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1/*
2 * kernel/lockdep.c
3 *
4 * Runtime locking correctness validator
5 *
6 * Started by Ingo Molnar:
7 *
8 * Copyright (C) 2006,2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
9 * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra
10 *
11 * this code maps all the lock dependencies as they occur in a live kernel
12 * and will warn about the following classes of locking bugs:
13 *
14 * - lock inversion scenarios
15 * - circular lock dependencies
16 * - hardirq/softirq safe/unsafe locking bugs
17 *
18 * Bugs are reported even if the current locking scenario does not cause
19 * any deadlock at this point.
20 *
21 * I.e. if anytime in the past two locks were taken in a different order,
22 * even if it happened for another task, even if those were different
23 * locks (but of the same class as this lock), this code will detect it.
24 *
25 * Thanks to Arjan van de Ven for coming up with the initial idea of
26 * mapping lock dependencies runtime.
27 */
28#define DISABLE_BRANCH_PROFILING
29#include <linux/mutex.h>
30#include <linux/sched.h>
31#include <linux/delay.h>
32#include <linux/module.h>
33#include <linux/proc_fs.h>
34#include <linux/seq_file.h>
35#include <linux/spinlock.h>
36#include <linux/kallsyms.h>
37#include <linux/interrupt.h>
38#include <linux/stacktrace.h>
39#include <linux/debug_locks.h>
40#include <linux/irqflags.h>
41#include <linux/utsname.h>
42#include <linux/hash.h>
43#include <linux/ftrace.h>
44#include <linux/stringify.h>
45#include <linux/bitops.h>
46#include <linux/gfp.h>
47#include <linux/kmemcheck.h>
48#include <linux/random.h>
49#include <linux/jhash.h>
50
51#include <asm/sections.h>
52
53#include "lockdep_internals.h"
54
55#define CREATE_TRACE_POINTS
56#include <trace/events/lock.h>
57
58#ifdef CONFIG_PROVE_LOCKING
59int prove_locking = 1;
60module_param(prove_locking, int, 0644);
61#else
62#define prove_locking 0
63#endif
64
65#ifdef CONFIG_LOCK_STAT
66int lock_stat = 1;
67module_param(lock_stat, int, 0644);
68#else
69#define lock_stat 0
70#endif
71
72/*
73 * lockdep_lock: protects the lockdep graph, the hashes and the
74 * class/list/hash allocators.
75 *
76 * This is one of the rare exceptions where it's justified
77 * to use a raw spinlock - we really dont want the spinlock
78 * code to recurse back into the lockdep code...
79 */
80static arch_spinlock_t lockdep_lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
81
82static int graph_lock(void)
83{
84 arch_spin_lock(&lockdep_lock);
85 /*
86 * Make sure that if another CPU detected a bug while
87 * walking the graph we dont change it (while the other
88 * CPU is busy printing out stuff with the graph lock
89 * dropped already)
90 */
91 if (!debug_locks) {
92 arch_spin_unlock(&lockdep_lock);
93 return 0;
94 }
95 /* prevent any recursions within lockdep from causing deadlocks */
96 current->lockdep_recursion++;
97 return 1;
98}
99
100static inline int graph_unlock(void)
101{
102 if (debug_locks && !arch_spin_is_locked(&lockdep_lock)) {
103 /*
104 * The lockdep graph lock isn't locked while we expect it to
105 * be, we're confused now, bye!
106 */
107 return DEBUG_LOCKS_WARN_ON(1);
108 }
109
110 current->lockdep_recursion--;
111 arch_spin_unlock(&lockdep_lock);
112 return 0;
113}
114
115/*
116 * Turn lock debugging off and return with 0 if it was off already,
117 * and also release the graph lock:
118 */
119static inline int debug_locks_off_graph_unlock(void)
120{
121 int ret = debug_locks_off();
122
123 arch_spin_unlock(&lockdep_lock);
124
125 return ret;
126}
127
128unsigned long nr_list_entries;
129static struct lock_list list_entries[MAX_LOCKDEP_ENTRIES];
130
131/*
132 * All data structures here are protected by the global debug_lock.
133 *
134 * Mutex key structs only get allocated, once during bootup, and never
135 * get freed - this significantly simplifies the debugging code.
136 */
137unsigned long nr_lock_classes;
138static struct lock_class lock_classes[MAX_LOCKDEP_KEYS];
139
140static inline struct lock_class *hlock_class(struct held_lock *hlock)
141{
142 if (!hlock->class_idx) {
143 /*
144 * Someone passed in garbage, we give up.
145 */
146 DEBUG_LOCKS_WARN_ON(1);
147 return NULL;
148 }
149 return lock_classes + hlock->class_idx - 1;
150}
151
152#ifdef CONFIG_LOCK_STAT
153static DEFINE_PER_CPU(struct lock_class_stats[MAX_LOCKDEP_KEYS], cpu_lock_stats);
154
155static inline u64 lockstat_clock(void)
156{
157 return local_clock();
158}
159
160static int lock_point(unsigned long points[], unsigned long ip)
161{
162 int i;
163
164 for (i = 0; i < LOCKSTAT_POINTS; i++) {
165 if (points[i] == 0) {
166 points[i] = ip;
167 break;
168 }
169 if (points[i] == ip)
170 break;
171 }
172
173 return i;
174}
175
176static void lock_time_inc(struct lock_time *lt, u64 time)
177{
178 if (time > lt->max)
179 lt->max = time;
180
181 if (time < lt->min || !lt->nr)
182 lt->min = time;
183
184 lt->total += time;
185 lt->nr++;
186}
187
188static inline void lock_time_add(struct lock_time *src, struct lock_time *dst)
189{
190 if (!src->nr)
191 return;
192
193 if (src->max > dst->max)
194 dst->max = src->max;
195
196 if (src->min < dst->min || !dst->nr)
197 dst->min = src->min;
198
199 dst->total += src->total;
200 dst->nr += src->nr;
201}
202
203struct lock_class_stats lock_stats(struct lock_class *class)
204{
205 struct lock_class_stats stats;
206 int cpu, i;
207
208 memset(&stats, 0, sizeof(struct lock_class_stats));
209 for_each_possible_cpu(cpu) {
210 struct lock_class_stats *pcs =
211 &per_cpu(cpu_lock_stats, cpu)[class - lock_classes];
212
213 for (i = 0; i < ARRAY_SIZE(stats.contention_point); i++)
214 stats.contention_point[i] += pcs->contention_point[i];
215
216 for (i = 0; i < ARRAY_SIZE(stats.contending_point); i++)
217 stats.contending_point[i] += pcs->contending_point[i];
218
219 lock_time_add(&pcs->read_waittime, &stats.read_waittime);
220 lock_time_add(&pcs->write_waittime, &stats.write_waittime);
221
222 lock_time_add(&pcs->read_holdtime, &stats.read_holdtime);
223 lock_time_add(&pcs->write_holdtime, &stats.write_holdtime);
224
225 for (i = 0; i < ARRAY_SIZE(stats.bounces); i++)
226 stats.bounces[i] += pcs->bounces[i];
227 }
228
229 return stats;
230}
231
232void clear_lock_stats(struct lock_class *class)
233{
234 int cpu;
235
236 for_each_possible_cpu(cpu) {
237 struct lock_class_stats *cpu_stats =
238 &per_cpu(cpu_lock_stats, cpu)[class - lock_classes];
239
240 memset(cpu_stats, 0, sizeof(struct lock_class_stats));
241 }
242 memset(class->contention_point, 0, sizeof(class->contention_point));
243 memset(class->contending_point, 0, sizeof(class->contending_point));
244}
245
246static struct lock_class_stats *get_lock_stats(struct lock_class *class)
247{
248 return &get_cpu_var(cpu_lock_stats)[class - lock_classes];
249}
250
251static void put_lock_stats(struct lock_class_stats *stats)
252{
253 put_cpu_var(cpu_lock_stats);
254}
255
256static void lock_release_holdtime(struct held_lock *hlock)
257{
258 struct lock_class_stats *stats;
259 u64 holdtime;
260
261 if (!lock_stat)
262 return;
263
264 holdtime = lockstat_clock() - hlock->holdtime_stamp;
265
266 stats = get_lock_stats(hlock_class(hlock));
267 if (hlock->read)
268 lock_time_inc(&stats->read_holdtime, holdtime);
269 else
270 lock_time_inc(&stats->write_holdtime, holdtime);
271 put_lock_stats(stats);
272}
273#else
274static inline void lock_release_holdtime(struct held_lock *hlock)
275{
276}
277#endif
278
279/*
280 * We keep a global list of all lock classes. The list only grows,
281 * never shrinks. The list is only accessed with the lockdep
282 * spinlock lock held.
283 */
284LIST_HEAD(all_lock_classes);
285
286/*
287 * The lockdep classes are in a hash-table as well, for fast lookup:
288 */
289#define CLASSHASH_BITS (MAX_LOCKDEP_KEYS_BITS - 1)
290#define CLASSHASH_SIZE (1UL << CLASSHASH_BITS)
291#define __classhashfn(key) hash_long((unsigned long)key, CLASSHASH_BITS)
292#define classhashentry(key) (classhash_table + __classhashfn((key)))
293
294static struct hlist_head classhash_table[CLASSHASH_SIZE];
295
296/*
297 * We put the lock dependency chains into a hash-table as well, to cache
298 * their existence:
299 */
300#define CHAINHASH_BITS (MAX_LOCKDEP_CHAINS_BITS-1)
301#define CHAINHASH_SIZE (1UL << CHAINHASH_BITS)
302#define __chainhashfn(chain) hash_long(chain, CHAINHASH_BITS)
303#define chainhashentry(chain) (chainhash_table + __chainhashfn((chain)))
304
305static struct hlist_head chainhash_table[CHAINHASH_SIZE];
306
307/*
308 * The hash key of the lock dependency chains is a hash itself too:
309 * it's a hash of all locks taken up to that lock, including that lock.
310 * It's a 64-bit hash, because it's important for the keys to be
311 * unique.
312 */
313static inline u64 iterate_chain_key(u64 key, u32 idx)
314{
315 u32 k0 = key, k1 = key >> 32;
316
317 __jhash_mix(idx, k0, k1); /* Macro that modifies arguments! */
318
319 return k0 | (u64)k1 << 32;
320}
321
322void lockdep_off(void)
323{
324 current->lockdep_recursion++;
325}
326EXPORT_SYMBOL(lockdep_off);
327
328void lockdep_on(void)
329{
330 current->lockdep_recursion--;
331}
332EXPORT_SYMBOL(lockdep_on);
333
334/*
335 * Debugging switches:
336 */
337
338#define VERBOSE 0
339#define VERY_VERBOSE 0
340
341#if VERBOSE
342# define HARDIRQ_VERBOSE 1
343# define SOFTIRQ_VERBOSE 1
344# define RECLAIM_VERBOSE 1
345#else
346# define HARDIRQ_VERBOSE 0
347# define SOFTIRQ_VERBOSE 0
348# define RECLAIM_VERBOSE 0
349#endif
350
351#if VERBOSE || HARDIRQ_VERBOSE || SOFTIRQ_VERBOSE || RECLAIM_VERBOSE
352/*
353 * Quick filtering for interesting events:
354 */
355static int class_filter(struct lock_class *class)
356{
357#if 0
358 /* Example */
359 if (class->name_version == 1 &&
360 !strcmp(class->name, "lockname"))
361 return 1;
362 if (class->name_version == 1 &&
363 !strcmp(class->name, "&struct->lockfield"))
364 return 1;
365#endif
366 /* Filter everything else. 1 would be to allow everything else */
367 return 0;
368}
369#endif
370
371static int verbose(struct lock_class *class)
372{
373#if VERBOSE
374 return class_filter(class);
375#endif
376 return 0;
377}
378
379/*
380 * Stack-trace: tightly packed array of stack backtrace
381 * addresses. Protected by the graph_lock.
382 */
383unsigned long nr_stack_trace_entries;
384static unsigned long stack_trace[MAX_STACK_TRACE_ENTRIES];
385
386static void print_lockdep_off(const char *bug_msg)
387{
388 printk(KERN_DEBUG "%s\n", bug_msg);
389 printk(KERN_DEBUG "turning off the locking correctness validator.\n");
390#ifdef CONFIG_LOCK_STAT
391 printk(KERN_DEBUG "Please attach the output of /proc/lock_stat to the bug report\n");
392#endif
393}
394
395static int save_trace(struct stack_trace *trace)
396{
397 trace->nr_entries = 0;
398 trace->max_entries = MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries;
399 trace->entries = stack_trace + nr_stack_trace_entries;
400
401 trace->skip = 3;
402
403 save_stack_trace(trace);
404
405 /*
406 * Some daft arches put -1 at the end to indicate its a full trace.
407 *
408 * <rant> this is buggy anyway, since it takes a whole extra entry so a
409 * complete trace that maxes out the entries provided will be reported
410 * as incomplete, friggin useless </rant>
411 */
412 if (trace->nr_entries != 0 &&
413 trace->entries[trace->nr_entries-1] == ULONG_MAX)
414 trace->nr_entries--;
415
416 trace->max_entries = trace->nr_entries;
417
418 nr_stack_trace_entries += trace->nr_entries;
419
420 if (nr_stack_trace_entries >= MAX_STACK_TRACE_ENTRIES-1) {
421 if (!debug_locks_off_graph_unlock())
422 return 0;
423
424 print_lockdep_off("BUG: MAX_STACK_TRACE_ENTRIES too low!");
425 dump_stack();
426
427 return 0;
428 }
429
430 return 1;
431}
432
433unsigned int nr_hardirq_chains;
434unsigned int nr_softirq_chains;
435unsigned int nr_process_chains;
436unsigned int max_lockdep_depth;
437
438#ifdef CONFIG_DEBUG_LOCKDEP
439/*
440 * Various lockdep statistics:
441 */
442DEFINE_PER_CPU(struct lockdep_stats, lockdep_stats);
443#endif
444
445/*
446 * Locking printouts:
447 */
448
449#define __USAGE(__STATE) \
450 [LOCK_USED_IN_##__STATE] = "IN-"__stringify(__STATE)"-W", \
451 [LOCK_ENABLED_##__STATE] = __stringify(__STATE)"-ON-W", \
452 [LOCK_USED_IN_##__STATE##_READ] = "IN-"__stringify(__STATE)"-R",\
453 [LOCK_ENABLED_##__STATE##_READ] = __stringify(__STATE)"-ON-R",
454
455static const char *usage_str[] =
456{
457#define LOCKDEP_STATE(__STATE) __USAGE(__STATE)
458#include "lockdep_states.h"
459#undef LOCKDEP_STATE
460 [LOCK_USED] = "INITIAL USE",
461};
462
463const char * __get_key_name(struct lockdep_subclass_key *key, char *str)
464{
465 return kallsyms_lookup((unsigned long)key, NULL, NULL, NULL, str);
466}
467
468static inline unsigned long lock_flag(enum lock_usage_bit bit)
469{
470 return 1UL << bit;
471}
472
473static char get_usage_char(struct lock_class *class, enum lock_usage_bit bit)
474{
475 char c = '.';
476
477 if (class->usage_mask & lock_flag(bit + 2))
478 c = '+';
479 if (class->usage_mask & lock_flag(bit)) {
480 c = '-';
481 if (class->usage_mask & lock_flag(bit + 2))
482 c = '?';
483 }
484
485 return c;
486}
487
488void get_usage_chars(struct lock_class *class, char usage[LOCK_USAGE_CHARS])
489{
490 int i = 0;
491
492#define LOCKDEP_STATE(__STATE) \
493 usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE); \
494 usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE##_READ);
495#include "lockdep_states.h"
496#undef LOCKDEP_STATE
497
498 usage[i] = '\0';
499}
500
501static void __print_lock_name(struct lock_class *class)
502{
503 char str[KSYM_NAME_LEN];
504 const char *name;
505
506 name = class->name;
507 if (!name) {
508 name = __get_key_name(class->key, str);
509 printk(KERN_CONT "%s", name);
510 } else {
511 printk(KERN_CONT "%s", name);
512 if (class->name_version > 1)
513 printk(KERN_CONT "#%d", class->name_version);
514 if (class->subclass)
515 printk(KERN_CONT "/%d", class->subclass);
516 }
517}
518
519static void print_lock_name(struct lock_class *class)
520{
521 char usage[LOCK_USAGE_CHARS];
522
523 get_usage_chars(class, usage);
524
525 printk(KERN_CONT " (");
526 __print_lock_name(class);
527 printk(KERN_CONT "){%s}", usage);
528}
529
530static void print_lockdep_cache(struct lockdep_map *lock)
531{
532 const char *name;
533 char str[KSYM_NAME_LEN];
534
535 name = lock->name;
536 if (!name)
537 name = __get_key_name(lock->key->subkeys, str);
538
539 printk(KERN_CONT "%s", name);
540}
541
542static void print_lock(struct held_lock *hlock)
543{
544 /*
545 * We can be called locklessly through debug_show_all_locks() so be
546 * extra careful, the hlock might have been released and cleared.
547 */
548 unsigned int class_idx = hlock->class_idx;
549
550 /* Don't re-read hlock->class_idx, can't use READ_ONCE() on bitfields: */
551 barrier();
552
553 if (!class_idx || (class_idx - 1) >= MAX_LOCKDEP_KEYS) {
554 printk(KERN_CONT "<RELEASED>\n");
555 return;
556 }
557
558 print_lock_name(lock_classes + class_idx - 1);
559 printk(KERN_CONT ", at: [<%p>] %pS\n",
560 (void *)hlock->acquire_ip, (void *)hlock->acquire_ip);
561}
562
563static void lockdep_print_held_locks(struct task_struct *curr)
564{
565 int i, depth = curr->lockdep_depth;
566
567 if (!depth) {
568 printk("no locks held by %s/%d.\n", curr->comm, task_pid_nr(curr));
569 return;
570 }
571 printk("%d lock%s held by %s/%d:\n",
572 depth, depth > 1 ? "s" : "", curr->comm, task_pid_nr(curr));
573
574 for (i = 0; i < depth; i++) {
575 printk(" #%d: ", i);
576 print_lock(curr->held_locks + i);
577 }
578}
579
580static void print_kernel_ident(void)
581{
582 printk("%s %.*s %s\n", init_utsname()->release,
583 (int)strcspn(init_utsname()->version, " "),
584 init_utsname()->version,
585 print_tainted());
586}
587
588static int very_verbose(struct lock_class *class)
589{
590#if VERY_VERBOSE
591 return class_filter(class);
592#endif
593 return 0;
594}
595
596/*
597 * Is this the address of a static object:
598 */
599#ifdef __KERNEL__
600static int static_obj(void *obj)
601{
602 unsigned long start = (unsigned long) &_stext,
603 end = (unsigned long) &_end,
604 addr = (unsigned long) obj;
605
606 /*
607 * static variable?
608 */
609 if ((addr >= start) && (addr < end))
610 return 1;
611
612 if (arch_is_kernel_data(addr))
613 return 1;
614
615 /*
616 * in-kernel percpu var?
617 */
618 if (is_kernel_percpu_address(addr))
619 return 1;
620
621 /*
622 * module static or percpu var?
623 */
624 return is_module_address(addr) || is_module_percpu_address(addr);
625}
626#endif
627
628/*
629 * To make lock name printouts unique, we calculate a unique
630 * class->name_version generation counter:
631 */
632static int count_matching_names(struct lock_class *new_class)
633{
634 struct lock_class *class;
635 int count = 0;
636
637 if (!new_class->name)
638 return 0;
639
640 list_for_each_entry_rcu(class, &all_lock_classes, lock_entry) {
641 if (new_class->key - new_class->subclass == class->key)
642 return class->name_version;
643 if (class->name && !strcmp(class->name, new_class->name))
644 count = max(count, class->name_version);
645 }
646
647 return count + 1;
648}
649
650/*
651 * Register a lock's class in the hash-table, if the class is not present
652 * yet. Otherwise we look it up. We cache the result in the lock object
653 * itself, so actual lookup of the hash should be once per lock object.
654 */
655static inline struct lock_class *
656look_up_lock_class(struct lockdep_map *lock, unsigned int subclass)
657{
658 struct lockdep_subclass_key *key;
659 struct hlist_head *hash_head;
660 struct lock_class *class;
661
662 if (unlikely(subclass >= MAX_LOCKDEP_SUBCLASSES)) {
663 debug_locks_off();
664 printk(KERN_ERR
665 "BUG: looking up invalid subclass: %u\n", subclass);
666 printk(KERN_ERR
667 "turning off the locking correctness validator.\n");
668 dump_stack();
669 return NULL;
670 }
671
672 /*
673 * Static locks do not have their class-keys yet - for them the key
674 * is the lock object itself:
675 */
676 if (unlikely(!lock->key))
677 lock->key = (void *)lock;
678
679 /*
680 * NOTE: the class-key must be unique. For dynamic locks, a static
681 * lock_class_key variable is passed in through the mutex_init()
682 * (or spin_lock_init()) call - which acts as the key. For static
683 * locks we use the lock object itself as the key.
684 */
685 BUILD_BUG_ON(sizeof(struct lock_class_key) >
686 sizeof(struct lockdep_map));
687
688 key = lock->key->subkeys + subclass;
689
690 hash_head = classhashentry(key);
691
692 /*
693 * We do an RCU walk of the hash, see lockdep_free_key_range().
694 */
695 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
696 return NULL;
697
698 hlist_for_each_entry_rcu(class, hash_head, hash_entry) {
699 if (class->key == key) {
700 /*
701 * Huh! same key, different name? Did someone trample
702 * on some memory? We're most confused.
703 */
704 WARN_ON_ONCE(class->name != lock->name);
705 return class;
706 }
707 }
708
709 return NULL;
710}
711
712/*
713 * Register a lock's class in the hash-table, if the class is not present
714 * yet. Otherwise we look it up. We cache the result in the lock object
715 * itself, so actual lookup of the hash should be once per lock object.
716 */
717static struct lock_class *
718register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force)
719{
720 struct lockdep_subclass_key *key;
721 struct hlist_head *hash_head;
722 struct lock_class *class;
723
724 DEBUG_LOCKS_WARN_ON(!irqs_disabled());
725
726 class = look_up_lock_class(lock, subclass);
727 if (likely(class))
728 goto out_set_class_cache;
729
730 /*
731 * Debug-check: all keys must be persistent!
732 */
733 if (!static_obj(lock->key)) {
734 debug_locks_off();
735 printk("INFO: trying to register non-static key.\n");
736 printk("the code is fine but needs lockdep annotation.\n");
737 printk("turning off the locking correctness validator.\n");
738 dump_stack();
739
740 return NULL;
741 }
742
743 key = lock->key->subkeys + subclass;
744 hash_head = classhashentry(key);
745
746 if (!graph_lock()) {
747 return NULL;
748 }
749 /*
750 * We have to do the hash-walk again, to avoid races
751 * with another CPU:
752 */
753 hlist_for_each_entry_rcu(class, hash_head, hash_entry) {
754 if (class->key == key)
755 goto out_unlock_set;
756 }
757
758 /*
759 * Allocate a new key from the static array, and add it to
760 * the hash:
761 */
762 if (nr_lock_classes >= MAX_LOCKDEP_KEYS) {
763 if (!debug_locks_off_graph_unlock()) {
764 return NULL;
765 }
766
767 print_lockdep_off("BUG: MAX_LOCKDEP_KEYS too low!");
768 dump_stack();
769 return NULL;
770 }
771 class = lock_classes + nr_lock_classes++;
772 debug_atomic_inc(nr_unused_locks);
773 class->key = key;
774 class->name = lock->name;
775 class->subclass = subclass;
776 INIT_LIST_HEAD(&class->lock_entry);
777 INIT_LIST_HEAD(&class->locks_before);
778 INIT_LIST_HEAD(&class->locks_after);
779 class->name_version = count_matching_names(class);
780 /*
781 * We use RCU's safe list-add method to make
782 * parallel walking of the hash-list safe:
783 */
784 hlist_add_head_rcu(&class->hash_entry, hash_head);
785 /*
786 * Add it to the global list of classes:
787 */
788 list_add_tail_rcu(&class->lock_entry, &all_lock_classes);
789
790 if (verbose(class)) {
791 graph_unlock();
792
793 printk("\nnew class %p: %s", class->key, class->name);
794 if (class->name_version > 1)
795 printk(KERN_CONT "#%d", class->name_version);
796 printk(KERN_CONT "\n");
797 dump_stack();
798
799 if (!graph_lock()) {
800 return NULL;
801 }
802 }
803out_unlock_set:
804 graph_unlock();
805
806out_set_class_cache:
807 if (!subclass || force)
808 lock->class_cache[0] = class;
809 else if (subclass < NR_LOCKDEP_CACHING_CLASSES)
810 lock->class_cache[subclass] = class;
811
812 /*
813 * Hash collision, did we smoke some? We found a class with a matching
814 * hash but the subclass -- which is hashed in -- didn't match.
815 */
816 if (DEBUG_LOCKS_WARN_ON(class->subclass != subclass))
817 return NULL;
818
819 return class;
820}
821
822#ifdef CONFIG_PROVE_LOCKING
823/*
824 * Allocate a lockdep entry. (assumes the graph_lock held, returns
825 * with NULL on failure)
826 */
827static struct lock_list *alloc_list_entry(void)
828{
829 if (nr_list_entries >= MAX_LOCKDEP_ENTRIES) {
830 if (!debug_locks_off_graph_unlock())
831 return NULL;
832
833 print_lockdep_off("BUG: MAX_LOCKDEP_ENTRIES too low!");
834 dump_stack();
835 return NULL;
836 }
837 return list_entries + nr_list_entries++;
838}
839
840/*
841 * Add a new dependency to the head of the list:
842 */
843static int add_lock_to_list(struct lock_class *this, struct list_head *head,
844 unsigned long ip, int distance,
845 struct stack_trace *trace)
846{
847 struct lock_list *entry;
848 /*
849 * Lock not present yet - get a new dependency struct and
850 * add it to the list:
851 */
852 entry = alloc_list_entry();
853 if (!entry)
854 return 0;
855
856 entry->class = this;
857 entry->distance = distance;
858 entry->trace = *trace;
859 /*
860 * Both allocation and removal are done under the graph lock; but
861 * iteration is under RCU-sched; see look_up_lock_class() and
862 * lockdep_free_key_range().
863 */
864 list_add_tail_rcu(&entry->entry, head);
865
866 return 1;
867}
868
869/*
870 * For good efficiency of modular, we use power of 2
871 */
872#define MAX_CIRCULAR_QUEUE_SIZE 4096UL
873#define CQ_MASK (MAX_CIRCULAR_QUEUE_SIZE-1)
874
875/*
876 * The circular_queue and helpers is used to implement the
877 * breadth-first search(BFS)algorithem, by which we can build
878 * the shortest path from the next lock to be acquired to the
879 * previous held lock if there is a circular between them.
880 */
881struct circular_queue {
882 unsigned long element[MAX_CIRCULAR_QUEUE_SIZE];
883 unsigned int front, rear;
884};
885
886static struct circular_queue lock_cq;
887
888unsigned int max_bfs_queue_depth;
889
890static unsigned int lockdep_dependency_gen_id;
891
892static inline void __cq_init(struct circular_queue *cq)
893{
894 cq->front = cq->rear = 0;
895 lockdep_dependency_gen_id++;
896}
897
898static inline int __cq_empty(struct circular_queue *cq)
899{
900 return (cq->front == cq->rear);
901}
902
903static inline int __cq_full(struct circular_queue *cq)
904{
905 return ((cq->rear + 1) & CQ_MASK) == cq->front;
906}
907
908static inline int __cq_enqueue(struct circular_queue *cq, unsigned long elem)
909{
910 if (__cq_full(cq))
911 return -1;
912
913 cq->element[cq->rear] = elem;
914 cq->rear = (cq->rear + 1) & CQ_MASK;
915 return 0;
916}
917
918static inline int __cq_dequeue(struct circular_queue *cq, unsigned long *elem)
919{
920 if (__cq_empty(cq))
921 return -1;
922
923 *elem = cq->element[cq->front];
924 cq->front = (cq->front + 1) & CQ_MASK;
925 return 0;
926}
927
928static inline unsigned int __cq_get_elem_count(struct circular_queue *cq)
929{
930 return (cq->rear - cq->front) & CQ_MASK;
931}
932
933static inline void mark_lock_accessed(struct lock_list *lock,
934 struct lock_list *parent)
935{
936 unsigned long nr;
937
938 nr = lock - list_entries;
939 WARN_ON(nr >= nr_list_entries); /* Out-of-bounds, input fail */
940 lock->parent = parent;
941 lock->class->dep_gen_id = lockdep_dependency_gen_id;
942}
943
944static inline unsigned long lock_accessed(struct lock_list *lock)
945{
946 unsigned long nr;
947
948 nr = lock - list_entries;
949 WARN_ON(nr >= nr_list_entries); /* Out-of-bounds, input fail */
950 return lock->class->dep_gen_id == lockdep_dependency_gen_id;
951}
952
953static inline struct lock_list *get_lock_parent(struct lock_list *child)
954{
955 return child->parent;
956}
957
958static inline int get_lock_depth(struct lock_list *child)
959{
960 int depth = 0;
961 struct lock_list *parent;
962
963 while ((parent = get_lock_parent(child))) {
964 child = parent;
965 depth++;
966 }
967 return depth;
968}
969
970static int __bfs(struct lock_list *source_entry,
971 void *data,
972 int (*match)(struct lock_list *entry, void *data),
973 struct lock_list **target_entry,
974 int forward)
975{
976 struct lock_list *entry;
977 struct list_head *head;
978 struct circular_queue *cq = &lock_cq;
979 int ret = 1;
980
981 if (match(source_entry, data)) {
982 *target_entry = source_entry;
983 ret = 0;
984 goto exit;
985 }
986
987 if (forward)
988 head = &source_entry->class->locks_after;
989 else
990 head = &source_entry->class->locks_before;
991
992 if (list_empty(head))
993 goto exit;
994
995 __cq_init(cq);
996 __cq_enqueue(cq, (unsigned long)source_entry);
997
998 while (!__cq_empty(cq)) {
999 struct lock_list *lock;
1000
1001 __cq_dequeue(cq, (unsigned long *)&lock);
1002
1003 if (!lock->class) {
1004 ret = -2;
1005 goto exit;
1006 }
1007
1008 if (forward)
1009 head = &lock->class->locks_after;
1010 else
1011 head = &lock->class->locks_before;
1012
1013 DEBUG_LOCKS_WARN_ON(!irqs_disabled());
1014
1015 list_for_each_entry_rcu(entry, head, entry) {
1016 if (!lock_accessed(entry)) {
1017 unsigned int cq_depth;
1018 mark_lock_accessed(entry, lock);
1019 if (match(entry, data)) {
1020 *target_entry = entry;
1021 ret = 0;
1022 goto exit;
1023 }
1024
1025 if (__cq_enqueue(cq, (unsigned long)entry)) {
1026 ret = -1;
1027 goto exit;
1028 }
1029 cq_depth = __cq_get_elem_count(cq);
1030 if (max_bfs_queue_depth < cq_depth)
1031 max_bfs_queue_depth = cq_depth;
1032 }
1033 }
1034 }
1035exit:
1036 return ret;
1037}
1038
1039static inline int __bfs_forwards(struct lock_list *src_entry,
1040 void *data,
1041 int (*match)(struct lock_list *entry, void *data),
1042 struct lock_list **target_entry)
1043{
1044 return __bfs(src_entry, data, match, target_entry, 1);
1045
1046}
1047
1048static inline int __bfs_backwards(struct lock_list *src_entry,
1049 void *data,
1050 int (*match)(struct lock_list *entry, void *data),
1051 struct lock_list **target_entry)
1052{
1053 return __bfs(src_entry, data, match, target_entry, 0);
1054
1055}
1056
1057/*
1058 * Recursive, forwards-direction lock-dependency checking, used for
1059 * both noncyclic checking and for hardirq-unsafe/softirq-unsafe
1060 * checking.
1061 */
1062
1063/*
1064 * Print a dependency chain entry (this is only done when a deadlock
1065 * has been detected):
1066 */
1067static noinline int
1068print_circular_bug_entry(struct lock_list *target, int depth)
1069{
1070 if (debug_locks_silent)
1071 return 0;
1072 printk("\n-> #%u", depth);
1073 print_lock_name(target->class);
1074 printk(KERN_CONT ":\n");
1075 print_stack_trace(&target->trace, 6);
1076
1077 return 0;
1078}
1079
1080static void
1081print_circular_lock_scenario(struct held_lock *src,
1082 struct held_lock *tgt,
1083 struct lock_list *prt)
1084{
1085 struct lock_class *source = hlock_class(src);
1086 struct lock_class *target = hlock_class(tgt);
1087 struct lock_class *parent = prt->class;
1088
1089 /*
1090 * A direct locking problem where unsafe_class lock is taken
1091 * directly by safe_class lock, then all we need to show
1092 * is the deadlock scenario, as it is obvious that the
1093 * unsafe lock is taken under the safe lock.
1094 *
1095 * But if there is a chain instead, where the safe lock takes
1096 * an intermediate lock (middle_class) where this lock is
1097 * not the same as the safe lock, then the lock chain is
1098 * used to describe the problem. Otherwise we would need
1099 * to show a different CPU case for each link in the chain
1100 * from the safe_class lock to the unsafe_class lock.
1101 */
1102 if (parent != source) {
1103 printk("Chain exists of:\n ");
1104 __print_lock_name(source);
1105 printk(KERN_CONT " --> ");
1106 __print_lock_name(parent);
1107 printk(KERN_CONT " --> ");
1108 __print_lock_name(target);
1109 printk(KERN_CONT "\n\n");
1110 }
1111
1112 printk(" Possible unsafe locking scenario:\n\n");
1113 printk(" CPU0 CPU1\n");
1114 printk(" ---- ----\n");
1115 printk(" lock(");
1116 __print_lock_name(target);
1117 printk(KERN_CONT ");\n");
1118 printk(" lock(");
1119 __print_lock_name(parent);
1120 printk(KERN_CONT ");\n");
1121 printk(" lock(");
1122 __print_lock_name(target);
1123 printk(KERN_CONT ");\n");
1124 printk(" lock(");
1125 __print_lock_name(source);
1126 printk(KERN_CONT ");\n");
1127 printk("\n *** DEADLOCK ***\n\n");
1128}
1129
1130/*
1131 * When a circular dependency is detected, print the
1132 * header first:
1133 */
1134static noinline int
1135print_circular_bug_header(struct lock_list *entry, unsigned int depth,
1136 struct held_lock *check_src,
1137 struct held_lock *check_tgt)
1138{
1139 struct task_struct *curr = current;
1140
1141 if (debug_locks_silent)
1142 return 0;
1143
1144 printk("\n");
1145 printk("======================================================\n");
1146 printk("[ INFO: possible circular locking dependency detected ]\n");
1147 print_kernel_ident();
1148 printk("-------------------------------------------------------\n");
1149 printk("%s/%d is trying to acquire lock:\n",
1150 curr->comm, task_pid_nr(curr));
1151 print_lock(check_src);
1152 printk("\nbut task is already holding lock:\n");
1153 print_lock(check_tgt);
1154 printk("\nwhich lock already depends on the new lock.\n\n");
1155 printk("\nthe existing dependency chain (in reverse order) is:\n");
1156
1157 print_circular_bug_entry(entry, depth);
1158
1159 return 0;
1160}
1161
1162static inline int class_equal(struct lock_list *entry, void *data)
1163{
1164 return entry->class == data;
1165}
1166
1167static noinline int print_circular_bug(struct lock_list *this,
1168 struct lock_list *target,
1169 struct held_lock *check_src,
1170 struct held_lock *check_tgt)
1171{
1172 struct task_struct *curr = current;
1173 struct lock_list *parent;
1174 struct lock_list *first_parent;
1175 int depth;
1176
1177 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1178 return 0;
1179
1180 if (!save_trace(&this->trace))
1181 return 0;
1182
1183 depth = get_lock_depth(target);
1184
1185 print_circular_bug_header(target, depth, check_src, check_tgt);
1186
1187 parent = get_lock_parent(target);
1188 first_parent = parent;
1189
1190 while (parent) {
1191 print_circular_bug_entry(parent, --depth);
1192 parent = get_lock_parent(parent);
1193 }
1194
1195 printk("\nother info that might help us debug this:\n\n");
1196 print_circular_lock_scenario(check_src, check_tgt,
1197 first_parent);
1198
1199 lockdep_print_held_locks(curr);
1200
1201 printk("\nstack backtrace:\n");
1202 dump_stack();
1203
1204 return 0;
1205}
1206
1207static noinline int print_bfs_bug(int ret)
1208{
1209 if (!debug_locks_off_graph_unlock())
1210 return 0;
1211
1212 /*
1213 * Breadth-first-search failed, graph got corrupted?
1214 */
1215 WARN(1, "lockdep bfs error:%d\n", ret);
1216
1217 return 0;
1218}
1219
1220static int noop_count(struct lock_list *entry, void *data)
1221{
1222 (*(unsigned long *)data)++;
1223 return 0;
1224}
1225
1226static unsigned long __lockdep_count_forward_deps(struct lock_list *this)
1227{
1228 unsigned long count = 0;
1229 struct lock_list *uninitialized_var(target_entry);
1230
1231 __bfs_forwards(this, (void *)&count, noop_count, &target_entry);
1232
1233 return count;
1234}
1235unsigned long lockdep_count_forward_deps(struct lock_class *class)
1236{
1237 unsigned long ret, flags;
1238 struct lock_list this;
1239
1240 this.parent = NULL;
1241 this.class = class;
1242
1243 local_irq_save(flags);
1244 arch_spin_lock(&lockdep_lock);
1245 ret = __lockdep_count_forward_deps(&this);
1246 arch_spin_unlock(&lockdep_lock);
1247 local_irq_restore(flags);
1248
1249 return ret;
1250}
1251
1252static unsigned long __lockdep_count_backward_deps(struct lock_list *this)
1253{
1254 unsigned long count = 0;
1255 struct lock_list *uninitialized_var(target_entry);
1256
1257 __bfs_backwards(this, (void *)&count, noop_count, &target_entry);
1258
1259 return count;
1260}
1261
1262unsigned long lockdep_count_backward_deps(struct lock_class *class)
1263{
1264 unsigned long ret, flags;
1265 struct lock_list this;
1266
1267 this.parent = NULL;
1268 this.class = class;
1269
1270 local_irq_save(flags);
1271 arch_spin_lock(&lockdep_lock);
1272 ret = __lockdep_count_backward_deps(&this);
1273 arch_spin_unlock(&lockdep_lock);
1274 local_irq_restore(flags);
1275
1276 return ret;
1277}
1278
1279/*
1280 * Prove that the dependency graph starting at <entry> can not
1281 * lead to <target>. Print an error and return 0 if it does.
1282 */
1283static noinline int
1284check_noncircular(struct lock_list *root, struct lock_class *target,
1285 struct lock_list **target_entry)
1286{
1287 int result;
1288
1289 debug_atomic_inc(nr_cyclic_checks);
1290
1291 result = __bfs_forwards(root, target, class_equal, target_entry);
1292
1293 return result;
1294}
1295
1296#if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
1297/*
1298 * Forwards and backwards subgraph searching, for the purposes of
1299 * proving that two subgraphs can be connected by a new dependency
1300 * without creating any illegal irq-safe -> irq-unsafe lock dependency.
1301 */
1302
1303static inline int usage_match(struct lock_list *entry, void *bit)
1304{
1305 return entry->class->usage_mask & (1 << (enum lock_usage_bit)bit);
1306}
1307
1308
1309
1310/*
1311 * Find a node in the forwards-direction dependency sub-graph starting
1312 * at @root->class that matches @bit.
1313 *
1314 * Return 0 if such a node exists in the subgraph, and put that node
1315 * into *@target_entry.
1316 *
1317 * Return 1 otherwise and keep *@target_entry unchanged.
1318 * Return <0 on error.
1319 */
1320static int
1321find_usage_forwards(struct lock_list *root, enum lock_usage_bit bit,
1322 struct lock_list **target_entry)
1323{
1324 int result;
1325
1326 debug_atomic_inc(nr_find_usage_forwards_checks);
1327
1328 result = __bfs_forwards(root, (void *)bit, usage_match, target_entry);
1329
1330 return result;
1331}
1332
1333/*
1334 * Find a node in the backwards-direction dependency sub-graph starting
1335 * at @root->class that matches @bit.
1336 *
1337 * Return 0 if such a node exists in the subgraph, and put that node
1338 * into *@target_entry.
1339 *
1340 * Return 1 otherwise and keep *@target_entry unchanged.
1341 * Return <0 on error.
1342 */
1343static int
1344find_usage_backwards(struct lock_list *root, enum lock_usage_bit bit,
1345 struct lock_list **target_entry)
1346{
1347 int result;
1348
1349 debug_atomic_inc(nr_find_usage_backwards_checks);
1350
1351 result = __bfs_backwards(root, (void *)bit, usage_match, target_entry);
1352
1353 return result;
1354}
1355
1356static void print_lock_class_header(struct lock_class *class, int depth)
1357{
1358 int bit;
1359
1360 printk("%*s->", depth, "");
1361 print_lock_name(class);
1362 printk(KERN_CONT " ops: %lu", class->ops);
1363 printk(KERN_CONT " {\n");
1364
1365 for (bit = 0; bit < LOCK_USAGE_STATES; bit++) {
1366 if (class->usage_mask & (1 << bit)) {
1367 int len = depth;
1368
1369 len += printk("%*s %s", depth, "", usage_str[bit]);
1370 len += printk(KERN_CONT " at:\n");
1371 print_stack_trace(class->usage_traces + bit, len);
1372 }
1373 }
1374 printk("%*s }\n", depth, "");
1375
1376 printk("%*s ... key at: [<%p>] %pS\n",
1377 depth, "", class->key, class->key);
1378}
1379
1380/*
1381 * printk the shortest lock dependencies from @start to @end in reverse order:
1382 */
1383static void __used
1384print_shortest_lock_dependencies(struct lock_list *leaf,
1385 struct lock_list *root)
1386{
1387 struct lock_list *entry = leaf;
1388 int depth;
1389
1390 /*compute depth from generated tree by BFS*/
1391 depth = get_lock_depth(leaf);
1392
1393 do {
1394 print_lock_class_header(entry->class, depth);
1395 printk("%*s ... acquired at:\n", depth, "");
1396 print_stack_trace(&entry->trace, 2);
1397 printk("\n");
1398
1399 if (depth == 0 && (entry != root)) {
1400 printk("lockdep:%s bad path found in chain graph\n", __func__);
1401 break;
1402 }
1403
1404 entry = get_lock_parent(entry);
1405 depth--;
1406 } while (entry && (depth >= 0));
1407
1408 return;
1409}
1410
1411static void
1412print_irq_lock_scenario(struct lock_list *safe_entry,
1413 struct lock_list *unsafe_entry,
1414 struct lock_class *prev_class,
1415 struct lock_class *next_class)
1416{
1417 struct lock_class *safe_class = safe_entry->class;
1418 struct lock_class *unsafe_class = unsafe_entry->class;
1419 struct lock_class *middle_class = prev_class;
1420
1421 if (middle_class == safe_class)
1422 middle_class = next_class;
1423
1424 /*
1425 * A direct locking problem where unsafe_class lock is taken
1426 * directly by safe_class lock, then all we need to show
1427 * is the deadlock scenario, as it is obvious that the
1428 * unsafe lock is taken under the safe lock.
1429 *
1430 * But if there is a chain instead, where the safe lock takes
1431 * an intermediate lock (middle_class) where this lock is
1432 * not the same as the safe lock, then the lock chain is
1433 * used to describe the problem. Otherwise we would need
1434 * to show a different CPU case for each link in the chain
1435 * from the safe_class lock to the unsafe_class lock.
1436 */
1437 if (middle_class != unsafe_class) {
1438 printk("Chain exists of:\n ");
1439 __print_lock_name(safe_class);
1440 printk(KERN_CONT " --> ");
1441 __print_lock_name(middle_class);
1442 printk(KERN_CONT " --> ");
1443 __print_lock_name(unsafe_class);
1444 printk(KERN_CONT "\n\n");
1445 }
1446
1447 printk(" Possible interrupt unsafe locking scenario:\n\n");
1448 printk(" CPU0 CPU1\n");
1449 printk(" ---- ----\n");
1450 printk(" lock(");
1451 __print_lock_name(unsafe_class);
1452 printk(KERN_CONT ");\n");
1453 printk(" local_irq_disable();\n");
1454 printk(" lock(");
1455 __print_lock_name(safe_class);
1456 printk(KERN_CONT ");\n");
1457 printk(" lock(");
1458 __print_lock_name(middle_class);
1459 printk(KERN_CONT ");\n");
1460 printk(" <Interrupt>\n");
1461 printk(" lock(");
1462 __print_lock_name(safe_class);
1463 printk(KERN_CONT ");\n");
1464 printk("\n *** DEADLOCK ***\n\n");
1465}
1466
1467static int
1468print_bad_irq_dependency(struct task_struct *curr,
1469 struct lock_list *prev_root,
1470 struct lock_list *next_root,
1471 struct lock_list *backwards_entry,
1472 struct lock_list *forwards_entry,
1473 struct held_lock *prev,
1474 struct held_lock *next,
1475 enum lock_usage_bit bit1,
1476 enum lock_usage_bit bit2,
1477 const char *irqclass)
1478{
1479 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1480 return 0;
1481
1482 printk("\n");
1483 printk("======================================================\n");
1484 printk("[ INFO: %s-safe -> %s-unsafe lock order detected ]\n",
1485 irqclass, irqclass);
1486 print_kernel_ident();
1487 printk("------------------------------------------------------\n");
1488 printk("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] is trying to acquire:\n",
1489 curr->comm, task_pid_nr(curr),
1490 curr->hardirq_context, hardirq_count() >> HARDIRQ_SHIFT,
1491 curr->softirq_context, softirq_count() >> SOFTIRQ_SHIFT,
1492 curr->hardirqs_enabled,
1493 curr->softirqs_enabled);
1494 print_lock(next);
1495
1496 printk("\nand this task is already holding:\n");
1497 print_lock(prev);
1498 printk("which would create a new lock dependency:\n");
1499 print_lock_name(hlock_class(prev));
1500 printk(KERN_CONT " ->");
1501 print_lock_name(hlock_class(next));
1502 printk(KERN_CONT "\n");
1503
1504 printk("\nbut this new dependency connects a %s-irq-safe lock:\n",
1505 irqclass);
1506 print_lock_name(backwards_entry->class);
1507 printk("\n... which became %s-irq-safe at:\n", irqclass);
1508
1509 print_stack_trace(backwards_entry->class->usage_traces + bit1, 1);
1510
1511 printk("\nto a %s-irq-unsafe lock:\n", irqclass);
1512 print_lock_name(forwards_entry->class);
1513 printk("\n... which became %s-irq-unsafe at:\n", irqclass);
1514 printk("...");
1515
1516 print_stack_trace(forwards_entry->class->usage_traces + bit2, 1);
1517
1518 printk("\nother info that might help us debug this:\n\n");
1519 print_irq_lock_scenario(backwards_entry, forwards_entry,
1520 hlock_class(prev), hlock_class(next));
1521
1522 lockdep_print_held_locks(curr);
1523
1524 printk("\nthe dependencies between %s-irq-safe lock and the holding lock:\n", irqclass);
1525 if (!save_trace(&prev_root->trace))
1526 return 0;
1527 print_shortest_lock_dependencies(backwards_entry, prev_root);
1528
1529 printk("\nthe dependencies between the lock to be acquired");
1530 printk(" and %s-irq-unsafe lock:\n", irqclass);
1531 if (!save_trace(&next_root->trace))
1532 return 0;
1533 print_shortest_lock_dependencies(forwards_entry, next_root);
1534
1535 printk("\nstack backtrace:\n");
1536 dump_stack();
1537
1538 return 0;
1539}
1540
1541static int
1542check_usage(struct task_struct *curr, struct held_lock *prev,
1543 struct held_lock *next, enum lock_usage_bit bit_backwards,
1544 enum lock_usage_bit bit_forwards, const char *irqclass)
1545{
1546 int ret;
1547 struct lock_list this, that;
1548 struct lock_list *uninitialized_var(target_entry);
1549 struct lock_list *uninitialized_var(target_entry1);
1550
1551 this.parent = NULL;
1552
1553 this.class = hlock_class(prev);
1554 ret = find_usage_backwards(&this, bit_backwards, &target_entry);
1555 if (ret < 0)
1556 return print_bfs_bug(ret);
1557 if (ret == 1)
1558 return ret;
1559
1560 that.parent = NULL;
1561 that.class = hlock_class(next);
1562 ret = find_usage_forwards(&that, bit_forwards, &target_entry1);
1563 if (ret < 0)
1564 return print_bfs_bug(ret);
1565 if (ret == 1)
1566 return ret;
1567
1568 return print_bad_irq_dependency(curr, &this, &that,
1569 target_entry, target_entry1,
1570 prev, next,
1571 bit_backwards, bit_forwards, irqclass);
1572}
1573
1574static const char *state_names[] = {
1575#define LOCKDEP_STATE(__STATE) \
1576 __stringify(__STATE),
1577#include "lockdep_states.h"
1578#undef LOCKDEP_STATE
1579};
1580
1581static const char *state_rnames[] = {
1582#define LOCKDEP_STATE(__STATE) \
1583 __stringify(__STATE)"-READ",
1584#include "lockdep_states.h"
1585#undef LOCKDEP_STATE
1586};
1587
1588static inline const char *state_name(enum lock_usage_bit bit)
1589{
1590 return (bit & 1) ? state_rnames[bit >> 2] : state_names[bit >> 2];
1591}
1592
1593static int exclusive_bit(int new_bit)
1594{
1595 /*
1596 * USED_IN
1597 * USED_IN_READ
1598 * ENABLED
1599 * ENABLED_READ
1600 *
1601 * bit 0 - write/read
1602 * bit 1 - used_in/enabled
1603 * bit 2+ state
1604 */
1605
1606 int state = new_bit & ~3;
1607 int dir = new_bit & 2;
1608
1609 /*
1610 * keep state, bit flip the direction and strip read.
1611 */
1612 return state | (dir ^ 2);
1613}
1614
1615static int check_irq_usage(struct task_struct *curr, struct held_lock *prev,
1616 struct held_lock *next, enum lock_usage_bit bit)
1617{
1618 /*
1619 * Prove that the new dependency does not connect a hardirq-safe
1620 * lock with a hardirq-unsafe lock - to achieve this we search
1621 * the backwards-subgraph starting at <prev>, and the
1622 * forwards-subgraph starting at <next>:
1623 */
1624 if (!check_usage(curr, prev, next, bit,
1625 exclusive_bit(bit), state_name(bit)))
1626 return 0;
1627
1628 bit++; /* _READ */
1629
1630 /*
1631 * Prove that the new dependency does not connect a hardirq-safe-read
1632 * lock with a hardirq-unsafe lock - to achieve this we search
1633 * the backwards-subgraph starting at <prev>, and the
1634 * forwards-subgraph starting at <next>:
1635 */
1636 if (!check_usage(curr, prev, next, bit,
1637 exclusive_bit(bit), state_name(bit)))
1638 return 0;
1639
1640 return 1;
1641}
1642
1643static int
1644check_prev_add_irq(struct task_struct *curr, struct held_lock *prev,
1645 struct held_lock *next)
1646{
1647#define LOCKDEP_STATE(__STATE) \
1648 if (!check_irq_usage(curr, prev, next, LOCK_USED_IN_##__STATE)) \
1649 return 0;
1650#include "lockdep_states.h"
1651#undef LOCKDEP_STATE
1652
1653 return 1;
1654}
1655
1656static void inc_chains(void)
1657{
1658 if (current->hardirq_context)
1659 nr_hardirq_chains++;
1660 else {
1661 if (current->softirq_context)
1662 nr_softirq_chains++;
1663 else
1664 nr_process_chains++;
1665 }
1666}
1667
1668#else
1669
1670static inline int
1671check_prev_add_irq(struct task_struct *curr, struct held_lock *prev,
1672 struct held_lock *next)
1673{
1674 return 1;
1675}
1676
1677static inline void inc_chains(void)
1678{
1679 nr_process_chains++;
1680}
1681
1682#endif
1683
1684static void
1685print_deadlock_scenario(struct held_lock *nxt,
1686 struct held_lock *prv)
1687{
1688 struct lock_class *next = hlock_class(nxt);
1689 struct lock_class *prev = hlock_class(prv);
1690
1691 printk(" Possible unsafe locking scenario:\n\n");
1692 printk(" CPU0\n");
1693 printk(" ----\n");
1694 printk(" lock(");
1695 __print_lock_name(prev);
1696 printk(KERN_CONT ");\n");
1697 printk(" lock(");
1698 __print_lock_name(next);
1699 printk(KERN_CONT ");\n");
1700 printk("\n *** DEADLOCK ***\n\n");
1701 printk(" May be due to missing lock nesting notation\n\n");
1702}
1703
1704static int
1705print_deadlock_bug(struct task_struct *curr, struct held_lock *prev,
1706 struct held_lock *next)
1707{
1708 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1709 return 0;
1710
1711 printk("\n");
1712 printk("=============================================\n");
1713 printk("[ INFO: possible recursive locking detected ]\n");
1714 print_kernel_ident();
1715 printk("---------------------------------------------\n");
1716 printk("%s/%d is trying to acquire lock:\n",
1717 curr->comm, task_pid_nr(curr));
1718 print_lock(next);
1719 printk("\nbut task is already holding lock:\n");
1720 print_lock(prev);
1721
1722 printk("\nother info that might help us debug this:\n");
1723 print_deadlock_scenario(next, prev);
1724 lockdep_print_held_locks(curr);
1725
1726 printk("\nstack backtrace:\n");
1727 dump_stack();
1728
1729 return 0;
1730}
1731
1732/*
1733 * Check whether we are holding such a class already.
1734 *
1735 * (Note that this has to be done separately, because the graph cannot
1736 * detect such classes of deadlocks.)
1737 *
1738 * Returns: 0 on deadlock detected, 1 on OK, 2 on recursive read
1739 */
1740static int
1741check_deadlock(struct task_struct *curr, struct held_lock *next,
1742 struct lockdep_map *next_instance, int read)
1743{
1744 struct held_lock *prev;
1745 struct held_lock *nest = NULL;
1746 int i;
1747
1748 for (i = 0; i < curr->lockdep_depth; i++) {
1749 prev = curr->held_locks + i;
1750
1751 if (prev->instance == next->nest_lock)
1752 nest = prev;
1753
1754 if (hlock_class(prev) != hlock_class(next))
1755 continue;
1756
1757 /*
1758 * Allow read-after-read recursion of the same
1759 * lock class (i.e. read_lock(lock)+read_lock(lock)):
1760 */
1761 if ((read == 2) && prev->read)
1762 return 2;
1763
1764 /*
1765 * We're holding the nest_lock, which serializes this lock's
1766 * nesting behaviour.
1767 */
1768 if (nest)
1769 return 2;
1770
1771 return print_deadlock_bug(curr, prev, next);
1772 }
1773 return 1;
1774}
1775
1776/*
1777 * There was a chain-cache miss, and we are about to add a new dependency
1778 * to a previous lock. We recursively validate the following rules:
1779 *
1780 * - would the adding of the <prev> -> <next> dependency create a
1781 * circular dependency in the graph? [== circular deadlock]
1782 *
1783 * - does the new prev->next dependency connect any hardirq-safe lock
1784 * (in the full backwards-subgraph starting at <prev>) with any
1785 * hardirq-unsafe lock (in the full forwards-subgraph starting at
1786 * <next>)? [== illegal lock inversion with hardirq contexts]
1787 *
1788 * - does the new prev->next dependency connect any softirq-safe lock
1789 * (in the full backwards-subgraph starting at <prev>) with any
1790 * softirq-unsafe lock (in the full forwards-subgraph starting at
1791 * <next>)? [== illegal lock inversion with softirq contexts]
1792 *
1793 * any of these scenarios could lead to a deadlock.
1794 *
1795 * Then if all the validations pass, we add the forwards and backwards
1796 * dependency.
1797 */
1798static int
1799check_prev_add(struct task_struct *curr, struct held_lock *prev,
1800 struct held_lock *next, int distance, int *stack_saved)
1801{
1802 struct lock_list *entry;
1803 int ret;
1804 struct lock_list this;
1805 struct lock_list *uninitialized_var(target_entry);
1806 /*
1807 * Static variable, serialized by the graph_lock().
1808 *
1809 * We use this static variable to save the stack trace in case
1810 * we call into this function multiple times due to encountering
1811 * trylocks in the held lock stack.
1812 */
1813 static struct stack_trace trace;
1814
1815 /*
1816 * Prove that the new <prev> -> <next> dependency would not
1817 * create a circular dependency in the graph. (We do this by
1818 * forward-recursing into the graph starting at <next>, and
1819 * checking whether we can reach <prev>.)
1820 *
1821 * We are using global variables to control the recursion, to
1822 * keep the stackframe size of the recursive functions low:
1823 */
1824 this.class = hlock_class(next);
1825 this.parent = NULL;
1826 ret = check_noncircular(&this, hlock_class(prev), &target_entry);
1827 if (unlikely(!ret))
1828 return print_circular_bug(&this, target_entry, next, prev);
1829 else if (unlikely(ret < 0))
1830 return print_bfs_bug(ret);
1831
1832 if (!check_prev_add_irq(curr, prev, next))
1833 return 0;
1834
1835 /*
1836 * For recursive read-locks we do all the dependency checks,
1837 * but we dont store read-triggered dependencies (only
1838 * write-triggered dependencies). This ensures that only the
1839 * write-side dependencies matter, and that if for example a
1840 * write-lock never takes any other locks, then the reads are
1841 * equivalent to a NOP.
1842 */
1843 if (next->read == 2 || prev->read == 2)
1844 return 1;
1845 /*
1846 * Is the <prev> -> <next> dependency already present?
1847 *
1848 * (this may occur even though this is a new chain: consider
1849 * e.g. the L1 -> L2 -> L3 -> L4 and the L5 -> L1 -> L2 -> L3
1850 * chains - the second one will be new, but L1 already has
1851 * L2 added to its dependency list, due to the first chain.)
1852 */
1853 list_for_each_entry(entry, &hlock_class(prev)->locks_after, entry) {
1854 if (entry->class == hlock_class(next)) {
1855 if (distance == 1)
1856 entry->distance = 1;
1857 return 2;
1858 }
1859 }
1860
1861 if (!*stack_saved) {
1862 if (!save_trace(&trace))
1863 return 0;
1864 *stack_saved = 1;
1865 }
1866
1867 /*
1868 * Ok, all validations passed, add the new lock
1869 * to the previous lock's dependency list:
1870 */
1871 ret = add_lock_to_list(hlock_class(next),
1872 &hlock_class(prev)->locks_after,
1873 next->acquire_ip, distance, &trace);
1874
1875 if (!ret)
1876 return 0;
1877
1878 ret = add_lock_to_list(hlock_class(prev),
1879 &hlock_class(next)->locks_before,
1880 next->acquire_ip, distance, &trace);
1881 if (!ret)
1882 return 0;
1883
1884 /*
1885 * Debugging printouts:
1886 */
1887 if (verbose(hlock_class(prev)) || verbose(hlock_class(next))) {
1888 /* We drop graph lock, so another thread can overwrite trace. */
1889 *stack_saved = 0;
1890 graph_unlock();
1891 printk("\n new dependency: ");
1892 print_lock_name(hlock_class(prev));
1893 printk(KERN_CONT " => ");
1894 print_lock_name(hlock_class(next));
1895 printk(KERN_CONT "\n");
1896 dump_stack();
1897 return graph_lock();
1898 }
1899 return 1;
1900}
1901
1902/*
1903 * Add the dependency to all directly-previous locks that are 'relevant'.
1904 * The ones that are relevant are (in increasing distance from curr):
1905 * all consecutive trylock entries and the final non-trylock entry - or
1906 * the end of this context's lock-chain - whichever comes first.
1907 */
1908static int
1909check_prevs_add(struct task_struct *curr, struct held_lock *next)
1910{
1911 int depth = curr->lockdep_depth;
1912 int stack_saved = 0;
1913 struct held_lock *hlock;
1914
1915 /*
1916 * Debugging checks.
1917 *
1918 * Depth must not be zero for a non-head lock:
1919 */
1920 if (!depth)
1921 goto out_bug;
1922 /*
1923 * At least two relevant locks must exist for this
1924 * to be a head:
1925 */
1926 if (curr->held_locks[depth].irq_context !=
1927 curr->held_locks[depth-1].irq_context)
1928 goto out_bug;
1929
1930 for (;;) {
1931 int distance = curr->lockdep_depth - depth + 1;
1932 hlock = curr->held_locks + depth - 1;
1933 /*
1934 * Only non-recursive-read entries get new dependencies
1935 * added:
1936 */
1937 if (hlock->read != 2 && hlock->check) {
1938 if (!check_prev_add(curr, hlock, next,
1939 distance, &stack_saved))
1940 return 0;
1941 /*
1942 * Stop after the first non-trylock entry,
1943 * as non-trylock entries have added their
1944 * own direct dependencies already, so this
1945 * lock is connected to them indirectly:
1946 */
1947 if (!hlock->trylock)
1948 break;
1949 }
1950 depth--;
1951 /*
1952 * End of lock-stack?
1953 */
1954 if (!depth)
1955 break;
1956 /*
1957 * Stop the search if we cross into another context:
1958 */
1959 if (curr->held_locks[depth].irq_context !=
1960 curr->held_locks[depth-1].irq_context)
1961 break;
1962 }
1963 return 1;
1964out_bug:
1965 if (!debug_locks_off_graph_unlock())
1966 return 0;
1967
1968 /*
1969 * Clearly we all shouldn't be here, but since we made it we
1970 * can reliable say we messed up our state. See the above two
1971 * gotos for reasons why we could possibly end up here.
1972 */
1973 WARN_ON(1);
1974
1975 return 0;
1976}
1977
1978unsigned long nr_lock_chains;
1979struct lock_chain lock_chains[MAX_LOCKDEP_CHAINS];
1980int nr_chain_hlocks;
1981static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
1982
1983struct lock_class *lock_chain_get_class(struct lock_chain *chain, int i)
1984{
1985 return lock_classes + chain_hlocks[chain->base + i];
1986}
1987
1988/*
1989 * Returns the index of the first held_lock of the current chain
1990 */
1991static inline int get_first_held_lock(struct task_struct *curr,
1992 struct held_lock *hlock)
1993{
1994 int i;
1995 struct held_lock *hlock_curr;
1996
1997 for (i = curr->lockdep_depth - 1; i >= 0; i--) {
1998 hlock_curr = curr->held_locks + i;
1999 if (hlock_curr->irq_context != hlock->irq_context)
2000 break;
2001
2002 }
2003
2004 return ++i;
2005}
2006
2007#ifdef CONFIG_DEBUG_LOCKDEP
2008/*
2009 * Returns the next chain_key iteration
2010 */
2011static u64 print_chain_key_iteration(int class_idx, u64 chain_key)
2012{
2013 u64 new_chain_key = iterate_chain_key(chain_key, class_idx);
2014
2015 printk(" class_idx:%d -> chain_key:%016Lx",
2016 class_idx,
2017 (unsigned long long)new_chain_key);
2018 return new_chain_key;
2019}
2020
2021static void
2022print_chain_keys_held_locks(struct task_struct *curr, struct held_lock *hlock_next)
2023{
2024 struct held_lock *hlock;
2025 u64 chain_key = 0;
2026 int depth = curr->lockdep_depth;
2027 int i;
2028
2029 printk("depth: %u\n", depth + 1);
2030 for (i = get_first_held_lock(curr, hlock_next); i < depth; i++) {
2031 hlock = curr->held_locks + i;
2032 chain_key = print_chain_key_iteration(hlock->class_idx, chain_key);
2033
2034 print_lock(hlock);
2035 }
2036
2037 print_chain_key_iteration(hlock_next->class_idx, chain_key);
2038 print_lock(hlock_next);
2039}
2040
2041static void print_chain_keys_chain(struct lock_chain *chain)
2042{
2043 int i;
2044 u64 chain_key = 0;
2045 int class_id;
2046
2047 printk("depth: %u\n", chain->depth);
2048 for (i = 0; i < chain->depth; i++) {
2049 class_id = chain_hlocks[chain->base + i];
2050 chain_key = print_chain_key_iteration(class_id + 1, chain_key);
2051
2052 print_lock_name(lock_classes + class_id);
2053 printk("\n");
2054 }
2055}
2056
2057static void print_collision(struct task_struct *curr,
2058 struct held_lock *hlock_next,
2059 struct lock_chain *chain)
2060{
2061 printk("\n");
2062 printk("======================\n");
2063 printk("[chain_key collision ]\n");
2064 print_kernel_ident();
2065 printk("----------------------\n");
2066 printk("%s/%d: ", current->comm, task_pid_nr(current));
2067 printk("Hash chain already cached but the contents don't match!\n");
2068
2069 printk("Held locks:");
2070 print_chain_keys_held_locks(curr, hlock_next);
2071
2072 printk("Locks in cached chain:");
2073 print_chain_keys_chain(chain);
2074
2075 printk("\nstack backtrace:\n");
2076 dump_stack();
2077}
2078#endif
2079
2080/*
2081 * Checks whether the chain and the current held locks are consistent
2082 * in depth and also in content. If they are not it most likely means
2083 * that there was a collision during the calculation of the chain_key.
2084 * Returns: 0 not passed, 1 passed
2085 */
2086static int check_no_collision(struct task_struct *curr,
2087 struct held_lock *hlock,
2088 struct lock_chain *chain)
2089{
2090#ifdef CONFIG_DEBUG_LOCKDEP
2091 int i, j, id;
2092
2093 i = get_first_held_lock(curr, hlock);
2094
2095 if (DEBUG_LOCKS_WARN_ON(chain->depth != curr->lockdep_depth - (i - 1))) {
2096 print_collision(curr, hlock, chain);
2097 return 0;
2098 }
2099
2100 for (j = 0; j < chain->depth - 1; j++, i++) {
2101 id = curr->held_locks[i].class_idx - 1;
2102
2103 if (DEBUG_LOCKS_WARN_ON(chain_hlocks[chain->base + j] != id)) {
2104 print_collision(curr, hlock, chain);
2105 return 0;
2106 }
2107 }
2108#endif
2109 return 1;
2110}
2111
2112/*
2113 * Look up a dependency chain. If the key is not present yet then
2114 * add it and return 1 - in this case the new dependency chain is
2115 * validated. If the key is already hashed, return 0.
2116 * (On return with 1 graph_lock is held.)
2117 */
2118static inline int lookup_chain_cache(struct task_struct *curr,
2119 struct held_lock *hlock,
2120 u64 chain_key)
2121{
2122 struct lock_class *class = hlock_class(hlock);
2123 struct hlist_head *hash_head = chainhashentry(chain_key);
2124 struct lock_chain *chain;
2125 int i, j;
2126
2127 /*
2128 * We might need to take the graph lock, ensure we've got IRQs
2129 * disabled to make this an IRQ-safe lock.. for recursion reasons
2130 * lockdep won't complain about its own locking errors.
2131 */
2132 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2133 return 0;
2134 /*
2135 * We can walk it lock-free, because entries only get added
2136 * to the hash:
2137 */
2138 hlist_for_each_entry_rcu(chain, hash_head, entry) {
2139 if (chain->chain_key == chain_key) {
2140cache_hit:
2141 debug_atomic_inc(chain_lookup_hits);
2142 if (!check_no_collision(curr, hlock, chain))
2143 return 0;
2144
2145 if (very_verbose(class))
2146 printk("\nhash chain already cached, key: "
2147 "%016Lx tail class: [%p] %s\n",
2148 (unsigned long long)chain_key,
2149 class->key, class->name);
2150 return 0;
2151 }
2152 }
2153 if (very_verbose(class))
2154 printk("\nnew hash chain, key: %016Lx tail class: [%p] %s\n",
2155 (unsigned long long)chain_key, class->key, class->name);
2156 /*
2157 * Allocate a new chain entry from the static array, and add
2158 * it to the hash:
2159 */
2160 if (!graph_lock())
2161 return 0;
2162 /*
2163 * We have to walk the chain again locked - to avoid duplicates:
2164 */
2165 hlist_for_each_entry(chain, hash_head, entry) {
2166 if (chain->chain_key == chain_key) {
2167 graph_unlock();
2168 goto cache_hit;
2169 }
2170 }
2171 if (unlikely(nr_lock_chains >= MAX_LOCKDEP_CHAINS)) {
2172 if (!debug_locks_off_graph_unlock())
2173 return 0;
2174
2175 print_lockdep_off("BUG: MAX_LOCKDEP_CHAINS too low!");
2176 dump_stack();
2177 return 0;
2178 }
2179 chain = lock_chains + nr_lock_chains++;
2180 chain->chain_key = chain_key;
2181 chain->irq_context = hlock->irq_context;
2182 i = get_first_held_lock(curr, hlock);
2183 chain->depth = curr->lockdep_depth + 1 - i;
2184
2185 BUILD_BUG_ON((1UL << 24) <= ARRAY_SIZE(chain_hlocks));
2186 BUILD_BUG_ON((1UL << 6) <= ARRAY_SIZE(curr->held_locks));
2187 BUILD_BUG_ON((1UL << 8*sizeof(chain_hlocks[0])) <= ARRAY_SIZE(lock_classes));
2188
2189 if (likely(nr_chain_hlocks + chain->depth <= MAX_LOCKDEP_CHAIN_HLOCKS)) {
2190 chain->base = nr_chain_hlocks;
2191 for (j = 0; j < chain->depth - 1; j++, i++) {
2192 int lock_id = curr->held_locks[i].class_idx - 1;
2193 chain_hlocks[chain->base + j] = lock_id;
2194 }
2195 chain_hlocks[chain->base + j] = class - lock_classes;
2196 }
2197
2198 if (nr_chain_hlocks < MAX_LOCKDEP_CHAIN_HLOCKS)
2199 nr_chain_hlocks += chain->depth;
2200
2201#ifdef CONFIG_DEBUG_LOCKDEP
2202 /*
2203 * Important for check_no_collision().
2204 */
2205 if (unlikely(nr_chain_hlocks > MAX_LOCKDEP_CHAIN_HLOCKS)) {
2206 if (debug_locks_off_graph_unlock())
2207 return 0;
2208
2209 print_lockdep_off("BUG: MAX_LOCKDEP_CHAIN_HLOCKS too low!");
2210 dump_stack();
2211 return 0;
2212 }
2213#endif
2214
2215 hlist_add_head_rcu(&chain->entry, hash_head);
2216 debug_atomic_inc(chain_lookup_misses);
2217 inc_chains();
2218
2219 return 1;
2220}
2221
2222static int validate_chain(struct task_struct *curr, struct lockdep_map *lock,
2223 struct held_lock *hlock, int chain_head, u64 chain_key)
2224{
2225 /*
2226 * Trylock needs to maintain the stack of held locks, but it
2227 * does not add new dependencies, because trylock can be done
2228 * in any order.
2229 *
2230 * We look up the chain_key and do the O(N^2) check and update of
2231 * the dependencies only if this is a new dependency chain.
2232 * (If lookup_chain_cache() returns with 1 it acquires
2233 * graph_lock for us)
2234 */
2235 if (!hlock->trylock && hlock->check &&
2236 lookup_chain_cache(curr, hlock, chain_key)) {
2237 /*
2238 * Check whether last held lock:
2239 *
2240 * - is irq-safe, if this lock is irq-unsafe
2241 * - is softirq-safe, if this lock is hardirq-unsafe
2242 *
2243 * And check whether the new lock's dependency graph
2244 * could lead back to the previous lock.
2245 *
2246 * any of these scenarios could lead to a deadlock. If
2247 * All validations
2248 */
2249 int ret = check_deadlock(curr, hlock, lock, hlock->read);
2250
2251 if (!ret)
2252 return 0;
2253 /*
2254 * Mark recursive read, as we jump over it when
2255 * building dependencies (just like we jump over
2256 * trylock entries):
2257 */
2258 if (ret == 2)
2259 hlock->read = 2;
2260 /*
2261 * Add dependency only if this lock is not the head
2262 * of the chain, and if it's not a secondary read-lock:
2263 */
2264 if (!chain_head && ret != 2)
2265 if (!check_prevs_add(curr, hlock))
2266 return 0;
2267 graph_unlock();
2268 } else
2269 /* after lookup_chain_cache(): */
2270 if (unlikely(!debug_locks))
2271 return 0;
2272
2273 return 1;
2274}
2275#else
2276static inline int validate_chain(struct task_struct *curr,
2277 struct lockdep_map *lock, struct held_lock *hlock,
2278 int chain_head, u64 chain_key)
2279{
2280 return 1;
2281}
2282#endif
2283
2284/*
2285 * We are building curr_chain_key incrementally, so double-check
2286 * it from scratch, to make sure that it's done correctly:
2287 */
2288static void check_chain_key(struct task_struct *curr)
2289{
2290#ifdef CONFIG_DEBUG_LOCKDEP
2291 struct held_lock *hlock, *prev_hlock = NULL;
2292 unsigned int i;
2293 u64 chain_key = 0;
2294
2295 for (i = 0; i < curr->lockdep_depth; i++) {
2296 hlock = curr->held_locks + i;
2297 if (chain_key != hlock->prev_chain_key) {
2298 debug_locks_off();
2299 /*
2300 * We got mighty confused, our chain keys don't match
2301 * with what we expect, someone trample on our task state?
2302 */
2303 WARN(1, "hm#1, depth: %u [%u], %016Lx != %016Lx\n",
2304 curr->lockdep_depth, i,
2305 (unsigned long long)chain_key,
2306 (unsigned long long)hlock->prev_chain_key);
2307 return;
2308 }
2309 /*
2310 * Whoops ran out of static storage again?
2311 */
2312 if (DEBUG_LOCKS_WARN_ON(hlock->class_idx > MAX_LOCKDEP_KEYS))
2313 return;
2314
2315 if (prev_hlock && (prev_hlock->irq_context !=
2316 hlock->irq_context))
2317 chain_key = 0;
2318 chain_key = iterate_chain_key(chain_key, hlock->class_idx);
2319 prev_hlock = hlock;
2320 }
2321 if (chain_key != curr->curr_chain_key) {
2322 debug_locks_off();
2323 /*
2324 * More smoking hash instead of calculating it, damn see these
2325 * numbers float.. I bet that a pink elephant stepped on my memory.
2326 */
2327 WARN(1, "hm#2, depth: %u [%u], %016Lx != %016Lx\n",
2328 curr->lockdep_depth, i,
2329 (unsigned long long)chain_key,
2330 (unsigned long long)curr->curr_chain_key);
2331 }
2332#endif
2333}
2334
2335static void
2336print_usage_bug_scenario(struct held_lock *lock)
2337{
2338 struct lock_class *class = hlock_class(lock);
2339
2340 printk(" Possible unsafe locking scenario:\n\n");
2341 printk(" CPU0\n");
2342 printk(" ----\n");
2343 printk(" lock(");
2344 __print_lock_name(class);
2345 printk(KERN_CONT ");\n");
2346 printk(" <Interrupt>\n");
2347 printk(" lock(");
2348 __print_lock_name(class);
2349 printk(KERN_CONT ");\n");
2350 printk("\n *** DEADLOCK ***\n\n");
2351}
2352
2353static int
2354print_usage_bug(struct task_struct *curr, struct held_lock *this,
2355 enum lock_usage_bit prev_bit, enum lock_usage_bit new_bit)
2356{
2357 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
2358 return 0;
2359
2360 printk("\n");
2361 printk("=================================\n");
2362 printk("[ INFO: inconsistent lock state ]\n");
2363 print_kernel_ident();
2364 printk("---------------------------------\n");
2365
2366 printk("inconsistent {%s} -> {%s} usage.\n",
2367 usage_str[prev_bit], usage_str[new_bit]);
2368
2369 printk("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] takes:\n",
2370 curr->comm, task_pid_nr(curr),
2371 trace_hardirq_context(curr), hardirq_count() >> HARDIRQ_SHIFT,
2372 trace_softirq_context(curr), softirq_count() >> SOFTIRQ_SHIFT,
2373 trace_hardirqs_enabled(curr),
2374 trace_softirqs_enabled(curr));
2375 print_lock(this);
2376
2377 printk("{%s} state was registered at:\n", usage_str[prev_bit]);
2378 print_stack_trace(hlock_class(this)->usage_traces + prev_bit, 1);
2379
2380 print_irqtrace_events(curr);
2381 printk("\nother info that might help us debug this:\n");
2382 print_usage_bug_scenario(this);
2383
2384 lockdep_print_held_locks(curr);
2385
2386 printk("\nstack backtrace:\n");
2387 dump_stack();
2388
2389 return 0;
2390}
2391
2392/*
2393 * Print out an error if an invalid bit is set:
2394 */
2395static inline int
2396valid_state(struct task_struct *curr, struct held_lock *this,
2397 enum lock_usage_bit new_bit, enum lock_usage_bit bad_bit)
2398{
2399 if (unlikely(hlock_class(this)->usage_mask & (1 << bad_bit)))
2400 return print_usage_bug(curr, this, bad_bit, new_bit);
2401 return 1;
2402}
2403
2404static int mark_lock(struct task_struct *curr, struct held_lock *this,
2405 enum lock_usage_bit new_bit);
2406
2407#if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
2408
2409/*
2410 * print irq inversion bug:
2411 */
2412static int
2413print_irq_inversion_bug(struct task_struct *curr,
2414 struct lock_list *root, struct lock_list *other,
2415 struct held_lock *this, int forwards,
2416 const char *irqclass)
2417{
2418 struct lock_list *entry = other;
2419 struct lock_list *middle = NULL;
2420 int depth;
2421
2422 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
2423 return 0;
2424
2425 printk("\n");
2426 printk("=========================================================\n");
2427 printk("[ INFO: possible irq lock inversion dependency detected ]\n");
2428 print_kernel_ident();
2429 printk("---------------------------------------------------------\n");
2430 printk("%s/%d just changed the state of lock:\n",
2431 curr->comm, task_pid_nr(curr));
2432 print_lock(this);
2433 if (forwards)
2434 printk("but this lock took another, %s-unsafe lock in the past:\n", irqclass);
2435 else
2436 printk("but this lock was taken by another, %s-safe lock in the past:\n", irqclass);
2437 print_lock_name(other->class);
2438 printk("\n\nand interrupts could create inverse lock ordering between them.\n\n");
2439
2440 printk("\nother info that might help us debug this:\n");
2441
2442 /* Find a middle lock (if one exists) */
2443 depth = get_lock_depth(other);
2444 do {
2445 if (depth == 0 && (entry != root)) {
2446 printk("lockdep:%s bad path found in chain graph\n", __func__);
2447 break;
2448 }
2449 middle = entry;
2450 entry = get_lock_parent(entry);
2451 depth--;
2452 } while (entry && entry != root && (depth >= 0));
2453 if (forwards)
2454 print_irq_lock_scenario(root, other,
2455 middle ? middle->class : root->class, other->class);
2456 else
2457 print_irq_lock_scenario(other, root,
2458 middle ? middle->class : other->class, root->class);
2459
2460 lockdep_print_held_locks(curr);
2461
2462 printk("\nthe shortest dependencies between 2nd lock and 1st lock:\n");
2463 if (!save_trace(&root->trace))
2464 return 0;
2465 print_shortest_lock_dependencies(other, root);
2466
2467 printk("\nstack backtrace:\n");
2468 dump_stack();
2469
2470 return 0;
2471}
2472
2473/*
2474 * Prove that in the forwards-direction subgraph starting at <this>
2475 * there is no lock matching <mask>:
2476 */
2477static int
2478check_usage_forwards(struct task_struct *curr, struct held_lock *this,
2479 enum lock_usage_bit bit, const char *irqclass)
2480{
2481 int ret;
2482 struct lock_list root;
2483 struct lock_list *uninitialized_var(target_entry);
2484
2485 root.parent = NULL;
2486 root.class = hlock_class(this);
2487 ret = find_usage_forwards(&root, bit, &target_entry);
2488 if (ret < 0)
2489 return print_bfs_bug(ret);
2490 if (ret == 1)
2491 return ret;
2492
2493 return print_irq_inversion_bug(curr, &root, target_entry,
2494 this, 1, irqclass);
2495}
2496
2497/*
2498 * Prove that in the backwards-direction subgraph starting at <this>
2499 * there is no lock matching <mask>:
2500 */
2501static int
2502check_usage_backwards(struct task_struct *curr, struct held_lock *this,
2503 enum lock_usage_bit bit, const char *irqclass)
2504{
2505 int ret;
2506 struct lock_list root;
2507 struct lock_list *uninitialized_var(target_entry);
2508
2509 root.parent = NULL;
2510 root.class = hlock_class(this);
2511 ret = find_usage_backwards(&root, bit, &target_entry);
2512 if (ret < 0)
2513 return print_bfs_bug(ret);
2514 if (ret == 1)
2515 return ret;
2516
2517 return print_irq_inversion_bug(curr, &root, target_entry,
2518 this, 0, irqclass);
2519}
2520
2521void print_irqtrace_events(struct task_struct *curr)
2522{
2523 printk("irq event stamp: %u\n", curr->irq_events);
2524 printk("hardirqs last enabled at (%u): [<%p>] %pS\n",
2525 curr->hardirq_enable_event, (void *)curr->hardirq_enable_ip,
2526 (void *)curr->hardirq_enable_ip);
2527 printk("hardirqs last disabled at (%u): [<%p>] %pS\n",
2528 curr->hardirq_disable_event, (void *)curr->hardirq_disable_ip,
2529 (void *)curr->hardirq_disable_ip);
2530 printk("softirqs last enabled at (%u): [<%p>] %pS\n",
2531 curr->softirq_enable_event, (void *)curr->softirq_enable_ip,
2532 (void *)curr->softirq_enable_ip);
2533 printk("softirqs last disabled at (%u): [<%p>] %pS\n",
2534 curr->softirq_disable_event, (void *)curr->softirq_disable_ip,
2535 (void *)curr->softirq_disable_ip);
2536}
2537
2538static int HARDIRQ_verbose(struct lock_class *class)
2539{
2540#if HARDIRQ_VERBOSE
2541 return class_filter(class);
2542#endif
2543 return 0;
2544}
2545
2546static int SOFTIRQ_verbose(struct lock_class *class)
2547{
2548#if SOFTIRQ_VERBOSE
2549 return class_filter(class);
2550#endif
2551 return 0;
2552}
2553
2554static int RECLAIM_FS_verbose(struct lock_class *class)
2555{
2556#if RECLAIM_VERBOSE
2557 return class_filter(class);
2558#endif
2559 return 0;
2560}
2561
2562#define STRICT_READ_CHECKS 1
2563
2564static int (*state_verbose_f[])(struct lock_class *class) = {
2565#define LOCKDEP_STATE(__STATE) \
2566 __STATE##_verbose,
2567#include "lockdep_states.h"
2568#undef LOCKDEP_STATE
2569};
2570
2571static inline int state_verbose(enum lock_usage_bit bit,
2572 struct lock_class *class)
2573{
2574 return state_verbose_f[bit >> 2](class);
2575}
2576
2577typedef int (*check_usage_f)(struct task_struct *, struct held_lock *,
2578 enum lock_usage_bit bit, const char *name);
2579
2580static int
2581mark_lock_irq(struct task_struct *curr, struct held_lock *this,
2582 enum lock_usage_bit new_bit)
2583{
2584 int excl_bit = exclusive_bit(new_bit);
2585 int read = new_bit & 1;
2586 int dir = new_bit & 2;
2587
2588 /*
2589 * mark USED_IN has to look forwards -- to ensure no dependency
2590 * has ENABLED state, which would allow recursion deadlocks.
2591 *
2592 * mark ENABLED has to look backwards -- to ensure no dependee
2593 * has USED_IN state, which, again, would allow recursion deadlocks.
2594 */
2595 check_usage_f usage = dir ?
2596 check_usage_backwards : check_usage_forwards;
2597
2598 /*
2599 * Validate that this particular lock does not have conflicting
2600 * usage states.
2601 */
2602 if (!valid_state(curr, this, new_bit, excl_bit))
2603 return 0;
2604
2605 /*
2606 * Validate that the lock dependencies don't have conflicting usage
2607 * states.
2608 */
2609 if ((!read || !dir || STRICT_READ_CHECKS) &&
2610 !usage(curr, this, excl_bit, state_name(new_bit & ~1)))
2611 return 0;
2612
2613 /*
2614 * Check for read in write conflicts
2615 */
2616 if (!read) {
2617 if (!valid_state(curr, this, new_bit, excl_bit + 1))
2618 return 0;
2619
2620 if (STRICT_READ_CHECKS &&
2621 !usage(curr, this, excl_bit + 1,
2622 state_name(new_bit + 1)))
2623 return 0;
2624 }
2625
2626 if (state_verbose(new_bit, hlock_class(this)))
2627 return 2;
2628
2629 return 1;
2630}
2631
2632enum mark_type {
2633#define LOCKDEP_STATE(__STATE) __STATE,
2634#include "lockdep_states.h"
2635#undef LOCKDEP_STATE
2636};
2637
2638/*
2639 * Mark all held locks with a usage bit:
2640 */
2641static int
2642mark_held_locks(struct task_struct *curr, enum mark_type mark)
2643{
2644 enum lock_usage_bit usage_bit;
2645 struct held_lock *hlock;
2646 int i;
2647
2648 for (i = 0; i < curr->lockdep_depth; i++) {
2649 hlock = curr->held_locks + i;
2650
2651 usage_bit = 2 + (mark << 2); /* ENABLED */
2652 if (hlock->read)
2653 usage_bit += 1; /* READ */
2654
2655 BUG_ON(usage_bit >= LOCK_USAGE_STATES);
2656
2657 if (!hlock->check)
2658 continue;
2659
2660 if (!mark_lock(curr, hlock, usage_bit))
2661 return 0;
2662 }
2663
2664 return 1;
2665}
2666
2667/*
2668 * Hardirqs will be enabled:
2669 */
2670static void __trace_hardirqs_on_caller(unsigned long ip)
2671{
2672 struct task_struct *curr = current;
2673
2674 /* we'll do an OFF -> ON transition: */
2675 curr->hardirqs_enabled = 1;
2676
2677 /*
2678 * We are going to turn hardirqs on, so set the
2679 * usage bit for all held locks:
2680 */
2681 if (!mark_held_locks(curr, HARDIRQ))
2682 return;
2683 /*
2684 * If we have softirqs enabled, then set the usage
2685 * bit for all held locks. (disabled hardirqs prevented
2686 * this bit from being set before)
2687 */
2688 if (curr->softirqs_enabled)
2689 if (!mark_held_locks(curr, SOFTIRQ))
2690 return;
2691
2692 curr->hardirq_enable_ip = ip;
2693 curr->hardirq_enable_event = ++curr->irq_events;
2694 debug_atomic_inc(hardirqs_on_events);
2695}
2696
2697__visible void trace_hardirqs_on_caller(unsigned long ip)
2698{
2699 time_hardirqs_on(CALLER_ADDR0, ip);
2700
2701 if (unlikely(!debug_locks || current->lockdep_recursion))
2702 return;
2703
2704 if (unlikely(current->hardirqs_enabled)) {
2705 /*
2706 * Neither irq nor preemption are disabled here
2707 * so this is racy by nature but losing one hit
2708 * in a stat is not a big deal.
2709 */
2710 __debug_atomic_inc(redundant_hardirqs_on);
2711 return;
2712 }
2713
2714 /*
2715 * We're enabling irqs and according to our state above irqs weren't
2716 * already enabled, yet we find the hardware thinks they are in fact
2717 * enabled.. someone messed up their IRQ state tracing.
2718 */
2719 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2720 return;
2721
2722 /*
2723 * See the fine text that goes along with this variable definition.
2724 */
2725 if (DEBUG_LOCKS_WARN_ON(unlikely(early_boot_irqs_disabled)))
2726 return;
2727
2728 /*
2729 * Can't allow enabling interrupts while in an interrupt handler,
2730 * that's general bad form and such. Recursion, limited stack etc..
2731 */
2732 if (DEBUG_LOCKS_WARN_ON(current->hardirq_context))
2733 return;
2734
2735 current->lockdep_recursion = 1;
2736 __trace_hardirqs_on_caller(ip);
2737 current->lockdep_recursion = 0;
2738}
2739EXPORT_SYMBOL(trace_hardirqs_on_caller);
2740
2741void trace_hardirqs_on(void)
2742{
2743 trace_hardirqs_on_caller(CALLER_ADDR0);
2744}
2745EXPORT_SYMBOL(trace_hardirqs_on);
2746
2747/*
2748 * Hardirqs were disabled:
2749 */
2750__visible void trace_hardirqs_off_caller(unsigned long ip)
2751{
2752 struct task_struct *curr = current;
2753
2754 time_hardirqs_off(CALLER_ADDR0, ip);
2755
2756 if (unlikely(!debug_locks || current->lockdep_recursion))
2757 return;
2758
2759 /*
2760 * So we're supposed to get called after you mask local IRQs, but for
2761 * some reason the hardware doesn't quite think you did a proper job.
2762 */
2763 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2764 return;
2765
2766 if (curr->hardirqs_enabled) {
2767 /*
2768 * We have done an ON -> OFF transition:
2769 */
2770 curr->hardirqs_enabled = 0;
2771 curr->hardirq_disable_ip = ip;
2772 curr->hardirq_disable_event = ++curr->irq_events;
2773 debug_atomic_inc(hardirqs_off_events);
2774 } else
2775 debug_atomic_inc(redundant_hardirqs_off);
2776}
2777EXPORT_SYMBOL(trace_hardirqs_off_caller);
2778
2779void trace_hardirqs_off(void)
2780{
2781 trace_hardirqs_off_caller(CALLER_ADDR0);
2782}
2783EXPORT_SYMBOL(trace_hardirqs_off);
2784
2785/*
2786 * Softirqs will be enabled:
2787 */
2788void trace_softirqs_on(unsigned long ip)
2789{
2790 struct task_struct *curr = current;
2791
2792 if (unlikely(!debug_locks || current->lockdep_recursion))
2793 return;
2794
2795 /*
2796 * We fancy IRQs being disabled here, see softirq.c, avoids
2797 * funny state and nesting things.
2798 */
2799 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2800 return;
2801
2802 if (curr->softirqs_enabled) {
2803 debug_atomic_inc(redundant_softirqs_on);
2804 return;
2805 }
2806
2807 current->lockdep_recursion = 1;
2808 /*
2809 * We'll do an OFF -> ON transition:
2810 */
2811 curr->softirqs_enabled = 1;
2812 curr->softirq_enable_ip = ip;
2813 curr->softirq_enable_event = ++curr->irq_events;
2814 debug_atomic_inc(softirqs_on_events);
2815 /*
2816 * We are going to turn softirqs on, so set the
2817 * usage bit for all held locks, if hardirqs are
2818 * enabled too:
2819 */
2820 if (curr->hardirqs_enabled)
2821 mark_held_locks(curr, SOFTIRQ);
2822 current->lockdep_recursion = 0;
2823}
2824
2825/*
2826 * Softirqs were disabled:
2827 */
2828void trace_softirqs_off(unsigned long ip)
2829{
2830 struct task_struct *curr = current;
2831
2832 if (unlikely(!debug_locks || current->lockdep_recursion))
2833 return;
2834
2835 /*
2836 * We fancy IRQs being disabled here, see softirq.c
2837 */
2838 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
2839 return;
2840
2841 if (curr->softirqs_enabled) {
2842 /*
2843 * We have done an ON -> OFF transition:
2844 */
2845 curr->softirqs_enabled = 0;
2846 curr->softirq_disable_ip = ip;
2847 curr->softirq_disable_event = ++curr->irq_events;
2848 debug_atomic_inc(softirqs_off_events);
2849 /*
2850 * Whoops, we wanted softirqs off, so why aren't they?
2851 */
2852 DEBUG_LOCKS_WARN_ON(!softirq_count());
2853 } else
2854 debug_atomic_inc(redundant_softirqs_off);
2855}
2856
2857static void __lockdep_trace_alloc(gfp_t gfp_mask, unsigned long flags)
2858{
2859 struct task_struct *curr = current;
2860
2861 if (unlikely(!debug_locks))
2862 return;
2863
2864 /* no reclaim without waiting on it */
2865 if (!(gfp_mask & __GFP_DIRECT_RECLAIM))
2866 return;
2867
2868 /* this guy won't enter reclaim */
2869 if ((curr->flags & PF_MEMALLOC) && !(gfp_mask & __GFP_NOMEMALLOC))
2870 return;
2871
2872 /* We're only interested __GFP_FS allocations for now */
2873 if (!(gfp_mask & __GFP_FS))
2874 return;
2875
2876 /*
2877 * Oi! Can't be having __GFP_FS allocations with IRQs disabled.
2878 */
2879 if (DEBUG_LOCKS_WARN_ON(irqs_disabled_flags(flags)))
2880 return;
2881
2882 mark_held_locks(curr, RECLAIM_FS);
2883}
2884
2885static void check_flags(unsigned long flags);
2886
2887void lockdep_trace_alloc(gfp_t gfp_mask)
2888{
2889 unsigned long flags;
2890
2891 if (unlikely(current->lockdep_recursion))
2892 return;
2893
2894 raw_local_irq_save(flags);
2895 check_flags(flags);
2896 current->lockdep_recursion = 1;
2897 __lockdep_trace_alloc(gfp_mask, flags);
2898 current->lockdep_recursion = 0;
2899 raw_local_irq_restore(flags);
2900}
2901
2902static int mark_irqflags(struct task_struct *curr, struct held_lock *hlock)
2903{
2904 /*
2905 * If non-trylock use in a hardirq or softirq context, then
2906 * mark the lock as used in these contexts:
2907 */
2908 if (!hlock->trylock) {
2909 if (hlock->read) {
2910 if (curr->hardirq_context)
2911 if (!mark_lock(curr, hlock,
2912 LOCK_USED_IN_HARDIRQ_READ))
2913 return 0;
2914 if (curr->softirq_context)
2915 if (!mark_lock(curr, hlock,
2916 LOCK_USED_IN_SOFTIRQ_READ))
2917 return 0;
2918 } else {
2919 if (curr->hardirq_context)
2920 if (!mark_lock(curr, hlock, LOCK_USED_IN_HARDIRQ))
2921 return 0;
2922 if (curr->softirq_context)
2923 if (!mark_lock(curr, hlock, LOCK_USED_IN_SOFTIRQ))
2924 return 0;
2925 }
2926 }
2927 if (!hlock->hardirqs_off) {
2928 if (hlock->read) {
2929 if (!mark_lock(curr, hlock,
2930 LOCK_ENABLED_HARDIRQ_READ))
2931 return 0;
2932 if (curr->softirqs_enabled)
2933 if (!mark_lock(curr, hlock,
2934 LOCK_ENABLED_SOFTIRQ_READ))
2935 return 0;
2936 } else {
2937 if (!mark_lock(curr, hlock,
2938 LOCK_ENABLED_HARDIRQ))
2939 return 0;
2940 if (curr->softirqs_enabled)
2941 if (!mark_lock(curr, hlock,
2942 LOCK_ENABLED_SOFTIRQ))
2943 return 0;
2944 }
2945 }
2946
2947 /*
2948 * We reuse the irq context infrastructure more broadly as a general
2949 * context checking code. This tests GFP_FS recursion (a lock taken
2950 * during reclaim for a GFP_FS allocation is held over a GFP_FS
2951 * allocation).
2952 */
2953 if (!hlock->trylock && (curr->lockdep_reclaim_gfp & __GFP_FS)) {
2954 if (hlock->read) {
2955 if (!mark_lock(curr, hlock, LOCK_USED_IN_RECLAIM_FS_READ))
2956 return 0;
2957 } else {
2958 if (!mark_lock(curr, hlock, LOCK_USED_IN_RECLAIM_FS))
2959 return 0;
2960 }
2961 }
2962
2963 return 1;
2964}
2965
2966static inline unsigned int task_irq_context(struct task_struct *task)
2967{
2968 return 2 * !!task->hardirq_context + !!task->softirq_context;
2969}
2970
2971static int separate_irq_context(struct task_struct *curr,
2972 struct held_lock *hlock)
2973{
2974 unsigned int depth = curr->lockdep_depth;
2975
2976 /*
2977 * Keep track of points where we cross into an interrupt context:
2978 */
2979 if (depth) {
2980 struct held_lock *prev_hlock;
2981
2982 prev_hlock = curr->held_locks + depth-1;
2983 /*
2984 * If we cross into another context, reset the
2985 * hash key (this also prevents the checking and the
2986 * adding of the dependency to 'prev'):
2987 */
2988 if (prev_hlock->irq_context != hlock->irq_context)
2989 return 1;
2990 }
2991 return 0;
2992}
2993
2994#else /* defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING) */
2995
2996static inline
2997int mark_lock_irq(struct task_struct *curr, struct held_lock *this,
2998 enum lock_usage_bit new_bit)
2999{
3000 WARN_ON(1); /* Impossible innit? when we don't have TRACE_IRQFLAG */
3001 return 1;
3002}
3003
3004static inline int mark_irqflags(struct task_struct *curr,
3005 struct held_lock *hlock)
3006{
3007 return 1;
3008}
3009
3010static inline unsigned int task_irq_context(struct task_struct *task)
3011{
3012 return 0;
3013}
3014
3015static inline int separate_irq_context(struct task_struct *curr,
3016 struct held_lock *hlock)
3017{
3018 return 0;
3019}
3020
3021void lockdep_trace_alloc(gfp_t gfp_mask)
3022{
3023}
3024
3025#endif /* defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING) */
3026
3027/*
3028 * Mark a lock with a usage bit, and validate the state transition:
3029 */
3030static int mark_lock(struct task_struct *curr, struct held_lock *this,
3031 enum lock_usage_bit new_bit)
3032{
3033 unsigned int new_mask = 1 << new_bit, ret = 1;
3034
3035 /*
3036 * If already set then do not dirty the cacheline,
3037 * nor do any checks:
3038 */
3039 if (likely(hlock_class(this)->usage_mask & new_mask))
3040 return 1;
3041
3042 if (!graph_lock())
3043 return 0;
3044 /*
3045 * Make sure we didn't race:
3046 */
3047 if (unlikely(hlock_class(this)->usage_mask & new_mask)) {
3048 graph_unlock();
3049 return 1;
3050 }
3051
3052 hlock_class(this)->usage_mask |= new_mask;
3053
3054 if (!save_trace(hlock_class(this)->usage_traces + new_bit))
3055 return 0;
3056
3057 switch (new_bit) {
3058#define LOCKDEP_STATE(__STATE) \
3059 case LOCK_USED_IN_##__STATE: \
3060 case LOCK_USED_IN_##__STATE##_READ: \
3061 case LOCK_ENABLED_##__STATE: \
3062 case LOCK_ENABLED_##__STATE##_READ:
3063#include "lockdep_states.h"
3064#undef LOCKDEP_STATE
3065 ret = mark_lock_irq(curr, this, new_bit);
3066 if (!ret)
3067 return 0;
3068 break;
3069 case LOCK_USED:
3070 debug_atomic_dec(nr_unused_locks);
3071 break;
3072 default:
3073 if (!debug_locks_off_graph_unlock())
3074 return 0;
3075 WARN_ON(1);
3076 return 0;
3077 }
3078
3079 graph_unlock();
3080
3081 /*
3082 * We must printk outside of the graph_lock:
3083 */
3084 if (ret == 2) {
3085 printk("\nmarked lock as {%s}:\n", usage_str[new_bit]);
3086 print_lock(this);
3087 print_irqtrace_events(curr);
3088 dump_stack();
3089 }
3090
3091 return ret;
3092}
3093
3094/*
3095 * Initialize a lock instance's lock-class mapping info:
3096 */
3097void lockdep_init_map(struct lockdep_map *lock, const char *name,
3098 struct lock_class_key *key, int subclass)
3099{
3100 int i;
3101
3102 kmemcheck_mark_initialized(lock, sizeof(*lock));
3103
3104 for (i = 0; i < NR_LOCKDEP_CACHING_CLASSES; i++)
3105 lock->class_cache[i] = NULL;
3106
3107#ifdef CONFIG_LOCK_STAT
3108 lock->cpu = raw_smp_processor_id();
3109#endif
3110
3111 /*
3112 * Can't be having no nameless bastards around this place!
3113 */
3114 if (DEBUG_LOCKS_WARN_ON(!name)) {
3115 lock->name = "NULL";
3116 return;
3117 }
3118
3119 lock->name = name;
3120
3121 /*
3122 * No key, no joy, we need to hash something.
3123 */
3124 if (DEBUG_LOCKS_WARN_ON(!key))
3125 return;
3126 /*
3127 * Sanity check, the lock-class key must be persistent:
3128 */
3129 if (!static_obj(key)) {
3130 printk("BUG: key %p not in .data!\n", key);
3131 /*
3132 * What it says above ^^^^^, I suggest you read it.
3133 */
3134 DEBUG_LOCKS_WARN_ON(1);
3135 return;
3136 }
3137 lock->key = key;
3138
3139 if (unlikely(!debug_locks))
3140 return;
3141
3142 if (subclass) {
3143 unsigned long flags;
3144
3145 if (DEBUG_LOCKS_WARN_ON(current->lockdep_recursion))
3146 return;
3147
3148 raw_local_irq_save(flags);
3149 current->lockdep_recursion = 1;
3150 register_lock_class(lock, subclass, 1);
3151 current->lockdep_recursion = 0;
3152 raw_local_irq_restore(flags);
3153 }
3154}
3155EXPORT_SYMBOL_GPL(lockdep_init_map);
3156
3157struct lock_class_key __lockdep_no_validate__;
3158EXPORT_SYMBOL_GPL(__lockdep_no_validate__);
3159
3160static int
3161print_lock_nested_lock_not_held(struct task_struct *curr,
3162 struct held_lock *hlock,
3163 unsigned long ip)
3164{
3165 if (!debug_locks_off())
3166 return 0;
3167 if (debug_locks_silent)
3168 return 0;
3169
3170 printk("\n");
3171 printk("==================================\n");
3172 printk("[ BUG: Nested lock was not taken ]\n");
3173 print_kernel_ident();
3174 printk("----------------------------------\n");
3175
3176 printk("%s/%d is trying to lock:\n", curr->comm, task_pid_nr(curr));
3177 print_lock(hlock);
3178
3179 printk("\nbut this task is not holding:\n");
3180 printk("%s\n", hlock->nest_lock->name);
3181
3182 printk("\nstack backtrace:\n");
3183 dump_stack();
3184
3185 printk("\nother info that might help us debug this:\n");
3186 lockdep_print_held_locks(curr);
3187
3188 printk("\nstack backtrace:\n");
3189 dump_stack();
3190
3191 return 0;
3192}
3193
3194static int __lock_is_held(struct lockdep_map *lock, int read);
3195
3196/*
3197 * This gets called for every mutex_lock*()/spin_lock*() operation.
3198 * We maintain the dependency maps and validate the locking attempt:
3199 */
3200static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
3201 int trylock, int read, int check, int hardirqs_off,
3202 struct lockdep_map *nest_lock, unsigned long ip,
3203 int references, int pin_count)
3204{
3205 struct task_struct *curr = current;
3206 struct lock_class *class = NULL;
3207 struct held_lock *hlock;
3208 unsigned int depth;
3209 int chain_head = 0;
3210 int class_idx;
3211 u64 chain_key;
3212
3213 if (unlikely(!debug_locks))
3214 return 0;
3215
3216 /*
3217 * Lockdep should run with IRQs disabled, otherwise we could
3218 * get an interrupt which would want to take locks, which would
3219 * end up in lockdep and have you got a head-ache already?
3220 */
3221 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
3222 return 0;
3223
3224 if (!prove_locking || lock->key == &__lockdep_no_validate__)
3225 check = 0;
3226
3227 if (subclass < NR_LOCKDEP_CACHING_CLASSES)
3228 class = lock->class_cache[subclass];
3229 /*
3230 * Not cached?
3231 */
3232 if (unlikely(!class)) {
3233 class = register_lock_class(lock, subclass, 0);
3234 if (!class)
3235 return 0;
3236 }
3237 atomic_inc((atomic_t *)&class->ops);
3238 if (very_verbose(class)) {
3239 printk("\nacquire class [%p] %s", class->key, class->name);
3240 if (class->name_version > 1)
3241 printk(KERN_CONT "#%d", class->name_version);
3242 printk(KERN_CONT "\n");
3243 dump_stack();
3244 }
3245
3246 /*
3247 * Add the lock to the list of currently held locks.
3248 * (we dont increase the depth just yet, up until the
3249 * dependency checks are done)
3250 */
3251 depth = curr->lockdep_depth;
3252 /*
3253 * Ran out of static storage for our per-task lock stack again have we?
3254 */
3255 if (DEBUG_LOCKS_WARN_ON(depth >= MAX_LOCK_DEPTH))
3256 return 0;
3257
3258 class_idx = class - lock_classes + 1;
3259
3260 if (depth) {
3261 hlock = curr->held_locks + depth - 1;
3262 if (hlock->class_idx == class_idx && nest_lock) {
3263 if (hlock->references)
3264 hlock->references++;
3265 else
3266 hlock->references = 2;
3267
3268 return 1;
3269 }
3270 }
3271
3272 hlock = curr->held_locks + depth;
3273 /*
3274 * Plain impossible, we just registered it and checked it weren't no
3275 * NULL like.. I bet this mushroom I ate was good!
3276 */
3277 if (DEBUG_LOCKS_WARN_ON(!class))
3278 return 0;
3279 hlock->class_idx = class_idx;
3280 hlock->acquire_ip = ip;
3281 hlock->instance = lock;
3282 hlock->nest_lock = nest_lock;
3283 hlock->irq_context = task_irq_context(curr);
3284 hlock->trylock = trylock;
3285 hlock->read = read;
3286 hlock->check = check;
3287 hlock->hardirqs_off = !!hardirqs_off;
3288 hlock->references = references;
3289#ifdef CONFIG_LOCK_STAT
3290 hlock->waittime_stamp = 0;
3291 hlock->holdtime_stamp = lockstat_clock();
3292#endif
3293 hlock->pin_count = pin_count;
3294
3295 if (check && !mark_irqflags(curr, hlock))
3296 return 0;
3297
3298 /* mark it as used: */
3299 if (!mark_lock(curr, hlock, LOCK_USED))
3300 return 0;
3301
3302 /*
3303 * Calculate the chain hash: it's the combined hash of all the
3304 * lock keys along the dependency chain. We save the hash value
3305 * at every step so that we can get the current hash easily
3306 * after unlock. The chain hash is then used to cache dependency
3307 * results.
3308 *
3309 * The 'key ID' is what is the most compact key value to drive
3310 * the hash, not class->key.
3311 */
3312 /*
3313 * Whoops, we did it again.. ran straight out of our static allocation.
3314 */
3315 if (DEBUG_LOCKS_WARN_ON(class_idx > MAX_LOCKDEP_KEYS))
3316 return 0;
3317
3318 chain_key = curr->curr_chain_key;
3319 if (!depth) {
3320 /*
3321 * How can we have a chain hash when we ain't got no keys?!
3322 */
3323 if (DEBUG_LOCKS_WARN_ON(chain_key != 0))
3324 return 0;
3325 chain_head = 1;
3326 }
3327
3328 hlock->prev_chain_key = chain_key;
3329 if (separate_irq_context(curr, hlock)) {
3330 chain_key = 0;
3331 chain_head = 1;
3332 }
3333 chain_key = iterate_chain_key(chain_key, class_idx);
3334
3335 if (nest_lock && !__lock_is_held(nest_lock, -1))
3336 return print_lock_nested_lock_not_held(curr, hlock, ip);
3337
3338 if (!validate_chain(curr, lock, hlock, chain_head, chain_key))
3339 return 0;
3340
3341 curr->curr_chain_key = chain_key;
3342 curr->lockdep_depth++;
3343 check_chain_key(curr);
3344#ifdef CONFIG_DEBUG_LOCKDEP
3345 if (unlikely(!debug_locks))
3346 return 0;
3347#endif
3348 if (unlikely(curr->lockdep_depth >= MAX_LOCK_DEPTH)) {
3349 debug_locks_off();
3350 print_lockdep_off("BUG: MAX_LOCK_DEPTH too low!");
3351 printk(KERN_DEBUG "depth: %i max: %lu!\n",
3352 curr->lockdep_depth, MAX_LOCK_DEPTH);
3353
3354 lockdep_print_held_locks(current);
3355 debug_show_all_locks();
3356 dump_stack();
3357
3358 return 0;
3359 }
3360
3361 if (unlikely(curr->lockdep_depth > max_lockdep_depth))
3362 max_lockdep_depth = curr->lockdep_depth;
3363
3364 return 1;
3365}
3366
3367static int
3368print_unlock_imbalance_bug(struct task_struct *curr, struct lockdep_map *lock,
3369 unsigned long ip)
3370{
3371 if (!debug_locks_off())
3372 return 0;
3373 if (debug_locks_silent)
3374 return 0;
3375
3376 printk("\n");
3377 printk("=====================================\n");
3378 printk("[ BUG: bad unlock balance detected! ]\n");
3379 print_kernel_ident();
3380 printk("-------------------------------------\n");
3381 printk("%s/%d is trying to release lock (",
3382 curr->comm, task_pid_nr(curr));
3383 print_lockdep_cache(lock);
3384 printk(KERN_CONT ") at:\n");
3385 print_ip_sym(ip);
3386 printk("but there are no more locks to release!\n");
3387 printk("\nother info that might help us debug this:\n");
3388 lockdep_print_held_locks(curr);
3389
3390 printk("\nstack backtrace:\n");
3391 dump_stack();
3392
3393 return 0;
3394}
3395
3396static int match_held_lock(struct held_lock *hlock, struct lockdep_map *lock)
3397{
3398 if (hlock->instance == lock)
3399 return 1;
3400
3401 if (hlock->references) {
3402 struct lock_class *class = lock->class_cache[0];
3403
3404 if (!class)
3405 class = look_up_lock_class(lock, 0);
3406
3407 /*
3408 * If look_up_lock_class() failed to find a class, we're trying
3409 * to test if we hold a lock that has never yet been acquired.
3410 * Clearly if the lock hasn't been acquired _ever_, we're not
3411 * holding it either, so report failure.
3412 */
3413 if (!class)
3414 return 0;
3415
3416 /*
3417 * References, but not a lock we're actually ref-counting?
3418 * State got messed up, follow the sites that change ->references
3419 * and try to make sense of it.
3420 */
3421 if (DEBUG_LOCKS_WARN_ON(!hlock->nest_lock))
3422 return 0;
3423
3424 if (hlock->class_idx == class - lock_classes + 1)
3425 return 1;
3426 }
3427
3428 return 0;
3429}
3430
3431static int
3432__lock_set_class(struct lockdep_map *lock, const char *name,
3433 struct lock_class_key *key, unsigned int subclass,
3434 unsigned long ip)
3435{
3436 struct task_struct *curr = current;
3437 struct held_lock *hlock, *prev_hlock;
3438 struct lock_class *class;
3439 unsigned int depth;
3440 int i;
3441
3442 depth = curr->lockdep_depth;
3443 /*
3444 * This function is about (re)setting the class of a held lock,
3445 * yet we're not actually holding any locks. Naughty user!
3446 */
3447 if (DEBUG_LOCKS_WARN_ON(!depth))
3448 return 0;
3449
3450 prev_hlock = NULL;
3451 for (i = depth-1; i >= 0; i--) {
3452 hlock = curr->held_locks + i;
3453 /*
3454 * We must not cross into another context:
3455 */
3456 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
3457 break;
3458 if (match_held_lock(hlock, lock))
3459 goto found_it;
3460 prev_hlock = hlock;
3461 }
3462 return print_unlock_imbalance_bug(curr, lock, ip);
3463
3464found_it:
3465 lockdep_init_map(lock, name, key, 0);
3466 class = register_lock_class(lock, subclass, 0);
3467 hlock->class_idx = class - lock_classes + 1;
3468
3469 curr->lockdep_depth = i;
3470 curr->curr_chain_key = hlock->prev_chain_key;
3471
3472 for (; i < depth; i++) {
3473 hlock = curr->held_locks + i;
3474 if (!__lock_acquire(hlock->instance,
3475 hlock_class(hlock)->subclass, hlock->trylock,
3476 hlock->read, hlock->check, hlock->hardirqs_off,
3477 hlock->nest_lock, hlock->acquire_ip,
3478 hlock->references, hlock->pin_count))
3479 return 0;
3480 }
3481
3482 /*
3483 * I took it apart and put it back together again, except now I have
3484 * these 'spare' parts.. where shall I put them.
3485 */
3486 if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth))
3487 return 0;
3488 return 1;
3489}
3490
3491/*
3492 * Remove the lock to the list of currently held locks - this gets
3493 * called on mutex_unlock()/spin_unlock*() (or on a failed
3494 * mutex_lock_interruptible()).
3495 *
3496 * @nested is an hysterical artifact, needs a tree wide cleanup.
3497 */
3498static int
3499__lock_release(struct lockdep_map *lock, int nested, unsigned long ip)
3500{
3501 struct task_struct *curr = current;
3502 struct held_lock *hlock, *prev_hlock;
3503 unsigned int depth;
3504 int i;
3505
3506 if (unlikely(!debug_locks))
3507 return 0;
3508
3509 depth = curr->lockdep_depth;
3510 /*
3511 * So we're all set to release this lock.. wait what lock? We don't
3512 * own any locks, you've been drinking again?
3513 */
3514 if (DEBUG_LOCKS_WARN_ON(depth <= 0))
3515 return print_unlock_imbalance_bug(curr, lock, ip);
3516
3517 /*
3518 * Check whether the lock exists in the current stack
3519 * of held locks:
3520 */
3521 prev_hlock = NULL;
3522 for (i = depth-1; i >= 0; i--) {
3523 hlock = curr->held_locks + i;
3524 /*
3525 * We must not cross into another context:
3526 */
3527 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
3528 break;
3529 if (match_held_lock(hlock, lock))
3530 goto found_it;
3531 prev_hlock = hlock;
3532 }
3533 return print_unlock_imbalance_bug(curr, lock, ip);
3534
3535found_it:
3536 if (hlock->instance == lock)
3537 lock_release_holdtime(hlock);
3538
3539 WARN(hlock->pin_count, "releasing a pinned lock\n");
3540
3541 if (hlock->references) {
3542 hlock->references--;
3543 if (hlock->references) {
3544 /*
3545 * We had, and after removing one, still have
3546 * references, the current lock stack is still
3547 * valid. We're done!
3548 */
3549 return 1;
3550 }
3551 }
3552
3553 /*
3554 * We have the right lock to unlock, 'hlock' points to it.
3555 * Now we remove it from the stack, and add back the other
3556 * entries (if any), recalculating the hash along the way:
3557 */
3558
3559 curr->lockdep_depth = i;
3560 curr->curr_chain_key = hlock->prev_chain_key;
3561
3562 for (i++; i < depth; i++) {
3563 hlock = curr->held_locks + i;
3564 if (!__lock_acquire(hlock->instance,
3565 hlock_class(hlock)->subclass, hlock->trylock,
3566 hlock->read, hlock->check, hlock->hardirqs_off,
3567 hlock->nest_lock, hlock->acquire_ip,
3568 hlock->references, hlock->pin_count))
3569 return 0;
3570 }
3571
3572 /*
3573 * We had N bottles of beer on the wall, we drank one, but now
3574 * there's not N-1 bottles of beer left on the wall...
3575 */
3576 if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - 1))
3577 return 0;
3578
3579 return 1;
3580}
3581
3582static int __lock_is_held(struct lockdep_map *lock, int read)
3583{
3584 struct task_struct *curr = current;
3585 int i;
3586
3587 for (i = 0; i < curr->lockdep_depth; i++) {
3588 struct held_lock *hlock = curr->held_locks + i;
3589
3590 if (match_held_lock(hlock, lock)) {
3591 if (read == -1 || hlock->read == read)
3592 return 1;
3593
3594 return 0;
3595 }
3596 }
3597
3598 return 0;
3599}
3600
3601static struct pin_cookie __lock_pin_lock(struct lockdep_map *lock)
3602{
3603 struct pin_cookie cookie = NIL_COOKIE;
3604 struct task_struct *curr = current;
3605 int i;
3606
3607 if (unlikely(!debug_locks))
3608 return cookie;
3609
3610 for (i = 0; i < curr->lockdep_depth; i++) {
3611 struct held_lock *hlock = curr->held_locks + i;
3612
3613 if (match_held_lock(hlock, lock)) {
3614 /*
3615 * Grab 16bits of randomness; this is sufficient to not
3616 * be guessable and still allows some pin nesting in
3617 * our u32 pin_count.
3618 */
3619 cookie.val = 1 + (prandom_u32() >> 16);
3620 hlock->pin_count += cookie.val;
3621 return cookie;
3622 }
3623 }
3624
3625 WARN(1, "pinning an unheld lock\n");
3626 return cookie;
3627}
3628
3629static void __lock_repin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
3630{
3631 struct task_struct *curr = current;
3632 int i;
3633
3634 if (unlikely(!debug_locks))
3635 return;
3636
3637 for (i = 0; i < curr->lockdep_depth; i++) {
3638 struct held_lock *hlock = curr->held_locks + i;
3639
3640 if (match_held_lock(hlock, lock)) {
3641 hlock->pin_count += cookie.val;
3642 return;
3643 }
3644 }
3645
3646 WARN(1, "pinning an unheld lock\n");
3647}
3648
3649static void __lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
3650{
3651 struct task_struct *curr = current;
3652 int i;
3653
3654 if (unlikely(!debug_locks))
3655 return;
3656
3657 for (i = 0; i < curr->lockdep_depth; i++) {
3658 struct held_lock *hlock = curr->held_locks + i;
3659
3660 if (match_held_lock(hlock, lock)) {
3661 if (WARN(!hlock->pin_count, "unpinning an unpinned lock\n"))
3662 return;
3663
3664 hlock->pin_count -= cookie.val;
3665
3666 if (WARN((int)hlock->pin_count < 0, "pin count corrupted\n"))
3667 hlock->pin_count = 0;
3668
3669 return;
3670 }
3671 }
3672
3673 WARN(1, "unpinning an unheld lock\n");
3674}
3675
3676/*
3677 * Check whether we follow the irq-flags state precisely:
3678 */
3679static void check_flags(unsigned long flags)
3680{
3681#if defined(CONFIG_PROVE_LOCKING) && defined(CONFIG_DEBUG_LOCKDEP) && \
3682 defined(CONFIG_TRACE_IRQFLAGS)
3683 if (!debug_locks)
3684 return;
3685
3686 if (irqs_disabled_flags(flags)) {
3687 if (DEBUG_LOCKS_WARN_ON(current->hardirqs_enabled)) {
3688 printk("possible reason: unannotated irqs-off.\n");
3689 }
3690 } else {
3691 if (DEBUG_LOCKS_WARN_ON(!current->hardirqs_enabled)) {
3692 printk("possible reason: unannotated irqs-on.\n");
3693 }
3694 }
3695
3696 /*
3697 * We dont accurately track softirq state in e.g.
3698 * hardirq contexts (such as on 4KSTACKS), so only
3699 * check if not in hardirq contexts:
3700 */
3701 if (!hardirq_count()) {
3702 if (softirq_count()) {
3703 /* like the above, but with softirqs */
3704 DEBUG_LOCKS_WARN_ON(current->softirqs_enabled);
3705 } else {
3706 /* lick the above, does it taste good? */
3707 DEBUG_LOCKS_WARN_ON(!current->softirqs_enabled);
3708 }
3709 }
3710
3711 if (!debug_locks)
3712 print_irqtrace_events(current);
3713#endif
3714}
3715
3716void lock_set_class(struct lockdep_map *lock, const char *name,
3717 struct lock_class_key *key, unsigned int subclass,
3718 unsigned long ip)
3719{
3720 unsigned long flags;
3721
3722 if (unlikely(current->lockdep_recursion))
3723 return;
3724
3725 raw_local_irq_save(flags);
3726 current->lockdep_recursion = 1;
3727 check_flags(flags);
3728 if (__lock_set_class(lock, name, key, subclass, ip))
3729 check_chain_key(current);
3730 current->lockdep_recursion = 0;
3731 raw_local_irq_restore(flags);
3732}
3733EXPORT_SYMBOL_GPL(lock_set_class);
3734
3735/*
3736 * We are not always called with irqs disabled - do that here,
3737 * and also avoid lockdep recursion:
3738 */
3739void lock_acquire(struct lockdep_map *lock, unsigned int subclass,
3740 int trylock, int read, int check,
3741 struct lockdep_map *nest_lock, unsigned long ip)
3742{
3743 unsigned long flags;
3744
3745 if (unlikely(current->lockdep_recursion))
3746 return;
3747
3748 raw_local_irq_save(flags);
3749 check_flags(flags);
3750
3751 current->lockdep_recursion = 1;
3752 trace_lock_acquire(lock, subclass, trylock, read, check, nest_lock, ip);
3753 __lock_acquire(lock, subclass, trylock, read, check,
3754 irqs_disabled_flags(flags), nest_lock, ip, 0, 0);
3755 current->lockdep_recursion = 0;
3756 raw_local_irq_restore(flags);
3757}
3758EXPORT_SYMBOL_GPL(lock_acquire);
3759
3760void lock_release(struct lockdep_map *lock, int nested,
3761 unsigned long ip)
3762{
3763 unsigned long flags;
3764
3765 if (unlikely(current->lockdep_recursion))
3766 return;
3767
3768 raw_local_irq_save(flags);
3769 check_flags(flags);
3770 current->lockdep_recursion = 1;
3771 trace_lock_release(lock, ip);
3772 if (__lock_release(lock, nested, ip))
3773 check_chain_key(current);
3774 current->lockdep_recursion = 0;
3775 raw_local_irq_restore(flags);
3776}
3777EXPORT_SYMBOL_GPL(lock_release);
3778
3779int lock_is_held_type(struct lockdep_map *lock, int read)
3780{
3781 unsigned long flags;
3782 int ret = 0;
3783
3784 if (unlikely(current->lockdep_recursion))
3785 return 1; /* avoid false negative lockdep_assert_held() */
3786
3787 raw_local_irq_save(flags);
3788 check_flags(flags);
3789
3790 current->lockdep_recursion = 1;
3791 ret = __lock_is_held(lock, read);
3792 current->lockdep_recursion = 0;
3793 raw_local_irq_restore(flags);
3794
3795 return ret;
3796}
3797EXPORT_SYMBOL_GPL(lock_is_held_type);
3798
3799struct pin_cookie lock_pin_lock(struct lockdep_map *lock)
3800{
3801 struct pin_cookie cookie = NIL_COOKIE;
3802 unsigned long flags;
3803
3804 if (unlikely(current->lockdep_recursion))
3805 return cookie;
3806
3807 raw_local_irq_save(flags);
3808 check_flags(flags);
3809
3810 current->lockdep_recursion = 1;
3811 cookie = __lock_pin_lock(lock);
3812 current->lockdep_recursion = 0;
3813 raw_local_irq_restore(flags);
3814
3815 return cookie;
3816}
3817EXPORT_SYMBOL_GPL(lock_pin_lock);
3818
3819void lock_repin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
3820{
3821 unsigned long flags;
3822
3823 if (unlikely(current->lockdep_recursion))
3824 return;
3825
3826 raw_local_irq_save(flags);
3827 check_flags(flags);
3828
3829 current->lockdep_recursion = 1;
3830 __lock_repin_lock(lock, cookie);
3831 current->lockdep_recursion = 0;
3832 raw_local_irq_restore(flags);
3833}
3834EXPORT_SYMBOL_GPL(lock_repin_lock);
3835
3836void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
3837{
3838 unsigned long flags;
3839
3840 if (unlikely(current->lockdep_recursion))
3841 return;
3842
3843 raw_local_irq_save(flags);
3844 check_flags(flags);
3845
3846 current->lockdep_recursion = 1;
3847 __lock_unpin_lock(lock, cookie);
3848 current->lockdep_recursion = 0;
3849 raw_local_irq_restore(flags);
3850}
3851EXPORT_SYMBOL_GPL(lock_unpin_lock);
3852
3853void lockdep_set_current_reclaim_state(gfp_t gfp_mask)
3854{
3855 current->lockdep_reclaim_gfp = gfp_mask;
3856}
3857
3858void lockdep_clear_current_reclaim_state(void)
3859{
3860 current->lockdep_reclaim_gfp = 0;
3861}
3862
3863#ifdef CONFIG_LOCK_STAT
3864static int
3865print_lock_contention_bug(struct task_struct *curr, struct lockdep_map *lock,
3866 unsigned long ip)
3867{
3868 if (!debug_locks_off())
3869 return 0;
3870 if (debug_locks_silent)
3871 return 0;
3872
3873 printk("\n");
3874 printk("=================================\n");
3875 printk("[ BUG: bad contention detected! ]\n");
3876 print_kernel_ident();
3877 printk("---------------------------------\n");
3878 printk("%s/%d is trying to contend lock (",
3879 curr->comm, task_pid_nr(curr));
3880 print_lockdep_cache(lock);
3881 printk(KERN_CONT ") at:\n");
3882 print_ip_sym(ip);
3883 printk("but there are no locks held!\n");
3884 printk("\nother info that might help us debug this:\n");
3885 lockdep_print_held_locks(curr);
3886
3887 printk("\nstack backtrace:\n");
3888 dump_stack();
3889
3890 return 0;
3891}
3892
3893static void
3894__lock_contended(struct lockdep_map *lock, unsigned long ip)
3895{
3896 struct task_struct *curr = current;
3897 struct held_lock *hlock, *prev_hlock;
3898 struct lock_class_stats *stats;
3899 unsigned int depth;
3900 int i, contention_point, contending_point;
3901
3902 depth = curr->lockdep_depth;
3903 /*
3904 * Whee, we contended on this lock, except it seems we're not
3905 * actually trying to acquire anything much at all..
3906 */
3907 if (DEBUG_LOCKS_WARN_ON(!depth))
3908 return;
3909
3910 prev_hlock = NULL;
3911 for (i = depth-1; i >= 0; i--) {
3912 hlock = curr->held_locks + i;
3913 /*
3914 * We must not cross into another context:
3915 */
3916 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
3917 break;
3918 if (match_held_lock(hlock, lock))
3919 goto found_it;
3920 prev_hlock = hlock;
3921 }
3922 print_lock_contention_bug(curr, lock, ip);
3923 return;
3924
3925found_it:
3926 if (hlock->instance != lock)
3927 return;
3928
3929 hlock->waittime_stamp = lockstat_clock();
3930
3931 contention_point = lock_point(hlock_class(hlock)->contention_point, ip);
3932 contending_point = lock_point(hlock_class(hlock)->contending_point,
3933 lock->ip);
3934
3935 stats = get_lock_stats(hlock_class(hlock));
3936 if (contention_point < LOCKSTAT_POINTS)
3937 stats->contention_point[contention_point]++;
3938 if (contending_point < LOCKSTAT_POINTS)
3939 stats->contending_point[contending_point]++;
3940 if (lock->cpu != smp_processor_id())
3941 stats->bounces[bounce_contended + !!hlock->read]++;
3942 put_lock_stats(stats);
3943}
3944
3945static void
3946__lock_acquired(struct lockdep_map *lock, unsigned long ip)
3947{
3948 struct task_struct *curr = current;
3949 struct held_lock *hlock, *prev_hlock;
3950 struct lock_class_stats *stats;
3951 unsigned int depth;
3952 u64 now, waittime = 0;
3953 int i, cpu;
3954
3955 depth = curr->lockdep_depth;
3956 /*
3957 * Yay, we acquired ownership of this lock we didn't try to
3958 * acquire, how the heck did that happen?
3959 */
3960 if (DEBUG_LOCKS_WARN_ON(!depth))
3961 return;
3962
3963 prev_hlock = NULL;
3964 for (i = depth-1; i >= 0; i--) {
3965 hlock = curr->held_locks + i;
3966 /*
3967 * We must not cross into another context:
3968 */
3969 if (prev_hlock && prev_hlock->irq_context != hlock->irq_context)
3970 break;
3971 if (match_held_lock(hlock, lock))
3972 goto found_it;
3973 prev_hlock = hlock;
3974 }
3975 print_lock_contention_bug(curr, lock, _RET_IP_);
3976 return;
3977
3978found_it:
3979 if (hlock->instance != lock)
3980 return;
3981
3982 cpu = smp_processor_id();
3983 if (hlock->waittime_stamp) {
3984 now = lockstat_clock();
3985 waittime = now - hlock->waittime_stamp;
3986 hlock->holdtime_stamp = now;
3987 }
3988
3989 trace_lock_acquired(lock, ip);
3990
3991 stats = get_lock_stats(hlock_class(hlock));
3992 if (waittime) {
3993 if (hlock->read)
3994 lock_time_inc(&stats->read_waittime, waittime);
3995 else
3996 lock_time_inc(&stats->write_waittime, waittime);
3997 }
3998 if (lock->cpu != cpu)
3999 stats->bounces[bounce_acquired + !!hlock->read]++;
4000 put_lock_stats(stats);
4001
4002 lock->cpu = cpu;
4003 lock->ip = ip;
4004}
4005
4006void lock_contended(struct lockdep_map *lock, unsigned long ip)
4007{
4008 unsigned long flags;
4009
4010 if (unlikely(!lock_stat))
4011 return;
4012
4013 if (unlikely(current->lockdep_recursion))
4014 return;
4015
4016 raw_local_irq_save(flags);
4017 check_flags(flags);
4018 current->lockdep_recursion = 1;
4019 trace_lock_contended(lock, ip);
4020 __lock_contended(lock, ip);
4021 current->lockdep_recursion = 0;
4022 raw_local_irq_restore(flags);
4023}
4024EXPORT_SYMBOL_GPL(lock_contended);
4025
4026void lock_acquired(struct lockdep_map *lock, unsigned long ip)
4027{
4028 unsigned long flags;
4029
4030 if (unlikely(!lock_stat))
4031 return;
4032
4033 if (unlikely(current->lockdep_recursion))
4034 return;
4035
4036 raw_local_irq_save(flags);
4037 check_flags(flags);
4038 current->lockdep_recursion = 1;
4039 __lock_acquired(lock, ip);
4040 current->lockdep_recursion = 0;
4041 raw_local_irq_restore(flags);
4042}
4043EXPORT_SYMBOL_GPL(lock_acquired);
4044#endif
4045
4046/*
4047 * Used by the testsuite, sanitize the validator state
4048 * after a simulated failure:
4049 */
4050
4051void lockdep_reset(void)
4052{
4053 unsigned long flags;
4054 int i;
4055
4056 raw_local_irq_save(flags);
4057 current->curr_chain_key = 0;
4058 current->lockdep_depth = 0;
4059 current->lockdep_recursion = 0;
4060 memset(current->held_locks, 0, MAX_LOCK_DEPTH*sizeof(struct held_lock));
4061 nr_hardirq_chains = 0;
4062 nr_softirq_chains = 0;
4063 nr_process_chains = 0;
4064 debug_locks = 1;
4065 for (i = 0; i < CHAINHASH_SIZE; i++)
4066 INIT_HLIST_HEAD(chainhash_table + i);
4067 raw_local_irq_restore(flags);
4068}
4069
4070static void zap_class(struct lock_class *class)
4071{
4072 int i;
4073
4074 /*
4075 * Remove all dependencies this lock is
4076 * involved in:
4077 */
4078 for (i = 0; i < nr_list_entries; i++) {
4079 if (list_entries[i].class == class)
4080 list_del_rcu(&list_entries[i].entry);
4081 }
4082 /*
4083 * Unhash the class and remove it from the all_lock_classes list:
4084 */
4085 hlist_del_rcu(&class->hash_entry);
4086 list_del_rcu(&class->lock_entry);
4087
4088 RCU_INIT_POINTER(class->key, NULL);
4089 RCU_INIT_POINTER(class->name, NULL);
4090}
4091
4092static inline int within(const void *addr, void *start, unsigned long size)
4093{
4094 return addr >= start && addr < start + size;
4095}
4096
4097/*
4098 * Used in module.c to remove lock classes from memory that is going to be
4099 * freed; and possibly re-used by other modules.
4100 *
4101 * We will have had one sync_sched() before getting here, so we're guaranteed
4102 * nobody will look up these exact classes -- they're properly dead but still
4103 * allocated.
4104 */
4105void lockdep_free_key_range(void *start, unsigned long size)
4106{
4107 struct lock_class *class;
4108 struct hlist_head *head;
4109 unsigned long flags;
4110 int i;
4111 int locked;
4112
4113 raw_local_irq_save(flags);
4114 locked = graph_lock();
4115
4116 /*
4117 * Unhash all classes that were created by this module:
4118 */
4119 for (i = 0; i < CLASSHASH_SIZE; i++) {
4120 head = classhash_table + i;
4121 hlist_for_each_entry_rcu(class, head, hash_entry) {
4122 if (within(class->key, start, size))
4123 zap_class(class);
4124 else if (within(class->name, start, size))
4125 zap_class(class);
4126 }
4127 }
4128
4129 if (locked)
4130 graph_unlock();
4131 raw_local_irq_restore(flags);
4132
4133 /*
4134 * Wait for any possible iterators from look_up_lock_class() to pass
4135 * before continuing to free the memory they refer to.
4136 *
4137 * sync_sched() is sufficient because the read-side is IRQ disable.
4138 */
4139 synchronize_sched();
4140
4141 /*
4142 * XXX at this point we could return the resources to the pool;
4143 * instead we leak them. We would need to change to bitmap allocators
4144 * instead of the linear allocators we have now.
4145 */
4146}
4147
4148void lockdep_reset_lock(struct lockdep_map *lock)
4149{
4150 struct lock_class *class;
4151 struct hlist_head *head;
4152 unsigned long flags;
4153 int i, j;
4154 int locked;
4155
4156 raw_local_irq_save(flags);
4157
4158 /*
4159 * Remove all classes this lock might have:
4160 */
4161 for (j = 0; j < MAX_LOCKDEP_SUBCLASSES; j++) {
4162 /*
4163 * If the class exists we look it up and zap it:
4164 */
4165 class = look_up_lock_class(lock, j);
4166 if (class)
4167 zap_class(class);
4168 }
4169 /*
4170 * Debug check: in the end all mapped classes should
4171 * be gone.
4172 */
4173 locked = graph_lock();
4174 for (i = 0; i < CLASSHASH_SIZE; i++) {
4175 head = classhash_table + i;
4176 hlist_for_each_entry_rcu(class, head, hash_entry) {
4177 int match = 0;
4178
4179 for (j = 0; j < NR_LOCKDEP_CACHING_CLASSES; j++)
4180 match |= class == lock->class_cache[j];
4181
4182 if (unlikely(match)) {
4183 if (debug_locks_off_graph_unlock()) {
4184 /*
4185 * We all just reset everything, how did it match?
4186 */
4187 WARN_ON(1);
4188 }
4189 goto out_restore;
4190 }
4191 }
4192 }
4193 if (locked)
4194 graph_unlock();
4195
4196out_restore:
4197 raw_local_irq_restore(flags);
4198}
4199
4200void __init lockdep_info(void)
4201{
4202 printk("Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar\n");
4203
4204 printk("... MAX_LOCKDEP_SUBCLASSES: %lu\n", MAX_LOCKDEP_SUBCLASSES);
4205 printk("... MAX_LOCK_DEPTH: %lu\n", MAX_LOCK_DEPTH);
4206 printk("... MAX_LOCKDEP_KEYS: %lu\n", MAX_LOCKDEP_KEYS);
4207 printk("... CLASSHASH_SIZE: %lu\n", CLASSHASH_SIZE);
4208 printk("... MAX_LOCKDEP_ENTRIES: %lu\n", MAX_LOCKDEP_ENTRIES);
4209 printk("... MAX_LOCKDEP_CHAINS: %lu\n", MAX_LOCKDEP_CHAINS);
4210 printk("... CHAINHASH_SIZE: %lu\n", CHAINHASH_SIZE);
4211
4212 printk(" memory used by lock dependency info: %lu kB\n",
4213 (sizeof(struct lock_class) * MAX_LOCKDEP_KEYS +
4214 sizeof(struct list_head) * CLASSHASH_SIZE +
4215 sizeof(struct lock_list) * MAX_LOCKDEP_ENTRIES +
4216 sizeof(struct lock_chain) * MAX_LOCKDEP_CHAINS +
4217 sizeof(struct list_head) * CHAINHASH_SIZE
4218#ifdef CONFIG_PROVE_LOCKING
4219 + sizeof(struct circular_queue)
4220#endif
4221 ) / 1024
4222 );
4223
4224 printk(" per task-struct memory footprint: %lu bytes\n",
4225 sizeof(struct held_lock) * MAX_LOCK_DEPTH);
4226}
4227
4228static void
4229print_freed_lock_bug(struct task_struct *curr, const void *mem_from,
4230 const void *mem_to, struct held_lock *hlock)
4231{
4232 if (!debug_locks_off())
4233 return;
4234 if (debug_locks_silent)
4235 return;
4236
4237 printk("\n");
4238 printk("=========================\n");
4239 printk("[ BUG: held lock freed! ]\n");
4240 print_kernel_ident();
4241 printk("-------------------------\n");
4242 printk("%s/%d is freeing memory %p-%p, with a lock still held there!\n",
4243 curr->comm, task_pid_nr(curr), mem_from, mem_to-1);
4244 print_lock(hlock);
4245 lockdep_print_held_locks(curr);
4246
4247 printk("\nstack backtrace:\n");
4248 dump_stack();
4249}
4250
4251static inline int not_in_range(const void* mem_from, unsigned long mem_len,
4252 const void* lock_from, unsigned long lock_len)
4253{
4254 return lock_from + lock_len <= mem_from ||
4255 mem_from + mem_len <= lock_from;
4256}
4257
4258/*
4259 * Called when kernel memory is freed (or unmapped), or if a lock
4260 * is destroyed or reinitialized - this code checks whether there is
4261 * any held lock in the memory range of <from> to <to>:
4262 */
4263void debug_check_no_locks_freed(const void *mem_from, unsigned long mem_len)
4264{
4265 struct task_struct *curr = current;
4266 struct held_lock *hlock;
4267 unsigned long flags;
4268 int i;
4269
4270 if (unlikely(!debug_locks))
4271 return;
4272
4273 local_irq_save(flags);
4274 for (i = 0; i < curr->lockdep_depth; i++) {
4275 hlock = curr->held_locks + i;
4276
4277 if (not_in_range(mem_from, mem_len, hlock->instance,
4278 sizeof(*hlock->instance)))
4279 continue;
4280
4281 print_freed_lock_bug(curr, mem_from, mem_from + mem_len, hlock);
4282 break;
4283 }
4284 local_irq_restore(flags);
4285}
4286EXPORT_SYMBOL_GPL(debug_check_no_locks_freed);
4287
4288static void print_held_locks_bug(void)
4289{
4290 if (!debug_locks_off())
4291 return;
4292 if (debug_locks_silent)
4293 return;
4294
4295 printk("\n");
4296 printk("=====================================\n");
4297 printk("[ BUG: %s/%d still has locks held! ]\n",
4298 current->comm, task_pid_nr(current));
4299 print_kernel_ident();
4300 printk("-------------------------------------\n");
4301 lockdep_print_held_locks(current);
4302 printk("\nstack backtrace:\n");
4303 dump_stack();
4304}
4305
4306void debug_check_no_locks_held(void)
4307{
4308 if (unlikely(current->lockdep_depth > 0))
4309 print_held_locks_bug();
4310}
4311EXPORT_SYMBOL_GPL(debug_check_no_locks_held);
4312
4313#ifdef __KERNEL__
4314void debug_show_all_locks(void)
4315{
4316 struct task_struct *g, *p;
4317 int count = 10;
4318 int unlock = 1;
4319
4320 if (unlikely(!debug_locks)) {
4321 printk("INFO: lockdep is turned off.\n");
4322 return;
4323 }
4324 printk("\nShowing all locks held in the system:\n");
4325
4326 /*
4327 * Here we try to get the tasklist_lock as hard as possible,
4328 * if not successful after 2 seconds we ignore it (but keep
4329 * trying). This is to enable a debug printout even if a
4330 * tasklist_lock-holding task deadlocks or crashes.
4331 */
4332retry:
4333 if (!read_trylock(&tasklist_lock)) {
4334 if (count == 10)
4335 printk("hm, tasklist_lock locked, retrying... ");
4336 if (count) {
4337 count--;
4338 printk(" #%d", 10-count);
4339 mdelay(200);
4340 goto retry;
4341 }
4342 printk(" ignoring it.\n");
4343 unlock = 0;
4344 } else {
4345 if (count != 10)
4346 printk(KERN_CONT " locked it.\n");
4347 }
4348
4349 do_each_thread(g, p) {
4350 /*
4351 * It's not reliable to print a task's held locks
4352 * if it's not sleeping (or if it's not the current
4353 * task):
4354 */
4355 if (p->state == TASK_RUNNING && p != current)
4356 continue;
4357 if (p->lockdep_depth)
4358 lockdep_print_held_locks(p);
4359 if (!unlock)
4360 if (read_trylock(&tasklist_lock))
4361 unlock = 1;
4362 } while_each_thread(g, p);
4363
4364 printk("\n");
4365 printk("=============================================\n\n");
4366
4367 if (unlock)
4368 read_unlock(&tasklist_lock);
4369}
4370EXPORT_SYMBOL_GPL(debug_show_all_locks);
4371#endif
4372
4373/*
4374 * Careful: only use this function if you are sure that
4375 * the task cannot run in parallel!
4376 */
4377void debug_show_held_locks(struct task_struct *task)
4378{
4379 if (unlikely(!debug_locks)) {
4380 printk("INFO: lockdep is turned off.\n");
4381 return;
4382 }
4383 lockdep_print_held_locks(task);
4384}
4385EXPORT_SYMBOL_GPL(debug_show_held_locks);
4386
4387asmlinkage __visible void lockdep_sys_exit(void)
4388{
4389 struct task_struct *curr = current;
4390
4391 if (unlikely(curr->lockdep_depth)) {
4392 if (!debug_locks_off())
4393 return;
4394 printk("\n");
4395 printk("================================================\n");
4396 printk("[ BUG: lock held when returning to user space! ]\n");
4397 print_kernel_ident();
4398 printk("------------------------------------------------\n");
4399 printk("%s/%d is leaving the kernel with locks still held!\n",
4400 curr->comm, curr->pid);
4401 lockdep_print_held_locks(curr);
4402 }
4403}
4404
4405void lockdep_rcu_suspicious(const char *file, const int line, const char *s)
4406{
4407 struct task_struct *curr = current;
4408
4409#ifndef CONFIG_PROVE_RCU_REPEATEDLY
4410 if (!debug_locks_off())
4411 return;
4412#endif /* #ifdef CONFIG_PROVE_RCU_REPEATEDLY */
4413 /* Note: the following can be executed concurrently, so be careful. */
4414 printk("\n");
4415 printk("===============================\n");
4416 printk("[ INFO: suspicious RCU usage. ]\n");
4417 print_kernel_ident();
4418 printk("-------------------------------\n");
4419 printk("%s:%d %s!\n", file, line, s);
4420 printk("\nother info that might help us debug this:\n\n");
4421 printk("\n%srcu_scheduler_active = %d, debug_locks = %d\n",
4422 !rcu_lockdep_current_cpu_online()
4423 ? "RCU used illegally from offline CPU!\n"
4424 : !rcu_is_watching()
4425 ? "RCU used illegally from idle CPU!\n"
4426 : "",
4427 rcu_scheduler_active, debug_locks);
4428
4429 /*
4430 * If a CPU is in the RCU-free window in idle (ie: in the section
4431 * between rcu_idle_enter() and rcu_idle_exit(), then RCU
4432 * considers that CPU to be in an "extended quiescent state",
4433 * which means that RCU will be completely ignoring that CPU.
4434 * Therefore, rcu_read_lock() and friends have absolutely no
4435 * effect on a CPU running in that state. In other words, even if
4436 * such an RCU-idle CPU has called rcu_read_lock(), RCU might well
4437 * delete data structures out from under it. RCU really has no
4438 * choice here: we need to keep an RCU-free window in idle where
4439 * the CPU may possibly enter into low power mode. This way we can
4440 * notice an extended quiescent state to other CPUs that started a grace
4441 * period. Otherwise we would delay any grace period as long as we run
4442 * in the idle task.
4443 *
4444 * So complain bitterly if someone does call rcu_read_lock(),
4445 * rcu_read_lock_bh() and so on from extended quiescent states.
4446 */
4447 if (!rcu_is_watching())
4448 printk("RCU used illegally from extended quiescent state!\n");
4449
4450 lockdep_print_held_locks(curr);
4451 printk("\nstack backtrace:\n");
4452 dump_stack();
4453}
4454EXPORT_SYMBOL_GPL(lockdep_rcu_suspicious);
1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * kernel/lockdep.c
4 *
5 * Runtime locking correctness validator
6 *
7 * Started by Ingo Molnar:
8 *
9 * Copyright (C) 2006,2007 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
10 * Copyright (C) 2007 Red Hat, Inc., Peter Zijlstra
11 *
12 * this code maps all the lock dependencies as they occur in a live kernel
13 * and will warn about the following classes of locking bugs:
14 *
15 * - lock inversion scenarios
16 * - circular lock dependencies
17 * - hardirq/softirq safe/unsafe locking bugs
18 *
19 * Bugs are reported even if the current locking scenario does not cause
20 * any deadlock at this point.
21 *
22 * I.e. if anytime in the past two locks were taken in a different order,
23 * even if it happened for another task, even if those were different
24 * locks (but of the same class as this lock), this code will detect it.
25 *
26 * Thanks to Arjan van de Ven for coming up with the initial idea of
27 * mapping lock dependencies runtime.
28 */
29#define DISABLE_BRANCH_PROFILING
30#include <linux/mutex.h>
31#include <linux/sched.h>
32#include <linux/sched/clock.h>
33#include <linux/sched/task.h>
34#include <linux/sched/mm.h>
35#include <linux/delay.h>
36#include <linux/module.h>
37#include <linux/proc_fs.h>
38#include <linux/seq_file.h>
39#include <linux/spinlock.h>
40#include <linux/kallsyms.h>
41#include <linux/interrupt.h>
42#include <linux/stacktrace.h>
43#include <linux/debug_locks.h>
44#include <linux/irqflags.h>
45#include <linux/utsname.h>
46#include <linux/hash.h>
47#include <linux/ftrace.h>
48#include <linux/stringify.h>
49#include <linux/bitmap.h>
50#include <linux/bitops.h>
51#include <linux/gfp.h>
52#include <linux/random.h>
53#include <linux/jhash.h>
54#include <linux/nmi.h>
55#include <linux/rcupdate.h>
56#include <linux/kprobes.h>
57#include <linux/lockdep.h>
58
59#include <asm/sections.h>
60
61#include "lockdep_internals.h"
62
63#define CREATE_TRACE_POINTS
64#include <trace/events/lock.h>
65
66#ifdef CONFIG_PROVE_LOCKING
67int prove_locking = 1;
68module_param(prove_locking, int, 0644);
69#else
70#define prove_locking 0
71#endif
72
73#ifdef CONFIG_LOCK_STAT
74int lock_stat = 1;
75module_param(lock_stat, int, 0644);
76#else
77#define lock_stat 0
78#endif
79
80DEFINE_PER_CPU(unsigned int, lockdep_recursion);
81EXPORT_PER_CPU_SYMBOL_GPL(lockdep_recursion);
82
83static __always_inline bool lockdep_enabled(void)
84{
85 if (!debug_locks)
86 return false;
87
88 if (this_cpu_read(lockdep_recursion))
89 return false;
90
91 if (current->lockdep_recursion)
92 return false;
93
94 return true;
95}
96
97/*
98 * lockdep_lock: protects the lockdep graph, the hashes and the
99 * class/list/hash allocators.
100 *
101 * This is one of the rare exceptions where it's justified
102 * to use a raw spinlock - we really dont want the spinlock
103 * code to recurse back into the lockdep code...
104 */
105static arch_spinlock_t __lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
106static struct task_struct *__owner;
107
108static inline void lockdep_lock(void)
109{
110 DEBUG_LOCKS_WARN_ON(!irqs_disabled());
111
112 __this_cpu_inc(lockdep_recursion);
113 arch_spin_lock(&__lock);
114 __owner = current;
115}
116
117static inline void lockdep_unlock(void)
118{
119 DEBUG_LOCKS_WARN_ON(!irqs_disabled());
120
121 if (debug_locks && DEBUG_LOCKS_WARN_ON(__owner != current))
122 return;
123
124 __owner = NULL;
125 arch_spin_unlock(&__lock);
126 __this_cpu_dec(lockdep_recursion);
127}
128
129static inline bool lockdep_assert_locked(void)
130{
131 return DEBUG_LOCKS_WARN_ON(__owner != current);
132}
133
134static struct task_struct *lockdep_selftest_task_struct;
135
136
137static int graph_lock(void)
138{
139 lockdep_lock();
140 /*
141 * Make sure that if another CPU detected a bug while
142 * walking the graph we dont change it (while the other
143 * CPU is busy printing out stuff with the graph lock
144 * dropped already)
145 */
146 if (!debug_locks) {
147 lockdep_unlock();
148 return 0;
149 }
150 return 1;
151}
152
153static inline void graph_unlock(void)
154{
155 lockdep_unlock();
156}
157
158/*
159 * Turn lock debugging off and return with 0 if it was off already,
160 * and also release the graph lock:
161 */
162static inline int debug_locks_off_graph_unlock(void)
163{
164 int ret = debug_locks_off();
165
166 lockdep_unlock();
167
168 return ret;
169}
170
171unsigned long nr_list_entries;
172static struct lock_list list_entries[MAX_LOCKDEP_ENTRIES];
173static DECLARE_BITMAP(list_entries_in_use, MAX_LOCKDEP_ENTRIES);
174
175/*
176 * All data structures here are protected by the global debug_lock.
177 *
178 * nr_lock_classes is the number of elements of lock_classes[] that is
179 * in use.
180 */
181#define KEYHASH_BITS (MAX_LOCKDEP_KEYS_BITS - 1)
182#define KEYHASH_SIZE (1UL << KEYHASH_BITS)
183static struct hlist_head lock_keys_hash[KEYHASH_SIZE];
184unsigned long nr_lock_classes;
185unsigned long nr_zapped_classes;
186#ifndef CONFIG_DEBUG_LOCKDEP
187static
188#endif
189struct lock_class lock_classes[MAX_LOCKDEP_KEYS];
190static DECLARE_BITMAP(lock_classes_in_use, MAX_LOCKDEP_KEYS);
191
192static inline struct lock_class *hlock_class(struct held_lock *hlock)
193{
194 unsigned int class_idx = hlock->class_idx;
195
196 /* Don't re-read hlock->class_idx, can't use READ_ONCE() on bitfield */
197 barrier();
198
199 if (!test_bit(class_idx, lock_classes_in_use)) {
200 /*
201 * Someone passed in garbage, we give up.
202 */
203 DEBUG_LOCKS_WARN_ON(1);
204 return NULL;
205 }
206
207 /*
208 * At this point, if the passed hlock->class_idx is still garbage,
209 * we just have to live with it
210 */
211 return lock_classes + class_idx;
212}
213
214#ifdef CONFIG_LOCK_STAT
215static DEFINE_PER_CPU(struct lock_class_stats[MAX_LOCKDEP_KEYS], cpu_lock_stats);
216
217static inline u64 lockstat_clock(void)
218{
219 return local_clock();
220}
221
222static int lock_point(unsigned long points[], unsigned long ip)
223{
224 int i;
225
226 for (i = 0; i < LOCKSTAT_POINTS; i++) {
227 if (points[i] == 0) {
228 points[i] = ip;
229 break;
230 }
231 if (points[i] == ip)
232 break;
233 }
234
235 return i;
236}
237
238static void lock_time_inc(struct lock_time *lt, u64 time)
239{
240 if (time > lt->max)
241 lt->max = time;
242
243 if (time < lt->min || !lt->nr)
244 lt->min = time;
245
246 lt->total += time;
247 lt->nr++;
248}
249
250static inline void lock_time_add(struct lock_time *src, struct lock_time *dst)
251{
252 if (!src->nr)
253 return;
254
255 if (src->max > dst->max)
256 dst->max = src->max;
257
258 if (src->min < dst->min || !dst->nr)
259 dst->min = src->min;
260
261 dst->total += src->total;
262 dst->nr += src->nr;
263}
264
265struct lock_class_stats lock_stats(struct lock_class *class)
266{
267 struct lock_class_stats stats;
268 int cpu, i;
269
270 memset(&stats, 0, sizeof(struct lock_class_stats));
271 for_each_possible_cpu(cpu) {
272 struct lock_class_stats *pcs =
273 &per_cpu(cpu_lock_stats, cpu)[class - lock_classes];
274
275 for (i = 0; i < ARRAY_SIZE(stats.contention_point); i++)
276 stats.contention_point[i] += pcs->contention_point[i];
277
278 for (i = 0; i < ARRAY_SIZE(stats.contending_point); i++)
279 stats.contending_point[i] += pcs->contending_point[i];
280
281 lock_time_add(&pcs->read_waittime, &stats.read_waittime);
282 lock_time_add(&pcs->write_waittime, &stats.write_waittime);
283
284 lock_time_add(&pcs->read_holdtime, &stats.read_holdtime);
285 lock_time_add(&pcs->write_holdtime, &stats.write_holdtime);
286
287 for (i = 0; i < ARRAY_SIZE(stats.bounces); i++)
288 stats.bounces[i] += pcs->bounces[i];
289 }
290
291 return stats;
292}
293
294void clear_lock_stats(struct lock_class *class)
295{
296 int cpu;
297
298 for_each_possible_cpu(cpu) {
299 struct lock_class_stats *cpu_stats =
300 &per_cpu(cpu_lock_stats, cpu)[class - lock_classes];
301
302 memset(cpu_stats, 0, sizeof(struct lock_class_stats));
303 }
304 memset(class->contention_point, 0, sizeof(class->contention_point));
305 memset(class->contending_point, 0, sizeof(class->contending_point));
306}
307
308static struct lock_class_stats *get_lock_stats(struct lock_class *class)
309{
310 return &this_cpu_ptr(cpu_lock_stats)[class - lock_classes];
311}
312
313static void lock_release_holdtime(struct held_lock *hlock)
314{
315 struct lock_class_stats *stats;
316 u64 holdtime;
317
318 if (!lock_stat)
319 return;
320
321 holdtime = lockstat_clock() - hlock->holdtime_stamp;
322
323 stats = get_lock_stats(hlock_class(hlock));
324 if (hlock->read)
325 lock_time_inc(&stats->read_holdtime, holdtime);
326 else
327 lock_time_inc(&stats->write_holdtime, holdtime);
328}
329#else
330static inline void lock_release_holdtime(struct held_lock *hlock)
331{
332}
333#endif
334
335/*
336 * We keep a global list of all lock classes. The list is only accessed with
337 * the lockdep spinlock lock held. free_lock_classes is a list with free
338 * elements. These elements are linked together by the lock_entry member in
339 * struct lock_class.
340 */
341LIST_HEAD(all_lock_classes);
342static LIST_HEAD(free_lock_classes);
343
344/**
345 * struct pending_free - information about data structures about to be freed
346 * @zapped: Head of a list with struct lock_class elements.
347 * @lock_chains_being_freed: Bitmap that indicates which lock_chains[] elements
348 * are about to be freed.
349 */
350struct pending_free {
351 struct list_head zapped;
352 DECLARE_BITMAP(lock_chains_being_freed, MAX_LOCKDEP_CHAINS);
353};
354
355/**
356 * struct delayed_free - data structures used for delayed freeing
357 *
358 * A data structure for delayed freeing of data structures that may be
359 * accessed by RCU readers at the time these were freed.
360 *
361 * @rcu_head: Used to schedule an RCU callback for freeing data structures.
362 * @index: Index of @pf to which freed data structures are added.
363 * @scheduled: Whether or not an RCU callback has been scheduled.
364 * @pf: Array with information about data structures about to be freed.
365 */
366static struct delayed_free {
367 struct rcu_head rcu_head;
368 int index;
369 int scheduled;
370 struct pending_free pf[2];
371} delayed_free;
372
373/*
374 * The lockdep classes are in a hash-table as well, for fast lookup:
375 */
376#define CLASSHASH_BITS (MAX_LOCKDEP_KEYS_BITS - 1)
377#define CLASSHASH_SIZE (1UL << CLASSHASH_BITS)
378#define __classhashfn(key) hash_long((unsigned long)key, CLASSHASH_BITS)
379#define classhashentry(key) (classhash_table + __classhashfn((key)))
380
381static struct hlist_head classhash_table[CLASSHASH_SIZE];
382
383/*
384 * We put the lock dependency chains into a hash-table as well, to cache
385 * their existence:
386 */
387#define CHAINHASH_BITS (MAX_LOCKDEP_CHAINS_BITS-1)
388#define CHAINHASH_SIZE (1UL << CHAINHASH_BITS)
389#define __chainhashfn(chain) hash_long(chain, CHAINHASH_BITS)
390#define chainhashentry(chain) (chainhash_table + __chainhashfn((chain)))
391
392static struct hlist_head chainhash_table[CHAINHASH_SIZE];
393
394/*
395 * the id of held_lock
396 */
397static inline u16 hlock_id(struct held_lock *hlock)
398{
399 BUILD_BUG_ON(MAX_LOCKDEP_KEYS_BITS + 2 > 16);
400
401 return (hlock->class_idx | (hlock->read << MAX_LOCKDEP_KEYS_BITS));
402}
403
404static inline unsigned int chain_hlock_class_idx(u16 hlock_id)
405{
406 return hlock_id & (MAX_LOCKDEP_KEYS - 1);
407}
408
409/*
410 * The hash key of the lock dependency chains is a hash itself too:
411 * it's a hash of all locks taken up to that lock, including that lock.
412 * It's a 64-bit hash, because it's important for the keys to be
413 * unique.
414 */
415static inline u64 iterate_chain_key(u64 key, u32 idx)
416{
417 u32 k0 = key, k1 = key >> 32;
418
419 __jhash_mix(idx, k0, k1); /* Macro that modifies arguments! */
420
421 return k0 | (u64)k1 << 32;
422}
423
424void lockdep_init_task(struct task_struct *task)
425{
426 task->lockdep_depth = 0; /* no locks held yet */
427 task->curr_chain_key = INITIAL_CHAIN_KEY;
428 task->lockdep_recursion = 0;
429}
430
431static __always_inline void lockdep_recursion_inc(void)
432{
433 __this_cpu_inc(lockdep_recursion);
434}
435
436static __always_inline void lockdep_recursion_finish(void)
437{
438 if (WARN_ON_ONCE(__this_cpu_dec_return(lockdep_recursion)))
439 __this_cpu_write(lockdep_recursion, 0);
440}
441
442void lockdep_set_selftest_task(struct task_struct *task)
443{
444 lockdep_selftest_task_struct = task;
445}
446
447/*
448 * Debugging switches:
449 */
450
451#define VERBOSE 0
452#define VERY_VERBOSE 0
453
454#if VERBOSE
455# define HARDIRQ_VERBOSE 1
456# define SOFTIRQ_VERBOSE 1
457#else
458# define HARDIRQ_VERBOSE 0
459# define SOFTIRQ_VERBOSE 0
460#endif
461
462#if VERBOSE || HARDIRQ_VERBOSE || SOFTIRQ_VERBOSE
463/*
464 * Quick filtering for interesting events:
465 */
466static int class_filter(struct lock_class *class)
467{
468#if 0
469 /* Example */
470 if (class->name_version == 1 &&
471 !strcmp(class->name, "lockname"))
472 return 1;
473 if (class->name_version == 1 &&
474 !strcmp(class->name, "&struct->lockfield"))
475 return 1;
476#endif
477 /* Filter everything else. 1 would be to allow everything else */
478 return 0;
479}
480#endif
481
482static int verbose(struct lock_class *class)
483{
484#if VERBOSE
485 return class_filter(class);
486#endif
487 return 0;
488}
489
490static void print_lockdep_off(const char *bug_msg)
491{
492 printk(KERN_DEBUG "%s\n", bug_msg);
493 printk(KERN_DEBUG "turning off the locking correctness validator.\n");
494#ifdef CONFIG_LOCK_STAT
495 printk(KERN_DEBUG "Please attach the output of /proc/lock_stat to the bug report\n");
496#endif
497}
498
499unsigned long nr_stack_trace_entries;
500
501#ifdef CONFIG_PROVE_LOCKING
502/**
503 * struct lock_trace - single stack backtrace
504 * @hash_entry: Entry in a stack_trace_hash[] list.
505 * @hash: jhash() of @entries.
506 * @nr_entries: Number of entries in @entries.
507 * @entries: Actual stack backtrace.
508 */
509struct lock_trace {
510 struct hlist_node hash_entry;
511 u32 hash;
512 u32 nr_entries;
513 unsigned long entries[] __aligned(sizeof(unsigned long));
514};
515#define LOCK_TRACE_SIZE_IN_LONGS \
516 (sizeof(struct lock_trace) / sizeof(unsigned long))
517/*
518 * Stack-trace: sequence of lock_trace structures. Protected by the graph_lock.
519 */
520static unsigned long stack_trace[MAX_STACK_TRACE_ENTRIES];
521static struct hlist_head stack_trace_hash[STACK_TRACE_HASH_SIZE];
522
523static bool traces_identical(struct lock_trace *t1, struct lock_trace *t2)
524{
525 return t1->hash == t2->hash && t1->nr_entries == t2->nr_entries &&
526 memcmp(t1->entries, t2->entries,
527 t1->nr_entries * sizeof(t1->entries[0])) == 0;
528}
529
530static struct lock_trace *save_trace(void)
531{
532 struct lock_trace *trace, *t2;
533 struct hlist_head *hash_head;
534 u32 hash;
535 int max_entries;
536
537 BUILD_BUG_ON_NOT_POWER_OF_2(STACK_TRACE_HASH_SIZE);
538 BUILD_BUG_ON(LOCK_TRACE_SIZE_IN_LONGS >= MAX_STACK_TRACE_ENTRIES);
539
540 trace = (struct lock_trace *)(stack_trace + nr_stack_trace_entries);
541 max_entries = MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries -
542 LOCK_TRACE_SIZE_IN_LONGS;
543
544 if (max_entries <= 0) {
545 if (!debug_locks_off_graph_unlock())
546 return NULL;
547
548 print_lockdep_off("BUG: MAX_STACK_TRACE_ENTRIES too low!");
549 dump_stack();
550
551 return NULL;
552 }
553 trace->nr_entries = stack_trace_save(trace->entries, max_entries, 3);
554
555 hash = jhash(trace->entries, trace->nr_entries *
556 sizeof(trace->entries[0]), 0);
557 trace->hash = hash;
558 hash_head = stack_trace_hash + (hash & (STACK_TRACE_HASH_SIZE - 1));
559 hlist_for_each_entry(t2, hash_head, hash_entry) {
560 if (traces_identical(trace, t2))
561 return t2;
562 }
563 nr_stack_trace_entries += LOCK_TRACE_SIZE_IN_LONGS + trace->nr_entries;
564 hlist_add_head(&trace->hash_entry, hash_head);
565
566 return trace;
567}
568
569/* Return the number of stack traces in the stack_trace[] array. */
570u64 lockdep_stack_trace_count(void)
571{
572 struct lock_trace *trace;
573 u64 c = 0;
574 int i;
575
576 for (i = 0; i < ARRAY_SIZE(stack_trace_hash); i++) {
577 hlist_for_each_entry(trace, &stack_trace_hash[i], hash_entry) {
578 c++;
579 }
580 }
581
582 return c;
583}
584
585/* Return the number of stack hash chains that have at least one stack trace. */
586u64 lockdep_stack_hash_count(void)
587{
588 u64 c = 0;
589 int i;
590
591 for (i = 0; i < ARRAY_SIZE(stack_trace_hash); i++)
592 if (!hlist_empty(&stack_trace_hash[i]))
593 c++;
594
595 return c;
596}
597#endif
598
599unsigned int nr_hardirq_chains;
600unsigned int nr_softirq_chains;
601unsigned int nr_process_chains;
602unsigned int max_lockdep_depth;
603
604#ifdef CONFIG_DEBUG_LOCKDEP
605/*
606 * Various lockdep statistics:
607 */
608DEFINE_PER_CPU(struct lockdep_stats, lockdep_stats);
609#endif
610
611#ifdef CONFIG_PROVE_LOCKING
612/*
613 * Locking printouts:
614 */
615
616#define __USAGE(__STATE) \
617 [LOCK_USED_IN_##__STATE] = "IN-"__stringify(__STATE)"-W", \
618 [LOCK_ENABLED_##__STATE] = __stringify(__STATE)"-ON-W", \
619 [LOCK_USED_IN_##__STATE##_READ] = "IN-"__stringify(__STATE)"-R",\
620 [LOCK_ENABLED_##__STATE##_READ] = __stringify(__STATE)"-ON-R",
621
622static const char *usage_str[] =
623{
624#define LOCKDEP_STATE(__STATE) __USAGE(__STATE)
625#include "lockdep_states.h"
626#undef LOCKDEP_STATE
627 [LOCK_USED] = "INITIAL USE",
628 [LOCK_USED_READ] = "INITIAL READ USE",
629 /* abused as string storage for verify_lock_unused() */
630 [LOCK_USAGE_STATES] = "IN-NMI",
631};
632#endif
633
634const char *__get_key_name(const struct lockdep_subclass_key *key, char *str)
635{
636 return kallsyms_lookup((unsigned long)key, NULL, NULL, NULL, str);
637}
638
639static inline unsigned long lock_flag(enum lock_usage_bit bit)
640{
641 return 1UL << bit;
642}
643
644static char get_usage_char(struct lock_class *class, enum lock_usage_bit bit)
645{
646 /*
647 * The usage character defaults to '.' (i.e., irqs disabled and not in
648 * irq context), which is the safest usage category.
649 */
650 char c = '.';
651
652 /*
653 * The order of the following usage checks matters, which will
654 * result in the outcome character as follows:
655 *
656 * - '+': irq is enabled and not in irq context
657 * - '-': in irq context and irq is disabled
658 * - '?': in irq context and irq is enabled
659 */
660 if (class->usage_mask & lock_flag(bit + LOCK_USAGE_DIR_MASK)) {
661 c = '+';
662 if (class->usage_mask & lock_flag(bit))
663 c = '?';
664 } else if (class->usage_mask & lock_flag(bit))
665 c = '-';
666
667 return c;
668}
669
670void get_usage_chars(struct lock_class *class, char usage[LOCK_USAGE_CHARS])
671{
672 int i = 0;
673
674#define LOCKDEP_STATE(__STATE) \
675 usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE); \
676 usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE##_READ);
677#include "lockdep_states.h"
678#undef LOCKDEP_STATE
679
680 usage[i] = '\0';
681}
682
683static void __print_lock_name(struct lock_class *class)
684{
685 char str[KSYM_NAME_LEN];
686 const char *name;
687
688 name = class->name;
689 if (!name) {
690 name = __get_key_name(class->key, str);
691 printk(KERN_CONT "%s", name);
692 } else {
693 printk(KERN_CONT "%s", name);
694 if (class->name_version > 1)
695 printk(KERN_CONT "#%d", class->name_version);
696 if (class->subclass)
697 printk(KERN_CONT "/%d", class->subclass);
698 }
699}
700
701static void print_lock_name(struct lock_class *class)
702{
703 char usage[LOCK_USAGE_CHARS];
704
705 get_usage_chars(class, usage);
706
707 printk(KERN_CONT " (");
708 __print_lock_name(class);
709 printk(KERN_CONT "){%s}-{%d:%d}", usage,
710 class->wait_type_outer ?: class->wait_type_inner,
711 class->wait_type_inner);
712}
713
714static void print_lockdep_cache(struct lockdep_map *lock)
715{
716 const char *name;
717 char str[KSYM_NAME_LEN];
718
719 name = lock->name;
720 if (!name)
721 name = __get_key_name(lock->key->subkeys, str);
722
723 printk(KERN_CONT "%s", name);
724}
725
726static void print_lock(struct held_lock *hlock)
727{
728 /*
729 * We can be called locklessly through debug_show_all_locks() so be
730 * extra careful, the hlock might have been released and cleared.
731 *
732 * If this indeed happens, lets pretend it does not hurt to continue
733 * to print the lock unless the hlock class_idx does not point to a
734 * registered class. The rationale here is: since we don't attempt
735 * to distinguish whether we are in this situation, if it just
736 * happened we can't count on class_idx to tell either.
737 */
738 struct lock_class *lock = hlock_class(hlock);
739
740 if (!lock) {
741 printk(KERN_CONT "<RELEASED>\n");
742 return;
743 }
744
745 printk(KERN_CONT "%px", hlock->instance);
746 print_lock_name(lock);
747 printk(KERN_CONT ", at: %pS\n", (void *)hlock->acquire_ip);
748}
749
750static void lockdep_print_held_locks(struct task_struct *p)
751{
752 int i, depth = READ_ONCE(p->lockdep_depth);
753
754 if (!depth)
755 printk("no locks held by %s/%d.\n", p->comm, task_pid_nr(p));
756 else
757 printk("%d lock%s held by %s/%d:\n", depth,
758 depth > 1 ? "s" : "", p->comm, task_pid_nr(p));
759 /*
760 * It's not reliable to print a task's held locks if it's not sleeping
761 * and it's not the current task.
762 */
763 if (p != current && task_is_running(p))
764 return;
765 for (i = 0; i < depth; i++) {
766 printk(" #%d: ", i);
767 print_lock(p->held_locks + i);
768 }
769}
770
771static void print_kernel_ident(void)
772{
773 printk("%s %.*s %s\n", init_utsname()->release,
774 (int)strcspn(init_utsname()->version, " "),
775 init_utsname()->version,
776 print_tainted());
777}
778
779static int very_verbose(struct lock_class *class)
780{
781#if VERY_VERBOSE
782 return class_filter(class);
783#endif
784 return 0;
785}
786
787/*
788 * Is this the address of a static object:
789 */
790#ifdef __KERNEL__
791static int static_obj(const void *obj)
792{
793 unsigned long start = (unsigned long) &_stext,
794 end = (unsigned long) &_end,
795 addr = (unsigned long) obj;
796
797 if (arch_is_kernel_initmem_freed(addr))
798 return 0;
799
800 /*
801 * static variable?
802 */
803 if ((addr >= start) && (addr < end))
804 return 1;
805
806 if (arch_is_kernel_data(addr))
807 return 1;
808
809 /*
810 * in-kernel percpu var?
811 */
812 if (is_kernel_percpu_address(addr))
813 return 1;
814
815 /*
816 * module static or percpu var?
817 */
818 return is_module_address(addr) || is_module_percpu_address(addr);
819}
820#endif
821
822/*
823 * To make lock name printouts unique, we calculate a unique
824 * class->name_version generation counter. The caller must hold the graph
825 * lock.
826 */
827static int count_matching_names(struct lock_class *new_class)
828{
829 struct lock_class *class;
830 int count = 0;
831
832 if (!new_class->name)
833 return 0;
834
835 list_for_each_entry(class, &all_lock_classes, lock_entry) {
836 if (new_class->key - new_class->subclass == class->key)
837 return class->name_version;
838 if (class->name && !strcmp(class->name, new_class->name))
839 count = max(count, class->name_version);
840 }
841
842 return count + 1;
843}
844
845/* used from NMI context -- must be lockless */
846static noinstr struct lock_class *
847look_up_lock_class(const struct lockdep_map *lock, unsigned int subclass)
848{
849 struct lockdep_subclass_key *key;
850 struct hlist_head *hash_head;
851 struct lock_class *class;
852
853 if (unlikely(subclass >= MAX_LOCKDEP_SUBCLASSES)) {
854 instrumentation_begin();
855 debug_locks_off();
856 printk(KERN_ERR
857 "BUG: looking up invalid subclass: %u\n", subclass);
858 printk(KERN_ERR
859 "turning off the locking correctness validator.\n");
860 dump_stack();
861 instrumentation_end();
862 return NULL;
863 }
864
865 /*
866 * If it is not initialised then it has never been locked,
867 * so it won't be present in the hash table.
868 */
869 if (unlikely(!lock->key))
870 return NULL;
871
872 /*
873 * NOTE: the class-key must be unique. For dynamic locks, a static
874 * lock_class_key variable is passed in through the mutex_init()
875 * (or spin_lock_init()) call - which acts as the key. For static
876 * locks we use the lock object itself as the key.
877 */
878 BUILD_BUG_ON(sizeof(struct lock_class_key) >
879 sizeof(struct lockdep_map));
880
881 key = lock->key->subkeys + subclass;
882
883 hash_head = classhashentry(key);
884
885 /*
886 * We do an RCU walk of the hash, see lockdep_free_key_range().
887 */
888 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
889 return NULL;
890
891 hlist_for_each_entry_rcu(class, hash_head, hash_entry) {
892 if (class->key == key) {
893 /*
894 * Huh! same key, different name? Did someone trample
895 * on some memory? We're most confused.
896 */
897 WARN_ON_ONCE(class->name != lock->name &&
898 lock->key != &__lockdep_no_validate__);
899 return class;
900 }
901 }
902
903 return NULL;
904}
905
906/*
907 * Static locks do not have their class-keys yet - for them the key is
908 * the lock object itself. If the lock is in the per cpu area, the
909 * canonical address of the lock (per cpu offset removed) is used.
910 */
911static bool assign_lock_key(struct lockdep_map *lock)
912{
913 unsigned long can_addr, addr = (unsigned long)lock;
914
915#ifdef __KERNEL__
916 /*
917 * lockdep_free_key_range() assumes that struct lock_class_key
918 * objects do not overlap. Since we use the address of lock
919 * objects as class key for static objects, check whether the
920 * size of lock_class_key objects does not exceed the size of
921 * the smallest lock object.
922 */
923 BUILD_BUG_ON(sizeof(struct lock_class_key) > sizeof(raw_spinlock_t));
924#endif
925
926 if (__is_kernel_percpu_address(addr, &can_addr))
927 lock->key = (void *)can_addr;
928 else if (__is_module_percpu_address(addr, &can_addr))
929 lock->key = (void *)can_addr;
930 else if (static_obj(lock))
931 lock->key = (void *)lock;
932 else {
933 /* Debug-check: all keys must be persistent! */
934 debug_locks_off();
935 pr_err("INFO: trying to register non-static key.\n");
936 pr_err("The code is fine but needs lockdep annotation, or maybe\n");
937 pr_err("you didn't initialize this object before use?\n");
938 pr_err("turning off the locking correctness validator.\n");
939 dump_stack();
940 return false;
941 }
942
943 return true;
944}
945
946#ifdef CONFIG_DEBUG_LOCKDEP
947
948/* Check whether element @e occurs in list @h */
949static bool in_list(struct list_head *e, struct list_head *h)
950{
951 struct list_head *f;
952
953 list_for_each(f, h) {
954 if (e == f)
955 return true;
956 }
957
958 return false;
959}
960
961/*
962 * Check whether entry @e occurs in any of the locks_after or locks_before
963 * lists.
964 */
965static bool in_any_class_list(struct list_head *e)
966{
967 struct lock_class *class;
968 int i;
969
970 for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
971 class = &lock_classes[i];
972 if (in_list(e, &class->locks_after) ||
973 in_list(e, &class->locks_before))
974 return true;
975 }
976 return false;
977}
978
979static bool class_lock_list_valid(struct lock_class *c, struct list_head *h)
980{
981 struct lock_list *e;
982
983 list_for_each_entry(e, h, entry) {
984 if (e->links_to != c) {
985 printk(KERN_INFO "class %s: mismatch for lock entry %ld; class %s <> %s",
986 c->name ? : "(?)",
987 (unsigned long)(e - list_entries),
988 e->links_to && e->links_to->name ?
989 e->links_to->name : "(?)",
990 e->class && e->class->name ? e->class->name :
991 "(?)");
992 return false;
993 }
994 }
995 return true;
996}
997
998#ifdef CONFIG_PROVE_LOCKING
999static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
1000#endif
1001
1002static bool check_lock_chain_key(struct lock_chain *chain)
1003{
1004#ifdef CONFIG_PROVE_LOCKING
1005 u64 chain_key = INITIAL_CHAIN_KEY;
1006 int i;
1007
1008 for (i = chain->base; i < chain->base + chain->depth; i++)
1009 chain_key = iterate_chain_key(chain_key, chain_hlocks[i]);
1010 /*
1011 * The 'unsigned long long' casts avoid that a compiler warning
1012 * is reported when building tools/lib/lockdep.
1013 */
1014 if (chain->chain_key != chain_key) {
1015 printk(KERN_INFO "chain %lld: key %#llx <> %#llx\n",
1016 (unsigned long long)(chain - lock_chains),
1017 (unsigned long long)chain->chain_key,
1018 (unsigned long long)chain_key);
1019 return false;
1020 }
1021#endif
1022 return true;
1023}
1024
1025static bool in_any_zapped_class_list(struct lock_class *class)
1026{
1027 struct pending_free *pf;
1028 int i;
1029
1030 for (i = 0, pf = delayed_free.pf; i < ARRAY_SIZE(delayed_free.pf); i++, pf++) {
1031 if (in_list(&class->lock_entry, &pf->zapped))
1032 return true;
1033 }
1034
1035 return false;
1036}
1037
1038static bool __check_data_structures(void)
1039{
1040 struct lock_class *class;
1041 struct lock_chain *chain;
1042 struct hlist_head *head;
1043 struct lock_list *e;
1044 int i;
1045
1046 /* Check whether all classes occur in a lock list. */
1047 for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
1048 class = &lock_classes[i];
1049 if (!in_list(&class->lock_entry, &all_lock_classes) &&
1050 !in_list(&class->lock_entry, &free_lock_classes) &&
1051 !in_any_zapped_class_list(class)) {
1052 printk(KERN_INFO "class %px/%s is not in any class list\n",
1053 class, class->name ? : "(?)");
1054 return false;
1055 }
1056 }
1057
1058 /* Check whether all classes have valid lock lists. */
1059 for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
1060 class = &lock_classes[i];
1061 if (!class_lock_list_valid(class, &class->locks_before))
1062 return false;
1063 if (!class_lock_list_valid(class, &class->locks_after))
1064 return false;
1065 }
1066
1067 /* Check the chain_key of all lock chains. */
1068 for (i = 0; i < ARRAY_SIZE(chainhash_table); i++) {
1069 head = chainhash_table + i;
1070 hlist_for_each_entry_rcu(chain, head, entry) {
1071 if (!check_lock_chain_key(chain))
1072 return false;
1073 }
1074 }
1075
1076 /*
1077 * Check whether all list entries that are in use occur in a class
1078 * lock list.
1079 */
1080 for_each_set_bit(i, list_entries_in_use, ARRAY_SIZE(list_entries)) {
1081 e = list_entries + i;
1082 if (!in_any_class_list(&e->entry)) {
1083 printk(KERN_INFO "list entry %d is not in any class list; class %s <> %s\n",
1084 (unsigned int)(e - list_entries),
1085 e->class->name ? : "(?)",
1086 e->links_to->name ? : "(?)");
1087 return false;
1088 }
1089 }
1090
1091 /*
1092 * Check whether all list entries that are not in use do not occur in
1093 * a class lock list.
1094 */
1095 for_each_clear_bit(i, list_entries_in_use, ARRAY_SIZE(list_entries)) {
1096 e = list_entries + i;
1097 if (in_any_class_list(&e->entry)) {
1098 printk(KERN_INFO "list entry %d occurs in a class list; class %s <> %s\n",
1099 (unsigned int)(e - list_entries),
1100 e->class && e->class->name ? e->class->name :
1101 "(?)",
1102 e->links_to && e->links_to->name ?
1103 e->links_to->name : "(?)");
1104 return false;
1105 }
1106 }
1107
1108 return true;
1109}
1110
1111int check_consistency = 0;
1112module_param(check_consistency, int, 0644);
1113
1114static void check_data_structures(void)
1115{
1116 static bool once = false;
1117
1118 if (check_consistency && !once) {
1119 if (!__check_data_structures()) {
1120 once = true;
1121 WARN_ON(once);
1122 }
1123 }
1124}
1125
1126#else /* CONFIG_DEBUG_LOCKDEP */
1127
1128static inline void check_data_structures(void) { }
1129
1130#endif /* CONFIG_DEBUG_LOCKDEP */
1131
1132static void init_chain_block_buckets(void);
1133
1134/*
1135 * Initialize the lock_classes[] array elements, the free_lock_classes list
1136 * and also the delayed_free structure.
1137 */
1138static void init_data_structures_once(void)
1139{
1140 static bool __read_mostly ds_initialized, rcu_head_initialized;
1141 int i;
1142
1143 if (likely(rcu_head_initialized))
1144 return;
1145
1146 if (system_state >= SYSTEM_SCHEDULING) {
1147 init_rcu_head(&delayed_free.rcu_head);
1148 rcu_head_initialized = true;
1149 }
1150
1151 if (ds_initialized)
1152 return;
1153
1154 ds_initialized = true;
1155
1156 INIT_LIST_HEAD(&delayed_free.pf[0].zapped);
1157 INIT_LIST_HEAD(&delayed_free.pf[1].zapped);
1158
1159 for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
1160 list_add_tail(&lock_classes[i].lock_entry, &free_lock_classes);
1161 INIT_LIST_HEAD(&lock_classes[i].locks_after);
1162 INIT_LIST_HEAD(&lock_classes[i].locks_before);
1163 }
1164 init_chain_block_buckets();
1165}
1166
1167static inline struct hlist_head *keyhashentry(const struct lock_class_key *key)
1168{
1169 unsigned long hash = hash_long((uintptr_t)key, KEYHASH_BITS);
1170
1171 return lock_keys_hash + hash;
1172}
1173
1174/* Register a dynamically allocated key. */
1175void lockdep_register_key(struct lock_class_key *key)
1176{
1177 struct hlist_head *hash_head;
1178 struct lock_class_key *k;
1179 unsigned long flags;
1180
1181 if (WARN_ON_ONCE(static_obj(key)))
1182 return;
1183 hash_head = keyhashentry(key);
1184
1185 raw_local_irq_save(flags);
1186 if (!graph_lock())
1187 goto restore_irqs;
1188 hlist_for_each_entry_rcu(k, hash_head, hash_entry) {
1189 if (WARN_ON_ONCE(k == key))
1190 goto out_unlock;
1191 }
1192 hlist_add_head_rcu(&key->hash_entry, hash_head);
1193out_unlock:
1194 graph_unlock();
1195restore_irqs:
1196 raw_local_irq_restore(flags);
1197}
1198EXPORT_SYMBOL_GPL(lockdep_register_key);
1199
1200/* Check whether a key has been registered as a dynamic key. */
1201static bool is_dynamic_key(const struct lock_class_key *key)
1202{
1203 struct hlist_head *hash_head;
1204 struct lock_class_key *k;
1205 bool found = false;
1206
1207 if (WARN_ON_ONCE(static_obj(key)))
1208 return false;
1209
1210 /*
1211 * If lock debugging is disabled lock_keys_hash[] may contain
1212 * pointers to memory that has already been freed. Avoid triggering
1213 * a use-after-free in that case by returning early.
1214 */
1215 if (!debug_locks)
1216 return true;
1217
1218 hash_head = keyhashentry(key);
1219
1220 rcu_read_lock();
1221 hlist_for_each_entry_rcu(k, hash_head, hash_entry) {
1222 if (k == key) {
1223 found = true;
1224 break;
1225 }
1226 }
1227 rcu_read_unlock();
1228
1229 return found;
1230}
1231
1232/*
1233 * Register a lock's class in the hash-table, if the class is not present
1234 * yet. Otherwise we look it up. We cache the result in the lock object
1235 * itself, so actual lookup of the hash should be once per lock object.
1236 */
1237static struct lock_class *
1238register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force)
1239{
1240 struct lockdep_subclass_key *key;
1241 struct hlist_head *hash_head;
1242 struct lock_class *class;
1243
1244 DEBUG_LOCKS_WARN_ON(!irqs_disabled());
1245
1246 class = look_up_lock_class(lock, subclass);
1247 if (likely(class))
1248 goto out_set_class_cache;
1249
1250 if (!lock->key) {
1251 if (!assign_lock_key(lock))
1252 return NULL;
1253 } else if (!static_obj(lock->key) && !is_dynamic_key(lock->key)) {
1254 return NULL;
1255 }
1256
1257 key = lock->key->subkeys + subclass;
1258 hash_head = classhashentry(key);
1259
1260 if (!graph_lock()) {
1261 return NULL;
1262 }
1263 /*
1264 * We have to do the hash-walk again, to avoid races
1265 * with another CPU:
1266 */
1267 hlist_for_each_entry_rcu(class, hash_head, hash_entry) {
1268 if (class->key == key)
1269 goto out_unlock_set;
1270 }
1271
1272 init_data_structures_once();
1273
1274 /* Allocate a new lock class and add it to the hash. */
1275 class = list_first_entry_or_null(&free_lock_classes, typeof(*class),
1276 lock_entry);
1277 if (!class) {
1278 if (!debug_locks_off_graph_unlock()) {
1279 return NULL;
1280 }
1281
1282 print_lockdep_off("BUG: MAX_LOCKDEP_KEYS too low!");
1283 dump_stack();
1284 return NULL;
1285 }
1286 nr_lock_classes++;
1287 __set_bit(class - lock_classes, lock_classes_in_use);
1288 debug_atomic_inc(nr_unused_locks);
1289 class->key = key;
1290 class->name = lock->name;
1291 class->subclass = subclass;
1292 WARN_ON_ONCE(!list_empty(&class->locks_before));
1293 WARN_ON_ONCE(!list_empty(&class->locks_after));
1294 class->name_version = count_matching_names(class);
1295 class->wait_type_inner = lock->wait_type_inner;
1296 class->wait_type_outer = lock->wait_type_outer;
1297 class->lock_type = lock->lock_type;
1298 /*
1299 * We use RCU's safe list-add method to make
1300 * parallel walking of the hash-list safe:
1301 */
1302 hlist_add_head_rcu(&class->hash_entry, hash_head);
1303 /*
1304 * Remove the class from the free list and add it to the global list
1305 * of classes.
1306 */
1307 list_move_tail(&class->lock_entry, &all_lock_classes);
1308
1309 if (verbose(class)) {
1310 graph_unlock();
1311
1312 printk("\nnew class %px: %s", class->key, class->name);
1313 if (class->name_version > 1)
1314 printk(KERN_CONT "#%d", class->name_version);
1315 printk(KERN_CONT "\n");
1316 dump_stack();
1317
1318 if (!graph_lock()) {
1319 return NULL;
1320 }
1321 }
1322out_unlock_set:
1323 graph_unlock();
1324
1325out_set_class_cache:
1326 if (!subclass || force)
1327 lock->class_cache[0] = class;
1328 else if (subclass < NR_LOCKDEP_CACHING_CLASSES)
1329 lock->class_cache[subclass] = class;
1330
1331 /*
1332 * Hash collision, did we smoke some? We found a class with a matching
1333 * hash but the subclass -- which is hashed in -- didn't match.
1334 */
1335 if (DEBUG_LOCKS_WARN_ON(class->subclass != subclass))
1336 return NULL;
1337
1338 return class;
1339}
1340
1341#ifdef CONFIG_PROVE_LOCKING
1342/*
1343 * Allocate a lockdep entry. (assumes the graph_lock held, returns
1344 * with NULL on failure)
1345 */
1346static struct lock_list *alloc_list_entry(void)
1347{
1348 int idx = find_first_zero_bit(list_entries_in_use,
1349 ARRAY_SIZE(list_entries));
1350
1351 if (idx >= ARRAY_SIZE(list_entries)) {
1352 if (!debug_locks_off_graph_unlock())
1353 return NULL;
1354
1355 print_lockdep_off("BUG: MAX_LOCKDEP_ENTRIES too low!");
1356 dump_stack();
1357 return NULL;
1358 }
1359 nr_list_entries++;
1360 __set_bit(idx, list_entries_in_use);
1361 return list_entries + idx;
1362}
1363
1364/*
1365 * Add a new dependency to the head of the list:
1366 */
1367static int add_lock_to_list(struct lock_class *this,
1368 struct lock_class *links_to, struct list_head *head,
1369 unsigned long ip, u16 distance, u8 dep,
1370 const struct lock_trace *trace)
1371{
1372 struct lock_list *entry;
1373 /*
1374 * Lock not present yet - get a new dependency struct and
1375 * add it to the list:
1376 */
1377 entry = alloc_list_entry();
1378 if (!entry)
1379 return 0;
1380
1381 entry->class = this;
1382 entry->links_to = links_to;
1383 entry->dep = dep;
1384 entry->distance = distance;
1385 entry->trace = trace;
1386 /*
1387 * Both allocation and removal are done under the graph lock; but
1388 * iteration is under RCU-sched; see look_up_lock_class() and
1389 * lockdep_free_key_range().
1390 */
1391 list_add_tail_rcu(&entry->entry, head);
1392
1393 return 1;
1394}
1395
1396/*
1397 * For good efficiency of modular, we use power of 2
1398 */
1399#define MAX_CIRCULAR_QUEUE_SIZE (1UL << CONFIG_LOCKDEP_CIRCULAR_QUEUE_BITS)
1400#define CQ_MASK (MAX_CIRCULAR_QUEUE_SIZE-1)
1401
1402/*
1403 * The circular_queue and helpers are used to implement graph
1404 * breadth-first search (BFS) algorithm, by which we can determine
1405 * whether there is a path from a lock to another. In deadlock checks,
1406 * a path from the next lock to be acquired to a previous held lock
1407 * indicates that adding the <prev> -> <next> lock dependency will
1408 * produce a circle in the graph. Breadth-first search instead of
1409 * depth-first search is used in order to find the shortest (circular)
1410 * path.
1411 */
1412struct circular_queue {
1413 struct lock_list *element[MAX_CIRCULAR_QUEUE_SIZE];
1414 unsigned int front, rear;
1415};
1416
1417static struct circular_queue lock_cq;
1418
1419unsigned int max_bfs_queue_depth;
1420
1421static unsigned int lockdep_dependency_gen_id;
1422
1423static inline void __cq_init(struct circular_queue *cq)
1424{
1425 cq->front = cq->rear = 0;
1426 lockdep_dependency_gen_id++;
1427}
1428
1429static inline int __cq_empty(struct circular_queue *cq)
1430{
1431 return (cq->front == cq->rear);
1432}
1433
1434static inline int __cq_full(struct circular_queue *cq)
1435{
1436 return ((cq->rear + 1) & CQ_MASK) == cq->front;
1437}
1438
1439static inline int __cq_enqueue(struct circular_queue *cq, struct lock_list *elem)
1440{
1441 if (__cq_full(cq))
1442 return -1;
1443
1444 cq->element[cq->rear] = elem;
1445 cq->rear = (cq->rear + 1) & CQ_MASK;
1446 return 0;
1447}
1448
1449/*
1450 * Dequeue an element from the circular_queue, return a lock_list if
1451 * the queue is not empty, or NULL if otherwise.
1452 */
1453static inline struct lock_list * __cq_dequeue(struct circular_queue *cq)
1454{
1455 struct lock_list * lock;
1456
1457 if (__cq_empty(cq))
1458 return NULL;
1459
1460 lock = cq->element[cq->front];
1461 cq->front = (cq->front + 1) & CQ_MASK;
1462
1463 return lock;
1464}
1465
1466static inline unsigned int __cq_get_elem_count(struct circular_queue *cq)
1467{
1468 return (cq->rear - cq->front) & CQ_MASK;
1469}
1470
1471static inline void mark_lock_accessed(struct lock_list *lock)
1472{
1473 lock->class->dep_gen_id = lockdep_dependency_gen_id;
1474}
1475
1476static inline void visit_lock_entry(struct lock_list *lock,
1477 struct lock_list *parent)
1478{
1479 lock->parent = parent;
1480}
1481
1482static inline unsigned long lock_accessed(struct lock_list *lock)
1483{
1484 return lock->class->dep_gen_id == lockdep_dependency_gen_id;
1485}
1486
1487static inline struct lock_list *get_lock_parent(struct lock_list *child)
1488{
1489 return child->parent;
1490}
1491
1492static inline int get_lock_depth(struct lock_list *child)
1493{
1494 int depth = 0;
1495 struct lock_list *parent;
1496
1497 while ((parent = get_lock_parent(child))) {
1498 child = parent;
1499 depth++;
1500 }
1501 return depth;
1502}
1503
1504/*
1505 * Return the forward or backward dependency list.
1506 *
1507 * @lock: the lock_list to get its class's dependency list
1508 * @offset: the offset to struct lock_class to determine whether it is
1509 * locks_after or locks_before
1510 */
1511static inline struct list_head *get_dep_list(struct lock_list *lock, int offset)
1512{
1513 void *lock_class = lock->class;
1514
1515 return lock_class + offset;
1516}
1517/*
1518 * Return values of a bfs search:
1519 *
1520 * BFS_E* indicates an error
1521 * BFS_R* indicates a result (match or not)
1522 *
1523 * BFS_EINVALIDNODE: Find a invalid node in the graph.
1524 *
1525 * BFS_EQUEUEFULL: The queue is full while doing the bfs.
1526 *
1527 * BFS_RMATCH: Find the matched node in the graph, and put that node into
1528 * *@target_entry.
1529 *
1530 * BFS_RNOMATCH: Haven't found the matched node and keep *@target_entry
1531 * _unchanged_.
1532 */
1533enum bfs_result {
1534 BFS_EINVALIDNODE = -2,
1535 BFS_EQUEUEFULL = -1,
1536 BFS_RMATCH = 0,
1537 BFS_RNOMATCH = 1,
1538};
1539
1540/*
1541 * bfs_result < 0 means error
1542 */
1543static inline bool bfs_error(enum bfs_result res)
1544{
1545 return res < 0;
1546}
1547
1548/*
1549 * DEP_*_BIT in lock_list::dep
1550 *
1551 * For dependency @prev -> @next:
1552 *
1553 * SR: @prev is shared reader (->read != 0) and @next is recursive reader
1554 * (->read == 2)
1555 * ER: @prev is exclusive locker (->read == 0) and @next is recursive reader
1556 * SN: @prev is shared reader and @next is non-recursive locker (->read != 2)
1557 * EN: @prev is exclusive locker and @next is non-recursive locker
1558 *
1559 * Note that we define the value of DEP_*_BITs so that:
1560 * bit0 is prev->read == 0
1561 * bit1 is next->read != 2
1562 */
1563#define DEP_SR_BIT (0 + (0 << 1)) /* 0 */
1564#define DEP_ER_BIT (1 + (0 << 1)) /* 1 */
1565#define DEP_SN_BIT (0 + (1 << 1)) /* 2 */
1566#define DEP_EN_BIT (1 + (1 << 1)) /* 3 */
1567
1568#define DEP_SR_MASK (1U << (DEP_SR_BIT))
1569#define DEP_ER_MASK (1U << (DEP_ER_BIT))
1570#define DEP_SN_MASK (1U << (DEP_SN_BIT))
1571#define DEP_EN_MASK (1U << (DEP_EN_BIT))
1572
1573static inline unsigned int
1574__calc_dep_bit(struct held_lock *prev, struct held_lock *next)
1575{
1576 return (prev->read == 0) + ((next->read != 2) << 1);
1577}
1578
1579static inline u8 calc_dep(struct held_lock *prev, struct held_lock *next)
1580{
1581 return 1U << __calc_dep_bit(prev, next);
1582}
1583
1584/*
1585 * calculate the dep_bit for backwards edges. We care about whether @prev is
1586 * shared and whether @next is recursive.
1587 */
1588static inline unsigned int
1589__calc_dep_bitb(struct held_lock *prev, struct held_lock *next)
1590{
1591 return (next->read != 2) + ((prev->read == 0) << 1);
1592}
1593
1594static inline u8 calc_depb(struct held_lock *prev, struct held_lock *next)
1595{
1596 return 1U << __calc_dep_bitb(prev, next);
1597}
1598
1599/*
1600 * Initialize a lock_list entry @lock belonging to @class as the root for a BFS
1601 * search.
1602 */
1603static inline void __bfs_init_root(struct lock_list *lock,
1604 struct lock_class *class)
1605{
1606 lock->class = class;
1607 lock->parent = NULL;
1608 lock->only_xr = 0;
1609}
1610
1611/*
1612 * Initialize a lock_list entry @lock based on a lock acquisition @hlock as the
1613 * root for a BFS search.
1614 *
1615 * ->only_xr of the initial lock node is set to @hlock->read == 2, to make sure
1616 * that <prev> -> @hlock and @hlock -> <whatever __bfs() found> is not -(*R)->
1617 * and -(S*)->.
1618 */
1619static inline void bfs_init_root(struct lock_list *lock,
1620 struct held_lock *hlock)
1621{
1622 __bfs_init_root(lock, hlock_class(hlock));
1623 lock->only_xr = (hlock->read == 2);
1624}
1625
1626/*
1627 * Similar to bfs_init_root() but initialize the root for backwards BFS.
1628 *
1629 * ->only_xr of the initial lock node is set to @hlock->read != 0, to make sure
1630 * that <next> -> @hlock and @hlock -> <whatever backwards BFS found> is not
1631 * -(*S)-> and -(R*)-> (reverse order of -(*R)-> and -(S*)->).
1632 */
1633static inline void bfs_init_rootb(struct lock_list *lock,
1634 struct held_lock *hlock)
1635{
1636 __bfs_init_root(lock, hlock_class(hlock));
1637 lock->only_xr = (hlock->read != 0);
1638}
1639
1640static inline struct lock_list *__bfs_next(struct lock_list *lock, int offset)
1641{
1642 if (!lock || !lock->parent)
1643 return NULL;
1644
1645 return list_next_or_null_rcu(get_dep_list(lock->parent, offset),
1646 &lock->entry, struct lock_list, entry);
1647}
1648
1649/*
1650 * Breadth-First Search to find a strong path in the dependency graph.
1651 *
1652 * @source_entry: the source of the path we are searching for.
1653 * @data: data used for the second parameter of @match function
1654 * @match: match function for the search
1655 * @target_entry: pointer to the target of a matched path
1656 * @offset: the offset to struct lock_class to determine whether it is
1657 * locks_after or locks_before
1658 *
1659 * We may have multiple edges (considering different kinds of dependencies,
1660 * e.g. ER and SN) between two nodes in the dependency graph. But
1661 * only the strong dependency path in the graph is relevant to deadlocks. A
1662 * strong dependency path is a dependency path that doesn't have two adjacent
1663 * dependencies as -(*R)-> -(S*)->, please see:
1664 *
1665 * Documentation/locking/lockdep-design.rst
1666 *
1667 * for more explanation of the definition of strong dependency paths
1668 *
1669 * In __bfs(), we only traverse in the strong dependency path:
1670 *
1671 * In lock_list::only_xr, we record whether the previous dependency only
1672 * has -(*R)-> in the search, and if it does (prev only has -(*R)->), we
1673 * filter out any -(S*)-> in the current dependency and after that, the
1674 * ->only_xr is set according to whether we only have -(*R)-> left.
1675 */
1676static enum bfs_result __bfs(struct lock_list *source_entry,
1677 void *data,
1678 bool (*match)(struct lock_list *entry, void *data),
1679 bool (*skip)(struct lock_list *entry, void *data),
1680 struct lock_list **target_entry,
1681 int offset)
1682{
1683 struct circular_queue *cq = &lock_cq;
1684 struct lock_list *lock = NULL;
1685 struct lock_list *entry;
1686 struct list_head *head;
1687 unsigned int cq_depth;
1688 bool first;
1689
1690 lockdep_assert_locked();
1691
1692 __cq_init(cq);
1693 __cq_enqueue(cq, source_entry);
1694
1695 while ((lock = __bfs_next(lock, offset)) || (lock = __cq_dequeue(cq))) {
1696 if (!lock->class)
1697 return BFS_EINVALIDNODE;
1698
1699 /*
1700 * Step 1: check whether we already finish on this one.
1701 *
1702 * If we have visited all the dependencies from this @lock to
1703 * others (iow, if we have visited all lock_list entries in
1704 * @lock->class->locks_{after,before}) we skip, otherwise go
1705 * and visit all the dependencies in the list and mark this
1706 * list accessed.
1707 */
1708 if (lock_accessed(lock))
1709 continue;
1710 else
1711 mark_lock_accessed(lock);
1712
1713 /*
1714 * Step 2: check whether prev dependency and this form a strong
1715 * dependency path.
1716 */
1717 if (lock->parent) { /* Parent exists, check prev dependency */
1718 u8 dep = lock->dep;
1719 bool prev_only_xr = lock->parent->only_xr;
1720
1721 /*
1722 * Mask out all -(S*)-> if we only have *R in previous
1723 * step, because -(*R)-> -(S*)-> don't make up a strong
1724 * dependency.
1725 */
1726 if (prev_only_xr)
1727 dep &= ~(DEP_SR_MASK | DEP_SN_MASK);
1728
1729 /* If nothing left, we skip */
1730 if (!dep)
1731 continue;
1732
1733 /* If there are only -(*R)-> left, set that for the next step */
1734 lock->only_xr = !(dep & (DEP_SN_MASK | DEP_EN_MASK));
1735 }
1736
1737 /*
1738 * Step 3: we haven't visited this and there is a strong
1739 * dependency path to this, so check with @match.
1740 * If @skip is provide and returns true, we skip this
1741 * lock (and any path this lock is in).
1742 */
1743 if (skip && skip(lock, data))
1744 continue;
1745
1746 if (match(lock, data)) {
1747 *target_entry = lock;
1748 return BFS_RMATCH;
1749 }
1750
1751 /*
1752 * Step 4: if not match, expand the path by adding the
1753 * forward or backwards dependencies in the search
1754 *
1755 */
1756 first = true;
1757 head = get_dep_list(lock, offset);
1758 list_for_each_entry_rcu(entry, head, entry) {
1759 visit_lock_entry(entry, lock);
1760
1761 /*
1762 * Note we only enqueue the first of the list into the
1763 * queue, because we can always find a sibling
1764 * dependency from one (see __bfs_next()), as a result
1765 * the space of queue is saved.
1766 */
1767 if (!first)
1768 continue;
1769
1770 first = false;
1771
1772 if (__cq_enqueue(cq, entry))
1773 return BFS_EQUEUEFULL;
1774
1775 cq_depth = __cq_get_elem_count(cq);
1776 if (max_bfs_queue_depth < cq_depth)
1777 max_bfs_queue_depth = cq_depth;
1778 }
1779 }
1780
1781 return BFS_RNOMATCH;
1782}
1783
1784static inline enum bfs_result
1785__bfs_forwards(struct lock_list *src_entry,
1786 void *data,
1787 bool (*match)(struct lock_list *entry, void *data),
1788 bool (*skip)(struct lock_list *entry, void *data),
1789 struct lock_list **target_entry)
1790{
1791 return __bfs(src_entry, data, match, skip, target_entry,
1792 offsetof(struct lock_class, locks_after));
1793
1794}
1795
1796static inline enum bfs_result
1797__bfs_backwards(struct lock_list *src_entry,
1798 void *data,
1799 bool (*match)(struct lock_list *entry, void *data),
1800 bool (*skip)(struct lock_list *entry, void *data),
1801 struct lock_list **target_entry)
1802{
1803 return __bfs(src_entry, data, match, skip, target_entry,
1804 offsetof(struct lock_class, locks_before));
1805
1806}
1807
1808static void print_lock_trace(const struct lock_trace *trace,
1809 unsigned int spaces)
1810{
1811 stack_trace_print(trace->entries, trace->nr_entries, spaces);
1812}
1813
1814/*
1815 * Print a dependency chain entry (this is only done when a deadlock
1816 * has been detected):
1817 */
1818static noinline void
1819print_circular_bug_entry(struct lock_list *target, int depth)
1820{
1821 if (debug_locks_silent)
1822 return;
1823 printk("\n-> #%u", depth);
1824 print_lock_name(target->class);
1825 printk(KERN_CONT ":\n");
1826 print_lock_trace(target->trace, 6);
1827}
1828
1829static void
1830print_circular_lock_scenario(struct held_lock *src,
1831 struct held_lock *tgt,
1832 struct lock_list *prt)
1833{
1834 struct lock_class *source = hlock_class(src);
1835 struct lock_class *target = hlock_class(tgt);
1836 struct lock_class *parent = prt->class;
1837
1838 /*
1839 * A direct locking problem where unsafe_class lock is taken
1840 * directly by safe_class lock, then all we need to show
1841 * is the deadlock scenario, as it is obvious that the
1842 * unsafe lock is taken under the safe lock.
1843 *
1844 * But if there is a chain instead, where the safe lock takes
1845 * an intermediate lock (middle_class) where this lock is
1846 * not the same as the safe lock, then the lock chain is
1847 * used to describe the problem. Otherwise we would need
1848 * to show a different CPU case for each link in the chain
1849 * from the safe_class lock to the unsafe_class lock.
1850 */
1851 if (parent != source) {
1852 printk("Chain exists of:\n ");
1853 __print_lock_name(source);
1854 printk(KERN_CONT " --> ");
1855 __print_lock_name(parent);
1856 printk(KERN_CONT " --> ");
1857 __print_lock_name(target);
1858 printk(KERN_CONT "\n\n");
1859 }
1860
1861 printk(" Possible unsafe locking scenario:\n\n");
1862 printk(" CPU0 CPU1\n");
1863 printk(" ---- ----\n");
1864 printk(" lock(");
1865 __print_lock_name(target);
1866 printk(KERN_CONT ");\n");
1867 printk(" lock(");
1868 __print_lock_name(parent);
1869 printk(KERN_CONT ");\n");
1870 printk(" lock(");
1871 __print_lock_name(target);
1872 printk(KERN_CONT ");\n");
1873 printk(" lock(");
1874 __print_lock_name(source);
1875 printk(KERN_CONT ");\n");
1876 printk("\n *** DEADLOCK ***\n\n");
1877}
1878
1879/*
1880 * When a circular dependency is detected, print the
1881 * header first:
1882 */
1883static noinline void
1884print_circular_bug_header(struct lock_list *entry, unsigned int depth,
1885 struct held_lock *check_src,
1886 struct held_lock *check_tgt)
1887{
1888 struct task_struct *curr = current;
1889
1890 if (debug_locks_silent)
1891 return;
1892
1893 pr_warn("\n");
1894 pr_warn("======================================================\n");
1895 pr_warn("WARNING: possible circular locking dependency detected\n");
1896 print_kernel_ident();
1897 pr_warn("------------------------------------------------------\n");
1898 pr_warn("%s/%d is trying to acquire lock:\n",
1899 curr->comm, task_pid_nr(curr));
1900 print_lock(check_src);
1901
1902 pr_warn("\nbut task is already holding lock:\n");
1903
1904 print_lock(check_tgt);
1905 pr_warn("\nwhich lock already depends on the new lock.\n\n");
1906 pr_warn("\nthe existing dependency chain (in reverse order) is:\n");
1907
1908 print_circular_bug_entry(entry, depth);
1909}
1910
1911/*
1912 * We are about to add A -> B into the dependency graph, and in __bfs() a
1913 * strong dependency path A -> .. -> B is found: hlock_class equals
1914 * entry->class.
1915 *
1916 * If A -> .. -> B can replace A -> B in any __bfs() search (means the former
1917 * is _stronger_ than or equal to the latter), we consider A -> B as redundant.
1918 * For example if A -> .. -> B is -(EN)-> (i.e. A -(E*)-> .. -(*N)-> B), and A
1919 * -> B is -(ER)-> or -(EN)->, then we don't need to add A -> B into the
1920 * dependency graph, as any strong path ..-> A -> B ->.. we can get with
1921 * having dependency A -> B, we could already get a equivalent path ..-> A ->
1922 * .. -> B -> .. with A -> .. -> B. Therefore A -> B is redundant.
1923 *
1924 * We need to make sure both the start and the end of A -> .. -> B is not
1925 * weaker than A -> B. For the start part, please see the comment in
1926 * check_redundant(). For the end part, we need:
1927 *
1928 * Either
1929 *
1930 * a) A -> B is -(*R)-> (everything is not weaker than that)
1931 *
1932 * or
1933 *
1934 * b) A -> .. -> B is -(*N)-> (nothing is stronger than this)
1935 *
1936 */
1937static inline bool hlock_equal(struct lock_list *entry, void *data)
1938{
1939 struct held_lock *hlock = (struct held_lock *)data;
1940
1941 return hlock_class(hlock) == entry->class && /* Found A -> .. -> B */
1942 (hlock->read == 2 || /* A -> B is -(*R)-> */
1943 !entry->only_xr); /* A -> .. -> B is -(*N)-> */
1944}
1945
1946/*
1947 * We are about to add B -> A into the dependency graph, and in __bfs() a
1948 * strong dependency path A -> .. -> B is found: hlock_class equals
1949 * entry->class.
1950 *
1951 * We will have a deadlock case (conflict) if A -> .. -> B -> A is a strong
1952 * dependency cycle, that means:
1953 *
1954 * Either
1955 *
1956 * a) B -> A is -(E*)->
1957 *
1958 * or
1959 *
1960 * b) A -> .. -> B is -(*N)-> (i.e. A -> .. -(*N)-> B)
1961 *
1962 * as then we don't have -(*R)-> -(S*)-> in the cycle.
1963 */
1964static inline bool hlock_conflict(struct lock_list *entry, void *data)
1965{
1966 struct held_lock *hlock = (struct held_lock *)data;
1967
1968 return hlock_class(hlock) == entry->class && /* Found A -> .. -> B */
1969 (hlock->read == 0 || /* B -> A is -(E*)-> */
1970 !entry->only_xr); /* A -> .. -> B is -(*N)-> */
1971}
1972
1973static noinline void print_circular_bug(struct lock_list *this,
1974 struct lock_list *target,
1975 struct held_lock *check_src,
1976 struct held_lock *check_tgt)
1977{
1978 struct task_struct *curr = current;
1979 struct lock_list *parent;
1980 struct lock_list *first_parent;
1981 int depth;
1982
1983 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
1984 return;
1985
1986 this->trace = save_trace();
1987 if (!this->trace)
1988 return;
1989
1990 depth = get_lock_depth(target);
1991
1992 print_circular_bug_header(target, depth, check_src, check_tgt);
1993
1994 parent = get_lock_parent(target);
1995 first_parent = parent;
1996
1997 while (parent) {
1998 print_circular_bug_entry(parent, --depth);
1999 parent = get_lock_parent(parent);
2000 }
2001
2002 printk("\nother info that might help us debug this:\n\n");
2003 print_circular_lock_scenario(check_src, check_tgt,
2004 first_parent);
2005
2006 lockdep_print_held_locks(curr);
2007
2008 printk("\nstack backtrace:\n");
2009 dump_stack();
2010}
2011
2012static noinline void print_bfs_bug(int ret)
2013{
2014 if (!debug_locks_off_graph_unlock())
2015 return;
2016
2017 /*
2018 * Breadth-first-search failed, graph got corrupted?
2019 */
2020 WARN(1, "lockdep bfs error:%d\n", ret);
2021}
2022
2023static bool noop_count(struct lock_list *entry, void *data)
2024{
2025 (*(unsigned long *)data)++;
2026 return false;
2027}
2028
2029static unsigned long __lockdep_count_forward_deps(struct lock_list *this)
2030{
2031 unsigned long count = 0;
2032 struct lock_list *target_entry;
2033
2034 __bfs_forwards(this, (void *)&count, noop_count, NULL, &target_entry);
2035
2036 return count;
2037}
2038unsigned long lockdep_count_forward_deps(struct lock_class *class)
2039{
2040 unsigned long ret, flags;
2041 struct lock_list this;
2042
2043 __bfs_init_root(&this, class);
2044
2045 raw_local_irq_save(flags);
2046 lockdep_lock();
2047 ret = __lockdep_count_forward_deps(&this);
2048 lockdep_unlock();
2049 raw_local_irq_restore(flags);
2050
2051 return ret;
2052}
2053
2054static unsigned long __lockdep_count_backward_deps(struct lock_list *this)
2055{
2056 unsigned long count = 0;
2057 struct lock_list *target_entry;
2058
2059 __bfs_backwards(this, (void *)&count, noop_count, NULL, &target_entry);
2060
2061 return count;
2062}
2063
2064unsigned long lockdep_count_backward_deps(struct lock_class *class)
2065{
2066 unsigned long ret, flags;
2067 struct lock_list this;
2068
2069 __bfs_init_root(&this, class);
2070
2071 raw_local_irq_save(flags);
2072 lockdep_lock();
2073 ret = __lockdep_count_backward_deps(&this);
2074 lockdep_unlock();
2075 raw_local_irq_restore(flags);
2076
2077 return ret;
2078}
2079
2080/*
2081 * Check that the dependency graph starting at <src> can lead to
2082 * <target> or not.
2083 */
2084static noinline enum bfs_result
2085check_path(struct held_lock *target, struct lock_list *src_entry,
2086 bool (*match)(struct lock_list *entry, void *data),
2087 bool (*skip)(struct lock_list *entry, void *data),
2088 struct lock_list **target_entry)
2089{
2090 enum bfs_result ret;
2091
2092 ret = __bfs_forwards(src_entry, target, match, skip, target_entry);
2093
2094 if (unlikely(bfs_error(ret)))
2095 print_bfs_bug(ret);
2096
2097 return ret;
2098}
2099
2100/*
2101 * Prove that the dependency graph starting at <src> can not
2102 * lead to <target>. If it can, there is a circle when adding
2103 * <target> -> <src> dependency.
2104 *
2105 * Print an error and return BFS_RMATCH if it does.
2106 */
2107static noinline enum bfs_result
2108check_noncircular(struct held_lock *src, struct held_lock *target,
2109 struct lock_trace **const trace)
2110{
2111 enum bfs_result ret;
2112 struct lock_list *target_entry;
2113 struct lock_list src_entry;
2114
2115 bfs_init_root(&src_entry, src);
2116
2117 debug_atomic_inc(nr_cyclic_checks);
2118
2119 ret = check_path(target, &src_entry, hlock_conflict, NULL, &target_entry);
2120
2121 if (unlikely(ret == BFS_RMATCH)) {
2122 if (!*trace) {
2123 /*
2124 * If save_trace fails here, the printing might
2125 * trigger a WARN but because of the !nr_entries it
2126 * should not do bad things.
2127 */
2128 *trace = save_trace();
2129 }
2130
2131 print_circular_bug(&src_entry, target_entry, src, target);
2132 }
2133
2134 return ret;
2135}
2136
2137#ifdef CONFIG_TRACE_IRQFLAGS
2138
2139/*
2140 * Forwards and backwards subgraph searching, for the purposes of
2141 * proving that two subgraphs can be connected by a new dependency
2142 * without creating any illegal irq-safe -> irq-unsafe lock dependency.
2143 *
2144 * A irq safe->unsafe deadlock happens with the following conditions:
2145 *
2146 * 1) We have a strong dependency path A -> ... -> B
2147 *
2148 * 2) and we have ENABLED_IRQ usage of B and USED_IN_IRQ usage of A, therefore
2149 * irq can create a new dependency B -> A (consider the case that a holder
2150 * of B gets interrupted by an irq whose handler will try to acquire A).
2151 *
2152 * 3) the dependency circle A -> ... -> B -> A we get from 1) and 2) is a
2153 * strong circle:
2154 *
2155 * For the usage bits of B:
2156 * a) if A -> B is -(*N)->, then B -> A could be any type, so any
2157 * ENABLED_IRQ usage suffices.
2158 * b) if A -> B is -(*R)->, then B -> A must be -(E*)->, so only
2159 * ENABLED_IRQ_*_READ usage suffices.
2160 *
2161 * For the usage bits of A:
2162 * c) if A -> B is -(E*)->, then B -> A could be any type, so any
2163 * USED_IN_IRQ usage suffices.
2164 * d) if A -> B is -(S*)->, then B -> A must be -(*N)->, so only
2165 * USED_IN_IRQ_*_READ usage suffices.
2166 */
2167
2168/*
2169 * There is a strong dependency path in the dependency graph: A -> B, and now
2170 * we need to decide which usage bit of A should be accumulated to detect
2171 * safe->unsafe bugs.
2172 *
2173 * Note that usage_accumulate() is used in backwards search, so ->only_xr
2174 * stands for whether A -> B only has -(S*)-> (in this case ->only_xr is true).
2175 *
2176 * As above, if only_xr is false, which means A -> B has -(E*)-> dependency
2177 * path, any usage of A should be considered. Otherwise, we should only
2178 * consider _READ usage.
2179 */
2180static inline bool usage_accumulate(struct lock_list *entry, void *mask)
2181{
2182 if (!entry->only_xr)
2183 *(unsigned long *)mask |= entry->class->usage_mask;
2184 else /* Mask out _READ usage bits */
2185 *(unsigned long *)mask |= (entry->class->usage_mask & LOCKF_IRQ);
2186
2187 return false;
2188}
2189
2190/*
2191 * There is a strong dependency path in the dependency graph: A -> B, and now
2192 * we need to decide which usage bit of B conflicts with the usage bits of A,
2193 * i.e. which usage bit of B may introduce safe->unsafe deadlocks.
2194 *
2195 * As above, if only_xr is false, which means A -> B has -(*N)-> dependency
2196 * path, any usage of B should be considered. Otherwise, we should only
2197 * consider _READ usage.
2198 */
2199static inline bool usage_match(struct lock_list *entry, void *mask)
2200{
2201 if (!entry->only_xr)
2202 return !!(entry->class->usage_mask & *(unsigned long *)mask);
2203 else /* Mask out _READ usage bits */
2204 return !!((entry->class->usage_mask & LOCKF_IRQ) & *(unsigned long *)mask);
2205}
2206
2207static inline bool usage_skip(struct lock_list *entry, void *mask)
2208{
2209 /*
2210 * Skip local_lock() for irq inversion detection.
2211 *
2212 * For !RT, local_lock() is not a real lock, so it won't carry any
2213 * dependency.
2214 *
2215 * For RT, an irq inversion happens when we have lock A and B, and on
2216 * some CPU we can have:
2217 *
2218 * lock(A);
2219 * <interrupted>
2220 * lock(B);
2221 *
2222 * where lock(B) cannot sleep, and we have a dependency B -> ... -> A.
2223 *
2224 * Now we prove local_lock() cannot exist in that dependency. First we
2225 * have the observation for any lock chain L1 -> ... -> Ln, for any
2226 * 1 <= i <= n, Li.inner_wait_type <= L1.inner_wait_type, otherwise
2227 * wait context check will complain. And since B is not a sleep lock,
2228 * therefore B.inner_wait_type >= 2, and since the inner_wait_type of
2229 * local_lock() is 3, which is greater than 2, therefore there is no
2230 * way the local_lock() exists in the dependency B -> ... -> A.
2231 *
2232 * As a result, we will skip local_lock(), when we search for irq
2233 * inversion bugs.
2234 */
2235 if (entry->class->lock_type == LD_LOCK_PERCPU) {
2236 if (DEBUG_LOCKS_WARN_ON(entry->class->wait_type_inner < LD_WAIT_CONFIG))
2237 return false;
2238
2239 return true;
2240 }
2241
2242 return false;
2243}
2244
2245/*
2246 * Find a node in the forwards-direction dependency sub-graph starting
2247 * at @root->class that matches @bit.
2248 *
2249 * Return BFS_MATCH if such a node exists in the subgraph, and put that node
2250 * into *@target_entry.
2251 */
2252static enum bfs_result
2253find_usage_forwards(struct lock_list *root, unsigned long usage_mask,
2254 struct lock_list **target_entry)
2255{
2256 enum bfs_result result;
2257
2258 debug_atomic_inc(nr_find_usage_forwards_checks);
2259
2260 result = __bfs_forwards(root, &usage_mask, usage_match, usage_skip, target_entry);
2261
2262 return result;
2263}
2264
2265/*
2266 * Find a node in the backwards-direction dependency sub-graph starting
2267 * at @root->class that matches @bit.
2268 */
2269static enum bfs_result
2270find_usage_backwards(struct lock_list *root, unsigned long usage_mask,
2271 struct lock_list **target_entry)
2272{
2273 enum bfs_result result;
2274
2275 debug_atomic_inc(nr_find_usage_backwards_checks);
2276
2277 result = __bfs_backwards(root, &usage_mask, usage_match, usage_skip, target_entry);
2278
2279 return result;
2280}
2281
2282static void print_lock_class_header(struct lock_class *class, int depth)
2283{
2284 int bit;
2285
2286 printk("%*s->", depth, "");
2287 print_lock_name(class);
2288#ifdef CONFIG_DEBUG_LOCKDEP
2289 printk(KERN_CONT " ops: %lu", debug_class_ops_read(class));
2290#endif
2291 printk(KERN_CONT " {\n");
2292
2293 for (bit = 0; bit < LOCK_TRACE_STATES; bit++) {
2294 if (class->usage_mask & (1 << bit)) {
2295 int len = depth;
2296
2297 len += printk("%*s %s", depth, "", usage_str[bit]);
2298 len += printk(KERN_CONT " at:\n");
2299 print_lock_trace(class->usage_traces[bit], len);
2300 }
2301 }
2302 printk("%*s }\n", depth, "");
2303
2304 printk("%*s ... key at: [<%px>] %pS\n",
2305 depth, "", class->key, class->key);
2306}
2307
2308/*
2309 * Dependency path printing:
2310 *
2311 * After BFS we get a lock dependency path (linked via ->parent of lock_list),
2312 * printing out each lock in the dependency path will help on understanding how
2313 * the deadlock could happen. Here are some details about dependency path
2314 * printing:
2315 *
2316 * 1) A lock_list can be either forwards or backwards for a lock dependency,
2317 * for a lock dependency A -> B, there are two lock_lists:
2318 *
2319 * a) lock_list in the ->locks_after list of A, whose ->class is B and
2320 * ->links_to is A. In this case, we can say the lock_list is
2321 * "A -> B" (forwards case).
2322 *
2323 * b) lock_list in the ->locks_before list of B, whose ->class is A
2324 * and ->links_to is B. In this case, we can say the lock_list is
2325 * "B <- A" (bacwards case).
2326 *
2327 * The ->trace of both a) and b) point to the call trace where B was
2328 * acquired with A held.
2329 *
2330 * 2) A "helper" lock_list is introduced during BFS, this lock_list doesn't
2331 * represent a certain lock dependency, it only provides an initial entry
2332 * for BFS. For example, BFS may introduce a "helper" lock_list whose
2333 * ->class is A, as a result BFS will search all dependencies starting with
2334 * A, e.g. A -> B or A -> C.
2335 *
2336 * The notation of a forwards helper lock_list is like "-> A", which means
2337 * we should search the forwards dependencies starting with "A", e.g A -> B
2338 * or A -> C.
2339 *
2340 * The notation of a bacwards helper lock_list is like "<- B", which means
2341 * we should search the backwards dependencies ending with "B", e.g.
2342 * B <- A or B <- C.
2343 */
2344
2345/*
2346 * printk the shortest lock dependencies from @root to @leaf in reverse order.
2347 *
2348 * We have a lock dependency path as follow:
2349 *
2350 * @root @leaf
2351 * | |
2352 * V V
2353 * ->parent ->parent
2354 * | lock_list | <--------- | lock_list | ... | lock_list | <--------- | lock_list |
2355 * | -> L1 | | L1 -> L2 | ... |Ln-2 -> Ln-1| | Ln-1 -> Ln|
2356 *
2357 * , so it's natural that we start from @leaf and print every ->class and
2358 * ->trace until we reach the @root.
2359 */
2360static void __used
2361print_shortest_lock_dependencies(struct lock_list *leaf,
2362 struct lock_list *root)
2363{
2364 struct lock_list *entry = leaf;
2365 int depth;
2366
2367 /*compute depth from generated tree by BFS*/
2368 depth = get_lock_depth(leaf);
2369
2370 do {
2371 print_lock_class_header(entry->class, depth);
2372 printk("%*s ... acquired at:\n", depth, "");
2373 print_lock_trace(entry->trace, 2);
2374 printk("\n");
2375
2376 if (depth == 0 && (entry != root)) {
2377 printk("lockdep:%s bad path found in chain graph\n", __func__);
2378 break;
2379 }
2380
2381 entry = get_lock_parent(entry);
2382 depth--;
2383 } while (entry && (depth >= 0));
2384}
2385
2386/*
2387 * printk the shortest lock dependencies from @leaf to @root.
2388 *
2389 * We have a lock dependency path (from a backwards search) as follow:
2390 *
2391 * @leaf @root
2392 * | |
2393 * V V
2394 * ->parent ->parent
2395 * | lock_list | ---------> | lock_list | ... | lock_list | ---------> | lock_list |
2396 * | L2 <- L1 | | L3 <- L2 | ... | Ln <- Ln-1 | | <- Ln |
2397 *
2398 * , so when we iterate from @leaf to @root, we actually print the lock
2399 * dependency path L1 -> L2 -> .. -> Ln in the non-reverse order.
2400 *
2401 * Another thing to notice here is that ->class of L2 <- L1 is L1, while the
2402 * ->trace of L2 <- L1 is the call trace of L2, in fact we don't have the call
2403 * trace of L1 in the dependency path, which is alright, because most of the
2404 * time we can figure out where L1 is held from the call trace of L2.
2405 */
2406static void __used
2407print_shortest_lock_dependencies_backwards(struct lock_list *leaf,
2408 struct lock_list *root)
2409{
2410 struct lock_list *entry = leaf;
2411 const struct lock_trace *trace = NULL;
2412 int depth;
2413
2414 /*compute depth from generated tree by BFS*/
2415 depth = get_lock_depth(leaf);
2416
2417 do {
2418 print_lock_class_header(entry->class, depth);
2419 if (trace) {
2420 printk("%*s ... acquired at:\n", depth, "");
2421 print_lock_trace(trace, 2);
2422 printk("\n");
2423 }
2424
2425 /*
2426 * Record the pointer to the trace for the next lock_list
2427 * entry, see the comments for the function.
2428 */
2429 trace = entry->trace;
2430
2431 if (depth == 0 && (entry != root)) {
2432 printk("lockdep:%s bad path found in chain graph\n", __func__);
2433 break;
2434 }
2435
2436 entry = get_lock_parent(entry);
2437 depth--;
2438 } while (entry && (depth >= 0));
2439}
2440
2441static void
2442print_irq_lock_scenario(struct lock_list *safe_entry,
2443 struct lock_list *unsafe_entry,
2444 struct lock_class *prev_class,
2445 struct lock_class *next_class)
2446{
2447 struct lock_class *safe_class = safe_entry->class;
2448 struct lock_class *unsafe_class = unsafe_entry->class;
2449 struct lock_class *middle_class = prev_class;
2450
2451 if (middle_class == safe_class)
2452 middle_class = next_class;
2453
2454 /*
2455 * A direct locking problem where unsafe_class lock is taken
2456 * directly by safe_class lock, then all we need to show
2457 * is the deadlock scenario, as it is obvious that the
2458 * unsafe lock is taken under the safe lock.
2459 *
2460 * But if there is a chain instead, where the safe lock takes
2461 * an intermediate lock (middle_class) where this lock is
2462 * not the same as the safe lock, then the lock chain is
2463 * used to describe the problem. Otherwise we would need
2464 * to show a different CPU case for each link in the chain
2465 * from the safe_class lock to the unsafe_class lock.
2466 */
2467 if (middle_class != unsafe_class) {
2468 printk("Chain exists of:\n ");
2469 __print_lock_name(safe_class);
2470 printk(KERN_CONT " --> ");
2471 __print_lock_name(middle_class);
2472 printk(KERN_CONT " --> ");
2473 __print_lock_name(unsafe_class);
2474 printk(KERN_CONT "\n\n");
2475 }
2476
2477 printk(" Possible interrupt unsafe locking scenario:\n\n");
2478 printk(" CPU0 CPU1\n");
2479 printk(" ---- ----\n");
2480 printk(" lock(");
2481 __print_lock_name(unsafe_class);
2482 printk(KERN_CONT ");\n");
2483 printk(" local_irq_disable();\n");
2484 printk(" lock(");
2485 __print_lock_name(safe_class);
2486 printk(KERN_CONT ");\n");
2487 printk(" lock(");
2488 __print_lock_name(middle_class);
2489 printk(KERN_CONT ");\n");
2490 printk(" <Interrupt>\n");
2491 printk(" lock(");
2492 __print_lock_name(safe_class);
2493 printk(KERN_CONT ");\n");
2494 printk("\n *** DEADLOCK ***\n\n");
2495}
2496
2497static void
2498print_bad_irq_dependency(struct task_struct *curr,
2499 struct lock_list *prev_root,
2500 struct lock_list *next_root,
2501 struct lock_list *backwards_entry,
2502 struct lock_list *forwards_entry,
2503 struct held_lock *prev,
2504 struct held_lock *next,
2505 enum lock_usage_bit bit1,
2506 enum lock_usage_bit bit2,
2507 const char *irqclass)
2508{
2509 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
2510 return;
2511
2512 pr_warn("\n");
2513 pr_warn("=====================================================\n");
2514 pr_warn("WARNING: %s-safe -> %s-unsafe lock order detected\n",
2515 irqclass, irqclass);
2516 print_kernel_ident();
2517 pr_warn("-----------------------------------------------------\n");
2518 pr_warn("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] is trying to acquire:\n",
2519 curr->comm, task_pid_nr(curr),
2520 lockdep_hardirq_context(), hardirq_count() >> HARDIRQ_SHIFT,
2521 curr->softirq_context, softirq_count() >> SOFTIRQ_SHIFT,
2522 lockdep_hardirqs_enabled(),
2523 curr->softirqs_enabled);
2524 print_lock(next);
2525
2526 pr_warn("\nand this task is already holding:\n");
2527 print_lock(prev);
2528 pr_warn("which would create a new lock dependency:\n");
2529 print_lock_name(hlock_class(prev));
2530 pr_cont(" ->");
2531 print_lock_name(hlock_class(next));
2532 pr_cont("\n");
2533
2534 pr_warn("\nbut this new dependency connects a %s-irq-safe lock:\n",
2535 irqclass);
2536 print_lock_name(backwards_entry->class);
2537 pr_warn("\n... which became %s-irq-safe at:\n", irqclass);
2538
2539 print_lock_trace(backwards_entry->class->usage_traces[bit1], 1);
2540
2541 pr_warn("\nto a %s-irq-unsafe lock:\n", irqclass);
2542 print_lock_name(forwards_entry->class);
2543 pr_warn("\n... which became %s-irq-unsafe at:\n", irqclass);
2544 pr_warn("...");
2545
2546 print_lock_trace(forwards_entry->class->usage_traces[bit2], 1);
2547
2548 pr_warn("\nother info that might help us debug this:\n\n");
2549 print_irq_lock_scenario(backwards_entry, forwards_entry,
2550 hlock_class(prev), hlock_class(next));
2551
2552 lockdep_print_held_locks(curr);
2553
2554 pr_warn("\nthe dependencies between %s-irq-safe lock and the holding lock:\n", irqclass);
2555 print_shortest_lock_dependencies_backwards(backwards_entry, prev_root);
2556
2557 pr_warn("\nthe dependencies between the lock to be acquired");
2558 pr_warn(" and %s-irq-unsafe lock:\n", irqclass);
2559 next_root->trace = save_trace();
2560 if (!next_root->trace)
2561 return;
2562 print_shortest_lock_dependencies(forwards_entry, next_root);
2563
2564 pr_warn("\nstack backtrace:\n");
2565 dump_stack();
2566}
2567
2568static const char *state_names[] = {
2569#define LOCKDEP_STATE(__STATE) \
2570 __stringify(__STATE),
2571#include "lockdep_states.h"
2572#undef LOCKDEP_STATE
2573};
2574
2575static const char *state_rnames[] = {
2576#define LOCKDEP_STATE(__STATE) \
2577 __stringify(__STATE)"-READ",
2578#include "lockdep_states.h"
2579#undef LOCKDEP_STATE
2580};
2581
2582static inline const char *state_name(enum lock_usage_bit bit)
2583{
2584 if (bit & LOCK_USAGE_READ_MASK)
2585 return state_rnames[bit >> LOCK_USAGE_DIR_MASK];
2586 else
2587 return state_names[bit >> LOCK_USAGE_DIR_MASK];
2588}
2589
2590/*
2591 * The bit number is encoded like:
2592 *
2593 * bit0: 0 exclusive, 1 read lock
2594 * bit1: 0 used in irq, 1 irq enabled
2595 * bit2-n: state
2596 */
2597static int exclusive_bit(int new_bit)
2598{
2599 int state = new_bit & LOCK_USAGE_STATE_MASK;
2600 int dir = new_bit & LOCK_USAGE_DIR_MASK;
2601
2602 /*
2603 * keep state, bit flip the direction and strip read.
2604 */
2605 return state | (dir ^ LOCK_USAGE_DIR_MASK);
2606}
2607
2608/*
2609 * Observe that when given a bitmask where each bitnr is encoded as above, a
2610 * right shift of the mask transforms the individual bitnrs as -1 and
2611 * conversely, a left shift transforms into +1 for the individual bitnrs.
2612 *
2613 * So for all bits whose number have LOCK_ENABLED_* set (bitnr1 == 1), we can
2614 * create the mask with those bit numbers using LOCK_USED_IN_* (bitnr1 == 0)
2615 * instead by subtracting the bit number by 2, or shifting the mask right by 2.
2616 *
2617 * Similarly, bitnr1 == 0 becomes bitnr1 == 1 by adding 2, or shifting left 2.
2618 *
2619 * So split the mask (note that LOCKF_ENABLED_IRQ_ALL|LOCKF_USED_IN_IRQ_ALL is
2620 * all bits set) and recompose with bitnr1 flipped.
2621 */
2622static unsigned long invert_dir_mask(unsigned long mask)
2623{
2624 unsigned long excl = 0;
2625
2626 /* Invert dir */
2627 excl |= (mask & LOCKF_ENABLED_IRQ_ALL) >> LOCK_USAGE_DIR_MASK;
2628 excl |= (mask & LOCKF_USED_IN_IRQ_ALL) << LOCK_USAGE_DIR_MASK;
2629
2630 return excl;
2631}
2632
2633/*
2634 * Note that a LOCK_ENABLED_IRQ_*_READ usage and a LOCK_USED_IN_IRQ_*_READ
2635 * usage may cause deadlock too, for example:
2636 *
2637 * P1 P2
2638 * <irq disabled>
2639 * write_lock(l1); <irq enabled>
2640 * read_lock(l2);
2641 * write_lock(l2);
2642 * <in irq>
2643 * read_lock(l1);
2644 *
2645 * , in above case, l1 will be marked as LOCK_USED_IN_IRQ_HARDIRQ_READ and l2
2646 * will marked as LOCK_ENABLE_IRQ_HARDIRQ_READ, and this is a possible
2647 * deadlock.
2648 *
2649 * In fact, all of the following cases may cause deadlocks:
2650 *
2651 * LOCK_USED_IN_IRQ_* -> LOCK_ENABLED_IRQ_*
2652 * LOCK_USED_IN_IRQ_*_READ -> LOCK_ENABLED_IRQ_*
2653 * LOCK_USED_IN_IRQ_* -> LOCK_ENABLED_IRQ_*_READ
2654 * LOCK_USED_IN_IRQ_*_READ -> LOCK_ENABLED_IRQ_*_READ
2655 *
2656 * As a result, to calculate the "exclusive mask", first we invert the
2657 * direction (USED_IN/ENABLED) of the original mask, and 1) for all bits with
2658 * bitnr0 set (LOCK_*_READ), add those with bitnr0 cleared (LOCK_*). 2) for all
2659 * bits with bitnr0 cleared (LOCK_*_READ), add those with bitnr0 set (LOCK_*).
2660 */
2661static unsigned long exclusive_mask(unsigned long mask)
2662{
2663 unsigned long excl = invert_dir_mask(mask);
2664
2665 excl |= (excl & LOCKF_IRQ_READ) >> LOCK_USAGE_READ_MASK;
2666 excl |= (excl & LOCKF_IRQ) << LOCK_USAGE_READ_MASK;
2667
2668 return excl;
2669}
2670
2671/*
2672 * Retrieve the _possible_ original mask to which @mask is
2673 * exclusive. Ie: this is the opposite of exclusive_mask().
2674 * Note that 2 possible original bits can match an exclusive
2675 * bit: one has LOCK_USAGE_READ_MASK set, the other has it
2676 * cleared. So both are returned for each exclusive bit.
2677 */
2678static unsigned long original_mask(unsigned long mask)
2679{
2680 unsigned long excl = invert_dir_mask(mask);
2681
2682 /* Include read in existing usages */
2683 excl |= (excl & LOCKF_IRQ_READ) >> LOCK_USAGE_READ_MASK;
2684 excl |= (excl & LOCKF_IRQ) << LOCK_USAGE_READ_MASK;
2685
2686 return excl;
2687}
2688
2689/*
2690 * Find the first pair of bit match between an original
2691 * usage mask and an exclusive usage mask.
2692 */
2693static int find_exclusive_match(unsigned long mask,
2694 unsigned long excl_mask,
2695 enum lock_usage_bit *bitp,
2696 enum lock_usage_bit *excl_bitp)
2697{
2698 int bit, excl, excl_read;
2699
2700 for_each_set_bit(bit, &mask, LOCK_USED) {
2701 /*
2702 * exclusive_bit() strips the read bit, however,
2703 * LOCK_ENABLED_IRQ_*_READ may cause deadlocks too, so we need
2704 * to search excl | LOCK_USAGE_READ_MASK as well.
2705 */
2706 excl = exclusive_bit(bit);
2707 excl_read = excl | LOCK_USAGE_READ_MASK;
2708 if (excl_mask & lock_flag(excl)) {
2709 *bitp = bit;
2710 *excl_bitp = excl;
2711 return 0;
2712 } else if (excl_mask & lock_flag(excl_read)) {
2713 *bitp = bit;
2714 *excl_bitp = excl_read;
2715 return 0;
2716 }
2717 }
2718 return -1;
2719}
2720
2721/*
2722 * Prove that the new dependency does not connect a hardirq-safe(-read)
2723 * lock with a hardirq-unsafe lock - to achieve this we search
2724 * the backwards-subgraph starting at <prev>, and the
2725 * forwards-subgraph starting at <next>:
2726 */
2727static int check_irq_usage(struct task_struct *curr, struct held_lock *prev,
2728 struct held_lock *next)
2729{
2730 unsigned long usage_mask = 0, forward_mask, backward_mask;
2731 enum lock_usage_bit forward_bit = 0, backward_bit = 0;
2732 struct lock_list *target_entry1;
2733 struct lock_list *target_entry;
2734 struct lock_list this, that;
2735 enum bfs_result ret;
2736
2737 /*
2738 * Step 1: gather all hard/soft IRQs usages backward in an
2739 * accumulated usage mask.
2740 */
2741 bfs_init_rootb(&this, prev);
2742
2743 ret = __bfs_backwards(&this, &usage_mask, usage_accumulate, usage_skip, NULL);
2744 if (bfs_error(ret)) {
2745 print_bfs_bug(ret);
2746 return 0;
2747 }
2748
2749 usage_mask &= LOCKF_USED_IN_IRQ_ALL;
2750 if (!usage_mask)
2751 return 1;
2752
2753 /*
2754 * Step 2: find exclusive uses forward that match the previous
2755 * backward accumulated mask.
2756 */
2757 forward_mask = exclusive_mask(usage_mask);
2758
2759 bfs_init_root(&that, next);
2760
2761 ret = find_usage_forwards(&that, forward_mask, &target_entry1);
2762 if (bfs_error(ret)) {
2763 print_bfs_bug(ret);
2764 return 0;
2765 }
2766 if (ret == BFS_RNOMATCH)
2767 return 1;
2768
2769 /*
2770 * Step 3: we found a bad match! Now retrieve a lock from the backward
2771 * list whose usage mask matches the exclusive usage mask from the
2772 * lock found on the forward list.
2773 *
2774 * Note, we should only keep the LOCKF_ENABLED_IRQ_ALL bits, considering
2775 * the follow case:
2776 *
2777 * When trying to add A -> B to the graph, we find that there is a
2778 * hardirq-safe L, that L -> ... -> A, and another hardirq-unsafe M,
2779 * that B -> ... -> M. However M is **softirq-safe**, if we use exact
2780 * invert bits of M's usage_mask, we will find another lock N that is
2781 * **softirq-unsafe** and N -> ... -> A, however N -> .. -> M will not
2782 * cause a inversion deadlock.
2783 */
2784 backward_mask = original_mask(target_entry1->class->usage_mask & LOCKF_ENABLED_IRQ_ALL);
2785
2786 ret = find_usage_backwards(&this, backward_mask, &target_entry);
2787 if (bfs_error(ret)) {
2788 print_bfs_bug(ret);
2789 return 0;
2790 }
2791 if (DEBUG_LOCKS_WARN_ON(ret == BFS_RNOMATCH))
2792 return 1;
2793
2794 /*
2795 * Step 4: narrow down to a pair of incompatible usage bits
2796 * and report it.
2797 */
2798 ret = find_exclusive_match(target_entry->class->usage_mask,
2799 target_entry1->class->usage_mask,
2800 &backward_bit, &forward_bit);
2801 if (DEBUG_LOCKS_WARN_ON(ret == -1))
2802 return 1;
2803
2804 print_bad_irq_dependency(curr, &this, &that,
2805 target_entry, target_entry1,
2806 prev, next,
2807 backward_bit, forward_bit,
2808 state_name(backward_bit));
2809
2810 return 0;
2811}
2812
2813#else
2814
2815static inline int check_irq_usage(struct task_struct *curr,
2816 struct held_lock *prev, struct held_lock *next)
2817{
2818 return 1;
2819}
2820
2821static inline bool usage_skip(struct lock_list *entry, void *mask)
2822{
2823 return false;
2824}
2825
2826#endif /* CONFIG_TRACE_IRQFLAGS */
2827
2828#ifdef CONFIG_LOCKDEP_SMALL
2829/*
2830 * Check that the dependency graph starting at <src> can lead to
2831 * <target> or not. If it can, <src> -> <target> dependency is already
2832 * in the graph.
2833 *
2834 * Return BFS_RMATCH if it does, or BFS_RNOMATCH if it does not, return BFS_E* if
2835 * any error appears in the bfs search.
2836 */
2837static noinline enum bfs_result
2838check_redundant(struct held_lock *src, struct held_lock *target)
2839{
2840 enum bfs_result ret;
2841 struct lock_list *target_entry;
2842 struct lock_list src_entry;
2843
2844 bfs_init_root(&src_entry, src);
2845 /*
2846 * Special setup for check_redundant().
2847 *
2848 * To report redundant, we need to find a strong dependency path that
2849 * is equal to or stronger than <src> -> <target>. So if <src> is E,
2850 * we need to let __bfs() only search for a path starting at a -(E*)->,
2851 * we achieve this by setting the initial node's ->only_xr to true in
2852 * that case. And if <prev> is S, we set initial ->only_xr to false
2853 * because both -(S*)-> (equal) and -(E*)-> (stronger) are redundant.
2854 */
2855 src_entry.only_xr = src->read == 0;
2856
2857 debug_atomic_inc(nr_redundant_checks);
2858
2859 /*
2860 * Note: we skip local_lock() for redundant check, because as the
2861 * comment in usage_skip(), A -> local_lock() -> B and A -> B are not
2862 * the same.
2863 */
2864 ret = check_path(target, &src_entry, hlock_equal, usage_skip, &target_entry);
2865
2866 if (ret == BFS_RMATCH)
2867 debug_atomic_inc(nr_redundant);
2868
2869 return ret;
2870}
2871
2872#else
2873
2874static inline enum bfs_result
2875check_redundant(struct held_lock *src, struct held_lock *target)
2876{
2877 return BFS_RNOMATCH;
2878}
2879
2880#endif
2881
2882static void inc_chains(int irq_context)
2883{
2884 if (irq_context & LOCK_CHAIN_HARDIRQ_CONTEXT)
2885 nr_hardirq_chains++;
2886 else if (irq_context & LOCK_CHAIN_SOFTIRQ_CONTEXT)
2887 nr_softirq_chains++;
2888 else
2889 nr_process_chains++;
2890}
2891
2892static void dec_chains(int irq_context)
2893{
2894 if (irq_context & LOCK_CHAIN_HARDIRQ_CONTEXT)
2895 nr_hardirq_chains--;
2896 else if (irq_context & LOCK_CHAIN_SOFTIRQ_CONTEXT)
2897 nr_softirq_chains--;
2898 else
2899 nr_process_chains--;
2900}
2901
2902static void
2903print_deadlock_scenario(struct held_lock *nxt, struct held_lock *prv)
2904{
2905 struct lock_class *next = hlock_class(nxt);
2906 struct lock_class *prev = hlock_class(prv);
2907
2908 printk(" Possible unsafe locking scenario:\n\n");
2909 printk(" CPU0\n");
2910 printk(" ----\n");
2911 printk(" lock(");
2912 __print_lock_name(prev);
2913 printk(KERN_CONT ");\n");
2914 printk(" lock(");
2915 __print_lock_name(next);
2916 printk(KERN_CONT ");\n");
2917 printk("\n *** DEADLOCK ***\n\n");
2918 printk(" May be due to missing lock nesting notation\n\n");
2919}
2920
2921static void
2922print_deadlock_bug(struct task_struct *curr, struct held_lock *prev,
2923 struct held_lock *next)
2924{
2925 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
2926 return;
2927
2928 pr_warn("\n");
2929 pr_warn("============================================\n");
2930 pr_warn("WARNING: possible recursive locking detected\n");
2931 print_kernel_ident();
2932 pr_warn("--------------------------------------------\n");
2933 pr_warn("%s/%d is trying to acquire lock:\n",
2934 curr->comm, task_pid_nr(curr));
2935 print_lock(next);
2936 pr_warn("\nbut task is already holding lock:\n");
2937 print_lock(prev);
2938
2939 pr_warn("\nother info that might help us debug this:\n");
2940 print_deadlock_scenario(next, prev);
2941 lockdep_print_held_locks(curr);
2942
2943 pr_warn("\nstack backtrace:\n");
2944 dump_stack();
2945}
2946
2947/*
2948 * Check whether we are holding such a class already.
2949 *
2950 * (Note that this has to be done separately, because the graph cannot
2951 * detect such classes of deadlocks.)
2952 *
2953 * Returns: 0 on deadlock detected, 1 on OK, 2 if another lock with the same
2954 * lock class is held but nest_lock is also held, i.e. we rely on the
2955 * nest_lock to avoid the deadlock.
2956 */
2957static int
2958check_deadlock(struct task_struct *curr, struct held_lock *next)
2959{
2960 struct held_lock *prev;
2961 struct held_lock *nest = NULL;
2962 int i;
2963
2964 for (i = 0; i < curr->lockdep_depth; i++) {
2965 prev = curr->held_locks + i;
2966
2967 if (prev->instance == next->nest_lock)
2968 nest = prev;
2969
2970 if (hlock_class(prev) != hlock_class(next))
2971 continue;
2972
2973 /*
2974 * Allow read-after-read recursion of the same
2975 * lock class (i.e. read_lock(lock)+read_lock(lock)):
2976 */
2977 if ((next->read == 2) && prev->read)
2978 continue;
2979
2980 /*
2981 * We're holding the nest_lock, which serializes this lock's
2982 * nesting behaviour.
2983 */
2984 if (nest)
2985 return 2;
2986
2987 print_deadlock_bug(curr, prev, next);
2988 return 0;
2989 }
2990 return 1;
2991}
2992
2993/*
2994 * There was a chain-cache miss, and we are about to add a new dependency
2995 * to a previous lock. We validate the following rules:
2996 *
2997 * - would the adding of the <prev> -> <next> dependency create a
2998 * circular dependency in the graph? [== circular deadlock]
2999 *
3000 * - does the new prev->next dependency connect any hardirq-safe lock
3001 * (in the full backwards-subgraph starting at <prev>) with any
3002 * hardirq-unsafe lock (in the full forwards-subgraph starting at
3003 * <next>)? [== illegal lock inversion with hardirq contexts]
3004 *
3005 * - does the new prev->next dependency connect any softirq-safe lock
3006 * (in the full backwards-subgraph starting at <prev>) with any
3007 * softirq-unsafe lock (in the full forwards-subgraph starting at
3008 * <next>)? [== illegal lock inversion with softirq contexts]
3009 *
3010 * any of these scenarios could lead to a deadlock.
3011 *
3012 * Then if all the validations pass, we add the forwards and backwards
3013 * dependency.
3014 */
3015static int
3016check_prev_add(struct task_struct *curr, struct held_lock *prev,
3017 struct held_lock *next, u16 distance,
3018 struct lock_trace **const trace)
3019{
3020 struct lock_list *entry;
3021 enum bfs_result ret;
3022
3023 if (!hlock_class(prev)->key || !hlock_class(next)->key) {
3024 /*
3025 * The warning statements below may trigger a use-after-free
3026 * of the class name. It is better to trigger a use-after free
3027 * and to have the class name most of the time instead of not
3028 * having the class name available.
3029 */
3030 WARN_ONCE(!debug_locks_silent && !hlock_class(prev)->key,
3031 "Detected use-after-free of lock class %px/%s\n",
3032 hlock_class(prev),
3033 hlock_class(prev)->name);
3034 WARN_ONCE(!debug_locks_silent && !hlock_class(next)->key,
3035 "Detected use-after-free of lock class %px/%s\n",
3036 hlock_class(next),
3037 hlock_class(next)->name);
3038 return 2;
3039 }
3040
3041 /*
3042 * Prove that the new <prev> -> <next> dependency would not
3043 * create a circular dependency in the graph. (We do this by
3044 * a breadth-first search into the graph starting at <next>,
3045 * and check whether we can reach <prev>.)
3046 *
3047 * The search is limited by the size of the circular queue (i.e.,
3048 * MAX_CIRCULAR_QUEUE_SIZE) which keeps track of a breadth of nodes
3049 * in the graph whose neighbours are to be checked.
3050 */
3051 ret = check_noncircular(next, prev, trace);
3052 if (unlikely(bfs_error(ret) || ret == BFS_RMATCH))
3053 return 0;
3054
3055 if (!check_irq_usage(curr, prev, next))
3056 return 0;
3057
3058 /*
3059 * Is the <prev> -> <next> dependency already present?
3060 *
3061 * (this may occur even though this is a new chain: consider
3062 * e.g. the L1 -> L2 -> L3 -> L4 and the L5 -> L1 -> L2 -> L3
3063 * chains - the second one will be new, but L1 already has
3064 * L2 added to its dependency list, due to the first chain.)
3065 */
3066 list_for_each_entry(entry, &hlock_class(prev)->locks_after, entry) {
3067 if (entry->class == hlock_class(next)) {
3068 if (distance == 1)
3069 entry->distance = 1;
3070 entry->dep |= calc_dep(prev, next);
3071
3072 /*
3073 * Also, update the reverse dependency in @next's
3074 * ->locks_before list.
3075 *
3076 * Here we reuse @entry as the cursor, which is fine
3077 * because we won't go to the next iteration of the
3078 * outer loop:
3079 *
3080 * For normal cases, we return in the inner loop.
3081 *
3082 * If we fail to return, we have inconsistency, i.e.
3083 * <prev>::locks_after contains <next> while
3084 * <next>::locks_before doesn't contain <prev>. In
3085 * that case, we return after the inner and indicate
3086 * something is wrong.
3087 */
3088 list_for_each_entry(entry, &hlock_class(next)->locks_before, entry) {
3089 if (entry->class == hlock_class(prev)) {
3090 if (distance == 1)
3091 entry->distance = 1;
3092 entry->dep |= calc_depb(prev, next);
3093 return 1;
3094 }
3095 }
3096
3097 /* <prev> is not found in <next>::locks_before */
3098 return 0;
3099 }
3100 }
3101
3102 /*
3103 * Is the <prev> -> <next> link redundant?
3104 */
3105 ret = check_redundant(prev, next);
3106 if (bfs_error(ret))
3107 return 0;
3108 else if (ret == BFS_RMATCH)
3109 return 2;
3110
3111 if (!*trace) {
3112 *trace = save_trace();
3113 if (!*trace)
3114 return 0;
3115 }
3116
3117 /*
3118 * Ok, all validations passed, add the new lock
3119 * to the previous lock's dependency list:
3120 */
3121 ret = add_lock_to_list(hlock_class(next), hlock_class(prev),
3122 &hlock_class(prev)->locks_after,
3123 next->acquire_ip, distance,
3124 calc_dep(prev, next),
3125 *trace);
3126
3127 if (!ret)
3128 return 0;
3129
3130 ret = add_lock_to_list(hlock_class(prev), hlock_class(next),
3131 &hlock_class(next)->locks_before,
3132 next->acquire_ip, distance,
3133 calc_depb(prev, next),
3134 *trace);
3135 if (!ret)
3136 return 0;
3137
3138 return 2;
3139}
3140
3141/*
3142 * Add the dependency to all directly-previous locks that are 'relevant'.
3143 * The ones that are relevant are (in increasing distance from curr):
3144 * all consecutive trylock entries and the final non-trylock entry - or
3145 * the end of this context's lock-chain - whichever comes first.
3146 */
3147static int
3148check_prevs_add(struct task_struct *curr, struct held_lock *next)
3149{
3150 struct lock_trace *trace = NULL;
3151 int depth = curr->lockdep_depth;
3152 struct held_lock *hlock;
3153
3154 /*
3155 * Debugging checks.
3156 *
3157 * Depth must not be zero for a non-head lock:
3158 */
3159 if (!depth)
3160 goto out_bug;
3161 /*
3162 * At least two relevant locks must exist for this
3163 * to be a head:
3164 */
3165 if (curr->held_locks[depth].irq_context !=
3166 curr->held_locks[depth-1].irq_context)
3167 goto out_bug;
3168
3169 for (;;) {
3170 u16 distance = curr->lockdep_depth - depth + 1;
3171 hlock = curr->held_locks + depth - 1;
3172
3173 if (hlock->check) {
3174 int ret = check_prev_add(curr, hlock, next, distance, &trace);
3175 if (!ret)
3176 return 0;
3177
3178 /*
3179 * Stop after the first non-trylock entry,
3180 * as non-trylock entries have added their
3181 * own direct dependencies already, so this
3182 * lock is connected to them indirectly:
3183 */
3184 if (!hlock->trylock)
3185 break;
3186 }
3187
3188 depth--;
3189 /*
3190 * End of lock-stack?
3191 */
3192 if (!depth)
3193 break;
3194 /*
3195 * Stop the search if we cross into another context:
3196 */
3197 if (curr->held_locks[depth].irq_context !=
3198 curr->held_locks[depth-1].irq_context)
3199 break;
3200 }
3201 return 1;
3202out_bug:
3203 if (!debug_locks_off_graph_unlock())
3204 return 0;
3205
3206 /*
3207 * Clearly we all shouldn't be here, but since we made it we
3208 * can reliable say we messed up our state. See the above two
3209 * gotos for reasons why we could possibly end up here.
3210 */
3211 WARN_ON(1);
3212
3213 return 0;
3214}
3215
3216struct lock_chain lock_chains[MAX_LOCKDEP_CHAINS];
3217static DECLARE_BITMAP(lock_chains_in_use, MAX_LOCKDEP_CHAINS);
3218static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
3219unsigned long nr_zapped_lock_chains;
3220unsigned int nr_free_chain_hlocks; /* Free chain_hlocks in buckets */
3221unsigned int nr_lost_chain_hlocks; /* Lost chain_hlocks */
3222unsigned int nr_large_chain_blocks; /* size > MAX_CHAIN_BUCKETS */
3223
3224/*
3225 * The first 2 chain_hlocks entries in the chain block in the bucket
3226 * list contains the following meta data:
3227 *
3228 * entry[0]:
3229 * Bit 15 - always set to 1 (it is not a class index)
3230 * Bits 0-14 - upper 15 bits of the next block index
3231 * entry[1] - lower 16 bits of next block index
3232 *
3233 * A next block index of all 1 bits means it is the end of the list.
3234 *
3235 * On the unsized bucket (bucket-0), the 3rd and 4th entries contain
3236 * the chain block size:
3237 *
3238 * entry[2] - upper 16 bits of the chain block size
3239 * entry[3] - lower 16 bits of the chain block size
3240 */
3241#define MAX_CHAIN_BUCKETS 16
3242#define CHAIN_BLK_FLAG (1U << 15)
3243#define CHAIN_BLK_LIST_END 0xFFFFU
3244
3245static int chain_block_buckets[MAX_CHAIN_BUCKETS];
3246
3247static inline int size_to_bucket(int size)
3248{
3249 if (size > MAX_CHAIN_BUCKETS)
3250 return 0;
3251
3252 return size - 1;
3253}
3254
3255/*
3256 * Iterate all the chain blocks in a bucket.
3257 */
3258#define for_each_chain_block(bucket, prev, curr) \
3259 for ((prev) = -1, (curr) = chain_block_buckets[bucket]; \
3260 (curr) >= 0; \
3261 (prev) = (curr), (curr) = chain_block_next(curr))
3262
3263/*
3264 * next block or -1
3265 */
3266static inline int chain_block_next(int offset)
3267{
3268 int next = chain_hlocks[offset];
3269
3270 WARN_ON_ONCE(!(next & CHAIN_BLK_FLAG));
3271
3272 if (next == CHAIN_BLK_LIST_END)
3273 return -1;
3274
3275 next &= ~CHAIN_BLK_FLAG;
3276 next <<= 16;
3277 next |= chain_hlocks[offset + 1];
3278
3279 return next;
3280}
3281
3282/*
3283 * bucket-0 only
3284 */
3285static inline int chain_block_size(int offset)
3286{
3287 return (chain_hlocks[offset + 2] << 16) | chain_hlocks[offset + 3];
3288}
3289
3290static inline void init_chain_block(int offset, int next, int bucket, int size)
3291{
3292 chain_hlocks[offset] = (next >> 16) | CHAIN_BLK_FLAG;
3293 chain_hlocks[offset + 1] = (u16)next;
3294
3295 if (size && !bucket) {
3296 chain_hlocks[offset + 2] = size >> 16;
3297 chain_hlocks[offset + 3] = (u16)size;
3298 }
3299}
3300
3301static inline void add_chain_block(int offset, int size)
3302{
3303 int bucket = size_to_bucket(size);
3304 int next = chain_block_buckets[bucket];
3305 int prev, curr;
3306
3307 if (unlikely(size < 2)) {
3308 /*
3309 * We can't store single entries on the freelist. Leak them.
3310 *
3311 * One possible way out would be to uniquely mark them, other
3312 * than with CHAIN_BLK_FLAG, such that we can recover them when
3313 * the block before it is re-added.
3314 */
3315 if (size)
3316 nr_lost_chain_hlocks++;
3317 return;
3318 }
3319
3320 nr_free_chain_hlocks += size;
3321 if (!bucket) {
3322 nr_large_chain_blocks++;
3323
3324 /*
3325 * Variable sized, sort large to small.
3326 */
3327 for_each_chain_block(0, prev, curr) {
3328 if (size >= chain_block_size(curr))
3329 break;
3330 }
3331 init_chain_block(offset, curr, 0, size);
3332 if (prev < 0)
3333 chain_block_buckets[0] = offset;
3334 else
3335 init_chain_block(prev, offset, 0, 0);
3336 return;
3337 }
3338 /*
3339 * Fixed size, add to head.
3340 */
3341 init_chain_block(offset, next, bucket, size);
3342 chain_block_buckets[bucket] = offset;
3343}
3344
3345/*
3346 * Only the first block in the list can be deleted.
3347 *
3348 * For the variable size bucket[0], the first block (the largest one) is
3349 * returned, broken up and put back into the pool. So if a chain block of
3350 * length > MAX_CHAIN_BUCKETS is ever used and zapped, it will just be
3351 * queued up after the primordial chain block and never be used until the
3352 * hlock entries in the primordial chain block is almost used up. That
3353 * causes fragmentation and reduce allocation efficiency. That can be
3354 * monitored by looking at the "large chain blocks" number in lockdep_stats.
3355 */
3356static inline void del_chain_block(int bucket, int size, int next)
3357{
3358 nr_free_chain_hlocks -= size;
3359 chain_block_buckets[bucket] = next;
3360
3361 if (!bucket)
3362 nr_large_chain_blocks--;
3363}
3364
3365static void init_chain_block_buckets(void)
3366{
3367 int i;
3368
3369 for (i = 0; i < MAX_CHAIN_BUCKETS; i++)
3370 chain_block_buckets[i] = -1;
3371
3372 add_chain_block(0, ARRAY_SIZE(chain_hlocks));
3373}
3374
3375/*
3376 * Return offset of a chain block of the right size or -1 if not found.
3377 *
3378 * Fairly simple worst-fit allocator with the addition of a number of size
3379 * specific free lists.
3380 */
3381static int alloc_chain_hlocks(int req)
3382{
3383 int bucket, curr, size;
3384
3385 /*
3386 * We rely on the MSB to act as an escape bit to denote freelist
3387 * pointers. Make sure this bit isn't set in 'normal' class_idx usage.
3388 */
3389 BUILD_BUG_ON((MAX_LOCKDEP_KEYS-1) & CHAIN_BLK_FLAG);
3390
3391 init_data_structures_once();
3392
3393 if (nr_free_chain_hlocks < req)
3394 return -1;
3395
3396 /*
3397 * We require a minimum of 2 (u16) entries to encode a freelist
3398 * 'pointer'.
3399 */
3400 req = max(req, 2);
3401 bucket = size_to_bucket(req);
3402 curr = chain_block_buckets[bucket];
3403
3404 if (bucket) {
3405 if (curr >= 0) {
3406 del_chain_block(bucket, req, chain_block_next(curr));
3407 return curr;
3408 }
3409 /* Try bucket 0 */
3410 curr = chain_block_buckets[0];
3411 }
3412
3413 /*
3414 * The variable sized freelist is sorted by size; the first entry is
3415 * the largest. Use it if it fits.
3416 */
3417 if (curr >= 0) {
3418 size = chain_block_size(curr);
3419 if (likely(size >= req)) {
3420 del_chain_block(0, size, chain_block_next(curr));
3421 add_chain_block(curr + req, size - req);
3422 return curr;
3423 }
3424 }
3425
3426 /*
3427 * Last resort, split a block in a larger sized bucket.
3428 */
3429 for (size = MAX_CHAIN_BUCKETS; size > req; size--) {
3430 bucket = size_to_bucket(size);
3431 curr = chain_block_buckets[bucket];
3432 if (curr < 0)
3433 continue;
3434
3435 del_chain_block(bucket, size, chain_block_next(curr));
3436 add_chain_block(curr + req, size - req);
3437 return curr;
3438 }
3439
3440 return -1;
3441}
3442
3443static inline void free_chain_hlocks(int base, int size)
3444{
3445 add_chain_block(base, max(size, 2));
3446}
3447
3448struct lock_class *lock_chain_get_class(struct lock_chain *chain, int i)
3449{
3450 u16 chain_hlock = chain_hlocks[chain->base + i];
3451 unsigned int class_idx = chain_hlock_class_idx(chain_hlock);
3452
3453 return lock_classes + class_idx - 1;
3454}
3455
3456/*
3457 * Returns the index of the first held_lock of the current chain
3458 */
3459static inline int get_first_held_lock(struct task_struct *curr,
3460 struct held_lock *hlock)
3461{
3462 int i;
3463 struct held_lock *hlock_curr;
3464
3465 for (i = curr->lockdep_depth - 1; i >= 0; i--) {
3466 hlock_curr = curr->held_locks + i;
3467 if (hlock_curr->irq_context != hlock->irq_context)
3468 break;
3469
3470 }
3471
3472 return ++i;
3473}
3474
3475#ifdef CONFIG_DEBUG_LOCKDEP
3476/*
3477 * Returns the next chain_key iteration
3478 */
3479static u64 print_chain_key_iteration(u16 hlock_id, u64 chain_key)
3480{
3481 u64 new_chain_key = iterate_chain_key(chain_key, hlock_id);
3482
3483 printk(" hlock_id:%d -> chain_key:%016Lx",
3484 (unsigned int)hlock_id,
3485 (unsigned long long)new_chain_key);
3486 return new_chain_key;
3487}
3488
3489static void
3490print_chain_keys_held_locks(struct task_struct *curr, struct held_lock *hlock_next)
3491{
3492 struct held_lock *hlock;
3493 u64 chain_key = INITIAL_CHAIN_KEY;
3494 int depth = curr->lockdep_depth;
3495 int i = get_first_held_lock(curr, hlock_next);
3496
3497 printk("depth: %u (irq_context %u)\n", depth - i + 1,
3498 hlock_next->irq_context);
3499 for (; i < depth; i++) {
3500 hlock = curr->held_locks + i;
3501 chain_key = print_chain_key_iteration(hlock_id(hlock), chain_key);
3502
3503 print_lock(hlock);
3504 }
3505
3506 print_chain_key_iteration(hlock_id(hlock_next), chain_key);
3507 print_lock(hlock_next);
3508}
3509
3510static void print_chain_keys_chain(struct lock_chain *chain)
3511{
3512 int i;
3513 u64 chain_key = INITIAL_CHAIN_KEY;
3514 u16 hlock_id;
3515
3516 printk("depth: %u\n", chain->depth);
3517 for (i = 0; i < chain->depth; i++) {
3518 hlock_id = chain_hlocks[chain->base + i];
3519 chain_key = print_chain_key_iteration(hlock_id, chain_key);
3520
3521 print_lock_name(lock_classes + chain_hlock_class_idx(hlock_id) - 1);
3522 printk("\n");
3523 }
3524}
3525
3526static void print_collision(struct task_struct *curr,
3527 struct held_lock *hlock_next,
3528 struct lock_chain *chain)
3529{
3530 pr_warn("\n");
3531 pr_warn("============================\n");
3532 pr_warn("WARNING: chain_key collision\n");
3533 print_kernel_ident();
3534 pr_warn("----------------------------\n");
3535 pr_warn("%s/%d: ", current->comm, task_pid_nr(current));
3536 pr_warn("Hash chain already cached but the contents don't match!\n");
3537
3538 pr_warn("Held locks:");
3539 print_chain_keys_held_locks(curr, hlock_next);
3540
3541 pr_warn("Locks in cached chain:");
3542 print_chain_keys_chain(chain);
3543
3544 pr_warn("\nstack backtrace:\n");
3545 dump_stack();
3546}
3547#endif
3548
3549/*
3550 * Checks whether the chain and the current held locks are consistent
3551 * in depth and also in content. If they are not it most likely means
3552 * that there was a collision during the calculation of the chain_key.
3553 * Returns: 0 not passed, 1 passed
3554 */
3555static int check_no_collision(struct task_struct *curr,
3556 struct held_lock *hlock,
3557 struct lock_chain *chain)
3558{
3559#ifdef CONFIG_DEBUG_LOCKDEP
3560 int i, j, id;
3561
3562 i = get_first_held_lock(curr, hlock);
3563
3564 if (DEBUG_LOCKS_WARN_ON(chain->depth != curr->lockdep_depth - (i - 1))) {
3565 print_collision(curr, hlock, chain);
3566 return 0;
3567 }
3568
3569 for (j = 0; j < chain->depth - 1; j++, i++) {
3570 id = hlock_id(&curr->held_locks[i]);
3571
3572 if (DEBUG_LOCKS_WARN_ON(chain_hlocks[chain->base + j] != id)) {
3573 print_collision(curr, hlock, chain);
3574 return 0;
3575 }
3576 }
3577#endif
3578 return 1;
3579}
3580
3581/*
3582 * Given an index that is >= -1, return the index of the next lock chain.
3583 * Return -2 if there is no next lock chain.
3584 */
3585long lockdep_next_lockchain(long i)
3586{
3587 i = find_next_bit(lock_chains_in_use, ARRAY_SIZE(lock_chains), i + 1);
3588 return i < ARRAY_SIZE(lock_chains) ? i : -2;
3589}
3590
3591unsigned long lock_chain_count(void)
3592{
3593 return bitmap_weight(lock_chains_in_use, ARRAY_SIZE(lock_chains));
3594}
3595
3596/* Must be called with the graph lock held. */
3597static struct lock_chain *alloc_lock_chain(void)
3598{
3599 int idx = find_first_zero_bit(lock_chains_in_use,
3600 ARRAY_SIZE(lock_chains));
3601
3602 if (unlikely(idx >= ARRAY_SIZE(lock_chains)))
3603 return NULL;
3604 __set_bit(idx, lock_chains_in_use);
3605 return lock_chains + idx;
3606}
3607
3608/*
3609 * Adds a dependency chain into chain hashtable. And must be called with
3610 * graph_lock held.
3611 *
3612 * Return 0 if fail, and graph_lock is released.
3613 * Return 1 if succeed, with graph_lock held.
3614 */
3615static inline int add_chain_cache(struct task_struct *curr,
3616 struct held_lock *hlock,
3617 u64 chain_key)
3618{
3619 struct hlist_head *hash_head = chainhashentry(chain_key);
3620 struct lock_chain *chain;
3621 int i, j;
3622
3623 /*
3624 * The caller must hold the graph lock, ensure we've got IRQs
3625 * disabled to make this an IRQ-safe lock.. for recursion reasons
3626 * lockdep won't complain about its own locking errors.
3627 */
3628 if (lockdep_assert_locked())
3629 return 0;
3630
3631 chain = alloc_lock_chain();
3632 if (!chain) {
3633 if (!debug_locks_off_graph_unlock())
3634 return 0;
3635
3636 print_lockdep_off("BUG: MAX_LOCKDEP_CHAINS too low!");
3637 dump_stack();
3638 return 0;
3639 }
3640 chain->chain_key = chain_key;
3641 chain->irq_context = hlock->irq_context;
3642 i = get_first_held_lock(curr, hlock);
3643 chain->depth = curr->lockdep_depth + 1 - i;
3644
3645 BUILD_BUG_ON((1UL << 24) <= ARRAY_SIZE(chain_hlocks));
3646 BUILD_BUG_ON((1UL << 6) <= ARRAY_SIZE(curr->held_locks));
3647 BUILD_BUG_ON((1UL << 8*sizeof(chain_hlocks[0])) <= ARRAY_SIZE(lock_classes));
3648
3649 j = alloc_chain_hlocks(chain->depth);
3650 if (j < 0) {
3651 if (!debug_locks_off_graph_unlock())
3652 return 0;
3653
3654 print_lockdep_off("BUG: MAX_LOCKDEP_CHAIN_HLOCKS too low!");
3655 dump_stack();
3656 return 0;
3657 }
3658
3659 chain->base = j;
3660 for (j = 0; j < chain->depth - 1; j++, i++) {
3661 int lock_id = hlock_id(curr->held_locks + i);
3662
3663 chain_hlocks[chain->base + j] = lock_id;
3664 }
3665 chain_hlocks[chain->base + j] = hlock_id(hlock);
3666 hlist_add_head_rcu(&chain->entry, hash_head);
3667 debug_atomic_inc(chain_lookup_misses);
3668 inc_chains(chain->irq_context);
3669
3670 return 1;
3671}
3672
3673/*
3674 * Look up a dependency chain. Must be called with either the graph lock or
3675 * the RCU read lock held.
3676 */
3677static inline struct lock_chain *lookup_chain_cache(u64 chain_key)
3678{
3679 struct hlist_head *hash_head = chainhashentry(chain_key);
3680 struct lock_chain *chain;
3681
3682 hlist_for_each_entry_rcu(chain, hash_head, entry) {
3683 if (READ_ONCE(chain->chain_key) == chain_key) {
3684 debug_atomic_inc(chain_lookup_hits);
3685 return chain;
3686 }
3687 }
3688 return NULL;
3689}
3690
3691/*
3692 * If the key is not present yet in dependency chain cache then
3693 * add it and return 1 - in this case the new dependency chain is
3694 * validated. If the key is already hashed, return 0.
3695 * (On return with 1 graph_lock is held.)
3696 */
3697static inline int lookup_chain_cache_add(struct task_struct *curr,
3698 struct held_lock *hlock,
3699 u64 chain_key)
3700{
3701 struct lock_class *class = hlock_class(hlock);
3702 struct lock_chain *chain = lookup_chain_cache(chain_key);
3703
3704 if (chain) {
3705cache_hit:
3706 if (!check_no_collision(curr, hlock, chain))
3707 return 0;
3708
3709 if (very_verbose(class)) {
3710 printk("\nhash chain already cached, key: "
3711 "%016Lx tail class: [%px] %s\n",
3712 (unsigned long long)chain_key,
3713 class->key, class->name);
3714 }
3715
3716 return 0;
3717 }
3718
3719 if (very_verbose(class)) {
3720 printk("\nnew hash chain, key: %016Lx tail class: [%px] %s\n",
3721 (unsigned long long)chain_key, class->key, class->name);
3722 }
3723
3724 if (!graph_lock())
3725 return 0;
3726
3727 /*
3728 * We have to walk the chain again locked - to avoid duplicates:
3729 */
3730 chain = lookup_chain_cache(chain_key);
3731 if (chain) {
3732 graph_unlock();
3733 goto cache_hit;
3734 }
3735
3736 if (!add_chain_cache(curr, hlock, chain_key))
3737 return 0;
3738
3739 return 1;
3740}
3741
3742static int validate_chain(struct task_struct *curr,
3743 struct held_lock *hlock,
3744 int chain_head, u64 chain_key)
3745{
3746 /*
3747 * Trylock needs to maintain the stack of held locks, but it
3748 * does not add new dependencies, because trylock can be done
3749 * in any order.
3750 *
3751 * We look up the chain_key and do the O(N^2) check and update of
3752 * the dependencies only if this is a new dependency chain.
3753 * (If lookup_chain_cache_add() return with 1 it acquires
3754 * graph_lock for us)
3755 */
3756 if (!hlock->trylock && hlock->check &&
3757 lookup_chain_cache_add(curr, hlock, chain_key)) {
3758 /*
3759 * Check whether last held lock:
3760 *
3761 * - is irq-safe, if this lock is irq-unsafe
3762 * - is softirq-safe, if this lock is hardirq-unsafe
3763 *
3764 * And check whether the new lock's dependency graph
3765 * could lead back to the previous lock:
3766 *
3767 * - within the current held-lock stack
3768 * - across our accumulated lock dependency records
3769 *
3770 * any of these scenarios could lead to a deadlock.
3771 */
3772 /*
3773 * The simple case: does the current hold the same lock
3774 * already?
3775 */
3776 int ret = check_deadlock(curr, hlock);
3777
3778 if (!ret)
3779 return 0;
3780 /*
3781 * Add dependency only if this lock is not the head
3782 * of the chain, and if the new lock introduces no more
3783 * lock dependency (because we already hold a lock with the
3784 * same lock class) nor deadlock (because the nest_lock
3785 * serializes nesting locks), see the comments for
3786 * check_deadlock().
3787 */
3788 if (!chain_head && ret != 2) {
3789 if (!check_prevs_add(curr, hlock))
3790 return 0;
3791 }
3792
3793 graph_unlock();
3794 } else {
3795 /* after lookup_chain_cache_add(): */
3796 if (unlikely(!debug_locks))
3797 return 0;
3798 }
3799
3800 return 1;
3801}
3802#else
3803static inline int validate_chain(struct task_struct *curr,
3804 struct held_lock *hlock,
3805 int chain_head, u64 chain_key)
3806{
3807 return 1;
3808}
3809
3810static void init_chain_block_buckets(void) { }
3811#endif /* CONFIG_PROVE_LOCKING */
3812
3813/*
3814 * We are building curr_chain_key incrementally, so double-check
3815 * it from scratch, to make sure that it's done correctly:
3816 */
3817static void check_chain_key(struct task_struct *curr)
3818{
3819#ifdef CONFIG_DEBUG_LOCKDEP
3820 struct held_lock *hlock, *prev_hlock = NULL;
3821 unsigned int i;
3822 u64 chain_key = INITIAL_CHAIN_KEY;
3823
3824 for (i = 0; i < curr->lockdep_depth; i++) {
3825 hlock = curr->held_locks + i;
3826 if (chain_key != hlock->prev_chain_key) {
3827 debug_locks_off();
3828 /*
3829 * We got mighty confused, our chain keys don't match
3830 * with what we expect, someone trample on our task state?
3831 */
3832 WARN(1, "hm#1, depth: %u [%u], %016Lx != %016Lx\n",
3833 curr->lockdep_depth, i,
3834 (unsigned long long)chain_key,
3835 (unsigned long long)hlock->prev_chain_key);
3836 return;
3837 }
3838
3839 /*
3840 * hlock->class_idx can't go beyond MAX_LOCKDEP_KEYS, but is
3841 * it registered lock class index?
3842 */
3843 if (DEBUG_LOCKS_WARN_ON(!test_bit(hlock->class_idx, lock_classes_in_use)))
3844 return;
3845
3846 if (prev_hlock && (prev_hlock->irq_context !=
3847 hlock->irq_context))
3848 chain_key = INITIAL_CHAIN_KEY;
3849 chain_key = iterate_chain_key(chain_key, hlock_id(hlock));
3850 prev_hlock = hlock;
3851 }
3852 if (chain_key != curr->curr_chain_key) {
3853 debug_locks_off();
3854 /*
3855 * More smoking hash instead of calculating it, damn see these
3856 * numbers float.. I bet that a pink elephant stepped on my memory.
3857 */
3858 WARN(1, "hm#2, depth: %u [%u], %016Lx != %016Lx\n",
3859 curr->lockdep_depth, i,
3860 (unsigned long long)chain_key,
3861 (unsigned long long)curr->curr_chain_key);
3862 }
3863#endif
3864}
3865
3866#ifdef CONFIG_PROVE_LOCKING
3867static int mark_lock(struct task_struct *curr, struct held_lock *this,
3868 enum lock_usage_bit new_bit);
3869
3870static void print_usage_bug_scenario(struct held_lock *lock)
3871{
3872 struct lock_class *class = hlock_class(lock);
3873
3874 printk(" Possible unsafe locking scenario:\n\n");
3875 printk(" CPU0\n");
3876 printk(" ----\n");
3877 printk(" lock(");
3878 __print_lock_name(class);
3879 printk(KERN_CONT ");\n");
3880 printk(" <Interrupt>\n");
3881 printk(" lock(");
3882 __print_lock_name(class);
3883 printk(KERN_CONT ");\n");
3884 printk("\n *** DEADLOCK ***\n\n");
3885}
3886
3887static void
3888print_usage_bug(struct task_struct *curr, struct held_lock *this,
3889 enum lock_usage_bit prev_bit, enum lock_usage_bit new_bit)
3890{
3891 if (!debug_locks_off() || debug_locks_silent)
3892 return;
3893
3894 pr_warn("\n");
3895 pr_warn("================================\n");
3896 pr_warn("WARNING: inconsistent lock state\n");
3897 print_kernel_ident();
3898 pr_warn("--------------------------------\n");
3899
3900 pr_warn("inconsistent {%s} -> {%s} usage.\n",
3901 usage_str[prev_bit], usage_str[new_bit]);
3902
3903 pr_warn("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] takes:\n",
3904 curr->comm, task_pid_nr(curr),
3905 lockdep_hardirq_context(), hardirq_count() >> HARDIRQ_SHIFT,
3906 lockdep_softirq_context(curr), softirq_count() >> SOFTIRQ_SHIFT,
3907 lockdep_hardirqs_enabled(),
3908 lockdep_softirqs_enabled(curr));
3909 print_lock(this);
3910
3911 pr_warn("{%s} state was registered at:\n", usage_str[prev_bit]);
3912 print_lock_trace(hlock_class(this)->usage_traces[prev_bit], 1);
3913
3914 print_irqtrace_events(curr);
3915 pr_warn("\nother info that might help us debug this:\n");
3916 print_usage_bug_scenario(this);
3917
3918 lockdep_print_held_locks(curr);
3919
3920 pr_warn("\nstack backtrace:\n");
3921 dump_stack();
3922}
3923
3924/*
3925 * Print out an error if an invalid bit is set:
3926 */
3927static inline int
3928valid_state(struct task_struct *curr, struct held_lock *this,
3929 enum lock_usage_bit new_bit, enum lock_usage_bit bad_bit)
3930{
3931 if (unlikely(hlock_class(this)->usage_mask & (1 << bad_bit))) {
3932 graph_unlock();
3933 print_usage_bug(curr, this, bad_bit, new_bit);
3934 return 0;
3935 }
3936 return 1;
3937}
3938
3939
3940/*
3941 * print irq inversion bug:
3942 */
3943static void
3944print_irq_inversion_bug(struct task_struct *curr,
3945 struct lock_list *root, struct lock_list *other,
3946 struct held_lock *this, int forwards,
3947 const char *irqclass)
3948{
3949 struct lock_list *entry = other;
3950 struct lock_list *middle = NULL;
3951 int depth;
3952
3953 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
3954 return;
3955
3956 pr_warn("\n");
3957 pr_warn("========================================================\n");
3958 pr_warn("WARNING: possible irq lock inversion dependency detected\n");
3959 print_kernel_ident();
3960 pr_warn("--------------------------------------------------------\n");
3961 pr_warn("%s/%d just changed the state of lock:\n",
3962 curr->comm, task_pid_nr(curr));
3963 print_lock(this);
3964 if (forwards)
3965 pr_warn("but this lock took another, %s-unsafe lock in the past:\n", irqclass);
3966 else
3967 pr_warn("but this lock was taken by another, %s-safe lock in the past:\n", irqclass);
3968 print_lock_name(other->class);
3969 pr_warn("\n\nand interrupts could create inverse lock ordering between them.\n\n");
3970
3971 pr_warn("\nother info that might help us debug this:\n");
3972
3973 /* Find a middle lock (if one exists) */
3974 depth = get_lock_depth(other);
3975 do {
3976 if (depth == 0 && (entry != root)) {
3977 pr_warn("lockdep:%s bad path found in chain graph\n", __func__);
3978 break;
3979 }
3980 middle = entry;
3981 entry = get_lock_parent(entry);
3982 depth--;
3983 } while (entry && entry != root && (depth >= 0));
3984 if (forwards)
3985 print_irq_lock_scenario(root, other,
3986 middle ? middle->class : root->class, other->class);
3987 else
3988 print_irq_lock_scenario(other, root,
3989 middle ? middle->class : other->class, root->class);
3990
3991 lockdep_print_held_locks(curr);
3992
3993 pr_warn("\nthe shortest dependencies between 2nd lock and 1st lock:\n");
3994 root->trace = save_trace();
3995 if (!root->trace)
3996 return;
3997 print_shortest_lock_dependencies(other, root);
3998
3999 pr_warn("\nstack backtrace:\n");
4000 dump_stack();
4001}
4002
4003/*
4004 * Prove that in the forwards-direction subgraph starting at <this>
4005 * there is no lock matching <mask>:
4006 */
4007static int
4008check_usage_forwards(struct task_struct *curr, struct held_lock *this,
4009 enum lock_usage_bit bit)
4010{
4011 enum bfs_result ret;
4012 struct lock_list root;
4013 struct lock_list *target_entry;
4014 enum lock_usage_bit read_bit = bit + LOCK_USAGE_READ_MASK;
4015 unsigned usage_mask = lock_flag(bit) | lock_flag(read_bit);
4016
4017 bfs_init_root(&root, this);
4018 ret = find_usage_forwards(&root, usage_mask, &target_entry);
4019 if (bfs_error(ret)) {
4020 print_bfs_bug(ret);
4021 return 0;
4022 }
4023 if (ret == BFS_RNOMATCH)
4024 return 1;
4025
4026 /* Check whether write or read usage is the match */
4027 if (target_entry->class->usage_mask & lock_flag(bit)) {
4028 print_irq_inversion_bug(curr, &root, target_entry,
4029 this, 1, state_name(bit));
4030 } else {
4031 print_irq_inversion_bug(curr, &root, target_entry,
4032 this, 1, state_name(read_bit));
4033 }
4034
4035 return 0;
4036}
4037
4038/*
4039 * Prove that in the backwards-direction subgraph starting at <this>
4040 * there is no lock matching <mask>:
4041 */
4042static int
4043check_usage_backwards(struct task_struct *curr, struct held_lock *this,
4044 enum lock_usage_bit bit)
4045{
4046 enum bfs_result ret;
4047 struct lock_list root;
4048 struct lock_list *target_entry;
4049 enum lock_usage_bit read_bit = bit + LOCK_USAGE_READ_MASK;
4050 unsigned usage_mask = lock_flag(bit) | lock_flag(read_bit);
4051
4052 bfs_init_rootb(&root, this);
4053 ret = find_usage_backwards(&root, usage_mask, &target_entry);
4054 if (bfs_error(ret)) {
4055 print_bfs_bug(ret);
4056 return 0;
4057 }
4058 if (ret == BFS_RNOMATCH)
4059 return 1;
4060
4061 /* Check whether write or read usage is the match */
4062 if (target_entry->class->usage_mask & lock_flag(bit)) {
4063 print_irq_inversion_bug(curr, &root, target_entry,
4064 this, 0, state_name(bit));
4065 } else {
4066 print_irq_inversion_bug(curr, &root, target_entry,
4067 this, 0, state_name(read_bit));
4068 }
4069
4070 return 0;
4071}
4072
4073void print_irqtrace_events(struct task_struct *curr)
4074{
4075 const struct irqtrace_events *trace = &curr->irqtrace;
4076
4077 printk("irq event stamp: %u\n", trace->irq_events);
4078 printk("hardirqs last enabled at (%u): [<%px>] %pS\n",
4079 trace->hardirq_enable_event, (void *)trace->hardirq_enable_ip,
4080 (void *)trace->hardirq_enable_ip);
4081 printk("hardirqs last disabled at (%u): [<%px>] %pS\n",
4082 trace->hardirq_disable_event, (void *)trace->hardirq_disable_ip,
4083 (void *)trace->hardirq_disable_ip);
4084 printk("softirqs last enabled at (%u): [<%px>] %pS\n",
4085 trace->softirq_enable_event, (void *)trace->softirq_enable_ip,
4086 (void *)trace->softirq_enable_ip);
4087 printk("softirqs last disabled at (%u): [<%px>] %pS\n",
4088 trace->softirq_disable_event, (void *)trace->softirq_disable_ip,
4089 (void *)trace->softirq_disable_ip);
4090}
4091
4092static int HARDIRQ_verbose(struct lock_class *class)
4093{
4094#if HARDIRQ_VERBOSE
4095 return class_filter(class);
4096#endif
4097 return 0;
4098}
4099
4100static int SOFTIRQ_verbose(struct lock_class *class)
4101{
4102#if SOFTIRQ_VERBOSE
4103 return class_filter(class);
4104#endif
4105 return 0;
4106}
4107
4108static int (*state_verbose_f[])(struct lock_class *class) = {
4109#define LOCKDEP_STATE(__STATE) \
4110 __STATE##_verbose,
4111#include "lockdep_states.h"
4112#undef LOCKDEP_STATE
4113};
4114
4115static inline int state_verbose(enum lock_usage_bit bit,
4116 struct lock_class *class)
4117{
4118 return state_verbose_f[bit >> LOCK_USAGE_DIR_MASK](class);
4119}
4120
4121typedef int (*check_usage_f)(struct task_struct *, struct held_lock *,
4122 enum lock_usage_bit bit, const char *name);
4123
4124static int
4125mark_lock_irq(struct task_struct *curr, struct held_lock *this,
4126 enum lock_usage_bit new_bit)
4127{
4128 int excl_bit = exclusive_bit(new_bit);
4129 int read = new_bit & LOCK_USAGE_READ_MASK;
4130 int dir = new_bit & LOCK_USAGE_DIR_MASK;
4131
4132 /*
4133 * Validate that this particular lock does not have conflicting
4134 * usage states.
4135 */
4136 if (!valid_state(curr, this, new_bit, excl_bit))
4137 return 0;
4138
4139 /*
4140 * Check for read in write conflicts
4141 */
4142 if (!read && !valid_state(curr, this, new_bit,
4143 excl_bit + LOCK_USAGE_READ_MASK))
4144 return 0;
4145
4146
4147 /*
4148 * Validate that the lock dependencies don't have conflicting usage
4149 * states.
4150 */
4151 if (dir) {
4152 /*
4153 * mark ENABLED has to look backwards -- to ensure no dependee
4154 * has USED_IN state, which, again, would allow recursion deadlocks.
4155 */
4156 if (!check_usage_backwards(curr, this, excl_bit))
4157 return 0;
4158 } else {
4159 /*
4160 * mark USED_IN has to look forwards -- to ensure no dependency
4161 * has ENABLED state, which would allow recursion deadlocks.
4162 */
4163 if (!check_usage_forwards(curr, this, excl_bit))
4164 return 0;
4165 }
4166
4167 if (state_verbose(new_bit, hlock_class(this)))
4168 return 2;
4169
4170 return 1;
4171}
4172
4173/*
4174 * Mark all held locks with a usage bit:
4175 */
4176static int
4177mark_held_locks(struct task_struct *curr, enum lock_usage_bit base_bit)
4178{
4179 struct held_lock *hlock;
4180 int i;
4181
4182 for (i = 0; i < curr->lockdep_depth; i++) {
4183 enum lock_usage_bit hlock_bit = base_bit;
4184 hlock = curr->held_locks + i;
4185
4186 if (hlock->read)
4187 hlock_bit += LOCK_USAGE_READ_MASK;
4188
4189 BUG_ON(hlock_bit >= LOCK_USAGE_STATES);
4190
4191 if (!hlock->check)
4192 continue;
4193
4194 if (!mark_lock(curr, hlock, hlock_bit))
4195 return 0;
4196 }
4197
4198 return 1;
4199}
4200
4201/*
4202 * Hardirqs will be enabled:
4203 */
4204static void __trace_hardirqs_on_caller(void)
4205{
4206 struct task_struct *curr = current;
4207
4208 /*
4209 * We are going to turn hardirqs on, so set the
4210 * usage bit for all held locks:
4211 */
4212 if (!mark_held_locks(curr, LOCK_ENABLED_HARDIRQ))
4213 return;
4214 /*
4215 * If we have softirqs enabled, then set the usage
4216 * bit for all held locks. (disabled hardirqs prevented
4217 * this bit from being set before)
4218 */
4219 if (curr->softirqs_enabled)
4220 mark_held_locks(curr, LOCK_ENABLED_SOFTIRQ);
4221}
4222
4223/**
4224 * lockdep_hardirqs_on_prepare - Prepare for enabling interrupts
4225 * @ip: Caller address
4226 *
4227 * Invoked before a possible transition to RCU idle from exit to user or
4228 * guest mode. This ensures that all RCU operations are done before RCU
4229 * stops watching. After the RCU transition lockdep_hardirqs_on() has to be
4230 * invoked to set the final state.
4231 */
4232void lockdep_hardirqs_on_prepare(unsigned long ip)
4233{
4234 if (unlikely(!debug_locks))
4235 return;
4236
4237 /*
4238 * NMIs do not (and cannot) track lock dependencies, nothing to do.
4239 */
4240 if (unlikely(in_nmi()))
4241 return;
4242
4243 if (unlikely(this_cpu_read(lockdep_recursion)))
4244 return;
4245
4246 if (unlikely(lockdep_hardirqs_enabled())) {
4247 /*
4248 * Neither irq nor preemption are disabled here
4249 * so this is racy by nature but losing one hit
4250 * in a stat is not a big deal.
4251 */
4252 __debug_atomic_inc(redundant_hardirqs_on);
4253 return;
4254 }
4255
4256 /*
4257 * We're enabling irqs and according to our state above irqs weren't
4258 * already enabled, yet we find the hardware thinks they are in fact
4259 * enabled.. someone messed up their IRQ state tracing.
4260 */
4261 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
4262 return;
4263
4264 /*
4265 * See the fine text that goes along with this variable definition.
4266 */
4267 if (DEBUG_LOCKS_WARN_ON(early_boot_irqs_disabled))
4268 return;
4269
4270 /*
4271 * Can't allow enabling interrupts while in an interrupt handler,
4272 * that's general bad form and such. Recursion, limited stack etc..
4273 */
4274 if (DEBUG_LOCKS_WARN_ON(lockdep_hardirq_context()))
4275 return;
4276
4277 current->hardirq_chain_key = current->curr_chain_key;
4278
4279 lockdep_recursion_inc();
4280 __trace_hardirqs_on_caller();
4281 lockdep_recursion_finish();
4282}
4283EXPORT_SYMBOL_GPL(lockdep_hardirqs_on_prepare);
4284
4285void noinstr lockdep_hardirqs_on(unsigned long ip)
4286{
4287 struct irqtrace_events *trace = ¤t->irqtrace;
4288
4289 if (unlikely(!debug_locks))
4290 return;
4291
4292 /*
4293 * NMIs can happen in the middle of local_irq_{en,dis}able() where the
4294 * tracking state and hardware state are out of sync.
4295 *
4296 * NMIs must save lockdep_hardirqs_enabled() to restore IRQ state from,
4297 * and not rely on hardware state like normal interrupts.
4298 */
4299 if (unlikely(in_nmi())) {
4300 if (!IS_ENABLED(CONFIG_TRACE_IRQFLAGS_NMI))
4301 return;
4302
4303 /*
4304 * Skip:
4305 * - recursion check, because NMI can hit lockdep;
4306 * - hardware state check, because above;
4307 * - chain_key check, see lockdep_hardirqs_on_prepare().
4308 */
4309 goto skip_checks;
4310 }
4311
4312 if (unlikely(this_cpu_read(lockdep_recursion)))
4313 return;
4314
4315 if (lockdep_hardirqs_enabled()) {
4316 /*
4317 * Neither irq nor preemption are disabled here
4318 * so this is racy by nature but losing one hit
4319 * in a stat is not a big deal.
4320 */
4321 __debug_atomic_inc(redundant_hardirqs_on);
4322 return;
4323 }
4324
4325 /*
4326 * We're enabling irqs and according to our state above irqs weren't
4327 * already enabled, yet we find the hardware thinks they are in fact
4328 * enabled.. someone messed up their IRQ state tracing.
4329 */
4330 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
4331 return;
4332
4333 /*
4334 * Ensure the lock stack remained unchanged between
4335 * lockdep_hardirqs_on_prepare() and lockdep_hardirqs_on().
4336 */
4337 DEBUG_LOCKS_WARN_ON(current->hardirq_chain_key !=
4338 current->curr_chain_key);
4339
4340skip_checks:
4341 /* we'll do an OFF -> ON transition: */
4342 __this_cpu_write(hardirqs_enabled, 1);
4343 trace->hardirq_enable_ip = ip;
4344 trace->hardirq_enable_event = ++trace->irq_events;
4345 debug_atomic_inc(hardirqs_on_events);
4346}
4347EXPORT_SYMBOL_GPL(lockdep_hardirqs_on);
4348
4349/*
4350 * Hardirqs were disabled:
4351 */
4352void noinstr lockdep_hardirqs_off(unsigned long ip)
4353{
4354 if (unlikely(!debug_locks))
4355 return;
4356
4357 /*
4358 * Matching lockdep_hardirqs_on(), allow NMIs in the middle of lockdep;
4359 * they will restore the software state. This ensures the software
4360 * state is consistent inside NMIs as well.
4361 */
4362 if (in_nmi()) {
4363 if (!IS_ENABLED(CONFIG_TRACE_IRQFLAGS_NMI))
4364 return;
4365 } else if (__this_cpu_read(lockdep_recursion))
4366 return;
4367
4368 /*
4369 * So we're supposed to get called after you mask local IRQs, but for
4370 * some reason the hardware doesn't quite think you did a proper job.
4371 */
4372 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
4373 return;
4374
4375 if (lockdep_hardirqs_enabled()) {
4376 struct irqtrace_events *trace = ¤t->irqtrace;
4377
4378 /*
4379 * We have done an ON -> OFF transition:
4380 */
4381 __this_cpu_write(hardirqs_enabled, 0);
4382 trace->hardirq_disable_ip = ip;
4383 trace->hardirq_disable_event = ++trace->irq_events;
4384 debug_atomic_inc(hardirqs_off_events);
4385 } else {
4386 debug_atomic_inc(redundant_hardirqs_off);
4387 }
4388}
4389EXPORT_SYMBOL_GPL(lockdep_hardirqs_off);
4390
4391/*
4392 * Softirqs will be enabled:
4393 */
4394void lockdep_softirqs_on(unsigned long ip)
4395{
4396 struct irqtrace_events *trace = ¤t->irqtrace;
4397
4398 if (unlikely(!lockdep_enabled()))
4399 return;
4400
4401 /*
4402 * We fancy IRQs being disabled here, see softirq.c, avoids
4403 * funny state and nesting things.
4404 */
4405 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
4406 return;
4407
4408 if (current->softirqs_enabled) {
4409 debug_atomic_inc(redundant_softirqs_on);
4410 return;
4411 }
4412
4413 lockdep_recursion_inc();
4414 /*
4415 * We'll do an OFF -> ON transition:
4416 */
4417 current->softirqs_enabled = 1;
4418 trace->softirq_enable_ip = ip;
4419 trace->softirq_enable_event = ++trace->irq_events;
4420 debug_atomic_inc(softirqs_on_events);
4421 /*
4422 * We are going to turn softirqs on, so set the
4423 * usage bit for all held locks, if hardirqs are
4424 * enabled too:
4425 */
4426 if (lockdep_hardirqs_enabled())
4427 mark_held_locks(current, LOCK_ENABLED_SOFTIRQ);
4428 lockdep_recursion_finish();
4429}
4430
4431/*
4432 * Softirqs were disabled:
4433 */
4434void lockdep_softirqs_off(unsigned long ip)
4435{
4436 if (unlikely(!lockdep_enabled()))
4437 return;
4438
4439 /*
4440 * We fancy IRQs being disabled here, see softirq.c
4441 */
4442 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
4443 return;
4444
4445 if (current->softirqs_enabled) {
4446 struct irqtrace_events *trace = ¤t->irqtrace;
4447
4448 /*
4449 * We have done an ON -> OFF transition:
4450 */
4451 current->softirqs_enabled = 0;
4452 trace->softirq_disable_ip = ip;
4453 trace->softirq_disable_event = ++trace->irq_events;
4454 debug_atomic_inc(softirqs_off_events);
4455 /*
4456 * Whoops, we wanted softirqs off, so why aren't they?
4457 */
4458 DEBUG_LOCKS_WARN_ON(!softirq_count());
4459 } else
4460 debug_atomic_inc(redundant_softirqs_off);
4461}
4462
4463static int
4464mark_usage(struct task_struct *curr, struct held_lock *hlock, int check)
4465{
4466 if (!check)
4467 goto lock_used;
4468
4469 /*
4470 * If non-trylock use in a hardirq or softirq context, then
4471 * mark the lock as used in these contexts:
4472 */
4473 if (!hlock->trylock) {
4474 if (hlock->read) {
4475 if (lockdep_hardirq_context())
4476 if (!mark_lock(curr, hlock,
4477 LOCK_USED_IN_HARDIRQ_READ))
4478 return 0;
4479 if (curr->softirq_context)
4480 if (!mark_lock(curr, hlock,
4481 LOCK_USED_IN_SOFTIRQ_READ))
4482 return 0;
4483 } else {
4484 if (lockdep_hardirq_context())
4485 if (!mark_lock(curr, hlock, LOCK_USED_IN_HARDIRQ))
4486 return 0;
4487 if (curr->softirq_context)
4488 if (!mark_lock(curr, hlock, LOCK_USED_IN_SOFTIRQ))
4489 return 0;
4490 }
4491 }
4492 if (!hlock->hardirqs_off) {
4493 if (hlock->read) {
4494 if (!mark_lock(curr, hlock,
4495 LOCK_ENABLED_HARDIRQ_READ))
4496 return 0;
4497 if (curr->softirqs_enabled)
4498 if (!mark_lock(curr, hlock,
4499 LOCK_ENABLED_SOFTIRQ_READ))
4500 return 0;
4501 } else {
4502 if (!mark_lock(curr, hlock,
4503 LOCK_ENABLED_HARDIRQ))
4504 return 0;
4505 if (curr->softirqs_enabled)
4506 if (!mark_lock(curr, hlock,
4507 LOCK_ENABLED_SOFTIRQ))
4508 return 0;
4509 }
4510 }
4511
4512lock_used:
4513 /* mark it as used: */
4514 if (!mark_lock(curr, hlock, LOCK_USED))
4515 return 0;
4516
4517 return 1;
4518}
4519
4520static inline unsigned int task_irq_context(struct task_struct *task)
4521{
4522 return LOCK_CHAIN_HARDIRQ_CONTEXT * !!lockdep_hardirq_context() +
4523 LOCK_CHAIN_SOFTIRQ_CONTEXT * !!task->softirq_context;
4524}
4525
4526static int separate_irq_context(struct task_struct *curr,
4527 struct held_lock *hlock)
4528{
4529 unsigned int depth = curr->lockdep_depth;
4530
4531 /*
4532 * Keep track of points where we cross into an interrupt context:
4533 */
4534 if (depth) {
4535 struct held_lock *prev_hlock;
4536
4537 prev_hlock = curr->held_locks + depth-1;
4538 /*
4539 * If we cross into another context, reset the
4540 * hash key (this also prevents the checking and the
4541 * adding of the dependency to 'prev'):
4542 */
4543 if (prev_hlock->irq_context != hlock->irq_context)
4544 return 1;
4545 }
4546 return 0;
4547}
4548
4549/*
4550 * Mark a lock with a usage bit, and validate the state transition:
4551 */
4552static int mark_lock(struct task_struct *curr, struct held_lock *this,
4553 enum lock_usage_bit new_bit)
4554{
4555 unsigned int new_mask, ret = 1;
4556
4557 if (new_bit >= LOCK_USAGE_STATES) {
4558 DEBUG_LOCKS_WARN_ON(1);
4559 return 0;
4560 }
4561
4562 if (new_bit == LOCK_USED && this->read)
4563 new_bit = LOCK_USED_READ;
4564
4565 new_mask = 1 << new_bit;
4566
4567 /*
4568 * If already set then do not dirty the cacheline,
4569 * nor do any checks:
4570 */
4571 if (likely(hlock_class(this)->usage_mask & new_mask))
4572 return 1;
4573
4574 if (!graph_lock())
4575 return 0;
4576 /*
4577 * Make sure we didn't race:
4578 */
4579 if (unlikely(hlock_class(this)->usage_mask & new_mask))
4580 goto unlock;
4581
4582 if (!hlock_class(this)->usage_mask)
4583 debug_atomic_dec(nr_unused_locks);
4584
4585 hlock_class(this)->usage_mask |= new_mask;
4586
4587 if (new_bit < LOCK_TRACE_STATES) {
4588 if (!(hlock_class(this)->usage_traces[new_bit] = save_trace()))
4589 return 0;
4590 }
4591
4592 if (new_bit < LOCK_USED) {
4593 ret = mark_lock_irq(curr, this, new_bit);
4594 if (!ret)
4595 return 0;
4596 }
4597
4598unlock:
4599 graph_unlock();
4600
4601 /*
4602 * We must printk outside of the graph_lock:
4603 */
4604 if (ret == 2) {
4605 printk("\nmarked lock as {%s}:\n", usage_str[new_bit]);
4606 print_lock(this);
4607 print_irqtrace_events(curr);
4608 dump_stack();
4609 }
4610
4611 return ret;
4612}
4613
4614static inline short task_wait_context(struct task_struct *curr)
4615{
4616 /*
4617 * Set appropriate wait type for the context; for IRQs we have to take
4618 * into account force_irqthread as that is implied by PREEMPT_RT.
4619 */
4620 if (lockdep_hardirq_context()) {
4621 /*
4622 * Check if force_irqthreads will run us threaded.
4623 */
4624 if (curr->hardirq_threaded || curr->irq_config)
4625 return LD_WAIT_CONFIG;
4626
4627 return LD_WAIT_SPIN;
4628 } else if (curr->softirq_context) {
4629 /*
4630 * Softirqs are always threaded.
4631 */
4632 return LD_WAIT_CONFIG;
4633 }
4634
4635 return LD_WAIT_MAX;
4636}
4637
4638static int
4639print_lock_invalid_wait_context(struct task_struct *curr,
4640 struct held_lock *hlock)
4641{
4642 short curr_inner;
4643
4644 if (!debug_locks_off())
4645 return 0;
4646 if (debug_locks_silent)
4647 return 0;
4648
4649 pr_warn("\n");
4650 pr_warn("=============================\n");
4651 pr_warn("[ BUG: Invalid wait context ]\n");
4652 print_kernel_ident();
4653 pr_warn("-----------------------------\n");
4654
4655 pr_warn("%s/%d is trying to lock:\n", curr->comm, task_pid_nr(curr));
4656 print_lock(hlock);
4657
4658 pr_warn("other info that might help us debug this:\n");
4659
4660 curr_inner = task_wait_context(curr);
4661 pr_warn("context-{%d:%d}\n", curr_inner, curr_inner);
4662
4663 lockdep_print_held_locks(curr);
4664
4665 pr_warn("stack backtrace:\n");
4666 dump_stack();
4667
4668 return 0;
4669}
4670
4671/*
4672 * Verify the wait_type context.
4673 *
4674 * This check validates we takes locks in the right wait-type order; that is it
4675 * ensures that we do not take mutexes inside spinlocks and do not attempt to
4676 * acquire spinlocks inside raw_spinlocks and the sort.
4677 *
4678 * The entire thing is slightly more complex because of RCU, RCU is a lock that
4679 * can be taken from (pretty much) any context but also has constraints.
4680 * However when taken in a stricter environment the RCU lock does not loosen
4681 * the constraints.
4682 *
4683 * Therefore we must look for the strictest environment in the lock stack and
4684 * compare that to the lock we're trying to acquire.
4685 */
4686static int check_wait_context(struct task_struct *curr, struct held_lock *next)
4687{
4688 u8 next_inner = hlock_class(next)->wait_type_inner;
4689 u8 next_outer = hlock_class(next)->wait_type_outer;
4690 u8 curr_inner;
4691 int depth;
4692
4693 if (!next_inner || next->trylock)
4694 return 0;
4695
4696 if (!next_outer)
4697 next_outer = next_inner;
4698
4699 /*
4700 * Find start of current irq_context..
4701 */
4702 for (depth = curr->lockdep_depth - 1; depth >= 0; depth--) {
4703 struct held_lock *prev = curr->held_locks + depth;
4704 if (prev->irq_context != next->irq_context)
4705 break;
4706 }
4707 depth++;
4708
4709 curr_inner = task_wait_context(curr);
4710
4711 for (; depth < curr->lockdep_depth; depth++) {
4712 struct held_lock *prev = curr->held_locks + depth;
4713 u8 prev_inner = hlock_class(prev)->wait_type_inner;
4714
4715 if (prev_inner) {
4716 /*
4717 * We can have a bigger inner than a previous one
4718 * when outer is smaller than inner, as with RCU.
4719 *
4720 * Also due to trylocks.
4721 */
4722 curr_inner = min(curr_inner, prev_inner);
4723 }
4724 }
4725
4726 if (next_outer > curr_inner)
4727 return print_lock_invalid_wait_context(curr, next);
4728
4729 return 0;
4730}
4731
4732#else /* CONFIG_PROVE_LOCKING */
4733
4734static inline int
4735mark_usage(struct task_struct *curr, struct held_lock *hlock, int check)
4736{
4737 return 1;
4738}
4739
4740static inline unsigned int task_irq_context(struct task_struct *task)
4741{
4742 return 0;
4743}
4744
4745static inline int separate_irq_context(struct task_struct *curr,
4746 struct held_lock *hlock)
4747{
4748 return 0;
4749}
4750
4751static inline int check_wait_context(struct task_struct *curr,
4752 struct held_lock *next)
4753{
4754 return 0;
4755}
4756
4757#endif /* CONFIG_PROVE_LOCKING */
4758
4759/*
4760 * Initialize a lock instance's lock-class mapping info:
4761 */
4762void lockdep_init_map_type(struct lockdep_map *lock, const char *name,
4763 struct lock_class_key *key, int subclass,
4764 u8 inner, u8 outer, u8 lock_type)
4765{
4766 int i;
4767
4768 for (i = 0; i < NR_LOCKDEP_CACHING_CLASSES; i++)
4769 lock->class_cache[i] = NULL;
4770
4771#ifdef CONFIG_LOCK_STAT
4772 lock->cpu = raw_smp_processor_id();
4773#endif
4774
4775 /*
4776 * Can't be having no nameless bastards around this place!
4777 */
4778 if (DEBUG_LOCKS_WARN_ON(!name)) {
4779 lock->name = "NULL";
4780 return;
4781 }
4782
4783 lock->name = name;
4784
4785 lock->wait_type_outer = outer;
4786 lock->wait_type_inner = inner;
4787 lock->lock_type = lock_type;
4788
4789 /*
4790 * No key, no joy, we need to hash something.
4791 */
4792 if (DEBUG_LOCKS_WARN_ON(!key))
4793 return;
4794 /*
4795 * Sanity check, the lock-class key must either have been allocated
4796 * statically or must have been registered as a dynamic key.
4797 */
4798 if (!static_obj(key) && !is_dynamic_key(key)) {
4799 if (debug_locks)
4800 printk(KERN_ERR "BUG: key %px has not been registered!\n", key);
4801 DEBUG_LOCKS_WARN_ON(1);
4802 return;
4803 }
4804 lock->key = key;
4805
4806 if (unlikely(!debug_locks))
4807 return;
4808
4809 if (subclass) {
4810 unsigned long flags;
4811
4812 if (DEBUG_LOCKS_WARN_ON(!lockdep_enabled()))
4813 return;
4814
4815 raw_local_irq_save(flags);
4816 lockdep_recursion_inc();
4817 register_lock_class(lock, subclass, 1);
4818 lockdep_recursion_finish();
4819 raw_local_irq_restore(flags);
4820 }
4821}
4822EXPORT_SYMBOL_GPL(lockdep_init_map_type);
4823
4824struct lock_class_key __lockdep_no_validate__;
4825EXPORT_SYMBOL_GPL(__lockdep_no_validate__);
4826
4827static void
4828print_lock_nested_lock_not_held(struct task_struct *curr,
4829 struct held_lock *hlock,
4830 unsigned long ip)
4831{
4832 if (!debug_locks_off())
4833 return;
4834 if (debug_locks_silent)
4835 return;
4836
4837 pr_warn("\n");
4838 pr_warn("==================================\n");
4839 pr_warn("WARNING: Nested lock was not taken\n");
4840 print_kernel_ident();
4841 pr_warn("----------------------------------\n");
4842
4843 pr_warn("%s/%d is trying to lock:\n", curr->comm, task_pid_nr(curr));
4844 print_lock(hlock);
4845
4846 pr_warn("\nbut this task is not holding:\n");
4847 pr_warn("%s\n", hlock->nest_lock->name);
4848
4849 pr_warn("\nstack backtrace:\n");
4850 dump_stack();
4851
4852 pr_warn("\nother info that might help us debug this:\n");
4853 lockdep_print_held_locks(curr);
4854
4855 pr_warn("\nstack backtrace:\n");
4856 dump_stack();
4857}
4858
4859static int __lock_is_held(const struct lockdep_map *lock, int read);
4860
4861/*
4862 * This gets called for every mutex_lock*()/spin_lock*() operation.
4863 * We maintain the dependency maps and validate the locking attempt:
4864 *
4865 * The callers must make sure that IRQs are disabled before calling it,
4866 * otherwise we could get an interrupt which would want to take locks,
4867 * which would end up in lockdep again.
4868 */
4869static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
4870 int trylock, int read, int check, int hardirqs_off,
4871 struct lockdep_map *nest_lock, unsigned long ip,
4872 int references, int pin_count)
4873{
4874 struct task_struct *curr = current;
4875 struct lock_class *class = NULL;
4876 struct held_lock *hlock;
4877 unsigned int depth;
4878 int chain_head = 0;
4879 int class_idx;
4880 u64 chain_key;
4881
4882 if (unlikely(!debug_locks))
4883 return 0;
4884
4885 if (!prove_locking || lock->key == &__lockdep_no_validate__)
4886 check = 0;
4887
4888 if (subclass < NR_LOCKDEP_CACHING_CLASSES)
4889 class = lock->class_cache[subclass];
4890 /*
4891 * Not cached?
4892 */
4893 if (unlikely(!class)) {
4894 class = register_lock_class(lock, subclass, 0);
4895 if (!class)
4896 return 0;
4897 }
4898
4899 debug_class_ops_inc(class);
4900
4901 if (very_verbose(class)) {
4902 printk("\nacquire class [%px] %s", class->key, class->name);
4903 if (class->name_version > 1)
4904 printk(KERN_CONT "#%d", class->name_version);
4905 printk(KERN_CONT "\n");
4906 dump_stack();
4907 }
4908
4909 /*
4910 * Add the lock to the list of currently held locks.
4911 * (we dont increase the depth just yet, up until the
4912 * dependency checks are done)
4913 */
4914 depth = curr->lockdep_depth;
4915 /*
4916 * Ran out of static storage for our per-task lock stack again have we?
4917 */
4918 if (DEBUG_LOCKS_WARN_ON(depth >= MAX_LOCK_DEPTH))
4919 return 0;
4920
4921 class_idx = class - lock_classes;
4922
4923 if (depth) { /* we're holding locks */
4924 hlock = curr->held_locks + depth - 1;
4925 if (hlock->class_idx == class_idx && nest_lock) {
4926 if (!references)
4927 references++;
4928
4929 if (!hlock->references)
4930 hlock->references++;
4931
4932 hlock->references += references;
4933
4934 /* Overflow */
4935 if (DEBUG_LOCKS_WARN_ON(hlock->references < references))
4936 return 0;
4937
4938 return 2;
4939 }
4940 }
4941
4942 hlock = curr->held_locks + depth;
4943 /*
4944 * Plain impossible, we just registered it and checked it weren't no
4945 * NULL like.. I bet this mushroom I ate was good!
4946 */
4947 if (DEBUG_LOCKS_WARN_ON(!class))
4948 return 0;
4949 hlock->class_idx = class_idx;
4950 hlock->acquire_ip = ip;
4951 hlock->instance = lock;
4952 hlock->nest_lock = nest_lock;
4953 hlock->irq_context = task_irq_context(curr);
4954 hlock->trylock = trylock;
4955 hlock->read = read;
4956 hlock->check = check;
4957 hlock->hardirqs_off = !!hardirqs_off;
4958 hlock->references = references;
4959#ifdef CONFIG_LOCK_STAT
4960 hlock->waittime_stamp = 0;
4961 hlock->holdtime_stamp = lockstat_clock();
4962#endif
4963 hlock->pin_count = pin_count;
4964
4965 if (check_wait_context(curr, hlock))
4966 return 0;
4967
4968 /* Initialize the lock usage bit */
4969 if (!mark_usage(curr, hlock, check))
4970 return 0;
4971
4972 /*
4973 * Calculate the chain hash: it's the combined hash of all the
4974 * lock keys along the dependency chain. We save the hash value
4975 * at every step so that we can get the current hash easily
4976 * after unlock. The chain hash is then used to cache dependency
4977 * results.
4978 *
4979 * The 'key ID' is what is the most compact key value to drive
4980 * the hash, not class->key.
4981 */
4982 /*
4983 * Whoops, we did it again.. class_idx is invalid.
4984 */
4985 if (DEBUG_LOCKS_WARN_ON(!test_bit(class_idx, lock_classes_in_use)))
4986 return 0;
4987
4988 chain_key = curr->curr_chain_key;
4989 if (!depth) {
4990 /*
4991 * How can we have a chain hash when we ain't got no keys?!
4992 */
4993 if (DEBUG_LOCKS_WARN_ON(chain_key != INITIAL_CHAIN_KEY))
4994 return 0;
4995 chain_head = 1;
4996 }
4997
4998 hlock->prev_chain_key = chain_key;
4999 if (separate_irq_context(curr, hlock)) {
5000 chain_key = INITIAL_CHAIN_KEY;
5001 chain_head = 1;
5002 }
5003 chain_key = iterate_chain_key(chain_key, hlock_id(hlock));
5004
5005 if (nest_lock && !__lock_is_held(nest_lock, -1)) {
5006 print_lock_nested_lock_not_held(curr, hlock, ip);
5007 return 0;
5008 }
5009
5010 if (!debug_locks_silent) {
5011 WARN_ON_ONCE(depth && !hlock_class(hlock - 1)->key);
5012 WARN_ON_ONCE(!hlock_class(hlock)->key);
5013 }
5014
5015 if (!validate_chain(curr, hlock, chain_head, chain_key))
5016 return 0;
5017
5018 curr->curr_chain_key = chain_key;
5019 curr->lockdep_depth++;
5020 check_chain_key(curr);
5021#ifdef CONFIG_DEBUG_LOCKDEP
5022 if (unlikely(!debug_locks))
5023 return 0;
5024#endif
5025 if (unlikely(curr->lockdep_depth >= MAX_LOCK_DEPTH)) {
5026 debug_locks_off();
5027 print_lockdep_off("BUG: MAX_LOCK_DEPTH too low!");
5028 printk(KERN_DEBUG "depth: %i max: %lu!\n",
5029 curr->lockdep_depth, MAX_LOCK_DEPTH);
5030
5031 lockdep_print_held_locks(current);
5032 debug_show_all_locks();
5033 dump_stack();
5034
5035 return 0;
5036 }
5037
5038 if (unlikely(curr->lockdep_depth > max_lockdep_depth))
5039 max_lockdep_depth = curr->lockdep_depth;
5040
5041 return 1;
5042}
5043
5044static void print_unlock_imbalance_bug(struct task_struct *curr,
5045 struct lockdep_map *lock,
5046 unsigned long ip)
5047{
5048 if (!debug_locks_off())
5049 return;
5050 if (debug_locks_silent)
5051 return;
5052
5053 pr_warn("\n");
5054 pr_warn("=====================================\n");
5055 pr_warn("WARNING: bad unlock balance detected!\n");
5056 print_kernel_ident();
5057 pr_warn("-------------------------------------\n");
5058 pr_warn("%s/%d is trying to release lock (",
5059 curr->comm, task_pid_nr(curr));
5060 print_lockdep_cache(lock);
5061 pr_cont(") at:\n");
5062 print_ip_sym(KERN_WARNING, ip);
5063 pr_warn("but there are no more locks to release!\n");
5064 pr_warn("\nother info that might help us debug this:\n");
5065 lockdep_print_held_locks(curr);
5066
5067 pr_warn("\nstack backtrace:\n");
5068 dump_stack();
5069}
5070
5071static noinstr int match_held_lock(const struct held_lock *hlock,
5072 const struct lockdep_map *lock)
5073{
5074 if (hlock->instance == lock)
5075 return 1;
5076
5077 if (hlock->references) {
5078 const struct lock_class *class = lock->class_cache[0];
5079
5080 if (!class)
5081 class = look_up_lock_class(lock, 0);
5082
5083 /*
5084 * If look_up_lock_class() failed to find a class, we're trying
5085 * to test if we hold a lock that has never yet been acquired.
5086 * Clearly if the lock hasn't been acquired _ever_, we're not
5087 * holding it either, so report failure.
5088 */
5089 if (!class)
5090 return 0;
5091
5092 /*
5093 * References, but not a lock we're actually ref-counting?
5094 * State got messed up, follow the sites that change ->references
5095 * and try to make sense of it.
5096 */
5097 if (DEBUG_LOCKS_WARN_ON(!hlock->nest_lock))
5098 return 0;
5099
5100 if (hlock->class_idx == class - lock_classes)
5101 return 1;
5102 }
5103
5104 return 0;
5105}
5106
5107/* @depth must not be zero */
5108static struct held_lock *find_held_lock(struct task_struct *curr,
5109 struct lockdep_map *lock,
5110 unsigned int depth, int *idx)
5111{
5112 struct held_lock *ret, *hlock, *prev_hlock;
5113 int i;
5114
5115 i = depth - 1;
5116 hlock = curr->held_locks + i;
5117 ret = hlock;
5118 if (match_held_lock(hlock, lock))
5119 goto out;
5120
5121 ret = NULL;
5122 for (i--, prev_hlock = hlock--;
5123 i >= 0;
5124 i--, prev_hlock = hlock--) {
5125 /*
5126 * We must not cross into another context:
5127 */
5128 if (prev_hlock->irq_context != hlock->irq_context) {
5129 ret = NULL;
5130 break;
5131 }
5132 if (match_held_lock(hlock, lock)) {
5133 ret = hlock;
5134 break;
5135 }
5136 }
5137
5138out:
5139 *idx = i;
5140 return ret;
5141}
5142
5143static int reacquire_held_locks(struct task_struct *curr, unsigned int depth,
5144 int idx, unsigned int *merged)
5145{
5146 struct held_lock *hlock;
5147 int first_idx = idx;
5148
5149 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
5150 return 0;
5151
5152 for (hlock = curr->held_locks + idx; idx < depth; idx++, hlock++) {
5153 switch (__lock_acquire(hlock->instance,
5154 hlock_class(hlock)->subclass,
5155 hlock->trylock,
5156 hlock->read, hlock->check,
5157 hlock->hardirqs_off,
5158 hlock->nest_lock, hlock->acquire_ip,
5159 hlock->references, hlock->pin_count)) {
5160 case 0:
5161 return 1;
5162 case 1:
5163 break;
5164 case 2:
5165 *merged += (idx == first_idx);
5166 break;
5167 default:
5168 WARN_ON(1);
5169 return 0;
5170 }
5171 }
5172 return 0;
5173}
5174
5175static int
5176__lock_set_class(struct lockdep_map *lock, const char *name,
5177 struct lock_class_key *key, unsigned int subclass,
5178 unsigned long ip)
5179{
5180 struct task_struct *curr = current;
5181 unsigned int depth, merged = 0;
5182 struct held_lock *hlock;
5183 struct lock_class *class;
5184 int i;
5185
5186 if (unlikely(!debug_locks))
5187 return 0;
5188
5189 depth = curr->lockdep_depth;
5190 /*
5191 * This function is about (re)setting the class of a held lock,
5192 * yet we're not actually holding any locks. Naughty user!
5193 */
5194 if (DEBUG_LOCKS_WARN_ON(!depth))
5195 return 0;
5196
5197 hlock = find_held_lock(curr, lock, depth, &i);
5198 if (!hlock) {
5199 print_unlock_imbalance_bug(curr, lock, ip);
5200 return 0;
5201 }
5202
5203 lockdep_init_map_waits(lock, name, key, 0,
5204 lock->wait_type_inner,
5205 lock->wait_type_outer);
5206 class = register_lock_class(lock, subclass, 0);
5207 hlock->class_idx = class - lock_classes;
5208
5209 curr->lockdep_depth = i;
5210 curr->curr_chain_key = hlock->prev_chain_key;
5211
5212 if (reacquire_held_locks(curr, depth, i, &merged))
5213 return 0;
5214
5215 /*
5216 * I took it apart and put it back together again, except now I have
5217 * these 'spare' parts.. where shall I put them.
5218 */
5219 if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - merged))
5220 return 0;
5221 return 1;
5222}
5223
5224static int __lock_downgrade(struct lockdep_map *lock, unsigned long ip)
5225{
5226 struct task_struct *curr = current;
5227 unsigned int depth, merged = 0;
5228 struct held_lock *hlock;
5229 int i;
5230
5231 if (unlikely(!debug_locks))
5232 return 0;
5233
5234 depth = curr->lockdep_depth;
5235 /*
5236 * This function is about (re)setting the class of a held lock,
5237 * yet we're not actually holding any locks. Naughty user!
5238 */
5239 if (DEBUG_LOCKS_WARN_ON(!depth))
5240 return 0;
5241
5242 hlock = find_held_lock(curr, lock, depth, &i);
5243 if (!hlock) {
5244 print_unlock_imbalance_bug(curr, lock, ip);
5245 return 0;
5246 }
5247
5248 curr->lockdep_depth = i;
5249 curr->curr_chain_key = hlock->prev_chain_key;
5250
5251 WARN(hlock->read, "downgrading a read lock");
5252 hlock->read = 1;
5253 hlock->acquire_ip = ip;
5254
5255 if (reacquire_held_locks(curr, depth, i, &merged))
5256 return 0;
5257
5258 /* Merging can't happen with unchanged classes.. */
5259 if (DEBUG_LOCKS_WARN_ON(merged))
5260 return 0;
5261
5262 /*
5263 * I took it apart and put it back together again, except now I have
5264 * these 'spare' parts.. where shall I put them.
5265 */
5266 if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth))
5267 return 0;
5268
5269 return 1;
5270}
5271
5272/*
5273 * Remove the lock from the list of currently held locks - this gets
5274 * called on mutex_unlock()/spin_unlock*() (or on a failed
5275 * mutex_lock_interruptible()).
5276 */
5277static int
5278__lock_release(struct lockdep_map *lock, unsigned long ip)
5279{
5280 struct task_struct *curr = current;
5281 unsigned int depth, merged = 1;
5282 struct held_lock *hlock;
5283 int i;
5284
5285 if (unlikely(!debug_locks))
5286 return 0;
5287
5288 depth = curr->lockdep_depth;
5289 /*
5290 * So we're all set to release this lock.. wait what lock? We don't
5291 * own any locks, you've been drinking again?
5292 */
5293 if (depth <= 0) {
5294 print_unlock_imbalance_bug(curr, lock, ip);
5295 return 0;
5296 }
5297
5298 /*
5299 * Check whether the lock exists in the current stack
5300 * of held locks:
5301 */
5302 hlock = find_held_lock(curr, lock, depth, &i);
5303 if (!hlock) {
5304 print_unlock_imbalance_bug(curr, lock, ip);
5305 return 0;
5306 }
5307
5308 if (hlock->instance == lock)
5309 lock_release_holdtime(hlock);
5310
5311 WARN(hlock->pin_count, "releasing a pinned lock\n");
5312
5313 if (hlock->references) {
5314 hlock->references--;
5315 if (hlock->references) {
5316 /*
5317 * We had, and after removing one, still have
5318 * references, the current lock stack is still
5319 * valid. We're done!
5320 */
5321 return 1;
5322 }
5323 }
5324
5325 /*
5326 * We have the right lock to unlock, 'hlock' points to it.
5327 * Now we remove it from the stack, and add back the other
5328 * entries (if any), recalculating the hash along the way:
5329 */
5330
5331 curr->lockdep_depth = i;
5332 curr->curr_chain_key = hlock->prev_chain_key;
5333
5334 /*
5335 * The most likely case is when the unlock is on the innermost
5336 * lock. In this case, we are done!
5337 */
5338 if (i == depth-1)
5339 return 1;
5340
5341 if (reacquire_held_locks(curr, depth, i + 1, &merged))
5342 return 0;
5343
5344 /*
5345 * We had N bottles of beer on the wall, we drank one, but now
5346 * there's not N-1 bottles of beer left on the wall...
5347 * Pouring two of the bottles together is acceptable.
5348 */
5349 DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - merged);
5350
5351 /*
5352 * Since reacquire_held_locks() would have called check_chain_key()
5353 * indirectly via __lock_acquire(), we don't need to do it again
5354 * on return.
5355 */
5356 return 0;
5357}
5358
5359static __always_inline
5360int __lock_is_held(const struct lockdep_map *lock, int read)
5361{
5362 struct task_struct *curr = current;
5363 int i;
5364
5365 for (i = 0; i < curr->lockdep_depth; i++) {
5366 struct held_lock *hlock = curr->held_locks + i;
5367
5368 if (match_held_lock(hlock, lock)) {
5369 if (read == -1 || hlock->read == read)
5370 return LOCK_STATE_HELD;
5371
5372 return LOCK_STATE_NOT_HELD;
5373 }
5374 }
5375
5376 return LOCK_STATE_NOT_HELD;
5377}
5378
5379static struct pin_cookie __lock_pin_lock(struct lockdep_map *lock)
5380{
5381 struct pin_cookie cookie = NIL_COOKIE;
5382 struct task_struct *curr = current;
5383 int i;
5384
5385 if (unlikely(!debug_locks))
5386 return cookie;
5387
5388 for (i = 0; i < curr->lockdep_depth; i++) {
5389 struct held_lock *hlock = curr->held_locks + i;
5390
5391 if (match_held_lock(hlock, lock)) {
5392 /*
5393 * Grab 16bits of randomness; this is sufficient to not
5394 * be guessable and still allows some pin nesting in
5395 * our u32 pin_count.
5396 */
5397 cookie.val = 1 + (prandom_u32() >> 16);
5398 hlock->pin_count += cookie.val;
5399 return cookie;
5400 }
5401 }
5402
5403 WARN(1, "pinning an unheld lock\n");
5404 return cookie;
5405}
5406
5407static void __lock_repin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
5408{
5409 struct task_struct *curr = current;
5410 int i;
5411
5412 if (unlikely(!debug_locks))
5413 return;
5414
5415 for (i = 0; i < curr->lockdep_depth; i++) {
5416 struct held_lock *hlock = curr->held_locks + i;
5417
5418 if (match_held_lock(hlock, lock)) {
5419 hlock->pin_count += cookie.val;
5420 return;
5421 }
5422 }
5423
5424 WARN(1, "pinning an unheld lock\n");
5425}
5426
5427static void __lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
5428{
5429 struct task_struct *curr = current;
5430 int i;
5431
5432 if (unlikely(!debug_locks))
5433 return;
5434
5435 for (i = 0; i < curr->lockdep_depth; i++) {
5436 struct held_lock *hlock = curr->held_locks + i;
5437
5438 if (match_held_lock(hlock, lock)) {
5439 if (WARN(!hlock->pin_count, "unpinning an unpinned lock\n"))
5440 return;
5441
5442 hlock->pin_count -= cookie.val;
5443
5444 if (WARN((int)hlock->pin_count < 0, "pin count corrupted\n"))
5445 hlock->pin_count = 0;
5446
5447 return;
5448 }
5449 }
5450
5451 WARN(1, "unpinning an unheld lock\n");
5452}
5453
5454/*
5455 * Check whether we follow the irq-flags state precisely:
5456 */
5457static noinstr void check_flags(unsigned long flags)
5458{
5459#if defined(CONFIG_PROVE_LOCKING) && defined(CONFIG_DEBUG_LOCKDEP)
5460 if (!debug_locks)
5461 return;
5462
5463 /* Get the warning out.. */
5464 instrumentation_begin();
5465
5466 if (irqs_disabled_flags(flags)) {
5467 if (DEBUG_LOCKS_WARN_ON(lockdep_hardirqs_enabled())) {
5468 printk("possible reason: unannotated irqs-off.\n");
5469 }
5470 } else {
5471 if (DEBUG_LOCKS_WARN_ON(!lockdep_hardirqs_enabled())) {
5472 printk("possible reason: unannotated irqs-on.\n");
5473 }
5474 }
5475
5476 /*
5477 * We dont accurately track softirq state in e.g.
5478 * hardirq contexts (such as on 4KSTACKS), so only
5479 * check if not in hardirq contexts:
5480 */
5481 if (!hardirq_count()) {
5482 if (softirq_count()) {
5483 /* like the above, but with softirqs */
5484 DEBUG_LOCKS_WARN_ON(current->softirqs_enabled);
5485 } else {
5486 /* lick the above, does it taste good? */
5487 DEBUG_LOCKS_WARN_ON(!current->softirqs_enabled);
5488 }
5489 }
5490
5491 if (!debug_locks)
5492 print_irqtrace_events(current);
5493
5494 instrumentation_end();
5495#endif
5496}
5497
5498void lock_set_class(struct lockdep_map *lock, const char *name,
5499 struct lock_class_key *key, unsigned int subclass,
5500 unsigned long ip)
5501{
5502 unsigned long flags;
5503
5504 if (unlikely(!lockdep_enabled()))
5505 return;
5506
5507 raw_local_irq_save(flags);
5508 lockdep_recursion_inc();
5509 check_flags(flags);
5510 if (__lock_set_class(lock, name, key, subclass, ip))
5511 check_chain_key(current);
5512 lockdep_recursion_finish();
5513 raw_local_irq_restore(flags);
5514}
5515EXPORT_SYMBOL_GPL(lock_set_class);
5516
5517void lock_downgrade(struct lockdep_map *lock, unsigned long ip)
5518{
5519 unsigned long flags;
5520
5521 if (unlikely(!lockdep_enabled()))
5522 return;
5523
5524 raw_local_irq_save(flags);
5525 lockdep_recursion_inc();
5526 check_flags(flags);
5527 if (__lock_downgrade(lock, ip))
5528 check_chain_key(current);
5529 lockdep_recursion_finish();
5530 raw_local_irq_restore(flags);
5531}
5532EXPORT_SYMBOL_GPL(lock_downgrade);
5533
5534/* NMI context !!! */
5535static void verify_lock_unused(struct lockdep_map *lock, struct held_lock *hlock, int subclass)
5536{
5537#ifdef CONFIG_PROVE_LOCKING
5538 struct lock_class *class = look_up_lock_class(lock, subclass);
5539 unsigned long mask = LOCKF_USED;
5540
5541 /* if it doesn't have a class (yet), it certainly hasn't been used yet */
5542 if (!class)
5543 return;
5544
5545 /*
5546 * READ locks only conflict with USED, such that if we only ever use
5547 * READ locks, there is no deadlock possible -- RCU.
5548 */
5549 if (!hlock->read)
5550 mask |= LOCKF_USED_READ;
5551
5552 if (!(class->usage_mask & mask))
5553 return;
5554
5555 hlock->class_idx = class - lock_classes;
5556
5557 print_usage_bug(current, hlock, LOCK_USED, LOCK_USAGE_STATES);
5558#endif
5559}
5560
5561static bool lockdep_nmi(void)
5562{
5563 if (raw_cpu_read(lockdep_recursion))
5564 return false;
5565
5566 if (!in_nmi())
5567 return false;
5568
5569 return true;
5570}
5571
5572/*
5573 * read_lock() is recursive if:
5574 * 1. We force lockdep think this way in selftests or
5575 * 2. The implementation is not queued read/write lock or
5576 * 3. The locker is at an in_interrupt() context.
5577 */
5578bool read_lock_is_recursive(void)
5579{
5580 return force_read_lock_recursive ||
5581 !IS_ENABLED(CONFIG_QUEUED_RWLOCKS) ||
5582 in_interrupt();
5583}
5584EXPORT_SYMBOL_GPL(read_lock_is_recursive);
5585
5586/*
5587 * We are not always called with irqs disabled - do that here,
5588 * and also avoid lockdep recursion:
5589 */
5590void lock_acquire(struct lockdep_map *lock, unsigned int subclass,
5591 int trylock, int read, int check,
5592 struct lockdep_map *nest_lock, unsigned long ip)
5593{
5594 unsigned long flags;
5595
5596 trace_lock_acquire(lock, subclass, trylock, read, check, nest_lock, ip);
5597
5598 if (!debug_locks)
5599 return;
5600
5601 if (unlikely(!lockdep_enabled())) {
5602 /* XXX allow trylock from NMI ?!? */
5603 if (lockdep_nmi() && !trylock) {
5604 struct held_lock hlock;
5605
5606 hlock.acquire_ip = ip;
5607 hlock.instance = lock;
5608 hlock.nest_lock = nest_lock;
5609 hlock.irq_context = 2; // XXX
5610 hlock.trylock = trylock;
5611 hlock.read = read;
5612 hlock.check = check;
5613 hlock.hardirqs_off = true;
5614 hlock.references = 0;
5615
5616 verify_lock_unused(lock, &hlock, subclass);
5617 }
5618 return;
5619 }
5620
5621 raw_local_irq_save(flags);
5622 check_flags(flags);
5623
5624 lockdep_recursion_inc();
5625 __lock_acquire(lock, subclass, trylock, read, check,
5626 irqs_disabled_flags(flags), nest_lock, ip, 0, 0);
5627 lockdep_recursion_finish();
5628 raw_local_irq_restore(flags);
5629}
5630EXPORT_SYMBOL_GPL(lock_acquire);
5631
5632void lock_release(struct lockdep_map *lock, unsigned long ip)
5633{
5634 unsigned long flags;
5635
5636 trace_lock_release(lock, ip);
5637
5638 if (unlikely(!lockdep_enabled()))
5639 return;
5640
5641 raw_local_irq_save(flags);
5642 check_flags(flags);
5643
5644 lockdep_recursion_inc();
5645 if (__lock_release(lock, ip))
5646 check_chain_key(current);
5647 lockdep_recursion_finish();
5648 raw_local_irq_restore(flags);
5649}
5650EXPORT_SYMBOL_GPL(lock_release);
5651
5652noinstr int lock_is_held_type(const struct lockdep_map *lock, int read)
5653{
5654 unsigned long flags;
5655 int ret = LOCK_STATE_NOT_HELD;
5656
5657 /*
5658 * Avoid false negative lockdep_assert_held() and
5659 * lockdep_assert_not_held().
5660 */
5661 if (unlikely(!lockdep_enabled()))
5662 return LOCK_STATE_UNKNOWN;
5663
5664 raw_local_irq_save(flags);
5665 check_flags(flags);
5666
5667 lockdep_recursion_inc();
5668 ret = __lock_is_held(lock, read);
5669 lockdep_recursion_finish();
5670 raw_local_irq_restore(flags);
5671
5672 return ret;
5673}
5674EXPORT_SYMBOL_GPL(lock_is_held_type);
5675NOKPROBE_SYMBOL(lock_is_held_type);
5676
5677struct pin_cookie lock_pin_lock(struct lockdep_map *lock)
5678{
5679 struct pin_cookie cookie = NIL_COOKIE;
5680 unsigned long flags;
5681
5682 if (unlikely(!lockdep_enabled()))
5683 return cookie;
5684
5685 raw_local_irq_save(flags);
5686 check_flags(flags);
5687
5688 lockdep_recursion_inc();
5689 cookie = __lock_pin_lock(lock);
5690 lockdep_recursion_finish();
5691 raw_local_irq_restore(flags);
5692
5693 return cookie;
5694}
5695EXPORT_SYMBOL_GPL(lock_pin_lock);
5696
5697void lock_repin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
5698{
5699 unsigned long flags;
5700
5701 if (unlikely(!lockdep_enabled()))
5702 return;
5703
5704 raw_local_irq_save(flags);
5705 check_flags(flags);
5706
5707 lockdep_recursion_inc();
5708 __lock_repin_lock(lock, cookie);
5709 lockdep_recursion_finish();
5710 raw_local_irq_restore(flags);
5711}
5712EXPORT_SYMBOL_GPL(lock_repin_lock);
5713
5714void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
5715{
5716 unsigned long flags;
5717
5718 if (unlikely(!lockdep_enabled()))
5719 return;
5720
5721 raw_local_irq_save(flags);
5722 check_flags(flags);
5723
5724 lockdep_recursion_inc();
5725 __lock_unpin_lock(lock, cookie);
5726 lockdep_recursion_finish();
5727 raw_local_irq_restore(flags);
5728}
5729EXPORT_SYMBOL_GPL(lock_unpin_lock);
5730
5731#ifdef CONFIG_LOCK_STAT
5732static void print_lock_contention_bug(struct task_struct *curr,
5733 struct lockdep_map *lock,
5734 unsigned long ip)
5735{
5736 if (!debug_locks_off())
5737 return;
5738 if (debug_locks_silent)
5739 return;
5740
5741 pr_warn("\n");
5742 pr_warn("=================================\n");
5743 pr_warn("WARNING: bad contention detected!\n");
5744 print_kernel_ident();
5745 pr_warn("---------------------------------\n");
5746 pr_warn("%s/%d is trying to contend lock (",
5747 curr->comm, task_pid_nr(curr));
5748 print_lockdep_cache(lock);
5749 pr_cont(") at:\n");
5750 print_ip_sym(KERN_WARNING, ip);
5751 pr_warn("but there are no locks held!\n");
5752 pr_warn("\nother info that might help us debug this:\n");
5753 lockdep_print_held_locks(curr);
5754
5755 pr_warn("\nstack backtrace:\n");
5756 dump_stack();
5757}
5758
5759static void
5760__lock_contended(struct lockdep_map *lock, unsigned long ip)
5761{
5762 struct task_struct *curr = current;
5763 struct held_lock *hlock;
5764 struct lock_class_stats *stats;
5765 unsigned int depth;
5766 int i, contention_point, contending_point;
5767
5768 depth = curr->lockdep_depth;
5769 /*
5770 * Whee, we contended on this lock, except it seems we're not
5771 * actually trying to acquire anything much at all..
5772 */
5773 if (DEBUG_LOCKS_WARN_ON(!depth))
5774 return;
5775
5776 hlock = find_held_lock(curr, lock, depth, &i);
5777 if (!hlock) {
5778 print_lock_contention_bug(curr, lock, ip);
5779 return;
5780 }
5781
5782 if (hlock->instance != lock)
5783 return;
5784
5785 hlock->waittime_stamp = lockstat_clock();
5786
5787 contention_point = lock_point(hlock_class(hlock)->contention_point, ip);
5788 contending_point = lock_point(hlock_class(hlock)->contending_point,
5789 lock->ip);
5790
5791 stats = get_lock_stats(hlock_class(hlock));
5792 if (contention_point < LOCKSTAT_POINTS)
5793 stats->contention_point[contention_point]++;
5794 if (contending_point < LOCKSTAT_POINTS)
5795 stats->contending_point[contending_point]++;
5796 if (lock->cpu != smp_processor_id())
5797 stats->bounces[bounce_contended + !!hlock->read]++;
5798}
5799
5800static void
5801__lock_acquired(struct lockdep_map *lock, unsigned long ip)
5802{
5803 struct task_struct *curr = current;
5804 struct held_lock *hlock;
5805 struct lock_class_stats *stats;
5806 unsigned int depth;
5807 u64 now, waittime = 0;
5808 int i, cpu;
5809
5810 depth = curr->lockdep_depth;
5811 /*
5812 * Yay, we acquired ownership of this lock we didn't try to
5813 * acquire, how the heck did that happen?
5814 */
5815 if (DEBUG_LOCKS_WARN_ON(!depth))
5816 return;
5817
5818 hlock = find_held_lock(curr, lock, depth, &i);
5819 if (!hlock) {
5820 print_lock_contention_bug(curr, lock, _RET_IP_);
5821 return;
5822 }
5823
5824 if (hlock->instance != lock)
5825 return;
5826
5827 cpu = smp_processor_id();
5828 if (hlock->waittime_stamp) {
5829 now = lockstat_clock();
5830 waittime = now - hlock->waittime_stamp;
5831 hlock->holdtime_stamp = now;
5832 }
5833
5834 stats = get_lock_stats(hlock_class(hlock));
5835 if (waittime) {
5836 if (hlock->read)
5837 lock_time_inc(&stats->read_waittime, waittime);
5838 else
5839 lock_time_inc(&stats->write_waittime, waittime);
5840 }
5841 if (lock->cpu != cpu)
5842 stats->bounces[bounce_acquired + !!hlock->read]++;
5843
5844 lock->cpu = cpu;
5845 lock->ip = ip;
5846}
5847
5848void lock_contended(struct lockdep_map *lock, unsigned long ip)
5849{
5850 unsigned long flags;
5851
5852 trace_lock_contended(lock, ip);
5853
5854 if (unlikely(!lock_stat || !lockdep_enabled()))
5855 return;
5856
5857 raw_local_irq_save(flags);
5858 check_flags(flags);
5859 lockdep_recursion_inc();
5860 __lock_contended(lock, ip);
5861 lockdep_recursion_finish();
5862 raw_local_irq_restore(flags);
5863}
5864EXPORT_SYMBOL_GPL(lock_contended);
5865
5866void lock_acquired(struct lockdep_map *lock, unsigned long ip)
5867{
5868 unsigned long flags;
5869
5870 trace_lock_acquired(lock, ip);
5871
5872 if (unlikely(!lock_stat || !lockdep_enabled()))
5873 return;
5874
5875 raw_local_irq_save(flags);
5876 check_flags(flags);
5877 lockdep_recursion_inc();
5878 __lock_acquired(lock, ip);
5879 lockdep_recursion_finish();
5880 raw_local_irq_restore(flags);
5881}
5882EXPORT_SYMBOL_GPL(lock_acquired);
5883#endif
5884
5885/*
5886 * Used by the testsuite, sanitize the validator state
5887 * after a simulated failure:
5888 */
5889
5890void lockdep_reset(void)
5891{
5892 unsigned long flags;
5893 int i;
5894
5895 raw_local_irq_save(flags);
5896 lockdep_init_task(current);
5897 memset(current->held_locks, 0, MAX_LOCK_DEPTH*sizeof(struct held_lock));
5898 nr_hardirq_chains = 0;
5899 nr_softirq_chains = 0;
5900 nr_process_chains = 0;
5901 debug_locks = 1;
5902 for (i = 0; i < CHAINHASH_SIZE; i++)
5903 INIT_HLIST_HEAD(chainhash_table + i);
5904 raw_local_irq_restore(flags);
5905}
5906
5907/* Remove a class from a lock chain. Must be called with the graph lock held. */
5908static void remove_class_from_lock_chain(struct pending_free *pf,
5909 struct lock_chain *chain,
5910 struct lock_class *class)
5911{
5912#ifdef CONFIG_PROVE_LOCKING
5913 int i;
5914
5915 for (i = chain->base; i < chain->base + chain->depth; i++) {
5916 if (chain_hlock_class_idx(chain_hlocks[i]) != class - lock_classes)
5917 continue;
5918 /*
5919 * Each lock class occurs at most once in a lock chain so once
5920 * we found a match we can break out of this loop.
5921 */
5922 goto free_lock_chain;
5923 }
5924 /* Since the chain has not been modified, return. */
5925 return;
5926
5927free_lock_chain:
5928 free_chain_hlocks(chain->base, chain->depth);
5929 /* Overwrite the chain key for concurrent RCU readers. */
5930 WRITE_ONCE(chain->chain_key, INITIAL_CHAIN_KEY);
5931 dec_chains(chain->irq_context);
5932
5933 /*
5934 * Note: calling hlist_del_rcu() from inside a
5935 * hlist_for_each_entry_rcu() loop is safe.
5936 */
5937 hlist_del_rcu(&chain->entry);
5938 __set_bit(chain - lock_chains, pf->lock_chains_being_freed);
5939 nr_zapped_lock_chains++;
5940#endif
5941}
5942
5943/* Must be called with the graph lock held. */
5944static void remove_class_from_lock_chains(struct pending_free *pf,
5945 struct lock_class *class)
5946{
5947 struct lock_chain *chain;
5948 struct hlist_head *head;
5949 int i;
5950
5951 for (i = 0; i < ARRAY_SIZE(chainhash_table); i++) {
5952 head = chainhash_table + i;
5953 hlist_for_each_entry_rcu(chain, head, entry) {
5954 remove_class_from_lock_chain(pf, chain, class);
5955 }
5956 }
5957}
5958
5959/*
5960 * Remove all references to a lock class. The caller must hold the graph lock.
5961 */
5962static void zap_class(struct pending_free *pf, struct lock_class *class)
5963{
5964 struct lock_list *entry;
5965 int i;
5966
5967 WARN_ON_ONCE(!class->key);
5968
5969 /*
5970 * Remove all dependencies this lock is
5971 * involved in:
5972 */
5973 for_each_set_bit(i, list_entries_in_use, ARRAY_SIZE(list_entries)) {
5974 entry = list_entries + i;
5975 if (entry->class != class && entry->links_to != class)
5976 continue;
5977 __clear_bit(i, list_entries_in_use);
5978 nr_list_entries--;
5979 list_del_rcu(&entry->entry);
5980 }
5981 if (list_empty(&class->locks_after) &&
5982 list_empty(&class->locks_before)) {
5983 list_move_tail(&class->lock_entry, &pf->zapped);
5984 hlist_del_rcu(&class->hash_entry);
5985 WRITE_ONCE(class->key, NULL);
5986 WRITE_ONCE(class->name, NULL);
5987 nr_lock_classes--;
5988 __clear_bit(class - lock_classes, lock_classes_in_use);
5989 } else {
5990 WARN_ONCE(true, "%s() failed for class %s\n", __func__,
5991 class->name);
5992 }
5993
5994 remove_class_from_lock_chains(pf, class);
5995 nr_zapped_classes++;
5996}
5997
5998static void reinit_class(struct lock_class *class)
5999{
6000 void *const p = class;
6001 const unsigned int offset = offsetof(struct lock_class, key);
6002
6003 WARN_ON_ONCE(!class->lock_entry.next);
6004 WARN_ON_ONCE(!list_empty(&class->locks_after));
6005 WARN_ON_ONCE(!list_empty(&class->locks_before));
6006 memset(p + offset, 0, sizeof(*class) - offset);
6007 WARN_ON_ONCE(!class->lock_entry.next);
6008 WARN_ON_ONCE(!list_empty(&class->locks_after));
6009 WARN_ON_ONCE(!list_empty(&class->locks_before));
6010}
6011
6012static inline int within(const void *addr, void *start, unsigned long size)
6013{
6014 return addr >= start && addr < start + size;
6015}
6016
6017static bool inside_selftest(void)
6018{
6019 return current == lockdep_selftest_task_struct;
6020}
6021
6022/* The caller must hold the graph lock. */
6023static struct pending_free *get_pending_free(void)
6024{
6025 return delayed_free.pf + delayed_free.index;
6026}
6027
6028static void free_zapped_rcu(struct rcu_head *cb);
6029
6030/*
6031 * Schedule an RCU callback if no RCU callback is pending. Must be called with
6032 * the graph lock held.
6033 */
6034static void call_rcu_zapped(struct pending_free *pf)
6035{
6036 WARN_ON_ONCE(inside_selftest());
6037
6038 if (list_empty(&pf->zapped))
6039 return;
6040
6041 if (delayed_free.scheduled)
6042 return;
6043
6044 delayed_free.scheduled = true;
6045
6046 WARN_ON_ONCE(delayed_free.pf + delayed_free.index != pf);
6047 delayed_free.index ^= 1;
6048
6049 call_rcu(&delayed_free.rcu_head, free_zapped_rcu);
6050}
6051
6052/* The caller must hold the graph lock. May be called from RCU context. */
6053static void __free_zapped_classes(struct pending_free *pf)
6054{
6055 struct lock_class *class;
6056
6057 check_data_structures();
6058
6059 list_for_each_entry(class, &pf->zapped, lock_entry)
6060 reinit_class(class);
6061
6062 list_splice_init(&pf->zapped, &free_lock_classes);
6063
6064#ifdef CONFIG_PROVE_LOCKING
6065 bitmap_andnot(lock_chains_in_use, lock_chains_in_use,
6066 pf->lock_chains_being_freed, ARRAY_SIZE(lock_chains));
6067 bitmap_clear(pf->lock_chains_being_freed, 0, ARRAY_SIZE(lock_chains));
6068#endif
6069}
6070
6071static void free_zapped_rcu(struct rcu_head *ch)
6072{
6073 struct pending_free *pf;
6074 unsigned long flags;
6075
6076 if (WARN_ON_ONCE(ch != &delayed_free.rcu_head))
6077 return;
6078
6079 raw_local_irq_save(flags);
6080 lockdep_lock();
6081
6082 /* closed head */
6083 pf = delayed_free.pf + (delayed_free.index ^ 1);
6084 __free_zapped_classes(pf);
6085 delayed_free.scheduled = false;
6086
6087 /*
6088 * If there's anything on the open list, close and start a new callback.
6089 */
6090 call_rcu_zapped(delayed_free.pf + delayed_free.index);
6091
6092 lockdep_unlock();
6093 raw_local_irq_restore(flags);
6094}
6095
6096/*
6097 * Remove all lock classes from the class hash table and from the
6098 * all_lock_classes list whose key or name is in the address range [start,
6099 * start + size). Move these lock classes to the zapped_classes list. Must
6100 * be called with the graph lock held.
6101 */
6102static void __lockdep_free_key_range(struct pending_free *pf, void *start,
6103 unsigned long size)
6104{
6105 struct lock_class *class;
6106 struct hlist_head *head;
6107 int i;
6108
6109 /* Unhash all classes that were created by a module. */
6110 for (i = 0; i < CLASSHASH_SIZE; i++) {
6111 head = classhash_table + i;
6112 hlist_for_each_entry_rcu(class, head, hash_entry) {
6113 if (!within(class->key, start, size) &&
6114 !within(class->name, start, size))
6115 continue;
6116 zap_class(pf, class);
6117 }
6118 }
6119}
6120
6121/*
6122 * Used in module.c to remove lock classes from memory that is going to be
6123 * freed; and possibly re-used by other modules.
6124 *
6125 * We will have had one synchronize_rcu() before getting here, so we're
6126 * guaranteed nobody will look up these exact classes -- they're properly dead
6127 * but still allocated.
6128 */
6129static void lockdep_free_key_range_reg(void *start, unsigned long size)
6130{
6131 struct pending_free *pf;
6132 unsigned long flags;
6133
6134 init_data_structures_once();
6135
6136 raw_local_irq_save(flags);
6137 lockdep_lock();
6138 pf = get_pending_free();
6139 __lockdep_free_key_range(pf, start, size);
6140 call_rcu_zapped(pf);
6141 lockdep_unlock();
6142 raw_local_irq_restore(flags);
6143
6144 /*
6145 * Wait for any possible iterators from look_up_lock_class() to pass
6146 * before continuing to free the memory they refer to.
6147 */
6148 synchronize_rcu();
6149}
6150
6151/*
6152 * Free all lockdep keys in the range [start, start+size). Does not sleep.
6153 * Ignores debug_locks. Must only be used by the lockdep selftests.
6154 */
6155static void lockdep_free_key_range_imm(void *start, unsigned long size)
6156{
6157 struct pending_free *pf = delayed_free.pf;
6158 unsigned long flags;
6159
6160 init_data_structures_once();
6161
6162 raw_local_irq_save(flags);
6163 lockdep_lock();
6164 __lockdep_free_key_range(pf, start, size);
6165 __free_zapped_classes(pf);
6166 lockdep_unlock();
6167 raw_local_irq_restore(flags);
6168}
6169
6170void lockdep_free_key_range(void *start, unsigned long size)
6171{
6172 init_data_structures_once();
6173
6174 if (inside_selftest())
6175 lockdep_free_key_range_imm(start, size);
6176 else
6177 lockdep_free_key_range_reg(start, size);
6178}
6179
6180/*
6181 * Check whether any element of the @lock->class_cache[] array refers to a
6182 * registered lock class. The caller must hold either the graph lock or the
6183 * RCU read lock.
6184 */
6185static bool lock_class_cache_is_registered(struct lockdep_map *lock)
6186{
6187 struct lock_class *class;
6188 struct hlist_head *head;
6189 int i, j;
6190
6191 for (i = 0; i < CLASSHASH_SIZE; i++) {
6192 head = classhash_table + i;
6193 hlist_for_each_entry_rcu(class, head, hash_entry) {
6194 for (j = 0; j < NR_LOCKDEP_CACHING_CLASSES; j++)
6195 if (lock->class_cache[j] == class)
6196 return true;
6197 }
6198 }
6199 return false;
6200}
6201
6202/* The caller must hold the graph lock. Does not sleep. */
6203static void __lockdep_reset_lock(struct pending_free *pf,
6204 struct lockdep_map *lock)
6205{
6206 struct lock_class *class;
6207 int j;
6208
6209 /*
6210 * Remove all classes this lock might have:
6211 */
6212 for (j = 0; j < MAX_LOCKDEP_SUBCLASSES; j++) {
6213 /*
6214 * If the class exists we look it up and zap it:
6215 */
6216 class = look_up_lock_class(lock, j);
6217 if (class)
6218 zap_class(pf, class);
6219 }
6220 /*
6221 * Debug check: in the end all mapped classes should
6222 * be gone.
6223 */
6224 if (WARN_ON_ONCE(lock_class_cache_is_registered(lock)))
6225 debug_locks_off();
6226}
6227
6228/*
6229 * Remove all information lockdep has about a lock if debug_locks == 1. Free
6230 * released data structures from RCU context.
6231 */
6232static void lockdep_reset_lock_reg(struct lockdep_map *lock)
6233{
6234 struct pending_free *pf;
6235 unsigned long flags;
6236 int locked;
6237
6238 raw_local_irq_save(flags);
6239 locked = graph_lock();
6240 if (!locked)
6241 goto out_irq;
6242
6243 pf = get_pending_free();
6244 __lockdep_reset_lock(pf, lock);
6245 call_rcu_zapped(pf);
6246
6247 graph_unlock();
6248out_irq:
6249 raw_local_irq_restore(flags);
6250}
6251
6252/*
6253 * Reset a lock. Does not sleep. Ignores debug_locks. Must only be used by the
6254 * lockdep selftests.
6255 */
6256static void lockdep_reset_lock_imm(struct lockdep_map *lock)
6257{
6258 struct pending_free *pf = delayed_free.pf;
6259 unsigned long flags;
6260
6261 raw_local_irq_save(flags);
6262 lockdep_lock();
6263 __lockdep_reset_lock(pf, lock);
6264 __free_zapped_classes(pf);
6265 lockdep_unlock();
6266 raw_local_irq_restore(flags);
6267}
6268
6269void lockdep_reset_lock(struct lockdep_map *lock)
6270{
6271 init_data_structures_once();
6272
6273 if (inside_selftest())
6274 lockdep_reset_lock_imm(lock);
6275 else
6276 lockdep_reset_lock_reg(lock);
6277}
6278
6279/* Unregister a dynamically allocated key. */
6280void lockdep_unregister_key(struct lock_class_key *key)
6281{
6282 struct hlist_head *hash_head = keyhashentry(key);
6283 struct lock_class_key *k;
6284 struct pending_free *pf;
6285 unsigned long flags;
6286 bool found = false;
6287
6288 might_sleep();
6289
6290 if (WARN_ON_ONCE(static_obj(key)))
6291 return;
6292
6293 raw_local_irq_save(flags);
6294 if (!graph_lock())
6295 goto out_irq;
6296
6297 pf = get_pending_free();
6298 hlist_for_each_entry_rcu(k, hash_head, hash_entry) {
6299 if (k == key) {
6300 hlist_del_rcu(&k->hash_entry);
6301 found = true;
6302 break;
6303 }
6304 }
6305 WARN_ON_ONCE(!found);
6306 __lockdep_free_key_range(pf, key, 1);
6307 call_rcu_zapped(pf);
6308 graph_unlock();
6309out_irq:
6310 raw_local_irq_restore(flags);
6311
6312 /* Wait until is_dynamic_key() has finished accessing k->hash_entry. */
6313 synchronize_rcu();
6314}
6315EXPORT_SYMBOL_GPL(lockdep_unregister_key);
6316
6317void __init lockdep_init(void)
6318{
6319 printk("Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar\n");
6320
6321 printk("... MAX_LOCKDEP_SUBCLASSES: %lu\n", MAX_LOCKDEP_SUBCLASSES);
6322 printk("... MAX_LOCK_DEPTH: %lu\n", MAX_LOCK_DEPTH);
6323 printk("... MAX_LOCKDEP_KEYS: %lu\n", MAX_LOCKDEP_KEYS);
6324 printk("... CLASSHASH_SIZE: %lu\n", CLASSHASH_SIZE);
6325 printk("... MAX_LOCKDEP_ENTRIES: %lu\n", MAX_LOCKDEP_ENTRIES);
6326 printk("... MAX_LOCKDEP_CHAINS: %lu\n", MAX_LOCKDEP_CHAINS);
6327 printk("... CHAINHASH_SIZE: %lu\n", CHAINHASH_SIZE);
6328
6329 printk(" memory used by lock dependency info: %zu kB\n",
6330 (sizeof(lock_classes) +
6331 sizeof(lock_classes_in_use) +
6332 sizeof(classhash_table) +
6333 sizeof(list_entries) +
6334 sizeof(list_entries_in_use) +
6335 sizeof(chainhash_table) +
6336 sizeof(delayed_free)
6337#ifdef CONFIG_PROVE_LOCKING
6338 + sizeof(lock_cq)
6339 + sizeof(lock_chains)
6340 + sizeof(lock_chains_in_use)
6341 + sizeof(chain_hlocks)
6342#endif
6343 ) / 1024
6344 );
6345
6346#if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
6347 printk(" memory used for stack traces: %zu kB\n",
6348 (sizeof(stack_trace) + sizeof(stack_trace_hash)) / 1024
6349 );
6350#endif
6351
6352 printk(" per task-struct memory footprint: %zu bytes\n",
6353 sizeof(((struct task_struct *)NULL)->held_locks));
6354}
6355
6356static void
6357print_freed_lock_bug(struct task_struct *curr, const void *mem_from,
6358 const void *mem_to, struct held_lock *hlock)
6359{
6360 if (!debug_locks_off())
6361 return;
6362 if (debug_locks_silent)
6363 return;
6364
6365 pr_warn("\n");
6366 pr_warn("=========================\n");
6367 pr_warn("WARNING: held lock freed!\n");
6368 print_kernel_ident();
6369 pr_warn("-------------------------\n");
6370 pr_warn("%s/%d is freeing memory %px-%px, with a lock still held there!\n",
6371 curr->comm, task_pid_nr(curr), mem_from, mem_to-1);
6372 print_lock(hlock);
6373 lockdep_print_held_locks(curr);
6374
6375 pr_warn("\nstack backtrace:\n");
6376 dump_stack();
6377}
6378
6379static inline int not_in_range(const void* mem_from, unsigned long mem_len,
6380 const void* lock_from, unsigned long lock_len)
6381{
6382 return lock_from + lock_len <= mem_from ||
6383 mem_from + mem_len <= lock_from;
6384}
6385
6386/*
6387 * Called when kernel memory is freed (or unmapped), or if a lock
6388 * is destroyed or reinitialized - this code checks whether there is
6389 * any held lock in the memory range of <from> to <to>:
6390 */
6391void debug_check_no_locks_freed(const void *mem_from, unsigned long mem_len)
6392{
6393 struct task_struct *curr = current;
6394 struct held_lock *hlock;
6395 unsigned long flags;
6396 int i;
6397
6398 if (unlikely(!debug_locks))
6399 return;
6400
6401 raw_local_irq_save(flags);
6402 for (i = 0; i < curr->lockdep_depth; i++) {
6403 hlock = curr->held_locks + i;
6404
6405 if (not_in_range(mem_from, mem_len, hlock->instance,
6406 sizeof(*hlock->instance)))
6407 continue;
6408
6409 print_freed_lock_bug(curr, mem_from, mem_from + mem_len, hlock);
6410 break;
6411 }
6412 raw_local_irq_restore(flags);
6413}
6414EXPORT_SYMBOL_GPL(debug_check_no_locks_freed);
6415
6416static void print_held_locks_bug(void)
6417{
6418 if (!debug_locks_off())
6419 return;
6420 if (debug_locks_silent)
6421 return;
6422
6423 pr_warn("\n");
6424 pr_warn("====================================\n");
6425 pr_warn("WARNING: %s/%d still has locks held!\n",
6426 current->comm, task_pid_nr(current));
6427 print_kernel_ident();
6428 pr_warn("------------------------------------\n");
6429 lockdep_print_held_locks(current);
6430 pr_warn("\nstack backtrace:\n");
6431 dump_stack();
6432}
6433
6434void debug_check_no_locks_held(void)
6435{
6436 if (unlikely(current->lockdep_depth > 0))
6437 print_held_locks_bug();
6438}
6439EXPORT_SYMBOL_GPL(debug_check_no_locks_held);
6440
6441#ifdef __KERNEL__
6442void debug_show_all_locks(void)
6443{
6444 struct task_struct *g, *p;
6445
6446 if (unlikely(!debug_locks)) {
6447 pr_warn("INFO: lockdep is turned off.\n");
6448 return;
6449 }
6450 pr_warn("\nShowing all locks held in the system:\n");
6451
6452 rcu_read_lock();
6453 for_each_process_thread(g, p) {
6454 if (!p->lockdep_depth)
6455 continue;
6456 lockdep_print_held_locks(p);
6457 touch_nmi_watchdog();
6458 touch_all_softlockup_watchdogs();
6459 }
6460 rcu_read_unlock();
6461
6462 pr_warn("\n");
6463 pr_warn("=============================================\n\n");
6464}
6465EXPORT_SYMBOL_GPL(debug_show_all_locks);
6466#endif
6467
6468/*
6469 * Careful: only use this function if you are sure that
6470 * the task cannot run in parallel!
6471 */
6472void debug_show_held_locks(struct task_struct *task)
6473{
6474 if (unlikely(!debug_locks)) {
6475 printk("INFO: lockdep is turned off.\n");
6476 return;
6477 }
6478 lockdep_print_held_locks(task);
6479}
6480EXPORT_SYMBOL_GPL(debug_show_held_locks);
6481
6482asmlinkage __visible void lockdep_sys_exit(void)
6483{
6484 struct task_struct *curr = current;
6485
6486 if (unlikely(curr->lockdep_depth)) {
6487 if (!debug_locks_off())
6488 return;
6489 pr_warn("\n");
6490 pr_warn("================================================\n");
6491 pr_warn("WARNING: lock held when returning to user space!\n");
6492 print_kernel_ident();
6493 pr_warn("------------------------------------------------\n");
6494 pr_warn("%s/%d is leaving the kernel with locks still held!\n",
6495 curr->comm, curr->pid);
6496 lockdep_print_held_locks(curr);
6497 }
6498
6499 /*
6500 * The lock history for each syscall should be independent. So wipe the
6501 * slate clean on return to userspace.
6502 */
6503 lockdep_invariant_state(false);
6504}
6505
6506void lockdep_rcu_suspicious(const char *file, const int line, const char *s)
6507{
6508 struct task_struct *curr = current;
6509 int dl = READ_ONCE(debug_locks);
6510
6511 /* Note: the following can be executed concurrently, so be careful. */
6512 pr_warn("\n");
6513 pr_warn("=============================\n");
6514 pr_warn("WARNING: suspicious RCU usage\n");
6515 print_kernel_ident();
6516 pr_warn("-----------------------------\n");
6517 pr_warn("%s:%d %s!\n", file, line, s);
6518 pr_warn("\nother info that might help us debug this:\n\n");
6519 pr_warn("\n%srcu_scheduler_active = %d, debug_locks = %d\n%s",
6520 !rcu_lockdep_current_cpu_online()
6521 ? "RCU used illegally from offline CPU!\n"
6522 : "",
6523 rcu_scheduler_active, dl,
6524 dl ? "" : "Possible false positive due to lockdep disabling via debug_locks = 0\n");
6525
6526 /*
6527 * If a CPU is in the RCU-free window in idle (ie: in the section
6528 * between rcu_idle_enter() and rcu_idle_exit(), then RCU
6529 * considers that CPU to be in an "extended quiescent state",
6530 * which means that RCU will be completely ignoring that CPU.
6531 * Therefore, rcu_read_lock() and friends have absolutely no
6532 * effect on a CPU running in that state. In other words, even if
6533 * such an RCU-idle CPU has called rcu_read_lock(), RCU might well
6534 * delete data structures out from under it. RCU really has no
6535 * choice here: we need to keep an RCU-free window in idle where
6536 * the CPU may possibly enter into low power mode. This way we can
6537 * notice an extended quiescent state to other CPUs that started a grace
6538 * period. Otherwise we would delay any grace period as long as we run
6539 * in the idle task.
6540 *
6541 * So complain bitterly if someone does call rcu_read_lock(),
6542 * rcu_read_lock_bh() and so on from extended quiescent states.
6543 */
6544 if (!rcu_is_watching())
6545 pr_warn("RCU used illegally from extended quiescent state!\n");
6546
6547 lockdep_print_held_locks(curr);
6548 pr_warn("\nstack backtrace:\n");
6549 dump_stack();
6550}
6551EXPORT_SYMBOL_GPL(lockdep_rcu_suspicious);