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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#include <linux/context_tracking.h>
59#include <linux/console.h>
60
61#include <asm/sections.h>
62
63#include "lockdep_internals.h"
64
65#include <trace/events/lock.h>
66
67#ifdef CONFIG_PROVE_LOCKING
68static int prove_locking = 1;
69module_param(prove_locking, int, 0644);
70#else
71#define prove_locking 0
72#endif
73
74#ifdef CONFIG_LOCK_STAT
75static int lock_stat = 1;
76module_param(lock_stat, int, 0644);
77#else
78#define lock_stat 0
79#endif
80
81#ifdef CONFIG_SYSCTL
82static struct ctl_table kern_lockdep_table[] = {
83#ifdef CONFIG_PROVE_LOCKING
84 {
85 .procname = "prove_locking",
86 .data = &prove_locking,
87 .maxlen = sizeof(int),
88 .mode = 0644,
89 .proc_handler = proc_dointvec,
90 },
91#endif /* CONFIG_PROVE_LOCKING */
92#ifdef CONFIG_LOCK_STAT
93 {
94 .procname = "lock_stat",
95 .data = &lock_stat,
96 .maxlen = sizeof(int),
97 .mode = 0644,
98 .proc_handler = proc_dointvec,
99 },
100#endif /* CONFIG_LOCK_STAT */
101};
102
103static __init int kernel_lockdep_sysctls_init(void)
104{
105 register_sysctl_init("kernel", kern_lockdep_table);
106 return 0;
107}
108late_initcall(kernel_lockdep_sysctls_init);
109#endif /* CONFIG_SYSCTL */
110
111DEFINE_PER_CPU(unsigned int, lockdep_recursion);
112EXPORT_PER_CPU_SYMBOL_GPL(lockdep_recursion);
113
114static __always_inline bool lockdep_enabled(void)
115{
116 if (!debug_locks)
117 return false;
118
119 if (this_cpu_read(lockdep_recursion))
120 return false;
121
122 if (current->lockdep_recursion)
123 return false;
124
125 return true;
126}
127
128/*
129 * lockdep_lock: protects the lockdep graph, the hashes and the
130 * class/list/hash allocators.
131 *
132 * This is one of the rare exceptions where it's justified
133 * to use a raw spinlock - we really dont want the spinlock
134 * code to recurse back into the lockdep code...
135 */
136static arch_spinlock_t __lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED;
137static struct task_struct *__owner;
138
139static inline void lockdep_lock(void)
140{
141 DEBUG_LOCKS_WARN_ON(!irqs_disabled());
142
143 __this_cpu_inc(lockdep_recursion);
144 arch_spin_lock(&__lock);
145 __owner = current;
146}
147
148static inline void lockdep_unlock(void)
149{
150 DEBUG_LOCKS_WARN_ON(!irqs_disabled());
151
152 if (debug_locks && DEBUG_LOCKS_WARN_ON(__owner != current))
153 return;
154
155 __owner = NULL;
156 arch_spin_unlock(&__lock);
157 __this_cpu_dec(lockdep_recursion);
158}
159
160static inline bool lockdep_assert_locked(void)
161{
162 return DEBUG_LOCKS_WARN_ON(__owner != current);
163}
164
165static struct task_struct *lockdep_selftest_task_struct;
166
167
168static int graph_lock(void)
169{
170 lockdep_lock();
171 /*
172 * Make sure that if another CPU detected a bug while
173 * walking the graph we dont change it (while the other
174 * CPU is busy printing out stuff with the graph lock
175 * dropped already)
176 */
177 if (!debug_locks) {
178 lockdep_unlock();
179 return 0;
180 }
181 return 1;
182}
183
184static inline void graph_unlock(void)
185{
186 lockdep_unlock();
187}
188
189/*
190 * Turn lock debugging off and return with 0 if it was off already,
191 * and also release the graph lock:
192 */
193static inline int debug_locks_off_graph_unlock(void)
194{
195 int ret = debug_locks_off();
196
197 lockdep_unlock();
198
199 return ret;
200}
201
202unsigned long nr_list_entries;
203static struct lock_list list_entries[MAX_LOCKDEP_ENTRIES];
204static DECLARE_BITMAP(list_entries_in_use, MAX_LOCKDEP_ENTRIES);
205
206/*
207 * All data structures here are protected by the global debug_lock.
208 *
209 * nr_lock_classes is the number of elements of lock_classes[] that is
210 * in use.
211 */
212#define KEYHASH_BITS (MAX_LOCKDEP_KEYS_BITS - 1)
213#define KEYHASH_SIZE (1UL << KEYHASH_BITS)
214static struct hlist_head lock_keys_hash[KEYHASH_SIZE];
215unsigned long nr_lock_classes;
216unsigned long nr_zapped_classes;
217unsigned long max_lock_class_idx;
218struct lock_class lock_classes[MAX_LOCKDEP_KEYS];
219DECLARE_BITMAP(lock_classes_in_use, MAX_LOCKDEP_KEYS);
220
221static inline struct lock_class *hlock_class(struct held_lock *hlock)
222{
223 unsigned int class_idx = hlock->class_idx;
224
225 /* Don't re-read hlock->class_idx, can't use READ_ONCE() on bitfield */
226 barrier();
227
228 if (!test_bit(class_idx, lock_classes_in_use)) {
229 /*
230 * Someone passed in garbage, we give up.
231 */
232 DEBUG_LOCKS_WARN_ON(1);
233 return NULL;
234 }
235
236 /*
237 * At this point, if the passed hlock->class_idx is still garbage,
238 * we just have to live with it
239 */
240 return lock_classes + class_idx;
241}
242
243#ifdef CONFIG_LOCK_STAT
244static DEFINE_PER_CPU(struct lock_class_stats[MAX_LOCKDEP_KEYS], cpu_lock_stats);
245
246static inline u64 lockstat_clock(void)
247{
248 return local_clock();
249}
250
251static int lock_point(unsigned long points[], unsigned long ip)
252{
253 int i;
254
255 for (i = 0; i < LOCKSTAT_POINTS; i++) {
256 if (points[i] == 0) {
257 points[i] = ip;
258 break;
259 }
260 if (points[i] == ip)
261 break;
262 }
263
264 return i;
265}
266
267static void lock_time_inc(struct lock_time *lt, u64 time)
268{
269 if (time > lt->max)
270 lt->max = time;
271
272 if (time < lt->min || !lt->nr)
273 lt->min = time;
274
275 lt->total += time;
276 lt->nr++;
277}
278
279static inline void lock_time_add(struct lock_time *src, struct lock_time *dst)
280{
281 if (!src->nr)
282 return;
283
284 if (src->max > dst->max)
285 dst->max = src->max;
286
287 if (src->min < dst->min || !dst->nr)
288 dst->min = src->min;
289
290 dst->total += src->total;
291 dst->nr += src->nr;
292}
293
294struct lock_class_stats lock_stats(struct lock_class *class)
295{
296 struct lock_class_stats stats;
297 int cpu, i;
298
299 memset(&stats, 0, sizeof(struct lock_class_stats));
300 for_each_possible_cpu(cpu) {
301 struct lock_class_stats *pcs =
302 &per_cpu(cpu_lock_stats, cpu)[class - lock_classes];
303
304 for (i = 0; i < ARRAY_SIZE(stats.contention_point); i++)
305 stats.contention_point[i] += pcs->contention_point[i];
306
307 for (i = 0; i < ARRAY_SIZE(stats.contending_point); i++)
308 stats.contending_point[i] += pcs->contending_point[i];
309
310 lock_time_add(&pcs->read_waittime, &stats.read_waittime);
311 lock_time_add(&pcs->write_waittime, &stats.write_waittime);
312
313 lock_time_add(&pcs->read_holdtime, &stats.read_holdtime);
314 lock_time_add(&pcs->write_holdtime, &stats.write_holdtime);
315
316 for (i = 0; i < ARRAY_SIZE(stats.bounces); i++)
317 stats.bounces[i] += pcs->bounces[i];
318 }
319
320 return stats;
321}
322
323void clear_lock_stats(struct lock_class *class)
324{
325 int cpu;
326
327 for_each_possible_cpu(cpu) {
328 struct lock_class_stats *cpu_stats =
329 &per_cpu(cpu_lock_stats, cpu)[class - lock_classes];
330
331 memset(cpu_stats, 0, sizeof(struct lock_class_stats));
332 }
333 memset(class->contention_point, 0, sizeof(class->contention_point));
334 memset(class->contending_point, 0, sizeof(class->contending_point));
335}
336
337static struct lock_class_stats *get_lock_stats(struct lock_class *class)
338{
339 return &this_cpu_ptr(cpu_lock_stats)[class - lock_classes];
340}
341
342static void lock_release_holdtime(struct held_lock *hlock)
343{
344 struct lock_class_stats *stats;
345 u64 holdtime;
346
347 if (!lock_stat)
348 return;
349
350 holdtime = lockstat_clock() - hlock->holdtime_stamp;
351
352 stats = get_lock_stats(hlock_class(hlock));
353 if (hlock->read)
354 lock_time_inc(&stats->read_holdtime, holdtime);
355 else
356 lock_time_inc(&stats->write_holdtime, holdtime);
357}
358#else
359static inline void lock_release_holdtime(struct held_lock *hlock)
360{
361}
362#endif
363
364/*
365 * We keep a global list of all lock classes. The list is only accessed with
366 * the lockdep spinlock lock held. free_lock_classes is a list with free
367 * elements. These elements are linked together by the lock_entry member in
368 * struct lock_class.
369 */
370static LIST_HEAD(all_lock_classes);
371static LIST_HEAD(free_lock_classes);
372
373/**
374 * struct pending_free - information about data structures about to be freed
375 * @zapped: Head of a list with struct lock_class elements.
376 * @lock_chains_being_freed: Bitmap that indicates which lock_chains[] elements
377 * are about to be freed.
378 */
379struct pending_free {
380 struct list_head zapped;
381 DECLARE_BITMAP(lock_chains_being_freed, MAX_LOCKDEP_CHAINS);
382};
383
384/**
385 * struct delayed_free - data structures used for delayed freeing
386 *
387 * A data structure for delayed freeing of data structures that may be
388 * accessed by RCU readers at the time these were freed.
389 *
390 * @rcu_head: Used to schedule an RCU callback for freeing data structures.
391 * @index: Index of @pf to which freed data structures are added.
392 * @scheduled: Whether or not an RCU callback has been scheduled.
393 * @pf: Array with information about data structures about to be freed.
394 */
395static struct delayed_free {
396 struct rcu_head rcu_head;
397 int index;
398 int scheduled;
399 struct pending_free pf[2];
400} delayed_free;
401
402/*
403 * The lockdep classes are in a hash-table as well, for fast lookup:
404 */
405#define CLASSHASH_BITS (MAX_LOCKDEP_KEYS_BITS - 1)
406#define CLASSHASH_SIZE (1UL << CLASSHASH_BITS)
407#define __classhashfn(key) hash_long((unsigned long)key, CLASSHASH_BITS)
408#define classhashentry(key) (classhash_table + __classhashfn((key)))
409
410static struct hlist_head classhash_table[CLASSHASH_SIZE];
411
412/*
413 * We put the lock dependency chains into a hash-table as well, to cache
414 * their existence:
415 */
416#define CHAINHASH_BITS (MAX_LOCKDEP_CHAINS_BITS-1)
417#define CHAINHASH_SIZE (1UL << CHAINHASH_BITS)
418#define __chainhashfn(chain) hash_long(chain, CHAINHASH_BITS)
419#define chainhashentry(chain) (chainhash_table + __chainhashfn((chain)))
420
421static struct hlist_head chainhash_table[CHAINHASH_SIZE];
422
423/*
424 * the id of held_lock
425 */
426static inline u16 hlock_id(struct held_lock *hlock)
427{
428 BUILD_BUG_ON(MAX_LOCKDEP_KEYS_BITS + 2 > 16);
429
430 return (hlock->class_idx | (hlock->read << MAX_LOCKDEP_KEYS_BITS));
431}
432
433static inline unsigned int chain_hlock_class_idx(u16 hlock_id)
434{
435 return hlock_id & (MAX_LOCKDEP_KEYS - 1);
436}
437
438/*
439 * The hash key of the lock dependency chains is a hash itself too:
440 * it's a hash of all locks taken up to that lock, including that lock.
441 * It's a 64-bit hash, because it's important for the keys to be
442 * unique.
443 */
444static inline u64 iterate_chain_key(u64 key, u32 idx)
445{
446 u32 k0 = key, k1 = key >> 32;
447
448 __jhash_mix(idx, k0, k1); /* Macro that modifies arguments! */
449
450 return k0 | (u64)k1 << 32;
451}
452
453void lockdep_init_task(struct task_struct *task)
454{
455 task->lockdep_depth = 0; /* no locks held yet */
456 task->curr_chain_key = INITIAL_CHAIN_KEY;
457 task->lockdep_recursion = 0;
458}
459
460static __always_inline void lockdep_recursion_inc(void)
461{
462 __this_cpu_inc(lockdep_recursion);
463}
464
465static __always_inline void lockdep_recursion_finish(void)
466{
467 if (WARN_ON_ONCE(__this_cpu_dec_return(lockdep_recursion)))
468 __this_cpu_write(lockdep_recursion, 0);
469}
470
471void lockdep_set_selftest_task(struct task_struct *task)
472{
473 lockdep_selftest_task_struct = task;
474}
475
476/*
477 * Debugging switches:
478 */
479
480#define VERBOSE 0
481#define VERY_VERBOSE 0
482
483#if VERBOSE
484# define HARDIRQ_VERBOSE 1
485# define SOFTIRQ_VERBOSE 1
486#else
487# define HARDIRQ_VERBOSE 0
488# define SOFTIRQ_VERBOSE 0
489#endif
490
491#if VERBOSE || HARDIRQ_VERBOSE || SOFTIRQ_VERBOSE
492/*
493 * Quick filtering for interesting events:
494 */
495static int class_filter(struct lock_class *class)
496{
497#if 0
498 /* Example */
499 if (class->name_version == 1 &&
500 !strcmp(class->name, "lockname"))
501 return 1;
502 if (class->name_version == 1 &&
503 !strcmp(class->name, "&struct->lockfield"))
504 return 1;
505#endif
506 /* Filter everything else. 1 would be to allow everything else */
507 return 0;
508}
509#endif
510
511static int verbose(struct lock_class *class)
512{
513#if VERBOSE
514 return class_filter(class);
515#endif
516 return 0;
517}
518
519static void print_lockdep_off(const char *bug_msg)
520{
521 printk(KERN_DEBUG "%s\n", bug_msg);
522 printk(KERN_DEBUG "turning off the locking correctness validator.\n");
523#ifdef CONFIG_LOCK_STAT
524 printk(KERN_DEBUG "Please attach the output of /proc/lock_stat to the bug report\n");
525#endif
526}
527
528unsigned long nr_stack_trace_entries;
529
530#ifdef CONFIG_PROVE_LOCKING
531/**
532 * struct lock_trace - single stack backtrace
533 * @hash_entry: Entry in a stack_trace_hash[] list.
534 * @hash: jhash() of @entries.
535 * @nr_entries: Number of entries in @entries.
536 * @entries: Actual stack backtrace.
537 */
538struct lock_trace {
539 struct hlist_node hash_entry;
540 u32 hash;
541 u32 nr_entries;
542 unsigned long entries[] __aligned(sizeof(unsigned long));
543};
544#define LOCK_TRACE_SIZE_IN_LONGS \
545 (sizeof(struct lock_trace) / sizeof(unsigned long))
546/*
547 * Stack-trace: sequence of lock_trace structures. Protected by the graph_lock.
548 */
549static unsigned long stack_trace[MAX_STACK_TRACE_ENTRIES];
550static struct hlist_head stack_trace_hash[STACK_TRACE_HASH_SIZE];
551
552static bool traces_identical(struct lock_trace *t1, struct lock_trace *t2)
553{
554 return t1->hash == t2->hash && t1->nr_entries == t2->nr_entries &&
555 memcmp(t1->entries, t2->entries,
556 t1->nr_entries * sizeof(t1->entries[0])) == 0;
557}
558
559static struct lock_trace *save_trace(void)
560{
561 struct lock_trace *trace, *t2;
562 struct hlist_head *hash_head;
563 u32 hash;
564 int max_entries;
565
566 BUILD_BUG_ON_NOT_POWER_OF_2(STACK_TRACE_HASH_SIZE);
567 BUILD_BUG_ON(LOCK_TRACE_SIZE_IN_LONGS >= MAX_STACK_TRACE_ENTRIES);
568
569 trace = (struct lock_trace *)(stack_trace + nr_stack_trace_entries);
570 max_entries = MAX_STACK_TRACE_ENTRIES - nr_stack_trace_entries -
571 LOCK_TRACE_SIZE_IN_LONGS;
572
573 if (max_entries <= 0) {
574 if (!debug_locks_off_graph_unlock())
575 return NULL;
576
577 nbcon_cpu_emergency_enter();
578 print_lockdep_off("BUG: MAX_STACK_TRACE_ENTRIES too low!");
579 dump_stack();
580 nbcon_cpu_emergency_exit();
581
582 return NULL;
583 }
584 trace->nr_entries = stack_trace_save(trace->entries, max_entries, 3);
585
586 hash = jhash(trace->entries, trace->nr_entries *
587 sizeof(trace->entries[0]), 0);
588 trace->hash = hash;
589 hash_head = stack_trace_hash + (hash & (STACK_TRACE_HASH_SIZE - 1));
590 hlist_for_each_entry(t2, hash_head, hash_entry) {
591 if (traces_identical(trace, t2))
592 return t2;
593 }
594 nr_stack_trace_entries += LOCK_TRACE_SIZE_IN_LONGS + trace->nr_entries;
595 hlist_add_head(&trace->hash_entry, hash_head);
596
597 return trace;
598}
599
600/* Return the number of stack traces in the stack_trace[] array. */
601u64 lockdep_stack_trace_count(void)
602{
603 struct lock_trace *trace;
604 u64 c = 0;
605 int i;
606
607 for (i = 0; i < ARRAY_SIZE(stack_trace_hash); i++) {
608 hlist_for_each_entry(trace, &stack_trace_hash[i], hash_entry) {
609 c++;
610 }
611 }
612
613 return c;
614}
615
616/* Return the number of stack hash chains that have at least one stack trace. */
617u64 lockdep_stack_hash_count(void)
618{
619 u64 c = 0;
620 int i;
621
622 for (i = 0; i < ARRAY_SIZE(stack_trace_hash); i++)
623 if (!hlist_empty(&stack_trace_hash[i]))
624 c++;
625
626 return c;
627}
628#endif
629
630unsigned int nr_hardirq_chains;
631unsigned int nr_softirq_chains;
632unsigned int nr_process_chains;
633unsigned int max_lockdep_depth;
634
635#ifdef CONFIG_DEBUG_LOCKDEP
636/*
637 * Various lockdep statistics:
638 */
639DEFINE_PER_CPU(struct lockdep_stats, lockdep_stats);
640#endif
641
642#ifdef CONFIG_PROVE_LOCKING
643/*
644 * Locking printouts:
645 */
646
647#define __USAGE(__STATE) \
648 [LOCK_USED_IN_##__STATE] = "IN-"__stringify(__STATE)"-W", \
649 [LOCK_ENABLED_##__STATE] = __stringify(__STATE)"-ON-W", \
650 [LOCK_USED_IN_##__STATE##_READ] = "IN-"__stringify(__STATE)"-R",\
651 [LOCK_ENABLED_##__STATE##_READ] = __stringify(__STATE)"-ON-R",
652
653static const char *usage_str[] =
654{
655#define LOCKDEP_STATE(__STATE) __USAGE(__STATE)
656#include "lockdep_states.h"
657#undef LOCKDEP_STATE
658 [LOCK_USED] = "INITIAL USE",
659 [LOCK_USED_READ] = "INITIAL READ USE",
660 /* abused as string storage for verify_lock_unused() */
661 [LOCK_USAGE_STATES] = "IN-NMI",
662};
663#endif
664
665const char *__get_key_name(const struct lockdep_subclass_key *key, char *str)
666{
667 return kallsyms_lookup((unsigned long)key, NULL, NULL, NULL, str);
668}
669
670static inline unsigned long lock_flag(enum lock_usage_bit bit)
671{
672 return 1UL << bit;
673}
674
675static char get_usage_char(struct lock_class *class, enum lock_usage_bit bit)
676{
677 /*
678 * The usage character defaults to '.' (i.e., irqs disabled and not in
679 * irq context), which is the safest usage category.
680 */
681 char c = '.';
682
683 /*
684 * The order of the following usage checks matters, which will
685 * result in the outcome character as follows:
686 *
687 * - '+': irq is enabled and not in irq context
688 * - '-': in irq context and irq is disabled
689 * - '?': in irq context and irq is enabled
690 */
691 if (class->usage_mask & lock_flag(bit + LOCK_USAGE_DIR_MASK)) {
692 c = '+';
693 if (class->usage_mask & lock_flag(bit))
694 c = '?';
695 } else if (class->usage_mask & lock_flag(bit))
696 c = '-';
697
698 return c;
699}
700
701void get_usage_chars(struct lock_class *class, char usage[LOCK_USAGE_CHARS])
702{
703 int i = 0;
704
705#define LOCKDEP_STATE(__STATE) \
706 usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE); \
707 usage[i++] = get_usage_char(class, LOCK_USED_IN_##__STATE##_READ);
708#include "lockdep_states.h"
709#undef LOCKDEP_STATE
710
711 usage[i] = '\0';
712}
713
714static void __print_lock_name(struct held_lock *hlock, struct lock_class *class)
715{
716 char str[KSYM_NAME_LEN];
717 const char *name;
718
719 name = class->name;
720 if (!name) {
721 name = __get_key_name(class->key, str);
722 printk(KERN_CONT "%s", name);
723 } else {
724 printk(KERN_CONT "%s", name);
725 if (class->name_version > 1)
726 printk(KERN_CONT "#%d", class->name_version);
727 if (class->subclass)
728 printk(KERN_CONT "/%d", class->subclass);
729 if (hlock && class->print_fn)
730 class->print_fn(hlock->instance);
731 }
732}
733
734static void print_lock_name(struct held_lock *hlock, struct lock_class *class)
735{
736 char usage[LOCK_USAGE_CHARS];
737
738 get_usage_chars(class, usage);
739
740 printk(KERN_CONT " (");
741 __print_lock_name(hlock, class);
742 printk(KERN_CONT "){%s}-{%d:%d}", usage,
743 class->wait_type_outer ?: class->wait_type_inner,
744 class->wait_type_inner);
745}
746
747static void print_lockdep_cache(struct lockdep_map *lock)
748{
749 const char *name;
750 char str[KSYM_NAME_LEN];
751
752 name = lock->name;
753 if (!name)
754 name = __get_key_name(lock->key->subkeys, str);
755
756 printk(KERN_CONT "%s", name);
757}
758
759static void print_lock(struct held_lock *hlock)
760{
761 /*
762 * We can be called locklessly through debug_show_all_locks() so be
763 * extra careful, the hlock might have been released and cleared.
764 *
765 * If this indeed happens, lets pretend it does not hurt to continue
766 * to print the lock unless the hlock class_idx does not point to a
767 * registered class. The rationale here is: since we don't attempt
768 * to distinguish whether we are in this situation, if it just
769 * happened we can't count on class_idx to tell either.
770 */
771 struct lock_class *lock = hlock_class(hlock);
772
773 if (!lock) {
774 printk(KERN_CONT "<RELEASED>\n");
775 return;
776 }
777
778 printk(KERN_CONT "%px", hlock->instance);
779 print_lock_name(hlock, lock);
780 printk(KERN_CONT ", at: %pS\n", (void *)hlock->acquire_ip);
781}
782
783static void lockdep_print_held_locks(struct task_struct *p)
784{
785 int i, depth = READ_ONCE(p->lockdep_depth);
786
787 if (!depth)
788 printk("no locks held by %s/%d.\n", p->comm, task_pid_nr(p));
789 else
790 printk("%d lock%s held by %s/%d:\n", depth,
791 str_plural(depth), p->comm, task_pid_nr(p));
792 /*
793 * It's not reliable to print a task's held locks if it's not sleeping
794 * and it's not the current task.
795 */
796 if (p != current && task_is_running(p))
797 return;
798 for (i = 0; i < depth; i++) {
799 printk(" #%d: ", i);
800 print_lock(p->held_locks + i);
801 }
802}
803
804static void print_kernel_ident(void)
805{
806 printk("%s %.*s %s\n", init_utsname()->release,
807 (int)strcspn(init_utsname()->version, " "),
808 init_utsname()->version,
809 print_tainted());
810}
811
812static int very_verbose(struct lock_class *class)
813{
814#if VERY_VERBOSE
815 return class_filter(class);
816#endif
817 return 0;
818}
819
820/*
821 * Is this the address of a static object:
822 */
823#ifdef __KERNEL__
824static int static_obj(const void *obj)
825{
826 unsigned long addr = (unsigned long) obj;
827
828 if (is_kernel_core_data(addr))
829 return 1;
830
831 /*
832 * keys are allowed in the __ro_after_init section.
833 */
834 if (is_kernel_rodata(addr))
835 return 1;
836
837 /*
838 * in initdata section and used during bootup only?
839 * NOTE: On some platforms the initdata section is
840 * outside of the _stext ... _end range.
841 */
842 if (system_state < SYSTEM_FREEING_INITMEM &&
843 init_section_contains((void *)addr, 1))
844 return 1;
845
846 /*
847 * in-kernel percpu var?
848 */
849 if (is_kernel_percpu_address(addr))
850 return 1;
851
852 /*
853 * module static or percpu var?
854 */
855 return is_module_address(addr) || is_module_percpu_address(addr);
856}
857#endif
858
859/*
860 * To make lock name printouts unique, we calculate a unique
861 * class->name_version generation counter. The caller must hold the graph
862 * lock.
863 */
864static int count_matching_names(struct lock_class *new_class)
865{
866 struct lock_class *class;
867 int count = 0;
868
869 if (!new_class->name)
870 return 0;
871
872 list_for_each_entry(class, &all_lock_classes, lock_entry) {
873 if (new_class->key - new_class->subclass == class->key)
874 return class->name_version;
875 if (class->name && !strcmp(class->name, new_class->name))
876 count = max(count, class->name_version);
877 }
878
879 return count + 1;
880}
881
882/* used from NMI context -- must be lockless */
883static noinstr struct lock_class *
884look_up_lock_class(const struct lockdep_map *lock, unsigned int subclass)
885{
886 struct lockdep_subclass_key *key;
887 struct hlist_head *hash_head;
888 struct lock_class *class;
889
890 if (unlikely(subclass >= MAX_LOCKDEP_SUBCLASSES)) {
891 instrumentation_begin();
892 debug_locks_off();
893 nbcon_cpu_emergency_enter();
894 printk(KERN_ERR
895 "BUG: looking up invalid subclass: %u\n", subclass);
896 printk(KERN_ERR
897 "turning off the locking correctness validator.\n");
898 dump_stack();
899 nbcon_cpu_emergency_exit();
900 instrumentation_end();
901 return NULL;
902 }
903
904 /*
905 * If it is not initialised then it has never been locked,
906 * so it won't be present in the hash table.
907 */
908 if (unlikely(!lock->key))
909 return NULL;
910
911 /*
912 * NOTE: the class-key must be unique. For dynamic locks, a static
913 * lock_class_key variable is passed in through the mutex_init()
914 * (or spin_lock_init()) call - which acts as the key. For static
915 * locks we use the lock object itself as the key.
916 */
917 BUILD_BUG_ON(sizeof(struct lock_class_key) >
918 sizeof(struct lockdep_map));
919
920 key = lock->key->subkeys + subclass;
921
922 hash_head = classhashentry(key);
923
924 /*
925 * We do an RCU walk of the hash, see lockdep_free_key_range().
926 */
927 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
928 return NULL;
929
930 hlist_for_each_entry_rcu_notrace(class, hash_head, hash_entry) {
931 if (class->key == key) {
932 /*
933 * Huh! same key, different name? Did someone trample
934 * on some memory? We're most confused.
935 */
936 WARN_ONCE(class->name != lock->name &&
937 lock->key != &__lockdep_no_validate__,
938 "Looking for class \"%s\" with key %ps, but found a different class \"%s\" with the same key\n",
939 lock->name, lock->key, class->name);
940 return class;
941 }
942 }
943
944 return NULL;
945}
946
947/*
948 * Static locks do not have their class-keys yet - for them the key is
949 * the lock object itself. If the lock is in the per cpu area, the
950 * canonical address of the lock (per cpu offset removed) is used.
951 */
952static bool assign_lock_key(struct lockdep_map *lock)
953{
954 unsigned long can_addr, addr = (unsigned long)lock;
955
956#ifdef __KERNEL__
957 /*
958 * lockdep_free_key_range() assumes that struct lock_class_key
959 * objects do not overlap. Since we use the address of lock
960 * objects as class key for static objects, check whether the
961 * size of lock_class_key objects does not exceed the size of
962 * the smallest lock object.
963 */
964 BUILD_BUG_ON(sizeof(struct lock_class_key) > sizeof(raw_spinlock_t));
965#endif
966
967 if (__is_kernel_percpu_address(addr, &can_addr))
968 lock->key = (void *)can_addr;
969 else if (__is_module_percpu_address(addr, &can_addr))
970 lock->key = (void *)can_addr;
971 else if (static_obj(lock))
972 lock->key = (void *)lock;
973 else {
974 /* Debug-check: all keys must be persistent! */
975 debug_locks_off();
976 nbcon_cpu_emergency_enter();
977 pr_err("INFO: trying to register non-static key.\n");
978 pr_err("The code is fine but needs lockdep annotation, or maybe\n");
979 pr_err("you didn't initialize this object before use?\n");
980 pr_err("turning off the locking correctness validator.\n");
981 dump_stack();
982 nbcon_cpu_emergency_exit();
983 return false;
984 }
985
986 return true;
987}
988
989#ifdef CONFIG_DEBUG_LOCKDEP
990
991/* Check whether element @e occurs in list @h */
992static bool in_list(struct list_head *e, struct list_head *h)
993{
994 struct list_head *f;
995
996 list_for_each(f, h) {
997 if (e == f)
998 return true;
999 }
1000
1001 return false;
1002}
1003
1004/*
1005 * Check whether entry @e occurs in any of the locks_after or locks_before
1006 * lists.
1007 */
1008static bool in_any_class_list(struct list_head *e)
1009{
1010 struct lock_class *class;
1011 int i;
1012
1013 for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
1014 class = &lock_classes[i];
1015 if (in_list(e, &class->locks_after) ||
1016 in_list(e, &class->locks_before))
1017 return true;
1018 }
1019 return false;
1020}
1021
1022static bool class_lock_list_valid(struct lock_class *c, struct list_head *h)
1023{
1024 struct lock_list *e;
1025
1026 list_for_each_entry(e, h, entry) {
1027 if (e->links_to != c) {
1028 printk(KERN_INFO "class %s: mismatch for lock entry %ld; class %s <> %s",
1029 c->name ? : "(?)",
1030 (unsigned long)(e - list_entries),
1031 e->links_to && e->links_to->name ?
1032 e->links_to->name : "(?)",
1033 e->class && e->class->name ? e->class->name :
1034 "(?)");
1035 return false;
1036 }
1037 }
1038 return true;
1039}
1040
1041#ifdef CONFIG_PROVE_LOCKING
1042static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
1043#endif
1044
1045static bool check_lock_chain_key(struct lock_chain *chain)
1046{
1047#ifdef CONFIG_PROVE_LOCKING
1048 u64 chain_key = INITIAL_CHAIN_KEY;
1049 int i;
1050
1051 for (i = chain->base; i < chain->base + chain->depth; i++)
1052 chain_key = iterate_chain_key(chain_key, chain_hlocks[i]);
1053 /*
1054 * The 'unsigned long long' casts avoid that a compiler warning
1055 * is reported when building tools/lib/lockdep.
1056 */
1057 if (chain->chain_key != chain_key) {
1058 printk(KERN_INFO "chain %lld: key %#llx <> %#llx\n",
1059 (unsigned long long)(chain - lock_chains),
1060 (unsigned long long)chain->chain_key,
1061 (unsigned long long)chain_key);
1062 return false;
1063 }
1064#endif
1065 return true;
1066}
1067
1068static bool in_any_zapped_class_list(struct lock_class *class)
1069{
1070 struct pending_free *pf;
1071 int i;
1072
1073 for (i = 0, pf = delayed_free.pf; i < ARRAY_SIZE(delayed_free.pf); i++, pf++) {
1074 if (in_list(&class->lock_entry, &pf->zapped))
1075 return true;
1076 }
1077
1078 return false;
1079}
1080
1081static bool __check_data_structures(void)
1082{
1083 struct lock_class *class;
1084 struct lock_chain *chain;
1085 struct hlist_head *head;
1086 struct lock_list *e;
1087 int i;
1088
1089 /* Check whether all classes occur in a lock list. */
1090 for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
1091 class = &lock_classes[i];
1092 if (!in_list(&class->lock_entry, &all_lock_classes) &&
1093 !in_list(&class->lock_entry, &free_lock_classes) &&
1094 !in_any_zapped_class_list(class)) {
1095 printk(KERN_INFO "class %px/%s is not in any class list\n",
1096 class, class->name ? : "(?)");
1097 return false;
1098 }
1099 }
1100
1101 /* Check whether all classes have valid lock lists. */
1102 for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
1103 class = &lock_classes[i];
1104 if (!class_lock_list_valid(class, &class->locks_before))
1105 return false;
1106 if (!class_lock_list_valid(class, &class->locks_after))
1107 return false;
1108 }
1109
1110 /* Check the chain_key of all lock chains. */
1111 for (i = 0; i < ARRAY_SIZE(chainhash_table); i++) {
1112 head = chainhash_table + i;
1113 hlist_for_each_entry_rcu(chain, head, entry) {
1114 if (!check_lock_chain_key(chain))
1115 return false;
1116 }
1117 }
1118
1119 /*
1120 * Check whether all list entries that are in use occur in a class
1121 * lock list.
1122 */
1123 for_each_set_bit(i, list_entries_in_use, ARRAY_SIZE(list_entries)) {
1124 e = list_entries + i;
1125 if (!in_any_class_list(&e->entry)) {
1126 printk(KERN_INFO "list entry %d is not in any class list; class %s <> %s\n",
1127 (unsigned int)(e - list_entries),
1128 e->class->name ? : "(?)",
1129 e->links_to->name ? : "(?)");
1130 return false;
1131 }
1132 }
1133
1134 /*
1135 * Check whether all list entries that are not in use do not occur in
1136 * a class lock list.
1137 */
1138 for_each_clear_bit(i, list_entries_in_use, ARRAY_SIZE(list_entries)) {
1139 e = list_entries + i;
1140 if (in_any_class_list(&e->entry)) {
1141 printk(KERN_INFO "list entry %d occurs in a class list; class %s <> %s\n",
1142 (unsigned int)(e - list_entries),
1143 e->class && e->class->name ? e->class->name :
1144 "(?)",
1145 e->links_to && e->links_to->name ?
1146 e->links_to->name : "(?)");
1147 return false;
1148 }
1149 }
1150
1151 return true;
1152}
1153
1154int check_consistency = 0;
1155module_param(check_consistency, int, 0644);
1156
1157static void check_data_structures(void)
1158{
1159 static bool once = false;
1160
1161 if (check_consistency && !once) {
1162 if (!__check_data_structures()) {
1163 once = true;
1164 WARN_ON(once);
1165 }
1166 }
1167}
1168
1169#else /* CONFIG_DEBUG_LOCKDEP */
1170
1171static inline void check_data_structures(void) { }
1172
1173#endif /* CONFIG_DEBUG_LOCKDEP */
1174
1175static void init_chain_block_buckets(void);
1176
1177/*
1178 * Initialize the lock_classes[] array elements, the free_lock_classes list
1179 * and also the delayed_free structure.
1180 */
1181static void init_data_structures_once(void)
1182{
1183 static bool __read_mostly ds_initialized, rcu_head_initialized;
1184 int i;
1185
1186 if (likely(rcu_head_initialized))
1187 return;
1188
1189 if (system_state >= SYSTEM_SCHEDULING) {
1190 init_rcu_head(&delayed_free.rcu_head);
1191 rcu_head_initialized = true;
1192 }
1193
1194 if (ds_initialized)
1195 return;
1196
1197 ds_initialized = true;
1198
1199 INIT_LIST_HEAD(&delayed_free.pf[0].zapped);
1200 INIT_LIST_HEAD(&delayed_free.pf[1].zapped);
1201
1202 for (i = 0; i < ARRAY_SIZE(lock_classes); i++) {
1203 list_add_tail(&lock_classes[i].lock_entry, &free_lock_classes);
1204 INIT_LIST_HEAD(&lock_classes[i].locks_after);
1205 INIT_LIST_HEAD(&lock_classes[i].locks_before);
1206 }
1207 init_chain_block_buckets();
1208}
1209
1210static inline struct hlist_head *keyhashentry(const struct lock_class_key *key)
1211{
1212 unsigned long hash = hash_long((uintptr_t)key, KEYHASH_BITS);
1213
1214 return lock_keys_hash + hash;
1215}
1216
1217/* Register a dynamically allocated key. */
1218void lockdep_register_key(struct lock_class_key *key)
1219{
1220 struct hlist_head *hash_head;
1221 struct lock_class_key *k;
1222 unsigned long flags;
1223
1224 if (WARN_ON_ONCE(static_obj(key)))
1225 return;
1226 hash_head = keyhashentry(key);
1227
1228 raw_local_irq_save(flags);
1229 if (!graph_lock())
1230 goto restore_irqs;
1231 hlist_for_each_entry_rcu(k, hash_head, hash_entry) {
1232 if (WARN_ON_ONCE(k == key))
1233 goto out_unlock;
1234 }
1235 hlist_add_head_rcu(&key->hash_entry, hash_head);
1236out_unlock:
1237 graph_unlock();
1238restore_irqs:
1239 raw_local_irq_restore(flags);
1240}
1241EXPORT_SYMBOL_GPL(lockdep_register_key);
1242
1243/* Check whether a key has been registered as a dynamic key. */
1244static bool is_dynamic_key(const struct lock_class_key *key)
1245{
1246 struct hlist_head *hash_head;
1247 struct lock_class_key *k;
1248 bool found = false;
1249
1250 if (WARN_ON_ONCE(static_obj(key)))
1251 return false;
1252
1253 /*
1254 * If lock debugging is disabled lock_keys_hash[] may contain
1255 * pointers to memory that has already been freed. Avoid triggering
1256 * a use-after-free in that case by returning early.
1257 */
1258 if (!debug_locks)
1259 return true;
1260
1261 hash_head = keyhashentry(key);
1262
1263 rcu_read_lock();
1264 hlist_for_each_entry_rcu(k, hash_head, hash_entry) {
1265 if (k == key) {
1266 found = true;
1267 break;
1268 }
1269 }
1270 rcu_read_unlock();
1271
1272 return found;
1273}
1274
1275/*
1276 * Register a lock's class in the hash-table, if the class is not present
1277 * yet. Otherwise we look it up. We cache the result in the lock object
1278 * itself, so actual lookup of the hash should be once per lock object.
1279 */
1280static struct lock_class *
1281register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force)
1282{
1283 struct lockdep_subclass_key *key;
1284 struct hlist_head *hash_head;
1285 struct lock_class *class;
1286 int idx;
1287
1288 DEBUG_LOCKS_WARN_ON(!irqs_disabled());
1289
1290 class = look_up_lock_class(lock, subclass);
1291 if (likely(class))
1292 goto out_set_class_cache;
1293
1294 if (!lock->key) {
1295 if (!assign_lock_key(lock))
1296 return NULL;
1297 } else if (!static_obj(lock->key) && !is_dynamic_key(lock->key)) {
1298 return NULL;
1299 }
1300
1301 key = lock->key->subkeys + subclass;
1302 hash_head = classhashentry(key);
1303
1304 if (!graph_lock()) {
1305 return NULL;
1306 }
1307 /*
1308 * We have to do the hash-walk again, to avoid races
1309 * with another CPU:
1310 */
1311 hlist_for_each_entry_rcu(class, hash_head, hash_entry) {
1312 if (class->key == key)
1313 goto out_unlock_set;
1314 }
1315
1316 init_data_structures_once();
1317
1318 /* Allocate a new lock class and add it to the hash. */
1319 class = list_first_entry_or_null(&free_lock_classes, typeof(*class),
1320 lock_entry);
1321 if (!class) {
1322 if (!debug_locks_off_graph_unlock()) {
1323 return NULL;
1324 }
1325
1326 nbcon_cpu_emergency_enter();
1327 print_lockdep_off("BUG: MAX_LOCKDEP_KEYS too low!");
1328 dump_stack();
1329 nbcon_cpu_emergency_exit();
1330 return NULL;
1331 }
1332 nr_lock_classes++;
1333 __set_bit(class - lock_classes, lock_classes_in_use);
1334 debug_atomic_inc(nr_unused_locks);
1335 class->key = key;
1336 class->name = lock->name;
1337 class->subclass = subclass;
1338 WARN_ON_ONCE(!list_empty(&class->locks_before));
1339 WARN_ON_ONCE(!list_empty(&class->locks_after));
1340 class->name_version = count_matching_names(class);
1341 class->wait_type_inner = lock->wait_type_inner;
1342 class->wait_type_outer = lock->wait_type_outer;
1343 class->lock_type = lock->lock_type;
1344 /*
1345 * We use RCU's safe list-add method to make
1346 * parallel walking of the hash-list safe:
1347 */
1348 hlist_add_head_rcu(&class->hash_entry, hash_head);
1349 /*
1350 * Remove the class from the free list and add it to the global list
1351 * of classes.
1352 */
1353 list_move_tail(&class->lock_entry, &all_lock_classes);
1354 idx = class - lock_classes;
1355 if (idx > max_lock_class_idx)
1356 max_lock_class_idx = idx;
1357
1358 if (verbose(class)) {
1359 graph_unlock();
1360
1361 nbcon_cpu_emergency_enter();
1362 printk("\nnew class %px: %s", class->key, class->name);
1363 if (class->name_version > 1)
1364 printk(KERN_CONT "#%d", class->name_version);
1365 printk(KERN_CONT "\n");
1366 dump_stack();
1367 nbcon_cpu_emergency_exit();
1368
1369 if (!graph_lock()) {
1370 return NULL;
1371 }
1372 }
1373out_unlock_set:
1374 graph_unlock();
1375
1376out_set_class_cache:
1377 if (!subclass || force)
1378 lock->class_cache[0] = class;
1379 else if (subclass < NR_LOCKDEP_CACHING_CLASSES)
1380 lock->class_cache[subclass] = class;
1381
1382 /*
1383 * Hash collision, did we smoke some? We found a class with a matching
1384 * hash but the subclass -- which is hashed in -- didn't match.
1385 */
1386 if (DEBUG_LOCKS_WARN_ON(class->subclass != subclass))
1387 return NULL;
1388
1389 return class;
1390}
1391
1392#ifdef CONFIG_PROVE_LOCKING
1393/*
1394 * Allocate a lockdep entry. (assumes the graph_lock held, returns
1395 * with NULL on failure)
1396 */
1397static struct lock_list *alloc_list_entry(void)
1398{
1399 int idx = find_first_zero_bit(list_entries_in_use,
1400 ARRAY_SIZE(list_entries));
1401
1402 if (idx >= ARRAY_SIZE(list_entries)) {
1403 if (!debug_locks_off_graph_unlock())
1404 return NULL;
1405
1406 nbcon_cpu_emergency_enter();
1407 print_lockdep_off("BUG: MAX_LOCKDEP_ENTRIES too low!");
1408 dump_stack();
1409 nbcon_cpu_emergency_exit();
1410 return NULL;
1411 }
1412 nr_list_entries++;
1413 __set_bit(idx, list_entries_in_use);
1414 return list_entries + idx;
1415}
1416
1417/*
1418 * Add a new dependency to the head of the list:
1419 */
1420static int add_lock_to_list(struct lock_class *this,
1421 struct lock_class *links_to, struct list_head *head,
1422 u16 distance, u8 dep,
1423 const struct lock_trace *trace)
1424{
1425 struct lock_list *entry;
1426 /*
1427 * Lock not present yet - get a new dependency struct and
1428 * add it to the list:
1429 */
1430 entry = alloc_list_entry();
1431 if (!entry)
1432 return 0;
1433
1434 entry->class = this;
1435 entry->links_to = links_to;
1436 entry->dep = dep;
1437 entry->distance = distance;
1438 entry->trace = trace;
1439 /*
1440 * Both allocation and removal are done under the graph lock; but
1441 * iteration is under RCU-sched; see look_up_lock_class() and
1442 * lockdep_free_key_range().
1443 */
1444 list_add_tail_rcu(&entry->entry, head);
1445
1446 return 1;
1447}
1448
1449/*
1450 * For good efficiency of modular, we use power of 2
1451 */
1452#define MAX_CIRCULAR_QUEUE_SIZE (1UL << CONFIG_LOCKDEP_CIRCULAR_QUEUE_BITS)
1453#define CQ_MASK (MAX_CIRCULAR_QUEUE_SIZE-1)
1454
1455/*
1456 * The circular_queue and helpers are used to implement graph
1457 * breadth-first search (BFS) algorithm, by which we can determine
1458 * whether there is a path from a lock to another. In deadlock checks,
1459 * a path from the next lock to be acquired to a previous held lock
1460 * indicates that adding the <prev> -> <next> lock dependency will
1461 * produce a circle in the graph. Breadth-first search instead of
1462 * depth-first search is used in order to find the shortest (circular)
1463 * path.
1464 */
1465struct circular_queue {
1466 struct lock_list *element[MAX_CIRCULAR_QUEUE_SIZE];
1467 unsigned int front, rear;
1468};
1469
1470static struct circular_queue lock_cq;
1471
1472unsigned int max_bfs_queue_depth;
1473
1474static unsigned int lockdep_dependency_gen_id;
1475
1476static inline void __cq_init(struct circular_queue *cq)
1477{
1478 cq->front = cq->rear = 0;
1479 lockdep_dependency_gen_id++;
1480}
1481
1482static inline int __cq_empty(struct circular_queue *cq)
1483{
1484 return (cq->front == cq->rear);
1485}
1486
1487static inline int __cq_full(struct circular_queue *cq)
1488{
1489 return ((cq->rear + 1) & CQ_MASK) == cq->front;
1490}
1491
1492static inline int __cq_enqueue(struct circular_queue *cq, struct lock_list *elem)
1493{
1494 if (__cq_full(cq))
1495 return -1;
1496
1497 cq->element[cq->rear] = elem;
1498 cq->rear = (cq->rear + 1) & CQ_MASK;
1499 return 0;
1500}
1501
1502/*
1503 * Dequeue an element from the circular_queue, return a lock_list if
1504 * the queue is not empty, or NULL if otherwise.
1505 */
1506static inline struct lock_list * __cq_dequeue(struct circular_queue *cq)
1507{
1508 struct lock_list * lock;
1509
1510 if (__cq_empty(cq))
1511 return NULL;
1512
1513 lock = cq->element[cq->front];
1514 cq->front = (cq->front + 1) & CQ_MASK;
1515
1516 return lock;
1517}
1518
1519static inline unsigned int __cq_get_elem_count(struct circular_queue *cq)
1520{
1521 return (cq->rear - cq->front) & CQ_MASK;
1522}
1523
1524static inline void mark_lock_accessed(struct lock_list *lock)
1525{
1526 lock->class->dep_gen_id = lockdep_dependency_gen_id;
1527}
1528
1529static inline void visit_lock_entry(struct lock_list *lock,
1530 struct lock_list *parent)
1531{
1532 lock->parent = parent;
1533}
1534
1535static inline unsigned long lock_accessed(struct lock_list *lock)
1536{
1537 return lock->class->dep_gen_id == lockdep_dependency_gen_id;
1538}
1539
1540static inline struct lock_list *get_lock_parent(struct lock_list *child)
1541{
1542 return child->parent;
1543}
1544
1545static inline int get_lock_depth(struct lock_list *child)
1546{
1547 int depth = 0;
1548 struct lock_list *parent;
1549
1550 while ((parent = get_lock_parent(child))) {
1551 child = parent;
1552 depth++;
1553 }
1554 return depth;
1555}
1556
1557/*
1558 * Return the forward or backward dependency list.
1559 *
1560 * @lock: the lock_list to get its class's dependency list
1561 * @offset: the offset to struct lock_class to determine whether it is
1562 * locks_after or locks_before
1563 */
1564static inline struct list_head *get_dep_list(struct lock_list *lock, int offset)
1565{
1566 void *lock_class = lock->class;
1567
1568 return lock_class + offset;
1569}
1570/*
1571 * Return values of a bfs search:
1572 *
1573 * BFS_E* indicates an error
1574 * BFS_R* indicates a result (match or not)
1575 *
1576 * BFS_EINVALIDNODE: Find a invalid node in the graph.
1577 *
1578 * BFS_EQUEUEFULL: The queue is full while doing the bfs.
1579 *
1580 * BFS_RMATCH: Find the matched node in the graph, and put that node into
1581 * *@target_entry.
1582 *
1583 * BFS_RNOMATCH: Haven't found the matched node and keep *@target_entry
1584 * _unchanged_.
1585 */
1586enum bfs_result {
1587 BFS_EINVALIDNODE = -2,
1588 BFS_EQUEUEFULL = -1,
1589 BFS_RMATCH = 0,
1590 BFS_RNOMATCH = 1,
1591};
1592
1593/*
1594 * bfs_result < 0 means error
1595 */
1596static inline bool bfs_error(enum bfs_result res)
1597{
1598 return res < 0;
1599}
1600
1601/*
1602 * DEP_*_BIT in lock_list::dep
1603 *
1604 * For dependency @prev -> @next:
1605 *
1606 * SR: @prev is shared reader (->read != 0) and @next is recursive reader
1607 * (->read == 2)
1608 * ER: @prev is exclusive locker (->read == 0) and @next is recursive reader
1609 * SN: @prev is shared reader and @next is non-recursive locker (->read != 2)
1610 * EN: @prev is exclusive locker and @next is non-recursive locker
1611 *
1612 * Note that we define the value of DEP_*_BITs so that:
1613 * bit0 is prev->read == 0
1614 * bit1 is next->read != 2
1615 */
1616#define DEP_SR_BIT (0 + (0 << 1)) /* 0 */
1617#define DEP_ER_BIT (1 + (0 << 1)) /* 1 */
1618#define DEP_SN_BIT (0 + (1 << 1)) /* 2 */
1619#define DEP_EN_BIT (1 + (1 << 1)) /* 3 */
1620
1621#define DEP_SR_MASK (1U << (DEP_SR_BIT))
1622#define DEP_ER_MASK (1U << (DEP_ER_BIT))
1623#define DEP_SN_MASK (1U << (DEP_SN_BIT))
1624#define DEP_EN_MASK (1U << (DEP_EN_BIT))
1625
1626static inline unsigned int
1627__calc_dep_bit(struct held_lock *prev, struct held_lock *next)
1628{
1629 return (prev->read == 0) + ((next->read != 2) << 1);
1630}
1631
1632static inline u8 calc_dep(struct held_lock *prev, struct held_lock *next)
1633{
1634 return 1U << __calc_dep_bit(prev, next);
1635}
1636
1637/*
1638 * calculate the dep_bit for backwards edges. We care about whether @prev is
1639 * shared and whether @next is recursive.
1640 */
1641static inline unsigned int
1642__calc_dep_bitb(struct held_lock *prev, struct held_lock *next)
1643{
1644 return (next->read != 2) + ((prev->read == 0) << 1);
1645}
1646
1647static inline u8 calc_depb(struct held_lock *prev, struct held_lock *next)
1648{
1649 return 1U << __calc_dep_bitb(prev, next);
1650}
1651
1652/*
1653 * Initialize a lock_list entry @lock belonging to @class as the root for a BFS
1654 * search.
1655 */
1656static inline void __bfs_init_root(struct lock_list *lock,
1657 struct lock_class *class)
1658{
1659 lock->class = class;
1660 lock->parent = NULL;
1661 lock->only_xr = 0;
1662}
1663
1664/*
1665 * Initialize a lock_list entry @lock based on a lock acquisition @hlock as the
1666 * root for a BFS search.
1667 *
1668 * ->only_xr of the initial lock node is set to @hlock->read == 2, to make sure
1669 * that <prev> -> @hlock and @hlock -> <whatever __bfs() found> is not -(*R)->
1670 * and -(S*)->.
1671 */
1672static inline void bfs_init_root(struct lock_list *lock,
1673 struct held_lock *hlock)
1674{
1675 __bfs_init_root(lock, hlock_class(hlock));
1676 lock->only_xr = (hlock->read == 2);
1677}
1678
1679/*
1680 * Similar to bfs_init_root() but initialize the root for backwards BFS.
1681 *
1682 * ->only_xr of the initial lock node is set to @hlock->read != 0, to make sure
1683 * that <next> -> @hlock and @hlock -> <whatever backwards BFS found> is not
1684 * -(*S)-> and -(R*)-> (reverse order of -(*R)-> and -(S*)->).
1685 */
1686static inline void bfs_init_rootb(struct lock_list *lock,
1687 struct held_lock *hlock)
1688{
1689 __bfs_init_root(lock, hlock_class(hlock));
1690 lock->only_xr = (hlock->read != 0);
1691}
1692
1693static inline struct lock_list *__bfs_next(struct lock_list *lock, int offset)
1694{
1695 if (!lock || !lock->parent)
1696 return NULL;
1697
1698 return list_next_or_null_rcu(get_dep_list(lock->parent, offset),
1699 &lock->entry, struct lock_list, entry);
1700}
1701
1702/*
1703 * Breadth-First Search to find a strong path in the dependency graph.
1704 *
1705 * @source_entry: the source of the path we are searching for.
1706 * @data: data used for the second parameter of @match function
1707 * @match: match function for the search
1708 * @target_entry: pointer to the target of a matched path
1709 * @offset: the offset to struct lock_class to determine whether it is
1710 * locks_after or locks_before
1711 *
1712 * We may have multiple edges (considering different kinds of dependencies,
1713 * e.g. ER and SN) between two nodes in the dependency graph. But
1714 * only the strong dependency path in the graph is relevant to deadlocks. A
1715 * strong dependency path is a dependency path that doesn't have two adjacent
1716 * dependencies as -(*R)-> -(S*)->, please see:
1717 *
1718 * Documentation/locking/lockdep-design.rst
1719 *
1720 * for more explanation of the definition of strong dependency paths
1721 *
1722 * In __bfs(), we only traverse in the strong dependency path:
1723 *
1724 * In lock_list::only_xr, we record whether the previous dependency only
1725 * has -(*R)-> in the search, and if it does (prev only has -(*R)->), we
1726 * filter out any -(S*)-> in the current dependency and after that, the
1727 * ->only_xr is set according to whether we only have -(*R)-> left.
1728 */
1729static enum bfs_result __bfs(struct lock_list *source_entry,
1730 void *data,
1731 bool (*match)(struct lock_list *entry, void *data),
1732 bool (*skip)(struct lock_list *entry, void *data),
1733 struct lock_list **target_entry,
1734 int offset)
1735{
1736 struct circular_queue *cq = &lock_cq;
1737 struct lock_list *lock = NULL;
1738 struct lock_list *entry;
1739 struct list_head *head;
1740 unsigned int cq_depth;
1741 bool first;
1742
1743 lockdep_assert_locked();
1744
1745 __cq_init(cq);
1746 __cq_enqueue(cq, source_entry);
1747
1748 while ((lock = __bfs_next(lock, offset)) || (lock = __cq_dequeue(cq))) {
1749 if (!lock->class)
1750 return BFS_EINVALIDNODE;
1751
1752 /*
1753 * Step 1: check whether we already finish on this one.
1754 *
1755 * If we have visited all the dependencies from this @lock to
1756 * others (iow, if we have visited all lock_list entries in
1757 * @lock->class->locks_{after,before}) we skip, otherwise go
1758 * and visit all the dependencies in the list and mark this
1759 * list accessed.
1760 */
1761 if (lock_accessed(lock))
1762 continue;
1763 else
1764 mark_lock_accessed(lock);
1765
1766 /*
1767 * Step 2: check whether prev dependency and this form a strong
1768 * dependency path.
1769 */
1770 if (lock->parent) { /* Parent exists, check prev dependency */
1771 u8 dep = lock->dep;
1772 bool prev_only_xr = lock->parent->only_xr;
1773
1774 /*
1775 * Mask out all -(S*)-> if we only have *R in previous
1776 * step, because -(*R)-> -(S*)-> don't make up a strong
1777 * dependency.
1778 */
1779 if (prev_only_xr)
1780 dep &= ~(DEP_SR_MASK | DEP_SN_MASK);
1781
1782 /* If nothing left, we skip */
1783 if (!dep)
1784 continue;
1785
1786 /* If there are only -(*R)-> left, set that for the next step */
1787 lock->only_xr = !(dep & (DEP_SN_MASK | DEP_EN_MASK));
1788 }
1789
1790 /*
1791 * Step 3: we haven't visited this and there is a strong
1792 * dependency path to this, so check with @match.
1793 * If @skip is provide and returns true, we skip this
1794 * lock (and any path this lock is in).
1795 */
1796 if (skip && skip(lock, data))
1797 continue;
1798
1799 if (match(lock, data)) {
1800 *target_entry = lock;
1801 return BFS_RMATCH;
1802 }
1803
1804 /*
1805 * Step 4: if not match, expand the path by adding the
1806 * forward or backwards dependencies in the search
1807 *
1808 */
1809 first = true;
1810 head = get_dep_list(lock, offset);
1811 list_for_each_entry_rcu(entry, head, entry) {
1812 visit_lock_entry(entry, lock);
1813
1814 /*
1815 * Note we only enqueue the first of the list into the
1816 * queue, because we can always find a sibling
1817 * dependency from one (see __bfs_next()), as a result
1818 * the space of queue is saved.
1819 */
1820 if (!first)
1821 continue;
1822
1823 first = false;
1824
1825 if (__cq_enqueue(cq, entry))
1826 return BFS_EQUEUEFULL;
1827
1828 cq_depth = __cq_get_elem_count(cq);
1829 if (max_bfs_queue_depth < cq_depth)
1830 max_bfs_queue_depth = cq_depth;
1831 }
1832 }
1833
1834 return BFS_RNOMATCH;
1835}
1836
1837static inline enum bfs_result
1838__bfs_forwards(struct lock_list *src_entry,
1839 void *data,
1840 bool (*match)(struct lock_list *entry, void *data),
1841 bool (*skip)(struct lock_list *entry, void *data),
1842 struct lock_list **target_entry)
1843{
1844 return __bfs(src_entry, data, match, skip, target_entry,
1845 offsetof(struct lock_class, locks_after));
1846
1847}
1848
1849static inline enum bfs_result
1850__bfs_backwards(struct lock_list *src_entry,
1851 void *data,
1852 bool (*match)(struct lock_list *entry, void *data),
1853 bool (*skip)(struct lock_list *entry, void *data),
1854 struct lock_list **target_entry)
1855{
1856 return __bfs(src_entry, data, match, skip, target_entry,
1857 offsetof(struct lock_class, locks_before));
1858
1859}
1860
1861static void print_lock_trace(const struct lock_trace *trace,
1862 unsigned int spaces)
1863{
1864 stack_trace_print(trace->entries, trace->nr_entries, spaces);
1865}
1866
1867/*
1868 * Print a dependency chain entry (this is only done when a deadlock
1869 * has been detected):
1870 */
1871static noinline void
1872print_circular_bug_entry(struct lock_list *target, int depth)
1873{
1874 if (debug_locks_silent)
1875 return;
1876 printk("\n-> #%u", depth);
1877 print_lock_name(NULL, target->class);
1878 printk(KERN_CONT ":\n");
1879 print_lock_trace(target->trace, 6);
1880}
1881
1882static void
1883print_circular_lock_scenario(struct held_lock *src,
1884 struct held_lock *tgt,
1885 struct lock_list *prt)
1886{
1887 struct lock_class *source = hlock_class(src);
1888 struct lock_class *target = hlock_class(tgt);
1889 struct lock_class *parent = prt->class;
1890 int src_read = src->read;
1891 int tgt_read = tgt->read;
1892
1893 /*
1894 * A direct locking problem where unsafe_class lock is taken
1895 * directly by safe_class lock, then all we need to show
1896 * is the deadlock scenario, as it is obvious that the
1897 * unsafe lock is taken under the safe lock.
1898 *
1899 * But if there is a chain instead, where the safe lock takes
1900 * an intermediate lock (middle_class) where this lock is
1901 * not the same as the safe lock, then the lock chain is
1902 * used to describe the problem. Otherwise we would need
1903 * to show a different CPU case for each link in the chain
1904 * from the safe_class lock to the unsafe_class lock.
1905 */
1906 if (parent != source) {
1907 printk("Chain exists of:\n ");
1908 __print_lock_name(src, source);
1909 printk(KERN_CONT " --> ");
1910 __print_lock_name(NULL, parent);
1911 printk(KERN_CONT " --> ");
1912 __print_lock_name(tgt, target);
1913 printk(KERN_CONT "\n\n");
1914 }
1915
1916 printk(" Possible unsafe locking scenario:\n\n");
1917 printk(" CPU0 CPU1\n");
1918 printk(" ---- ----\n");
1919 if (tgt_read != 0)
1920 printk(" rlock(");
1921 else
1922 printk(" lock(");
1923 __print_lock_name(tgt, target);
1924 printk(KERN_CONT ");\n");
1925 printk(" lock(");
1926 __print_lock_name(NULL, parent);
1927 printk(KERN_CONT ");\n");
1928 printk(" lock(");
1929 __print_lock_name(tgt, target);
1930 printk(KERN_CONT ");\n");
1931 if (src_read != 0)
1932 printk(" rlock(");
1933 else if (src->sync)
1934 printk(" sync(");
1935 else
1936 printk(" lock(");
1937 __print_lock_name(src, source);
1938 printk(KERN_CONT ");\n");
1939 printk("\n *** DEADLOCK ***\n\n");
1940}
1941
1942/*
1943 * When a circular dependency is detected, print the
1944 * header first:
1945 */
1946static noinline void
1947print_circular_bug_header(struct lock_list *entry, unsigned int depth,
1948 struct held_lock *check_src,
1949 struct held_lock *check_tgt)
1950{
1951 struct task_struct *curr = current;
1952
1953 if (debug_locks_silent)
1954 return;
1955
1956 pr_warn("\n");
1957 pr_warn("======================================================\n");
1958 pr_warn("WARNING: possible circular locking dependency detected\n");
1959 print_kernel_ident();
1960 pr_warn("------------------------------------------------------\n");
1961 pr_warn("%s/%d is trying to acquire lock:\n",
1962 curr->comm, task_pid_nr(curr));
1963 print_lock(check_src);
1964
1965 pr_warn("\nbut task is already holding lock:\n");
1966
1967 print_lock(check_tgt);
1968 pr_warn("\nwhich lock already depends on the new lock.\n\n");
1969 pr_warn("\nthe existing dependency chain (in reverse order) is:\n");
1970
1971 print_circular_bug_entry(entry, depth);
1972}
1973
1974/*
1975 * We are about to add A -> B into the dependency graph, and in __bfs() a
1976 * strong dependency path A -> .. -> B is found: hlock_class equals
1977 * entry->class.
1978 *
1979 * If A -> .. -> B can replace A -> B in any __bfs() search (means the former
1980 * is _stronger_ than or equal to the latter), we consider A -> B as redundant.
1981 * For example if A -> .. -> B is -(EN)-> (i.e. A -(E*)-> .. -(*N)-> B), and A
1982 * -> B is -(ER)-> or -(EN)->, then we don't need to add A -> B into the
1983 * dependency graph, as any strong path ..-> A -> B ->.. we can get with
1984 * having dependency A -> B, we could already get a equivalent path ..-> A ->
1985 * .. -> B -> .. with A -> .. -> B. Therefore A -> B is redundant.
1986 *
1987 * We need to make sure both the start and the end of A -> .. -> B is not
1988 * weaker than A -> B. For the start part, please see the comment in
1989 * check_redundant(). For the end part, we need:
1990 *
1991 * Either
1992 *
1993 * a) A -> B is -(*R)-> (everything is not weaker than that)
1994 *
1995 * or
1996 *
1997 * b) A -> .. -> B is -(*N)-> (nothing is stronger than this)
1998 *
1999 */
2000static inline bool hlock_equal(struct lock_list *entry, void *data)
2001{
2002 struct held_lock *hlock = (struct held_lock *)data;
2003
2004 return hlock_class(hlock) == entry->class && /* Found A -> .. -> B */
2005 (hlock->read == 2 || /* A -> B is -(*R)-> */
2006 !entry->only_xr); /* A -> .. -> B is -(*N)-> */
2007}
2008
2009/*
2010 * We are about to add B -> A into the dependency graph, and in __bfs() a
2011 * strong dependency path A -> .. -> B is found: hlock_class equals
2012 * entry->class.
2013 *
2014 * We will have a deadlock case (conflict) if A -> .. -> B -> A is a strong
2015 * dependency cycle, that means:
2016 *
2017 * Either
2018 *
2019 * a) B -> A is -(E*)->
2020 *
2021 * or
2022 *
2023 * b) A -> .. -> B is -(*N)-> (i.e. A -> .. -(*N)-> B)
2024 *
2025 * as then we don't have -(*R)-> -(S*)-> in the cycle.
2026 */
2027static inline bool hlock_conflict(struct lock_list *entry, void *data)
2028{
2029 struct held_lock *hlock = (struct held_lock *)data;
2030
2031 return hlock_class(hlock) == entry->class && /* Found A -> .. -> B */
2032 (hlock->read == 0 || /* B -> A is -(E*)-> */
2033 !entry->only_xr); /* A -> .. -> B is -(*N)-> */
2034}
2035
2036static noinline void print_circular_bug(struct lock_list *this,
2037 struct lock_list *target,
2038 struct held_lock *check_src,
2039 struct held_lock *check_tgt)
2040{
2041 struct task_struct *curr = current;
2042 struct lock_list *parent;
2043 struct lock_list *first_parent;
2044 int depth;
2045
2046 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
2047 return;
2048
2049 this->trace = save_trace();
2050 if (!this->trace)
2051 return;
2052
2053 depth = get_lock_depth(target);
2054
2055 nbcon_cpu_emergency_enter();
2056
2057 print_circular_bug_header(target, depth, check_src, check_tgt);
2058
2059 parent = get_lock_parent(target);
2060 first_parent = parent;
2061
2062 while (parent) {
2063 print_circular_bug_entry(parent, --depth);
2064 parent = get_lock_parent(parent);
2065 }
2066
2067 printk("\nother info that might help us debug this:\n\n");
2068 print_circular_lock_scenario(check_src, check_tgt,
2069 first_parent);
2070
2071 lockdep_print_held_locks(curr);
2072
2073 printk("\nstack backtrace:\n");
2074 dump_stack();
2075
2076 nbcon_cpu_emergency_exit();
2077}
2078
2079static noinline void print_bfs_bug(int ret)
2080{
2081 if (!debug_locks_off_graph_unlock())
2082 return;
2083
2084 /*
2085 * Breadth-first-search failed, graph got corrupted?
2086 */
2087 if (ret == BFS_EQUEUEFULL)
2088 pr_warn("Increase LOCKDEP_CIRCULAR_QUEUE_BITS to avoid this warning:\n");
2089
2090 WARN(1, "lockdep bfs error:%d\n", ret);
2091}
2092
2093static bool noop_count(struct lock_list *entry, void *data)
2094{
2095 (*(unsigned long *)data)++;
2096 return false;
2097}
2098
2099static unsigned long __lockdep_count_forward_deps(struct lock_list *this)
2100{
2101 unsigned long count = 0;
2102 struct lock_list *target_entry;
2103
2104 __bfs_forwards(this, (void *)&count, noop_count, NULL, &target_entry);
2105
2106 return count;
2107}
2108unsigned long lockdep_count_forward_deps(struct lock_class *class)
2109{
2110 unsigned long ret, flags;
2111 struct lock_list this;
2112
2113 __bfs_init_root(&this, class);
2114
2115 raw_local_irq_save(flags);
2116 lockdep_lock();
2117 ret = __lockdep_count_forward_deps(&this);
2118 lockdep_unlock();
2119 raw_local_irq_restore(flags);
2120
2121 return ret;
2122}
2123
2124static unsigned long __lockdep_count_backward_deps(struct lock_list *this)
2125{
2126 unsigned long count = 0;
2127 struct lock_list *target_entry;
2128
2129 __bfs_backwards(this, (void *)&count, noop_count, NULL, &target_entry);
2130
2131 return count;
2132}
2133
2134unsigned long lockdep_count_backward_deps(struct lock_class *class)
2135{
2136 unsigned long ret, flags;
2137 struct lock_list this;
2138
2139 __bfs_init_root(&this, class);
2140
2141 raw_local_irq_save(flags);
2142 lockdep_lock();
2143 ret = __lockdep_count_backward_deps(&this);
2144 lockdep_unlock();
2145 raw_local_irq_restore(flags);
2146
2147 return ret;
2148}
2149
2150/*
2151 * Check that the dependency graph starting at <src> can lead to
2152 * <target> or not.
2153 */
2154static noinline enum bfs_result
2155check_path(struct held_lock *target, struct lock_list *src_entry,
2156 bool (*match)(struct lock_list *entry, void *data),
2157 bool (*skip)(struct lock_list *entry, void *data),
2158 struct lock_list **target_entry)
2159{
2160 enum bfs_result ret;
2161
2162 ret = __bfs_forwards(src_entry, target, match, skip, target_entry);
2163
2164 if (unlikely(bfs_error(ret)))
2165 print_bfs_bug(ret);
2166
2167 return ret;
2168}
2169
2170static void print_deadlock_bug(struct task_struct *, struct held_lock *, struct held_lock *);
2171
2172/*
2173 * Prove that the dependency graph starting at <src> can not
2174 * lead to <target>. If it can, there is a circle when adding
2175 * <target> -> <src> dependency.
2176 *
2177 * Print an error and return BFS_RMATCH if it does.
2178 */
2179static noinline enum bfs_result
2180check_noncircular(struct held_lock *src, struct held_lock *target,
2181 struct lock_trace **const trace)
2182{
2183 enum bfs_result ret;
2184 struct lock_list *target_entry;
2185 struct lock_list src_entry;
2186
2187 bfs_init_root(&src_entry, src);
2188
2189 debug_atomic_inc(nr_cyclic_checks);
2190
2191 ret = check_path(target, &src_entry, hlock_conflict, NULL, &target_entry);
2192
2193 if (unlikely(ret == BFS_RMATCH)) {
2194 if (!*trace) {
2195 /*
2196 * If save_trace fails here, the printing might
2197 * trigger a WARN but because of the !nr_entries it
2198 * should not do bad things.
2199 */
2200 *trace = save_trace();
2201 }
2202
2203 if (src->class_idx == target->class_idx)
2204 print_deadlock_bug(current, src, target);
2205 else
2206 print_circular_bug(&src_entry, target_entry, src, target);
2207 }
2208
2209 return ret;
2210}
2211
2212#ifdef CONFIG_TRACE_IRQFLAGS
2213
2214/*
2215 * Forwards and backwards subgraph searching, for the purposes of
2216 * proving that two subgraphs can be connected by a new dependency
2217 * without creating any illegal irq-safe -> irq-unsafe lock dependency.
2218 *
2219 * A irq safe->unsafe deadlock happens with the following conditions:
2220 *
2221 * 1) We have a strong dependency path A -> ... -> B
2222 *
2223 * 2) and we have ENABLED_IRQ usage of B and USED_IN_IRQ usage of A, therefore
2224 * irq can create a new dependency B -> A (consider the case that a holder
2225 * of B gets interrupted by an irq whose handler will try to acquire A).
2226 *
2227 * 3) the dependency circle A -> ... -> B -> A we get from 1) and 2) is a
2228 * strong circle:
2229 *
2230 * For the usage bits of B:
2231 * a) if A -> B is -(*N)->, then B -> A could be any type, so any
2232 * ENABLED_IRQ usage suffices.
2233 * b) if A -> B is -(*R)->, then B -> A must be -(E*)->, so only
2234 * ENABLED_IRQ_*_READ usage suffices.
2235 *
2236 * For the usage bits of A:
2237 * c) if A -> B is -(E*)->, then B -> A could be any type, so any
2238 * USED_IN_IRQ usage suffices.
2239 * d) if A -> B is -(S*)->, then B -> A must be -(*N)->, so only
2240 * USED_IN_IRQ_*_READ usage suffices.
2241 */
2242
2243/*
2244 * There is a strong dependency path in the dependency graph: A -> B, and now
2245 * we need to decide which usage bit of A should be accumulated to detect
2246 * safe->unsafe bugs.
2247 *
2248 * Note that usage_accumulate() is used in backwards search, so ->only_xr
2249 * stands for whether A -> B only has -(S*)-> (in this case ->only_xr is true).
2250 *
2251 * As above, if only_xr is false, which means A -> B has -(E*)-> dependency
2252 * path, any usage of A should be considered. Otherwise, we should only
2253 * consider _READ usage.
2254 */
2255static inline bool usage_accumulate(struct lock_list *entry, void *mask)
2256{
2257 if (!entry->only_xr)
2258 *(unsigned long *)mask |= entry->class->usage_mask;
2259 else /* Mask out _READ usage bits */
2260 *(unsigned long *)mask |= (entry->class->usage_mask & LOCKF_IRQ);
2261
2262 return false;
2263}
2264
2265/*
2266 * There is a strong dependency path in the dependency graph: A -> B, and now
2267 * we need to decide which usage bit of B conflicts with the usage bits of A,
2268 * i.e. which usage bit of B may introduce safe->unsafe deadlocks.
2269 *
2270 * As above, if only_xr is false, which means A -> B has -(*N)-> dependency
2271 * path, any usage of B should be considered. Otherwise, we should only
2272 * consider _READ usage.
2273 */
2274static inline bool usage_match(struct lock_list *entry, void *mask)
2275{
2276 if (!entry->only_xr)
2277 return !!(entry->class->usage_mask & *(unsigned long *)mask);
2278 else /* Mask out _READ usage bits */
2279 return !!((entry->class->usage_mask & LOCKF_IRQ) & *(unsigned long *)mask);
2280}
2281
2282static inline bool usage_skip(struct lock_list *entry, void *mask)
2283{
2284 if (entry->class->lock_type == LD_LOCK_NORMAL)
2285 return false;
2286
2287 /*
2288 * Skip local_lock() for irq inversion detection.
2289 *
2290 * For !RT, local_lock() is not a real lock, so it won't carry any
2291 * dependency.
2292 *
2293 * For RT, an irq inversion happens when we have lock A and B, and on
2294 * some CPU we can have:
2295 *
2296 * lock(A);
2297 * <interrupted>
2298 * lock(B);
2299 *
2300 * where lock(B) cannot sleep, and we have a dependency B -> ... -> A.
2301 *
2302 * Now we prove local_lock() cannot exist in that dependency. First we
2303 * have the observation for any lock chain L1 -> ... -> Ln, for any
2304 * 1 <= i <= n, Li.inner_wait_type <= L1.inner_wait_type, otherwise
2305 * wait context check will complain. And since B is not a sleep lock,
2306 * therefore B.inner_wait_type >= 2, and since the inner_wait_type of
2307 * local_lock() is 3, which is greater than 2, therefore there is no
2308 * way the local_lock() exists in the dependency B -> ... -> A.
2309 *
2310 * As a result, we will skip local_lock(), when we search for irq
2311 * inversion bugs.
2312 */
2313 if (entry->class->lock_type == LD_LOCK_PERCPU &&
2314 DEBUG_LOCKS_WARN_ON(entry->class->wait_type_inner < LD_WAIT_CONFIG))
2315 return false;
2316
2317 /*
2318 * Skip WAIT_OVERRIDE for irq inversion detection -- it's not actually
2319 * a lock and only used to override the wait_type.
2320 */
2321
2322 return true;
2323}
2324
2325/*
2326 * Find a node in the forwards-direction dependency sub-graph starting
2327 * at @root->class that matches @bit.
2328 *
2329 * Return BFS_MATCH if such a node exists in the subgraph, and put that node
2330 * into *@target_entry.
2331 */
2332static enum bfs_result
2333find_usage_forwards(struct lock_list *root, unsigned long usage_mask,
2334 struct lock_list **target_entry)
2335{
2336 enum bfs_result result;
2337
2338 debug_atomic_inc(nr_find_usage_forwards_checks);
2339
2340 result = __bfs_forwards(root, &usage_mask, usage_match, usage_skip, target_entry);
2341
2342 return result;
2343}
2344
2345/*
2346 * Find a node in the backwards-direction dependency sub-graph starting
2347 * at @root->class that matches @bit.
2348 */
2349static enum bfs_result
2350find_usage_backwards(struct lock_list *root, unsigned long usage_mask,
2351 struct lock_list **target_entry)
2352{
2353 enum bfs_result result;
2354
2355 debug_atomic_inc(nr_find_usage_backwards_checks);
2356
2357 result = __bfs_backwards(root, &usage_mask, usage_match, usage_skip, target_entry);
2358
2359 return result;
2360}
2361
2362static void print_lock_class_header(struct lock_class *class, int depth)
2363{
2364 int bit;
2365
2366 printk("%*s->", depth, "");
2367 print_lock_name(NULL, class);
2368#ifdef CONFIG_DEBUG_LOCKDEP
2369 printk(KERN_CONT " ops: %lu", debug_class_ops_read(class));
2370#endif
2371 printk(KERN_CONT " {\n");
2372
2373 for (bit = 0; bit < LOCK_TRACE_STATES; bit++) {
2374 if (class->usage_mask & (1 << bit)) {
2375 int len = depth;
2376
2377 len += printk("%*s %s", depth, "", usage_str[bit]);
2378 len += printk(KERN_CONT " at:\n");
2379 print_lock_trace(class->usage_traces[bit], len);
2380 }
2381 }
2382 printk("%*s }\n", depth, "");
2383
2384 printk("%*s ... key at: [<%px>] %pS\n",
2385 depth, "", class->key, class->key);
2386}
2387
2388/*
2389 * Dependency path printing:
2390 *
2391 * After BFS we get a lock dependency path (linked via ->parent of lock_list),
2392 * printing out each lock in the dependency path will help on understanding how
2393 * the deadlock could happen. Here are some details about dependency path
2394 * printing:
2395 *
2396 * 1) A lock_list can be either forwards or backwards for a lock dependency,
2397 * for a lock dependency A -> B, there are two lock_lists:
2398 *
2399 * a) lock_list in the ->locks_after list of A, whose ->class is B and
2400 * ->links_to is A. In this case, we can say the lock_list is
2401 * "A -> B" (forwards case).
2402 *
2403 * b) lock_list in the ->locks_before list of B, whose ->class is A
2404 * and ->links_to is B. In this case, we can say the lock_list is
2405 * "B <- A" (bacwards case).
2406 *
2407 * The ->trace of both a) and b) point to the call trace where B was
2408 * acquired with A held.
2409 *
2410 * 2) A "helper" lock_list is introduced during BFS, this lock_list doesn't
2411 * represent a certain lock dependency, it only provides an initial entry
2412 * for BFS. For example, BFS may introduce a "helper" lock_list whose
2413 * ->class is A, as a result BFS will search all dependencies starting with
2414 * A, e.g. A -> B or A -> C.
2415 *
2416 * The notation of a forwards helper lock_list is like "-> A", which means
2417 * we should search the forwards dependencies starting with "A", e.g A -> B
2418 * or A -> C.
2419 *
2420 * The notation of a bacwards helper lock_list is like "<- B", which means
2421 * we should search the backwards dependencies ending with "B", e.g.
2422 * B <- A or B <- C.
2423 */
2424
2425/*
2426 * printk the shortest lock dependencies from @root to @leaf in reverse order.
2427 *
2428 * We have a lock dependency path as follow:
2429 *
2430 * @root @leaf
2431 * | |
2432 * V V
2433 * ->parent ->parent
2434 * | lock_list | <--------- | lock_list | ... | lock_list | <--------- | lock_list |
2435 * | -> L1 | | L1 -> L2 | ... |Ln-2 -> Ln-1| | Ln-1 -> Ln|
2436 *
2437 * , so it's natural that we start from @leaf and print every ->class and
2438 * ->trace until we reach the @root.
2439 */
2440static void __used
2441print_shortest_lock_dependencies(struct lock_list *leaf,
2442 struct lock_list *root)
2443{
2444 struct lock_list *entry = leaf;
2445 int depth;
2446
2447 /*compute depth from generated tree by BFS*/
2448 depth = get_lock_depth(leaf);
2449
2450 do {
2451 print_lock_class_header(entry->class, depth);
2452 printk("%*s ... acquired at:\n", depth, "");
2453 print_lock_trace(entry->trace, 2);
2454 printk("\n");
2455
2456 if (depth == 0 && (entry != root)) {
2457 printk("lockdep:%s bad path found in chain graph\n", __func__);
2458 break;
2459 }
2460
2461 entry = get_lock_parent(entry);
2462 depth--;
2463 } while (entry && (depth >= 0));
2464}
2465
2466/*
2467 * printk the shortest lock dependencies from @leaf to @root.
2468 *
2469 * We have a lock dependency path (from a backwards search) as follow:
2470 *
2471 * @leaf @root
2472 * | |
2473 * V V
2474 * ->parent ->parent
2475 * | lock_list | ---------> | lock_list | ... | lock_list | ---------> | lock_list |
2476 * | L2 <- L1 | | L3 <- L2 | ... | Ln <- Ln-1 | | <- Ln |
2477 *
2478 * , so when we iterate from @leaf to @root, we actually print the lock
2479 * dependency path L1 -> L2 -> .. -> Ln in the non-reverse order.
2480 *
2481 * Another thing to notice here is that ->class of L2 <- L1 is L1, while the
2482 * ->trace of L2 <- L1 is the call trace of L2, in fact we don't have the call
2483 * trace of L1 in the dependency path, which is alright, because most of the
2484 * time we can figure out where L1 is held from the call trace of L2.
2485 */
2486static void __used
2487print_shortest_lock_dependencies_backwards(struct lock_list *leaf,
2488 struct lock_list *root)
2489{
2490 struct lock_list *entry = leaf;
2491 const struct lock_trace *trace = NULL;
2492 int depth;
2493
2494 /*compute depth from generated tree by BFS*/
2495 depth = get_lock_depth(leaf);
2496
2497 do {
2498 print_lock_class_header(entry->class, depth);
2499 if (trace) {
2500 printk("%*s ... acquired at:\n", depth, "");
2501 print_lock_trace(trace, 2);
2502 printk("\n");
2503 }
2504
2505 /*
2506 * Record the pointer to the trace for the next lock_list
2507 * entry, see the comments for the function.
2508 */
2509 trace = entry->trace;
2510
2511 if (depth == 0 && (entry != root)) {
2512 printk("lockdep:%s bad path found in chain graph\n", __func__);
2513 break;
2514 }
2515
2516 entry = get_lock_parent(entry);
2517 depth--;
2518 } while (entry && (depth >= 0));
2519}
2520
2521static void
2522print_irq_lock_scenario(struct lock_list *safe_entry,
2523 struct lock_list *unsafe_entry,
2524 struct lock_class *prev_class,
2525 struct lock_class *next_class)
2526{
2527 struct lock_class *safe_class = safe_entry->class;
2528 struct lock_class *unsafe_class = unsafe_entry->class;
2529 struct lock_class *middle_class = prev_class;
2530
2531 if (middle_class == safe_class)
2532 middle_class = next_class;
2533
2534 /*
2535 * A direct locking problem where unsafe_class lock is taken
2536 * directly by safe_class lock, then all we need to show
2537 * is the deadlock scenario, as it is obvious that the
2538 * unsafe lock is taken under the safe lock.
2539 *
2540 * But if there is a chain instead, where the safe lock takes
2541 * an intermediate lock (middle_class) where this lock is
2542 * not the same as the safe lock, then the lock chain is
2543 * used to describe the problem. Otherwise we would need
2544 * to show a different CPU case for each link in the chain
2545 * from the safe_class lock to the unsafe_class lock.
2546 */
2547 if (middle_class != unsafe_class) {
2548 printk("Chain exists of:\n ");
2549 __print_lock_name(NULL, safe_class);
2550 printk(KERN_CONT " --> ");
2551 __print_lock_name(NULL, middle_class);
2552 printk(KERN_CONT " --> ");
2553 __print_lock_name(NULL, unsafe_class);
2554 printk(KERN_CONT "\n\n");
2555 }
2556
2557 printk(" Possible interrupt unsafe locking scenario:\n\n");
2558 printk(" CPU0 CPU1\n");
2559 printk(" ---- ----\n");
2560 printk(" lock(");
2561 __print_lock_name(NULL, unsafe_class);
2562 printk(KERN_CONT ");\n");
2563 printk(" local_irq_disable();\n");
2564 printk(" lock(");
2565 __print_lock_name(NULL, safe_class);
2566 printk(KERN_CONT ");\n");
2567 printk(" lock(");
2568 __print_lock_name(NULL, middle_class);
2569 printk(KERN_CONT ");\n");
2570 printk(" <Interrupt>\n");
2571 printk(" lock(");
2572 __print_lock_name(NULL, safe_class);
2573 printk(KERN_CONT ");\n");
2574 printk("\n *** DEADLOCK ***\n\n");
2575}
2576
2577static void
2578print_bad_irq_dependency(struct task_struct *curr,
2579 struct lock_list *prev_root,
2580 struct lock_list *next_root,
2581 struct lock_list *backwards_entry,
2582 struct lock_list *forwards_entry,
2583 struct held_lock *prev,
2584 struct held_lock *next,
2585 enum lock_usage_bit bit1,
2586 enum lock_usage_bit bit2,
2587 const char *irqclass)
2588{
2589 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
2590 return;
2591
2592 nbcon_cpu_emergency_enter();
2593
2594 pr_warn("\n");
2595 pr_warn("=====================================================\n");
2596 pr_warn("WARNING: %s-safe -> %s-unsafe lock order detected\n",
2597 irqclass, irqclass);
2598 print_kernel_ident();
2599 pr_warn("-----------------------------------------------------\n");
2600 pr_warn("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] is trying to acquire:\n",
2601 curr->comm, task_pid_nr(curr),
2602 lockdep_hardirq_context(), hardirq_count() >> HARDIRQ_SHIFT,
2603 curr->softirq_context, softirq_count() >> SOFTIRQ_SHIFT,
2604 lockdep_hardirqs_enabled(),
2605 curr->softirqs_enabled);
2606 print_lock(next);
2607
2608 pr_warn("\nand this task is already holding:\n");
2609 print_lock(prev);
2610 pr_warn("which would create a new lock dependency:\n");
2611 print_lock_name(prev, hlock_class(prev));
2612 pr_cont(" ->");
2613 print_lock_name(next, hlock_class(next));
2614 pr_cont("\n");
2615
2616 pr_warn("\nbut this new dependency connects a %s-irq-safe lock:\n",
2617 irqclass);
2618 print_lock_name(NULL, backwards_entry->class);
2619 pr_warn("\n... which became %s-irq-safe at:\n", irqclass);
2620
2621 print_lock_trace(backwards_entry->class->usage_traces[bit1], 1);
2622
2623 pr_warn("\nto a %s-irq-unsafe lock:\n", irqclass);
2624 print_lock_name(NULL, forwards_entry->class);
2625 pr_warn("\n... which became %s-irq-unsafe at:\n", irqclass);
2626 pr_warn("...");
2627
2628 print_lock_trace(forwards_entry->class->usage_traces[bit2], 1);
2629
2630 pr_warn("\nother info that might help us debug this:\n\n");
2631 print_irq_lock_scenario(backwards_entry, forwards_entry,
2632 hlock_class(prev), hlock_class(next));
2633
2634 lockdep_print_held_locks(curr);
2635
2636 pr_warn("\nthe dependencies between %s-irq-safe lock and the holding lock:\n", irqclass);
2637 print_shortest_lock_dependencies_backwards(backwards_entry, prev_root);
2638
2639 pr_warn("\nthe dependencies between the lock to be acquired");
2640 pr_warn(" and %s-irq-unsafe lock:\n", irqclass);
2641 next_root->trace = save_trace();
2642 if (!next_root->trace)
2643 goto out;
2644 print_shortest_lock_dependencies(forwards_entry, next_root);
2645
2646 pr_warn("\nstack backtrace:\n");
2647 dump_stack();
2648out:
2649 nbcon_cpu_emergency_exit();
2650}
2651
2652static const char *state_names[] = {
2653#define LOCKDEP_STATE(__STATE) \
2654 __stringify(__STATE),
2655#include "lockdep_states.h"
2656#undef LOCKDEP_STATE
2657};
2658
2659static const char *state_rnames[] = {
2660#define LOCKDEP_STATE(__STATE) \
2661 __stringify(__STATE)"-READ",
2662#include "lockdep_states.h"
2663#undef LOCKDEP_STATE
2664};
2665
2666static inline const char *state_name(enum lock_usage_bit bit)
2667{
2668 if (bit & LOCK_USAGE_READ_MASK)
2669 return state_rnames[bit >> LOCK_USAGE_DIR_MASK];
2670 else
2671 return state_names[bit >> LOCK_USAGE_DIR_MASK];
2672}
2673
2674/*
2675 * The bit number is encoded like:
2676 *
2677 * bit0: 0 exclusive, 1 read lock
2678 * bit1: 0 used in irq, 1 irq enabled
2679 * bit2-n: state
2680 */
2681static int exclusive_bit(int new_bit)
2682{
2683 int state = new_bit & LOCK_USAGE_STATE_MASK;
2684 int dir = new_bit & LOCK_USAGE_DIR_MASK;
2685
2686 /*
2687 * keep state, bit flip the direction and strip read.
2688 */
2689 return state | (dir ^ LOCK_USAGE_DIR_MASK);
2690}
2691
2692/*
2693 * Observe that when given a bitmask where each bitnr is encoded as above, a
2694 * right shift of the mask transforms the individual bitnrs as -1 and
2695 * conversely, a left shift transforms into +1 for the individual bitnrs.
2696 *
2697 * So for all bits whose number have LOCK_ENABLED_* set (bitnr1 == 1), we can
2698 * create the mask with those bit numbers using LOCK_USED_IN_* (bitnr1 == 0)
2699 * instead by subtracting the bit number by 2, or shifting the mask right by 2.
2700 *
2701 * Similarly, bitnr1 == 0 becomes bitnr1 == 1 by adding 2, or shifting left 2.
2702 *
2703 * So split the mask (note that LOCKF_ENABLED_IRQ_ALL|LOCKF_USED_IN_IRQ_ALL is
2704 * all bits set) and recompose with bitnr1 flipped.
2705 */
2706static unsigned long invert_dir_mask(unsigned long mask)
2707{
2708 unsigned long excl = 0;
2709
2710 /* Invert dir */
2711 excl |= (mask & LOCKF_ENABLED_IRQ_ALL) >> LOCK_USAGE_DIR_MASK;
2712 excl |= (mask & LOCKF_USED_IN_IRQ_ALL) << LOCK_USAGE_DIR_MASK;
2713
2714 return excl;
2715}
2716
2717/*
2718 * Note that a LOCK_ENABLED_IRQ_*_READ usage and a LOCK_USED_IN_IRQ_*_READ
2719 * usage may cause deadlock too, for example:
2720 *
2721 * P1 P2
2722 * <irq disabled>
2723 * write_lock(l1); <irq enabled>
2724 * read_lock(l2);
2725 * write_lock(l2);
2726 * <in irq>
2727 * read_lock(l1);
2728 *
2729 * , in above case, l1 will be marked as LOCK_USED_IN_IRQ_HARDIRQ_READ and l2
2730 * will marked as LOCK_ENABLE_IRQ_HARDIRQ_READ, and this is a possible
2731 * deadlock.
2732 *
2733 * In fact, all of the following cases may cause deadlocks:
2734 *
2735 * LOCK_USED_IN_IRQ_* -> LOCK_ENABLED_IRQ_*
2736 * LOCK_USED_IN_IRQ_*_READ -> LOCK_ENABLED_IRQ_*
2737 * LOCK_USED_IN_IRQ_* -> LOCK_ENABLED_IRQ_*_READ
2738 * LOCK_USED_IN_IRQ_*_READ -> LOCK_ENABLED_IRQ_*_READ
2739 *
2740 * As a result, to calculate the "exclusive mask", first we invert the
2741 * direction (USED_IN/ENABLED) of the original mask, and 1) for all bits with
2742 * bitnr0 set (LOCK_*_READ), add those with bitnr0 cleared (LOCK_*). 2) for all
2743 * bits with bitnr0 cleared (LOCK_*_READ), add those with bitnr0 set (LOCK_*).
2744 */
2745static unsigned long exclusive_mask(unsigned long mask)
2746{
2747 unsigned long excl = invert_dir_mask(mask);
2748
2749 excl |= (excl & LOCKF_IRQ_READ) >> LOCK_USAGE_READ_MASK;
2750 excl |= (excl & LOCKF_IRQ) << LOCK_USAGE_READ_MASK;
2751
2752 return excl;
2753}
2754
2755/*
2756 * Retrieve the _possible_ original mask to which @mask is
2757 * exclusive. Ie: this is the opposite of exclusive_mask().
2758 * Note that 2 possible original bits can match an exclusive
2759 * bit: one has LOCK_USAGE_READ_MASK set, the other has it
2760 * cleared. So both are returned for each exclusive bit.
2761 */
2762static unsigned long original_mask(unsigned long mask)
2763{
2764 unsigned long excl = invert_dir_mask(mask);
2765
2766 /* Include read in existing usages */
2767 excl |= (excl & LOCKF_IRQ_READ) >> LOCK_USAGE_READ_MASK;
2768 excl |= (excl & LOCKF_IRQ) << LOCK_USAGE_READ_MASK;
2769
2770 return excl;
2771}
2772
2773/*
2774 * Find the first pair of bit match between an original
2775 * usage mask and an exclusive usage mask.
2776 */
2777static int find_exclusive_match(unsigned long mask,
2778 unsigned long excl_mask,
2779 enum lock_usage_bit *bitp,
2780 enum lock_usage_bit *excl_bitp)
2781{
2782 int bit, excl, excl_read;
2783
2784 for_each_set_bit(bit, &mask, LOCK_USED) {
2785 /*
2786 * exclusive_bit() strips the read bit, however,
2787 * LOCK_ENABLED_IRQ_*_READ may cause deadlocks too, so we need
2788 * to search excl | LOCK_USAGE_READ_MASK as well.
2789 */
2790 excl = exclusive_bit(bit);
2791 excl_read = excl | LOCK_USAGE_READ_MASK;
2792 if (excl_mask & lock_flag(excl)) {
2793 *bitp = bit;
2794 *excl_bitp = excl;
2795 return 0;
2796 } else if (excl_mask & lock_flag(excl_read)) {
2797 *bitp = bit;
2798 *excl_bitp = excl_read;
2799 return 0;
2800 }
2801 }
2802 return -1;
2803}
2804
2805/*
2806 * Prove that the new dependency does not connect a hardirq-safe(-read)
2807 * lock with a hardirq-unsafe lock - to achieve this we search
2808 * the backwards-subgraph starting at <prev>, and the
2809 * forwards-subgraph starting at <next>:
2810 */
2811static int check_irq_usage(struct task_struct *curr, struct held_lock *prev,
2812 struct held_lock *next)
2813{
2814 unsigned long usage_mask = 0, forward_mask, backward_mask;
2815 enum lock_usage_bit forward_bit = 0, backward_bit = 0;
2816 struct lock_list *target_entry1;
2817 struct lock_list *target_entry;
2818 struct lock_list this, that;
2819 enum bfs_result ret;
2820
2821 /*
2822 * Step 1: gather all hard/soft IRQs usages backward in an
2823 * accumulated usage mask.
2824 */
2825 bfs_init_rootb(&this, prev);
2826
2827 ret = __bfs_backwards(&this, &usage_mask, usage_accumulate, usage_skip, NULL);
2828 if (bfs_error(ret)) {
2829 print_bfs_bug(ret);
2830 return 0;
2831 }
2832
2833 usage_mask &= LOCKF_USED_IN_IRQ_ALL;
2834 if (!usage_mask)
2835 return 1;
2836
2837 /*
2838 * Step 2: find exclusive uses forward that match the previous
2839 * backward accumulated mask.
2840 */
2841 forward_mask = exclusive_mask(usage_mask);
2842
2843 bfs_init_root(&that, next);
2844
2845 ret = find_usage_forwards(&that, forward_mask, &target_entry1);
2846 if (bfs_error(ret)) {
2847 print_bfs_bug(ret);
2848 return 0;
2849 }
2850 if (ret == BFS_RNOMATCH)
2851 return 1;
2852
2853 /*
2854 * Step 3: we found a bad match! Now retrieve a lock from the backward
2855 * list whose usage mask matches the exclusive usage mask from the
2856 * lock found on the forward list.
2857 *
2858 * Note, we should only keep the LOCKF_ENABLED_IRQ_ALL bits, considering
2859 * the follow case:
2860 *
2861 * When trying to add A -> B to the graph, we find that there is a
2862 * hardirq-safe L, that L -> ... -> A, and another hardirq-unsafe M,
2863 * that B -> ... -> M. However M is **softirq-safe**, if we use exact
2864 * invert bits of M's usage_mask, we will find another lock N that is
2865 * **softirq-unsafe** and N -> ... -> A, however N -> .. -> M will not
2866 * cause a inversion deadlock.
2867 */
2868 backward_mask = original_mask(target_entry1->class->usage_mask & LOCKF_ENABLED_IRQ_ALL);
2869
2870 ret = find_usage_backwards(&this, backward_mask, &target_entry);
2871 if (bfs_error(ret)) {
2872 print_bfs_bug(ret);
2873 return 0;
2874 }
2875 if (DEBUG_LOCKS_WARN_ON(ret == BFS_RNOMATCH))
2876 return 1;
2877
2878 /*
2879 * Step 4: narrow down to a pair of incompatible usage bits
2880 * and report it.
2881 */
2882 ret = find_exclusive_match(target_entry->class->usage_mask,
2883 target_entry1->class->usage_mask,
2884 &backward_bit, &forward_bit);
2885 if (DEBUG_LOCKS_WARN_ON(ret == -1))
2886 return 1;
2887
2888 print_bad_irq_dependency(curr, &this, &that,
2889 target_entry, target_entry1,
2890 prev, next,
2891 backward_bit, forward_bit,
2892 state_name(backward_bit));
2893
2894 return 0;
2895}
2896
2897#else
2898
2899static inline int check_irq_usage(struct task_struct *curr,
2900 struct held_lock *prev, struct held_lock *next)
2901{
2902 return 1;
2903}
2904
2905static inline bool usage_skip(struct lock_list *entry, void *mask)
2906{
2907 return false;
2908}
2909
2910#endif /* CONFIG_TRACE_IRQFLAGS */
2911
2912#ifdef CONFIG_LOCKDEP_SMALL
2913/*
2914 * Check that the dependency graph starting at <src> can lead to
2915 * <target> or not. If it can, <src> -> <target> dependency is already
2916 * in the graph.
2917 *
2918 * Return BFS_RMATCH if it does, or BFS_RNOMATCH if it does not, return BFS_E* if
2919 * any error appears in the bfs search.
2920 */
2921static noinline enum bfs_result
2922check_redundant(struct held_lock *src, struct held_lock *target)
2923{
2924 enum bfs_result ret;
2925 struct lock_list *target_entry;
2926 struct lock_list src_entry;
2927
2928 bfs_init_root(&src_entry, src);
2929 /*
2930 * Special setup for check_redundant().
2931 *
2932 * To report redundant, we need to find a strong dependency path that
2933 * is equal to or stronger than <src> -> <target>. So if <src> is E,
2934 * we need to let __bfs() only search for a path starting at a -(E*)->,
2935 * we achieve this by setting the initial node's ->only_xr to true in
2936 * that case. And if <prev> is S, we set initial ->only_xr to false
2937 * because both -(S*)-> (equal) and -(E*)-> (stronger) are redundant.
2938 */
2939 src_entry.only_xr = src->read == 0;
2940
2941 debug_atomic_inc(nr_redundant_checks);
2942
2943 /*
2944 * Note: we skip local_lock() for redundant check, because as the
2945 * comment in usage_skip(), A -> local_lock() -> B and A -> B are not
2946 * the same.
2947 */
2948 ret = check_path(target, &src_entry, hlock_equal, usage_skip, &target_entry);
2949
2950 if (ret == BFS_RMATCH)
2951 debug_atomic_inc(nr_redundant);
2952
2953 return ret;
2954}
2955
2956#else
2957
2958static inline enum bfs_result
2959check_redundant(struct held_lock *src, struct held_lock *target)
2960{
2961 return BFS_RNOMATCH;
2962}
2963
2964#endif
2965
2966static void inc_chains(int irq_context)
2967{
2968 if (irq_context & LOCK_CHAIN_HARDIRQ_CONTEXT)
2969 nr_hardirq_chains++;
2970 else if (irq_context & LOCK_CHAIN_SOFTIRQ_CONTEXT)
2971 nr_softirq_chains++;
2972 else
2973 nr_process_chains++;
2974}
2975
2976static void dec_chains(int irq_context)
2977{
2978 if (irq_context & LOCK_CHAIN_HARDIRQ_CONTEXT)
2979 nr_hardirq_chains--;
2980 else if (irq_context & LOCK_CHAIN_SOFTIRQ_CONTEXT)
2981 nr_softirq_chains--;
2982 else
2983 nr_process_chains--;
2984}
2985
2986static void
2987print_deadlock_scenario(struct held_lock *nxt, struct held_lock *prv)
2988{
2989 struct lock_class *next = hlock_class(nxt);
2990 struct lock_class *prev = hlock_class(prv);
2991
2992 printk(" Possible unsafe locking scenario:\n\n");
2993 printk(" CPU0\n");
2994 printk(" ----\n");
2995 printk(" lock(");
2996 __print_lock_name(prv, prev);
2997 printk(KERN_CONT ");\n");
2998 printk(" lock(");
2999 __print_lock_name(nxt, next);
3000 printk(KERN_CONT ");\n");
3001 printk("\n *** DEADLOCK ***\n\n");
3002 printk(" May be due to missing lock nesting notation\n\n");
3003}
3004
3005static void
3006print_deadlock_bug(struct task_struct *curr, struct held_lock *prev,
3007 struct held_lock *next)
3008{
3009 struct lock_class *class = hlock_class(prev);
3010
3011 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
3012 return;
3013
3014 nbcon_cpu_emergency_enter();
3015
3016 pr_warn("\n");
3017 pr_warn("============================================\n");
3018 pr_warn("WARNING: possible recursive locking detected\n");
3019 print_kernel_ident();
3020 pr_warn("--------------------------------------------\n");
3021 pr_warn("%s/%d is trying to acquire lock:\n",
3022 curr->comm, task_pid_nr(curr));
3023 print_lock(next);
3024 pr_warn("\nbut task is already holding lock:\n");
3025 print_lock(prev);
3026
3027 if (class->cmp_fn) {
3028 pr_warn("and the lock comparison function returns %i:\n",
3029 class->cmp_fn(prev->instance, next->instance));
3030 }
3031
3032 pr_warn("\nother info that might help us debug this:\n");
3033 print_deadlock_scenario(next, prev);
3034 lockdep_print_held_locks(curr);
3035
3036 pr_warn("\nstack backtrace:\n");
3037 dump_stack();
3038
3039 nbcon_cpu_emergency_exit();
3040}
3041
3042/*
3043 * Check whether we are holding such a class already.
3044 *
3045 * (Note that this has to be done separately, because the graph cannot
3046 * detect such classes of deadlocks.)
3047 *
3048 * Returns: 0 on deadlock detected, 1 on OK, 2 if another lock with the same
3049 * lock class is held but nest_lock is also held, i.e. we rely on the
3050 * nest_lock to avoid the deadlock.
3051 */
3052static int
3053check_deadlock(struct task_struct *curr, struct held_lock *next)
3054{
3055 struct lock_class *class;
3056 struct held_lock *prev;
3057 struct held_lock *nest = NULL;
3058 int i;
3059
3060 for (i = 0; i < curr->lockdep_depth; i++) {
3061 prev = curr->held_locks + i;
3062
3063 if (prev->instance == next->nest_lock)
3064 nest = prev;
3065
3066 if (hlock_class(prev) != hlock_class(next))
3067 continue;
3068
3069 /*
3070 * Allow read-after-read recursion of the same
3071 * lock class (i.e. read_lock(lock)+read_lock(lock)):
3072 */
3073 if ((next->read == 2) && prev->read)
3074 continue;
3075
3076 class = hlock_class(prev);
3077
3078 if (class->cmp_fn &&
3079 class->cmp_fn(prev->instance, next->instance) < 0)
3080 continue;
3081
3082 /*
3083 * We're holding the nest_lock, which serializes this lock's
3084 * nesting behaviour.
3085 */
3086 if (nest)
3087 return 2;
3088
3089 print_deadlock_bug(curr, prev, next);
3090 return 0;
3091 }
3092 return 1;
3093}
3094
3095/*
3096 * There was a chain-cache miss, and we are about to add a new dependency
3097 * to a previous lock. We validate the following rules:
3098 *
3099 * - would the adding of the <prev> -> <next> dependency create a
3100 * circular dependency in the graph? [== circular deadlock]
3101 *
3102 * - does the new prev->next dependency connect any hardirq-safe lock
3103 * (in the full backwards-subgraph starting at <prev>) with any
3104 * hardirq-unsafe lock (in the full forwards-subgraph starting at
3105 * <next>)? [== illegal lock inversion with hardirq contexts]
3106 *
3107 * - does the new prev->next dependency connect any softirq-safe lock
3108 * (in the full backwards-subgraph starting at <prev>) with any
3109 * softirq-unsafe lock (in the full forwards-subgraph starting at
3110 * <next>)? [== illegal lock inversion with softirq contexts]
3111 *
3112 * any of these scenarios could lead to a deadlock.
3113 *
3114 * Then if all the validations pass, we add the forwards and backwards
3115 * dependency.
3116 */
3117static int
3118check_prev_add(struct task_struct *curr, struct held_lock *prev,
3119 struct held_lock *next, u16 distance,
3120 struct lock_trace **const trace)
3121{
3122 struct lock_list *entry;
3123 enum bfs_result ret;
3124
3125 if (!hlock_class(prev)->key || !hlock_class(next)->key) {
3126 /*
3127 * The warning statements below may trigger a use-after-free
3128 * of the class name. It is better to trigger a use-after free
3129 * and to have the class name most of the time instead of not
3130 * having the class name available.
3131 */
3132 WARN_ONCE(!debug_locks_silent && !hlock_class(prev)->key,
3133 "Detected use-after-free of lock class %px/%s\n",
3134 hlock_class(prev),
3135 hlock_class(prev)->name);
3136 WARN_ONCE(!debug_locks_silent && !hlock_class(next)->key,
3137 "Detected use-after-free of lock class %px/%s\n",
3138 hlock_class(next),
3139 hlock_class(next)->name);
3140 return 2;
3141 }
3142
3143 if (prev->class_idx == next->class_idx) {
3144 struct lock_class *class = hlock_class(prev);
3145
3146 if (class->cmp_fn &&
3147 class->cmp_fn(prev->instance, next->instance) < 0)
3148 return 2;
3149 }
3150
3151 /*
3152 * Prove that the new <prev> -> <next> dependency would not
3153 * create a circular dependency in the graph. (We do this by
3154 * a breadth-first search into the graph starting at <next>,
3155 * and check whether we can reach <prev>.)
3156 *
3157 * The search is limited by the size of the circular queue (i.e.,
3158 * MAX_CIRCULAR_QUEUE_SIZE) which keeps track of a breadth of nodes
3159 * in the graph whose neighbours are to be checked.
3160 */
3161 ret = check_noncircular(next, prev, trace);
3162 if (unlikely(bfs_error(ret) || ret == BFS_RMATCH))
3163 return 0;
3164
3165 if (!check_irq_usage(curr, prev, next))
3166 return 0;
3167
3168 /*
3169 * Is the <prev> -> <next> dependency already present?
3170 *
3171 * (this may occur even though this is a new chain: consider
3172 * e.g. the L1 -> L2 -> L3 -> L4 and the L5 -> L1 -> L2 -> L3
3173 * chains - the second one will be new, but L1 already has
3174 * L2 added to its dependency list, due to the first chain.)
3175 */
3176 list_for_each_entry(entry, &hlock_class(prev)->locks_after, entry) {
3177 if (entry->class == hlock_class(next)) {
3178 if (distance == 1)
3179 entry->distance = 1;
3180 entry->dep |= calc_dep(prev, next);
3181
3182 /*
3183 * Also, update the reverse dependency in @next's
3184 * ->locks_before list.
3185 *
3186 * Here we reuse @entry as the cursor, which is fine
3187 * because we won't go to the next iteration of the
3188 * outer loop:
3189 *
3190 * For normal cases, we return in the inner loop.
3191 *
3192 * If we fail to return, we have inconsistency, i.e.
3193 * <prev>::locks_after contains <next> while
3194 * <next>::locks_before doesn't contain <prev>. In
3195 * that case, we return after the inner and indicate
3196 * something is wrong.
3197 */
3198 list_for_each_entry(entry, &hlock_class(next)->locks_before, entry) {
3199 if (entry->class == hlock_class(prev)) {
3200 if (distance == 1)
3201 entry->distance = 1;
3202 entry->dep |= calc_depb(prev, next);
3203 return 1;
3204 }
3205 }
3206
3207 /* <prev> is not found in <next>::locks_before */
3208 return 0;
3209 }
3210 }
3211
3212 /*
3213 * Is the <prev> -> <next> link redundant?
3214 */
3215 ret = check_redundant(prev, next);
3216 if (bfs_error(ret))
3217 return 0;
3218 else if (ret == BFS_RMATCH)
3219 return 2;
3220
3221 if (!*trace) {
3222 *trace = save_trace();
3223 if (!*trace)
3224 return 0;
3225 }
3226
3227 /*
3228 * Ok, all validations passed, add the new lock
3229 * to the previous lock's dependency list:
3230 */
3231 ret = add_lock_to_list(hlock_class(next), hlock_class(prev),
3232 &hlock_class(prev)->locks_after, distance,
3233 calc_dep(prev, next), *trace);
3234
3235 if (!ret)
3236 return 0;
3237
3238 ret = add_lock_to_list(hlock_class(prev), hlock_class(next),
3239 &hlock_class(next)->locks_before, distance,
3240 calc_depb(prev, next), *trace);
3241 if (!ret)
3242 return 0;
3243
3244 return 2;
3245}
3246
3247/*
3248 * Add the dependency to all directly-previous locks that are 'relevant'.
3249 * The ones that are relevant are (in increasing distance from curr):
3250 * all consecutive trylock entries and the final non-trylock entry - or
3251 * the end of this context's lock-chain - whichever comes first.
3252 */
3253static int
3254check_prevs_add(struct task_struct *curr, struct held_lock *next)
3255{
3256 struct lock_trace *trace = NULL;
3257 int depth = curr->lockdep_depth;
3258 struct held_lock *hlock;
3259
3260 /*
3261 * Debugging checks.
3262 *
3263 * Depth must not be zero for a non-head lock:
3264 */
3265 if (!depth)
3266 goto out_bug;
3267 /*
3268 * At least two relevant locks must exist for this
3269 * to be a head:
3270 */
3271 if (curr->held_locks[depth].irq_context !=
3272 curr->held_locks[depth-1].irq_context)
3273 goto out_bug;
3274
3275 for (;;) {
3276 u16 distance = curr->lockdep_depth - depth + 1;
3277 hlock = curr->held_locks + depth - 1;
3278
3279 if (hlock->check) {
3280 int ret = check_prev_add(curr, hlock, next, distance, &trace);
3281 if (!ret)
3282 return 0;
3283
3284 /*
3285 * Stop after the first non-trylock entry,
3286 * as non-trylock entries have added their
3287 * own direct dependencies already, so this
3288 * lock is connected to them indirectly:
3289 */
3290 if (!hlock->trylock)
3291 break;
3292 }
3293
3294 depth--;
3295 /*
3296 * End of lock-stack?
3297 */
3298 if (!depth)
3299 break;
3300 /*
3301 * Stop the search if we cross into another context:
3302 */
3303 if (curr->held_locks[depth].irq_context !=
3304 curr->held_locks[depth-1].irq_context)
3305 break;
3306 }
3307 return 1;
3308out_bug:
3309 if (!debug_locks_off_graph_unlock())
3310 return 0;
3311
3312 /*
3313 * Clearly we all shouldn't be here, but since we made it we
3314 * can reliable say we messed up our state. See the above two
3315 * gotos for reasons why we could possibly end up here.
3316 */
3317 WARN_ON(1);
3318
3319 return 0;
3320}
3321
3322struct lock_chain lock_chains[MAX_LOCKDEP_CHAINS];
3323static DECLARE_BITMAP(lock_chains_in_use, MAX_LOCKDEP_CHAINS);
3324static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
3325unsigned long nr_zapped_lock_chains;
3326unsigned int nr_free_chain_hlocks; /* Free chain_hlocks in buckets */
3327unsigned int nr_lost_chain_hlocks; /* Lost chain_hlocks */
3328unsigned int nr_large_chain_blocks; /* size > MAX_CHAIN_BUCKETS */
3329
3330/*
3331 * The first 2 chain_hlocks entries in the chain block in the bucket
3332 * list contains the following meta data:
3333 *
3334 * entry[0]:
3335 * Bit 15 - always set to 1 (it is not a class index)
3336 * Bits 0-14 - upper 15 bits of the next block index
3337 * entry[1] - lower 16 bits of next block index
3338 *
3339 * A next block index of all 1 bits means it is the end of the list.
3340 *
3341 * On the unsized bucket (bucket-0), the 3rd and 4th entries contain
3342 * the chain block size:
3343 *
3344 * entry[2] - upper 16 bits of the chain block size
3345 * entry[3] - lower 16 bits of the chain block size
3346 */
3347#define MAX_CHAIN_BUCKETS 16
3348#define CHAIN_BLK_FLAG (1U << 15)
3349#define CHAIN_BLK_LIST_END 0xFFFFU
3350
3351static int chain_block_buckets[MAX_CHAIN_BUCKETS];
3352
3353static inline int size_to_bucket(int size)
3354{
3355 if (size > MAX_CHAIN_BUCKETS)
3356 return 0;
3357
3358 return size - 1;
3359}
3360
3361/*
3362 * Iterate all the chain blocks in a bucket.
3363 */
3364#define for_each_chain_block(bucket, prev, curr) \
3365 for ((prev) = -1, (curr) = chain_block_buckets[bucket]; \
3366 (curr) >= 0; \
3367 (prev) = (curr), (curr) = chain_block_next(curr))
3368
3369/*
3370 * next block or -1
3371 */
3372static inline int chain_block_next(int offset)
3373{
3374 int next = chain_hlocks[offset];
3375
3376 WARN_ON_ONCE(!(next & CHAIN_BLK_FLAG));
3377
3378 if (next == CHAIN_BLK_LIST_END)
3379 return -1;
3380
3381 next &= ~CHAIN_BLK_FLAG;
3382 next <<= 16;
3383 next |= chain_hlocks[offset + 1];
3384
3385 return next;
3386}
3387
3388/*
3389 * bucket-0 only
3390 */
3391static inline int chain_block_size(int offset)
3392{
3393 return (chain_hlocks[offset + 2] << 16) | chain_hlocks[offset + 3];
3394}
3395
3396static inline void init_chain_block(int offset, int next, int bucket, int size)
3397{
3398 chain_hlocks[offset] = (next >> 16) | CHAIN_BLK_FLAG;
3399 chain_hlocks[offset + 1] = (u16)next;
3400
3401 if (size && !bucket) {
3402 chain_hlocks[offset + 2] = size >> 16;
3403 chain_hlocks[offset + 3] = (u16)size;
3404 }
3405}
3406
3407static inline void add_chain_block(int offset, int size)
3408{
3409 int bucket = size_to_bucket(size);
3410 int next = chain_block_buckets[bucket];
3411 int prev, curr;
3412
3413 if (unlikely(size < 2)) {
3414 /*
3415 * We can't store single entries on the freelist. Leak them.
3416 *
3417 * One possible way out would be to uniquely mark them, other
3418 * than with CHAIN_BLK_FLAG, such that we can recover them when
3419 * the block before it is re-added.
3420 */
3421 if (size)
3422 nr_lost_chain_hlocks++;
3423 return;
3424 }
3425
3426 nr_free_chain_hlocks += size;
3427 if (!bucket) {
3428 nr_large_chain_blocks++;
3429
3430 /*
3431 * Variable sized, sort large to small.
3432 */
3433 for_each_chain_block(0, prev, curr) {
3434 if (size >= chain_block_size(curr))
3435 break;
3436 }
3437 init_chain_block(offset, curr, 0, size);
3438 if (prev < 0)
3439 chain_block_buckets[0] = offset;
3440 else
3441 init_chain_block(prev, offset, 0, 0);
3442 return;
3443 }
3444 /*
3445 * Fixed size, add to head.
3446 */
3447 init_chain_block(offset, next, bucket, size);
3448 chain_block_buckets[bucket] = offset;
3449}
3450
3451/*
3452 * Only the first block in the list can be deleted.
3453 *
3454 * For the variable size bucket[0], the first block (the largest one) is
3455 * returned, broken up and put back into the pool. So if a chain block of
3456 * length > MAX_CHAIN_BUCKETS is ever used and zapped, it will just be
3457 * queued up after the primordial chain block and never be used until the
3458 * hlock entries in the primordial chain block is almost used up. That
3459 * causes fragmentation and reduce allocation efficiency. That can be
3460 * monitored by looking at the "large chain blocks" number in lockdep_stats.
3461 */
3462static inline void del_chain_block(int bucket, int size, int next)
3463{
3464 nr_free_chain_hlocks -= size;
3465 chain_block_buckets[bucket] = next;
3466
3467 if (!bucket)
3468 nr_large_chain_blocks--;
3469}
3470
3471static void init_chain_block_buckets(void)
3472{
3473 int i;
3474
3475 for (i = 0; i < MAX_CHAIN_BUCKETS; i++)
3476 chain_block_buckets[i] = -1;
3477
3478 add_chain_block(0, ARRAY_SIZE(chain_hlocks));
3479}
3480
3481/*
3482 * Return offset of a chain block of the right size or -1 if not found.
3483 *
3484 * Fairly simple worst-fit allocator with the addition of a number of size
3485 * specific free lists.
3486 */
3487static int alloc_chain_hlocks(int req)
3488{
3489 int bucket, curr, size;
3490
3491 /*
3492 * We rely on the MSB to act as an escape bit to denote freelist
3493 * pointers. Make sure this bit isn't set in 'normal' class_idx usage.
3494 */
3495 BUILD_BUG_ON((MAX_LOCKDEP_KEYS-1) & CHAIN_BLK_FLAG);
3496
3497 init_data_structures_once();
3498
3499 if (nr_free_chain_hlocks < req)
3500 return -1;
3501
3502 /*
3503 * We require a minimum of 2 (u16) entries to encode a freelist
3504 * 'pointer'.
3505 */
3506 req = max(req, 2);
3507 bucket = size_to_bucket(req);
3508 curr = chain_block_buckets[bucket];
3509
3510 if (bucket) {
3511 if (curr >= 0) {
3512 del_chain_block(bucket, req, chain_block_next(curr));
3513 return curr;
3514 }
3515 /* Try bucket 0 */
3516 curr = chain_block_buckets[0];
3517 }
3518
3519 /*
3520 * The variable sized freelist is sorted by size; the first entry is
3521 * the largest. Use it if it fits.
3522 */
3523 if (curr >= 0) {
3524 size = chain_block_size(curr);
3525 if (likely(size >= req)) {
3526 del_chain_block(0, size, chain_block_next(curr));
3527 if (size > req)
3528 add_chain_block(curr + req, size - req);
3529 return curr;
3530 }
3531 }
3532
3533 /*
3534 * Last resort, split a block in a larger sized bucket.
3535 */
3536 for (size = MAX_CHAIN_BUCKETS; size > req; size--) {
3537 bucket = size_to_bucket(size);
3538 curr = chain_block_buckets[bucket];
3539 if (curr < 0)
3540 continue;
3541
3542 del_chain_block(bucket, size, chain_block_next(curr));
3543 add_chain_block(curr + req, size - req);
3544 return curr;
3545 }
3546
3547 return -1;
3548}
3549
3550static inline void free_chain_hlocks(int base, int size)
3551{
3552 add_chain_block(base, max(size, 2));
3553}
3554
3555struct lock_class *lock_chain_get_class(struct lock_chain *chain, int i)
3556{
3557 u16 chain_hlock = chain_hlocks[chain->base + i];
3558 unsigned int class_idx = chain_hlock_class_idx(chain_hlock);
3559
3560 return lock_classes + class_idx;
3561}
3562
3563/*
3564 * Returns the index of the first held_lock of the current chain
3565 */
3566static inline int get_first_held_lock(struct task_struct *curr,
3567 struct held_lock *hlock)
3568{
3569 int i;
3570 struct held_lock *hlock_curr;
3571
3572 for (i = curr->lockdep_depth - 1; i >= 0; i--) {
3573 hlock_curr = curr->held_locks + i;
3574 if (hlock_curr->irq_context != hlock->irq_context)
3575 break;
3576
3577 }
3578
3579 return ++i;
3580}
3581
3582#ifdef CONFIG_DEBUG_LOCKDEP
3583/*
3584 * Returns the next chain_key iteration
3585 */
3586static u64 print_chain_key_iteration(u16 hlock_id, u64 chain_key)
3587{
3588 u64 new_chain_key = iterate_chain_key(chain_key, hlock_id);
3589
3590 printk(" hlock_id:%d -> chain_key:%016Lx",
3591 (unsigned int)hlock_id,
3592 (unsigned long long)new_chain_key);
3593 return new_chain_key;
3594}
3595
3596static void
3597print_chain_keys_held_locks(struct task_struct *curr, struct held_lock *hlock_next)
3598{
3599 struct held_lock *hlock;
3600 u64 chain_key = INITIAL_CHAIN_KEY;
3601 int depth = curr->lockdep_depth;
3602 int i = get_first_held_lock(curr, hlock_next);
3603
3604 printk("depth: %u (irq_context %u)\n", depth - i + 1,
3605 hlock_next->irq_context);
3606 for (; i < depth; i++) {
3607 hlock = curr->held_locks + i;
3608 chain_key = print_chain_key_iteration(hlock_id(hlock), chain_key);
3609
3610 print_lock(hlock);
3611 }
3612
3613 print_chain_key_iteration(hlock_id(hlock_next), chain_key);
3614 print_lock(hlock_next);
3615}
3616
3617static void print_chain_keys_chain(struct lock_chain *chain)
3618{
3619 int i;
3620 u64 chain_key = INITIAL_CHAIN_KEY;
3621 u16 hlock_id;
3622
3623 printk("depth: %u\n", chain->depth);
3624 for (i = 0; i < chain->depth; i++) {
3625 hlock_id = chain_hlocks[chain->base + i];
3626 chain_key = print_chain_key_iteration(hlock_id, chain_key);
3627
3628 print_lock_name(NULL, lock_classes + chain_hlock_class_idx(hlock_id));
3629 printk("\n");
3630 }
3631}
3632
3633static void print_collision(struct task_struct *curr,
3634 struct held_lock *hlock_next,
3635 struct lock_chain *chain)
3636{
3637 nbcon_cpu_emergency_enter();
3638
3639 pr_warn("\n");
3640 pr_warn("============================\n");
3641 pr_warn("WARNING: chain_key collision\n");
3642 print_kernel_ident();
3643 pr_warn("----------------------------\n");
3644 pr_warn("%s/%d: ", current->comm, task_pid_nr(current));
3645 pr_warn("Hash chain already cached but the contents don't match!\n");
3646
3647 pr_warn("Held locks:");
3648 print_chain_keys_held_locks(curr, hlock_next);
3649
3650 pr_warn("Locks in cached chain:");
3651 print_chain_keys_chain(chain);
3652
3653 pr_warn("\nstack backtrace:\n");
3654 dump_stack();
3655
3656 nbcon_cpu_emergency_exit();
3657}
3658#endif
3659
3660/*
3661 * Checks whether the chain and the current held locks are consistent
3662 * in depth and also in content. If they are not it most likely means
3663 * that there was a collision during the calculation of the chain_key.
3664 * Returns: 0 not passed, 1 passed
3665 */
3666static int check_no_collision(struct task_struct *curr,
3667 struct held_lock *hlock,
3668 struct lock_chain *chain)
3669{
3670#ifdef CONFIG_DEBUG_LOCKDEP
3671 int i, j, id;
3672
3673 i = get_first_held_lock(curr, hlock);
3674
3675 if (DEBUG_LOCKS_WARN_ON(chain->depth != curr->lockdep_depth - (i - 1))) {
3676 print_collision(curr, hlock, chain);
3677 return 0;
3678 }
3679
3680 for (j = 0; j < chain->depth - 1; j++, i++) {
3681 id = hlock_id(&curr->held_locks[i]);
3682
3683 if (DEBUG_LOCKS_WARN_ON(chain_hlocks[chain->base + j] != id)) {
3684 print_collision(curr, hlock, chain);
3685 return 0;
3686 }
3687 }
3688#endif
3689 return 1;
3690}
3691
3692/*
3693 * Given an index that is >= -1, return the index of the next lock chain.
3694 * Return -2 if there is no next lock chain.
3695 */
3696long lockdep_next_lockchain(long i)
3697{
3698 i = find_next_bit(lock_chains_in_use, ARRAY_SIZE(lock_chains), i + 1);
3699 return i < ARRAY_SIZE(lock_chains) ? i : -2;
3700}
3701
3702unsigned long lock_chain_count(void)
3703{
3704 return bitmap_weight(lock_chains_in_use, ARRAY_SIZE(lock_chains));
3705}
3706
3707/* Must be called with the graph lock held. */
3708static struct lock_chain *alloc_lock_chain(void)
3709{
3710 int idx = find_first_zero_bit(lock_chains_in_use,
3711 ARRAY_SIZE(lock_chains));
3712
3713 if (unlikely(idx >= ARRAY_SIZE(lock_chains)))
3714 return NULL;
3715 __set_bit(idx, lock_chains_in_use);
3716 return lock_chains + idx;
3717}
3718
3719/*
3720 * Adds a dependency chain into chain hashtable. And must be called with
3721 * graph_lock held.
3722 *
3723 * Return 0 if fail, and graph_lock is released.
3724 * Return 1 if succeed, with graph_lock held.
3725 */
3726static inline int add_chain_cache(struct task_struct *curr,
3727 struct held_lock *hlock,
3728 u64 chain_key)
3729{
3730 struct hlist_head *hash_head = chainhashentry(chain_key);
3731 struct lock_chain *chain;
3732 int i, j;
3733
3734 /*
3735 * The caller must hold the graph lock, ensure we've got IRQs
3736 * disabled to make this an IRQ-safe lock.. for recursion reasons
3737 * lockdep won't complain about its own locking errors.
3738 */
3739 if (lockdep_assert_locked())
3740 return 0;
3741
3742 chain = alloc_lock_chain();
3743 if (!chain) {
3744 if (!debug_locks_off_graph_unlock())
3745 return 0;
3746
3747 nbcon_cpu_emergency_enter();
3748 print_lockdep_off("BUG: MAX_LOCKDEP_CHAINS too low!");
3749 dump_stack();
3750 nbcon_cpu_emergency_exit();
3751 return 0;
3752 }
3753 chain->chain_key = chain_key;
3754 chain->irq_context = hlock->irq_context;
3755 i = get_first_held_lock(curr, hlock);
3756 chain->depth = curr->lockdep_depth + 1 - i;
3757
3758 BUILD_BUG_ON((1UL << 24) <= ARRAY_SIZE(chain_hlocks));
3759 BUILD_BUG_ON((1UL << 6) <= ARRAY_SIZE(curr->held_locks));
3760 BUILD_BUG_ON((1UL << 8*sizeof(chain_hlocks[0])) <= ARRAY_SIZE(lock_classes));
3761
3762 j = alloc_chain_hlocks(chain->depth);
3763 if (j < 0) {
3764 if (!debug_locks_off_graph_unlock())
3765 return 0;
3766
3767 nbcon_cpu_emergency_enter();
3768 print_lockdep_off("BUG: MAX_LOCKDEP_CHAIN_HLOCKS too low!");
3769 dump_stack();
3770 nbcon_cpu_emergency_exit();
3771 return 0;
3772 }
3773
3774 chain->base = j;
3775 for (j = 0; j < chain->depth - 1; j++, i++) {
3776 int lock_id = hlock_id(curr->held_locks + i);
3777
3778 chain_hlocks[chain->base + j] = lock_id;
3779 }
3780 chain_hlocks[chain->base + j] = hlock_id(hlock);
3781 hlist_add_head_rcu(&chain->entry, hash_head);
3782 debug_atomic_inc(chain_lookup_misses);
3783 inc_chains(chain->irq_context);
3784
3785 return 1;
3786}
3787
3788/*
3789 * Look up a dependency chain. Must be called with either the graph lock or
3790 * the RCU read lock held.
3791 */
3792static inline struct lock_chain *lookup_chain_cache(u64 chain_key)
3793{
3794 struct hlist_head *hash_head = chainhashentry(chain_key);
3795 struct lock_chain *chain;
3796
3797 hlist_for_each_entry_rcu(chain, hash_head, entry) {
3798 if (READ_ONCE(chain->chain_key) == chain_key) {
3799 debug_atomic_inc(chain_lookup_hits);
3800 return chain;
3801 }
3802 }
3803 return NULL;
3804}
3805
3806/*
3807 * If the key is not present yet in dependency chain cache then
3808 * add it and return 1 - in this case the new dependency chain is
3809 * validated. If the key is already hashed, return 0.
3810 * (On return with 1 graph_lock is held.)
3811 */
3812static inline int lookup_chain_cache_add(struct task_struct *curr,
3813 struct held_lock *hlock,
3814 u64 chain_key)
3815{
3816 struct lock_class *class = hlock_class(hlock);
3817 struct lock_chain *chain = lookup_chain_cache(chain_key);
3818
3819 if (chain) {
3820cache_hit:
3821 if (!check_no_collision(curr, hlock, chain))
3822 return 0;
3823
3824 if (very_verbose(class)) {
3825 printk("\nhash chain already cached, key: "
3826 "%016Lx tail class: [%px] %s\n",
3827 (unsigned long long)chain_key,
3828 class->key, class->name);
3829 }
3830
3831 return 0;
3832 }
3833
3834 if (very_verbose(class)) {
3835 printk("\nnew hash chain, key: %016Lx tail class: [%px] %s\n",
3836 (unsigned long long)chain_key, class->key, class->name);
3837 }
3838
3839 if (!graph_lock())
3840 return 0;
3841
3842 /*
3843 * We have to walk the chain again locked - to avoid duplicates:
3844 */
3845 chain = lookup_chain_cache(chain_key);
3846 if (chain) {
3847 graph_unlock();
3848 goto cache_hit;
3849 }
3850
3851 if (!add_chain_cache(curr, hlock, chain_key))
3852 return 0;
3853
3854 return 1;
3855}
3856
3857static int validate_chain(struct task_struct *curr,
3858 struct held_lock *hlock,
3859 int chain_head, u64 chain_key)
3860{
3861 /*
3862 * Trylock needs to maintain the stack of held locks, but it
3863 * does not add new dependencies, because trylock can be done
3864 * in any order.
3865 *
3866 * We look up the chain_key and do the O(N^2) check and update of
3867 * the dependencies only if this is a new dependency chain.
3868 * (If lookup_chain_cache_add() return with 1 it acquires
3869 * graph_lock for us)
3870 */
3871 if (!hlock->trylock && hlock->check &&
3872 lookup_chain_cache_add(curr, hlock, chain_key)) {
3873 /*
3874 * Check whether last held lock:
3875 *
3876 * - is irq-safe, if this lock is irq-unsafe
3877 * - is softirq-safe, if this lock is hardirq-unsafe
3878 *
3879 * And check whether the new lock's dependency graph
3880 * could lead back to the previous lock:
3881 *
3882 * - within the current held-lock stack
3883 * - across our accumulated lock dependency records
3884 *
3885 * any of these scenarios could lead to a deadlock.
3886 */
3887 /*
3888 * The simple case: does the current hold the same lock
3889 * already?
3890 */
3891 int ret = check_deadlock(curr, hlock);
3892
3893 if (!ret)
3894 return 0;
3895 /*
3896 * Add dependency only if this lock is not the head
3897 * of the chain, and if the new lock introduces no more
3898 * lock dependency (because we already hold a lock with the
3899 * same lock class) nor deadlock (because the nest_lock
3900 * serializes nesting locks), see the comments for
3901 * check_deadlock().
3902 */
3903 if (!chain_head && ret != 2) {
3904 if (!check_prevs_add(curr, hlock))
3905 return 0;
3906 }
3907
3908 graph_unlock();
3909 } else {
3910 /* after lookup_chain_cache_add(): */
3911 if (unlikely(!debug_locks))
3912 return 0;
3913 }
3914
3915 return 1;
3916}
3917#else
3918static inline int validate_chain(struct task_struct *curr,
3919 struct held_lock *hlock,
3920 int chain_head, u64 chain_key)
3921{
3922 return 1;
3923}
3924
3925static void init_chain_block_buckets(void) { }
3926#endif /* CONFIG_PROVE_LOCKING */
3927
3928/*
3929 * We are building curr_chain_key incrementally, so double-check
3930 * it from scratch, to make sure that it's done correctly:
3931 */
3932static void check_chain_key(struct task_struct *curr)
3933{
3934#ifdef CONFIG_DEBUG_LOCKDEP
3935 struct held_lock *hlock, *prev_hlock = NULL;
3936 unsigned int i;
3937 u64 chain_key = INITIAL_CHAIN_KEY;
3938
3939 for (i = 0; i < curr->lockdep_depth; i++) {
3940 hlock = curr->held_locks + i;
3941 if (chain_key != hlock->prev_chain_key) {
3942 debug_locks_off();
3943 /*
3944 * We got mighty confused, our chain keys don't match
3945 * with what we expect, someone trample on our task state?
3946 */
3947 WARN(1, "hm#1, depth: %u [%u], %016Lx != %016Lx\n",
3948 curr->lockdep_depth, i,
3949 (unsigned long long)chain_key,
3950 (unsigned long long)hlock->prev_chain_key);
3951 return;
3952 }
3953
3954 /*
3955 * hlock->class_idx can't go beyond MAX_LOCKDEP_KEYS, but is
3956 * it registered lock class index?
3957 */
3958 if (DEBUG_LOCKS_WARN_ON(!test_bit(hlock->class_idx, lock_classes_in_use)))
3959 return;
3960
3961 if (prev_hlock && (prev_hlock->irq_context !=
3962 hlock->irq_context))
3963 chain_key = INITIAL_CHAIN_KEY;
3964 chain_key = iterate_chain_key(chain_key, hlock_id(hlock));
3965 prev_hlock = hlock;
3966 }
3967 if (chain_key != curr->curr_chain_key) {
3968 debug_locks_off();
3969 /*
3970 * More smoking hash instead of calculating it, damn see these
3971 * numbers float.. I bet that a pink elephant stepped on my memory.
3972 */
3973 WARN(1, "hm#2, depth: %u [%u], %016Lx != %016Lx\n",
3974 curr->lockdep_depth, i,
3975 (unsigned long long)chain_key,
3976 (unsigned long long)curr->curr_chain_key);
3977 }
3978#endif
3979}
3980
3981#ifdef CONFIG_PROVE_LOCKING
3982static int mark_lock(struct task_struct *curr, struct held_lock *this,
3983 enum lock_usage_bit new_bit);
3984
3985static void print_usage_bug_scenario(struct held_lock *lock)
3986{
3987 struct lock_class *class = hlock_class(lock);
3988
3989 printk(" Possible unsafe locking scenario:\n\n");
3990 printk(" CPU0\n");
3991 printk(" ----\n");
3992 printk(" lock(");
3993 __print_lock_name(lock, class);
3994 printk(KERN_CONT ");\n");
3995 printk(" <Interrupt>\n");
3996 printk(" lock(");
3997 __print_lock_name(lock, class);
3998 printk(KERN_CONT ");\n");
3999 printk("\n *** DEADLOCK ***\n\n");
4000}
4001
4002static void
4003print_usage_bug(struct task_struct *curr, struct held_lock *this,
4004 enum lock_usage_bit prev_bit, enum lock_usage_bit new_bit)
4005{
4006 if (!debug_locks_off() || debug_locks_silent)
4007 return;
4008
4009 nbcon_cpu_emergency_enter();
4010
4011 pr_warn("\n");
4012 pr_warn("================================\n");
4013 pr_warn("WARNING: inconsistent lock state\n");
4014 print_kernel_ident();
4015 pr_warn("--------------------------------\n");
4016
4017 pr_warn("inconsistent {%s} -> {%s} usage.\n",
4018 usage_str[prev_bit], usage_str[new_bit]);
4019
4020 pr_warn("%s/%d [HC%u[%lu]:SC%u[%lu]:HE%u:SE%u] takes:\n",
4021 curr->comm, task_pid_nr(curr),
4022 lockdep_hardirq_context(), hardirq_count() >> HARDIRQ_SHIFT,
4023 lockdep_softirq_context(curr), softirq_count() >> SOFTIRQ_SHIFT,
4024 lockdep_hardirqs_enabled(),
4025 lockdep_softirqs_enabled(curr));
4026 print_lock(this);
4027
4028 pr_warn("{%s} state was registered at:\n", usage_str[prev_bit]);
4029 print_lock_trace(hlock_class(this)->usage_traces[prev_bit], 1);
4030
4031 print_irqtrace_events(curr);
4032 pr_warn("\nother info that might help us debug this:\n");
4033 print_usage_bug_scenario(this);
4034
4035 lockdep_print_held_locks(curr);
4036
4037 pr_warn("\nstack backtrace:\n");
4038 dump_stack();
4039
4040 nbcon_cpu_emergency_exit();
4041}
4042
4043/*
4044 * Print out an error if an invalid bit is set:
4045 */
4046static inline int
4047valid_state(struct task_struct *curr, struct held_lock *this,
4048 enum lock_usage_bit new_bit, enum lock_usage_bit bad_bit)
4049{
4050 if (unlikely(hlock_class(this)->usage_mask & (1 << bad_bit))) {
4051 graph_unlock();
4052 print_usage_bug(curr, this, bad_bit, new_bit);
4053 return 0;
4054 }
4055 return 1;
4056}
4057
4058
4059/*
4060 * print irq inversion bug:
4061 */
4062static void
4063print_irq_inversion_bug(struct task_struct *curr,
4064 struct lock_list *root, struct lock_list *other,
4065 struct held_lock *this, int forwards,
4066 const char *irqclass)
4067{
4068 struct lock_list *entry = other;
4069 struct lock_list *middle = NULL;
4070 int depth;
4071
4072 if (!debug_locks_off_graph_unlock() || debug_locks_silent)
4073 return;
4074
4075 nbcon_cpu_emergency_enter();
4076
4077 pr_warn("\n");
4078 pr_warn("========================================================\n");
4079 pr_warn("WARNING: possible irq lock inversion dependency detected\n");
4080 print_kernel_ident();
4081 pr_warn("--------------------------------------------------------\n");
4082 pr_warn("%s/%d just changed the state of lock:\n",
4083 curr->comm, task_pid_nr(curr));
4084 print_lock(this);
4085 if (forwards)
4086 pr_warn("but this lock took another, %s-unsafe lock in the past:\n", irqclass);
4087 else
4088 pr_warn("but this lock was taken by another, %s-safe lock in the past:\n", irqclass);
4089 print_lock_name(NULL, other->class);
4090 pr_warn("\n\nand interrupts could create inverse lock ordering between them.\n\n");
4091
4092 pr_warn("\nother info that might help us debug this:\n");
4093
4094 /* Find a middle lock (if one exists) */
4095 depth = get_lock_depth(other);
4096 do {
4097 if (depth == 0 && (entry != root)) {
4098 pr_warn("lockdep:%s bad path found in chain graph\n", __func__);
4099 break;
4100 }
4101 middle = entry;
4102 entry = get_lock_parent(entry);
4103 depth--;
4104 } while (entry && entry != root && (depth >= 0));
4105 if (forwards)
4106 print_irq_lock_scenario(root, other,
4107 middle ? middle->class : root->class, other->class);
4108 else
4109 print_irq_lock_scenario(other, root,
4110 middle ? middle->class : other->class, root->class);
4111
4112 lockdep_print_held_locks(curr);
4113
4114 pr_warn("\nthe shortest dependencies between 2nd lock and 1st lock:\n");
4115 root->trace = save_trace();
4116 if (!root->trace)
4117 goto out;
4118 print_shortest_lock_dependencies(other, root);
4119
4120 pr_warn("\nstack backtrace:\n");
4121 dump_stack();
4122out:
4123 nbcon_cpu_emergency_exit();
4124}
4125
4126/*
4127 * Prove that in the forwards-direction subgraph starting at <this>
4128 * there is no lock matching <mask>:
4129 */
4130static int
4131check_usage_forwards(struct task_struct *curr, struct held_lock *this,
4132 enum lock_usage_bit bit)
4133{
4134 enum bfs_result ret;
4135 struct lock_list root;
4136 struct lock_list *target_entry;
4137 enum lock_usage_bit read_bit = bit + LOCK_USAGE_READ_MASK;
4138 unsigned usage_mask = lock_flag(bit) | lock_flag(read_bit);
4139
4140 bfs_init_root(&root, this);
4141 ret = find_usage_forwards(&root, usage_mask, &target_entry);
4142 if (bfs_error(ret)) {
4143 print_bfs_bug(ret);
4144 return 0;
4145 }
4146 if (ret == BFS_RNOMATCH)
4147 return 1;
4148
4149 /* Check whether write or read usage is the match */
4150 if (target_entry->class->usage_mask & lock_flag(bit)) {
4151 print_irq_inversion_bug(curr, &root, target_entry,
4152 this, 1, state_name(bit));
4153 } else {
4154 print_irq_inversion_bug(curr, &root, target_entry,
4155 this, 1, state_name(read_bit));
4156 }
4157
4158 return 0;
4159}
4160
4161/*
4162 * Prove that in the backwards-direction subgraph starting at <this>
4163 * there is no lock matching <mask>:
4164 */
4165static int
4166check_usage_backwards(struct task_struct *curr, struct held_lock *this,
4167 enum lock_usage_bit bit)
4168{
4169 enum bfs_result ret;
4170 struct lock_list root;
4171 struct lock_list *target_entry;
4172 enum lock_usage_bit read_bit = bit + LOCK_USAGE_READ_MASK;
4173 unsigned usage_mask = lock_flag(bit) | lock_flag(read_bit);
4174
4175 bfs_init_rootb(&root, this);
4176 ret = find_usage_backwards(&root, usage_mask, &target_entry);
4177 if (bfs_error(ret)) {
4178 print_bfs_bug(ret);
4179 return 0;
4180 }
4181 if (ret == BFS_RNOMATCH)
4182 return 1;
4183
4184 /* Check whether write or read usage is the match */
4185 if (target_entry->class->usage_mask & lock_flag(bit)) {
4186 print_irq_inversion_bug(curr, &root, target_entry,
4187 this, 0, state_name(bit));
4188 } else {
4189 print_irq_inversion_bug(curr, &root, target_entry,
4190 this, 0, state_name(read_bit));
4191 }
4192
4193 return 0;
4194}
4195
4196void print_irqtrace_events(struct task_struct *curr)
4197{
4198 const struct irqtrace_events *trace = &curr->irqtrace;
4199
4200 nbcon_cpu_emergency_enter();
4201
4202 printk("irq event stamp: %u\n", trace->irq_events);
4203 printk("hardirqs last enabled at (%u): [<%px>] %pS\n",
4204 trace->hardirq_enable_event, (void *)trace->hardirq_enable_ip,
4205 (void *)trace->hardirq_enable_ip);
4206 printk("hardirqs last disabled at (%u): [<%px>] %pS\n",
4207 trace->hardirq_disable_event, (void *)trace->hardirq_disable_ip,
4208 (void *)trace->hardirq_disable_ip);
4209 printk("softirqs last enabled at (%u): [<%px>] %pS\n",
4210 trace->softirq_enable_event, (void *)trace->softirq_enable_ip,
4211 (void *)trace->softirq_enable_ip);
4212 printk("softirqs last disabled at (%u): [<%px>] %pS\n",
4213 trace->softirq_disable_event, (void *)trace->softirq_disable_ip,
4214 (void *)trace->softirq_disable_ip);
4215
4216 nbcon_cpu_emergency_exit();
4217}
4218
4219static int HARDIRQ_verbose(struct lock_class *class)
4220{
4221#if HARDIRQ_VERBOSE
4222 return class_filter(class);
4223#endif
4224 return 0;
4225}
4226
4227static int SOFTIRQ_verbose(struct lock_class *class)
4228{
4229#if SOFTIRQ_VERBOSE
4230 return class_filter(class);
4231#endif
4232 return 0;
4233}
4234
4235static int (*state_verbose_f[])(struct lock_class *class) = {
4236#define LOCKDEP_STATE(__STATE) \
4237 __STATE##_verbose,
4238#include "lockdep_states.h"
4239#undef LOCKDEP_STATE
4240};
4241
4242static inline int state_verbose(enum lock_usage_bit bit,
4243 struct lock_class *class)
4244{
4245 return state_verbose_f[bit >> LOCK_USAGE_DIR_MASK](class);
4246}
4247
4248typedef int (*check_usage_f)(struct task_struct *, struct held_lock *,
4249 enum lock_usage_bit bit, const char *name);
4250
4251static int
4252mark_lock_irq(struct task_struct *curr, struct held_lock *this,
4253 enum lock_usage_bit new_bit)
4254{
4255 int excl_bit = exclusive_bit(new_bit);
4256 int read = new_bit & LOCK_USAGE_READ_MASK;
4257 int dir = new_bit & LOCK_USAGE_DIR_MASK;
4258
4259 /*
4260 * Validate that this particular lock does not have conflicting
4261 * usage states.
4262 */
4263 if (!valid_state(curr, this, new_bit, excl_bit))
4264 return 0;
4265
4266 /*
4267 * Check for read in write conflicts
4268 */
4269 if (!read && !valid_state(curr, this, new_bit,
4270 excl_bit + LOCK_USAGE_READ_MASK))
4271 return 0;
4272
4273
4274 /*
4275 * Validate that the lock dependencies don't have conflicting usage
4276 * states.
4277 */
4278 if (dir) {
4279 /*
4280 * mark ENABLED has to look backwards -- to ensure no dependee
4281 * has USED_IN state, which, again, would allow recursion deadlocks.
4282 */
4283 if (!check_usage_backwards(curr, this, excl_bit))
4284 return 0;
4285 } else {
4286 /*
4287 * mark USED_IN has to look forwards -- to ensure no dependency
4288 * has ENABLED state, which would allow recursion deadlocks.
4289 */
4290 if (!check_usage_forwards(curr, this, excl_bit))
4291 return 0;
4292 }
4293
4294 if (state_verbose(new_bit, hlock_class(this)))
4295 return 2;
4296
4297 return 1;
4298}
4299
4300/*
4301 * Mark all held locks with a usage bit:
4302 */
4303static int
4304mark_held_locks(struct task_struct *curr, enum lock_usage_bit base_bit)
4305{
4306 struct held_lock *hlock;
4307 int i;
4308
4309 for (i = 0; i < curr->lockdep_depth; i++) {
4310 enum lock_usage_bit hlock_bit = base_bit;
4311 hlock = curr->held_locks + i;
4312
4313 if (hlock->read)
4314 hlock_bit += LOCK_USAGE_READ_MASK;
4315
4316 BUG_ON(hlock_bit >= LOCK_USAGE_STATES);
4317
4318 if (!hlock->check)
4319 continue;
4320
4321 if (!mark_lock(curr, hlock, hlock_bit))
4322 return 0;
4323 }
4324
4325 return 1;
4326}
4327
4328/*
4329 * Hardirqs will be enabled:
4330 */
4331static void __trace_hardirqs_on_caller(void)
4332{
4333 struct task_struct *curr = current;
4334
4335 /*
4336 * We are going to turn hardirqs on, so set the
4337 * usage bit for all held locks:
4338 */
4339 if (!mark_held_locks(curr, LOCK_ENABLED_HARDIRQ))
4340 return;
4341 /*
4342 * If we have softirqs enabled, then set the usage
4343 * bit for all held locks. (disabled hardirqs prevented
4344 * this bit from being set before)
4345 */
4346 if (curr->softirqs_enabled)
4347 mark_held_locks(curr, LOCK_ENABLED_SOFTIRQ);
4348}
4349
4350/**
4351 * lockdep_hardirqs_on_prepare - Prepare for enabling interrupts
4352 *
4353 * Invoked before a possible transition to RCU idle from exit to user or
4354 * guest mode. This ensures that all RCU operations are done before RCU
4355 * stops watching. After the RCU transition lockdep_hardirqs_on() has to be
4356 * invoked to set the final state.
4357 */
4358void lockdep_hardirqs_on_prepare(void)
4359{
4360 if (unlikely(!debug_locks))
4361 return;
4362
4363 /*
4364 * NMIs do not (and cannot) track lock dependencies, nothing to do.
4365 */
4366 if (unlikely(in_nmi()))
4367 return;
4368
4369 if (unlikely(this_cpu_read(lockdep_recursion)))
4370 return;
4371
4372 if (unlikely(lockdep_hardirqs_enabled())) {
4373 /*
4374 * Neither irq nor preemption are disabled here
4375 * so this is racy by nature but losing one hit
4376 * in a stat is not a big deal.
4377 */
4378 __debug_atomic_inc(redundant_hardirqs_on);
4379 return;
4380 }
4381
4382 /*
4383 * We're enabling irqs and according to our state above irqs weren't
4384 * already enabled, yet we find the hardware thinks they are in fact
4385 * enabled.. someone messed up their IRQ state tracing.
4386 */
4387 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
4388 return;
4389
4390 /*
4391 * See the fine text that goes along with this variable definition.
4392 */
4393 if (DEBUG_LOCKS_WARN_ON(early_boot_irqs_disabled))
4394 return;
4395
4396 /*
4397 * Can't allow enabling interrupts while in an interrupt handler,
4398 * that's general bad form and such. Recursion, limited stack etc..
4399 */
4400 if (DEBUG_LOCKS_WARN_ON(lockdep_hardirq_context()))
4401 return;
4402
4403 current->hardirq_chain_key = current->curr_chain_key;
4404
4405 lockdep_recursion_inc();
4406 __trace_hardirqs_on_caller();
4407 lockdep_recursion_finish();
4408}
4409EXPORT_SYMBOL_GPL(lockdep_hardirqs_on_prepare);
4410
4411void noinstr lockdep_hardirqs_on(unsigned long ip)
4412{
4413 struct irqtrace_events *trace = ¤t->irqtrace;
4414
4415 if (unlikely(!debug_locks))
4416 return;
4417
4418 /*
4419 * NMIs can happen in the middle of local_irq_{en,dis}able() where the
4420 * tracking state and hardware state are out of sync.
4421 *
4422 * NMIs must save lockdep_hardirqs_enabled() to restore IRQ state from,
4423 * and not rely on hardware state like normal interrupts.
4424 */
4425 if (unlikely(in_nmi())) {
4426 if (!IS_ENABLED(CONFIG_TRACE_IRQFLAGS_NMI))
4427 return;
4428
4429 /*
4430 * Skip:
4431 * - recursion check, because NMI can hit lockdep;
4432 * - hardware state check, because above;
4433 * - chain_key check, see lockdep_hardirqs_on_prepare().
4434 */
4435 goto skip_checks;
4436 }
4437
4438 if (unlikely(this_cpu_read(lockdep_recursion)))
4439 return;
4440
4441 if (lockdep_hardirqs_enabled()) {
4442 /*
4443 * Neither irq nor preemption are disabled here
4444 * so this is racy by nature but losing one hit
4445 * in a stat is not a big deal.
4446 */
4447 __debug_atomic_inc(redundant_hardirqs_on);
4448 return;
4449 }
4450
4451 /*
4452 * We're enabling irqs and according to our state above irqs weren't
4453 * already enabled, yet we find the hardware thinks they are in fact
4454 * enabled.. someone messed up their IRQ state tracing.
4455 */
4456 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
4457 return;
4458
4459 /*
4460 * Ensure the lock stack remained unchanged between
4461 * lockdep_hardirqs_on_prepare() and lockdep_hardirqs_on().
4462 */
4463 DEBUG_LOCKS_WARN_ON(current->hardirq_chain_key !=
4464 current->curr_chain_key);
4465
4466skip_checks:
4467 /* we'll do an OFF -> ON transition: */
4468 __this_cpu_write(hardirqs_enabled, 1);
4469 trace->hardirq_enable_ip = ip;
4470 trace->hardirq_enable_event = ++trace->irq_events;
4471 debug_atomic_inc(hardirqs_on_events);
4472}
4473EXPORT_SYMBOL_GPL(lockdep_hardirqs_on);
4474
4475/*
4476 * Hardirqs were disabled:
4477 */
4478void noinstr lockdep_hardirqs_off(unsigned long ip)
4479{
4480 if (unlikely(!debug_locks))
4481 return;
4482
4483 /*
4484 * Matching lockdep_hardirqs_on(), allow NMIs in the middle of lockdep;
4485 * they will restore the software state. This ensures the software
4486 * state is consistent inside NMIs as well.
4487 */
4488 if (in_nmi()) {
4489 if (!IS_ENABLED(CONFIG_TRACE_IRQFLAGS_NMI))
4490 return;
4491 } else if (__this_cpu_read(lockdep_recursion))
4492 return;
4493
4494 /*
4495 * So we're supposed to get called after you mask local IRQs, but for
4496 * some reason the hardware doesn't quite think you did a proper job.
4497 */
4498 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
4499 return;
4500
4501 if (lockdep_hardirqs_enabled()) {
4502 struct irqtrace_events *trace = ¤t->irqtrace;
4503
4504 /*
4505 * We have done an ON -> OFF transition:
4506 */
4507 __this_cpu_write(hardirqs_enabled, 0);
4508 trace->hardirq_disable_ip = ip;
4509 trace->hardirq_disable_event = ++trace->irq_events;
4510 debug_atomic_inc(hardirqs_off_events);
4511 } else {
4512 debug_atomic_inc(redundant_hardirqs_off);
4513 }
4514}
4515EXPORT_SYMBOL_GPL(lockdep_hardirqs_off);
4516
4517/*
4518 * Softirqs will be enabled:
4519 */
4520void lockdep_softirqs_on(unsigned long ip)
4521{
4522 struct irqtrace_events *trace = ¤t->irqtrace;
4523
4524 if (unlikely(!lockdep_enabled()))
4525 return;
4526
4527 /*
4528 * We fancy IRQs being disabled here, see softirq.c, avoids
4529 * funny state and nesting things.
4530 */
4531 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
4532 return;
4533
4534 if (current->softirqs_enabled) {
4535 debug_atomic_inc(redundant_softirqs_on);
4536 return;
4537 }
4538
4539 lockdep_recursion_inc();
4540 /*
4541 * We'll do an OFF -> ON transition:
4542 */
4543 current->softirqs_enabled = 1;
4544 trace->softirq_enable_ip = ip;
4545 trace->softirq_enable_event = ++trace->irq_events;
4546 debug_atomic_inc(softirqs_on_events);
4547 /*
4548 * We are going to turn softirqs on, so set the
4549 * usage bit for all held locks, if hardirqs are
4550 * enabled too:
4551 */
4552 if (lockdep_hardirqs_enabled())
4553 mark_held_locks(current, LOCK_ENABLED_SOFTIRQ);
4554 lockdep_recursion_finish();
4555}
4556
4557/*
4558 * Softirqs were disabled:
4559 */
4560void lockdep_softirqs_off(unsigned long ip)
4561{
4562 if (unlikely(!lockdep_enabled()))
4563 return;
4564
4565 /*
4566 * We fancy IRQs being disabled here, see softirq.c
4567 */
4568 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
4569 return;
4570
4571 if (current->softirqs_enabled) {
4572 struct irqtrace_events *trace = ¤t->irqtrace;
4573
4574 /*
4575 * We have done an ON -> OFF transition:
4576 */
4577 current->softirqs_enabled = 0;
4578 trace->softirq_disable_ip = ip;
4579 trace->softirq_disable_event = ++trace->irq_events;
4580 debug_atomic_inc(softirqs_off_events);
4581 /*
4582 * Whoops, we wanted softirqs off, so why aren't they?
4583 */
4584 DEBUG_LOCKS_WARN_ON(!softirq_count());
4585 } else
4586 debug_atomic_inc(redundant_softirqs_off);
4587}
4588
4589/**
4590 * lockdep_cleanup_dead_cpu - Ensure CPU lockdep state is cleanly stopped
4591 *
4592 * @cpu: index of offlined CPU
4593 * @idle: task pointer for offlined CPU's idle thread
4594 *
4595 * Invoked after the CPU is dead. Ensures that the tracing infrastructure
4596 * is left in a suitable state for the CPU to be subsequently brought
4597 * online again.
4598 */
4599void lockdep_cleanup_dead_cpu(unsigned int cpu, struct task_struct *idle)
4600{
4601 if (unlikely(!debug_locks))
4602 return;
4603
4604 if (unlikely(per_cpu(hardirqs_enabled, cpu))) {
4605 pr_warn("CPU %u left hardirqs enabled!", cpu);
4606 if (idle)
4607 print_irqtrace_events(idle);
4608 /* Clean it up for when the CPU comes online again. */
4609 per_cpu(hardirqs_enabled, cpu) = 0;
4610 }
4611}
4612
4613static int
4614mark_usage(struct task_struct *curr, struct held_lock *hlock, int check)
4615{
4616 if (!check)
4617 goto lock_used;
4618
4619 /*
4620 * If non-trylock use in a hardirq or softirq context, then
4621 * mark the lock as used in these contexts:
4622 */
4623 if (!hlock->trylock) {
4624 if (hlock->read) {
4625 if (lockdep_hardirq_context())
4626 if (!mark_lock(curr, hlock,
4627 LOCK_USED_IN_HARDIRQ_READ))
4628 return 0;
4629 if (curr->softirq_context)
4630 if (!mark_lock(curr, hlock,
4631 LOCK_USED_IN_SOFTIRQ_READ))
4632 return 0;
4633 } else {
4634 if (lockdep_hardirq_context())
4635 if (!mark_lock(curr, hlock, LOCK_USED_IN_HARDIRQ))
4636 return 0;
4637 if (curr->softirq_context)
4638 if (!mark_lock(curr, hlock, LOCK_USED_IN_SOFTIRQ))
4639 return 0;
4640 }
4641 }
4642
4643 /*
4644 * For lock_sync(), don't mark the ENABLED usage, since lock_sync()
4645 * creates no critical section and no extra dependency can be introduced
4646 * by interrupts
4647 */
4648 if (!hlock->hardirqs_off && !hlock->sync) {
4649 if (hlock->read) {
4650 if (!mark_lock(curr, hlock,
4651 LOCK_ENABLED_HARDIRQ_READ))
4652 return 0;
4653 if (curr->softirqs_enabled)
4654 if (!mark_lock(curr, hlock,
4655 LOCK_ENABLED_SOFTIRQ_READ))
4656 return 0;
4657 } else {
4658 if (!mark_lock(curr, hlock,
4659 LOCK_ENABLED_HARDIRQ))
4660 return 0;
4661 if (curr->softirqs_enabled)
4662 if (!mark_lock(curr, hlock,
4663 LOCK_ENABLED_SOFTIRQ))
4664 return 0;
4665 }
4666 }
4667
4668lock_used:
4669 /* mark it as used: */
4670 if (!mark_lock(curr, hlock, LOCK_USED))
4671 return 0;
4672
4673 return 1;
4674}
4675
4676static inline unsigned int task_irq_context(struct task_struct *task)
4677{
4678 return LOCK_CHAIN_HARDIRQ_CONTEXT * !!lockdep_hardirq_context() +
4679 LOCK_CHAIN_SOFTIRQ_CONTEXT * !!task->softirq_context;
4680}
4681
4682static int separate_irq_context(struct task_struct *curr,
4683 struct held_lock *hlock)
4684{
4685 unsigned int depth = curr->lockdep_depth;
4686
4687 /*
4688 * Keep track of points where we cross into an interrupt context:
4689 */
4690 if (depth) {
4691 struct held_lock *prev_hlock;
4692
4693 prev_hlock = curr->held_locks + depth-1;
4694 /*
4695 * If we cross into another context, reset the
4696 * hash key (this also prevents the checking and the
4697 * adding of the dependency to 'prev'):
4698 */
4699 if (prev_hlock->irq_context != hlock->irq_context)
4700 return 1;
4701 }
4702 return 0;
4703}
4704
4705/*
4706 * Mark a lock with a usage bit, and validate the state transition:
4707 */
4708static int mark_lock(struct task_struct *curr, struct held_lock *this,
4709 enum lock_usage_bit new_bit)
4710{
4711 unsigned int new_mask, ret = 1;
4712
4713 if (new_bit >= LOCK_USAGE_STATES) {
4714 DEBUG_LOCKS_WARN_ON(1);
4715 return 0;
4716 }
4717
4718 if (new_bit == LOCK_USED && this->read)
4719 new_bit = LOCK_USED_READ;
4720
4721 new_mask = 1 << new_bit;
4722
4723 /*
4724 * If already set then do not dirty the cacheline,
4725 * nor do any checks:
4726 */
4727 if (likely(hlock_class(this)->usage_mask & new_mask))
4728 return 1;
4729
4730 if (!graph_lock())
4731 return 0;
4732 /*
4733 * Make sure we didn't race:
4734 */
4735 if (unlikely(hlock_class(this)->usage_mask & new_mask))
4736 goto unlock;
4737
4738 if (!hlock_class(this)->usage_mask)
4739 debug_atomic_dec(nr_unused_locks);
4740
4741 hlock_class(this)->usage_mask |= new_mask;
4742
4743 if (new_bit < LOCK_TRACE_STATES) {
4744 if (!(hlock_class(this)->usage_traces[new_bit] = save_trace()))
4745 return 0;
4746 }
4747
4748 if (new_bit < LOCK_USED) {
4749 ret = mark_lock_irq(curr, this, new_bit);
4750 if (!ret)
4751 return 0;
4752 }
4753
4754unlock:
4755 graph_unlock();
4756
4757 /*
4758 * We must printk outside of the graph_lock:
4759 */
4760 if (ret == 2) {
4761 nbcon_cpu_emergency_enter();
4762 printk("\nmarked lock as {%s}:\n", usage_str[new_bit]);
4763 print_lock(this);
4764 print_irqtrace_events(curr);
4765 dump_stack();
4766 nbcon_cpu_emergency_exit();
4767 }
4768
4769 return ret;
4770}
4771
4772static inline short task_wait_context(struct task_struct *curr)
4773{
4774 /*
4775 * Set appropriate wait type for the context; for IRQs we have to take
4776 * into account force_irqthread as that is implied by PREEMPT_RT.
4777 */
4778 if (lockdep_hardirq_context()) {
4779 /*
4780 * Check if force_irqthreads will run us threaded.
4781 */
4782 if (curr->hardirq_threaded || curr->irq_config)
4783 return LD_WAIT_CONFIG;
4784
4785 return LD_WAIT_SPIN;
4786 } else if (curr->softirq_context) {
4787 /*
4788 * Softirqs are always threaded.
4789 */
4790 return LD_WAIT_CONFIG;
4791 }
4792
4793 return LD_WAIT_MAX;
4794}
4795
4796static int
4797print_lock_invalid_wait_context(struct task_struct *curr,
4798 struct held_lock *hlock)
4799{
4800 short curr_inner;
4801
4802 if (!debug_locks_off())
4803 return 0;
4804 if (debug_locks_silent)
4805 return 0;
4806
4807 nbcon_cpu_emergency_enter();
4808
4809 pr_warn("\n");
4810 pr_warn("=============================\n");
4811 pr_warn("[ BUG: Invalid wait context ]\n");
4812 print_kernel_ident();
4813 pr_warn("-----------------------------\n");
4814
4815 pr_warn("%s/%d is trying to lock:\n", curr->comm, task_pid_nr(curr));
4816 print_lock(hlock);
4817
4818 pr_warn("other info that might help us debug this:\n");
4819
4820 curr_inner = task_wait_context(curr);
4821 pr_warn("context-{%d:%d}\n", curr_inner, curr_inner);
4822
4823 lockdep_print_held_locks(curr);
4824
4825 pr_warn("stack backtrace:\n");
4826 dump_stack();
4827
4828 nbcon_cpu_emergency_exit();
4829
4830 return 0;
4831}
4832
4833/*
4834 * Verify the wait_type context.
4835 *
4836 * This check validates we take locks in the right wait-type order; that is it
4837 * ensures that we do not take mutexes inside spinlocks and do not attempt to
4838 * acquire spinlocks inside raw_spinlocks and the sort.
4839 *
4840 * The entire thing is slightly more complex because of RCU, RCU is a lock that
4841 * can be taken from (pretty much) any context but also has constraints.
4842 * However when taken in a stricter environment the RCU lock does not loosen
4843 * the constraints.
4844 *
4845 * Therefore we must look for the strictest environment in the lock stack and
4846 * compare that to the lock we're trying to acquire.
4847 */
4848static int check_wait_context(struct task_struct *curr, struct held_lock *next)
4849{
4850 u8 next_inner = hlock_class(next)->wait_type_inner;
4851 u8 next_outer = hlock_class(next)->wait_type_outer;
4852 u8 curr_inner;
4853 int depth;
4854
4855 if (!next_inner || next->trylock)
4856 return 0;
4857
4858 if (!next_outer)
4859 next_outer = next_inner;
4860
4861 /*
4862 * Find start of current irq_context..
4863 */
4864 for (depth = curr->lockdep_depth - 1; depth >= 0; depth--) {
4865 struct held_lock *prev = curr->held_locks + depth;
4866 if (prev->irq_context != next->irq_context)
4867 break;
4868 }
4869 depth++;
4870
4871 curr_inner = task_wait_context(curr);
4872
4873 for (; depth < curr->lockdep_depth; depth++) {
4874 struct held_lock *prev = curr->held_locks + depth;
4875 struct lock_class *class = hlock_class(prev);
4876 u8 prev_inner = class->wait_type_inner;
4877
4878 if (prev_inner) {
4879 /*
4880 * We can have a bigger inner than a previous one
4881 * when outer is smaller than inner, as with RCU.
4882 *
4883 * Also due to trylocks.
4884 */
4885 curr_inner = min(curr_inner, prev_inner);
4886
4887 /*
4888 * Allow override for annotations -- this is typically
4889 * only valid/needed for code that only exists when
4890 * CONFIG_PREEMPT_RT=n.
4891 */
4892 if (unlikely(class->lock_type == LD_LOCK_WAIT_OVERRIDE))
4893 curr_inner = prev_inner;
4894 }
4895 }
4896
4897 if (next_outer > curr_inner)
4898 return print_lock_invalid_wait_context(curr, next);
4899
4900 return 0;
4901}
4902
4903#else /* CONFIG_PROVE_LOCKING */
4904
4905static inline int
4906mark_usage(struct task_struct *curr, struct held_lock *hlock, int check)
4907{
4908 return 1;
4909}
4910
4911static inline unsigned int task_irq_context(struct task_struct *task)
4912{
4913 return 0;
4914}
4915
4916static inline int separate_irq_context(struct task_struct *curr,
4917 struct held_lock *hlock)
4918{
4919 return 0;
4920}
4921
4922static inline int check_wait_context(struct task_struct *curr,
4923 struct held_lock *next)
4924{
4925 return 0;
4926}
4927
4928#endif /* CONFIG_PROVE_LOCKING */
4929
4930/*
4931 * Initialize a lock instance's lock-class mapping info:
4932 */
4933void lockdep_init_map_type(struct lockdep_map *lock, const char *name,
4934 struct lock_class_key *key, int subclass,
4935 u8 inner, u8 outer, u8 lock_type)
4936{
4937 int i;
4938
4939 for (i = 0; i < NR_LOCKDEP_CACHING_CLASSES; i++)
4940 lock->class_cache[i] = NULL;
4941
4942#ifdef CONFIG_LOCK_STAT
4943 lock->cpu = raw_smp_processor_id();
4944#endif
4945
4946 /*
4947 * Can't be having no nameless bastards around this place!
4948 */
4949 if (DEBUG_LOCKS_WARN_ON(!name)) {
4950 lock->name = "NULL";
4951 return;
4952 }
4953
4954 lock->name = name;
4955
4956 lock->wait_type_outer = outer;
4957 lock->wait_type_inner = inner;
4958 lock->lock_type = lock_type;
4959
4960 /*
4961 * No key, no joy, we need to hash something.
4962 */
4963 if (DEBUG_LOCKS_WARN_ON(!key))
4964 return;
4965 /*
4966 * Sanity check, the lock-class key must either have been allocated
4967 * statically or must have been registered as a dynamic key.
4968 */
4969 if (!static_obj(key) && !is_dynamic_key(key)) {
4970 if (debug_locks)
4971 printk(KERN_ERR "BUG: key %px has not been registered!\n", key);
4972 DEBUG_LOCKS_WARN_ON(1);
4973 return;
4974 }
4975 lock->key = key;
4976
4977 if (unlikely(!debug_locks))
4978 return;
4979
4980 if (subclass) {
4981 unsigned long flags;
4982
4983 if (DEBUG_LOCKS_WARN_ON(!lockdep_enabled()))
4984 return;
4985
4986 raw_local_irq_save(flags);
4987 lockdep_recursion_inc();
4988 register_lock_class(lock, subclass, 1);
4989 lockdep_recursion_finish();
4990 raw_local_irq_restore(flags);
4991 }
4992}
4993EXPORT_SYMBOL_GPL(lockdep_init_map_type);
4994
4995struct lock_class_key __lockdep_no_validate__;
4996EXPORT_SYMBOL_GPL(__lockdep_no_validate__);
4997
4998struct lock_class_key __lockdep_no_track__;
4999EXPORT_SYMBOL_GPL(__lockdep_no_track__);
5000
5001#ifdef CONFIG_PROVE_LOCKING
5002void lockdep_set_lock_cmp_fn(struct lockdep_map *lock, lock_cmp_fn cmp_fn,
5003 lock_print_fn print_fn)
5004{
5005 struct lock_class *class = lock->class_cache[0];
5006 unsigned long flags;
5007
5008 raw_local_irq_save(flags);
5009 lockdep_recursion_inc();
5010
5011 if (!class)
5012 class = register_lock_class(lock, 0, 0);
5013
5014 if (class) {
5015 WARN_ON(class->cmp_fn && class->cmp_fn != cmp_fn);
5016 WARN_ON(class->print_fn && class->print_fn != print_fn);
5017
5018 class->cmp_fn = cmp_fn;
5019 class->print_fn = print_fn;
5020 }
5021
5022 lockdep_recursion_finish();
5023 raw_local_irq_restore(flags);
5024}
5025EXPORT_SYMBOL_GPL(lockdep_set_lock_cmp_fn);
5026#endif
5027
5028static void
5029print_lock_nested_lock_not_held(struct task_struct *curr,
5030 struct held_lock *hlock)
5031{
5032 if (!debug_locks_off())
5033 return;
5034 if (debug_locks_silent)
5035 return;
5036
5037 nbcon_cpu_emergency_enter();
5038
5039 pr_warn("\n");
5040 pr_warn("==================================\n");
5041 pr_warn("WARNING: Nested lock was not taken\n");
5042 print_kernel_ident();
5043 pr_warn("----------------------------------\n");
5044
5045 pr_warn("%s/%d is trying to lock:\n", curr->comm, task_pid_nr(curr));
5046 print_lock(hlock);
5047
5048 pr_warn("\nbut this task is not holding:\n");
5049 pr_warn("%s\n", hlock->nest_lock->name);
5050
5051 pr_warn("\nstack backtrace:\n");
5052 dump_stack();
5053
5054 pr_warn("\nother info that might help us debug this:\n");
5055 lockdep_print_held_locks(curr);
5056
5057 pr_warn("\nstack backtrace:\n");
5058 dump_stack();
5059
5060 nbcon_cpu_emergency_exit();
5061}
5062
5063static int __lock_is_held(const struct lockdep_map *lock, int read);
5064
5065/*
5066 * This gets called for every mutex_lock*()/spin_lock*() operation.
5067 * We maintain the dependency maps and validate the locking attempt:
5068 *
5069 * The callers must make sure that IRQs are disabled before calling it,
5070 * otherwise we could get an interrupt which would want to take locks,
5071 * which would end up in lockdep again.
5072 */
5073static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
5074 int trylock, int read, int check, int hardirqs_off,
5075 struct lockdep_map *nest_lock, unsigned long ip,
5076 int references, int pin_count, int sync)
5077{
5078 struct task_struct *curr = current;
5079 struct lock_class *class = NULL;
5080 struct held_lock *hlock;
5081 unsigned int depth;
5082 int chain_head = 0;
5083 int class_idx;
5084 u64 chain_key;
5085
5086 if (unlikely(!debug_locks))
5087 return 0;
5088
5089 if (unlikely(lock->key == &__lockdep_no_track__))
5090 return 0;
5091
5092 if (!prove_locking || lock->key == &__lockdep_no_validate__)
5093 check = 0;
5094
5095 if (subclass < NR_LOCKDEP_CACHING_CLASSES)
5096 class = lock->class_cache[subclass];
5097 /*
5098 * Not cached?
5099 */
5100 if (unlikely(!class)) {
5101 class = register_lock_class(lock, subclass, 0);
5102 if (!class)
5103 return 0;
5104 }
5105
5106 debug_class_ops_inc(class);
5107
5108 if (very_verbose(class)) {
5109 nbcon_cpu_emergency_enter();
5110 printk("\nacquire class [%px] %s", class->key, class->name);
5111 if (class->name_version > 1)
5112 printk(KERN_CONT "#%d", class->name_version);
5113 printk(KERN_CONT "\n");
5114 dump_stack();
5115 nbcon_cpu_emergency_exit();
5116 }
5117
5118 /*
5119 * Add the lock to the list of currently held locks.
5120 * (we dont increase the depth just yet, up until the
5121 * dependency checks are done)
5122 */
5123 depth = curr->lockdep_depth;
5124 /*
5125 * Ran out of static storage for our per-task lock stack again have we?
5126 */
5127 if (DEBUG_LOCKS_WARN_ON(depth >= MAX_LOCK_DEPTH))
5128 return 0;
5129
5130 class_idx = class - lock_classes;
5131
5132 if (depth && !sync) {
5133 /* we're holding locks and the new held lock is not a sync */
5134 hlock = curr->held_locks + depth - 1;
5135 if (hlock->class_idx == class_idx && nest_lock) {
5136 if (!references)
5137 references++;
5138
5139 if (!hlock->references)
5140 hlock->references++;
5141
5142 hlock->references += references;
5143
5144 /* Overflow */
5145 if (DEBUG_LOCKS_WARN_ON(hlock->references < references))
5146 return 0;
5147
5148 return 2;
5149 }
5150 }
5151
5152 hlock = curr->held_locks + depth;
5153 /*
5154 * Plain impossible, we just registered it and checked it weren't no
5155 * NULL like.. I bet this mushroom I ate was good!
5156 */
5157 if (DEBUG_LOCKS_WARN_ON(!class))
5158 return 0;
5159 hlock->class_idx = class_idx;
5160 hlock->acquire_ip = ip;
5161 hlock->instance = lock;
5162 hlock->nest_lock = nest_lock;
5163 hlock->irq_context = task_irq_context(curr);
5164 hlock->trylock = trylock;
5165 hlock->read = read;
5166 hlock->check = check;
5167 hlock->sync = !!sync;
5168 hlock->hardirqs_off = !!hardirqs_off;
5169 hlock->references = references;
5170#ifdef CONFIG_LOCK_STAT
5171 hlock->waittime_stamp = 0;
5172 hlock->holdtime_stamp = lockstat_clock();
5173#endif
5174 hlock->pin_count = pin_count;
5175
5176 if (check_wait_context(curr, hlock))
5177 return 0;
5178
5179 /* Initialize the lock usage bit */
5180 if (!mark_usage(curr, hlock, check))
5181 return 0;
5182
5183 /*
5184 * Calculate the chain hash: it's the combined hash of all the
5185 * lock keys along the dependency chain. We save the hash value
5186 * at every step so that we can get the current hash easily
5187 * after unlock. The chain hash is then used to cache dependency
5188 * results.
5189 *
5190 * The 'key ID' is what is the most compact key value to drive
5191 * the hash, not class->key.
5192 */
5193 /*
5194 * Whoops, we did it again.. class_idx is invalid.
5195 */
5196 if (DEBUG_LOCKS_WARN_ON(!test_bit(class_idx, lock_classes_in_use)))
5197 return 0;
5198
5199 chain_key = curr->curr_chain_key;
5200 if (!depth) {
5201 /*
5202 * How can we have a chain hash when we ain't got no keys?!
5203 */
5204 if (DEBUG_LOCKS_WARN_ON(chain_key != INITIAL_CHAIN_KEY))
5205 return 0;
5206 chain_head = 1;
5207 }
5208
5209 hlock->prev_chain_key = chain_key;
5210 if (separate_irq_context(curr, hlock)) {
5211 chain_key = INITIAL_CHAIN_KEY;
5212 chain_head = 1;
5213 }
5214 chain_key = iterate_chain_key(chain_key, hlock_id(hlock));
5215
5216 if (nest_lock && !__lock_is_held(nest_lock, -1)) {
5217 print_lock_nested_lock_not_held(curr, hlock);
5218 return 0;
5219 }
5220
5221 if (!debug_locks_silent) {
5222 WARN_ON_ONCE(depth && !hlock_class(hlock - 1)->key);
5223 WARN_ON_ONCE(!hlock_class(hlock)->key);
5224 }
5225
5226 if (!validate_chain(curr, hlock, chain_head, chain_key))
5227 return 0;
5228
5229 /* For lock_sync(), we are done here since no actual critical section */
5230 if (hlock->sync)
5231 return 1;
5232
5233 curr->curr_chain_key = chain_key;
5234 curr->lockdep_depth++;
5235 check_chain_key(curr);
5236#ifdef CONFIG_DEBUG_LOCKDEP
5237 if (unlikely(!debug_locks))
5238 return 0;
5239#endif
5240 if (unlikely(curr->lockdep_depth >= MAX_LOCK_DEPTH)) {
5241 debug_locks_off();
5242 nbcon_cpu_emergency_enter();
5243 print_lockdep_off("BUG: MAX_LOCK_DEPTH too low!");
5244 printk(KERN_DEBUG "depth: %i max: %lu!\n",
5245 curr->lockdep_depth, MAX_LOCK_DEPTH);
5246
5247 lockdep_print_held_locks(current);
5248 debug_show_all_locks();
5249 dump_stack();
5250 nbcon_cpu_emergency_exit();
5251
5252 return 0;
5253 }
5254
5255 if (unlikely(curr->lockdep_depth > max_lockdep_depth))
5256 max_lockdep_depth = curr->lockdep_depth;
5257
5258 return 1;
5259}
5260
5261static void print_unlock_imbalance_bug(struct task_struct *curr,
5262 struct lockdep_map *lock,
5263 unsigned long ip)
5264{
5265 if (!debug_locks_off())
5266 return;
5267 if (debug_locks_silent)
5268 return;
5269
5270 nbcon_cpu_emergency_enter();
5271
5272 pr_warn("\n");
5273 pr_warn("=====================================\n");
5274 pr_warn("WARNING: bad unlock balance detected!\n");
5275 print_kernel_ident();
5276 pr_warn("-------------------------------------\n");
5277 pr_warn("%s/%d is trying to release lock (",
5278 curr->comm, task_pid_nr(curr));
5279 print_lockdep_cache(lock);
5280 pr_cont(") at:\n");
5281 print_ip_sym(KERN_WARNING, ip);
5282 pr_warn("but there are no more locks to release!\n");
5283 pr_warn("\nother info that might help us debug this:\n");
5284 lockdep_print_held_locks(curr);
5285
5286 pr_warn("\nstack backtrace:\n");
5287 dump_stack();
5288
5289 nbcon_cpu_emergency_exit();
5290}
5291
5292static noinstr int match_held_lock(const struct held_lock *hlock,
5293 const struct lockdep_map *lock)
5294{
5295 if (hlock->instance == lock)
5296 return 1;
5297
5298 if (hlock->references) {
5299 const struct lock_class *class = lock->class_cache[0];
5300
5301 if (!class)
5302 class = look_up_lock_class(lock, 0);
5303
5304 /*
5305 * If look_up_lock_class() failed to find a class, we're trying
5306 * to test if we hold a lock that has never yet been acquired.
5307 * Clearly if the lock hasn't been acquired _ever_, we're not
5308 * holding it either, so report failure.
5309 */
5310 if (!class)
5311 return 0;
5312
5313 /*
5314 * References, but not a lock we're actually ref-counting?
5315 * State got messed up, follow the sites that change ->references
5316 * and try to make sense of it.
5317 */
5318 if (DEBUG_LOCKS_WARN_ON(!hlock->nest_lock))
5319 return 0;
5320
5321 if (hlock->class_idx == class - lock_classes)
5322 return 1;
5323 }
5324
5325 return 0;
5326}
5327
5328/* @depth must not be zero */
5329static struct held_lock *find_held_lock(struct task_struct *curr,
5330 struct lockdep_map *lock,
5331 unsigned int depth, int *idx)
5332{
5333 struct held_lock *ret, *hlock, *prev_hlock;
5334 int i;
5335
5336 i = depth - 1;
5337 hlock = curr->held_locks + i;
5338 ret = hlock;
5339 if (match_held_lock(hlock, lock))
5340 goto out;
5341
5342 ret = NULL;
5343 for (i--, prev_hlock = hlock--;
5344 i >= 0;
5345 i--, prev_hlock = hlock--) {
5346 /*
5347 * We must not cross into another context:
5348 */
5349 if (prev_hlock->irq_context != hlock->irq_context) {
5350 ret = NULL;
5351 break;
5352 }
5353 if (match_held_lock(hlock, lock)) {
5354 ret = hlock;
5355 break;
5356 }
5357 }
5358
5359out:
5360 *idx = i;
5361 return ret;
5362}
5363
5364static int reacquire_held_locks(struct task_struct *curr, unsigned int depth,
5365 int idx, unsigned int *merged)
5366{
5367 struct held_lock *hlock;
5368 int first_idx = idx;
5369
5370 if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
5371 return 0;
5372
5373 for (hlock = curr->held_locks + idx; idx < depth; idx++, hlock++) {
5374 switch (__lock_acquire(hlock->instance,
5375 hlock_class(hlock)->subclass,
5376 hlock->trylock,
5377 hlock->read, hlock->check,
5378 hlock->hardirqs_off,
5379 hlock->nest_lock, hlock->acquire_ip,
5380 hlock->references, hlock->pin_count, 0)) {
5381 case 0:
5382 return 1;
5383 case 1:
5384 break;
5385 case 2:
5386 *merged += (idx == first_idx);
5387 break;
5388 default:
5389 WARN_ON(1);
5390 return 0;
5391 }
5392 }
5393 return 0;
5394}
5395
5396static int
5397__lock_set_class(struct lockdep_map *lock, const char *name,
5398 struct lock_class_key *key, unsigned int subclass,
5399 unsigned long ip)
5400{
5401 struct task_struct *curr = current;
5402 unsigned int depth, merged = 0;
5403 struct held_lock *hlock;
5404 struct lock_class *class;
5405 int i;
5406
5407 if (unlikely(!debug_locks))
5408 return 0;
5409
5410 depth = curr->lockdep_depth;
5411 /*
5412 * This function is about (re)setting the class of a held lock,
5413 * yet we're not actually holding any locks. Naughty user!
5414 */
5415 if (DEBUG_LOCKS_WARN_ON(!depth))
5416 return 0;
5417
5418 hlock = find_held_lock(curr, lock, depth, &i);
5419 if (!hlock) {
5420 print_unlock_imbalance_bug(curr, lock, ip);
5421 return 0;
5422 }
5423
5424 lockdep_init_map_type(lock, name, key, 0,
5425 lock->wait_type_inner,
5426 lock->wait_type_outer,
5427 lock->lock_type);
5428 class = register_lock_class(lock, subclass, 0);
5429 hlock->class_idx = class - lock_classes;
5430
5431 curr->lockdep_depth = i;
5432 curr->curr_chain_key = hlock->prev_chain_key;
5433
5434 if (reacquire_held_locks(curr, depth, i, &merged))
5435 return 0;
5436
5437 /*
5438 * I took it apart and put it back together again, except now I have
5439 * these 'spare' parts.. where shall I put them.
5440 */
5441 if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - merged))
5442 return 0;
5443 return 1;
5444}
5445
5446static int __lock_downgrade(struct lockdep_map *lock, unsigned long ip)
5447{
5448 struct task_struct *curr = current;
5449 unsigned int depth, merged = 0;
5450 struct held_lock *hlock;
5451 int i;
5452
5453 if (unlikely(!debug_locks))
5454 return 0;
5455
5456 depth = curr->lockdep_depth;
5457 /*
5458 * This function is about (re)setting the class of a held lock,
5459 * yet we're not actually holding any locks. Naughty user!
5460 */
5461 if (DEBUG_LOCKS_WARN_ON(!depth))
5462 return 0;
5463
5464 hlock = find_held_lock(curr, lock, depth, &i);
5465 if (!hlock) {
5466 print_unlock_imbalance_bug(curr, lock, ip);
5467 return 0;
5468 }
5469
5470 curr->lockdep_depth = i;
5471 curr->curr_chain_key = hlock->prev_chain_key;
5472
5473 WARN(hlock->read, "downgrading a read lock");
5474 hlock->read = 1;
5475 hlock->acquire_ip = ip;
5476
5477 if (reacquire_held_locks(curr, depth, i, &merged))
5478 return 0;
5479
5480 /* Merging can't happen with unchanged classes.. */
5481 if (DEBUG_LOCKS_WARN_ON(merged))
5482 return 0;
5483
5484 /*
5485 * I took it apart and put it back together again, except now I have
5486 * these 'spare' parts.. where shall I put them.
5487 */
5488 if (DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth))
5489 return 0;
5490
5491 return 1;
5492}
5493
5494/*
5495 * Remove the lock from the list of currently held locks - this gets
5496 * called on mutex_unlock()/spin_unlock*() (or on a failed
5497 * mutex_lock_interruptible()).
5498 */
5499static int
5500__lock_release(struct lockdep_map *lock, unsigned long ip)
5501{
5502 struct task_struct *curr = current;
5503 unsigned int depth, merged = 1;
5504 struct held_lock *hlock;
5505 int i;
5506
5507 if (unlikely(!debug_locks))
5508 return 0;
5509
5510 depth = curr->lockdep_depth;
5511 /*
5512 * So we're all set to release this lock.. wait what lock? We don't
5513 * own any locks, you've been drinking again?
5514 */
5515 if (depth <= 0) {
5516 print_unlock_imbalance_bug(curr, lock, ip);
5517 return 0;
5518 }
5519
5520 /*
5521 * Check whether the lock exists in the current stack
5522 * of held locks:
5523 */
5524 hlock = find_held_lock(curr, lock, depth, &i);
5525 if (!hlock) {
5526 print_unlock_imbalance_bug(curr, lock, ip);
5527 return 0;
5528 }
5529
5530 if (hlock->instance == lock)
5531 lock_release_holdtime(hlock);
5532
5533 WARN(hlock->pin_count, "releasing a pinned lock\n");
5534
5535 if (hlock->references) {
5536 hlock->references--;
5537 if (hlock->references) {
5538 /*
5539 * We had, and after removing one, still have
5540 * references, the current lock stack is still
5541 * valid. We're done!
5542 */
5543 return 1;
5544 }
5545 }
5546
5547 /*
5548 * We have the right lock to unlock, 'hlock' points to it.
5549 * Now we remove it from the stack, and add back the other
5550 * entries (if any), recalculating the hash along the way:
5551 */
5552
5553 curr->lockdep_depth = i;
5554 curr->curr_chain_key = hlock->prev_chain_key;
5555
5556 /*
5557 * The most likely case is when the unlock is on the innermost
5558 * lock. In this case, we are done!
5559 */
5560 if (i == depth-1)
5561 return 1;
5562
5563 if (reacquire_held_locks(curr, depth, i + 1, &merged))
5564 return 0;
5565
5566 /*
5567 * We had N bottles of beer on the wall, we drank one, but now
5568 * there's not N-1 bottles of beer left on the wall...
5569 * Pouring two of the bottles together is acceptable.
5570 */
5571 DEBUG_LOCKS_WARN_ON(curr->lockdep_depth != depth - merged);
5572
5573 /*
5574 * Since reacquire_held_locks() would have called check_chain_key()
5575 * indirectly via __lock_acquire(), we don't need to do it again
5576 * on return.
5577 */
5578 return 0;
5579}
5580
5581static __always_inline
5582int __lock_is_held(const struct lockdep_map *lock, int read)
5583{
5584 struct task_struct *curr = current;
5585 int i;
5586
5587 for (i = 0; i < curr->lockdep_depth; i++) {
5588 struct held_lock *hlock = curr->held_locks + i;
5589
5590 if (match_held_lock(hlock, lock)) {
5591 if (read == -1 || !!hlock->read == read)
5592 return LOCK_STATE_HELD;
5593
5594 return LOCK_STATE_NOT_HELD;
5595 }
5596 }
5597
5598 return LOCK_STATE_NOT_HELD;
5599}
5600
5601static struct pin_cookie __lock_pin_lock(struct lockdep_map *lock)
5602{
5603 struct pin_cookie cookie = NIL_COOKIE;
5604 struct task_struct *curr = current;
5605 int i;
5606
5607 if (unlikely(!debug_locks))
5608 return cookie;
5609
5610 for (i = 0; i < curr->lockdep_depth; i++) {
5611 struct held_lock *hlock = curr->held_locks + i;
5612
5613 if (match_held_lock(hlock, lock)) {
5614 /*
5615 * Grab 16bits of randomness; this is sufficient to not
5616 * be guessable and still allows some pin nesting in
5617 * our u32 pin_count.
5618 */
5619 cookie.val = 1 + (sched_clock() & 0xffff);
5620 hlock->pin_count += cookie.val;
5621 return cookie;
5622 }
5623 }
5624
5625 WARN(1, "pinning an unheld lock\n");
5626 return cookie;
5627}
5628
5629static void __lock_repin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
5630{
5631 struct task_struct *curr = current;
5632 int i;
5633
5634 if (unlikely(!debug_locks))
5635 return;
5636
5637 for (i = 0; i < curr->lockdep_depth; i++) {
5638 struct held_lock *hlock = curr->held_locks + i;
5639
5640 if (match_held_lock(hlock, lock)) {
5641 hlock->pin_count += cookie.val;
5642 return;
5643 }
5644 }
5645
5646 WARN(1, "pinning an unheld lock\n");
5647}
5648
5649static void __lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
5650{
5651 struct task_struct *curr = current;
5652 int i;
5653
5654 if (unlikely(!debug_locks))
5655 return;
5656
5657 for (i = 0; i < curr->lockdep_depth; i++) {
5658 struct held_lock *hlock = curr->held_locks + i;
5659
5660 if (match_held_lock(hlock, lock)) {
5661 if (WARN(!hlock->pin_count, "unpinning an unpinned lock\n"))
5662 return;
5663
5664 hlock->pin_count -= cookie.val;
5665
5666 if (WARN((int)hlock->pin_count < 0, "pin count corrupted\n"))
5667 hlock->pin_count = 0;
5668
5669 return;
5670 }
5671 }
5672
5673 WARN(1, "unpinning an unheld lock\n");
5674}
5675
5676/*
5677 * Check whether we follow the irq-flags state precisely:
5678 */
5679static noinstr void check_flags(unsigned long flags)
5680{
5681#if defined(CONFIG_PROVE_LOCKING) && defined(CONFIG_DEBUG_LOCKDEP)
5682 if (!debug_locks)
5683 return;
5684
5685 /* Get the warning out.. */
5686 instrumentation_begin();
5687
5688 if (irqs_disabled_flags(flags)) {
5689 if (DEBUG_LOCKS_WARN_ON(lockdep_hardirqs_enabled())) {
5690 printk("possible reason: unannotated irqs-off.\n");
5691 }
5692 } else {
5693 if (DEBUG_LOCKS_WARN_ON(!lockdep_hardirqs_enabled())) {
5694 printk("possible reason: unannotated irqs-on.\n");
5695 }
5696 }
5697
5698#ifndef CONFIG_PREEMPT_RT
5699 /*
5700 * We dont accurately track softirq state in e.g.
5701 * hardirq contexts (such as on 4KSTACKS), so only
5702 * check if not in hardirq contexts:
5703 */
5704 if (!hardirq_count()) {
5705 if (softirq_count()) {
5706 /* like the above, but with softirqs */
5707 DEBUG_LOCKS_WARN_ON(current->softirqs_enabled);
5708 } else {
5709 /* lick the above, does it taste good? */
5710 DEBUG_LOCKS_WARN_ON(!current->softirqs_enabled);
5711 }
5712 }
5713#endif
5714
5715 if (!debug_locks)
5716 print_irqtrace_events(current);
5717
5718 instrumentation_end();
5719#endif
5720}
5721
5722void lock_set_class(struct lockdep_map *lock, const char *name,
5723 struct lock_class_key *key, unsigned int subclass,
5724 unsigned long ip)
5725{
5726 unsigned long flags;
5727
5728 if (unlikely(!lockdep_enabled()))
5729 return;
5730
5731 raw_local_irq_save(flags);
5732 lockdep_recursion_inc();
5733 check_flags(flags);
5734 if (__lock_set_class(lock, name, key, subclass, ip))
5735 check_chain_key(current);
5736 lockdep_recursion_finish();
5737 raw_local_irq_restore(flags);
5738}
5739EXPORT_SYMBOL_GPL(lock_set_class);
5740
5741void lock_downgrade(struct lockdep_map *lock, unsigned long ip)
5742{
5743 unsigned long flags;
5744
5745 if (unlikely(!lockdep_enabled()))
5746 return;
5747
5748 raw_local_irq_save(flags);
5749 lockdep_recursion_inc();
5750 check_flags(flags);
5751 if (__lock_downgrade(lock, ip))
5752 check_chain_key(current);
5753 lockdep_recursion_finish();
5754 raw_local_irq_restore(flags);
5755}
5756EXPORT_SYMBOL_GPL(lock_downgrade);
5757
5758/* NMI context !!! */
5759static void verify_lock_unused(struct lockdep_map *lock, struct held_lock *hlock, int subclass)
5760{
5761#ifdef CONFIG_PROVE_LOCKING
5762 struct lock_class *class = look_up_lock_class(lock, subclass);
5763 unsigned long mask = LOCKF_USED;
5764
5765 /* if it doesn't have a class (yet), it certainly hasn't been used yet */
5766 if (!class)
5767 return;
5768
5769 /*
5770 * READ locks only conflict with USED, such that if we only ever use
5771 * READ locks, there is no deadlock possible -- RCU.
5772 */
5773 if (!hlock->read)
5774 mask |= LOCKF_USED_READ;
5775
5776 if (!(class->usage_mask & mask))
5777 return;
5778
5779 hlock->class_idx = class - lock_classes;
5780
5781 print_usage_bug(current, hlock, LOCK_USED, LOCK_USAGE_STATES);
5782#endif
5783}
5784
5785static bool lockdep_nmi(void)
5786{
5787 if (raw_cpu_read(lockdep_recursion))
5788 return false;
5789
5790 if (!in_nmi())
5791 return false;
5792
5793 return true;
5794}
5795
5796/*
5797 * read_lock() is recursive if:
5798 * 1. We force lockdep think this way in selftests or
5799 * 2. The implementation is not queued read/write lock or
5800 * 3. The locker is at an in_interrupt() context.
5801 */
5802bool read_lock_is_recursive(void)
5803{
5804 return force_read_lock_recursive ||
5805 !IS_ENABLED(CONFIG_QUEUED_RWLOCKS) ||
5806 in_interrupt();
5807}
5808EXPORT_SYMBOL_GPL(read_lock_is_recursive);
5809
5810/*
5811 * We are not always called with irqs disabled - do that here,
5812 * and also avoid lockdep recursion:
5813 */
5814void lock_acquire(struct lockdep_map *lock, unsigned int subclass,
5815 int trylock, int read, int check,
5816 struct lockdep_map *nest_lock, unsigned long ip)
5817{
5818 unsigned long flags;
5819
5820 trace_lock_acquire(lock, subclass, trylock, read, check, nest_lock, ip);
5821
5822 if (!debug_locks)
5823 return;
5824
5825 if (unlikely(!lockdep_enabled())) {
5826 /* XXX allow trylock from NMI ?!? */
5827 if (lockdep_nmi() && !trylock) {
5828 struct held_lock hlock;
5829
5830 hlock.acquire_ip = ip;
5831 hlock.instance = lock;
5832 hlock.nest_lock = nest_lock;
5833 hlock.irq_context = 2; // XXX
5834 hlock.trylock = trylock;
5835 hlock.read = read;
5836 hlock.check = check;
5837 hlock.hardirqs_off = true;
5838 hlock.references = 0;
5839
5840 verify_lock_unused(lock, &hlock, subclass);
5841 }
5842 return;
5843 }
5844
5845 raw_local_irq_save(flags);
5846 check_flags(flags);
5847
5848 lockdep_recursion_inc();
5849 __lock_acquire(lock, subclass, trylock, read, check,
5850 irqs_disabled_flags(flags), nest_lock, ip, 0, 0, 0);
5851 lockdep_recursion_finish();
5852 raw_local_irq_restore(flags);
5853}
5854EXPORT_SYMBOL_GPL(lock_acquire);
5855
5856void lock_release(struct lockdep_map *lock, unsigned long ip)
5857{
5858 unsigned long flags;
5859
5860 trace_lock_release(lock, ip);
5861
5862 if (unlikely(!lockdep_enabled() ||
5863 lock->key == &__lockdep_no_track__))
5864 return;
5865
5866 raw_local_irq_save(flags);
5867 check_flags(flags);
5868
5869 lockdep_recursion_inc();
5870 if (__lock_release(lock, ip))
5871 check_chain_key(current);
5872 lockdep_recursion_finish();
5873 raw_local_irq_restore(flags);
5874}
5875EXPORT_SYMBOL_GPL(lock_release);
5876
5877/*
5878 * lock_sync() - A special annotation for synchronize_{s,}rcu()-like API.
5879 *
5880 * No actual critical section is created by the APIs annotated with this: these
5881 * APIs are used to wait for one or multiple critical sections (on other CPUs
5882 * or threads), and it means that calling these APIs inside these critical
5883 * sections is potential deadlock.
5884 */
5885void lock_sync(struct lockdep_map *lock, unsigned subclass, int read,
5886 int check, struct lockdep_map *nest_lock, unsigned long ip)
5887{
5888 unsigned long flags;
5889
5890 if (unlikely(!lockdep_enabled()))
5891 return;
5892
5893 raw_local_irq_save(flags);
5894 check_flags(flags);
5895
5896 lockdep_recursion_inc();
5897 __lock_acquire(lock, subclass, 0, read, check,
5898 irqs_disabled_flags(flags), nest_lock, ip, 0, 0, 1);
5899 check_chain_key(current);
5900 lockdep_recursion_finish();
5901 raw_local_irq_restore(flags);
5902}
5903EXPORT_SYMBOL_GPL(lock_sync);
5904
5905noinstr int lock_is_held_type(const struct lockdep_map *lock, int read)
5906{
5907 unsigned long flags;
5908 int ret = LOCK_STATE_NOT_HELD;
5909
5910 /*
5911 * Avoid false negative lockdep_assert_held() and
5912 * lockdep_assert_not_held().
5913 */
5914 if (unlikely(!lockdep_enabled()))
5915 return LOCK_STATE_UNKNOWN;
5916
5917 raw_local_irq_save(flags);
5918 check_flags(flags);
5919
5920 lockdep_recursion_inc();
5921 ret = __lock_is_held(lock, read);
5922 lockdep_recursion_finish();
5923 raw_local_irq_restore(flags);
5924
5925 return ret;
5926}
5927EXPORT_SYMBOL_GPL(lock_is_held_type);
5928NOKPROBE_SYMBOL(lock_is_held_type);
5929
5930struct pin_cookie lock_pin_lock(struct lockdep_map *lock)
5931{
5932 struct pin_cookie cookie = NIL_COOKIE;
5933 unsigned long flags;
5934
5935 if (unlikely(!lockdep_enabled()))
5936 return cookie;
5937
5938 raw_local_irq_save(flags);
5939 check_flags(flags);
5940
5941 lockdep_recursion_inc();
5942 cookie = __lock_pin_lock(lock);
5943 lockdep_recursion_finish();
5944 raw_local_irq_restore(flags);
5945
5946 return cookie;
5947}
5948EXPORT_SYMBOL_GPL(lock_pin_lock);
5949
5950void lock_repin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
5951{
5952 unsigned long flags;
5953
5954 if (unlikely(!lockdep_enabled()))
5955 return;
5956
5957 raw_local_irq_save(flags);
5958 check_flags(flags);
5959
5960 lockdep_recursion_inc();
5961 __lock_repin_lock(lock, cookie);
5962 lockdep_recursion_finish();
5963 raw_local_irq_restore(flags);
5964}
5965EXPORT_SYMBOL_GPL(lock_repin_lock);
5966
5967void lock_unpin_lock(struct lockdep_map *lock, struct pin_cookie cookie)
5968{
5969 unsigned long flags;
5970
5971 if (unlikely(!lockdep_enabled()))
5972 return;
5973
5974 raw_local_irq_save(flags);
5975 check_flags(flags);
5976
5977 lockdep_recursion_inc();
5978 __lock_unpin_lock(lock, cookie);
5979 lockdep_recursion_finish();
5980 raw_local_irq_restore(flags);
5981}
5982EXPORT_SYMBOL_GPL(lock_unpin_lock);
5983
5984#ifdef CONFIG_LOCK_STAT
5985static void print_lock_contention_bug(struct task_struct *curr,
5986 struct lockdep_map *lock,
5987 unsigned long ip)
5988{
5989 if (!debug_locks_off())
5990 return;
5991 if (debug_locks_silent)
5992 return;
5993
5994 nbcon_cpu_emergency_enter();
5995
5996 pr_warn("\n");
5997 pr_warn("=================================\n");
5998 pr_warn("WARNING: bad contention detected!\n");
5999 print_kernel_ident();
6000 pr_warn("---------------------------------\n");
6001 pr_warn("%s/%d is trying to contend lock (",
6002 curr->comm, task_pid_nr(curr));
6003 print_lockdep_cache(lock);
6004 pr_cont(") at:\n");
6005 print_ip_sym(KERN_WARNING, ip);
6006 pr_warn("but there are no locks held!\n");
6007 pr_warn("\nother info that might help us debug this:\n");
6008 lockdep_print_held_locks(curr);
6009
6010 pr_warn("\nstack backtrace:\n");
6011 dump_stack();
6012
6013 nbcon_cpu_emergency_exit();
6014}
6015
6016static void
6017__lock_contended(struct lockdep_map *lock, unsigned long ip)
6018{
6019 struct task_struct *curr = current;
6020 struct held_lock *hlock;
6021 struct lock_class_stats *stats;
6022 unsigned int depth;
6023 int i, contention_point, contending_point;
6024
6025 depth = curr->lockdep_depth;
6026 /*
6027 * Whee, we contended on this lock, except it seems we're not
6028 * actually trying to acquire anything much at all..
6029 */
6030 if (DEBUG_LOCKS_WARN_ON(!depth))
6031 return;
6032
6033 if (unlikely(lock->key == &__lockdep_no_track__))
6034 return;
6035
6036 hlock = find_held_lock(curr, lock, depth, &i);
6037 if (!hlock) {
6038 print_lock_contention_bug(curr, lock, ip);
6039 return;
6040 }
6041
6042 if (hlock->instance != lock)
6043 return;
6044
6045 hlock->waittime_stamp = lockstat_clock();
6046
6047 contention_point = lock_point(hlock_class(hlock)->contention_point, ip);
6048 contending_point = lock_point(hlock_class(hlock)->contending_point,
6049 lock->ip);
6050
6051 stats = get_lock_stats(hlock_class(hlock));
6052 if (contention_point < LOCKSTAT_POINTS)
6053 stats->contention_point[contention_point]++;
6054 if (contending_point < LOCKSTAT_POINTS)
6055 stats->contending_point[contending_point]++;
6056 if (lock->cpu != smp_processor_id())
6057 stats->bounces[bounce_contended + !!hlock->read]++;
6058}
6059
6060static void
6061__lock_acquired(struct lockdep_map *lock, unsigned long ip)
6062{
6063 struct task_struct *curr = current;
6064 struct held_lock *hlock;
6065 struct lock_class_stats *stats;
6066 unsigned int depth;
6067 u64 now, waittime = 0;
6068 int i, cpu;
6069
6070 depth = curr->lockdep_depth;
6071 /*
6072 * Yay, we acquired ownership of this lock we didn't try to
6073 * acquire, how the heck did that happen?
6074 */
6075 if (DEBUG_LOCKS_WARN_ON(!depth))
6076 return;
6077
6078 if (unlikely(lock->key == &__lockdep_no_track__))
6079 return;
6080
6081 hlock = find_held_lock(curr, lock, depth, &i);
6082 if (!hlock) {
6083 print_lock_contention_bug(curr, lock, _RET_IP_);
6084 return;
6085 }
6086
6087 if (hlock->instance != lock)
6088 return;
6089
6090 cpu = smp_processor_id();
6091 if (hlock->waittime_stamp) {
6092 now = lockstat_clock();
6093 waittime = now - hlock->waittime_stamp;
6094 hlock->holdtime_stamp = now;
6095 }
6096
6097 stats = get_lock_stats(hlock_class(hlock));
6098 if (waittime) {
6099 if (hlock->read)
6100 lock_time_inc(&stats->read_waittime, waittime);
6101 else
6102 lock_time_inc(&stats->write_waittime, waittime);
6103 }
6104 if (lock->cpu != cpu)
6105 stats->bounces[bounce_acquired + !!hlock->read]++;
6106
6107 lock->cpu = cpu;
6108 lock->ip = ip;
6109}
6110
6111void lock_contended(struct lockdep_map *lock, unsigned long ip)
6112{
6113 unsigned long flags;
6114
6115 trace_lock_contended(lock, ip);
6116
6117 if (unlikely(!lock_stat || !lockdep_enabled()))
6118 return;
6119
6120 raw_local_irq_save(flags);
6121 check_flags(flags);
6122 lockdep_recursion_inc();
6123 __lock_contended(lock, ip);
6124 lockdep_recursion_finish();
6125 raw_local_irq_restore(flags);
6126}
6127EXPORT_SYMBOL_GPL(lock_contended);
6128
6129void lock_acquired(struct lockdep_map *lock, unsigned long ip)
6130{
6131 unsigned long flags;
6132
6133 trace_lock_acquired(lock, ip);
6134
6135 if (unlikely(!lock_stat || !lockdep_enabled()))
6136 return;
6137
6138 raw_local_irq_save(flags);
6139 check_flags(flags);
6140 lockdep_recursion_inc();
6141 __lock_acquired(lock, ip);
6142 lockdep_recursion_finish();
6143 raw_local_irq_restore(flags);
6144}
6145EXPORT_SYMBOL_GPL(lock_acquired);
6146#endif
6147
6148/*
6149 * Used by the testsuite, sanitize the validator state
6150 * after a simulated failure:
6151 */
6152
6153void lockdep_reset(void)
6154{
6155 unsigned long flags;
6156 int i;
6157
6158 raw_local_irq_save(flags);
6159 lockdep_init_task(current);
6160 memset(current->held_locks, 0, MAX_LOCK_DEPTH*sizeof(struct held_lock));
6161 nr_hardirq_chains = 0;
6162 nr_softirq_chains = 0;
6163 nr_process_chains = 0;
6164 debug_locks = 1;
6165 for (i = 0; i < CHAINHASH_SIZE; i++)
6166 INIT_HLIST_HEAD(chainhash_table + i);
6167 raw_local_irq_restore(flags);
6168}
6169
6170/* Remove a class from a lock chain. Must be called with the graph lock held. */
6171static void remove_class_from_lock_chain(struct pending_free *pf,
6172 struct lock_chain *chain,
6173 struct lock_class *class)
6174{
6175#ifdef CONFIG_PROVE_LOCKING
6176 int i;
6177
6178 for (i = chain->base; i < chain->base + chain->depth; i++) {
6179 if (chain_hlock_class_idx(chain_hlocks[i]) != class - lock_classes)
6180 continue;
6181 /*
6182 * Each lock class occurs at most once in a lock chain so once
6183 * we found a match we can break out of this loop.
6184 */
6185 goto free_lock_chain;
6186 }
6187 /* Since the chain has not been modified, return. */
6188 return;
6189
6190free_lock_chain:
6191 free_chain_hlocks(chain->base, chain->depth);
6192 /* Overwrite the chain key for concurrent RCU readers. */
6193 WRITE_ONCE(chain->chain_key, INITIAL_CHAIN_KEY);
6194 dec_chains(chain->irq_context);
6195
6196 /*
6197 * Note: calling hlist_del_rcu() from inside a
6198 * hlist_for_each_entry_rcu() loop is safe.
6199 */
6200 hlist_del_rcu(&chain->entry);
6201 __set_bit(chain - lock_chains, pf->lock_chains_being_freed);
6202 nr_zapped_lock_chains++;
6203#endif
6204}
6205
6206/* Must be called with the graph lock held. */
6207static void remove_class_from_lock_chains(struct pending_free *pf,
6208 struct lock_class *class)
6209{
6210 struct lock_chain *chain;
6211 struct hlist_head *head;
6212 int i;
6213
6214 for (i = 0; i < ARRAY_SIZE(chainhash_table); i++) {
6215 head = chainhash_table + i;
6216 hlist_for_each_entry_rcu(chain, head, entry) {
6217 remove_class_from_lock_chain(pf, chain, class);
6218 }
6219 }
6220}
6221
6222/*
6223 * Remove all references to a lock class. The caller must hold the graph lock.
6224 */
6225static void zap_class(struct pending_free *pf, struct lock_class *class)
6226{
6227 struct lock_list *entry;
6228 int i;
6229
6230 WARN_ON_ONCE(!class->key);
6231
6232 /*
6233 * Remove all dependencies this lock is
6234 * involved in:
6235 */
6236 for_each_set_bit(i, list_entries_in_use, ARRAY_SIZE(list_entries)) {
6237 entry = list_entries + i;
6238 if (entry->class != class && entry->links_to != class)
6239 continue;
6240 __clear_bit(i, list_entries_in_use);
6241 nr_list_entries--;
6242 list_del_rcu(&entry->entry);
6243 }
6244 if (list_empty(&class->locks_after) &&
6245 list_empty(&class->locks_before)) {
6246 list_move_tail(&class->lock_entry, &pf->zapped);
6247 hlist_del_rcu(&class->hash_entry);
6248 WRITE_ONCE(class->key, NULL);
6249 WRITE_ONCE(class->name, NULL);
6250 nr_lock_classes--;
6251 __clear_bit(class - lock_classes, lock_classes_in_use);
6252 if (class - lock_classes == max_lock_class_idx)
6253 max_lock_class_idx--;
6254 } else {
6255 WARN_ONCE(true, "%s() failed for class %s\n", __func__,
6256 class->name);
6257 }
6258
6259 remove_class_from_lock_chains(pf, class);
6260 nr_zapped_classes++;
6261}
6262
6263static void reinit_class(struct lock_class *class)
6264{
6265 WARN_ON_ONCE(!class->lock_entry.next);
6266 WARN_ON_ONCE(!list_empty(&class->locks_after));
6267 WARN_ON_ONCE(!list_empty(&class->locks_before));
6268 memset_startat(class, 0, key);
6269 WARN_ON_ONCE(!class->lock_entry.next);
6270 WARN_ON_ONCE(!list_empty(&class->locks_after));
6271 WARN_ON_ONCE(!list_empty(&class->locks_before));
6272}
6273
6274static inline int within(const void *addr, void *start, unsigned long size)
6275{
6276 return addr >= start && addr < start + size;
6277}
6278
6279static bool inside_selftest(void)
6280{
6281 return current == lockdep_selftest_task_struct;
6282}
6283
6284/* The caller must hold the graph lock. */
6285static struct pending_free *get_pending_free(void)
6286{
6287 return delayed_free.pf + delayed_free.index;
6288}
6289
6290static void free_zapped_rcu(struct rcu_head *cb);
6291
6292/*
6293* See if we need to queue an RCU callback, must called with
6294* the lockdep lock held, returns false if either we don't have
6295* any pending free or the callback is already scheduled.
6296* Otherwise, a call_rcu() must follow this function call.
6297*/
6298static bool prepare_call_rcu_zapped(struct pending_free *pf)
6299{
6300 WARN_ON_ONCE(inside_selftest());
6301
6302 if (list_empty(&pf->zapped))
6303 return false;
6304
6305 if (delayed_free.scheduled)
6306 return false;
6307
6308 delayed_free.scheduled = true;
6309
6310 WARN_ON_ONCE(delayed_free.pf + delayed_free.index != pf);
6311 delayed_free.index ^= 1;
6312
6313 return true;
6314}
6315
6316/* The caller must hold the graph lock. May be called from RCU context. */
6317static void __free_zapped_classes(struct pending_free *pf)
6318{
6319 struct lock_class *class;
6320
6321 check_data_structures();
6322
6323 list_for_each_entry(class, &pf->zapped, lock_entry)
6324 reinit_class(class);
6325
6326 list_splice_init(&pf->zapped, &free_lock_classes);
6327
6328#ifdef CONFIG_PROVE_LOCKING
6329 bitmap_andnot(lock_chains_in_use, lock_chains_in_use,
6330 pf->lock_chains_being_freed, ARRAY_SIZE(lock_chains));
6331 bitmap_clear(pf->lock_chains_being_freed, 0, ARRAY_SIZE(lock_chains));
6332#endif
6333}
6334
6335static void free_zapped_rcu(struct rcu_head *ch)
6336{
6337 struct pending_free *pf;
6338 unsigned long flags;
6339 bool need_callback;
6340
6341 if (WARN_ON_ONCE(ch != &delayed_free.rcu_head))
6342 return;
6343
6344 raw_local_irq_save(flags);
6345 lockdep_lock();
6346
6347 /* closed head */
6348 pf = delayed_free.pf + (delayed_free.index ^ 1);
6349 __free_zapped_classes(pf);
6350 delayed_free.scheduled = false;
6351 need_callback =
6352 prepare_call_rcu_zapped(delayed_free.pf + delayed_free.index);
6353 lockdep_unlock();
6354 raw_local_irq_restore(flags);
6355
6356 /*
6357 * If there's pending free and its callback has not been scheduled,
6358 * queue an RCU callback.
6359 */
6360 if (need_callback)
6361 call_rcu(&delayed_free.rcu_head, free_zapped_rcu);
6362
6363}
6364
6365/*
6366 * Remove all lock classes from the class hash table and from the
6367 * all_lock_classes list whose key or name is in the address range [start,
6368 * start + size). Move these lock classes to the zapped_classes list. Must
6369 * be called with the graph lock held.
6370 */
6371static void __lockdep_free_key_range(struct pending_free *pf, void *start,
6372 unsigned long size)
6373{
6374 struct lock_class *class;
6375 struct hlist_head *head;
6376 int i;
6377
6378 /* Unhash all classes that were created by a module. */
6379 for (i = 0; i < CLASSHASH_SIZE; i++) {
6380 head = classhash_table + i;
6381 hlist_for_each_entry_rcu(class, head, hash_entry) {
6382 if (!within(class->key, start, size) &&
6383 !within(class->name, start, size))
6384 continue;
6385 zap_class(pf, class);
6386 }
6387 }
6388}
6389
6390/*
6391 * Used in module.c to remove lock classes from memory that is going to be
6392 * freed; and possibly re-used by other modules.
6393 *
6394 * We will have had one synchronize_rcu() before getting here, so we're
6395 * guaranteed nobody will look up these exact classes -- they're properly dead
6396 * but still allocated.
6397 */
6398static void lockdep_free_key_range_reg(void *start, unsigned long size)
6399{
6400 struct pending_free *pf;
6401 unsigned long flags;
6402 bool need_callback;
6403
6404 init_data_structures_once();
6405
6406 raw_local_irq_save(flags);
6407 lockdep_lock();
6408 pf = get_pending_free();
6409 __lockdep_free_key_range(pf, start, size);
6410 need_callback = prepare_call_rcu_zapped(pf);
6411 lockdep_unlock();
6412 raw_local_irq_restore(flags);
6413 if (need_callback)
6414 call_rcu(&delayed_free.rcu_head, free_zapped_rcu);
6415 /*
6416 * Wait for any possible iterators from look_up_lock_class() to pass
6417 * before continuing to free the memory they refer to.
6418 */
6419 synchronize_rcu();
6420}
6421
6422/*
6423 * Free all lockdep keys in the range [start, start+size). Does not sleep.
6424 * Ignores debug_locks. Must only be used by the lockdep selftests.
6425 */
6426static void lockdep_free_key_range_imm(void *start, unsigned long size)
6427{
6428 struct pending_free *pf = delayed_free.pf;
6429 unsigned long flags;
6430
6431 init_data_structures_once();
6432
6433 raw_local_irq_save(flags);
6434 lockdep_lock();
6435 __lockdep_free_key_range(pf, start, size);
6436 __free_zapped_classes(pf);
6437 lockdep_unlock();
6438 raw_local_irq_restore(flags);
6439}
6440
6441void lockdep_free_key_range(void *start, unsigned long size)
6442{
6443 init_data_structures_once();
6444
6445 if (inside_selftest())
6446 lockdep_free_key_range_imm(start, size);
6447 else
6448 lockdep_free_key_range_reg(start, size);
6449}
6450
6451/*
6452 * Check whether any element of the @lock->class_cache[] array refers to a
6453 * registered lock class. The caller must hold either the graph lock or the
6454 * RCU read lock.
6455 */
6456static bool lock_class_cache_is_registered(struct lockdep_map *lock)
6457{
6458 struct lock_class *class;
6459 struct hlist_head *head;
6460 int i, j;
6461
6462 for (i = 0; i < CLASSHASH_SIZE; i++) {
6463 head = classhash_table + i;
6464 hlist_for_each_entry_rcu(class, head, hash_entry) {
6465 for (j = 0; j < NR_LOCKDEP_CACHING_CLASSES; j++)
6466 if (lock->class_cache[j] == class)
6467 return true;
6468 }
6469 }
6470 return false;
6471}
6472
6473/* The caller must hold the graph lock. Does not sleep. */
6474static void __lockdep_reset_lock(struct pending_free *pf,
6475 struct lockdep_map *lock)
6476{
6477 struct lock_class *class;
6478 int j;
6479
6480 /*
6481 * Remove all classes this lock might have:
6482 */
6483 for (j = 0; j < MAX_LOCKDEP_SUBCLASSES; j++) {
6484 /*
6485 * If the class exists we look it up and zap it:
6486 */
6487 class = look_up_lock_class(lock, j);
6488 if (class)
6489 zap_class(pf, class);
6490 }
6491 /*
6492 * Debug check: in the end all mapped classes should
6493 * be gone.
6494 */
6495 if (WARN_ON_ONCE(lock_class_cache_is_registered(lock)))
6496 debug_locks_off();
6497}
6498
6499/*
6500 * Remove all information lockdep has about a lock if debug_locks == 1. Free
6501 * released data structures from RCU context.
6502 */
6503static void lockdep_reset_lock_reg(struct lockdep_map *lock)
6504{
6505 struct pending_free *pf;
6506 unsigned long flags;
6507 int locked;
6508 bool need_callback = false;
6509
6510 raw_local_irq_save(flags);
6511 locked = graph_lock();
6512 if (!locked)
6513 goto out_irq;
6514
6515 pf = get_pending_free();
6516 __lockdep_reset_lock(pf, lock);
6517 need_callback = prepare_call_rcu_zapped(pf);
6518
6519 graph_unlock();
6520out_irq:
6521 raw_local_irq_restore(flags);
6522 if (need_callback)
6523 call_rcu(&delayed_free.rcu_head, free_zapped_rcu);
6524}
6525
6526/*
6527 * Reset a lock. Does not sleep. Ignores debug_locks. Must only be used by the
6528 * lockdep selftests.
6529 */
6530static void lockdep_reset_lock_imm(struct lockdep_map *lock)
6531{
6532 struct pending_free *pf = delayed_free.pf;
6533 unsigned long flags;
6534
6535 raw_local_irq_save(flags);
6536 lockdep_lock();
6537 __lockdep_reset_lock(pf, lock);
6538 __free_zapped_classes(pf);
6539 lockdep_unlock();
6540 raw_local_irq_restore(flags);
6541}
6542
6543void lockdep_reset_lock(struct lockdep_map *lock)
6544{
6545 init_data_structures_once();
6546
6547 if (inside_selftest())
6548 lockdep_reset_lock_imm(lock);
6549 else
6550 lockdep_reset_lock_reg(lock);
6551}
6552
6553/*
6554 * Unregister a dynamically allocated key.
6555 *
6556 * Unlike lockdep_register_key(), a search is always done to find a matching
6557 * key irrespective of debug_locks to avoid potential invalid access to freed
6558 * memory in lock_class entry.
6559 */
6560void lockdep_unregister_key(struct lock_class_key *key)
6561{
6562 struct hlist_head *hash_head = keyhashentry(key);
6563 struct lock_class_key *k;
6564 struct pending_free *pf;
6565 unsigned long flags;
6566 bool found = false;
6567 bool need_callback = false;
6568
6569 might_sleep();
6570
6571 if (WARN_ON_ONCE(static_obj(key)))
6572 return;
6573
6574 raw_local_irq_save(flags);
6575 lockdep_lock();
6576
6577 hlist_for_each_entry_rcu(k, hash_head, hash_entry) {
6578 if (k == key) {
6579 hlist_del_rcu(&k->hash_entry);
6580 found = true;
6581 break;
6582 }
6583 }
6584 WARN_ON_ONCE(!found && debug_locks);
6585 if (found) {
6586 pf = get_pending_free();
6587 __lockdep_free_key_range(pf, key, 1);
6588 need_callback = prepare_call_rcu_zapped(pf);
6589 }
6590 lockdep_unlock();
6591 raw_local_irq_restore(flags);
6592
6593 if (need_callback)
6594 call_rcu(&delayed_free.rcu_head, free_zapped_rcu);
6595
6596 /* Wait until is_dynamic_key() has finished accessing k->hash_entry. */
6597 synchronize_rcu();
6598}
6599EXPORT_SYMBOL_GPL(lockdep_unregister_key);
6600
6601void __init lockdep_init(void)
6602{
6603 pr_info("Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar\n");
6604
6605 pr_info("... MAX_LOCKDEP_SUBCLASSES: %lu\n", MAX_LOCKDEP_SUBCLASSES);
6606 pr_info("... MAX_LOCK_DEPTH: %lu\n", MAX_LOCK_DEPTH);
6607 pr_info("... MAX_LOCKDEP_KEYS: %lu\n", MAX_LOCKDEP_KEYS);
6608 pr_info("... CLASSHASH_SIZE: %lu\n", CLASSHASH_SIZE);
6609 pr_info("... MAX_LOCKDEP_ENTRIES: %lu\n", MAX_LOCKDEP_ENTRIES);
6610 pr_info("... MAX_LOCKDEP_CHAINS: %lu\n", MAX_LOCKDEP_CHAINS);
6611 pr_info("... CHAINHASH_SIZE: %lu\n", CHAINHASH_SIZE);
6612
6613 pr_info(" memory used by lock dependency info: %zu kB\n",
6614 (sizeof(lock_classes) +
6615 sizeof(lock_classes_in_use) +
6616 sizeof(classhash_table) +
6617 sizeof(list_entries) +
6618 sizeof(list_entries_in_use) +
6619 sizeof(chainhash_table) +
6620 sizeof(delayed_free)
6621#ifdef CONFIG_PROVE_LOCKING
6622 + sizeof(lock_cq)
6623 + sizeof(lock_chains)
6624 + sizeof(lock_chains_in_use)
6625 + sizeof(chain_hlocks)
6626#endif
6627 ) / 1024
6628 );
6629
6630#if defined(CONFIG_TRACE_IRQFLAGS) && defined(CONFIG_PROVE_LOCKING)
6631 pr_info(" memory used for stack traces: %zu kB\n",
6632 (sizeof(stack_trace) + sizeof(stack_trace_hash)) / 1024
6633 );
6634#endif
6635
6636 pr_info(" per task-struct memory footprint: %zu bytes\n",
6637 sizeof(((struct task_struct *)NULL)->held_locks));
6638}
6639
6640static void
6641print_freed_lock_bug(struct task_struct *curr, const void *mem_from,
6642 const void *mem_to, struct held_lock *hlock)
6643{
6644 if (!debug_locks_off())
6645 return;
6646 if (debug_locks_silent)
6647 return;
6648
6649 nbcon_cpu_emergency_enter();
6650
6651 pr_warn("\n");
6652 pr_warn("=========================\n");
6653 pr_warn("WARNING: held lock freed!\n");
6654 print_kernel_ident();
6655 pr_warn("-------------------------\n");
6656 pr_warn("%s/%d is freeing memory %px-%px, with a lock still held there!\n",
6657 curr->comm, task_pid_nr(curr), mem_from, mem_to-1);
6658 print_lock(hlock);
6659 lockdep_print_held_locks(curr);
6660
6661 pr_warn("\nstack backtrace:\n");
6662 dump_stack();
6663
6664 nbcon_cpu_emergency_exit();
6665}
6666
6667static inline int not_in_range(const void* mem_from, unsigned long mem_len,
6668 const void* lock_from, unsigned long lock_len)
6669{
6670 return lock_from + lock_len <= mem_from ||
6671 mem_from + mem_len <= lock_from;
6672}
6673
6674/*
6675 * Called when kernel memory is freed (or unmapped), or if a lock
6676 * is destroyed or reinitialized - this code checks whether there is
6677 * any held lock in the memory range of <from> to <to>:
6678 */
6679void debug_check_no_locks_freed(const void *mem_from, unsigned long mem_len)
6680{
6681 struct task_struct *curr = current;
6682 struct held_lock *hlock;
6683 unsigned long flags;
6684 int i;
6685
6686 if (unlikely(!debug_locks))
6687 return;
6688
6689 raw_local_irq_save(flags);
6690 for (i = 0; i < curr->lockdep_depth; i++) {
6691 hlock = curr->held_locks + i;
6692
6693 if (not_in_range(mem_from, mem_len, hlock->instance,
6694 sizeof(*hlock->instance)))
6695 continue;
6696
6697 print_freed_lock_bug(curr, mem_from, mem_from + mem_len, hlock);
6698 break;
6699 }
6700 raw_local_irq_restore(flags);
6701}
6702EXPORT_SYMBOL_GPL(debug_check_no_locks_freed);
6703
6704static void print_held_locks_bug(void)
6705{
6706 if (!debug_locks_off())
6707 return;
6708 if (debug_locks_silent)
6709 return;
6710
6711 nbcon_cpu_emergency_enter();
6712
6713 pr_warn("\n");
6714 pr_warn("====================================\n");
6715 pr_warn("WARNING: %s/%d still has locks held!\n",
6716 current->comm, task_pid_nr(current));
6717 print_kernel_ident();
6718 pr_warn("------------------------------------\n");
6719 lockdep_print_held_locks(current);
6720 pr_warn("\nstack backtrace:\n");
6721 dump_stack();
6722
6723 nbcon_cpu_emergency_exit();
6724}
6725
6726void debug_check_no_locks_held(void)
6727{
6728 if (unlikely(current->lockdep_depth > 0))
6729 print_held_locks_bug();
6730}
6731EXPORT_SYMBOL_GPL(debug_check_no_locks_held);
6732
6733#ifdef __KERNEL__
6734void debug_show_all_locks(void)
6735{
6736 struct task_struct *g, *p;
6737
6738 if (unlikely(!debug_locks)) {
6739 pr_warn("INFO: lockdep is turned off.\n");
6740 return;
6741 }
6742 pr_warn("\nShowing all locks held in the system:\n");
6743
6744 rcu_read_lock();
6745 for_each_process_thread(g, p) {
6746 if (!p->lockdep_depth)
6747 continue;
6748 lockdep_print_held_locks(p);
6749 touch_nmi_watchdog();
6750 touch_all_softlockup_watchdogs();
6751 }
6752 rcu_read_unlock();
6753
6754 pr_warn("\n");
6755 pr_warn("=============================================\n\n");
6756}
6757EXPORT_SYMBOL_GPL(debug_show_all_locks);
6758#endif
6759
6760/*
6761 * Careful: only use this function if you are sure that
6762 * the task cannot run in parallel!
6763 */
6764void debug_show_held_locks(struct task_struct *task)
6765{
6766 if (unlikely(!debug_locks)) {
6767 printk("INFO: lockdep is turned off.\n");
6768 return;
6769 }
6770 lockdep_print_held_locks(task);
6771}
6772EXPORT_SYMBOL_GPL(debug_show_held_locks);
6773
6774asmlinkage __visible void lockdep_sys_exit(void)
6775{
6776 struct task_struct *curr = current;
6777
6778 if (unlikely(curr->lockdep_depth)) {
6779 if (!debug_locks_off())
6780 return;
6781 nbcon_cpu_emergency_enter();
6782 pr_warn("\n");
6783 pr_warn("================================================\n");
6784 pr_warn("WARNING: lock held when returning to user space!\n");
6785 print_kernel_ident();
6786 pr_warn("------------------------------------------------\n");
6787 pr_warn("%s/%d is leaving the kernel with locks still held!\n",
6788 curr->comm, curr->pid);
6789 lockdep_print_held_locks(curr);
6790 nbcon_cpu_emergency_exit();
6791 }
6792
6793 /*
6794 * The lock history for each syscall should be independent. So wipe the
6795 * slate clean on return to userspace.
6796 */
6797 lockdep_invariant_state(false);
6798}
6799
6800void lockdep_rcu_suspicious(const char *file, const int line, const char *s)
6801{
6802 struct task_struct *curr = current;
6803 int dl = READ_ONCE(debug_locks);
6804 bool rcu = warn_rcu_enter();
6805
6806 /* Note: the following can be executed concurrently, so be careful. */
6807 nbcon_cpu_emergency_enter();
6808 pr_warn("\n");
6809 pr_warn("=============================\n");
6810 pr_warn("WARNING: suspicious RCU usage\n");
6811 print_kernel_ident();
6812 pr_warn("-----------------------------\n");
6813 pr_warn("%s:%d %s!\n", file, line, s);
6814 pr_warn("\nother info that might help us debug this:\n\n");
6815 pr_warn("\n%srcu_scheduler_active = %d, debug_locks = %d\n%s",
6816 !rcu_lockdep_current_cpu_online()
6817 ? "RCU used illegally from offline CPU!\n"
6818 : "",
6819 rcu_scheduler_active, dl,
6820 dl ? "" : "Possible false positive due to lockdep disabling via debug_locks = 0\n");
6821
6822 /*
6823 * If a CPU is in the RCU-free window in idle (ie: in the section
6824 * between ct_idle_enter() and ct_idle_exit(), then RCU
6825 * considers that CPU to be in an "extended quiescent state",
6826 * which means that RCU will be completely ignoring that CPU.
6827 * Therefore, rcu_read_lock() and friends have absolutely no
6828 * effect on a CPU running in that state. In other words, even if
6829 * such an RCU-idle CPU has called rcu_read_lock(), RCU might well
6830 * delete data structures out from under it. RCU really has no
6831 * choice here: we need to keep an RCU-free window in idle where
6832 * the CPU may possibly enter into low power mode. This way we can
6833 * notice an extended quiescent state to other CPUs that started a grace
6834 * period. Otherwise we would delay any grace period as long as we run
6835 * in the idle task.
6836 *
6837 * So complain bitterly if someone does call rcu_read_lock(),
6838 * rcu_read_lock_bh() and so on from extended quiescent states.
6839 */
6840 if (!rcu_is_watching())
6841 pr_warn("RCU used illegally from extended quiescent state!\n");
6842
6843 lockdep_print_held_locks(curr);
6844 pr_warn("\nstack backtrace:\n");
6845 dump_stack();
6846 nbcon_cpu_emergency_exit();
6847 warn_rcu_exit(rcu);
6848}
6849EXPORT_SYMBOL_GPL(lockdep_rcu_suspicious);