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1/* CPU control.
2 * (C) 2001, 2002, 2003, 2004 Rusty Russell
3 *
4 * This code is licenced under the GPL.
5 */
6#include <linux/sched/mm.h>
7#include <linux/proc_fs.h>
8#include <linux/smp.h>
9#include <linux/init.h>
10#include <linux/notifier.h>
11#include <linux/sched/signal.h>
12#include <linux/sched/hotplug.h>
13#include <linux/sched/isolation.h>
14#include <linux/sched/task.h>
15#include <linux/sched/smt.h>
16#include <linux/unistd.h>
17#include <linux/cpu.h>
18#include <linux/oom.h>
19#include <linux/rcupdate.h>
20#include <linux/export.h>
21#include <linux/bug.h>
22#include <linux/kthread.h>
23#include <linux/stop_machine.h>
24#include <linux/mutex.h>
25#include <linux/gfp.h>
26#include <linux/suspend.h>
27#include <linux/lockdep.h>
28#include <linux/tick.h>
29#include <linux/irq.h>
30#include <linux/nmi.h>
31#include <linux/smpboot.h>
32#include <linux/relay.h>
33#include <linux/slab.h>
34#include <linux/scs.h>
35#include <linux/percpu-rwsem.h>
36#include <linux/cpuset.h>
37#include <linux/random.h>
38#include <linux/cc_platform.h>
39
40#include <trace/events/power.h>
41#define CREATE_TRACE_POINTS
42#include <trace/events/cpuhp.h>
43
44#include "smpboot.h"
45
46/**
47 * struct cpuhp_cpu_state - Per cpu hotplug state storage
48 * @state: The current cpu state
49 * @target: The target state
50 * @fail: Current CPU hotplug callback state
51 * @thread: Pointer to the hotplug thread
52 * @should_run: Thread should execute
53 * @rollback: Perform a rollback
54 * @single: Single callback invocation
55 * @bringup: Single callback bringup or teardown selector
56 * @cpu: CPU number
57 * @node: Remote CPU node; for multi-instance, do a
58 * single entry callback for install/remove
59 * @last: For multi-instance rollback, remember how far we got
60 * @cb_state: The state for a single callback (install/uninstall)
61 * @result: Result of the operation
62 * @done_up: Signal completion to the issuer of the task for cpu-up
63 * @done_down: Signal completion to the issuer of the task for cpu-down
64 */
65struct cpuhp_cpu_state {
66 enum cpuhp_state state;
67 enum cpuhp_state target;
68 enum cpuhp_state fail;
69#ifdef CONFIG_SMP
70 struct task_struct *thread;
71 bool should_run;
72 bool rollback;
73 bool single;
74 bool bringup;
75 struct hlist_node *node;
76 struct hlist_node *last;
77 enum cpuhp_state cb_state;
78 int result;
79 struct completion done_up;
80 struct completion done_down;
81#endif
82};
83
84static DEFINE_PER_CPU(struct cpuhp_cpu_state, cpuhp_state) = {
85 .fail = CPUHP_INVALID,
86};
87
88#ifdef CONFIG_SMP
89cpumask_t cpus_booted_once_mask;
90#endif
91
92#if defined(CONFIG_LOCKDEP) && defined(CONFIG_SMP)
93static struct lockdep_map cpuhp_state_up_map =
94 STATIC_LOCKDEP_MAP_INIT("cpuhp_state-up", &cpuhp_state_up_map);
95static struct lockdep_map cpuhp_state_down_map =
96 STATIC_LOCKDEP_MAP_INIT("cpuhp_state-down", &cpuhp_state_down_map);
97
98
99static inline void cpuhp_lock_acquire(bool bringup)
100{
101 lock_map_acquire(bringup ? &cpuhp_state_up_map : &cpuhp_state_down_map);
102}
103
104static inline void cpuhp_lock_release(bool bringup)
105{
106 lock_map_release(bringup ? &cpuhp_state_up_map : &cpuhp_state_down_map);
107}
108#else
109
110static inline void cpuhp_lock_acquire(bool bringup) { }
111static inline void cpuhp_lock_release(bool bringup) { }
112
113#endif
114
115/**
116 * struct cpuhp_step - Hotplug state machine step
117 * @name: Name of the step
118 * @startup: Startup function of the step
119 * @teardown: Teardown function of the step
120 * @cant_stop: Bringup/teardown can't be stopped at this step
121 * @multi_instance: State has multiple instances which get added afterwards
122 */
123struct cpuhp_step {
124 const char *name;
125 union {
126 int (*single)(unsigned int cpu);
127 int (*multi)(unsigned int cpu,
128 struct hlist_node *node);
129 } startup;
130 union {
131 int (*single)(unsigned int cpu);
132 int (*multi)(unsigned int cpu,
133 struct hlist_node *node);
134 } teardown;
135 /* private: */
136 struct hlist_head list;
137 /* public: */
138 bool cant_stop;
139 bool multi_instance;
140};
141
142static DEFINE_MUTEX(cpuhp_state_mutex);
143static struct cpuhp_step cpuhp_hp_states[];
144
145static struct cpuhp_step *cpuhp_get_step(enum cpuhp_state state)
146{
147 return cpuhp_hp_states + state;
148}
149
150static bool cpuhp_step_empty(bool bringup, struct cpuhp_step *step)
151{
152 return bringup ? !step->startup.single : !step->teardown.single;
153}
154
155/**
156 * cpuhp_invoke_callback - Invoke the callbacks for a given state
157 * @cpu: The cpu for which the callback should be invoked
158 * @state: The state to do callbacks for
159 * @bringup: True if the bringup callback should be invoked
160 * @node: For multi-instance, do a single entry callback for install/remove
161 * @lastp: For multi-instance rollback, remember how far we got
162 *
163 * Called from cpu hotplug and from the state register machinery.
164 *
165 * Return: %0 on success or a negative errno code
166 */
167static int cpuhp_invoke_callback(unsigned int cpu, enum cpuhp_state state,
168 bool bringup, struct hlist_node *node,
169 struct hlist_node **lastp)
170{
171 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
172 struct cpuhp_step *step = cpuhp_get_step(state);
173 int (*cbm)(unsigned int cpu, struct hlist_node *node);
174 int (*cb)(unsigned int cpu);
175 int ret, cnt;
176
177 if (st->fail == state) {
178 st->fail = CPUHP_INVALID;
179 return -EAGAIN;
180 }
181
182 if (cpuhp_step_empty(bringup, step)) {
183 WARN_ON_ONCE(1);
184 return 0;
185 }
186
187 if (!step->multi_instance) {
188 WARN_ON_ONCE(lastp && *lastp);
189 cb = bringup ? step->startup.single : step->teardown.single;
190
191 trace_cpuhp_enter(cpu, st->target, state, cb);
192 ret = cb(cpu);
193 trace_cpuhp_exit(cpu, st->state, state, ret);
194 return ret;
195 }
196 cbm = bringup ? step->startup.multi : step->teardown.multi;
197
198 /* Single invocation for instance add/remove */
199 if (node) {
200 WARN_ON_ONCE(lastp && *lastp);
201 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
202 ret = cbm(cpu, node);
203 trace_cpuhp_exit(cpu, st->state, state, ret);
204 return ret;
205 }
206
207 /* State transition. Invoke on all instances */
208 cnt = 0;
209 hlist_for_each(node, &step->list) {
210 if (lastp && node == *lastp)
211 break;
212
213 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
214 ret = cbm(cpu, node);
215 trace_cpuhp_exit(cpu, st->state, state, ret);
216 if (ret) {
217 if (!lastp)
218 goto err;
219
220 *lastp = node;
221 return ret;
222 }
223 cnt++;
224 }
225 if (lastp)
226 *lastp = NULL;
227 return 0;
228err:
229 /* Rollback the instances if one failed */
230 cbm = !bringup ? step->startup.multi : step->teardown.multi;
231 if (!cbm)
232 return ret;
233
234 hlist_for_each(node, &step->list) {
235 if (!cnt--)
236 break;
237
238 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
239 ret = cbm(cpu, node);
240 trace_cpuhp_exit(cpu, st->state, state, ret);
241 /*
242 * Rollback must not fail,
243 */
244 WARN_ON_ONCE(ret);
245 }
246 return ret;
247}
248
249#ifdef CONFIG_SMP
250static bool cpuhp_is_ap_state(enum cpuhp_state state)
251{
252 /*
253 * The extra check for CPUHP_TEARDOWN_CPU is only for documentation
254 * purposes as that state is handled explicitly in cpu_down.
255 */
256 return state > CPUHP_BRINGUP_CPU && state != CPUHP_TEARDOWN_CPU;
257}
258
259static inline void wait_for_ap_thread(struct cpuhp_cpu_state *st, bool bringup)
260{
261 struct completion *done = bringup ? &st->done_up : &st->done_down;
262 wait_for_completion(done);
263}
264
265static inline void complete_ap_thread(struct cpuhp_cpu_state *st, bool bringup)
266{
267 struct completion *done = bringup ? &st->done_up : &st->done_down;
268 complete(done);
269}
270
271/*
272 * The former STARTING/DYING states, ran with IRQs disabled and must not fail.
273 */
274static bool cpuhp_is_atomic_state(enum cpuhp_state state)
275{
276 return CPUHP_AP_IDLE_DEAD <= state && state < CPUHP_AP_ONLINE;
277}
278
279/* Serializes the updates to cpu_online_mask, cpu_present_mask */
280static DEFINE_MUTEX(cpu_add_remove_lock);
281bool cpuhp_tasks_frozen;
282EXPORT_SYMBOL_GPL(cpuhp_tasks_frozen);
283
284/*
285 * The following two APIs (cpu_maps_update_begin/done) must be used when
286 * attempting to serialize the updates to cpu_online_mask & cpu_present_mask.
287 */
288void cpu_maps_update_begin(void)
289{
290 mutex_lock(&cpu_add_remove_lock);
291}
292
293void cpu_maps_update_done(void)
294{
295 mutex_unlock(&cpu_add_remove_lock);
296}
297
298/*
299 * If set, cpu_up and cpu_down will return -EBUSY and do nothing.
300 * Should always be manipulated under cpu_add_remove_lock
301 */
302static int cpu_hotplug_disabled;
303
304#ifdef CONFIG_HOTPLUG_CPU
305
306DEFINE_STATIC_PERCPU_RWSEM(cpu_hotplug_lock);
307
308void cpus_read_lock(void)
309{
310 percpu_down_read(&cpu_hotplug_lock);
311}
312EXPORT_SYMBOL_GPL(cpus_read_lock);
313
314int cpus_read_trylock(void)
315{
316 return percpu_down_read_trylock(&cpu_hotplug_lock);
317}
318EXPORT_SYMBOL_GPL(cpus_read_trylock);
319
320void cpus_read_unlock(void)
321{
322 percpu_up_read(&cpu_hotplug_lock);
323}
324EXPORT_SYMBOL_GPL(cpus_read_unlock);
325
326void cpus_write_lock(void)
327{
328 percpu_down_write(&cpu_hotplug_lock);
329}
330
331void cpus_write_unlock(void)
332{
333 percpu_up_write(&cpu_hotplug_lock);
334}
335
336void lockdep_assert_cpus_held(void)
337{
338 /*
339 * We can't have hotplug operations before userspace starts running,
340 * and some init codepaths will knowingly not take the hotplug lock.
341 * This is all valid, so mute lockdep until it makes sense to report
342 * unheld locks.
343 */
344 if (system_state < SYSTEM_RUNNING)
345 return;
346
347 percpu_rwsem_assert_held(&cpu_hotplug_lock);
348}
349
350#ifdef CONFIG_LOCKDEP
351int lockdep_is_cpus_held(void)
352{
353 return percpu_rwsem_is_held(&cpu_hotplug_lock);
354}
355#endif
356
357static void lockdep_acquire_cpus_lock(void)
358{
359 rwsem_acquire(&cpu_hotplug_lock.dep_map, 0, 0, _THIS_IP_);
360}
361
362static void lockdep_release_cpus_lock(void)
363{
364 rwsem_release(&cpu_hotplug_lock.dep_map, _THIS_IP_);
365}
366
367/*
368 * Wait for currently running CPU hotplug operations to complete (if any) and
369 * disable future CPU hotplug (from sysfs). The 'cpu_add_remove_lock' protects
370 * the 'cpu_hotplug_disabled' flag. The same lock is also acquired by the
371 * hotplug path before performing hotplug operations. So acquiring that lock
372 * guarantees mutual exclusion from any currently running hotplug operations.
373 */
374void cpu_hotplug_disable(void)
375{
376 cpu_maps_update_begin();
377 cpu_hotplug_disabled++;
378 cpu_maps_update_done();
379}
380EXPORT_SYMBOL_GPL(cpu_hotplug_disable);
381
382static void __cpu_hotplug_enable(void)
383{
384 if (WARN_ONCE(!cpu_hotplug_disabled, "Unbalanced cpu hotplug enable\n"))
385 return;
386 cpu_hotplug_disabled--;
387}
388
389void cpu_hotplug_enable(void)
390{
391 cpu_maps_update_begin();
392 __cpu_hotplug_enable();
393 cpu_maps_update_done();
394}
395EXPORT_SYMBOL_GPL(cpu_hotplug_enable);
396
397#else
398
399static void lockdep_acquire_cpus_lock(void)
400{
401}
402
403static void lockdep_release_cpus_lock(void)
404{
405}
406
407#endif /* CONFIG_HOTPLUG_CPU */
408
409/*
410 * Architectures that need SMT-specific errata handling during SMT hotplug
411 * should override this.
412 */
413void __weak arch_smt_update(void) { }
414
415#ifdef CONFIG_HOTPLUG_SMT
416enum cpuhp_smt_control cpu_smt_control __read_mostly = CPU_SMT_ENABLED;
417
418void __init cpu_smt_disable(bool force)
419{
420 if (!cpu_smt_possible())
421 return;
422
423 if (force) {
424 pr_info("SMT: Force disabled\n");
425 cpu_smt_control = CPU_SMT_FORCE_DISABLED;
426 } else {
427 pr_info("SMT: disabled\n");
428 cpu_smt_control = CPU_SMT_DISABLED;
429 }
430}
431
432/*
433 * The decision whether SMT is supported can only be done after the full
434 * CPU identification. Called from architecture code.
435 */
436void __init cpu_smt_check_topology(void)
437{
438 if (!topology_smt_supported())
439 cpu_smt_control = CPU_SMT_NOT_SUPPORTED;
440}
441
442static int __init smt_cmdline_disable(char *str)
443{
444 cpu_smt_disable(str && !strcmp(str, "force"));
445 return 0;
446}
447early_param("nosmt", smt_cmdline_disable);
448
449static inline bool cpu_smt_allowed(unsigned int cpu)
450{
451 if (cpu_smt_control == CPU_SMT_ENABLED)
452 return true;
453
454 if (topology_is_primary_thread(cpu))
455 return true;
456
457 /*
458 * On x86 it's required to boot all logical CPUs at least once so
459 * that the init code can get a chance to set CR4.MCE on each
460 * CPU. Otherwise, a broadcasted MCE observing CR4.MCE=0b on any
461 * core will shutdown the machine.
462 */
463 return !cpumask_test_cpu(cpu, &cpus_booted_once_mask);
464}
465
466/* Returns true if SMT is not supported of forcefully (irreversibly) disabled */
467bool cpu_smt_possible(void)
468{
469 return cpu_smt_control != CPU_SMT_FORCE_DISABLED &&
470 cpu_smt_control != CPU_SMT_NOT_SUPPORTED;
471}
472EXPORT_SYMBOL_GPL(cpu_smt_possible);
473#else
474static inline bool cpu_smt_allowed(unsigned int cpu) { return true; }
475#endif
476
477static inline enum cpuhp_state
478cpuhp_set_state(int cpu, struct cpuhp_cpu_state *st, enum cpuhp_state target)
479{
480 enum cpuhp_state prev_state = st->state;
481 bool bringup = st->state < target;
482
483 st->rollback = false;
484 st->last = NULL;
485
486 st->target = target;
487 st->single = false;
488 st->bringup = bringup;
489 if (cpu_dying(cpu) != !bringup)
490 set_cpu_dying(cpu, !bringup);
491
492 return prev_state;
493}
494
495static inline void
496cpuhp_reset_state(int cpu, struct cpuhp_cpu_state *st,
497 enum cpuhp_state prev_state)
498{
499 bool bringup = !st->bringup;
500
501 st->target = prev_state;
502
503 /*
504 * Already rolling back. No need invert the bringup value or to change
505 * the current state.
506 */
507 if (st->rollback)
508 return;
509
510 st->rollback = true;
511
512 /*
513 * If we have st->last we need to undo partial multi_instance of this
514 * state first. Otherwise start undo at the previous state.
515 */
516 if (!st->last) {
517 if (st->bringup)
518 st->state--;
519 else
520 st->state++;
521 }
522
523 st->bringup = bringup;
524 if (cpu_dying(cpu) != !bringup)
525 set_cpu_dying(cpu, !bringup);
526}
527
528/* Regular hotplug invocation of the AP hotplug thread */
529static void __cpuhp_kick_ap(struct cpuhp_cpu_state *st)
530{
531 if (!st->single && st->state == st->target)
532 return;
533
534 st->result = 0;
535 /*
536 * Make sure the above stores are visible before should_run becomes
537 * true. Paired with the mb() above in cpuhp_thread_fun()
538 */
539 smp_mb();
540 st->should_run = true;
541 wake_up_process(st->thread);
542 wait_for_ap_thread(st, st->bringup);
543}
544
545static int cpuhp_kick_ap(int cpu, struct cpuhp_cpu_state *st,
546 enum cpuhp_state target)
547{
548 enum cpuhp_state prev_state;
549 int ret;
550
551 prev_state = cpuhp_set_state(cpu, st, target);
552 __cpuhp_kick_ap(st);
553 if ((ret = st->result)) {
554 cpuhp_reset_state(cpu, st, prev_state);
555 __cpuhp_kick_ap(st);
556 }
557
558 return ret;
559}
560
561static int bringup_wait_for_ap(unsigned int cpu)
562{
563 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
564
565 /* Wait for the CPU to reach CPUHP_AP_ONLINE_IDLE */
566 wait_for_ap_thread(st, true);
567 if (WARN_ON_ONCE((!cpu_online(cpu))))
568 return -ECANCELED;
569
570 /* Unpark the hotplug thread of the target cpu */
571 kthread_unpark(st->thread);
572
573 /*
574 * SMT soft disabling on X86 requires to bring the CPU out of the
575 * BIOS 'wait for SIPI' state in order to set the CR4.MCE bit. The
576 * CPU marked itself as booted_once in notify_cpu_starting() so the
577 * cpu_smt_allowed() check will now return false if this is not the
578 * primary sibling.
579 */
580 if (!cpu_smt_allowed(cpu))
581 return -ECANCELED;
582
583 if (st->target <= CPUHP_AP_ONLINE_IDLE)
584 return 0;
585
586 return cpuhp_kick_ap(cpu, st, st->target);
587}
588
589static int bringup_cpu(unsigned int cpu)
590{
591 struct task_struct *idle = idle_thread_get(cpu);
592 int ret;
593
594 /*
595 * Reset stale stack state from the last time this CPU was online.
596 */
597 scs_task_reset(idle);
598 kasan_unpoison_task_stack(idle);
599
600 /*
601 * Some architectures have to walk the irq descriptors to
602 * setup the vector space for the cpu which comes online.
603 * Prevent irq alloc/free across the bringup.
604 */
605 irq_lock_sparse();
606
607 /* Arch-specific enabling code. */
608 ret = __cpu_up(cpu, idle);
609 irq_unlock_sparse();
610 if (ret)
611 return ret;
612 return bringup_wait_for_ap(cpu);
613}
614
615static int finish_cpu(unsigned int cpu)
616{
617 struct task_struct *idle = idle_thread_get(cpu);
618 struct mm_struct *mm = idle->active_mm;
619
620 /*
621 * idle_task_exit() will have switched to &init_mm, now
622 * clean up any remaining active_mm state.
623 */
624 if (mm != &init_mm)
625 idle->active_mm = &init_mm;
626 mmdrop(mm);
627 return 0;
628}
629
630/*
631 * Hotplug state machine related functions
632 */
633
634/*
635 * Get the next state to run. Empty ones will be skipped. Returns true if a
636 * state must be run.
637 *
638 * st->state will be modified ahead of time, to match state_to_run, as if it
639 * has already ran.
640 */
641static bool cpuhp_next_state(bool bringup,
642 enum cpuhp_state *state_to_run,
643 struct cpuhp_cpu_state *st,
644 enum cpuhp_state target)
645{
646 do {
647 if (bringup) {
648 if (st->state >= target)
649 return false;
650
651 *state_to_run = ++st->state;
652 } else {
653 if (st->state <= target)
654 return false;
655
656 *state_to_run = st->state--;
657 }
658
659 if (!cpuhp_step_empty(bringup, cpuhp_get_step(*state_to_run)))
660 break;
661 } while (true);
662
663 return true;
664}
665
666static int __cpuhp_invoke_callback_range(bool bringup,
667 unsigned int cpu,
668 struct cpuhp_cpu_state *st,
669 enum cpuhp_state target,
670 bool nofail)
671{
672 enum cpuhp_state state;
673 int ret = 0;
674
675 while (cpuhp_next_state(bringup, &state, st, target)) {
676 int err;
677
678 err = cpuhp_invoke_callback(cpu, state, bringup, NULL, NULL);
679 if (!err)
680 continue;
681
682 if (nofail) {
683 pr_warn("CPU %u %s state %s (%d) failed (%d)\n",
684 cpu, bringup ? "UP" : "DOWN",
685 cpuhp_get_step(st->state)->name,
686 st->state, err);
687 ret = -1;
688 } else {
689 ret = err;
690 break;
691 }
692 }
693
694 return ret;
695}
696
697static inline int cpuhp_invoke_callback_range(bool bringup,
698 unsigned int cpu,
699 struct cpuhp_cpu_state *st,
700 enum cpuhp_state target)
701{
702 return __cpuhp_invoke_callback_range(bringup, cpu, st, target, false);
703}
704
705static inline void cpuhp_invoke_callback_range_nofail(bool bringup,
706 unsigned int cpu,
707 struct cpuhp_cpu_state *st,
708 enum cpuhp_state target)
709{
710 __cpuhp_invoke_callback_range(bringup, cpu, st, target, true);
711}
712
713static inline bool can_rollback_cpu(struct cpuhp_cpu_state *st)
714{
715 if (IS_ENABLED(CONFIG_HOTPLUG_CPU))
716 return true;
717 /*
718 * When CPU hotplug is disabled, then taking the CPU down is not
719 * possible because takedown_cpu() and the architecture and
720 * subsystem specific mechanisms are not available. So the CPU
721 * which would be completely unplugged again needs to stay around
722 * in the current state.
723 */
724 return st->state <= CPUHP_BRINGUP_CPU;
725}
726
727static int cpuhp_up_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
728 enum cpuhp_state target)
729{
730 enum cpuhp_state prev_state = st->state;
731 int ret = 0;
732
733 ret = cpuhp_invoke_callback_range(true, cpu, st, target);
734 if (ret) {
735 pr_debug("CPU UP failed (%d) CPU %u state %s (%d)\n",
736 ret, cpu, cpuhp_get_step(st->state)->name,
737 st->state);
738
739 cpuhp_reset_state(cpu, st, prev_state);
740 if (can_rollback_cpu(st))
741 WARN_ON(cpuhp_invoke_callback_range(false, cpu, st,
742 prev_state));
743 }
744 return ret;
745}
746
747/*
748 * The cpu hotplug threads manage the bringup and teardown of the cpus
749 */
750static int cpuhp_should_run(unsigned int cpu)
751{
752 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
753
754 return st->should_run;
755}
756
757/*
758 * Execute teardown/startup callbacks on the plugged cpu. Also used to invoke
759 * callbacks when a state gets [un]installed at runtime.
760 *
761 * Each invocation of this function by the smpboot thread does a single AP
762 * state callback.
763 *
764 * It has 3 modes of operation:
765 * - single: runs st->cb_state
766 * - up: runs ++st->state, while st->state < st->target
767 * - down: runs st->state--, while st->state > st->target
768 *
769 * When complete or on error, should_run is cleared and the completion is fired.
770 */
771static void cpuhp_thread_fun(unsigned int cpu)
772{
773 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
774 bool bringup = st->bringup;
775 enum cpuhp_state state;
776
777 if (WARN_ON_ONCE(!st->should_run))
778 return;
779
780 /*
781 * ACQUIRE for the cpuhp_should_run() load of ->should_run. Ensures
782 * that if we see ->should_run we also see the rest of the state.
783 */
784 smp_mb();
785
786 /*
787 * The BP holds the hotplug lock, but we're now running on the AP,
788 * ensure that anybody asserting the lock is held, will actually find
789 * it so.
790 */
791 lockdep_acquire_cpus_lock();
792 cpuhp_lock_acquire(bringup);
793
794 if (st->single) {
795 state = st->cb_state;
796 st->should_run = false;
797 } else {
798 st->should_run = cpuhp_next_state(bringup, &state, st, st->target);
799 if (!st->should_run)
800 goto end;
801 }
802
803 WARN_ON_ONCE(!cpuhp_is_ap_state(state));
804
805 if (cpuhp_is_atomic_state(state)) {
806 local_irq_disable();
807 st->result = cpuhp_invoke_callback(cpu, state, bringup, st->node, &st->last);
808 local_irq_enable();
809
810 /*
811 * STARTING/DYING must not fail!
812 */
813 WARN_ON_ONCE(st->result);
814 } else {
815 st->result = cpuhp_invoke_callback(cpu, state, bringup, st->node, &st->last);
816 }
817
818 if (st->result) {
819 /*
820 * If we fail on a rollback, we're up a creek without no
821 * paddle, no way forward, no way back. We loose, thanks for
822 * playing.
823 */
824 WARN_ON_ONCE(st->rollback);
825 st->should_run = false;
826 }
827
828end:
829 cpuhp_lock_release(bringup);
830 lockdep_release_cpus_lock();
831
832 if (!st->should_run)
833 complete_ap_thread(st, bringup);
834}
835
836/* Invoke a single callback on a remote cpu */
837static int
838cpuhp_invoke_ap_callback(int cpu, enum cpuhp_state state, bool bringup,
839 struct hlist_node *node)
840{
841 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
842 int ret;
843
844 if (!cpu_online(cpu))
845 return 0;
846
847 cpuhp_lock_acquire(false);
848 cpuhp_lock_release(false);
849
850 cpuhp_lock_acquire(true);
851 cpuhp_lock_release(true);
852
853 /*
854 * If we are up and running, use the hotplug thread. For early calls
855 * we invoke the thread function directly.
856 */
857 if (!st->thread)
858 return cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
859
860 st->rollback = false;
861 st->last = NULL;
862
863 st->node = node;
864 st->bringup = bringup;
865 st->cb_state = state;
866 st->single = true;
867
868 __cpuhp_kick_ap(st);
869
870 /*
871 * If we failed and did a partial, do a rollback.
872 */
873 if ((ret = st->result) && st->last) {
874 st->rollback = true;
875 st->bringup = !bringup;
876
877 __cpuhp_kick_ap(st);
878 }
879
880 /*
881 * Clean up the leftovers so the next hotplug operation wont use stale
882 * data.
883 */
884 st->node = st->last = NULL;
885 return ret;
886}
887
888static int cpuhp_kick_ap_work(unsigned int cpu)
889{
890 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
891 enum cpuhp_state prev_state = st->state;
892 int ret;
893
894 cpuhp_lock_acquire(false);
895 cpuhp_lock_release(false);
896
897 cpuhp_lock_acquire(true);
898 cpuhp_lock_release(true);
899
900 trace_cpuhp_enter(cpu, st->target, prev_state, cpuhp_kick_ap_work);
901 ret = cpuhp_kick_ap(cpu, st, st->target);
902 trace_cpuhp_exit(cpu, st->state, prev_state, ret);
903
904 return ret;
905}
906
907static struct smp_hotplug_thread cpuhp_threads = {
908 .store = &cpuhp_state.thread,
909 .thread_should_run = cpuhp_should_run,
910 .thread_fn = cpuhp_thread_fun,
911 .thread_comm = "cpuhp/%u",
912 .selfparking = true,
913};
914
915static __init void cpuhp_init_state(void)
916{
917 struct cpuhp_cpu_state *st;
918 int cpu;
919
920 for_each_possible_cpu(cpu) {
921 st = per_cpu_ptr(&cpuhp_state, cpu);
922 init_completion(&st->done_up);
923 init_completion(&st->done_down);
924 }
925}
926
927void __init cpuhp_threads_init(void)
928{
929 cpuhp_init_state();
930 BUG_ON(smpboot_register_percpu_thread(&cpuhp_threads));
931 kthread_unpark(this_cpu_read(cpuhp_state.thread));
932}
933
934/*
935 *
936 * Serialize hotplug trainwrecks outside of the cpu_hotplug_lock
937 * protected region.
938 *
939 * The operation is still serialized against concurrent CPU hotplug via
940 * cpu_add_remove_lock, i.e. CPU map protection. But it is _not_
941 * serialized against other hotplug related activity like adding or
942 * removing of state callbacks and state instances, which invoke either the
943 * startup or the teardown callback of the affected state.
944 *
945 * This is required for subsystems which are unfixable vs. CPU hotplug and
946 * evade lock inversion problems by scheduling work which has to be
947 * completed _before_ cpu_up()/_cpu_down() returns.
948 *
949 * Don't even think about adding anything to this for any new code or even
950 * drivers. It's only purpose is to keep existing lock order trainwrecks
951 * working.
952 *
953 * For cpu_down() there might be valid reasons to finish cleanups which are
954 * not required to be done under cpu_hotplug_lock, but that's a different
955 * story and would be not invoked via this.
956 */
957static void cpu_up_down_serialize_trainwrecks(bool tasks_frozen)
958{
959 /*
960 * cpusets delegate hotplug operations to a worker to "solve" the
961 * lock order problems. Wait for the worker, but only if tasks are
962 * _not_ frozen (suspend, hibernate) as that would wait forever.
963 *
964 * The wait is required because otherwise the hotplug operation
965 * returns with inconsistent state, which could even be observed in
966 * user space when a new CPU is brought up. The CPU plug uevent
967 * would be delivered and user space reacting on it would fail to
968 * move tasks to the newly plugged CPU up to the point where the
969 * work has finished because up to that point the newly plugged CPU
970 * is not assignable in cpusets/cgroups. On unplug that's not
971 * necessarily a visible issue, but it is still inconsistent state,
972 * which is the real problem which needs to be "fixed". This can't
973 * prevent the transient state between scheduling the work and
974 * returning from waiting for it.
975 */
976 if (!tasks_frozen)
977 cpuset_wait_for_hotplug();
978}
979
980#ifdef CONFIG_HOTPLUG_CPU
981#ifndef arch_clear_mm_cpumask_cpu
982#define arch_clear_mm_cpumask_cpu(cpu, mm) cpumask_clear_cpu(cpu, mm_cpumask(mm))
983#endif
984
985/**
986 * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
987 * @cpu: a CPU id
988 *
989 * This function walks all processes, finds a valid mm struct for each one and
990 * then clears a corresponding bit in mm's cpumask. While this all sounds
991 * trivial, there are various non-obvious corner cases, which this function
992 * tries to solve in a safe manner.
993 *
994 * Also note that the function uses a somewhat relaxed locking scheme, so it may
995 * be called only for an already offlined CPU.
996 */
997void clear_tasks_mm_cpumask(int cpu)
998{
999 struct task_struct *p;
1000
1001 /*
1002 * This function is called after the cpu is taken down and marked
1003 * offline, so its not like new tasks will ever get this cpu set in
1004 * their mm mask. -- Peter Zijlstra
1005 * Thus, we may use rcu_read_lock() here, instead of grabbing
1006 * full-fledged tasklist_lock.
1007 */
1008 WARN_ON(cpu_online(cpu));
1009 rcu_read_lock();
1010 for_each_process(p) {
1011 struct task_struct *t;
1012
1013 /*
1014 * Main thread might exit, but other threads may still have
1015 * a valid mm. Find one.
1016 */
1017 t = find_lock_task_mm(p);
1018 if (!t)
1019 continue;
1020 arch_clear_mm_cpumask_cpu(cpu, t->mm);
1021 task_unlock(t);
1022 }
1023 rcu_read_unlock();
1024}
1025
1026/* Take this CPU down. */
1027static int take_cpu_down(void *_param)
1028{
1029 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
1030 enum cpuhp_state target = max((int)st->target, CPUHP_AP_OFFLINE);
1031 int err, cpu = smp_processor_id();
1032
1033 /* Ensure this CPU doesn't handle any more interrupts. */
1034 err = __cpu_disable();
1035 if (err < 0)
1036 return err;
1037
1038 /*
1039 * Must be called from CPUHP_TEARDOWN_CPU, which means, as we are going
1040 * down, that the current state is CPUHP_TEARDOWN_CPU - 1.
1041 */
1042 WARN_ON(st->state != (CPUHP_TEARDOWN_CPU - 1));
1043
1044 /*
1045 * Invoke the former CPU_DYING callbacks. DYING must not fail!
1046 */
1047 cpuhp_invoke_callback_range_nofail(false, cpu, st, target);
1048
1049 /* Give up timekeeping duties */
1050 tick_handover_do_timer();
1051 /* Remove CPU from timer broadcasting */
1052 tick_offline_cpu(cpu);
1053 /* Park the stopper thread */
1054 stop_machine_park(cpu);
1055 return 0;
1056}
1057
1058static int takedown_cpu(unsigned int cpu)
1059{
1060 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1061 int err;
1062
1063 /* Park the smpboot threads */
1064 kthread_park(st->thread);
1065
1066 /*
1067 * Prevent irq alloc/free while the dying cpu reorganizes the
1068 * interrupt affinities.
1069 */
1070 irq_lock_sparse();
1071
1072 /*
1073 * So now all preempt/rcu users must observe !cpu_active().
1074 */
1075 err = stop_machine_cpuslocked(take_cpu_down, NULL, cpumask_of(cpu));
1076 if (err) {
1077 /* CPU refused to die */
1078 irq_unlock_sparse();
1079 /* Unpark the hotplug thread so we can rollback there */
1080 kthread_unpark(st->thread);
1081 return err;
1082 }
1083 BUG_ON(cpu_online(cpu));
1084
1085 /*
1086 * The teardown callback for CPUHP_AP_SCHED_STARTING will have removed
1087 * all runnable tasks from the CPU, there's only the idle task left now
1088 * that the migration thread is done doing the stop_machine thing.
1089 *
1090 * Wait for the stop thread to go away.
1091 */
1092 wait_for_ap_thread(st, false);
1093 BUG_ON(st->state != CPUHP_AP_IDLE_DEAD);
1094
1095 /* Interrupts are moved away from the dying cpu, reenable alloc/free */
1096 irq_unlock_sparse();
1097
1098 hotplug_cpu__broadcast_tick_pull(cpu);
1099 /* This actually kills the CPU. */
1100 __cpu_die(cpu);
1101
1102 tick_cleanup_dead_cpu(cpu);
1103 rcutree_migrate_callbacks(cpu);
1104 return 0;
1105}
1106
1107static void cpuhp_complete_idle_dead(void *arg)
1108{
1109 struct cpuhp_cpu_state *st = arg;
1110
1111 complete_ap_thread(st, false);
1112}
1113
1114void cpuhp_report_idle_dead(void)
1115{
1116 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
1117
1118 BUG_ON(st->state != CPUHP_AP_OFFLINE);
1119 rcu_report_dead(smp_processor_id());
1120 st->state = CPUHP_AP_IDLE_DEAD;
1121 /*
1122 * We cannot call complete after rcu_report_dead() so we delegate it
1123 * to an online cpu.
1124 */
1125 smp_call_function_single(cpumask_first(cpu_online_mask),
1126 cpuhp_complete_idle_dead, st, 0);
1127}
1128
1129static int cpuhp_down_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
1130 enum cpuhp_state target)
1131{
1132 enum cpuhp_state prev_state = st->state;
1133 int ret = 0;
1134
1135 ret = cpuhp_invoke_callback_range(false, cpu, st, target);
1136 if (ret) {
1137 pr_debug("CPU DOWN failed (%d) CPU %u state %s (%d)\n",
1138 ret, cpu, cpuhp_get_step(st->state)->name,
1139 st->state);
1140
1141 cpuhp_reset_state(cpu, st, prev_state);
1142
1143 if (st->state < prev_state)
1144 WARN_ON(cpuhp_invoke_callback_range(true, cpu, st,
1145 prev_state));
1146 }
1147
1148 return ret;
1149}
1150
1151/* Requires cpu_add_remove_lock to be held */
1152static int __ref _cpu_down(unsigned int cpu, int tasks_frozen,
1153 enum cpuhp_state target)
1154{
1155 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1156 int prev_state, ret = 0;
1157
1158 if (num_online_cpus() == 1)
1159 return -EBUSY;
1160
1161 if (!cpu_present(cpu))
1162 return -EINVAL;
1163
1164 cpus_write_lock();
1165
1166 cpuhp_tasks_frozen = tasks_frozen;
1167
1168 prev_state = cpuhp_set_state(cpu, st, target);
1169 /*
1170 * If the current CPU state is in the range of the AP hotplug thread,
1171 * then we need to kick the thread.
1172 */
1173 if (st->state > CPUHP_TEARDOWN_CPU) {
1174 st->target = max((int)target, CPUHP_TEARDOWN_CPU);
1175 ret = cpuhp_kick_ap_work(cpu);
1176 /*
1177 * The AP side has done the error rollback already. Just
1178 * return the error code..
1179 */
1180 if (ret)
1181 goto out;
1182
1183 /*
1184 * We might have stopped still in the range of the AP hotplug
1185 * thread. Nothing to do anymore.
1186 */
1187 if (st->state > CPUHP_TEARDOWN_CPU)
1188 goto out;
1189
1190 st->target = target;
1191 }
1192 /*
1193 * The AP brought itself down to CPUHP_TEARDOWN_CPU. So we need
1194 * to do the further cleanups.
1195 */
1196 ret = cpuhp_down_callbacks(cpu, st, target);
1197 if (ret && st->state < prev_state) {
1198 if (st->state == CPUHP_TEARDOWN_CPU) {
1199 cpuhp_reset_state(cpu, st, prev_state);
1200 __cpuhp_kick_ap(st);
1201 } else {
1202 WARN(1, "DEAD callback error for CPU%d", cpu);
1203 }
1204 }
1205
1206out:
1207 cpus_write_unlock();
1208 /*
1209 * Do post unplug cleanup. This is still protected against
1210 * concurrent CPU hotplug via cpu_add_remove_lock.
1211 */
1212 lockup_detector_cleanup();
1213 arch_smt_update();
1214 cpu_up_down_serialize_trainwrecks(tasks_frozen);
1215 return ret;
1216}
1217
1218static int cpu_down_maps_locked(unsigned int cpu, enum cpuhp_state target)
1219{
1220 /*
1221 * If the platform does not support hotplug, report it explicitly to
1222 * differentiate it from a transient offlining failure.
1223 */
1224 if (cc_platform_has(CC_ATTR_HOTPLUG_DISABLED))
1225 return -EOPNOTSUPP;
1226 if (cpu_hotplug_disabled)
1227 return -EBUSY;
1228 return _cpu_down(cpu, 0, target);
1229}
1230
1231static int cpu_down(unsigned int cpu, enum cpuhp_state target)
1232{
1233 int err;
1234
1235 cpu_maps_update_begin();
1236 err = cpu_down_maps_locked(cpu, target);
1237 cpu_maps_update_done();
1238 return err;
1239}
1240
1241/**
1242 * cpu_device_down - Bring down a cpu device
1243 * @dev: Pointer to the cpu device to offline
1244 *
1245 * This function is meant to be used by device core cpu subsystem only.
1246 *
1247 * Other subsystems should use remove_cpu() instead.
1248 *
1249 * Return: %0 on success or a negative errno code
1250 */
1251int cpu_device_down(struct device *dev)
1252{
1253 return cpu_down(dev->id, CPUHP_OFFLINE);
1254}
1255
1256int remove_cpu(unsigned int cpu)
1257{
1258 int ret;
1259
1260 lock_device_hotplug();
1261 ret = device_offline(get_cpu_device(cpu));
1262 unlock_device_hotplug();
1263
1264 return ret;
1265}
1266EXPORT_SYMBOL_GPL(remove_cpu);
1267
1268void smp_shutdown_nonboot_cpus(unsigned int primary_cpu)
1269{
1270 unsigned int cpu;
1271 int error;
1272
1273 cpu_maps_update_begin();
1274
1275 /*
1276 * Make certain the cpu I'm about to reboot on is online.
1277 *
1278 * This is inline to what migrate_to_reboot_cpu() already do.
1279 */
1280 if (!cpu_online(primary_cpu))
1281 primary_cpu = cpumask_first(cpu_online_mask);
1282
1283 for_each_online_cpu(cpu) {
1284 if (cpu == primary_cpu)
1285 continue;
1286
1287 error = cpu_down_maps_locked(cpu, CPUHP_OFFLINE);
1288 if (error) {
1289 pr_err("Failed to offline CPU%d - error=%d",
1290 cpu, error);
1291 break;
1292 }
1293 }
1294
1295 /*
1296 * Ensure all but the reboot CPU are offline.
1297 */
1298 BUG_ON(num_online_cpus() > 1);
1299
1300 /*
1301 * Make sure the CPUs won't be enabled by someone else after this
1302 * point. Kexec will reboot to a new kernel shortly resetting
1303 * everything along the way.
1304 */
1305 cpu_hotplug_disabled++;
1306
1307 cpu_maps_update_done();
1308}
1309
1310#else
1311#define takedown_cpu NULL
1312#endif /*CONFIG_HOTPLUG_CPU*/
1313
1314/**
1315 * notify_cpu_starting(cpu) - Invoke the callbacks on the starting CPU
1316 * @cpu: cpu that just started
1317 *
1318 * It must be called by the arch code on the new cpu, before the new cpu
1319 * enables interrupts and before the "boot" cpu returns from __cpu_up().
1320 */
1321void notify_cpu_starting(unsigned int cpu)
1322{
1323 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1324 enum cpuhp_state target = min((int)st->target, CPUHP_AP_ONLINE);
1325
1326 rcu_cpu_starting(cpu); /* Enables RCU usage on this CPU. */
1327 cpumask_set_cpu(cpu, &cpus_booted_once_mask);
1328
1329 /*
1330 * STARTING must not fail!
1331 */
1332 cpuhp_invoke_callback_range_nofail(true, cpu, st, target);
1333}
1334
1335/*
1336 * Called from the idle task. Wake up the controlling task which brings the
1337 * hotplug thread of the upcoming CPU up and then delegates the rest of the
1338 * online bringup to the hotplug thread.
1339 */
1340void cpuhp_online_idle(enum cpuhp_state state)
1341{
1342 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
1343
1344 /* Happens for the boot cpu */
1345 if (state != CPUHP_AP_ONLINE_IDLE)
1346 return;
1347
1348 /*
1349 * Unpart the stopper thread before we start the idle loop (and start
1350 * scheduling); this ensures the stopper task is always available.
1351 */
1352 stop_machine_unpark(smp_processor_id());
1353
1354 st->state = CPUHP_AP_ONLINE_IDLE;
1355 complete_ap_thread(st, true);
1356}
1357
1358/* Requires cpu_add_remove_lock to be held */
1359static int _cpu_up(unsigned int cpu, int tasks_frozen, enum cpuhp_state target)
1360{
1361 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1362 struct task_struct *idle;
1363 int ret = 0;
1364
1365 cpus_write_lock();
1366
1367 if (!cpu_present(cpu)) {
1368 ret = -EINVAL;
1369 goto out;
1370 }
1371
1372 /*
1373 * The caller of cpu_up() might have raced with another
1374 * caller. Nothing to do.
1375 */
1376 if (st->state >= target)
1377 goto out;
1378
1379 if (st->state == CPUHP_OFFLINE) {
1380 /* Let it fail before we try to bring the cpu up */
1381 idle = idle_thread_get(cpu);
1382 if (IS_ERR(idle)) {
1383 ret = PTR_ERR(idle);
1384 goto out;
1385 }
1386 }
1387
1388 cpuhp_tasks_frozen = tasks_frozen;
1389
1390 cpuhp_set_state(cpu, st, target);
1391 /*
1392 * If the current CPU state is in the range of the AP hotplug thread,
1393 * then we need to kick the thread once more.
1394 */
1395 if (st->state > CPUHP_BRINGUP_CPU) {
1396 ret = cpuhp_kick_ap_work(cpu);
1397 /*
1398 * The AP side has done the error rollback already. Just
1399 * return the error code..
1400 */
1401 if (ret)
1402 goto out;
1403 }
1404
1405 /*
1406 * Try to reach the target state. We max out on the BP at
1407 * CPUHP_BRINGUP_CPU. After that the AP hotplug thread is
1408 * responsible for bringing it up to the target state.
1409 */
1410 target = min((int)target, CPUHP_BRINGUP_CPU);
1411 ret = cpuhp_up_callbacks(cpu, st, target);
1412out:
1413 cpus_write_unlock();
1414 arch_smt_update();
1415 cpu_up_down_serialize_trainwrecks(tasks_frozen);
1416 return ret;
1417}
1418
1419static int cpu_up(unsigned int cpu, enum cpuhp_state target)
1420{
1421 int err = 0;
1422
1423 if (!cpu_possible(cpu)) {
1424 pr_err("can't online cpu %d because it is not configured as may-hotadd at boot time\n",
1425 cpu);
1426#if defined(CONFIG_IA64)
1427 pr_err("please check additional_cpus= boot parameter\n");
1428#endif
1429 return -EINVAL;
1430 }
1431
1432 err = try_online_node(cpu_to_node(cpu));
1433 if (err)
1434 return err;
1435
1436 cpu_maps_update_begin();
1437
1438 if (cpu_hotplug_disabled) {
1439 err = -EBUSY;
1440 goto out;
1441 }
1442 if (!cpu_smt_allowed(cpu)) {
1443 err = -EPERM;
1444 goto out;
1445 }
1446
1447 err = _cpu_up(cpu, 0, target);
1448out:
1449 cpu_maps_update_done();
1450 return err;
1451}
1452
1453/**
1454 * cpu_device_up - Bring up a cpu device
1455 * @dev: Pointer to the cpu device to online
1456 *
1457 * This function is meant to be used by device core cpu subsystem only.
1458 *
1459 * Other subsystems should use add_cpu() instead.
1460 *
1461 * Return: %0 on success or a negative errno code
1462 */
1463int cpu_device_up(struct device *dev)
1464{
1465 return cpu_up(dev->id, CPUHP_ONLINE);
1466}
1467
1468int add_cpu(unsigned int cpu)
1469{
1470 int ret;
1471
1472 lock_device_hotplug();
1473 ret = device_online(get_cpu_device(cpu));
1474 unlock_device_hotplug();
1475
1476 return ret;
1477}
1478EXPORT_SYMBOL_GPL(add_cpu);
1479
1480/**
1481 * bringup_hibernate_cpu - Bring up the CPU that we hibernated on
1482 * @sleep_cpu: The cpu we hibernated on and should be brought up.
1483 *
1484 * On some architectures like arm64, we can hibernate on any CPU, but on
1485 * wake up the CPU we hibernated on might be offline as a side effect of
1486 * using maxcpus= for example.
1487 *
1488 * Return: %0 on success or a negative errno code
1489 */
1490int bringup_hibernate_cpu(unsigned int sleep_cpu)
1491{
1492 int ret;
1493
1494 if (!cpu_online(sleep_cpu)) {
1495 pr_info("Hibernated on a CPU that is offline! Bringing CPU up.\n");
1496 ret = cpu_up(sleep_cpu, CPUHP_ONLINE);
1497 if (ret) {
1498 pr_err("Failed to bring hibernate-CPU up!\n");
1499 return ret;
1500 }
1501 }
1502 return 0;
1503}
1504
1505void bringup_nonboot_cpus(unsigned int setup_max_cpus)
1506{
1507 unsigned int cpu;
1508
1509 for_each_present_cpu(cpu) {
1510 if (num_online_cpus() >= setup_max_cpus)
1511 break;
1512 if (!cpu_online(cpu))
1513 cpu_up(cpu, CPUHP_ONLINE);
1514 }
1515}
1516
1517#ifdef CONFIG_PM_SLEEP_SMP
1518static cpumask_var_t frozen_cpus;
1519
1520int freeze_secondary_cpus(int primary)
1521{
1522 int cpu, error = 0;
1523
1524 cpu_maps_update_begin();
1525 if (primary == -1) {
1526 primary = cpumask_first(cpu_online_mask);
1527 if (!housekeeping_cpu(primary, HK_TYPE_TIMER))
1528 primary = housekeeping_any_cpu(HK_TYPE_TIMER);
1529 } else {
1530 if (!cpu_online(primary))
1531 primary = cpumask_first(cpu_online_mask);
1532 }
1533
1534 /*
1535 * We take down all of the non-boot CPUs in one shot to avoid races
1536 * with the userspace trying to use the CPU hotplug at the same time
1537 */
1538 cpumask_clear(frozen_cpus);
1539
1540 pr_info("Disabling non-boot CPUs ...\n");
1541 for_each_online_cpu(cpu) {
1542 if (cpu == primary)
1543 continue;
1544
1545 if (pm_wakeup_pending()) {
1546 pr_info("Wakeup pending. Abort CPU freeze\n");
1547 error = -EBUSY;
1548 break;
1549 }
1550
1551 trace_suspend_resume(TPS("CPU_OFF"), cpu, true);
1552 error = _cpu_down(cpu, 1, CPUHP_OFFLINE);
1553 trace_suspend_resume(TPS("CPU_OFF"), cpu, false);
1554 if (!error)
1555 cpumask_set_cpu(cpu, frozen_cpus);
1556 else {
1557 pr_err("Error taking CPU%d down: %d\n", cpu, error);
1558 break;
1559 }
1560 }
1561
1562 if (!error)
1563 BUG_ON(num_online_cpus() > 1);
1564 else
1565 pr_err("Non-boot CPUs are not disabled\n");
1566
1567 /*
1568 * Make sure the CPUs won't be enabled by someone else. We need to do
1569 * this even in case of failure as all freeze_secondary_cpus() users are
1570 * supposed to do thaw_secondary_cpus() on the failure path.
1571 */
1572 cpu_hotplug_disabled++;
1573
1574 cpu_maps_update_done();
1575 return error;
1576}
1577
1578void __weak arch_thaw_secondary_cpus_begin(void)
1579{
1580}
1581
1582void __weak arch_thaw_secondary_cpus_end(void)
1583{
1584}
1585
1586void thaw_secondary_cpus(void)
1587{
1588 int cpu, error;
1589
1590 /* Allow everyone to use the CPU hotplug again */
1591 cpu_maps_update_begin();
1592 __cpu_hotplug_enable();
1593 if (cpumask_empty(frozen_cpus))
1594 goto out;
1595
1596 pr_info("Enabling non-boot CPUs ...\n");
1597
1598 arch_thaw_secondary_cpus_begin();
1599
1600 for_each_cpu(cpu, frozen_cpus) {
1601 trace_suspend_resume(TPS("CPU_ON"), cpu, true);
1602 error = _cpu_up(cpu, 1, CPUHP_ONLINE);
1603 trace_suspend_resume(TPS("CPU_ON"), cpu, false);
1604 if (!error) {
1605 pr_info("CPU%d is up\n", cpu);
1606 continue;
1607 }
1608 pr_warn("Error taking CPU%d up: %d\n", cpu, error);
1609 }
1610
1611 arch_thaw_secondary_cpus_end();
1612
1613 cpumask_clear(frozen_cpus);
1614out:
1615 cpu_maps_update_done();
1616}
1617
1618static int __init alloc_frozen_cpus(void)
1619{
1620 if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
1621 return -ENOMEM;
1622 return 0;
1623}
1624core_initcall(alloc_frozen_cpus);
1625
1626/*
1627 * When callbacks for CPU hotplug notifications are being executed, we must
1628 * ensure that the state of the system with respect to the tasks being frozen
1629 * or not, as reported by the notification, remains unchanged *throughout the
1630 * duration* of the execution of the callbacks.
1631 * Hence we need to prevent the freezer from racing with regular CPU hotplug.
1632 *
1633 * This synchronization is implemented by mutually excluding regular CPU
1634 * hotplug and Suspend/Hibernate call paths by hooking onto the Suspend/
1635 * Hibernate notifications.
1636 */
1637static int
1638cpu_hotplug_pm_callback(struct notifier_block *nb,
1639 unsigned long action, void *ptr)
1640{
1641 switch (action) {
1642
1643 case PM_SUSPEND_PREPARE:
1644 case PM_HIBERNATION_PREPARE:
1645 cpu_hotplug_disable();
1646 break;
1647
1648 case PM_POST_SUSPEND:
1649 case PM_POST_HIBERNATION:
1650 cpu_hotplug_enable();
1651 break;
1652
1653 default:
1654 return NOTIFY_DONE;
1655 }
1656
1657 return NOTIFY_OK;
1658}
1659
1660
1661static int __init cpu_hotplug_pm_sync_init(void)
1662{
1663 /*
1664 * cpu_hotplug_pm_callback has higher priority than x86
1665 * bsp_pm_callback which depends on cpu_hotplug_pm_callback
1666 * to disable cpu hotplug to avoid cpu hotplug race.
1667 */
1668 pm_notifier(cpu_hotplug_pm_callback, 0);
1669 return 0;
1670}
1671core_initcall(cpu_hotplug_pm_sync_init);
1672
1673#endif /* CONFIG_PM_SLEEP_SMP */
1674
1675int __boot_cpu_id;
1676
1677#endif /* CONFIG_SMP */
1678
1679/* Boot processor state steps */
1680static struct cpuhp_step cpuhp_hp_states[] = {
1681 [CPUHP_OFFLINE] = {
1682 .name = "offline",
1683 .startup.single = NULL,
1684 .teardown.single = NULL,
1685 },
1686#ifdef CONFIG_SMP
1687 [CPUHP_CREATE_THREADS]= {
1688 .name = "threads:prepare",
1689 .startup.single = smpboot_create_threads,
1690 .teardown.single = NULL,
1691 .cant_stop = true,
1692 },
1693 [CPUHP_PERF_PREPARE] = {
1694 .name = "perf:prepare",
1695 .startup.single = perf_event_init_cpu,
1696 .teardown.single = perf_event_exit_cpu,
1697 },
1698 [CPUHP_RANDOM_PREPARE] = {
1699 .name = "random:prepare",
1700 .startup.single = random_prepare_cpu,
1701 .teardown.single = NULL,
1702 },
1703 [CPUHP_WORKQUEUE_PREP] = {
1704 .name = "workqueue:prepare",
1705 .startup.single = workqueue_prepare_cpu,
1706 .teardown.single = NULL,
1707 },
1708 [CPUHP_HRTIMERS_PREPARE] = {
1709 .name = "hrtimers:prepare",
1710 .startup.single = hrtimers_prepare_cpu,
1711 .teardown.single = hrtimers_dead_cpu,
1712 },
1713 [CPUHP_SMPCFD_PREPARE] = {
1714 .name = "smpcfd:prepare",
1715 .startup.single = smpcfd_prepare_cpu,
1716 .teardown.single = smpcfd_dead_cpu,
1717 },
1718 [CPUHP_RELAY_PREPARE] = {
1719 .name = "relay:prepare",
1720 .startup.single = relay_prepare_cpu,
1721 .teardown.single = NULL,
1722 },
1723 [CPUHP_SLAB_PREPARE] = {
1724 .name = "slab:prepare",
1725 .startup.single = slab_prepare_cpu,
1726 .teardown.single = slab_dead_cpu,
1727 },
1728 [CPUHP_RCUTREE_PREP] = {
1729 .name = "RCU/tree:prepare",
1730 .startup.single = rcutree_prepare_cpu,
1731 .teardown.single = rcutree_dead_cpu,
1732 },
1733 /*
1734 * On the tear-down path, timers_dead_cpu() must be invoked
1735 * before blk_mq_queue_reinit_notify() from notify_dead(),
1736 * otherwise a RCU stall occurs.
1737 */
1738 [CPUHP_TIMERS_PREPARE] = {
1739 .name = "timers:prepare",
1740 .startup.single = timers_prepare_cpu,
1741 .teardown.single = timers_dead_cpu,
1742 },
1743 /* Kicks the plugged cpu into life */
1744 [CPUHP_BRINGUP_CPU] = {
1745 .name = "cpu:bringup",
1746 .startup.single = bringup_cpu,
1747 .teardown.single = finish_cpu,
1748 .cant_stop = true,
1749 },
1750 /* Final state before CPU kills itself */
1751 [CPUHP_AP_IDLE_DEAD] = {
1752 .name = "idle:dead",
1753 },
1754 /*
1755 * Last state before CPU enters the idle loop to die. Transient state
1756 * for synchronization.
1757 */
1758 [CPUHP_AP_OFFLINE] = {
1759 .name = "ap:offline",
1760 .cant_stop = true,
1761 },
1762 /* First state is scheduler control. Interrupts are disabled */
1763 [CPUHP_AP_SCHED_STARTING] = {
1764 .name = "sched:starting",
1765 .startup.single = sched_cpu_starting,
1766 .teardown.single = sched_cpu_dying,
1767 },
1768 [CPUHP_AP_RCUTREE_DYING] = {
1769 .name = "RCU/tree:dying",
1770 .startup.single = NULL,
1771 .teardown.single = rcutree_dying_cpu,
1772 },
1773 [CPUHP_AP_SMPCFD_DYING] = {
1774 .name = "smpcfd:dying",
1775 .startup.single = NULL,
1776 .teardown.single = smpcfd_dying_cpu,
1777 },
1778 /* Entry state on starting. Interrupts enabled from here on. Transient
1779 * state for synchronsization */
1780 [CPUHP_AP_ONLINE] = {
1781 .name = "ap:online",
1782 },
1783 /*
1784 * Handled on control processor until the plugged processor manages
1785 * this itself.
1786 */
1787 [CPUHP_TEARDOWN_CPU] = {
1788 .name = "cpu:teardown",
1789 .startup.single = NULL,
1790 .teardown.single = takedown_cpu,
1791 .cant_stop = true,
1792 },
1793
1794 [CPUHP_AP_SCHED_WAIT_EMPTY] = {
1795 .name = "sched:waitempty",
1796 .startup.single = NULL,
1797 .teardown.single = sched_cpu_wait_empty,
1798 },
1799
1800 /* Handle smpboot threads park/unpark */
1801 [CPUHP_AP_SMPBOOT_THREADS] = {
1802 .name = "smpboot/threads:online",
1803 .startup.single = smpboot_unpark_threads,
1804 .teardown.single = smpboot_park_threads,
1805 },
1806 [CPUHP_AP_IRQ_AFFINITY_ONLINE] = {
1807 .name = "irq/affinity:online",
1808 .startup.single = irq_affinity_online_cpu,
1809 .teardown.single = NULL,
1810 },
1811 [CPUHP_AP_PERF_ONLINE] = {
1812 .name = "perf:online",
1813 .startup.single = perf_event_init_cpu,
1814 .teardown.single = perf_event_exit_cpu,
1815 },
1816 [CPUHP_AP_WATCHDOG_ONLINE] = {
1817 .name = "lockup_detector:online",
1818 .startup.single = lockup_detector_online_cpu,
1819 .teardown.single = lockup_detector_offline_cpu,
1820 },
1821 [CPUHP_AP_WORKQUEUE_ONLINE] = {
1822 .name = "workqueue:online",
1823 .startup.single = workqueue_online_cpu,
1824 .teardown.single = workqueue_offline_cpu,
1825 },
1826 [CPUHP_AP_RANDOM_ONLINE] = {
1827 .name = "random:online",
1828 .startup.single = random_online_cpu,
1829 .teardown.single = NULL,
1830 },
1831 [CPUHP_AP_RCUTREE_ONLINE] = {
1832 .name = "RCU/tree:online",
1833 .startup.single = rcutree_online_cpu,
1834 .teardown.single = rcutree_offline_cpu,
1835 },
1836#endif
1837 /*
1838 * The dynamically registered state space is here
1839 */
1840
1841#ifdef CONFIG_SMP
1842 /* Last state is scheduler control setting the cpu active */
1843 [CPUHP_AP_ACTIVE] = {
1844 .name = "sched:active",
1845 .startup.single = sched_cpu_activate,
1846 .teardown.single = sched_cpu_deactivate,
1847 },
1848#endif
1849
1850 /* CPU is fully up and running. */
1851 [CPUHP_ONLINE] = {
1852 .name = "online",
1853 .startup.single = NULL,
1854 .teardown.single = NULL,
1855 },
1856};
1857
1858/* Sanity check for callbacks */
1859static int cpuhp_cb_check(enum cpuhp_state state)
1860{
1861 if (state <= CPUHP_OFFLINE || state >= CPUHP_ONLINE)
1862 return -EINVAL;
1863 return 0;
1864}
1865
1866/*
1867 * Returns a free for dynamic slot assignment of the Online state. The states
1868 * are protected by the cpuhp_slot_states mutex and an empty slot is identified
1869 * by having no name assigned.
1870 */
1871static int cpuhp_reserve_state(enum cpuhp_state state)
1872{
1873 enum cpuhp_state i, end;
1874 struct cpuhp_step *step;
1875
1876 switch (state) {
1877 case CPUHP_AP_ONLINE_DYN:
1878 step = cpuhp_hp_states + CPUHP_AP_ONLINE_DYN;
1879 end = CPUHP_AP_ONLINE_DYN_END;
1880 break;
1881 case CPUHP_BP_PREPARE_DYN:
1882 step = cpuhp_hp_states + CPUHP_BP_PREPARE_DYN;
1883 end = CPUHP_BP_PREPARE_DYN_END;
1884 break;
1885 default:
1886 return -EINVAL;
1887 }
1888
1889 for (i = state; i <= end; i++, step++) {
1890 if (!step->name)
1891 return i;
1892 }
1893 WARN(1, "No more dynamic states available for CPU hotplug\n");
1894 return -ENOSPC;
1895}
1896
1897static int cpuhp_store_callbacks(enum cpuhp_state state, const char *name,
1898 int (*startup)(unsigned int cpu),
1899 int (*teardown)(unsigned int cpu),
1900 bool multi_instance)
1901{
1902 /* (Un)Install the callbacks for further cpu hotplug operations */
1903 struct cpuhp_step *sp;
1904 int ret = 0;
1905
1906 /*
1907 * If name is NULL, then the state gets removed.
1908 *
1909 * CPUHP_AP_ONLINE_DYN and CPUHP_BP_PREPARE_DYN are handed out on
1910 * the first allocation from these dynamic ranges, so the removal
1911 * would trigger a new allocation and clear the wrong (already
1912 * empty) state, leaving the callbacks of the to be cleared state
1913 * dangling, which causes wreckage on the next hotplug operation.
1914 */
1915 if (name && (state == CPUHP_AP_ONLINE_DYN ||
1916 state == CPUHP_BP_PREPARE_DYN)) {
1917 ret = cpuhp_reserve_state(state);
1918 if (ret < 0)
1919 return ret;
1920 state = ret;
1921 }
1922 sp = cpuhp_get_step(state);
1923 if (name && sp->name)
1924 return -EBUSY;
1925
1926 sp->startup.single = startup;
1927 sp->teardown.single = teardown;
1928 sp->name = name;
1929 sp->multi_instance = multi_instance;
1930 INIT_HLIST_HEAD(&sp->list);
1931 return ret;
1932}
1933
1934static void *cpuhp_get_teardown_cb(enum cpuhp_state state)
1935{
1936 return cpuhp_get_step(state)->teardown.single;
1937}
1938
1939/*
1940 * Call the startup/teardown function for a step either on the AP or
1941 * on the current CPU.
1942 */
1943static int cpuhp_issue_call(int cpu, enum cpuhp_state state, bool bringup,
1944 struct hlist_node *node)
1945{
1946 struct cpuhp_step *sp = cpuhp_get_step(state);
1947 int ret;
1948
1949 /*
1950 * If there's nothing to do, we done.
1951 * Relies on the union for multi_instance.
1952 */
1953 if (cpuhp_step_empty(bringup, sp))
1954 return 0;
1955 /*
1956 * The non AP bound callbacks can fail on bringup. On teardown
1957 * e.g. module removal we crash for now.
1958 */
1959#ifdef CONFIG_SMP
1960 if (cpuhp_is_ap_state(state))
1961 ret = cpuhp_invoke_ap_callback(cpu, state, bringup, node);
1962 else
1963 ret = cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
1964#else
1965 ret = cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
1966#endif
1967 BUG_ON(ret && !bringup);
1968 return ret;
1969}
1970
1971/*
1972 * Called from __cpuhp_setup_state on a recoverable failure.
1973 *
1974 * Note: The teardown callbacks for rollback are not allowed to fail!
1975 */
1976static void cpuhp_rollback_install(int failedcpu, enum cpuhp_state state,
1977 struct hlist_node *node)
1978{
1979 int cpu;
1980
1981 /* Roll back the already executed steps on the other cpus */
1982 for_each_present_cpu(cpu) {
1983 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1984 int cpustate = st->state;
1985
1986 if (cpu >= failedcpu)
1987 break;
1988
1989 /* Did we invoke the startup call on that cpu ? */
1990 if (cpustate >= state)
1991 cpuhp_issue_call(cpu, state, false, node);
1992 }
1993}
1994
1995int __cpuhp_state_add_instance_cpuslocked(enum cpuhp_state state,
1996 struct hlist_node *node,
1997 bool invoke)
1998{
1999 struct cpuhp_step *sp;
2000 int cpu;
2001 int ret;
2002
2003 lockdep_assert_cpus_held();
2004
2005 sp = cpuhp_get_step(state);
2006 if (sp->multi_instance == false)
2007 return -EINVAL;
2008
2009 mutex_lock(&cpuhp_state_mutex);
2010
2011 if (!invoke || !sp->startup.multi)
2012 goto add_node;
2013
2014 /*
2015 * Try to call the startup callback for each present cpu
2016 * depending on the hotplug state of the cpu.
2017 */
2018 for_each_present_cpu(cpu) {
2019 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
2020 int cpustate = st->state;
2021
2022 if (cpustate < state)
2023 continue;
2024
2025 ret = cpuhp_issue_call(cpu, state, true, node);
2026 if (ret) {
2027 if (sp->teardown.multi)
2028 cpuhp_rollback_install(cpu, state, node);
2029 goto unlock;
2030 }
2031 }
2032add_node:
2033 ret = 0;
2034 hlist_add_head(node, &sp->list);
2035unlock:
2036 mutex_unlock(&cpuhp_state_mutex);
2037 return ret;
2038}
2039
2040int __cpuhp_state_add_instance(enum cpuhp_state state, struct hlist_node *node,
2041 bool invoke)
2042{
2043 int ret;
2044
2045 cpus_read_lock();
2046 ret = __cpuhp_state_add_instance_cpuslocked(state, node, invoke);
2047 cpus_read_unlock();
2048 return ret;
2049}
2050EXPORT_SYMBOL_GPL(__cpuhp_state_add_instance);
2051
2052/**
2053 * __cpuhp_setup_state_cpuslocked - Setup the callbacks for an hotplug machine state
2054 * @state: The state to setup
2055 * @name: Name of the step
2056 * @invoke: If true, the startup function is invoked for cpus where
2057 * cpu state >= @state
2058 * @startup: startup callback function
2059 * @teardown: teardown callback function
2060 * @multi_instance: State is set up for multiple instances which get
2061 * added afterwards.
2062 *
2063 * The caller needs to hold cpus read locked while calling this function.
2064 * Return:
2065 * On success:
2066 * Positive state number if @state is CPUHP_AP_ONLINE_DYN;
2067 * 0 for all other states
2068 * On failure: proper (negative) error code
2069 */
2070int __cpuhp_setup_state_cpuslocked(enum cpuhp_state state,
2071 const char *name, bool invoke,
2072 int (*startup)(unsigned int cpu),
2073 int (*teardown)(unsigned int cpu),
2074 bool multi_instance)
2075{
2076 int cpu, ret = 0;
2077 bool dynstate;
2078
2079 lockdep_assert_cpus_held();
2080
2081 if (cpuhp_cb_check(state) || !name)
2082 return -EINVAL;
2083
2084 mutex_lock(&cpuhp_state_mutex);
2085
2086 ret = cpuhp_store_callbacks(state, name, startup, teardown,
2087 multi_instance);
2088
2089 dynstate = state == CPUHP_AP_ONLINE_DYN;
2090 if (ret > 0 && dynstate) {
2091 state = ret;
2092 ret = 0;
2093 }
2094
2095 if (ret || !invoke || !startup)
2096 goto out;
2097
2098 /*
2099 * Try to call the startup callback for each present cpu
2100 * depending on the hotplug state of the cpu.
2101 */
2102 for_each_present_cpu(cpu) {
2103 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
2104 int cpustate = st->state;
2105
2106 if (cpustate < state)
2107 continue;
2108
2109 ret = cpuhp_issue_call(cpu, state, true, NULL);
2110 if (ret) {
2111 if (teardown)
2112 cpuhp_rollback_install(cpu, state, NULL);
2113 cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
2114 goto out;
2115 }
2116 }
2117out:
2118 mutex_unlock(&cpuhp_state_mutex);
2119 /*
2120 * If the requested state is CPUHP_AP_ONLINE_DYN, return the
2121 * dynamically allocated state in case of success.
2122 */
2123 if (!ret && dynstate)
2124 return state;
2125 return ret;
2126}
2127EXPORT_SYMBOL(__cpuhp_setup_state_cpuslocked);
2128
2129int __cpuhp_setup_state(enum cpuhp_state state,
2130 const char *name, bool invoke,
2131 int (*startup)(unsigned int cpu),
2132 int (*teardown)(unsigned int cpu),
2133 bool multi_instance)
2134{
2135 int ret;
2136
2137 cpus_read_lock();
2138 ret = __cpuhp_setup_state_cpuslocked(state, name, invoke, startup,
2139 teardown, multi_instance);
2140 cpus_read_unlock();
2141 return ret;
2142}
2143EXPORT_SYMBOL(__cpuhp_setup_state);
2144
2145int __cpuhp_state_remove_instance(enum cpuhp_state state,
2146 struct hlist_node *node, bool invoke)
2147{
2148 struct cpuhp_step *sp = cpuhp_get_step(state);
2149 int cpu;
2150
2151 BUG_ON(cpuhp_cb_check(state));
2152
2153 if (!sp->multi_instance)
2154 return -EINVAL;
2155
2156 cpus_read_lock();
2157 mutex_lock(&cpuhp_state_mutex);
2158
2159 if (!invoke || !cpuhp_get_teardown_cb(state))
2160 goto remove;
2161 /*
2162 * Call the teardown callback for each present cpu depending
2163 * on the hotplug state of the cpu. This function is not
2164 * allowed to fail currently!
2165 */
2166 for_each_present_cpu(cpu) {
2167 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
2168 int cpustate = st->state;
2169
2170 if (cpustate >= state)
2171 cpuhp_issue_call(cpu, state, false, node);
2172 }
2173
2174remove:
2175 hlist_del(node);
2176 mutex_unlock(&cpuhp_state_mutex);
2177 cpus_read_unlock();
2178
2179 return 0;
2180}
2181EXPORT_SYMBOL_GPL(__cpuhp_state_remove_instance);
2182
2183/**
2184 * __cpuhp_remove_state_cpuslocked - Remove the callbacks for an hotplug machine state
2185 * @state: The state to remove
2186 * @invoke: If true, the teardown function is invoked for cpus where
2187 * cpu state >= @state
2188 *
2189 * The caller needs to hold cpus read locked while calling this function.
2190 * The teardown callback is currently not allowed to fail. Think
2191 * about module removal!
2192 */
2193void __cpuhp_remove_state_cpuslocked(enum cpuhp_state state, bool invoke)
2194{
2195 struct cpuhp_step *sp = cpuhp_get_step(state);
2196 int cpu;
2197
2198 BUG_ON(cpuhp_cb_check(state));
2199
2200 lockdep_assert_cpus_held();
2201
2202 mutex_lock(&cpuhp_state_mutex);
2203 if (sp->multi_instance) {
2204 WARN(!hlist_empty(&sp->list),
2205 "Error: Removing state %d which has instances left.\n",
2206 state);
2207 goto remove;
2208 }
2209
2210 if (!invoke || !cpuhp_get_teardown_cb(state))
2211 goto remove;
2212
2213 /*
2214 * Call the teardown callback for each present cpu depending
2215 * on the hotplug state of the cpu. This function is not
2216 * allowed to fail currently!
2217 */
2218 for_each_present_cpu(cpu) {
2219 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
2220 int cpustate = st->state;
2221
2222 if (cpustate >= state)
2223 cpuhp_issue_call(cpu, state, false, NULL);
2224 }
2225remove:
2226 cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
2227 mutex_unlock(&cpuhp_state_mutex);
2228}
2229EXPORT_SYMBOL(__cpuhp_remove_state_cpuslocked);
2230
2231void __cpuhp_remove_state(enum cpuhp_state state, bool invoke)
2232{
2233 cpus_read_lock();
2234 __cpuhp_remove_state_cpuslocked(state, invoke);
2235 cpus_read_unlock();
2236}
2237EXPORT_SYMBOL(__cpuhp_remove_state);
2238
2239#ifdef CONFIG_HOTPLUG_SMT
2240static void cpuhp_offline_cpu_device(unsigned int cpu)
2241{
2242 struct device *dev = get_cpu_device(cpu);
2243
2244 dev->offline = true;
2245 /* Tell user space about the state change */
2246 kobject_uevent(&dev->kobj, KOBJ_OFFLINE);
2247}
2248
2249static void cpuhp_online_cpu_device(unsigned int cpu)
2250{
2251 struct device *dev = get_cpu_device(cpu);
2252
2253 dev->offline = false;
2254 /* Tell user space about the state change */
2255 kobject_uevent(&dev->kobj, KOBJ_ONLINE);
2256}
2257
2258int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval)
2259{
2260 int cpu, ret = 0;
2261
2262 cpu_maps_update_begin();
2263 for_each_online_cpu(cpu) {
2264 if (topology_is_primary_thread(cpu))
2265 continue;
2266 ret = cpu_down_maps_locked(cpu, CPUHP_OFFLINE);
2267 if (ret)
2268 break;
2269 /*
2270 * As this needs to hold the cpu maps lock it's impossible
2271 * to call device_offline() because that ends up calling
2272 * cpu_down() which takes cpu maps lock. cpu maps lock
2273 * needs to be held as this might race against in kernel
2274 * abusers of the hotplug machinery (thermal management).
2275 *
2276 * So nothing would update device:offline state. That would
2277 * leave the sysfs entry stale and prevent onlining after
2278 * smt control has been changed to 'off' again. This is
2279 * called under the sysfs hotplug lock, so it is properly
2280 * serialized against the regular offline usage.
2281 */
2282 cpuhp_offline_cpu_device(cpu);
2283 }
2284 if (!ret)
2285 cpu_smt_control = ctrlval;
2286 cpu_maps_update_done();
2287 return ret;
2288}
2289
2290int cpuhp_smt_enable(void)
2291{
2292 int cpu, ret = 0;
2293
2294 cpu_maps_update_begin();
2295 cpu_smt_control = CPU_SMT_ENABLED;
2296 for_each_present_cpu(cpu) {
2297 /* Skip online CPUs and CPUs on offline nodes */
2298 if (cpu_online(cpu) || !node_online(cpu_to_node(cpu)))
2299 continue;
2300 ret = _cpu_up(cpu, 0, CPUHP_ONLINE);
2301 if (ret)
2302 break;
2303 /* See comment in cpuhp_smt_disable() */
2304 cpuhp_online_cpu_device(cpu);
2305 }
2306 cpu_maps_update_done();
2307 return ret;
2308}
2309#endif
2310
2311#if defined(CONFIG_SYSFS) && defined(CONFIG_HOTPLUG_CPU)
2312static ssize_t state_show(struct device *dev,
2313 struct device_attribute *attr, char *buf)
2314{
2315 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2316
2317 return sprintf(buf, "%d\n", st->state);
2318}
2319static DEVICE_ATTR_RO(state);
2320
2321static ssize_t target_store(struct device *dev, struct device_attribute *attr,
2322 const char *buf, size_t count)
2323{
2324 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2325 struct cpuhp_step *sp;
2326 int target, ret;
2327
2328 ret = kstrtoint(buf, 10, &target);
2329 if (ret)
2330 return ret;
2331
2332#ifdef CONFIG_CPU_HOTPLUG_STATE_CONTROL
2333 if (target < CPUHP_OFFLINE || target > CPUHP_ONLINE)
2334 return -EINVAL;
2335#else
2336 if (target != CPUHP_OFFLINE && target != CPUHP_ONLINE)
2337 return -EINVAL;
2338#endif
2339
2340 ret = lock_device_hotplug_sysfs();
2341 if (ret)
2342 return ret;
2343
2344 mutex_lock(&cpuhp_state_mutex);
2345 sp = cpuhp_get_step(target);
2346 ret = !sp->name || sp->cant_stop ? -EINVAL : 0;
2347 mutex_unlock(&cpuhp_state_mutex);
2348 if (ret)
2349 goto out;
2350
2351 if (st->state < target)
2352 ret = cpu_up(dev->id, target);
2353 else if (st->state > target)
2354 ret = cpu_down(dev->id, target);
2355 else if (WARN_ON(st->target != target))
2356 st->target = target;
2357out:
2358 unlock_device_hotplug();
2359 return ret ? ret : count;
2360}
2361
2362static ssize_t target_show(struct device *dev,
2363 struct device_attribute *attr, char *buf)
2364{
2365 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2366
2367 return sprintf(buf, "%d\n", st->target);
2368}
2369static DEVICE_ATTR_RW(target);
2370
2371static ssize_t fail_store(struct device *dev, struct device_attribute *attr,
2372 const char *buf, size_t count)
2373{
2374 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2375 struct cpuhp_step *sp;
2376 int fail, ret;
2377
2378 ret = kstrtoint(buf, 10, &fail);
2379 if (ret)
2380 return ret;
2381
2382 if (fail == CPUHP_INVALID) {
2383 st->fail = fail;
2384 return count;
2385 }
2386
2387 if (fail < CPUHP_OFFLINE || fail > CPUHP_ONLINE)
2388 return -EINVAL;
2389
2390 /*
2391 * Cannot fail STARTING/DYING callbacks.
2392 */
2393 if (cpuhp_is_atomic_state(fail))
2394 return -EINVAL;
2395
2396 /*
2397 * DEAD callbacks cannot fail...
2398 * ... neither can CPUHP_BRINGUP_CPU during hotunplug. The latter
2399 * triggering STARTING callbacks, a failure in this state would
2400 * hinder rollback.
2401 */
2402 if (fail <= CPUHP_BRINGUP_CPU && st->state > CPUHP_BRINGUP_CPU)
2403 return -EINVAL;
2404
2405 /*
2406 * Cannot fail anything that doesn't have callbacks.
2407 */
2408 mutex_lock(&cpuhp_state_mutex);
2409 sp = cpuhp_get_step(fail);
2410 if (!sp->startup.single && !sp->teardown.single)
2411 ret = -EINVAL;
2412 mutex_unlock(&cpuhp_state_mutex);
2413 if (ret)
2414 return ret;
2415
2416 st->fail = fail;
2417
2418 return count;
2419}
2420
2421static ssize_t fail_show(struct device *dev,
2422 struct device_attribute *attr, char *buf)
2423{
2424 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2425
2426 return sprintf(buf, "%d\n", st->fail);
2427}
2428
2429static DEVICE_ATTR_RW(fail);
2430
2431static struct attribute *cpuhp_cpu_attrs[] = {
2432 &dev_attr_state.attr,
2433 &dev_attr_target.attr,
2434 &dev_attr_fail.attr,
2435 NULL
2436};
2437
2438static const struct attribute_group cpuhp_cpu_attr_group = {
2439 .attrs = cpuhp_cpu_attrs,
2440 .name = "hotplug",
2441 NULL
2442};
2443
2444static ssize_t states_show(struct device *dev,
2445 struct device_attribute *attr, char *buf)
2446{
2447 ssize_t cur, res = 0;
2448 int i;
2449
2450 mutex_lock(&cpuhp_state_mutex);
2451 for (i = CPUHP_OFFLINE; i <= CPUHP_ONLINE; i++) {
2452 struct cpuhp_step *sp = cpuhp_get_step(i);
2453
2454 if (sp->name) {
2455 cur = sprintf(buf, "%3d: %s\n", i, sp->name);
2456 buf += cur;
2457 res += cur;
2458 }
2459 }
2460 mutex_unlock(&cpuhp_state_mutex);
2461 return res;
2462}
2463static DEVICE_ATTR_RO(states);
2464
2465static struct attribute *cpuhp_cpu_root_attrs[] = {
2466 &dev_attr_states.attr,
2467 NULL
2468};
2469
2470static const struct attribute_group cpuhp_cpu_root_attr_group = {
2471 .attrs = cpuhp_cpu_root_attrs,
2472 .name = "hotplug",
2473 NULL
2474};
2475
2476#ifdef CONFIG_HOTPLUG_SMT
2477
2478static ssize_t
2479__store_smt_control(struct device *dev, struct device_attribute *attr,
2480 const char *buf, size_t count)
2481{
2482 int ctrlval, ret;
2483
2484 if (sysfs_streq(buf, "on"))
2485 ctrlval = CPU_SMT_ENABLED;
2486 else if (sysfs_streq(buf, "off"))
2487 ctrlval = CPU_SMT_DISABLED;
2488 else if (sysfs_streq(buf, "forceoff"))
2489 ctrlval = CPU_SMT_FORCE_DISABLED;
2490 else
2491 return -EINVAL;
2492
2493 if (cpu_smt_control == CPU_SMT_FORCE_DISABLED)
2494 return -EPERM;
2495
2496 if (cpu_smt_control == CPU_SMT_NOT_SUPPORTED)
2497 return -ENODEV;
2498
2499 ret = lock_device_hotplug_sysfs();
2500 if (ret)
2501 return ret;
2502
2503 if (ctrlval != cpu_smt_control) {
2504 switch (ctrlval) {
2505 case CPU_SMT_ENABLED:
2506 ret = cpuhp_smt_enable();
2507 break;
2508 case CPU_SMT_DISABLED:
2509 case CPU_SMT_FORCE_DISABLED:
2510 ret = cpuhp_smt_disable(ctrlval);
2511 break;
2512 }
2513 }
2514
2515 unlock_device_hotplug();
2516 return ret ? ret : count;
2517}
2518
2519#else /* !CONFIG_HOTPLUG_SMT */
2520static ssize_t
2521__store_smt_control(struct device *dev, struct device_attribute *attr,
2522 const char *buf, size_t count)
2523{
2524 return -ENODEV;
2525}
2526#endif /* CONFIG_HOTPLUG_SMT */
2527
2528static const char *smt_states[] = {
2529 [CPU_SMT_ENABLED] = "on",
2530 [CPU_SMT_DISABLED] = "off",
2531 [CPU_SMT_FORCE_DISABLED] = "forceoff",
2532 [CPU_SMT_NOT_SUPPORTED] = "notsupported",
2533 [CPU_SMT_NOT_IMPLEMENTED] = "notimplemented",
2534};
2535
2536static ssize_t control_show(struct device *dev,
2537 struct device_attribute *attr, char *buf)
2538{
2539 const char *state = smt_states[cpu_smt_control];
2540
2541 return snprintf(buf, PAGE_SIZE - 2, "%s\n", state);
2542}
2543
2544static ssize_t control_store(struct device *dev, struct device_attribute *attr,
2545 const char *buf, size_t count)
2546{
2547 return __store_smt_control(dev, attr, buf, count);
2548}
2549static DEVICE_ATTR_RW(control);
2550
2551static ssize_t active_show(struct device *dev,
2552 struct device_attribute *attr, char *buf)
2553{
2554 return snprintf(buf, PAGE_SIZE - 2, "%d\n", sched_smt_active());
2555}
2556static DEVICE_ATTR_RO(active);
2557
2558static struct attribute *cpuhp_smt_attrs[] = {
2559 &dev_attr_control.attr,
2560 &dev_attr_active.attr,
2561 NULL
2562};
2563
2564static const struct attribute_group cpuhp_smt_attr_group = {
2565 .attrs = cpuhp_smt_attrs,
2566 .name = "smt",
2567 NULL
2568};
2569
2570static int __init cpu_smt_sysfs_init(void)
2571{
2572 return sysfs_create_group(&cpu_subsys.dev_root->kobj,
2573 &cpuhp_smt_attr_group);
2574}
2575
2576static int __init cpuhp_sysfs_init(void)
2577{
2578 int cpu, ret;
2579
2580 ret = cpu_smt_sysfs_init();
2581 if (ret)
2582 return ret;
2583
2584 ret = sysfs_create_group(&cpu_subsys.dev_root->kobj,
2585 &cpuhp_cpu_root_attr_group);
2586 if (ret)
2587 return ret;
2588
2589 for_each_possible_cpu(cpu) {
2590 struct device *dev = get_cpu_device(cpu);
2591
2592 if (!dev)
2593 continue;
2594 ret = sysfs_create_group(&dev->kobj, &cpuhp_cpu_attr_group);
2595 if (ret)
2596 return ret;
2597 }
2598 return 0;
2599}
2600device_initcall(cpuhp_sysfs_init);
2601#endif /* CONFIG_SYSFS && CONFIG_HOTPLUG_CPU */
2602
2603/*
2604 * cpu_bit_bitmap[] is a special, "compressed" data structure that
2605 * represents all NR_CPUS bits binary values of 1<<nr.
2606 *
2607 * It is used by cpumask_of() to get a constant address to a CPU
2608 * mask value that has a single bit set only.
2609 */
2610
2611/* cpu_bit_bitmap[0] is empty - so we can back into it */
2612#define MASK_DECLARE_1(x) [x+1][0] = (1UL << (x))
2613#define MASK_DECLARE_2(x) MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
2614#define MASK_DECLARE_4(x) MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
2615#define MASK_DECLARE_8(x) MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
2616
2617const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
2618
2619 MASK_DECLARE_8(0), MASK_DECLARE_8(8),
2620 MASK_DECLARE_8(16), MASK_DECLARE_8(24),
2621#if BITS_PER_LONG > 32
2622 MASK_DECLARE_8(32), MASK_DECLARE_8(40),
2623 MASK_DECLARE_8(48), MASK_DECLARE_8(56),
2624#endif
2625};
2626EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
2627
2628const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
2629EXPORT_SYMBOL(cpu_all_bits);
2630
2631#ifdef CONFIG_INIT_ALL_POSSIBLE
2632struct cpumask __cpu_possible_mask __read_mostly
2633 = {CPU_BITS_ALL};
2634#else
2635struct cpumask __cpu_possible_mask __read_mostly;
2636#endif
2637EXPORT_SYMBOL(__cpu_possible_mask);
2638
2639struct cpumask __cpu_online_mask __read_mostly;
2640EXPORT_SYMBOL(__cpu_online_mask);
2641
2642struct cpumask __cpu_present_mask __read_mostly;
2643EXPORT_SYMBOL(__cpu_present_mask);
2644
2645struct cpumask __cpu_active_mask __read_mostly;
2646EXPORT_SYMBOL(__cpu_active_mask);
2647
2648struct cpumask __cpu_dying_mask __read_mostly;
2649EXPORT_SYMBOL(__cpu_dying_mask);
2650
2651atomic_t __num_online_cpus __read_mostly;
2652EXPORT_SYMBOL(__num_online_cpus);
2653
2654void init_cpu_present(const struct cpumask *src)
2655{
2656 cpumask_copy(&__cpu_present_mask, src);
2657}
2658
2659void init_cpu_possible(const struct cpumask *src)
2660{
2661 cpumask_copy(&__cpu_possible_mask, src);
2662}
2663
2664void init_cpu_online(const struct cpumask *src)
2665{
2666 cpumask_copy(&__cpu_online_mask, src);
2667}
2668
2669void set_cpu_online(unsigned int cpu, bool online)
2670{
2671 /*
2672 * atomic_inc/dec() is required to handle the horrid abuse of this
2673 * function by the reboot and kexec code which invoke it from
2674 * IPI/NMI broadcasts when shutting down CPUs. Invocation from
2675 * regular CPU hotplug is properly serialized.
2676 *
2677 * Note, that the fact that __num_online_cpus is of type atomic_t
2678 * does not protect readers which are not serialized against
2679 * concurrent hotplug operations.
2680 */
2681 if (online) {
2682 if (!cpumask_test_and_set_cpu(cpu, &__cpu_online_mask))
2683 atomic_inc(&__num_online_cpus);
2684 } else {
2685 if (cpumask_test_and_clear_cpu(cpu, &__cpu_online_mask))
2686 atomic_dec(&__num_online_cpus);
2687 }
2688}
2689
2690/*
2691 * Activate the first processor.
2692 */
2693void __init boot_cpu_init(void)
2694{
2695 int cpu = smp_processor_id();
2696
2697 /* Mark the boot cpu "present", "online" etc for SMP and UP case */
2698 set_cpu_online(cpu, true);
2699 set_cpu_active(cpu, true);
2700 set_cpu_present(cpu, true);
2701 set_cpu_possible(cpu, true);
2702
2703#ifdef CONFIG_SMP
2704 __boot_cpu_id = cpu;
2705#endif
2706}
2707
2708/*
2709 * Must be called _AFTER_ setting up the per_cpu areas
2710 */
2711void __init boot_cpu_hotplug_init(void)
2712{
2713#ifdef CONFIG_SMP
2714 cpumask_set_cpu(smp_processor_id(), &cpus_booted_once_mask);
2715#endif
2716 this_cpu_write(cpuhp_state.state, CPUHP_ONLINE);
2717 this_cpu_write(cpuhp_state.target, CPUHP_ONLINE);
2718}
2719
2720/*
2721 * These are used for a global "mitigations=" cmdline option for toggling
2722 * optional CPU mitigations.
2723 */
2724enum cpu_mitigations {
2725 CPU_MITIGATIONS_OFF,
2726 CPU_MITIGATIONS_AUTO,
2727 CPU_MITIGATIONS_AUTO_NOSMT,
2728};
2729
2730static enum cpu_mitigations cpu_mitigations __ro_after_init =
2731 CPU_MITIGATIONS_AUTO;
2732
2733static int __init mitigations_parse_cmdline(char *arg)
2734{
2735 if (!strcmp(arg, "off"))
2736 cpu_mitigations = CPU_MITIGATIONS_OFF;
2737 else if (!strcmp(arg, "auto"))
2738 cpu_mitigations = CPU_MITIGATIONS_AUTO;
2739 else if (!strcmp(arg, "auto,nosmt"))
2740 cpu_mitigations = CPU_MITIGATIONS_AUTO_NOSMT;
2741 else
2742 pr_crit("Unsupported mitigations=%s, system may still be vulnerable\n",
2743 arg);
2744
2745 return 0;
2746}
2747early_param("mitigations", mitigations_parse_cmdline);
2748
2749/* mitigations=off */
2750bool cpu_mitigations_off(void)
2751{
2752 return cpu_mitigations == CPU_MITIGATIONS_OFF;
2753}
2754EXPORT_SYMBOL_GPL(cpu_mitigations_off);
2755
2756/* mitigations=auto,nosmt */
2757bool cpu_mitigations_auto_nosmt(void)
2758{
2759 return cpu_mitigations == CPU_MITIGATIONS_AUTO_NOSMT;
2760}
2761EXPORT_SYMBOL_GPL(cpu_mitigations_auto_nosmt);
1/* CPU control.
2 * (C) 2001, 2002, 2003, 2004 Rusty Russell
3 *
4 * This code is licenced under the GPL.
5 */
6#include <linux/sched/mm.h>
7#include <linux/proc_fs.h>
8#include <linux/smp.h>
9#include <linux/init.h>
10#include <linux/notifier.h>
11#include <linux/sched/signal.h>
12#include <linux/sched/hotplug.h>
13#include <linux/sched/isolation.h>
14#include <linux/sched/task.h>
15#include <linux/sched/smt.h>
16#include <linux/unistd.h>
17#include <linux/cpu.h>
18#include <linux/oom.h>
19#include <linux/rcupdate.h>
20#include <linux/delay.h>
21#include <linux/export.h>
22#include <linux/bug.h>
23#include <linux/kthread.h>
24#include <linux/stop_machine.h>
25#include <linux/mutex.h>
26#include <linux/gfp.h>
27#include <linux/suspend.h>
28#include <linux/lockdep.h>
29#include <linux/tick.h>
30#include <linux/irq.h>
31#include <linux/nmi.h>
32#include <linux/smpboot.h>
33#include <linux/relay.h>
34#include <linux/slab.h>
35#include <linux/scs.h>
36#include <linux/percpu-rwsem.h>
37#include <linux/cpuset.h>
38#include <linux/random.h>
39#include <linux/cc_platform.h>
40
41#include <trace/events/power.h>
42#define CREATE_TRACE_POINTS
43#include <trace/events/cpuhp.h>
44
45#include "smpboot.h"
46
47/**
48 * struct cpuhp_cpu_state - Per cpu hotplug state storage
49 * @state: The current cpu state
50 * @target: The target state
51 * @fail: Current CPU hotplug callback state
52 * @thread: Pointer to the hotplug thread
53 * @should_run: Thread should execute
54 * @rollback: Perform a rollback
55 * @single: Single callback invocation
56 * @bringup: Single callback bringup or teardown selector
57 * @node: Remote CPU node; for multi-instance, do a
58 * single entry callback for install/remove
59 * @last: For multi-instance rollback, remember how far we got
60 * @cb_state: The state for a single callback (install/uninstall)
61 * @result: Result of the operation
62 * @ap_sync_state: State for AP synchronization
63 * @done_up: Signal completion to the issuer of the task for cpu-up
64 * @done_down: Signal completion to the issuer of the task for cpu-down
65 */
66struct cpuhp_cpu_state {
67 enum cpuhp_state state;
68 enum cpuhp_state target;
69 enum cpuhp_state fail;
70#ifdef CONFIG_SMP
71 struct task_struct *thread;
72 bool should_run;
73 bool rollback;
74 bool single;
75 bool bringup;
76 struct hlist_node *node;
77 struct hlist_node *last;
78 enum cpuhp_state cb_state;
79 int result;
80 atomic_t ap_sync_state;
81 struct completion done_up;
82 struct completion done_down;
83#endif
84};
85
86static DEFINE_PER_CPU(struct cpuhp_cpu_state, cpuhp_state) = {
87 .fail = CPUHP_INVALID,
88};
89
90#ifdef CONFIG_SMP
91cpumask_t cpus_booted_once_mask;
92#endif
93
94#if defined(CONFIG_LOCKDEP) && defined(CONFIG_SMP)
95static struct lockdep_map cpuhp_state_up_map =
96 STATIC_LOCKDEP_MAP_INIT("cpuhp_state-up", &cpuhp_state_up_map);
97static struct lockdep_map cpuhp_state_down_map =
98 STATIC_LOCKDEP_MAP_INIT("cpuhp_state-down", &cpuhp_state_down_map);
99
100
101static inline void cpuhp_lock_acquire(bool bringup)
102{
103 lock_map_acquire(bringup ? &cpuhp_state_up_map : &cpuhp_state_down_map);
104}
105
106static inline void cpuhp_lock_release(bool bringup)
107{
108 lock_map_release(bringup ? &cpuhp_state_up_map : &cpuhp_state_down_map);
109}
110#else
111
112static inline void cpuhp_lock_acquire(bool bringup) { }
113static inline void cpuhp_lock_release(bool bringup) { }
114
115#endif
116
117/**
118 * struct cpuhp_step - Hotplug state machine step
119 * @name: Name of the step
120 * @startup: Startup function of the step
121 * @teardown: Teardown function of the step
122 * @cant_stop: Bringup/teardown can't be stopped at this step
123 * @multi_instance: State has multiple instances which get added afterwards
124 */
125struct cpuhp_step {
126 const char *name;
127 union {
128 int (*single)(unsigned int cpu);
129 int (*multi)(unsigned int cpu,
130 struct hlist_node *node);
131 } startup;
132 union {
133 int (*single)(unsigned int cpu);
134 int (*multi)(unsigned int cpu,
135 struct hlist_node *node);
136 } teardown;
137 /* private: */
138 struct hlist_head list;
139 /* public: */
140 bool cant_stop;
141 bool multi_instance;
142};
143
144static DEFINE_MUTEX(cpuhp_state_mutex);
145static struct cpuhp_step cpuhp_hp_states[];
146
147static struct cpuhp_step *cpuhp_get_step(enum cpuhp_state state)
148{
149 return cpuhp_hp_states + state;
150}
151
152static bool cpuhp_step_empty(bool bringup, struct cpuhp_step *step)
153{
154 return bringup ? !step->startup.single : !step->teardown.single;
155}
156
157/**
158 * cpuhp_invoke_callback - Invoke the callbacks for a given state
159 * @cpu: The cpu for which the callback should be invoked
160 * @state: The state to do callbacks for
161 * @bringup: True if the bringup callback should be invoked
162 * @node: For multi-instance, do a single entry callback for install/remove
163 * @lastp: For multi-instance rollback, remember how far we got
164 *
165 * Called from cpu hotplug and from the state register machinery.
166 *
167 * Return: %0 on success or a negative errno code
168 */
169static int cpuhp_invoke_callback(unsigned int cpu, enum cpuhp_state state,
170 bool bringup, struct hlist_node *node,
171 struct hlist_node **lastp)
172{
173 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
174 struct cpuhp_step *step = cpuhp_get_step(state);
175 int (*cbm)(unsigned int cpu, struct hlist_node *node);
176 int (*cb)(unsigned int cpu);
177 int ret, cnt;
178
179 if (st->fail == state) {
180 st->fail = CPUHP_INVALID;
181 return -EAGAIN;
182 }
183
184 if (cpuhp_step_empty(bringup, step)) {
185 WARN_ON_ONCE(1);
186 return 0;
187 }
188
189 if (!step->multi_instance) {
190 WARN_ON_ONCE(lastp && *lastp);
191 cb = bringup ? step->startup.single : step->teardown.single;
192
193 trace_cpuhp_enter(cpu, st->target, state, cb);
194 ret = cb(cpu);
195 trace_cpuhp_exit(cpu, st->state, state, ret);
196 return ret;
197 }
198 cbm = bringup ? step->startup.multi : step->teardown.multi;
199
200 /* Single invocation for instance add/remove */
201 if (node) {
202 WARN_ON_ONCE(lastp && *lastp);
203 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
204 ret = cbm(cpu, node);
205 trace_cpuhp_exit(cpu, st->state, state, ret);
206 return ret;
207 }
208
209 /* State transition. Invoke on all instances */
210 cnt = 0;
211 hlist_for_each(node, &step->list) {
212 if (lastp && node == *lastp)
213 break;
214
215 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
216 ret = cbm(cpu, node);
217 trace_cpuhp_exit(cpu, st->state, state, ret);
218 if (ret) {
219 if (!lastp)
220 goto err;
221
222 *lastp = node;
223 return ret;
224 }
225 cnt++;
226 }
227 if (lastp)
228 *lastp = NULL;
229 return 0;
230err:
231 /* Rollback the instances if one failed */
232 cbm = !bringup ? step->startup.multi : step->teardown.multi;
233 if (!cbm)
234 return ret;
235
236 hlist_for_each(node, &step->list) {
237 if (!cnt--)
238 break;
239
240 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
241 ret = cbm(cpu, node);
242 trace_cpuhp_exit(cpu, st->state, state, ret);
243 /*
244 * Rollback must not fail,
245 */
246 WARN_ON_ONCE(ret);
247 }
248 return ret;
249}
250
251#ifdef CONFIG_SMP
252static bool cpuhp_is_ap_state(enum cpuhp_state state)
253{
254 /*
255 * The extra check for CPUHP_TEARDOWN_CPU is only for documentation
256 * purposes as that state is handled explicitly in cpu_down.
257 */
258 return state > CPUHP_BRINGUP_CPU && state != CPUHP_TEARDOWN_CPU;
259}
260
261static inline void wait_for_ap_thread(struct cpuhp_cpu_state *st, bool bringup)
262{
263 struct completion *done = bringup ? &st->done_up : &st->done_down;
264 wait_for_completion(done);
265}
266
267static inline void complete_ap_thread(struct cpuhp_cpu_state *st, bool bringup)
268{
269 struct completion *done = bringup ? &st->done_up : &st->done_down;
270 complete(done);
271}
272
273/*
274 * The former STARTING/DYING states, ran with IRQs disabled and must not fail.
275 */
276static bool cpuhp_is_atomic_state(enum cpuhp_state state)
277{
278 return CPUHP_AP_IDLE_DEAD <= state && state < CPUHP_AP_ONLINE;
279}
280
281/* Synchronization state management */
282enum cpuhp_sync_state {
283 SYNC_STATE_DEAD,
284 SYNC_STATE_KICKED,
285 SYNC_STATE_SHOULD_DIE,
286 SYNC_STATE_ALIVE,
287 SYNC_STATE_SHOULD_ONLINE,
288 SYNC_STATE_ONLINE,
289};
290
291#ifdef CONFIG_HOTPLUG_CORE_SYNC
292/**
293 * cpuhp_ap_update_sync_state - Update synchronization state during bringup/teardown
294 * @state: The synchronization state to set
295 *
296 * No synchronization point. Just update of the synchronization state, but implies
297 * a full barrier so that the AP changes are visible before the control CPU proceeds.
298 */
299static inline void cpuhp_ap_update_sync_state(enum cpuhp_sync_state state)
300{
301 atomic_t *st = this_cpu_ptr(&cpuhp_state.ap_sync_state);
302
303 (void)atomic_xchg(st, state);
304}
305
306void __weak arch_cpuhp_sync_state_poll(void) { cpu_relax(); }
307
308static bool cpuhp_wait_for_sync_state(unsigned int cpu, enum cpuhp_sync_state state,
309 enum cpuhp_sync_state next_state)
310{
311 atomic_t *st = per_cpu_ptr(&cpuhp_state.ap_sync_state, cpu);
312 ktime_t now, end, start = ktime_get();
313 int sync;
314
315 end = start + 10ULL * NSEC_PER_SEC;
316
317 sync = atomic_read(st);
318 while (1) {
319 if (sync == state) {
320 if (!atomic_try_cmpxchg(st, &sync, next_state))
321 continue;
322 return true;
323 }
324
325 now = ktime_get();
326 if (now > end) {
327 /* Timeout. Leave the state unchanged */
328 return false;
329 } else if (now - start < NSEC_PER_MSEC) {
330 /* Poll for one millisecond */
331 arch_cpuhp_sync_state_poll();
332 } else {
333 usleep_range_state(USEC_PER_MSEC, 2 * USEC_PER_MSEC, TASK_UNINTERRUPTIBLE);
334 }
335 sync = atomic_read(st);
336 }
337 return true;
338}
339#else /* CONFIG_HOTPLUG_CORE_SYNC */
340static inline void cpuhp_ap_update_sync_state(enum cpuhp_sync_state state) { }
341#endif /* !CONFIG_HOTPLUG_CORE_SYNC */
342
343#ifdef CONFIG_HOTPLUG_CORE_SYNC_DEAD
344/**
345 * cpuhp_ap_report_dead - Update synchronization state to DEAD
346 *
347 * No synchronization point. Just update of the synchronization state.
348 */
349void cpuhp_ap_report_dead(void)
350{
351 cpuhp_ap_update_sync_state(SYNC_STATE_DEAD);
352}
353
354void __weak arch_cpuhp_cleanup_dead_cpu(unsigned int cpu) { }
355
356/*
357 * Late CPU shutdown synchronization point. Cannot use cpuhp_state::done_down
358 * because the AP cannot issue complete() at this stage.
359 */
360static void cpuhp_bp_sync_dead(unsigned int cpu)
361{
362 atomic_t *st = per_cpu_ptr(&cpuhp_state.ap_sync_state, cpu);
363 int sync = atomic_read(st);
364
365 do {
366 /* CPU can have reported dead already. Don't overwrite that! */
367 if (sync == SYNC_STATE_DEAD)
368 break;
369 } while (!atomic_try_cmpxchg(st, &sync, SYNC_STATE_SHOULD_DIE));
370
371 if (cpuhp_wait_for_sync_state(cpu, SYNC_STATE_DEAD, SYNC_STATE_DEAD)) {
372 /* CPU reached dead state. Invoke the cleanup function */
373 arch_cpuhp_cleanup_dead_cpu(cpu);
374 return;
375 }
376
377 /* No further action possible. Emit message and give up. */
378 pr_err("CPU%u failed to report dead state\n", cpu);
379}
380#else /* CONFIG_HOTPLUG_CORE_SYNC_DEAD */
381static inline void cpuhp_bp_sync_dead(unsigned int cpu) { }
382#endif /* !CONFIG_HOTPLUG_CORE_SYNC_DEAD */
383
384#ifdef CONFIG_HOTPLUG_CORE_SYNC_FULL
385/**
386 * cpuhp_ap_sync_alive - Synchronize AP with the control CPU once it is alive
387 *
388 * Updates the AP synchronization state to SYNC_STATE_ALIVE and waits
389 * for the BP to release it.
390 */
391void cpuhp_ap_sync_alive(void)
392{
393 atomic_t *st = this_cpu_ptr(&cpuhp_state.ap_sync_state);
394
395 cpuhp_ap_update_sync_state(SYNC_STATE_ALIVE);
396
397 /* Wait for the control CPU to release it. */
398 while (atomic_read(st) != SYNC_STATE_SHOULD_ONLINE)
399 cpu_relax();
400}
401
402static bool cpuhp_can_boot_ap(unsigned int cpu)
403{
404 atomic_t *st = per_cpu_ptr(&cpuhp_state.ap_sync_state, cpu);
405 int sync = atomic_read(st);
406
407again:
408 switch (sync) {
409 case SYNC_STATE_DEAD:
410 /* CPU is properly dead */
411 break;
412 case SYNC_STATE_KICKED:
413 /* CPU did not come up in previous attempt */
414 break;
415 case SYNC_STATE_ALIVE:
416 /* CPU is stuck cpuhp_ap_sync_alive(). */
417 break;
418 default:
419 /* CPU failed to report online or dead and is in limbo state. */
420 return false;
421 }
422
423 /* Prepare for booting */
424 if (!atomic_try_cmpxchg(st, &sync, SYNC_STATE_KICKED))
425 goto again;
426
427 return true;
428}
429
430void __weak arch_cpuhp_cleanup_kick_cpu(unsigned int cpu) { }
431
432/*
433 * Early CPU bringup synchronization point. Cannot use cpuhp_state::done_up
434 * because the AP cannot issue complete() so early in the bringup.
435 */
436static int cpuhp_bp_sync_alive(unsigned int cpu)
437{
438 int ret = 0;
439
440 if (!IS_ENABLED(CONFIG_HOTPLUG_CORE_SYNC_FULL))
441 return 0;
442
443 if (!cpuhp_wait_for_sync_state(cpu, SYNC_STATE_ALIVE, SYNC_STATE_SHOULD_ONLINE)) {
444 pr_err("CPU%u failed to report alive state\n", cpu);
445 ret = -EIO;
446 }
447
448 /* Let the architecture cleanup the kick alive mechanics. */
449 arch_cpuhp_cleanup_kick_cpu(cpu);
450 return ret;
451}
452#else /* CONFIG_HOTPLUG_CORE_SYNC_FULL */
453static inline int cpuhp_bp_sync_alive(unsigned int cpu) { return 0; }
454static inline bool cpuhp_can_boot_ap(unsigned int cpu) { return true; }
455#endif /* !CONFIG_HOTPLUG_CORE_SYNC_FULL */
456
457/* Serializes the updates to cpu_online_mask, cpu_present_mask */
458static DEFINE_MUTEX(cpu_add_remove_lock);
459bool cpuhp_tasks_frozen;
460EXPORT_SYMBOL_GPL(cpuhp_tasks_frozen);
461
462/*
463 * The following two APIs (cpu_maps_update_begin/done) must be used when
464 * attempting to serialize the updates to cpu_online_mask & cpu_present_mask.
465 */
466void cpu_maps_update_begin(void)
467{
468 mutex_lock(&cpu_add_remove_lock);
469}
470
471void cpu_maps_update_done(void)
472{
473 mutex_unlock(&cpu_add_remove_lock);
474}
475
476/*
477 * If set, cpu_up and cpu_down will return -EBUSY and do nothing.
478 * Should always be manipulated under cpu_add_remove_lock
479 */
480static int cpu_hotplug_disabled;
481
482#ifdef CONFIG_HOTPLUG_CPU
483
484DEFINE_STATIC_PERCPU_RWSEM(cpu_hotplug_lock);
485
486void cpus_read_lock(void)
487{
488 percpu_down_read(&cpu_hotplug_lock);
489}
490EXPORT_SYMBOL_GPL(cpus_read_lock);
491
492int cpus_read_trylock(void)
493{
494 return percpu_down_read_trylock(&cpu_hotplug_lock);
495}
496EXPORT_SYMBOL_GPL(cpus_read_trylock);
497
498void cpus_read_unlock(void)
499{
500 percpu_up_read(&cpu_hotplug_lock);
501}
502EXPORT_SYMBOL_GPL(cpus_read_unlock);
503
504void cpus_write_lock(void)
505{
506 percpu_down_write(&cpu_hotplug_lock);
507}
508
509void cpus_write_unlock(void)
510{
511 percpu_up_write(&cpu_hotplug_lock);
512}
513
514void lockdep_assert_cpus_held(void)
515{
516 /*
517 * We can't have hotplug operations before userspace starts running,
518 * and some init codepaths will knowingly not take the hotplug lock.
519 * This is all valid, so mute lockdep until it makes sense to report
520 * unheld locks.
521 */
522 if (system_state < SYSTEM_RUNNING)
523 return;
524
525 percpu_rwsem_assert_held(&cpu_hotplug_lock);
526}
527
528#ifdef CONFIG_LOCKDEP
529int lockdep_is_cpus_held(void)
530{
531 return percpu_rwsem_is_held(&cpu_hotplug_lock);
532}
533#endif
534
535static void lockdep_acquire_cpus_lock(void)
536{
537 rwsem_acquire(&cpu_hotplug_lock.dep_map, 0, 0, _THIS_IP_);
538}
539
540static void lockdep_release_cpus_lock(void)
541{
542 rwsem_release(&cpu_hotplug_lock.dep_map, _THIS_IP_);
543}
544
545/*
546 * Wait for currently running CPU hotplug operations to complete (if any) and
547 * disable future CPU hotplug (from sysfs). The 'cpu_add_remove_lock' protects
548 * the 'cpu_hotplug_disabled' flag. The same lock is also acquired by the
549 * hotplug path before performing hotplug operations. So acquiring that lock
550 * guarantees mutual exclusion from any currently running hotplug operations.
551 */
552void cpu_hotplug_disable(void)
553{
554 cpu_maps_update_begin();
555 cpu_hotplug_disabled++;
556 cpu_maps_update_done();
557}
558EXPORT_SYMBOL_GPL(cpu_hotplug_disable);
559
560static void __cpu_hotplug_enable(void)
561{
562 if (WARN_ONCE(!cpu_hotplug_disabled, "Unbalanced cpu hotplug enable\n"))
563 return;
564 cpu_hotplug_disabled--;
565}
566
567void cpu_hotplug_enable(void)
568{
569 cpu_maps_update_begin();
570 __cpu_hotplug_enable();
571 cpu_maps_update_done();
572}
573EXPORT_SYMBOL_GPL(cpu_hotplug_enable);
574
575#else
576
577static void lockdep_acquire_cpus_lock(void)
578{
579}
580
581static void lockdep_release_cpus_lock(void)
582{
583}
584
585#endif /* CONFIG_HOTPLUG_CPU */
586
587/*
588 * Architectures that need SMT-specific errata handling during SMT hotplug
589 * should override this.
590 */
591void __weak arch_smt_update(void) { }
592
593#ifdef CONFIG_HOTPLUG_SMT
594
595enum cpuhp_smt_control cpu_smt_control __read_mostly = CPU_SMT_ENABLED;
596static unsigned int cpu_smt_max_threads __ro_after_init;
597unsigned int cpu_smt_num_threads __read_mostly = UINT_MAX;
598
599void __init cpu_smt_disable(bool force)
600{
601 if (!cpu_smt_possible())
602 return;
603
604 if (force) {
605 pr_info("SMT: Force disabled\n");
606 cpu_smt_control = CPU_SMT_FORCE_DISABLED;
607 } else {
608 pr_info("SMT: disabled\n");
609 cpu_smt_control = CPU_SMT_DISABLED;
610 }
611 cpu_smt_num_threads = 1;
612}
613
614/*
615 * The decision whether SMT is supported can only be done after the full
616 * CPU identification. Called from architecture code.
617 */
618void __init cpu_smt_set_num_threads(unsigned int num_threads,
619 unsigned int max_threads)
620{
621 WARN_ON(!num_threads || (num_threads > max_threads));
622
623 if (max_threads == 1)
624 cpu_smt_control = CPU_SMT_NOT_SUPPORTED;
625
626 cpu_smt_max_threads = max_threads;
627
628 /*
629 * If SMT has been disabled via the kernel command line or SMT is
630 * not supported, set cpu_smt_num_threads to 1 for consistency.
631 * If enabled, take the architecture requested number of threads
632 * to bring up into account.
633 */
634 if (cpu_smt_control != CPU_SMT_ENABLED)
635 cpu_smt_num_threads = 1;
636 else if (num_threads < cpu_smt_num_threads)
637 cpu_smt_num_threads = num_threads;
638}
639
640static int __init smt_cmdline_disable(char *str)
641{
642 cpu_smt_disable(str && !strcmp(str, "force"));
643 return 0;
644}
645early_param("nosmt", smt_cmdline_disable);
646
647/*
648 * For Archicture supporting partial SMT states check if the thread is allowed.
649 * Otherwise this has already been checked through cpu_smt_max_threads when
650 * setting the SMT level.
651 */
652static inline bool cpu_smt_thread_allowed(unsigned int cpu)
653{
654#ifdef CONFIG_SMT_NUM_THREADS_DYNAMIC
655 return topology_smt_thread_allowed(cpu);
656#else
657 return true;
658#endif
659}
660
661static inline bool cpu_bootable(unsigned int cpu)
662{
663 if (cpu_smt_control == CPU_SMT_ENABLED && cpu_smt_thread_allowed(cpu))
664 return true;
665
666 /* All CPUs are bootable if controls are not configured */
667 if (cpu_smt_control == CPU_SMT_NOT_IMPLEMENTED)
668 return true;
669
670 /* All CPUs are bootable if CPU is not SMT capable */
671 if (cpu_smt_control == CPU_SMT_NOT_SUPPORTED)
672 return true;
673
674 if (topology_is_primary_thread(cpu))
675 return true;
676
677 /*
678 * On x86 it's required to boot all logical CPUs at least once so
679 * that the init code can get a chance to set CR4.MCE on each
680 * CPU. Otherwise, a broadcasted MCE observing CR4.MCE=0b on any
681 * core will shutdown the machine.
682 */
683 return !cpumask_test_cpu(cpu, &cpus_booted_once_mask);
684}
685
686/* Returns true if SMT is supported and not forcefully (irreversibly) disabled */
687bool cpu_smt_possible(void)
688{
689 return cpu_smt_control != CPU_SMT_FORCE_DISABLED &&
690 cpu_smt_control != CPU_SMT_NOT_SUPPORTED;
691}
692EXPORT_SYMBOL_GPL(cpu_smt_possible);
693
694#else
695static inline bool cpu_bootable(unsigned int cpu) { return true; }
696#endif
697
698static inline enum cpuhp_state
699cpuhp_set_state(int cpu, struct cpuhp_cpu_state *st, enum cpuhp_state target)
700{
701 enum cpuhp_state prev_state = st->state;
702 bool bringup = st->state < target;
703
704 st->rollback = false;
705 st->last = NULL;
706
707 st->target = target;
708 st->single = false;
709 st->bringup = bringup;
710 if (cpu_dying(cpu) != !bringup)
711 set_cpu_dying(cpu, !bringup);
712
713 return prev_state;
714}
715
716static inline void
717cpuhp_reset_state(int cpu, struct cpuhp_cpu_state *st,
718 enum cpuhp_state prev_state)
719{
720 bool bringup = !st->bringup;
721
722 st->target = prev_state;
723
724 /*
725 * Already rolling back. No need invert the bringup value or to change
726 * the current state.
727 */
728 if (st->rollback)
729 return;
730
731 st->rollback = true;
732
733 /*
734 * If we have st->last we need to undo partial multi_instance of this
735 * state first. Otherwise start undo at the previous state.
736 */
737 if (!st->last) {
738 if (st->bringup)
739 st->state--;
740 else
741 st->state++;
742 }
743
744 st->bringup = bringup;
745 if (cpu_dying(cpu) != !bringup)
746 set_cpu_dying(cpu, !bringup);
747}
748
749/* Regular hotplug invocation of the AP hotplug thread */
750static void __cpuhp_kick_ap(struct cpuhp_cpu_state *st)
751{
752 if (!st->single && st->state == st->target)
753 return;
754
755 st->result = 0;
756 /*
757 * Make sure the above stores are visible before should_run becomes
758 * true. Paired with the mb() above in cpuhp_thread_fun()
759 */
760 smp_mb();
761 st->should_run = true;
762 wake_up_process(st->thread);
763 wait_for_ap_thread(st, st->bringup);
764}
765
766static int cpuhp_kick_ap(int cpu, struct cpuhp_cpu_state *st,
767 enum cpuhp_state target)
768{
769 enum cpuhp_state prev_state;
770 int ret;
771
772 prev_state = cpuhp_set_state(cpu, st, target);
773 __cpuhp_kick_ap(st);
774 if ((ret = st->result)) {
775 cpuhp_reset_state(cpu, st, prev_state);
776 __cpuhp_kick_ap(st);
777 }
778
779 return ret;
780}
781
782static int bringup_wait_for_ap_online(unsigned int cpu)
783{
784 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
785
786 /* Wait for the CPU to reach CPUHP_AP_ONLINE_IDLE */
787 wait_for_ap_thread(st, true);
788 if (WARN_ON_ONCE((!cpu_online(cpu))))
789 return -ECANCELED;
790
791 /* Unpark the hotplug thread of the target cpu */
792 kthread_unpark(st->thread);
793
794 /*
795 * SMT soft disabling on X86 requires to bring the CPU out of the
796 * BIOS 'wait for SIPI' state in order to set the CR4.MCE bit. The
797 * CPU marked itself as booted_once in notify_cpu_starting() so the
798 * cpu_bootable() check will now return false if this is not the
799 * primary sibling.
800 */
801 if (!cpu_bootable(cpu))
802 return -ECANCELED;
803 return 0;
804}
805
806#ifdef CONFIG_HOTPLUG_SPLIT_STARTUP
807static int cpuhp_kick_ap_alive(unsigned int cpu)
808{
809 if (!cpuhp_can_boot_ap(cpu))
810 return -EAGAIN;
811
812 return arch_cpuhp_kick_ap_alive(cpu, idle_thread_get(cpu));
813}
814
815static int cpuhp_bringup_ap(unsigned int cpu)
816{
817 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
818 int ret;
819
820 /*
821 * Some architectures have to walk the irq descriptors to
822 * setup the vector space for the cpu which comes online.
823 * Prevent irq alloc/free across the bringup.
824 */
825 irq_lock_sparse();
826
827 ret = cpuhp_bp_sync_alive(cpu);
828 if (ret)
829 goto out_unlock;
830
831 ret = bringup_wait_for_ap_online(cpu);
832 if (ret)
833 goto out_unlock;
834
835 irq_unlock_sparse();
836
837 if (st->target <= CPUHP_AP_ONLINE_IDLE)
838 return 0;
839
840 return cpuhp_kick_ap(cpu, st, st->target);
841
842out_unlock:
843 irq_unlock_sparse();
844 return ret;
845}
846#else
847static int bringup_cpu(unsigned int cpu)
848{
849 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
850 struct task_struct *idle = idle_thread_get(cpu);
851 int ret;
852
853 if (!cpuhp_can_boot_ap(cpu))
854 return -EAGAIN;
855
856 /*
857 * Some architectures have to walk the irq descriptors to
858 * setup the vector space for the cpu which comes online.
859 *
860 * Prevent irq alloc/free across the bringup by acquiring the
861 * sparse irq lock. Hold it until the upcoming CPU completes the
862 * startup in cpuhp_online_idle() which allows to avoid
863 * intermediate synchronization points in the architecture code.
864 */
865 irq_lock_sparse();
866
867 ret = __cpu_up(cpu, idle);
868 if (ret)
869 goto out_unlock;
870
871 ret = cpuhp_bp_sync_alive(cpu);
872 if (ret)
873 goto out_unlock;
874
875 ret = bringup_wait_for_ap_online(cpu);
876 if (ret)
877 goto out_unlock;
878
879 irq_unlock_sparse();
880
881 if (st->target <= CPUHP_AP_ONLINE_IDLE)
882 return 0;
883
884 return cpuhp_kick_ap(cpu, st, st->target);
885
886out_unlock:
887 irq_unlock_sparse();
888 return ret;
889}
890#endif
891
892static int finish_cpu(unsigned int cpu)
893{
894 struct task_struct *idle = idle_thread_get(cpu);
895 struct mm_struct *mm = idle->active_mm;
896
897 /*
898 * idle_task_exit() will have switched to &init_mm, now
899 * clean up any remaining active_mm state.
900 */
901 if (mm != &init_mm)
902 idle->active_mm = &init_mm;
903 mmdrop_lazy_tlb(mm);
904 return 0;
905}
906
907/*
908 * Hotplug state machine related functions
909 */
910
911/*
912 * Get the next state to run. Empty ones will be skipped. Returns true if a
913 * state must be run.
914 *
915 * st->state will be modified ahead of time, to match state_to_run, as if it
916 * has already ran.
917 */
918static bool cpuhp_next_state(bool bringup,
919 enum cpuhp_state *state_to_run,
920 struct cpuhp_cpu_state *st,
921 enum cpuhp_state target)
922{
923 do {
924 if (bringup) {
925 if (st->state >= target)
926 return false;
927
928 *state_to_run = ++st->state;
929 } else {
930 if (st->state <= target)
931 return false;
932
933 *state_to_run = st->state--;
934 }
935
936 if (!cpuhp_step_empty(bringup, cpuhp_get_step(*state_to_run)))
937 break;
938 } while (true);
939
940 return true;
941}
942
943static int __cpuhp_invoke_callback_range(bool bringup,
944 unsigned int cpu,
945 struct cpuhp_cpu_state *st,
946 enum cpuhp_state target,
947 bool nofail)
948{
949 enum cpuhp_state state;
950 int ret = 0;
951
952 while (cpuhp_next_state(bringup, &state, st, target)) {
953 int err;
954
955 err = cpuhp_invoke_callback(cpu, state, bringup, NULL, NULL);
956 if (!err)
957 continue;
958
959 if (nofail) {
960 pr_warn("CPU %u %s state %s (%d) failed (%d)\n",
961 cpu, bringup ? "UP" : "DOWN",
962 cpuhp_get_step(st->state)->name,
963 st->state, err);
964 ret = -1;
965 } else {
966 ret = err;
967 break;
968 }
969 }
970
971 return ret;
972}
973
974static inline int cpuhp_invoke_callback_range(bool bringup,
975 unsigned int cpu,
976 struct cpuhp_cpu_state *st,
977 enum cpuhp_state target)
978{
979 return __cpuhp_invoke_callback_range(bringup, cpu, st, target, false);
980}
981
982static inline void cpuhp_invoke_callback_range_nofail(bool bringup,
983 unsigned int cpu,
984 struct cpuhp_cpu_state *st,
985 enum cpuhp_state target)
986{
987 __cpuhp_invoke_callback_range(bringup, cpu, st, target, true);
988}
989
990static inline bool can_rollback_cpu(struct cpuhp_cpu_state *st)
991{
992 if (IS_ENABLED(CONFIG_HOTPLUG_CPU))
993 return true;
994 /*
995 * When CPU hotplug is disabled, then taking the CPU down is not
996 * possible because takedown_cpu() and the architecture and
997 * subsystem specific mechanisms are not available. So the CPU
998 * which would be completely unplugged again needs to stay around
999 * in the current state.
1000 */
1001 return st->state <= CPUHP_BRINGUP_CPU;
1002}
1003
1004static int cpuhp_up_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
1005 enum cpuhp_state target)
1006{
1007 enum cpuhp_state prev_state = st->state;
1008 int ret = 0;
1009
1010 ret = cpuhp_invoke_callback_range(true, cpu, st, target);
1011 if (ret) {
1012 pr_debug("CPU UP failed (%d) CPU %u state %s (%d)\n",
1013 ret, cpu, cpuhp_get_step(st->state)->name,
1014 st->state);
1015
1016 cpuhp_reset_state(cpu, st, prev_state);
1017 if (can_rollback_cpu(st))
1018 WARN_ON(cpuhp_invoke_callback_range(false, cpu, st,
1019 prev_state));
1020 }
1021 return ret;
1022}
1023
1024/*
1025 * The cpu hotplug threads manage the bringup and teardown of the cpus
1026 */
1027static int cpuhp_should_run(unsigned int cpu)
1028{
1029 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
1030
1031 return st->should_run;
1032}
1033
1034/*
1035 * Execute teardown/startup callbacks on the plugged cpu. Also used to invoke
1036 * callbacks when a state gets [un]installed at runtime.
1037 *
1038 * Each invocation of this function by the smpboot thread does a single AP
1039 * state callback.
1040 *
1041 * It has 3 modes of operation:
1042 * - single: runs st->cb_state
1043 * - up: runs ++st->state, while st->state < st->target
1044 * - down: runs st->state--, while st->state > st->target
1045 *
1046 * When complete or on error, should_run is cleared and the completion is fired.
1047 */
1048static void cpuhp_thread_fun(unsigned int cpu)
1049{
1050 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
1051 bool bringup = st->bringup;
1052 enum cpuhp_state state;
1053
1054 if (WARN_ON_ONCE(!st->should_run))
1055 return;
1056
1057 /*
1058 * ACQUIRE for the cpuhp_should_run() load of ->should_run. Ensures
1059 * that if we see ->should_run we also see the rest of the state.
1060 */
1061 smp_mb();
1062
1063 /*
1064 * The BP holds the hotplug lock, but we're now running on the AP,
1065 * ensure that anybody asserting the lock is held, will actually find
1066 * it so.
1067 */
1068 lockdep_acquire_cpus_lock();
1069 cpuhp_lock_acquire(bringup);
1070
1071 if (st->single) {
1072 state = st->cb_state;
1073 st->should_run = false;
1074 } else {
1075 st->should_run = cpuhp_next_state(bringup, &state, st, st->target);
1076 if (!st->should_run)
1077 goto end;
1078 }
1079
1080 WARN_ON_ONCE(!cpuhp_is_ap_state(state));
1081
1082 if (cpuhp_is_atomic_state(state)) {
1083 local_irq_disable();
1084 st->result = cpuhp_invoke_callback(cpu, state, bringup, st->node, &st->last);
1085 local_irq_enable();
1086
1087 /*
1088 * STARTING/DYING must not fail!
1089 */
1090 WARN_ON_ONCE(st->result);
1091 } else {
1092 st->result = cpuhp_invoke_callback(cpu, state, bringup, st->node, &st->last);
1093 }
1094
1095 if (st->result) {
1096 /*
1097 * If we fail on a rollback, we're up a creek without no
1098 * paddle, no way forward, no way back. We loose, thanks for
1099 * playing.
1100 */
1101 WARN_ON_ONCE(st->rollback);
1102 st->should_run = false;
1103 }
1104
1105end:
1106 cpuhp_lock_release(bringup);
1107 lockdep_release_cpus_lock();
1108
1109 if (!st->should_run)
1110 complete_ap_thread(st, bringup);
1111}
1112
1113/* Invoke a single callback on a remote cpu */
1114static int
1115cpuhp_invoke_ap_callback(int cpu, enum cpuhp_state state, bool bringup,
1116 struct hlist_node *node)
1117{
1118 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1119 int ret;
1120
1121 if (!cpu_online(cpu))
1122 return 0;
1123
1124 cpuhp_lock_acquire(false);
1125 cpuhp_lock_release(false);
1126
1127 cpuhp_lock_acquire(true);
1128 cpuhp_lock_release(true);
1129
1130 /*
1131 * If we are up and running, use the hotplug thread. For early calls
1132 * we invoke the thread function directly.
1133 */
1134 if (!st->thread)
1135 return cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
1136
1137 st->rollback = false;
1138 st->last = NULL;
1139
1140 st->node = node;
1141 st->bringup = bringup;
1142 st->cb_state = state;
1143 st->single = true;
1144
1145 __cpuhp_kick_ap(st);
1146
1147 /*
1148 * If we failed and did a partial, do a rollback.
1149 */
1150 if ((ret = st->result) && st->last) {
1151 st->rollback = true;
1152 st->bringup = !bringup;
1153
1154 __cpuhp_kick_ap(st);
1155 }
1156
1157 /*
1158 * Clean up the leftovers so the next hotplug operation wont use stale
1159 * data.
1160 */
1161 st->node = st->last = NULL;
1162 return ret;
1163}
1164
1165static int cpuhp_kick_ap_work(unsigned int cpu)
1166{
1167 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1168 enum cpuhp_state prev_state = st->state;
1169 int ret;
1170
1171 cpuhp_lock_acquire(false);
1172 cpuhp_lock_release(false);
1173
1174 cpuhp_lock_acquire(true);
1175 cpuhp_lock_release(true);
1176
1177 trace_cpuhp_enter(cpu, st->target, prev_state, cpuhp_kick_ap_work);
1178 ret = cpuhp_kick_ap(cpu, st, st->target);
1179 trace_cpuhp_exit(cpu, st->state, prev_state, ret);
1180
1181 return ret;
1182}
1183
1184static struct smp_hotplug_thread cpuhp_threads = {
1185 .store = &cpuhp_state.thread,
1186 .thread_should_run = cpuhp_should_run,
1187 .thread_fn = cpuhp_thread_fun,
1188 .thread_comm = "cpuhp/%u",
1189 .selfparking = true,
1190};
1191
1192static __init void cpuhp_init_state(void)
1193{
1194 struct cpuhp_cpu_state *st;
1195 int cpu;
1196
1197 for_each_possible_cpu(cpu) {
1198 st = per_cpu_ptr(&cpuhp_state, cpu);
1199 init_completion(&st->done_up);
1200 init_completion(&st->done_down);
1201 }
1202}
1203
1204void __init cpuhp_threads_init(void)
1205{
1206 cpuhp_init_state();
1207 BUG_ON(smpboot_register_percpu_thread(&cpuhp_threads));
1208 kthread_unpark(this_cpu_read(cpuhp_state.thread));
1209}
1210
1211/*
1212 *
1213 * Serialize hotplug trainwrecks outside of the cpu_hotplug_lock
1214 * protected region.
1215 *
1216 * The operation is still serialized against concurrent CPU hotplug via
1217 * cpu_add_remove_lock, i.e. CPU map protection. But it is _not_
1218 * serialized against other hotplug related activity like adding or
1219 * removing of state callbacks and state instances, which invoke either the
1220 * startup or the teardown callback of the affected state.
1221 *
1222 * This is required for subsystems which are unfixable vs. CPU hotplug and
1223 * evade lock inversion problems by scheduling work which has to be
1224 * completed _before_ cpu_up()/_cpu_down() returns.
1225 *
1226 * Don't even think about adding anything to this for any new code or even
1227 * drivers. It's only purpose is to keep existing lock order trainwrecks
1228 * working.
1229 *
1230 * For cpu_down() there might be valid reasons to finish cleanups which are
1231 * not required to be done under cpu_hotplug_lock, but that's a different
1232 * story and would be not invoked via this.
1233 */
1234static void cpu_up_down_serialize_trainwrecks(bool tasks_frozen)
1235{
1236 /*
1237 * cpusets delegate hotplug operations to a worker to "solve" the
1238 * lock order problems. Wait for the worker, but only if tasks are
1239 * _not_ frozen (suspend, hibernate) as that would wait forever.
1240 *
1241 * The wait is required because otherwise the hotplug operation
1242 * returns with inconsistent state, which could even be observed in
1243 * user space when a new CPU is brought up. The CPU plug uevent
1244 * would be delivered and user space reacting on it would fail to
1245 * move tasks to the newly plugged CPU up to the point where the
1246 * work has finished because up to that point the newly plugged CPU
1247 * is not assignable in cpusets/cgroups. On unplug that's not
1248 * necessarily a visible issue, but it is still inconsistent state,
1249 * which is the real problem which needs to be "fixed". This can't
1250 * prevent the transient state between scheduling the work and
1251 * returning from waiting for it.
1252 */
1253 if (!tasks_frozen)
1254 cpuset_wait_for_hotplug();
1255}
1256
1257#ifdef CONFIG_HOTPLUG_CPU
1258#ifndef arch_clear_mm_cpumask_cpu
1259#define arch_clear_mm_cpumask_cpu(cpu, mm) cpumask_clear_cpu(cpu, mm_cpumask(mm))
1260#endif
1261
1262/**
1263 * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
1264 * @cpu: a CPU id
1265 *
1266 * This function walks all processes, finds a valid mm struct for each one and
1267 * then clears a corresponding bit in mm's cpumask. While this all sounds
1268 * trivial, there are various non-obvious corner cases, which this function
1269 * tries to solve in a safe manner.
1270 *
1271 * Also note that the function uses a somewhat relaxed locking scheme, so it may
1272 * be called only for an already offlined CPU.
1273 */
1274void clear_tasks_mm_cpumask(int cpu)
1275{
1276 struct task_struct *p;
1277
1278 /*
1279 * This function is called after the cpu is taken down and marked
1280 * offline, so its not like new tasks will ever get this cpu set in
1281 * their mm mask. -- Peter Zijlstra
1282 * Thus, we may use rcu_read_lock() here, instead of grabbing
1283 * full-fledged tasklist_lock.
1284 */
1285 WARN_ON(cpu_online(cpu));
1286 rcu_read_lock();
1287 for_each_process(p) {
1288 struct task_struct *t;
1289
1290 /*
1291 * Main thread might exit, but other threads may still have
1292 * a valid mm. Find one.
1293 */
1294 t = find_lock_task_mm(p);
1295 if (!t)
1296 continue;
1297 arch_clear_mm_cpumask_cpu(cpu, t->mm);
1298 task_unlock(t);
1299 }
1300 rcu_read_unlock();
1301}
1302
1303/* Take this CPU down. */
1304static int take_cpu_down(void *_param)
1305{
1306 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
1307 enum cpuhp_state target = max((int)st->target, CPUHP_AP_OFFLINE);
1308 int err, cpu = smp_processor_id();
1309
1310 /* Ensure this CPU doesn't handle any more interrupts. */
1311 err = __cpu_disable();
1312 if (err < 0)
1313 return err;
1314
1315 /*
1316 * Must be called from CPUHP_TEARDOWN_CPU, which means, as we are going
1317 * down, that the current state is CPUHP_TEARDOWN_CPU - 1.
1318 */
1319 WARN_ON(st->state != (CPUHP_TEARDOWN_CPU - 1));
1320
1321 /*
1322 * Invoke the former CPU_DYING callbacks. DYING must not fail!
1323 */
1324 cpuhp_invoke_callback_range_nofail(false, cpu, st, target);
1325
1326 /* Park the stopper thread */
1327 stop_machine_park(cpu);
1328 return 0;
1329}
1330
1331static int takedown_cpu(unsigned int cpu)
1332{
1333 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1334 int err;
1335
1336 /* Park the smpboot threads */
1337 kthread_park(st->thread);
1338
1339 /*
1340 * Prevent irq alloc/free while the dying cpu reorganizes the
1341 * interrupt affinities.
1342 */
1343 irq_lock_sparse();
1344
1345 /*
1346 * So now all preempt/rcu users must observe !cpu_active().
1347 */
1348 err = stop_machine_cpuslocked(take_cpu_down, NULL, cpumask_of(cpu));
1349 if (err) {
1350 /* CPU refused to die */
1351 irq_unlock_sparse();
1352 /* Unpark the hotplug thread so we can rollback there */
1353 kthread_unpark(st->thread);
1354 return err;
1355 }
1356 BUG_ON(cpu_online(cpu));
1357
1358 /*
1359 * The teardown callback for CPUHP_AP_SCHED_STARTING will have removed
1360 * all runnable tasks from the CPU, there's only the idle task left now
1361 * that the migration thread is done doing the stop_machine thing.
1362 *
1363 * Wait for the stop thread to go away.
1364 */
1365 wait_for_ap_thread(st, false);
1366 BUG_ON(st->state != CPUHP_AP_IDLE_DEAD);
1367
1368 /* Interrupts are moved away from the dying cpu, reenable alloc/free */
1369 irq_unlock_sparse();
1370
1371 hotplug_cpu__broadcast_tick_pull(cpu);
1372 /* This actually kills the CPU. */
1373 __cpu_die(cpu);
1374
1375 cpuhp_bp_sync_dead(cpu);
1376
1377 tick_cleanup_dead_cpu(cpu);
1378
1379 /*
1380 * Callbacks must be re-integrated right away to the RCU state machine.
1381 * Otherwise an RCU callback could block a further teardown function
1382 * waiting for its completion.
1383 */
1384 rcutree_migrate_callbacks(cpu);
1385
1386 return 0;
1387}
1388
1389static void cpuhp_complete_idle_dead(void *arg)
1390{
1391 struct cpuhp_cpu_state *st = arg;
1392
1393 complete_ap_thread(st, false);
1394}
1395
1396void cpuhp_report_idle_dead(void)
1397{
1398 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
1399
1400 BUG_ON(st->state != CPUHP_AP_OFFLINE);
1401 tick_assert_timekeeping_handover();
1402 rcutree_report_cpu_dead();
1403 st->state = CPUHP_AP_IDLE_DEAD;
1404 /*
1405 * We cannot call complete after rcutree_report_cpu_dead() so we delegate it
1406 * to an online cpu.
1407 */
1408 smp_call_function_single(cpumask_first(cpu_online_mask),
1409 cpuhp_complete_idle_dead, st, 0);
1410}
1411
1412static int cpuhp_down_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
1413 enum cpuhp_state target)
1414{
1415 enum cpuhp_state prev_state = st->state;
1416 int ret = 0;
1417
1418 ret = cpuhp_invoke_callback_range(false, cpu, st, target);
1419 if (ret) {
1420 pr_debug("CPU DOWN failed (%d) CPU %u state %s (%d)\n",
1421 ret, cpu, cpuhp_get_step(st->state)->name,
1422 st->state);
1423
1424 cpuhp_reset_state(cpu, st, prev_state);
1425
1426 if (st->state < prev_state)
1427 WARN_ON(cpuhp_invoke_callback_range(true, cpu, st,
1428 prev_state));
1429 }
1430
1431 return ret;
1432}
1433
1434/* Requires cpu_add_remove_lock to be held */
1435static int __ref _cpu_down(unsigned int cpu, int tasks_frozen,
1436 enum cpuhp_state target)
1437{
1438 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1439 int prev_state, ret = 0;
1440
1441 if (num_online_cpus() == 1)
1442 return -EBUSY;
1443
1444 if (!cpu_present(cpu))
1445 return -EINVAL;
1446
1447 cpus_write_lock();
1448
1449 cpuhp_tasks_frozen = tasks_frozen;
1450
1451 prev_state = cpuhp_set_state(cpu, st, target);
1452 /*
1453 * If the current CPU state is in the range of the AP hotplug thread,
1454 * then we need to kick the thread.
1455 */
1456 if (st->state > CPUHP_TEARDOWN_CPU) {
1457 st->target = max((int)target, CPUHP_TEARDOWN_CPU);
1458 ret = cpuhp_kick_ap_work(cpu);
1459 /*
1460 * The AP side has done the error rollback already. Just
1461 * return the error code..
1462 */
1463 if (ret)
1464 goto out;
1465
1466 /*
1467 * We might have stopped still in the range of the AP hotplug
1468 * thread. Nothing to do anymore.
1469 */
1470 if (st->state > CPUHP_TEARDOWN_CPU)
1471 goto out;
1472
1473 st->target = target;
1474 }
1475 /*
1476 * The AP brought itself down to CPUHP_TEARDOWN_CPU. So we need
1477 * to do the further cleanups.
1478 */
1479 ret = cpuhp_down_callbacks(cpu, st, target);
1480 if (ret && st->state < prev_state) {
1481 if (st->state == CPUHP_TEARDOWN_CPU) {
1482 cpuhp_reset_state(cpu, st, prev_state);
1483 __cpuhp_kick_ap(st);
1484 } else {
1485 WARN(1, "DEAD callback error for CPU%d", cpu);
1486 }
1487 }
1488
1489out:
1490 cpus_write_unlock();
1491 /*
1492 * Do post unplug cleanup. This is still protected against
1493 * concurrent CPU hotplug via cpu_add_remove_lock.
1494 */
1495 lockup_detector_cleanup();
1496 arch_smt_update();
1497 cpu_up_down_serialize_trainwrecks(tasks_frozen);
1498 return ret;
1499}
1500
1501struct cpu_down_work {
1502 unsigned int cpu;
1503 enum cpuhp_state target;
1504};
1505
1506static long __cpu_down_maps_locked(void *arg)
1507{
1508 struct cpu_down_work *work = arg;
1509
1510 return _cpu_down(work->cpu, 0, work->target);
1511}
1512
1513static int cpu_down_maps_locked(unsigned int cpu, enum cpuhp_state target)
1514{
1515 struct cpu_down_work work = { .cpu = cpu, .target = target, };
1516
1517 /*
1518 * If the platform does not support hotplug, report it explicitly to
1519 * differentiate it from a transient offlining failure.
1520 */
1521 if (cc_platform_has(CC_ATTR_HOTPLUG_DISABLED))
1522 return -EOPNOTSUPP;
1523 if (cpu_hotplug_disabled)
1524 return -EBUSY;
1525
1526 /*
1527 * Ensure that the control task does not run on the to be offlined
1528 * CPU to prevent a deadlock against cfs_b->period_timer.
1529 * Also keep at least one housekeeping cpu onlined to avoid generating
1530 * an empty sched_domain span.
1531 */
1532 for_each_cpu_and(cpu, cpu_online_mask, housekeeping_cpumask(HK_TYPE_DOMAIN)) {
1533 if (cpu != work.cpu)
1534 return work_on_cpu(cpu, __cpu_down_maps_locked, &work);
1535 }
1536 return -EBUSY;
1537}
1538
1539static int cpu_down(unsigned int cpu, enum cpuhp_state target)
1540{
1541 int err;
1542
1543 cpu_maps_update_begin();
1544 err = cpu_down_maps_locked(cpu, target);
1545 cpu_maps_update_done();
1546 return err;
1547}
1548
1549/**
1550 * cpu_device_down - Bring down a cpu device
1551 * @dev: Pointer to the cpu device to offline
1552 *
1553 * This function is meant to be used by device core cpu subsystem only.
1554 *
1555 * Other subsystems should use remove_cpu() instead.
1556 *
1557 * Return: %0 on success or a negative errno code
1558 */
1559int cpu_device_down(struct device *dev)
1560{
1561 return cpu_down(dev->id, CPUHP_OFFLINE);
1562}
1563
1564int remove_cpu(unsigned int cpu)
1565{
1566 int ret;
1567
1568 lock_device_hotplug();
1569 ret = device_offline(get_cpu_device(cpu));
1570 unlock_device_hotplug();
1571
1572 return ret;
1573}
1574EXPORT_SYMBOL_GPL(remove_cpu);
1575
1576void smp_shutdown_nonboot_cpus(unsigned int primary_cpu)
1577{
1578 unsigned int cpu;
1579 int error;
1580
1581 cpu_maps_update_begin();
1582
1583 /*
1584 * Make certain the cpu I'm about to reboot on is online.
1585 *
1586 * This is inline to what migrate_to_reboot_cpu() already do.
1587 */
1588 if (!cpu_online(primary_cpu))
1589 primary_cpu = cpumask_first(cpu_online_mask);
1590
1591 for_each_online_cpu(cpu) {
1592 if (cpu == primary_cpu)
1593 continue;
1594
1595 error = cpu_down_maps_locked(cpu, CPUHP_OFFLINE);
1596 if (error) {
1597 pr_err("Failed to offline CPU%d - error=%d",
1598 cpu, error);
1599 break;
1600 }
1601 }
1602
1603 /*
1604 * Ensure all but the reboot CPU are offline.
1605 */
1606 BUG_ON(num_online_cpus() > 1);
1607
1608 /*
1609 * Make sure the CPUs won't be enabled by someone else after this
1610 * point. Kexec will reboot to a new kernel shortly resetting
1611 * everything along the way.
1612 */
1613 cpu_hotplug_disabled++;
1614
1615 cpu_maps_update_done();
1616}
1617
1618#else
1619#define takedown_cpu NULL
1620#endif /*CONFIG_HOTPLUG_CPU*/
1621
1622/**
1623 * notify_cpu_starting(cpu) - Invoke the callbacks on the starting CPU
1624 * @cpu: cpu that just started
1625 *
1626 * It must be called by the arch code on the new cpu, before the new cpu
1627 * enables interrupts and before the "boot" cpu returns from __cpu_up().
1628 */
1629void notify_cpu_starting(unsigned int cpu)
1630{
1631 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1632 enum cpuhp_state target = min((int)st->target, CPUHP_AP_ONLINE);
1633
1634 rcutree_report_cpu_starting(cpu); /* Enables RCU usage on this CPU. */
1635 cpumask_set_cpu(cpu, &cpus_booted_once_mask);
1636
1637 /*
1638 * STARTING must not fail!
1639 */
1640 cpuhp_invoke_callback_range_nofail(true, cpu, st, target);
1641}
1642
1643/*
1644 * Called from the idle task. Wake up the controlling task which brings the
1645 * hotplug thread of the upcoming CPU up and then delegates the rest of the
1646 * online bringup to the hotplug thread.
1647 */
1648void cpuhp_online_idle(enum cpuhp_state state)
1649{
1650 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
1651
1652 /* Happens for the boot cpu */
1653 if (state != CPUHP_AP_ONLINE_IDLE)
1654 return;
1655
1656 cpuhp_ap_update_sync_state(SYNC_STATE_ONLINE);
1657
1658 /*
1659 * Unpark the stopper thread before we start the idle loop (and start
1660 * scheduling); this ensures the stopper task is always available.
1661 */
1662 stop_machine_unpark(smp_processor_id());
1663
1664 st->state = CPUHP_AP_ONLINE_IDLE;
1665 complete_ap_thread(st, true);
1666}
1667
1668/* Requires cpu_add_remove_lock to be held */
1669static int _cpu_up(unsigned int cpu, int tasks_frozen, enum cpuhp_state target)
1670{
1671 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1672 struct task_struct *idle;
1673 int ret = 0;
1674
1675 cpus_write_lock();
1676
1677 if (!cpu_present(cpu)) {
1678 ret = -EINVAL;
1679 goto out;
1680 }
1681
1682 /*
1683 * The caller of cpu_up() might have raced with another
1684 * caller. Nothing to do.
1685 */
1686 if (st->state >= target)
1687 goto out;
1688
1689 if (st->state == CPUHP_OFFLINE) {
1690 /* Let it fail before we try to bring the cpu up */
1691 idle = idle_thread_get(cpu);
1692 if (IS_ERR(idle)) {
1693 ret = PTR_ERR(idle);
1694 goto out;
1695 }
1696
1697 /*
1698 * Reset stale stack state from the last time this CPU was online.
1699 */
1700 scs_task_reset(idle);
1701 kasan_unpoison_task_stack(idle);
1702 }
1703
1704 cpuhp_tasks_frozen = tasks_frozen;
1705
1706 cpuhp_set_state(cpu, st, target);
1707 /*
1708 * If the current CPU state is in the range of the AP hotplug thread,
1709 * then we need to kick the thread once more.
1710 */
1711 if (st->state > CPUHP_BRINGUP_CPU) {
1712 ret = cpuhp_kick_ap_work(cpu);
1713 /*
1714 * The AP side has done the error rollback already. Just
1715 * return the error code..
1716 */
1717 if (ret)
1718 goto out;
1719 }
1720
1721 /*
1722 * Try to reach the target state. We max out on the BP at
1723 * CPUHP_BRINGUP_CPU. After that the AP hotplug thread is
1724 * responsible for bringing it up to the target state.
1725 */
1726 target = min((int)target, CPUHP_BRINGUP_CPU);
1727 ret = cpuhp_up_callbacks(cpu, st, target);
1728out:
1729 cpus_write_unlock();
1730 arch_smt_update();
1731 cpu_up_down_serialize_trainwrecks(tasks_frozen);
1732 return ret;
1733}
1734
1735static int cpu_up(unsigned int cpu, enum cpuhp_state target)
1736{
1737 int err = 0;
1738
1739 if (!cpu_possible(cpu)) {
1740 pr_err("can't online cpu %d because it is not configured as may-hotadd at boot time\n",
1741 cpu);
1742 return -EINVAL;
1743 }
1744
1745 err = try_online_node(cpu_to_node(cpu));
1746 if (err)
1747 return err;
1748
1749 cpu_maps_update_begin();
1750
1751 if (cpu_hotplug_disabled) {
1752 err = -EBUSY;
1753 goto out;
1754 }
1755 if (!cpu_bootable(cpu)) {
1756 err = -EPERM;
1757 goto out;
1758 }
1759
1760 err = _cpu_up(cpu, 0, target);
1761out:
1762 cpu_maps_update_done();
1763 return err;
1764}
1765
1766/**
1767 * cpu_device_up - Bring up a cpu device
1768 * @dev: Pointer to the cpu device to online
1769 *
1770 * This function is meant to be used by device core cpu subsystem only.
1771 *
1772 * Other subsystems should use add_cpu() instead.
1773 *
1774 * Return: %0 on success or a negative errno code
1775 */
1776int cpu_device_up(struct device *dev)
1777{
1778 return cpu_up(dev->id, CPUHP_ONLINE);
1779}
1780
1781int add_cpu(unsigned int cpu)
1782{
1783 int ret;
1784
1785 lock_device_hotplug();
1786 ret = device_online(get_cpu_device(cpu));
1787 unlock_device_hotplug();
1788
1789 return ret;
1790}
1791EXPORT_SYMBOL_GPL(add_cpu);
1792
1793/**
1794 * bringup_hibernate_cpu - Bring up the CPU that we hibernated on
1795 * @sleep_cpu: The cpu we hibernated on and should be brought up.
1796 *
1797 * On some architectures like arm64, we can hibernate on any CPU, but on
1798 * wake up the CPU we hibernated on might be offline as a side effect of
1799 * using maxcpus= for example.
1800 *
1801 * Return: %0 on success or a negative errno code
1802 */
1803int bringup_hibernate_cpu(unsigned int sleep_cpu)
1804{
1805 int ret;
1806
1807 if (!cpu_online(sleep_cpu)) {
1808 pr_info("Hibernated on a CPU that is offline! Bringing CPU up.\n");
1809 ret = cpu_up(sleep_cpu, CPUHP_ONLINE);
1810 if (ret) {
1811 pr_err("Failed to bring hibernate-CPU up!\n");
1812 return ret;
1813 }
1814 }
1815 return 0;
1816}
1817
1818static void __init cpuhp_bringup_mask(const struct cpumask *mask, unsigned int ncpus,
1819 enum cpuhp_state target)
1820{
1821 unsigned int cpu;
1822
1823 for_each_cpu(cpu, mask) {
1824 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1825
1826 if (cpu_up(cpu, target) && can_rollback_cpu(st)) {
1827 /*
1828 * If this failed then cpu_up() might have only
1829 * rolled back to CPUHP_BP_KICK_AP for the final
1830 * online. Clean it up. NOOP if already rolled back.
1831 */
1832 WARN_ON(cpuhp_invoke_callback_range(false, cpu, st, CPUHP_OFFLINE));
1833 }
1834
1835 if (!--ncpus)
1836 break;
1837 }
1838}
1839
1840#ifdef CONFIG_HOTPLUG_PARALLEL
1841static bool __cpuhp_parallel_bringup __ro_after_init = true;
1842
1843static int __init parallel_bringup_parse_param(char *arg)
1844{
1845 return kstrtobool(arg, &__cpuhp_parallel_bringup);
1846}
1847early_param("cpuhp.parallel", parallel_bringup_parse_param);
1848
1849static inline bool cpuhp_smt_aware(void)
1850{
1851 return cpu_smt_max_threads > 1;
1852}
1853
1854static inline const struct cpumask *cpuhp_get_primary_thread_mask(void)
1855{
1856 return cpu_primary_thread_mask;
1857}
1858
1859/*
1860 * On architectures which have enabled parallel bringup this invokes all BP
1861 * prepare states for each of the to be onlined APs first. The last state
1862 * sends the startup IPI to the APs. The APs proceed through the low level
1863 * bringup code in parallel and then wait for the control CPU to release
1864 * them one by one for the final onlining procedure.
1865 *
1866 * This avoids waiting for each AP to respond to the startup IPI in
1867 * CPUHP_BRINGUP_CPU.
1868 */
1869static bool __init cpuhp_bringup_cpus_parallel(unsigned int ncpus)
1870{
1871 const struct cpumask *mask = cpu_present_mask;
1872
1873 if (__cpuhp_parallel_bringup)
1874 __cpuhp_parallel_bringup = arch_cpuhp_init_parallel_bringup();
1875 if (!__cpuhp_parallel_bringup)
1876 return false;
1877
1878 if (cpuhp_smt_aware()) {
1879 const struct cpumask *pmask = cpuhp_get_primary_thread_mask();
1880 static struct cpumask tmp_mask __initdata;
1881
1882 /*
1883 * X86 requires to prevent that SMT siblings stopped while
1884 * the primary thread does a microcode update for various
1885 * reasons. Bring the primary threads up first.
1886 */
1887 cpumask_and(&tmp_mask, mask, pmask);
1888 cpuhp_bringup_mask(&tmp_mask, ncpus, CPUHP_BP_KICK_AP);
1889 cpuhp_bringup_mask(&tmp_mask, ncpus, CPUHP_ONLINE);
1890 /* Account for the online CPUs */
1891 ncpus -= num_online_cpus();
1892 if (!ncpus)
1893 return true;
1894 /* Create the mask for secondary CPUs */
1895 cpumask_andnot(&tmp_mask, mask, pmask);
1896 mask = &tmp_mask;
1897 }
1898
1899 /* Bring the not-yet started CPUs up */
1900 cpuhp_bringup_mask(mask, ncpus, CPUHP_BP_KICK_AP);
1901 cpuhp_bringup_mask(mask, ncpus, CPUHP_ONLINE);
1902 return true;
1903}
1904#else
1905static inline bool cpuhp_bringup_cpus_parallel(unsigned int ncpus) { return false; }
1906#endif /* CONFIG_HOTPLUG_PARALLEL */
1907
1908void __init bringup_nonboot_cpus(unsigned int max_cpus)
1909{
1910 /* Try parallel bringup optimization if enabled */
1911 if (cpuhp_bringup_cpus_parallel(max_cpus))
1912 return;
1913
1914 /* Full per CPU serialized bringup */
1915 cpuhp_bringup_mask(cpu_present_mask, max_cpus, CPUHP_ONLINE);
1916}
1917
1918#ifdef CONFIG_PM_SLEEP_SMP
1919static cpumask_var_t frozen_cpus;
1920
1921int freeze_secondary_cpus(int primary)
1922{
1923 int cpu, error = 0;
1924
1925 cpu_maps_update_begin();
1926 if (primary == -1) {
1927 primary = cpumask_first(cpu_online_mask);
1928 if (!housekeeping_cpu(primary, HK_TYPE_TIMER))
1929 primary = housekeeping_any_cpu(HK_TYPE_TIMER);
1930 } else {
1931 if (!cpu_online(primary))
1932 primary = cpumask_first(cpu_online_mask);
1933 }
1934
1935 /*
1936 * We take down all of the non-boot CPUs in one shot to avoid races
1937 * with the userspace trying to use the CPU hotplug at the same time
1938 */
1939 cpumask_clear(frozen_cpus);
1940
1941 pr_info("Disabling non-boot CPUs ...\n");
1942 for_each_online_cpu(cpu) {
1943 if (cpu == primary)
1944 continue;
1945
1946 if (pm_wakeup_pending()) {
1947 pr_info("Wakeup pending. Abort CPU freeze\n");
1948 error = -EBUSY;
1949 break;
1950 }
1951
1952 trace_suspend_resume(TPS("CPU_OFF"), cpu, true);
1953 error = _cpu_down(cpu, 1, CPUHP_OFFLINE);
1954 trace_suspend_resume(TPS("CPU_OFF"), cpu, false);
1955 if (!error)
1956 cpumask_set_cpu(cpu, frozen_cpus);
1957 else {
1958 pr_err("Error taking CPU%d down: %d\n", cpu, error);
1959 break;
1960 }
1961 }
1962
1963 if (!error)
1964 BUG_ON(num_online_cpus() > 1);
1965 else
1966 pr_err("Non-boot CPUs are not disabled\n");
1967
1968 /*
1969 * Make sure the CPUs won't be enabled by someone else. We need to do
1970 * this even in case of failure as all freeze_secondary_cpus() users are
1971 * supposed to do thaw_secondary_cpus() on the failure path.
1972 */
1973 cpu_hotplug_disabled++;
1974
1975 cpu_maps_update_done();
1976 return error;
1977}
1978
1979void __weak arch_thaw_secondary_cpus_begin(void)
1980{
1981}
1982
1983void __weak arch_thaw_secondary_cpus_end(void)
1984{
1985}
1986
1987void thaw_secondary_cpus(void)
1988{
1989 int cpu, error;
1990
1991 /* Allow everyone to use the CPU hotplug again */
1992 cpu_maps_update_begin();
1993 __cpu_hotplug_enable();
1994 if (cpumask_empty(frozen_cpus))
1995 goto out;
1996
1997 pr_info("Enabling non-boot CPUs ...\n");
1998
1999 arch_thaw_secondary_cpus_begin();
2000
2001 for_each_cpu(cpu, frozen_cpus) {
2002 trace_suspend_resume(TPS("CPU_ON"), cpu, true);
2003 error = _cpu_up(cpu, 1, CPUHP_ONLINE);
2004 trace_suspend_resume(TPS("CPU_ON"), cpu, false);
2005 if (!error) {
2006 pr_info("CPU%d is up\n", cpu);
2007 continue;
2008 }
2009 pr_warn("Error taking CPU%d up: %d\n", cpu, error);
2010 }
2011
2012 arch_thaw_secondary_cpus_end();
2013
2014 cpumask_clear(frozen_cpus);
2015out:
2016 cpu_maps_update_done();
2017}
2018
2019static int __init alloc_frozen_cpus(void)
2020{
2021 if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
2022 return -ENOMEM;
2023 return 0;
2024}
2025core_initcall(alloc_frozen_cpus);
2026
2027/*
2028 * When callbacks for CPU hotplug notifications are being executed, we must
2029 * ensure that the state of the system with respect to the tasks being frozen
2030 * or not, as reported by the notification, remains unchanged *throughout the
2031 * duration* of the execution of the callbacks.
2032 * Hence we need to prevent the freezer from racing with regular CPU hotplug.
2033 *
2034 * This synchronization is implemented by mutually excluding regular CPU
2035 * hotplug and Suspend/Hibernate call paths by hooking onto the Suspend/
2036 * Hibernate notifications.
2037 */
2038static int
2039cpu_hotplug_pm_callback(struct notifier_block *nb,
2040 unsigned long action, void *ptr)
2041{
2042 switch (action) {
2043
2044 case PM_SUSPEND_PREPARE:
2045 case PM_HIBERNATION_PREPARE:
2046 cpu_hotplug_disable();
2047 break;
2048
2049 case PM_POST_SUSPEND:
2050 case PM_POST_HIBERNATION:
2051 cpu_hotplug_enable();
2052 break;
2053
2054 default:
2055 return NOTIFY_DONE;
2056 }
2057
2058 return NOTIFY_OK;
2059}
2060
2061
2062static int __init cpu_hotplug_pm_sync_init(void)
2063{
2064 /*
2065 * cpu_hotplug_pm_callback has higher priority than x86
2066 * bsp_pm_callback which depends on cpu_hotplug_pm_callback
2067 * to disable cpu hotplug to avoid cpu hotplug race.
2068 */
2069 pm_notifier(cpu_hotplug_pm_callback, 0);
2070 return 0;
2071}
2072core_initcall(cpu_hotplug_pm_sync_init);
2073
2074#endif /* CONFIG_PM_SLEEP_SMP */
2075
2076int __boot_cpu_id;
2077
2078#endif /* CONFIG_SMP */
2079
2080/* Boot processor state steps */
2081static struct cpuhp_step cpuhp_hp_states[] = {
2082 [CPUHP_OFFLINE] = {
2083 .name = "offline",
2084 .startup.single = NULL,
2085 .teardown.single = NULL,
2086 },
2087#ifdef CONFIG_SMP
2088 [CPUHP_CREATE_THREADS]= {
2089 .name = "threads:prepare",
2090 .startup.single = smpboot_create_threads,
2091 .teardown.single = NULL,
2092 .cant_stop = true,
2093 },
2094 [CPUHP_PERF_PREPARE] = {
2095 .name = "perf:prepare",
2096 .startup.single = perf_event_init_cpu,
2097 .teardown.single = perf_event_exit_cpu,
2098 },
2099 [CPUHP_RANDOM_PREPARE] = {
2100 .name = "random:prepare",
2101 .startup.single = random_prepare_cpu,
2102 .teardown.single = NULL,
2103 },
2104 [CPUHP_WORKQUEUE_PREP] = {
2105 .name = "workqueue:prepare",
2106 .startup.single = workqueue_prepare_cpu,
2107 .teardown.single = NULL,
2108 },
2109 [CPUHP_HRTIMERS_PREPARE] = {
2110 .name = "hrtimers:prepare",
2111 .startup.single = hrtimers_prepare_cpu,
2112 .teardown.single = NULL,
2113 },
2114 [CPUHP_SMPCFD_PREPARE] = {
2115 .name = "smpcfd:prepare",
2116 .startup.single = smpcfd_prepare_cpu,
2117 .teardown.single = smpcfd_dead_cpu,
2118 },
2119 [CPUHP_RELAY_PREPARE] = {
2120 .name = "relay:prepare",
2121 .startup.single = relay_prepare_cpu,
2122 .teardown.single = NULL,
2123 },
2124 [CPUHP_RCUTREE_PREP] = {
2125 .name = "RCU/tree:prepare",
2126 .startup.single = rcutree_prepare_cpu,
2127 .teardown.single = rcutree_dead_cpu,
2128 },
2129 /*
2130 * On the tear-down path, timers_dead_cpu() must be invoked
2131 * before blk_mq_queue_reinit_notify() from notify_dead(),
2132 * otherwise a RCU stall occurs.
2133 */
2134 [CPUHP_TIMERS_PREPARE] = {
2135 .name = "timers:prepare",
2136 .startup.single = timers_prepare_cpu,
2137 .teardown.single = timers_dead_cpu,
2138 },
2139
2140#ifdef CONFIG_HOTPLUG_SPLIT_STARTUP
2141 /*
2142 * Kicks the AP alive. AP will wait in cpuhp_ap_sync_alive() until
2143 * the next step will release it.
2144 */
2145 [CPUHP_BP_KICK_AP] = {
2146 .name = "cpu:kick_ap",
2147 .startup.single = cpuhp_kick_ap_alive,
2148 },
2149
2150 /*
2151 * Waits for the AP to reach cpuhp_ap_sync_alive() and then
2152 * releases it for the complete bringup.
2153 */
2154 [CPUHP_BRINGUP_CPU] = {
2155 .name = "cpu:bringup",
2156 .startup.single = cpuhp_bringup_ap,
2157 .teardown.single = finish_cpu,
2158 .cant_stop = true,
2159 },
2160#else
2161 /*
2162 * All-in-one CPU bringup state which includes the kick alive.
2163 */
2164 [CPUHP_BRINGUP_CPU] = {
2165 .name = "cpu:bringup",
2166 .startup.single = bringup_cpu,
2167 .teardown.single = finish_cpu,
2168 .cant_stop = true,
2169 },
2170#endif
2171 /* Final state before CPU kills itself */
2172 [CPUHP_AP_IDLE_DEAD] = {
2173 .name = "idle:dead",
2174 },
2175 /*
2176 * Last state before CPU enters the idle loop to die. Transient state
2177 * for synchronization.
2178 */
2179 [CPUHP_AP_OFFLINE] = {
2180 .name = "ap:offline",
2181 .cant_stop = true,
2182 },
2183 /* First state is scheduler control. Interrupts are disabled */
2184 [CPUHP_AP_SCHED_STARTING] = {
2185 .name = "sched:starting",
2186 .startup.single = sched_cpu_starting,
2187 .teardown.single = sched_cpu_dying,
2188 },
2189 [CPUHP_AP_RCUTREE_DYING] = {
2190 .name = "RCU/tree:dying",
2191 .startup.single = NULL,
2192 .teardown.single = rcutree_dying_cpu,
2193 },
2194 [CPUHP_AP_SMPCFD_DYING] = {
2195 .name = "smpcfd:dying",
2196 .startup.single = NULL,
2197 .teardown.single = smpcfd_dying_cpu,
2198 },
2199 [CPUHP_AP_HRTIMERS_DYING] = {
2200 .name = "hrtimers:dying",
2201 .startup.single = NULL,
2202 .teardown.single = hrtimers_cpu_dying,
2203 },
2204 [CPUHP_AP_TICK_DYING] = {
2205 .name = "tick:dying",
2206 .startup.single = NULL,
2207 .teardown.single = tick_cpu_dying,
2208 },
2209 /* Entry state on starting. Interrupts enabled from here on. Transient
2210 * state for synchronsization */
2211 [CPUHP_AP_ONLINE] = {
2212 .name = "ap:online",
2213 },
2214 /*
2215 * Handled on control processor until the plugged processor manages
2216 * this itself.
2217 */
2218 [CPUHP_TEARDOWN_CPU] = {
2219 .name = "cpu:teardown",
2220 .startup.single = NULL,
2221 .teardown.single = takedown_cpu,
2222 .cant_stop = true,
2223 },
2224
2225 [CPUHP_AP_SCHED_WAIT_EMPTY] = {
2226 .name = "sched:waitempty",
2227 .startup.single = NULL,
2228 .teardown.single = sched_cpu_wait_empty,
2229 },
2230
2231 /* Handle smpboot threads park/unpark */
2232 [CPUHP_AP_SMPBOOT_THREADS] = {
2233 .name = "smpboot/threads:online",
2234 .startup.single = smpboot_unpark_threads,
2235 .teardown.single = smpboot_park_threads,
2236 },
2237 [CPUHP_AP_IRQ_AFFINITY_ONLINE] = {
2238 .name = "irq/affinity:online",
2239 .startup.single = irq_affinity_online_cpu,
2240 .teardown.single = NULL,
2241 },
2242 [CPUHP_AP_PERF_ONLINE] = {
2243 .name = "perf:online",
2244 .startup.single = perf_event_init_cpu,
2245 .teardown.single = perf_event_exit_cpu,
2246 },
2247 [CPUHP_AP_WATCHDOG_ONLINE] = {
2248 .name = "lockup_detector:online",
2249 .startup.single = lockup_detector_online_cpu,
2250 .teardown.single = lockup_detector_offline_cpu,
2251 },
2252 [CPUHP_AP_WORKQUEUE_ONLINE] = {
2253 .name = "workqueue:online",
2254 .startup.single = workqueue_online_cpu,
2255 .teardown.single = workqueue_offline_cpu,
2256 },
2257 [CPUHP_AP_RANDOM_ONLINE] = {
2258 .name = "random:online",
2259 .startup.single = random_online_cpu,
2260 .teardown.single = NULL,
2261 },
2262 [CPUHP_AP_RCUTREE_ONLINE] = {
2263 .name = "RCU/tree:online",
2264 .startup.single = rcutree_online_cpu,
2265 .teardown.single = rcutree_offline_cpu,
2266 },
2267#endif
2268 /*
2269 * The dynamically registered state space is here
2270 */
2271
2272#ifdef CONFIG_SMP
2273 /* Last state is scheduler control setting the cpu active */
2274 [CPUHP_AP_ACTIVE] = {
2275 .name = "sched:active",
2276 .startup.single = sched_cpu_activate,
2277 .teardown.single = sched_cpu_deactivate,
2278 },
2279#endif
2280
2281 /* CPU is fully up and running. */
2282 [CPUHP_ONLINE] = {
2283 .name = "online",
2284 .startup.single = NULL,
2285 .teardown.single = NULL,
2286 },
2287};
2288
2289/* Sanity check for callbacks */
2290static int cpuhp_cb_check(enum cpuhp_state state)
2291{
2292 if (state <= CPUHP_OFFLINE || state >= CPUHP_ONLINE)
2293 return -EINVAL;
2294 return 0;
2295}
2296
2297/*
2298 * Returns a free for dynamic slot assignment of the Online state. The states
2299 * are protected by the cpuhp_slot_states mutex and an empty slot is identified
2300 * by having no name assigned.
2301 */
2302static int cpuhp_reserve_state(enum cpuhp_state state)
2303{
2304 enum cpuhp_state i, end;
2305 struct cpuhp_step *step;
2306
2307 switch (state) {
2308 case CPUHP_AP_ONLINE_DYN:
2309 step = cpuhp_hp_states + CPUHP_AP_ONLINE_DYN;
2310 end = CPUHP_AP_ONLINE_DYN_END;
2311 break;
2312 case CPUHP_BP_PREPARE_DYN:
2313 step = cpuhp_hp_states + CPUHP_BP_PREPARE_DYN;
2314 end = CPUHP_BP_PREPARE_DYN_END;
2315 break;
2316 default:
2317 return -EINVAL;
2318 }
2319
2320 for (i = state; i <= end; i++, step++) {
2321 if (!step->name)
2322 return i;
2323 }
2324 WARN(1, "No more dynamic states available for CPU hotplug\n");
2325 return -ENOSPC;
2326}
2327
2328static int cpuhp_store_callbacks(enum cpuhp_state state, const char *name,
2329 int (*startup)(unsigned int cpu),
2330 int (*teardown)(unsigned int cpu),
2331 bool multi_instance)
2332{
2333 /* (Un)Install the callbacks for further cpu hotplug operations */
2334 struct cpuhp_step *sp;
2335 int ret = 0;
2336
2337 /*
2338 * If name is NULL, then the state gets removed.
2339 *
2340 * CPUHP_AP_ONLINE_DYN and CPUHP_BP_PREPARE_DYN are handed out on
2341 * the first allocation from these dynamic ranges, so the removal
2342 * would trigger a new allocation and clear the wrong (already
2343 * empty) state, leaving the callbacks of the to be cleared state
2344 * dangling, which causes wreckage on the next hotplug operation.
2345 */
2346 if (name && (state == CPUHP_AP_ONLINE_DYN ||
2347 state == CPUHP_BP_PREPARE_DYN)) {
2348 ret = cpuhp_reserve_state(state);
2349 if (ret < 0)
2350 return ret;
2351 state = ret;
2352 }
2353 sp = cpuhp_get_step(state);
2354 if (name && sp->name)
2355 return -EBUSY;
2356
2357 sp->startup.single = startup;
2358 sp->teardown.single = teardown;
2359 sp->name = name;
2360 sp->multi_instance = multi_instance;
2361 INIT_HLIST_HEAD(&sp->list);
2362 return ret;
2363}
2364
2365static void *cpuhp_get_teardown_cb(enum cpuhp_state state)
2366{
2367 return cpuhp_get_step(state)->teardown.single;
2368}
2369
2370/*
2371 * Call the startup/teardown function for a step either on the AP or
2372 * on the current CPU.
2373 */
2374static int cpuhp_issue_call(int cpu, enum cpuhp_state state, bool bringup,
2375 struct hlist_node *node)
2376{
2377 struct cpuhp_step *sp = cpuhp_get_step(state);
2378 int ret;
2379
2380 /*
2381 * If there's nothing to do, we done.
2382 * Relies on the union for multi_instance.
2383 */
2384 if (cpuhp_step_empty(bringup, sp))
2385 return 0;
2386 /*
2387 * The non AP bound callbacks can fail on bringup. On teardown
2388 * e.g. module removal we crash for now.
2389 */
2390#ifdef CONFIG_SMP
2391 if (cpuhp_is_ap_state(state))
2392 ret = cpuhp_invoke_ap_callback(cpu, state, bringup, node);
2393 else
2394 ret = cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
2395#else
2396 ret = cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
2397#endif
2398 BUG_ON(ret && !bringup);
2399 return ret;
2400}
2401
2402/*
2403 * Called from __cpuhp_setup_state on a recoverable failure.
2404 *
2405 * Note: The teardown callbacks for rollback are not allowed to fail!
2406 */
2407static void cpuhp_rollback_install(int failedcpu, enum cpuhp_state state,
2408 struct hlist_node *node)
2409{
2410 int cpu;
2411
2412 /* Roll back the already executed steps on the other cpus */
2413 for_each_present_cpu(cpu) {
2414 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
2415 int cpustate = st->state;
2416
2417 if (cpu >= failedcpu)
2418 break;
2419
2420 /* Did we invoke the startup call on that cpu ? */
2421 if (cpustate >= state)
2422 cpuhp_issue_call(cpu, state, false, node);
2423 }
2424}
2425
2426int __cpuhp_state_add_instance_cpuslocked(enum cpuhp_state state,
2427 struct hlist_node *node,
2428 bool invoke)
2429{
2430 struct cpuhp_step *sp;
2431 int cpu;
2432 int ret;
2433
2434 lockdep_assert_cpus_held();
2435
2436 sp = cpuhp_get_step(state);
2437 if (sp->multi_instance == false)
2438 return -EINVAL;
2439
2440 mutex_lock(&cpuhp_state_mutex);
2441
2442 if (!invoke || !sp->startup.multi)
2443 goto add_node;
2444
2445 /*
2446 * Try to call the startup callback for each present cpu
2447 * depending on the hotplug state of the cpu.
2448 */
2449 for_each_present_cpu(cpu) {
2450 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
2451 int cpustate = st->state;
2452
2453 if (cpustate < state)
2454 continue;
2455
2456 ret = cpuhp_issue_call(cpu, state, true, node);
2457 if (ret) {
2458 if (sp->teardown.multi)
2459 cpuhp_rollback_install(cpu, state, node);
2460 goto unlock;
2461 }
2462 }
2463add_node:
2464 ret = 0;
2465 hlist_add_head(node, &sp->list);
2466unlock:
2467 mutex_unlock(&cpuhp_state_mutex);
2468 return ret;
2469}
2470
2471int __cpuhp_state_add_instance(enum cpuhp_state state, struct hlist_node *node,
2472 bool invoke)
2473{
2474 int ret;
2475
2476 cpus_read_lock();
2477 ret = __cpuhp_state_add_instance_cpuslocked(state, node, invoke);
2478 cpus_read_unlock();
2479 return ret;
2480}
2481EXPORT_SYMBOL_GPL(__cpuhp_state_add_instance);
2482
2483/**
2484 * __cpuhp_setup_state_cpuslocked - Setup the callbacks for an hotplug machine state
2485 * @state: The state to setup
2486 * @name: Name of the step
2487 * @invoke: If true, the startup function is invoked for cpus where
2488 * cpu state >= @state
2489 * @startup: startup callback function
2490 * @teardown: teardown callback function
2491 * @multi_instance: State is set up for multiple instances which get
2492 * added afterwards.
2493 *
2494 * The caller needs to hold cpus read locked while calling this function.
2495 * Return:
2496 * On success:
2497 * Positive state number if @state is CPUHP_AP_ONLINE_DYN;
2498 * 0 for all other states
2499 * On failure: proper (negative) error code
2500 */
2501int __cpuhp_setup_state_cpuslocked(enum cpuhp_state state,
2502 const char *name, bool invoke,
2503 int (*startup)(unsigned int cpu),
2504 int (*teardown)(unsigned int cpu),
2505 bool multi_instance)
2506{
2507 int cpu, ret = 0;
2508 bool dynstate;
2509
2510 lockdep_assert_cpus_held();
2511
2512 if (cpuhp_cb_check(state) || !name)
2513 return -EINVAL;
2514
2515 mutex_lock(&cpuhp_state_mutex);
2516
2517 ret = cpuhp_store_callbacks(state, name, startup, teardown,
2518 multi_instance);
2519
2520 dynstate = state == CPUHP_AP_ONLINE_DYN;
2521 if (ret > 0 && dynstate) {
2522 state = ret;
2523 ret = 0;
2524 }
2525
2526 if (ret || !invoke || !startup)
2527 goto out;
2528
2529 /*
2530 * Try to call the startup callback for each present cpu
2531 * depending on the hotplug state of the cpu.
2532 */
2533 for_each_present_cpu(cpu) {
2534 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
2535 int cpustate = st->state;
2536
2537 if (cpustate < state)
2538 continue;
2539
2540 ret = cpuhp_issue_call(cpu, state, true, NULL);
2541 if (ret) {
2542 if (teardown)
2543 cpuhp_rollback_install(cpu, state, NULL);
2544 cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
2545 goto out;
2546 }
2547 }
2548out:
2549 mutex_unlock(&cpuhp_state_mutex);
2550 /*
2551 * If the requested state is CPUHP_AP_ONLINE_DYN, return the
2552 * dynamically allocated state in case of success.
2553 */
2554 if (!ret && dynstate)
2555 return state;
2556 return ret;
2557}
2558EXPORT_SYMBOL(__cpuhp_setup_state_cpuslocked);
2559
2560int __cpuhp_setup_state(enum cpuhp_state state,
2561 const char *name, bool invoke,
2562 int (*startup)(unsigned int cpu),
2563 int (*teardown)(unsigned int cpu),
2564 bool multi_instance)
2565{
2566 int ret;
2567
2568 cpus_read_lock();
2569 ret = __cpuhp_setup_state_cpuslocked(state, name, invoke, startup,
2570 teardown, multi_instance);
2571 cpus_read_unlock();
2572 return ret;
2573}
2574EXPORT_SYMBOL(__cpuhp_setup_state);
2575
2576int __cpuhp_state_remove_instance(enum cpuhp_state state,
2577 struct hlist_node *node, bool invoke)
2578{
2579 struct cpuhp_step *sp = cpuhp_get_step(state);
2580 int cpu;
2581
2582 BUG_ON(cpuhp_cb_check(state));
2583
2584 if (!sp->multi_instance)
2585 return -EINVAL;
2586
2587 cpus_read_lock();
2588 mutex_lock(&cpuhp_state_mutex);
2589
2590 if (!invoke || !cpuhp_get_teardown_cb(state))
2591 goto remove;
2592 /*
2593 * Call the teardown callback for each present cpu depending
2594 * on the hotplug state of the cpu. This function is not
2595 * allowed to fail currently!
2596 */
2597 for_each_present_cpu(cpu) {
2598 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
2599 int cpustate = st->state;
2600
2601 if (cpustate >= state)
2602 cpuhp_issue_call(cpu, state, false, node);
2603 }
2604
2605remove:
2606 hlist_del(node);
2607 mutex_unlock(&cpuhp_state_mutex);
2608 cpus_read_unlock();
2609
2610 return 0;
2611}
2612EXPORT_SYMBOL_GPL(__cpuhp_state_remove_instance);
2613
2614/**
2615 * __cpuhp_remove_state_cpuslocked - Remove the callbacks for an hotplug machine state
2616 * @state: The state to remove
2617 * @invoke: If true, the teardown function is invoked for cpus where
2618 * cpu state >= @state
2619 *
2620 * The caller needs to hold cpus read locked while calling this function.
2621 * The teardown callback is currently not allowed to fail. Think
2622 * about module removal!
2623 */
2624void __cpuhp_remove_state_cpuslocked(enum cpuhp_state state, bool invoke)
2625{
2626 struct cpuhp_step *sp = cpuhp_get_step(state);
2627 int cpu;
2628
2629 BUG_ON(cpuhp_cb_check(state));
2630
2631 lockdep_assert_cpus_held();
2632
2633 mutex_lock(&cpuhp_state_mutex);
2634 if (sp->multi_instance) {
2635 WARN(!hlist_empty(&sp->list),
2636 "Error: Removing state %d which has instances left.\n",
2637 state);
2638 goto remove;
2639 }
2640
2641 if (!invoke || !cpuhp_get_teardown_cb(state))
2642 goto remove;
2643
2644 /*
2645 * Call the teardown callback for each present cpu depending
2646 * on the hotplug state of the cpu. This function is not
2647 * allowed to fail currently!
2648 */
2649 for_each_present_cpu(cpu) {
2650 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
2651 int cpustate = st->state;
2652
2653 if (cpustate >= state)
2654 cpuhp_issue_call(cpu, state, false, NULL);
2655 }
2656remove:
2657 cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
2658 mutex_unlock(&cpuhp_state_mutex);
2659}
2660EXPORT_SYMBOL(__cpuhp_remove_state_cpuslocked);
2661
2662void __cpuhp_remove_state(enum cpuhp_state state, bool invoke)
2663{
2664 cpus_read_lock();
2665 __cpuhp_remove_state_cpuslocked(state, invoke);
2666 cpus_read_unlock();
2667}
2668EXPORT_SYMBOL(__cpuhp_remove_state);
2669
2670#ifdef CONFIG_HOTPLUG_SMT
2671static void cpuhp_offline_cpu_device(unsigned int cpu)
2672{
2673 struct device *dev = get_cpu_device(cpu);
2674
2675 dev->offline = true;
2676 /* Tell user space about the state change */
2677 kobject_uevent(&dev->kobj, KOBJ_OFFLINE);
2678}
2679
2680static void cpuhp_online_cpu_device(unsigned int cpu)
2681{
2682 struct device *dev = get_cpu_device(cpu);
2683
2684 dev->offline = false;
2685 /* Tell user space about the state change */
2686 kobject_uevent(&dev->kobj, KOBJ_ONLINE);
2687}
2688
2689int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval)
2690{
2691 int cpu, ret = 0;
2692
2693 cpu_maps_update_begin();
2694 for_each_online_cpu(cpu) {
2695 if (topology_is_primary_thread(cpu))
2696 continue;
2697 /*
2698 * Disable can be called with CPU_SMT_ENABLED when changing
2699 * from a higher to lower number of SMT threads per core.
2700 */
2701 if (ctrlval == CPU_SMT_ENABLED && cpu_smt_thread_allowed(cpu))
2702 continue;
2703 ret = cpu_down_maps_locked(cpu, CPUHP_OFFLINE);
2704 if (ret)
2705 break;
2706 /*
2707 * As this needs to hold the cpu maps lock it's impossible
2708 * to call device_offline() because that ends up calling
2709 * cpu_down() which takes cpu maps lock. cpu maps lock
2710 * needs to be held as this might race against in kernel
2711 * abusers of the hotplug machinery (thermal management).
2712 *
2713 * So nothing would update device:offline state. That would
2714 * leave the sysfs entry stale and prevent onlining after
2715 * smt control has been changed to 'off' again. This is
2716 * called under the sysfs hotplug lock, so it is properly
2717 * serialized against the regular offline usage.
2718 */
2719 cpuhp_offline_cpu_device(cpu);
2720 }
2721 if (!ret)
2722 cpu_smt_control = ctrlval;
2723 cpu_maps_update_done();
2724 return ret;
2725}
2726
2727int cpuhp_smt_enable(void)
2728{
2729 int cpu, ret = 0;
2730
2731 cpu_maps_update_begin();
2732 cpu_smt_control = CPU_SMT_ENABLED;
2733 for_each_present_cpu(cpu) {
2734 /* Skip online CPUs and CPUs on offline nodes */
2735 if (cpu_online(cpu) || !node_online(cpu_to_node(cpu)))
2736 continue;
2737 if (!cpu_smt_thread_allowed(cpu))
2738 continue;
2739 ret = _cpu_up(cpu, 0, CPUHP_ONLINE);
2740 if (ret)
2741 break;
2742 /* See comment in cpuhp_smt_disable() */
2743 cpuhp_online_cpu_device(cpu);
2744 }
2745 cpu_maps_update_done();
2746 return ret;
2747}
2748#endif
2749
2750#if defined(CONFIG_SYSFS) && defined(CONFIG_HOTPLUG_CPU)
2751static ssize_t state_show(struct device *dev,
2752 struct device_attribute *attr, char *buf)
2753{
2754 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2755
2756 return sprintf(buf, "%d\n", st->state);
2757}
2758static DEVICE_ATTR_RO(state);
2759
2760static ssize_t target_store(struct device *dev, struct device_attribute *attr,
2761 const char *buf, size_t count)
2762{
2763 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2764 struct cpuhp_step *sp;
2765 int target, ret;
2766
2767 ret = kstrtoint(buf, 10, &target);
2768 if (ret)
2769 return ret;
2770
2771#ifdef CONFIG_CPU_HOTPLUG_STATE_CONTROL
2772 if (target < CPUHP_OFFLINE || target > CPUHP_ONLINE)
2773 return -EINVAL;
2774#else
2775 if (target != CPUHP_OFFLINE && target != CPUHP_ONLINE)
2776 return -EINVAL;
2777#endif
2778
2779 ret = lock_device_hotplug_sysfs();
2780 if (ret)
2781 return ret;
2782
2783 mutex_lock(&cpuhp_state_mutex);
2784 sp = cpuhp_get_step(target);
2785 ret = !sp->name || sp->cant_stop ? -EINVAL : 0;
2786 mutex_unlock(&cpuhp_state_mutex);
2787 if (ret)
2788 goto out;
2789
2790 if (st->state < target)
2791 ret = cpu_up(dev->id, target);
2792 else if (st->state > target)
2793 ret = cpu_down(dev->id, target);
2794 else if (WARN_ON(st->target != target))
2795 st->target = target;
2796out:
2797 unlock_device_hotplug();
2798 return ret ? ret : count;
2799}
2800
2801static ssize_t target_show(struct device *dev,
2802 struct device_attribute *attr, char *buf)
2803{
2804 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2805
2806 return sprintf(buf, "%d\n", st->target);
2807}
2808static DEVICE_ATTR_RW(target);
2809
2810static ssize_t fail_store(struct device *dev, struct device_attribute *attr,
2811 const char *buf, size_t count)
2812{
2813 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2814 struct cpuhp_step *sp;
2815 int fail, ret;
2816
2817 ret = kstrtoint(buf, 10, &fail);
2818 if (ret)
2819 return ret;
2820
2821 if (fail == CPUHP_INVALID) {
2822 st->fail = fail;
2823 return count;
2824 }
2825
2826 if (fail < CPUHP_OFFLINE || fail > CPUHP_ONLINE)
2827 return -EINVAL;
2828
2829 /*
2830 * Cannot fail STARTING/DYING callbacks.
2831 */
2832 if (cpuhp_is_atomic_state(fail))
2833 return -EINVAL;
2834
2835 /*
2836 * DEAD callbacks cannot fail...
2837 * ... neither can CPUHP_BRINGUP_CPU during hotunplug. The latter
2838 * triggering STARTING callbacks, a failure in this state would
2839 * hinder rollback.
2840 */
2841 if (fail <= CPUHP_BRINGUP_CPU && st->state > CPUHP_BRINGUP_CPU)
2842 return -EINVAL;
2843
2844 /*
2845 * Cannot fail anything that doesn't have callbacks.
2846 */
2847 mutex_lock(&cpuhp_state_mutex);
2848 sp = cpuhp_get_step(fail);
2849 if (!sp->startup.single && !sp->teardown.single)
2850 ret = -EINVAL;
2851 mutex_unlock(&cpuhp_state_mutex);
2852 if (ret)
2853 return ret;
2854
2855 st->fail = fail;
2856
2857 return count;
2858}
2859
2860static ssize_t fail_show(struct device *dev,
2861 struct device_attribute *attr, char *buf)
2862{
2863 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2864
2865 return sprintf(buf, "%d\n", st->fail);
2866}
2867
2868static DEVICE_ATTR_RW(fail);
2869
2870static struct attribute *cpuhp_cpu_attrs[] = {
2871 &dev_attr_state.attr,
2872 &dev_attr_target.attr,
2873 &dev_attr_fail.attr,
2874 NULL
2875};
2876
2877static const struct attribute_group cpuhp_cpu_attr_group = {
2878 .attrs = cpuhp_cpu_attrs,
2879 .name = "hotplug",
2880 NULL
2881};
2882
2883static ssize_t states_show(struct device *dev,
2884 struct device_attribute *attr, char *buf)
2885{
2886 ssize_t cur, res = 0;
2887 int i;
2888
2889 mutex_lock(&cpuhp_state_mutex);
2890 for (i = CPUHP_OFFLINE; i <= CPUHP_ONLINE; i++) {
2891 struct cpuhp_step *sp = cpuhp_get_step(i);
2892
2893 if (sp->name) {
2894 cur = sprintf(buf, "%3d: %s\n", i, sp->name);
2895 buf += cur;
2896 res += cur;
2897 }
2898 }
2899 mutex_unlock(&cpuhp_state_mutex);
2900 return res;
2901}
2902static DEVICE_ATTR_RO(states);
2903
2904static struct attribute *cpuhp_cpu_root_attrs[] = {
2905 &dev_attr_states.attr,
2906 NULL
2907};
2908
2909static const struct attribute_group cpuhp_cpu_root_attr_group = {
2910 .attrs = cpuhp_cpu_root_attrs,
2911 .name = "hotplug",
2912 NULL
2913};
2914
2915#ifdef CONFIG_HOTPLUG_SMT
2916
2917static bool cpu_smt_num_threads_valid(unsigned int threads)
2918{
2919 if (IS_ENABLED(CONFIG_SMT_NUM_THREADS_DYNAMIC))
2920 return threads >= 1 && threads <= cpu_smt_max_threads;
2921 return threads == 1 || threads == cpu_smt_max_threads;
2922}
2923
2924static ssize_t
2925__store_smt_control(struct device *dev, struct device_attribute *attr,
2926 const char *buf, size_t count)
2927{
2928 int ctrlval, ret, num_threads, orig_threads;
2929 bool force_off;
2930
2931 if (cpu_smt_control == CPU_SMT_FORCE_DISABLED)
2932 return -EPERM;
2933
2934 if (cpu_smt_control == CPU_SMT_NOT_SUPPORTED)
2935 return -ENODEV;
2936
2937 if (sysfs_streq(buf, "on")) {
2938 ctrlval = CPU_SMT_ENABLED;
2939 num_threads = cpu_smt_max_threads;
2940 } else if (sysfs_streq(buf, "off")) {
2941 ctrlval = CPU_SMT_DISABLED;
2942 num_threads = 1;
2943 } else if (sysfs_streq(buf, "forceoff")) {
2944 ctrlval = CPU_SMT_FORCE_DISABLED;
2945 num_threads = 1;
2946 } else if (kstrtoint(buf, 10, &num_threads) == 0) {
2947 if (num_threads == 1)
2948 ctrlval = CPU_SMT_DISABLED;
2949 else if (cpu_smt_num_threads_valid(num_threads))
2950 ctrlval = CPU_SMT_ENABLED;
2951 else
2952 return -EINVAL;
2953 } else {
2954 return -EINVAL;
2955 }
2956
2957 ret = lock_device_hotplug_sysfs();
2958 if (ret)
2959 return ret;
2960
2961 orig_threads = cpu_smt_num_threads;
2962 cpu_smt_num_threads = num_threads;
2963
2964 force_off = ctrlval != cpu_smt_control && ctrlval == CPU_SMT_FORCE_DISABLED;
2965
2966 if (num_threads > orig_threads)
2967 ret = cpuhp_smt_enable();
2968 else if (num_threads < orig_threads || force_off)
2969 ret = cpuhp_smt_disable(ctrlval);
2970
2971 unlock_device_hotplug();
2972 return ret ? ret : count;
2973}
2974
2975#else /* !CONFIG_HOTPLUG_SMT */
2976static ssize_t
2977__store_smt_control(struct device *dev, struct device_attribute *attr,
2978 const char *buf, size_t count)
2979{
2980 return -ENODEV;
2981}
2982#endif /* CONFIG_HOTPLUG_SMT */
2983
2984static const char *smt_states[] = {
2985 [CPU_SMT_ENABLED] = "on",
2986 [CPU_SMT_DISABLED] = "off",
2987 [CPU_SMT_FORCE_DISABLED] = "forceoff",
2988 [CPU_SMT_NOT_SUPPORTED] = "notsupported",
2989 [CPU_SMT_NOT_IMPLEMENTED] = "notimplemented",
2990};
2991
2992static ssize_t control_show(struct device *dev,
2993 struct device_attribute *attr, char *buf)
2994{
2995 const char *state = smt_states[cpu_smt_control];
2996
2997#ifdef CONFIG_HOTPLUG_SMT
2998 /*
2999 * If SMT is enabled but not all threads are enabled then show the
3000 * number of threads. If all threads are enabled show "on". Otherwise
3001 * show the state name.
3002 */
3003 if (cpu_smt_control == CPU_SMT_ENABLED &&
3004 cpu_smt_num_threads != cpu_smt_max_threads)
3005 return sysfs_emit(buf, "%d\n", cpu_smt_num_threads);
3006#endif
3007
3008 return sysfs_emit(buf, "%s\n", state);
3009}
3010
3011static ssize_t control_store(struct device *dev, struct device_attribute *attr,
3012 const char *buf, size_t count)
3013{
3014 return __store_smt_control(dev, attr, buf, count);
3015}
3016static DEVICE_ATTR_RW(control);
3017
3018static ssize_t active_show(struct device *dev,
3019 struct device_attribute *attr, char *buf)
3020{
3021 return sysfs_emit(buf, "%d\n", sched_smt_active());
3022}
3023static DEVICE_ATTR_RO(active);
3024
3025static struct attribute *cpuhp_smt_attrs[] = {
3026 &dev_attr_control.attr,
3027 &dev_attr_active.attr,
3028 NULL
3029};
3030
3031static const struct attribute_group cpuhp_smt_attr_group = {
3032 .attrs = cpuhp_smt_attrs,
3033 .name = "smt",
3034 NULL
3035};
3036
3037static int __init cpu_smt_sysfs_init(void)
3038{
3039 struct device *dev_root;
3040 int ret = -ENODEV;
3041
3042 dev_root = bus_get_dev_root(&cpu_subsys);
3043 if (dev_root) {
3044 ret = sysfs_create_group(&dev_root->kobj, &cpuhp_smt_attr_group);
3045 put_device(dev_root);
3046 }
3047 return ret;
3048}
3049
3050static int __init cpuhp_sysfs_init(void)
3051{
3052 struct device *dev_root;
3053 int cpu, ret;
3054
3055 ret = cpu_smt_sysfs_init();
3056 if (ret)
3057 return ret;
3058
3059 dev_root = bus_get_dev_root(&cpu_subsys);
3060 if (dev_root) {
3061 ret = sysfs_create_group(&dev_root->kobj, &cpuhp_cpu_root_attr_group);
3062 put_device(dev_root);
3063 if (ret)
3064 return ret;
3065 }
3066
3067 for_each_possible_cpu(cpu) {
3068 struct device *dev = get_cpu_device(cpu);
3069
3070 if (!dev)
3071 continue;
3072 ret = sysfs_create_group(&dev->kobj, &cpuhp_cpu_attr_group);
3073 if (ret)
3074 return ret;
3075 }
3076 return 0;
3077}
3078device_initcall(cpuhp_sysfs_init);
3079#endif /* CONFIG_SYSFS && CONFIG_HOTPLUG_CPU */
3080
3081/*
3082 * cpu_bit_bitmap[] is a special, "compressed" data structure that
3083 * represents all NR_CPUS bits binary values of 1<<nr.
3084 *
3085 * It is used by cpumask_of() to get a constant address to a CPU
3086 * mask value that has a single bit set only.
3087 */
3088
3089/* cpu_bit_bitmap[0] is empty - so we can back into it */
3090#define MASK_DECLARE_1(x) [x+1][0] = (1UL << (x))
3091#define MASK_DECLARE_2(x) MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
3092#define MASK_DECLARE_4(x) MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
3093#define MASK_DECLARE_8(x) MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
3094
3095const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
3096
3097 MASK_DECLARE_8(0), MASK_DECLARE_8(8),
3098 MASK_DECLARE_8(16), MASK_DECLARE_8(24),
3099#if BITS_PER_LONG > 32
3100 MASK_DECLARE_8(32), MASK_DECLARE_8(40),
3101 MASK_DECLARE_8(48), MASK_DECLARE_8(56),
3102#endif
3103};
3104EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
3105
3106const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
3107EXPORT_SYMBOL(cpu_all_bits);
3108
3109#ifdef CONFIG_INIT_ALL_POSSIBLE
3110struct cpumask __cpu_possible_mask __ro_after_init
3111 = {CPU_BITS_ALL};
3112#else
3113struct cpumask __cpu_possible_mask __ro_after_init;
3114#endif
3115EXPORT_SYMBOL(__cpu_possible_mask);
3116
3117struct cpumask __cpu_online_mask __read_mostly;
3118EXPORT_SYMBOL(__cpu_online_mask);
3119
3120struct cpumask __cpu_present_mask __read_mostly;
3121EXPORT_SYMBOL(__cpu_present_mask);
3122
3123struct cpumask __cpu_active_mask __read_mostly;
3124EXPORT_SYMBOL(__cpu_active_mask);
3125
3126struct cpumask __cpu_dying_mask __read_mostly;
3127EXPORT_SYMBOL(__cpu_dying_mask);
3128
3129atomic_t __num_online_cpus __read_mostly;
3130EXPORT_SYMBOL(__num_online_cpus);
3131
3132void init_cpu_present(const struct cpumask *src)
3133{
3134 cpumask_copy(&__cpu_present_mask, src);
3135}
3136
3137void init_cpu_possible(const struct cpumask *src)
3138{
3139 cpumask_copy(&__cpu_possible_mask, src);
3140}
3141
3142void init_cpu_online(const struct cpumask *src)
3143{
3144 cpumask_copy(&__cpu_online_mask, src);
3145}
3146
3147void set_cpu_online(unsigned int cpu, bool online)
3148{
3149 /*
3150 * atomic_inc/dec() is required to handle the horrid abuse of this
3151 * function by the reboot and kexec code which invoke it from
3152 * IPI/NMI broadcasts when shutting down CPUs. Invocation from
3153 * regular CPU hotplug is properly serialized.
3154 *
3155 * Note, that the fact that __num_online_cpus is of type atomic_t
3156 * does not protect readers which are not serialized against
3157 * concurrent hotplug operations.
3158 */
3159 if (online) {
3160 if (!cpumask_test_and_set_cpu(cpu, &__cpu_online_mask))
3161 atomic_inc(&__num_online_cpus);
3162 } else {
3163 if (cpumask_test_and_clear_cpu(cpu, &__cpu_online_mask))
3164 atomic_dec(&__num_online_cpus);
3165 }
3166}
3167
3168/*
3169 * Activate the first processor.
3170 */
3171void __init boot_cpu_init(void)
3172{
3173 int cpu = smp_processor_id();
3174
3175 /* Mark the boot cpu "present", "online" etc for SMP and UP case */
3176 set_cpu_online(cpu, true);
3177 set_cpu_active(cpu, true);
3178 set_cpu_present(cpu, true);
3179 set_cpu_possible(cpu, true);
3180
3181#ifdef CONFIG_SMP
3182 __boot_cpu_id = cpu;
3183#endif
3184}
3185
3186/*
3187 * Must be called _AFTER_ setting up the per_cpu areas
3188 */
3189void __init boot_cpu_hotplug_init(void)
3190{
3191#ifdef CONFIG_SMP
3192 cpumask_set_cpu(smp_processor_id(), &cpus_booted_once_mask);
3193 atomic_set(this_cpu_ptr(&cpuhp_state.ap_sync_state), SYNC_STATE_ONLINE);
3194#endif
3195 this_cpu_write(cpuhp_state.state, CPUHP_ONLINE);
3196 this_cpu_write(cpuhp_state.target, CPUHP_ONLINE);
3197}
3198
3199#ifdef CONFIG_CPU_MITIGATIONS
3200/*
3201 * These are used for a global "mitigations=" cmdline option for toggling
3202 * optional CPU mitigations.
3203 */
3204enum cpu_mitigations {
3205 CPU_MITIGATIONS_OFF,
3206 CPU_MITIGATIONS_AUTO,
3207 CPU_MITIGATIONS_AUTO_NOSMT,
3208};
3209
3210static enum cpu_mitigations cpu_mitigations __ro_after_init = CPU_MITIGATIONS_AUTO;
3211
3212static int __init mitigations_parse_cmdline(char *arg)
3213{
3214 if (!strcmp(arg, "off"))
3215 cpu_mitigations = CPU_MITIGATIONS_OFF;
3216 else if (!strcmp(arg, "auto"))
3217 cpu_mitigations = CPU_MITIGATIONS_AUTO;
3218 else if (!strcmp(arg, "auto,nosmt"))
3219 cpu_mitigations = CPU_MITIGATIONS_AUTO_NOSMT;
3220 else
3221 pr_crit("Unsupported mitigations=%s, system may still be vulnerable\n",
3222 arg);
3223
3224 return 0;
3225}
3226
3227/* mitigations=off */
3228bool cpu_mitigations_off(void)
3229{
3230 return cpu_mitigations == CPU_MITIGATIONS_OFF;
3231}
3232EXPORT_SYMBOL_GPL(cpu_mitigations_off);
3233
3234/* mitigations=auto,nosmt */
3235bool cpu_mitigations_auto_nosmt(void)
3236{
3237 return cpu_mitigations == CPU_MITIGATIONS_AUTO_NOSMT;
3238}
3239EXPORT_SYMBOL_GPL(cpu_mitigations_auto_nosmt);
3240#else
3241static int __init mitigations_parse_cmdline(char *arg)
3242{
3243 pr_crit("Kernel compiled without mitigations, ignoring 'mitigations'; system may still be vulnerable\n");
3244 return 0;
3245}
3246#endif
3247early_param("mitigations", mitigations_parse_cmdline);