projects/linux·blob v5.9-rc2 · refs

2554 lines · 60.8 KiB

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/percpu-rwsem.h>
35
36#include <trace/events/power.h>
37#define CREATE_TRACE_POINTS
38#include <trace/events/cpuhp.h>
39
40#include "smpboot.h"
41
42/**
43 * cpuhp_cpu_state - Per cpu hotplug state storage
44 * @state: The current cpu state
45 * @target: The target state
46 * @thread: Pointer to the hotplug thread
47 * @should_run: Thread should execute
48 * @rollback: Perform a rollback
49 * @single: Single callback invocation
50 * @bringup: Single callback bringup or teardown selector
51 * @cb_state: The state for a single callback (install/uninstall)
52 * @result: Result of the operation
53 * @done_up: Signal completion to the issuer of the task for cpu-up
54 * @done_down: Signal completion to the issuer of the task for cpu-down
55 */
56struct cpuhp_cpu_state {
57 enum cpuhp_state state;
58 enum cpuhp_state target;
59 enum cpuhp_state fail;
60#ifdef CONFIG_SMP
61 struct task_struct *thread;
62 bool should_run;
63 bool rollback;
64 bool single;
65 bool bringup;
66 struct hlist_node *node;
67 struct hlist_node *last;
68 enum cpuhp_state cb_state;
69 int result;
70 struct completion done_up;
71 struct completion done_down;
72#endif
73};
74
75static DEFINE_PER_CPU(struct cpuhp_cpu_state, cpuhp_state) = {
76 .fail = CPUHP_INVALID,
77};
78
79#ifdef CONFIG_SMP
80cpumask_t cpus_booted_once_mask;
81#endif
82
83#if defined(CONFIG_LOCKDEP) && defined(CONFIG_SMP)
84static struct lockdep_map cpuhp_state_up_map =
85 STATIC_LOCKDEP_MAP_INIT("cpuhp_state-up", &cpuhp_state_up_map);
86static struct lockdep_map cpuhp_state_down_map =
87 STATIC_LOCKDEP_MAP_INIT("cpuhp_state-down", &cpuhp_state_down_map);
88
89
90static inline void cpuhp_lock_acquire(bool bringup)
91{
92 lock_map_acquire(bringup ? &cpuhp_state_up_map : &cpuhp_state_down_map);
93}
94
95static inline void cpuhp_lock_release(bool bringup)
96{
97 lock_map_release(bringup ? &cpuhp_state_up_map : &cpuhp_state_down_map);
98}
99#else
100
101static inline void cpuhp_lock_acquire(bool bringup) { }
102static inline void cpuhp_lock_release(bool bringup) { }
103
104#endif
105
106/**
107 * cpuhp_step - Hotplug state machine step
108 * @name: Name of the step
109 * @startup: Startup function of the step
110 * @teardown: Teardown function of the step
111 * @cant_stop: Bringup/teardown can't be stopped at this step
112 */
113struct cpuhp_step {
114 const char *name;
115 union {
116 int (*single)(unsigned int cpu);
117 int (*multi)(unsigned int cpu,
118 struct hlist_node *node);
119 } startup;
120 union {
121 int (*single)(unsigned int cpu);
122 int (*multi)(unsigned int cpu,
123 struct hlist_node *node);
124 } teardown;
125 struct hlist_head list;
126 bool cant_stop;
127 bool multi_instance;
128};
129
130static DEFINE_MUTEX(cpuhp_state_mutex);
131static struct cpuhp_step cpuhp_hp_states[];
132
133static struct cpuhp_step *cpuhp_get_step(enum cpuhp_state state)
134{
135 return cpuhp_hp_states + state;
136}
137
138/**
139 * cpuhp_invoke_callback _ Invoke the callbacks for a given state
140 * @cpu: The cpu for which the callback should be invoked
141 * @state: The state to do callbacks for
142 * @bringup: True if the bringup callback should be invoked
143 * @node: For multi-instance, do a single entry callback for install/remove
144 * @lastp: For multi-instance rollback, remember how far we got
145 *
146 * Called from cpu hotplug and from the state register machinery.
147 */
148static int cpuhp_invoke_callback(unsigned int cpu, enum cpuhp_state state,
149 bool bringup, struct hlist_node *node,
150 struct hlist_node **lastp)
151{
152 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
153 struct cpuhp_step *step = cpuhp_get_step(state);
154 int (*cbm)(unsigned int cpu, struct hlist_node *node);
155 int (*cb)(unsigned int cpu);
156 int ret, cnt;
157
158 if (st->fail == state) {
159 st->fail = CPUHP_INVALID;
160
161 if (!(bringup ? step->startup.single : step->teardown.single))
162 return 0;
163
164 return -EAGAIN;
165 }
166
167 if (!step->multi_instance) {
168 WARN_ON_ONCE(lastp && *lastp);
169 cb = bringup ? step->startup.single : step->teardown.single;
170 if (!cb)
171 return 0;
172 trace_cpuhp_enter(cpu, st->target, state, cb);
173 ret = cb(cpu);
174 trace_cpuhp_exit(cpu, st->state, state, ret);
175 return ret;
176 }
177 cbm = bringup ? step->startup.multi : step->teardown.multi;
178 if (!cbm)
179 return 0;
180
181 /* Single invocation for instance add/remove */
182 if (node) {
183 WARN_ON_ONCE(lastp && *lastp);
184 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
185 ret = cbm(cpu, node);
186 trace_cpuhp_exit(cpu, st->state, state, ret);
187 return ret;
188 }
189
190 /* State transition. Invoke on all instances */
191 cnt = 0;
192 hlist_for_each(node, &step->list) {
193 if (lastp && node == *lastp)
194 break;
195
196 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
197 ret = cbm(cpu, node);
198 trace_cpuhp_exit(cpu, st->state, state, ret);
199 if (ret) {
200 if (!lastp)
201 goto err;
202
203 *lastp = node;
204 return ret;
205 }
206 cnt++;
207 }
208 if (lastp)
209 *lastp = NULL;
210 return 0;
211err:
212 /* Rollback the instances if one failed */
213 cbm = !bringup ? step->startup.multi : step->teardown.multi;
214 if (!cbm)
215 return ret;
216
217 hlist_for_each(node, &step->list) {
218 if (!cnt--)
219 break;
220
221 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
222 ret = cbm(cpu, node);
223 trace_cpuhp_exit(cpu, st->state, state, ret);
224 /*
225 * Rollback must not fail,
226 */
227 WARN_ON_ONCE(ret);
228 }
229 return ret;
230}
231
232#ifdef CONFIG_SMP
233static bool cpuhp_is_ap_state(enum cpuhp_state state)
234{
235 /*
236 * The extra check for CPUHP_TEARDOWN_CPU is only for documentation
237 * purposes as that state is handled explicitly in cpu_down.
238 */
239 return state > CPUHP_BRINGUP_CPU && state != CPUHP_TEARDOWN_CPU;
240}
241
242static inline void wait_for_ap_thread(struct cpuhp_cpu_state *st, bool bringup)
243{
244 struct completion *done = bringup ? &st->done_up : &st->done_down;
245 wait_for_completion(done);
246}
247
248static inline void complete_ap_thread(struct cpuhp_cpu_state *st, bool bringup)
249{
250 struct completion *done = bringup ? &st->done_up : &st->done_down;
251 complete(done);
252}
253
254/*
255 * The former STARTING/DYING states, ran with IRQs disabled and must not fail.
256 */
257static bool cpuhp_is_atomic_state(enum cpuhp_state state)
258{
259 return CPUHP_AP_IDLE_DEAD <= state && state < CPUHP_AP_ONLINE;
260}
261
262/* Serializes the updates to cpu_online_mask, cpu_present_mask */
263static DEFINE_MUTEX(cpu_add_remove_lock);
264bool cpuhp_tasks_frozen;
265EXPORT_SYMBOL_GPL(cpuhp_tasks_frozen);
266
267/*
268 * The following two APIs (cpu_maps_update_begin/done) must be used when
269 * attempting to serialize the updates to cpu_online_mask & cpu_present_mask.
270 */
271void cpu_maps_update_begin(void)
272{
273 mutex_lock(&cpu_add_remove_lock);
274}
275
276void cpu_maps_update_done(void)
277{
278 mutex_unlock(&cpu_add_remove_lock);
279}
280
281/*
282 * If set, cpu_up and cpu_down will return -EBUSY and do nothing.
283 * Should always be manipulated under cpu_add_remove_lock
284 */
285static int cpu_hotplug_disabled;
286
287#ifdef CONFIG_HOTPLUG_CPU
288
289DEFINE_STATIC_PERCPU_RWSEM(cpu_hotplug_lock);
290
291void cpus_read_lock(void)
292{
293 percpu_down_read(&cpu_hotplug_lock);
294}
295EXPORT_SYMBOL_GPL(cpus_read_lock);
296
297int cpus_read_trylock(void)
298{
299 return percpu_down_read_trylock(&cpu_hotplug_lock);
300}
301EXPORT_SYMBOL_GPL(cpus_read_trylock);
302
303void cpus_read_unlock(void)
304{
305 percpu_up_read(&cpu_hotplug_lock);
306}
307EXPORT_SYMBOL_GPL(cpus_read_unlock);
308
309void cpus_write_lock(void)
310{
311 percpu_down_write(&cpu_hotplug_lock);
312}
313
314void cpus_write_unlock(void)
315{
316 percpu_up_write(&cpu_hotplug_lock);
317}
318
319void lockdep_assert_cpus_held(void)
320{
321 /*
322 * We can't have hotplug operations before userspace starts running,
323 * and some init codepaths will knowingly not take the hotplug lock.
324 * This is all valid, so mute lockdep until it makes sense to report
325 * unheld locks.
326 */
327 if (system_state < SYSTEM_RUNNING)
328 return;
329
330 percpu_rwsem_assert_held(&cpu_hotplug_lock);
331}
332
333static void lockdep_acquire_cpus_lock(void)
334{
335 rwsem_acquire(&cpu_hotplug_lock.dep_map, 0, 0, _THIS_IP_);
336}
337
338static void lockdep_release_cpus_lock(void)
339{
340 rwsem_release(&cpu_hotplug_lock.dep_map, _THIS_IP_);
341}
342
343/*
344 * Wait for currently running CPU hotplug operations to complete (if any) and
345 * disable future CPU hotplug (from sysfs). The 'cpu_add_remove_lock' protects
346 * the 'cpu_hotplug_disabled' flag. The same lock is also acquired by the
347 * hotplug path before performing hotplug operations. So acquiring that lock
348 * guarantees mutual exclusion from any currently running hotplug operations.
349 */
350void cpu_hotplug_disable(void)
351{
352 cpu_maps_update_begin();
353 cpu_hotplug_disabled++;
354 cpu_maps_update_done();
355}
356EXPORT_SYMBOL_GPL(cpu_hotplug_disable);
357
358static void __cpu_hotplug_enable(void)
359{
360 if (WARN_ONCE(!cpu_hotplug_disabled, "Unbalanced cpu hotplug enable\n"))
361 return;
362 cpu_hotplug_disabled--;
363}
364
365void cpu_hotplug_enable(void)
366{
367 cpu_maps_update_begin();
368 __cpu_hotplug_enable();
369 cpu_maps_update_done();
370}
371EXPORT_SYMBOL_GPL(cpu_hotplug_enable);
372
373#else
374
375static void lockdep_acquire_cpus_lock(void)
376{
377}
378
379static void lockdep_release_cpus_lock(void)
380{
381}
382
383#endif /* CONFIG_HOTPLUG_CPU */
384
385/*
386 * Architectures that need SMT-specific errata handling during SMT hotplug
387 * should override this.
388 */
389void __weak arch_smt_update(void) { }
390
391#ifdef CONFIG_HOTPLUG_SMT
392enum cpuhp_smt_control cpu_smt_control __read_mostly = CPU_SMT_ENABLED;
393
394void __init cpu_smt_disable(bool force)
395{
396 if (!cpu_smt_possible())
397 return;
398
399 if (force) {
400 pr_info("SMT: Force disabled\n");
401 cpu_smt_control = CPU_SMT_FORCE_DISABLED;
402 } else {
403 pr_info("SMT: disabled\n");
404 cpu_smt_control = CPU_SMT_DISABLED;
405 }
406}
407
408/*
409 * The decision whether SMT is supported can only be done after the full
410 * CPU identification. Called from architecture code.
411 */
412void __init cpu_smt_check_topology(void)
413{
414 if (!topology_smt_supported())
415 cpu_smt_control = CPU_SMT_NOT_SUPPORTED;
416}
417
418static int __init smt_cmdline_disable(char *str)
419{
420 cpu_smt_disable(str && !strcmp(str, "force"));
421 return 0;
422}
423early_param("nosmt", smt_cmdline_disable);
424
425static inline bool cpu_smt_allowed(unsigned int cpu)
426{
427 if (cpu_smt_control == CPU_SMT_ENABLED)
428 return true;
429
430 if (topology_is_primary_thread(cpu))
431 return true;
432
433 /*
434 * On x86 it's required to boot all logical CPUs at least once so
435 * that the init code can get a chance to set CR4.MCE on each
436 * CPU. Otherwise, a broadcasted MCE observing CR4.MCE=0b on any
437 * core will shutdown the machine.
438 */
439 return !cpumask_test_cpu(cpu, &cpus_booted_once_mask);
440}
441
442/* Returns true if SMT is not supported of forcefully (irreversibly) disabled */
443bool cpu_smt_possible(void)
444{
445 return cpu_smt_control != CPU_SMT_FORCE_DISABLED &&
446 cpu_smt_control != CPU_SMT_NOT_SUPPORTED;
447}
448EXPORT_SYMBOL_GPL(cpu_smt_possible);
449#else
450static inline bool cpu_smt_allowed(unsigned int cpu) { return true; }
451#endif
452
453static inline enum cpuhp_state
454cpuhp_set_state(struct cpuhp_cpu_state *st, enum cpuhp_state target)
455{
456 enum cpuhp_state prev_state = st->state;
457
458 st->rollback = false;
459 st->last = NULL;
460
461 st->target = target;
462 st->single = false;
463 st->bringup = st->state < target;
464
465 return prev_state;
466}
467
468static inline void
469cpuhp_reset_state(struct cpuhp_cpu_state *st, enum cpuhp_state prev_state)
470{
471 st->rollback = true;
472
473 /*
474 * If we have st->last we need to undo partial multi_instance of this
475 * state first. Otherwise start undo at the previous state.
476 */
477 if (!st->last) {
478 if (st->bringup)
479 st->state--;
480 else
481 st->state++;
482 }
483
484 st->target = prev_state;
485 st->bringup = !st->bringup;
486}
487
488/* Regular hotplug invocation of the AP hotplug thread */
489static void __cpuhp_kick_ap(struct cpuhp_cpu_state *st)
490{
491 if (!st->single && st->state == st->target)
492 return;
493
494 st->result = 0;
495 /*
496 * Make sure the above stores are visible before should_run becomes
497 * true. Paired with the mb() above in cpuhp_thread_fun()
498 */
499 smp_mb();
500 st->should_run = true;
501 wake_up_process(st->thread);
502 wait_for_ap_thread(st, st->bringup);
503}
504
505static int cpuhp_kick_ap(struct cpuhp_cpu_state *st, enum cpuhp_state target)
506{
507 enum cpuhp_state prev_state;
508 int ret;
509
510 prev_state = cpuhp_set_state(st, target);
511 __cpuhp_kick_ap(st);
512 if ((ret = st->result)) {
513 cpuhp_reset_state(st, prev_state);
514 __cpuhp_kick_ap(st);
515 }
516
517 return ret;
518}
519
520static int bringup_wait_for_ap(unsigned int cpu)
521{
522 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
523
524 /* Wait for the CPU to reach CPUHP_AP_ONLINE_IDLE */
525 wait_for_ap_thread(st, true);
526 if (WARN_ON_ONCE((!cpu_online(cpu))))
527 return -ECANCELED;
528
529 /* Unpark the hotplug thread of the target cpu */
530 kthread_unpark(st->thread);
531
532 /*
533 * SMT soft disabling on X86 requires to bring the CPU out of the
534 * BIOS 'wait for SIPI' state in order to set the CR4.MCE bit. The
535 * CPU marked itself as booted_once in notify_cpu_starting() so the
536 * cpu_smt_allowed() check will now return false if this is not the
537 * primary sibling.
538 */
539 if (!cpu_smt_allowed(cpu))
540 return -ECANCELED;
541
542 if (st->target <= CPUHP_AP_ONLINE_IDLE)
543 return 0;
544
545 return cpuhp_kick_ap(st, st->target);
546}
547
548static int bringup_cpu(unsigned int cpu)
549{
550 struct task_struct *idle = idle_thread_get(cpu);
551 int ret;
552
553 /*
554 * Some architectures have to walk the irq descriptors to
555 * setup the vector space for the cpu which comes online.
556 * Prevent irq alloc/free across the bringup.
557 */
558 irq_lock_sparse();
559
560 /* Arch-specific enabling code. */
561 ret = __cpu_up(cpu, idle);
562 irq_unlock_sparse();
563 if (ret)
564 return ret;
565 return bringup_wait_for_ap(cpu);
566}
567
568static int finish_cpu(unsigned int cpu)
569{
570 struct task_struct *idle = idle_thread_get(cpu);
571 struct mm_struct *mm = idle->active_mm;
572
573 /*
574 * idle_task_exit() will have switched to &init_mm, now
575 * clean up any remaining active_mm state.
576 */
577 if (mm != &init_mm)
578 idle->active_mm = &init_mm;
579 mmdrop(mm);
580 return 0;
581}
582
583/*
584 * Hotplug state machine related functions
585 */
586
587static void undo_cpu_up(unsigned int cpu, struct cpuhp_cpu_state *st)
588{
589 for (st->state--; st->state > st->target; st->state--)
590 cpuhp_invoke_callback(cpu, st->state, false, NULL, NULL);
591}
592
593static inline bool can_rollback_cpu(struct cpuhp_cpu_state *st)
594{
595 if (IS_ENABLED(CONFIG_HOTPLUG_CPU))
596 return true;
597 /*
598 * When CPU hotplug is disabled, then taking the CPU down is not
599 * possible because takedown_cpu() and the architecture and
600 * subsystem specific mechanisms are not available. So the CPU
601 * which would be completely unplugged again needs to stay around
602 * in the current state.
603 */
604 return st->state <= CPUHP_BRINGUP_CPU;
605}
606
607static int cpuhp_up_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
608 enum cpuhp_state target)
609{
610 enum cpuhp_state prev_state = st->state;
611 int ret = 0;
612
613 while (st->state < target) {
614 st->state++;
615 ret = cpuhp_invoke_callback(cpu, st->state, true, NULL, NULL);
616 if (ret) {
617 if (can_rollback_cpu(st)) {
618 st->target = prev_state;
619 undo_cpu_up(cpu, st);
620 }
621 break;
622 }
623 }
624 return ret;
625}
626
627/*
628 * The cpu hotplug threads manage the bringup and teardown of the cpus
629 */
630static void cpuhp_create(unsigned int cpu)
631{
632 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
633
634 init_completion(&st->done_up);
635 init_completion(&st->done_down);
636}
637
638static int cpuhp_should_run(unsigned int cpu)
639{
640 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
641
642 return st->should_run;
643}
644
645/*
646 * Execute teardown/startup callbacks on the plugged cpu. Also used to invoke
647 * callbacks when a state gets [un]installed at runtime.
648 *
649 * Each invocation of this function by the smpboot thread does a single AP
650 * state callback.
651 *
652 * It has 3 modes of operation:
653 * - single: runs st->cb_state
654 * - up: runs ++st->state, while st->state < st->target
655 * - down: runs st->state--, while st->state > st->target
656 *
657 * When complete or on error, should_run is cleared and the completion is fired.
658 */
659static void cpuhp_thread_fun(unsigned int cpu)
660{
661 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
662 bool bringup = st->bringup;
663 enum cpuhp_state state;
664
665 if (WARN_ON_ONCE(!st->should_run))
666 return;
667
668 /*
669 * ACQUIRE for the cpuhp_should_run() load of ->should_run. Ensures
670 * that if we see ->should_run we also see the rest of the state.
671 */
672 smp_mb();
673
674 /*
675 * The BP holds the hotplug lock, but we're now running on the AP,
676 * ensure that anybody asserting the lock is held, will actually find
677 * it so.
678 */
679 lockdep_acquire_cpus_lock();
680 cpuhp_lock_acquire(bringup);
681
682 if (st->single) {
683 state = st->cb_state;
684 st->should_run = false;
685 } else {
686 if (bringup) {
687 st->state++;
688 state = st->state;
689 st->should_run = (st->state < st->target);
690 WARN_ON_ONCE(st->state > st->target);
691 } else {
692 state = st->state;
693 st->state--;
694 st->should_run = (st->state > st->target);
695 WARN_ON_ONCE(st->state < st->target);
696 }
697 }
698
699 WARN_ON_ONCE(!cpuhp_is_ap_state(state));
700
701 if (cpuhp_is_atomic_state(state)) {
702 local_irq_disable();
703 st->result = cpuhp_invoke_callback(cpu, state, bringup, st->node, &st->last);
704 local_irq_enable();
705
706 /*
707 * STARTING/DYING must not fail!
708 */
709 WARN_ON_ONCE(st->result);
710 } else {
711 st->result = cpuhp_invoke_callback(cpu, state, bringup, st->node, &st->last);
712 }
713
714 if (st->result) {
715 /*
716 * If we fail on a rollback, we're up a creek without no
717 * paddle, no way forward, no way back. We loose, thanks for
718 * playing.
719 */
720 WARN_ON_ONCE(st->rollback);
721 st->should_run = false;
722 }
723
724 cpuhp_lock_release(bringup);
725 lockdep_release_cpus_lock();
726
727 if (!st->should_run)
728 complete_ap_thread(st, bringup);
729}
730
731/* Invoke a single callback on a remote cpu */
732static int
733cpuhp_invoke_ap_callback(int cpu, enum cpuhp_state state, bool bringup,
734 struct hlist_node *node)
735{
736 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
737 int ret;
738
739 if (!cpu_online(cpu))
740 return 0;
741
742 cpuhp_lock_acquire(false);
743 cpuhp_lock_release(false);
744
745 cpuhp_lock_acquire(true);
746 cpuhp_lock_release(true);
747
748 /*
749 * If we are up and running, use the hotplug thread. For early calls
750 * we invoke the thread function directly.
751 */
752 if (!st->thread)
753 return cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
754
755 st->rollback = false;
756 st->last = NULL;
757
758 st->node = node;
759 st->bringup = bringup;
760 st->cb_state = state;
761 st->single = true;
762
763 __cpuhp_kick_ap(st);
764
765 /*
766 * If we failed and did a partial, do a rollback.
767 */
768 if ((ret = st->result) && st->last) {
769 st->rollback = true;
770 st->bringup = !bringup;
771
772 __cpuhp_kick_ap(st);
773 }
774
775 /*
776 * Clean up the leftovers so the next hotplug operation wont use stale
777 * data.
778 */
779 st->node = st->last = NULL;
780 return ret;
781}
782
783static int cpuhp_kick_ap_work(unsigned int cpu)
784{
785 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
786 enum cpuhp_state prev_state = st->state;
787 int ret;
788
789 cpuhp_lock_acquire(false);
790 cpuhp_lock_release(false);
791
792 cpuhp_lock_acquire(true);
793 cpuhp_lock_release(true);
794
795 trace_cpuhp_enter(cpu, st->target, prev_state, cpuhp_kick_ap_work);
796 ret = cpuhp_kick_ap(st, st->target);
797 trace_cpuhp_exit(cpu, st->state, prev_state, ret);
798
799 return ret;
800}
801
802static struct smp_hotplug_thread cpuhp_threads = {
803 .store = &cpuhp_state.thread,
804 .create = &cpuhp_create,
805 .thread_should_run = cpuhp_should_run,
806 .thread_fn = cpuhp_thread_fun,
807 .thread_comm = "cpuhp/%u",
808 .selfparking = true,
809};
810
811void __init cpuhp_threads_init(void)
812{
813 BUG_ON(smpboot_register_percpu_thread(&cpuhp_threads));
814 kthread_unpark(this_cpu_read(cpuhp_state.thread));
815}
816
817#ifdef CONFIG_HOTPLUG_CPU
818/**
819 * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
820 * @cpu: a CPU id
821 *
822 * This function walks all processes, finds a valid mm struct for each one and
823 * then clears a corresponding bit in mm's cpumask. While this all sounds
824 * trivial, there are various non-obvious corner cases, which this function
825 * tries to solve in a safe manner.
826 *
827 * Also note that the function uses a somewhat relaxed locking scheme, so it may
828 * be called only for an already offlined CPU.
829 */
830void clear_tasks_mm_cpumask(int cpu)
831{
832 struct task_struct *p;
833
834 /*
835 * This function is called after the cpu is taken down and marked
836 * offline, so its not like new tasks will ever get this cpu set in
837 * their mm mask. -- Peter Zijlstra
838 * Thus, we may use rcu_read_lock() here, instead of grabbing
839 * full-fledged tasklist_lock.
840 */
841 WARN_ON(cpu_online(cpu));
842 rcu_read_lock();
843 for_each_process(p) {
844 struct task_struct *t;
845
846 /*
847 * Main thread might exit, but other threads may still have
848 * a valid mm. Find one.
849 */
850 t = find_lock_task_mm(p);
851 if (!t)
852 continue;
853 cpumask_clear_cpu(cpu, mm_cpumask(t->mm));
854 task_unlock(t);
855 }
856 rcu_read_unlock();
857}
858
859/* Take this CPU down. */
860static int take_cpu_down(void *_param)
861{
862 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
863 enum cpuhp_state target = max((int)st->target, CPUHP_AP_OFFLINE);
864 int err, cpu = smp_processor_id();
865 int ret;
866
867 /* Ensure this CPU doesn't handle any more interrupts. */
868 err = __cpu_disable();
869 if (err < 0)
870 return err;
871
872 /*
873 * We get here while we are in CPUHP_TEARDOWN_CPU state and we must not
874 * do this step again.
875 */
876 WARN_ON(st->state != CPUHP_TEARDOWN_CPU);
877 st->state--;
878 /* Invoke the former CPU_DYING callbacks */
879 for (; st->state > target; st->state--) {
880 ret = cpuhp_invoke_callback(cpu, st->state, false, NULL, NULL);
881 /*
882 * DYING must not fail!
883 */
884 WARN_ON_ONCE(ret);
885 }
886
887 /* Give up timekeeping duties */
888 tick_handover_do_timer();
889 /* Remove CPU from timer broadcasting */
890 tick_offline_cpu(cpu);
891 /* Park the stopper thread */
892 stop_machine_park(cpu);
893 return 0;
894}
895
896static int takedown_cpu(unsigned int cpu)
897{
898 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
899 int err;
900
901 /* Park the smpboot threads */
902 kthread_park(per_cpu_ptr(&cpuhp_state, cpu)->thread);
903
904 /*
905 * Prevent irq alloc/free while the dying cpu reorganizes the
906 * interrupt affinities.
907 */
908 irq_lock_sparse();
909
910 /*
911 * So now all preempt/rcu users must observe !cpu_active().
912 */
913 err = stop_machine_cpuslocked(take_cpu_down, NULL, cpumask_of(cpu));
914 if (err) {
915 /* CPU refused to die */
916 irq_unlock_sparse();
917 /* Unpark the hotplug thread so we can rollback there */
918 kthread_unpark(per_cpu_ptr(&cpuhp_state, cpu)->thread);
919 return err;
920 }
921 BUG_ON(cpu_online(cpu));
922
923 /*
924 * The teardown callback for CPUHP_AP_SCHED_STARTING will have removed
925 * all runnable tasks from the CPU, there's only the idle task left now
926 * that the migration thread is done doing the stop_machine thing.
927 *
928 * Wait for the stop thread to go away.
929 */
930 wait_for_ap_thread(st, false);
931 BUG_ON(st->state != CPUHP_AP_IDLE_DEAD);
932
933 /* Interrupts are moved away from the dying cpu, reenable alloc/free */
934 irq_unlock_sparse();
935
936 hotplug_cpu__broadcast_tick_pull(cpu);
937 /* This actually kills the CPU. */
938 __cpu_die(cpu);
939
940 tick_cleanup_dead_cpu(cpu);
941 rcutree_migrate_callbacks(cpu);
942 return 0;
943}
944
945static void cpuhp_complete_idle_dead(void *arg)
946{
947 struct cpuhp_cpu_state *st = arg;
948
949 complete_ap_thread(st, false);
950}
951
952void cpuhp_report_idle_dead(void)
953{
954 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
955
956 BUG_ON(st->state != CPUHP_AP_OFFLINE);
957 rcu_report_dead(smp_processor_id());
958 st->state = CPUHP_AP_IDLE_DEAD;
959 /*
960 * We cannot call complete after rcu_report_dead() so we delegate it
961 * to an online cpu.
962 */
963 smp_call_function_single(cpumask_first(cpu_online_mask),
964 cpuhp_complete_idle_dead, st, 0);
965}
966
967static void undo_cpu_down(unsigned int cpu, struct cpuhp_cpu_state *st)
968{
969 for (st->state++; st->state < st->target; st->state++)
970 cpuhp_invoke_callback(cpu, st->state, true, NULL, NULL);
971}
972
973static int cpuhp_down_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
974 enum cpuhp_state target)
975{
976 enum cpuhp_state prev_state = st->state;
977 int ret = 0;
978
979 for (; st->state > target; st->state--) {
980 ret = cpuhp_invoke_callback(cpu, st->state, false, NULL, NULL);
981 if (ret) {
982 st->target = prev_state;
983 if (st->state < prev_state)
984 undo_cpu_down(cpu, st);
985 break;
986 }
987 }
988 return ret;
989}
990
991/* Requires cpu_add_remove_lock to be held */
992static int __ref _cpu_down(unsigned int cpu, int tasks_frozen,
993 enum cpuhp_state target)
994{
995 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
996 int prev_state, ret = 0;
997
998 if (num_online_cpus() == 1)
999 return -EBUSY;
1000
1001 if (!cpu_present(cpu))
1002 return -EINVAL;
1003
1004 cpus_write_lock();
1005
1006 cpuhp_tasks_frozen = tasks_frozen;
1007
1008 prev_state = cpuhp_set_state(st, target);
1009 /*
1010 * If the current CPU state is in the range of the AP hotplug thread,
1011 * then we need to kick the thread.
1012 */
1013 if (st->state > CPUHP_TEARDOWN_CPU) {
1014 st->target = max((int)target, CPUHP_TEARDOWN_CPU);
1015 ret = cpuhp_kick_ap_work(cpu);
1016 /*
1017 * The AP side has done the error rollback already. Just
1018 * return the error code..
1019 */
1020 if (ret)
1021 goto out;
1022
1023 /*
1024 * We might have stopped still in the range of the AP hotplug
1025 * thread. Nothing to do anymore.
1026 */
1027 if (st->state > CPUHP_TEARDOWN_CPU)
1028 goto out;
1029
1030 st->target = target;
1031 }
1032 /*
1033 * The AP brought itself down to CPUHP_TEARDOWN_CPU. So we need
1034 * to do the further cleanups.
1035 */
1036 ret = cpuhp_down_callbacks(cpu, st, target);
1037 if (ret && st->state == CPUHP_TEARDOWN_CPU && st->state < prev_state) {
1038 cpuhp_reset_state(st, prev_state);
1039 __cpuhp_kick_ap(st);
1040 }
1041
1042out:
1043 cpus_write_unlock();
1044 /*
1045 * Do post unplug cleanup. This is still protected against
1046 * concurrent CPU hotplug via cpu_add_remove_lock.
1047 */
1048 lockup_detector_cleanup();
1049 arch_smt_update();
1050 return ret;
1051}
1052
1053static int cpu_down_maps_locked(unsigned int cpu, enum cpuhp_state target)
1054{
1055 if (cpu_hotplug_disabled)
1056 return -EBUSY;
1057 return _cpu_down(cpu, 0, target);
1058}
1059
1060static int cpu_down(unsigned int cpu, enum cpuhp_state target)
1061{
1062 int err;
1063
1064 cpu_maps_update_begin();
1065 err = cpu_down_maps_locked(cpu, target);
1066 cpu_maps_update_done();
1067 return err;
1068}
1069
1070/**
1071 * cpu_device_down - Bring down a cpu device
1072 * @dev: Pointer to the cpu device to offline
1073 *
1074 * This function is meant to be used by device core cpu subsystem only.
1075 *
1076 * Other subsystems should use remove_cpu() instead.
1077 */
1078int cpu_device_down(struct device *dev)
1079{
1080 return cpu_down(dev->id, CPUHP_OFFLINE);
1081}
1082
1083int remove_cpu(unsigned int cpu)
1084{
1085 int ret;
1086
1087 lock_device_hotplug();
1088 ret = device_offline(get_cpu_device(cpu));
1089 unlock_device_hotplug();
1090
1091 return ret;
1092}
1093EXPORT_SYMBOL_GPL(remove_cpu);
1094
1095void smp_shutdown_nonboot_cpus(unsigned int primary_cpu)
1096{
1097 unsigned int cpu;
1098 int error;
1099
1100 cpu_maps_update_begin();
1101
1102 /*
1103 * Make certain the cpu I'm about to reboot on is online.
1104 *
1105 * This is inline to what migrate_to_reboot_cpu() already do.
1106 */
1107 if (!cpu_online(primary_cpu))
1108 primary_cpu = cpumask_first(cpu_online_mask);
1109
1110 for_each_online_cpu(cpu) {
1111 if (cpu == primary_cpu)
1112 continue;
1113
1114 error = cpu_down_maps_locked(cpu, CPUHP_OFFLINE);
1115 if (error) {
1116 pr_err("Failed to offline CPU%d - error=%d",
1117 cpu, error);
1118 break;
1119 }
1120 }
1121
1122 /*
1123 * Ensure all but the reboot CPU are offline.
1124 */
1125 BUG_ON(num_online_cpus() > 1);
1126
1127 /*
1128 * Make sure the CPUs won't be enabled by someone else after this
1129 * point. Kexec will reboot to a new kernel shortly resetting
1130 * everything along the way.
1131 */
1132 cpu_hotplug_disabled++;
1133
1134 cpu_maps_update_done();
1135}
1136
1137#else
1138#define takedown_cpu NULL
1139#endif /*CONFIG_HOTPLUG_CPU*/
1140
1141/**
1142 * notify_cpu_starting(cpu) - Invoke the callbacks on the starting CPU
1143 * @cpu: cpu that just started
1144 *
1145 * It must be called by the arch code on the new cpu, before the new cpu
1146 * enables interrupts and before the "boot" cpu returns from __cpu_up().
1147 */
1148void notify_cpu_starting(unsigned int cpu)
1149{
1150 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1151 enum cpuhp_state target = min((int)st->target, CPUHP_AP_ONLINE);
1152 int ret;
1153
1154 rcu_cpu_starting(cpu); /* Enables RCU usage on this CPU. */
1155 cpumask_set_cpu(cpu, &cpus_booted_once_mask);
1156 while (st->state < target) {
1157 st->state++;
1158 ret = cpuhp_invoke_callback(cpu, st->state, true, NULL, NULL);
1159 /*
1160 * STARTING must not fail!
1161 */
1162 WARN_ON_ONCE(ret);
1163 }
1164}
1165
1166/*
1167 * Called from the idle task. Wake up the controlling task which brings the
1168 * hotplug thread of the upcoming CPU up and then delegates the rest of the
1169 * online bringup to the hotplug thread.
1170 */
1171void cpuhp_online_idle(enum cpuhp_state state)
1172{
1173 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
1174
1175 /* Happens for the boot cpu */
1176 if (state != CPUHP_AP_ONLINE_IDLE)
1177 return;
1178
1179 /*
1180 * Unpart the stopper thread before we start the idle loop (and start
1181 * scheduling); this ensures the stopper task is always available.
1182 */
1183 stop_machine_unpark(smp_processor_id());
1184
1185 st->state = CPUHP_AP_ONLINE_IDLE;
1186 complete_ap_thread(st, true);
1187}
1188
1189/* Requires cpu_add_remove_lock to be held */
1190static int _cpu_up(unsigned int cpu, int tasks_frozen, enum cpuhp_state target)
1191{
1192 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1193 struct task_struct *idle;
1194 int ret = 0;
1195
1196 cpus_write_lock();
1197
1198 if (!cpu_present(cpu)) {
1199 ret = -EINVAL;
1200 goto out;
1201 }
1202
1203 /*
1204 * The caller of cpu_up() might have raced with another
1205 * caller. Nothing to do.
1206 */
1207 if (st->state >= target)
1208 goto out;
1209
1210 if (st->state == CPUHP_OFFLINE) {
1211 /* Let it fail before we try to bring the cpu up */
1212 idle = idle_thread_get(cpu);
1213 if (IS_ERR(idle)) {
1214 ret = PTR_ERR(idle);
1215 goto out;
1216 }
1217 }
1218
1219 cpuhp_tasks_frozen = tasks_frozen;
1220
1221 cpuhp_set_state(st, target);
1222 /*
1223 * If the current CPU state is in the range of the AP hotplug thread,
1224 * then we need to kick the thread once more.
1225 */
1226 if (st->state > CPUHP_BRINGUP_CPU) {
1227 ret = cpuhp_kick_ap_work(cpu);
1228 /*
1229 * The AP side has done the error rollback already. Just
1230 * return the error code..
1231 */
1232 if (ret)
1233 goto out;
1234 }
1235
1236 /*
1237 * Try to reach the target state. We max out on the BP at
1238 * CPUHP_BRINGUP_CPU. After that the AP hotplug thread is
1239 * responsible for bringing it up to the target state.
1240 */
1241 target = min((int)target, CPUHP_BRINGUP_CPU);
1242 ret = cpuhp_up_callbacks(cpu, st, target);
1243out:
1244 cpus_write_unlock();
1245 arch_smt_update();
1246 return ret;
1247}
1248
1249static int cpu_up(unsigned int cpu, enum cpuhp_state target)
1250{
1251 int err = 0;
1252
1253 if (!cpu_possible(cpu)) {
1254 pr_err("can't online cpu %d because it is not configured as may-hotadd at boot time\n",
1255 cpu);
1256#if defined(CONFIG_IA64)
1257 pr_err("please check additional_cpus= boot parameter\n");
1258#endif
1259 return -EINVAL;
1260 }
1261
1262 err = try_online_node(cpu_to_node(cpu));
1263 if (err)
1264 return err;
1265
1266 cpu_maps_update_begin();
1267
1268 if (cpu_hotplug_disabled) {
1269 err = -EBUSY;
1270 goto out;
1271 }
1272 if (!cpu_smt_allowed(cpu)) {
1273 err = -EPERM;
1274 goto out;
1275 }
1276
1277 err = _cpu_up(cpu, 0, target);
1278out:
1279 cpu_maps_update_done();
1280 return err;
1281}
1282
1283/**
1284 * cpu_device_up - Bring up a cpu device
1285 * @dev: Pointer to the cpu device to online
1286 *
1287 * This function is meant to be used by device core cpu subsystem only.
1288 *
1289 * Other subsystems should use add_cpu() instead.
1290 */
1291int cpu_device_up(struct device *dev)
1292{
1293 return cpu_up(dev->id, CPUHP_ONLINE);
1294}
1295
1296int add_cpu(unsigned int cpu)
1297{
1298 int ret;
1299
1300 lock_device_hotplug();
1301 ret = device_online(get_cpu_device(cpu));
1302 unlock_device_hotplug();
1303
1304 return ret;
1305}
1306EXPORT_SYMBOL_GPL(add_cpu);
1307
1308/**
1309 * bringup_hibernate_cpu - Bring up the CPU that we hibernated on
1310 * @sleep_cpu: The cpu we hibernated on and should be brought up.
1311 *
1312 * On some architectures like arm64, we can hibernate on any CPU, but on
1313 * wake up the CPU we hibernated on might be offline as a side effect of
1314 * using maxcpus= for example.
1315 */
1316int bringup_hibernate_cpu(unsigned int sleep_cpu)
1317{
1318 int ret;
1319
1320 if (!cpu_online(sleep_cpu)) {
1321 pr_info("Hibernated on a CPU that is offline! Bringing CPU up.\n");
1322 ret = cpu_up(sleep_cpu, CPUHP_ONLINE);
1323 if (ret) {
1324 pr_err("Failed to bring hibernate-CPU up!\n");
1325 return ret;
1326 }
1327 }
1328 return 0;
1329}
1330
1331void bringup_nonboot_cpus(unsigned int setup_max_cpus)
1332{
1333 unsigned int cpu;
1334
1335 for_each_present_cpu(cpu) {
1336 if (num_online_cpus() >= setup_max_cpus)
1337 break;
1338 if (!cpu_online(cpu))
1339 cpu_up(cpu, CPUHP_ONLINE);
1340 }
1341}
1342
1343#ifdef CONFIG_PM_SLEEP_SMP
1344static cpumask_var_t frozen_cpus;
1345
1346int freeze_secondary_cpus(int primary)
1347{
1348 int cpu, error = 0;
1349
1350 cpu_maps_update_begin();
1351 if (primary == -1) {
1352 primary = cpumask_first(cpu_online_mask);
1353 if (!housekeeping_cpu(primary, HK_FLAG_TIMER))
1354 primary = housekeeping_any_cpu(HK_FLAG_TIMER);
1355 } else {
1356 if (!cpu_online(primary))
1357 primary = cpumask_first(cpu_online_mask);
1358 }
1359
1360 /*
1361 * We take down all of the non-boot CPUs in one shot to avoid races
1362 * with the userspace trying to use the CPU hotplug at the same time
1363 */
1364 cpumask_clear(frozen_cpus);
1365
1366 pr_info("Disabling non-boot CPUs ...\n");
1367 for_each_online_cpu(cpu) {
1368 if (cpu == primary)
1369 continue;
1370
1371 if (pm_wakeup_pending()) {
1372 pr_info("Wakeup pending. Abort CPU freeze\n");
1373 error = -EBUSY;
1374 break;
1375 }
1376
1377 trace_suspend_resume(TPS("CPU_OFF"), cpu, true);
1378 error = _cpu_down(cpu, 1, CPUHP_OFFLINE);
1379 trace_suspend_resume(TPS("CPU_OFF"), cpu, false);
1380 if (!error)
1381 cpumask_set_cpu(cpu, frozen_cpus);
1382 else {
1383 pr_err("Error taking CPU%d down: %d\n", cpu, error);
1384 break;
1385 }
1386 }
1387
1388 if (!error)
1389 BUG_ON(num_online_cpus() > 1);
1390 else
1391 pr_err("Non-boot CPUs are not disabled\n");
1392
1393 /*
1394 * Make sure the CPUs won't be enabled by someone else. We need to do
1395 * this even in case of failure as all freeze_secondary_cpus() users are
1396 * supposed to do thaw_secondary_cpus() on the failure path.
1397 */
1398 cpu_hotplug_disabled++;
1399
1400 cpu_maps_update_done();
1401 return error;
1402}
1403
1404void __weak arch_thaw_secondary_cpus_begin(void)
1405{
1406}
1407
1408void __weak arch_thaw_secondary_cpus_end(void)
1409{
1410}
1411
1412void thaw_secondary_cpus(void)
1413{
1414 int cpu, error;
1415
1416 /* Allow everyone to use the CPU hotplug again */
1417 cpu_maps_update_begin();
1418 __cpu_hotplug_enable();
1419 if (cpumask_empty(frozen_cpus))
1420 goto out;
1421
1422 pr_info("Enabling non-boot CPUs ...\n");
1423
1424 arch_thaw_secondary_cpus_begin();
1425
1426 for_each_cpu(cpu, frozen_cpus) {
1427 trace_suspend_resume(TPS("CPU_ON"), cpu, true);
1428 error = _cpu_up(cpu, 1, CPUHP_ONLINE);
1429 trace_suspend_resume(TPS("CPU_ON"), cpu, false);
1430 if (!error) {
1431 pr_info("CPU%d is up\n", cpu);
1432 continue;
1433 }
1434 pr_warn("Error taking CPU%d up: %d\n", cpu, error);
1435 }
1436
1437 arch_thaw_secondary_cpus_end();
1438
1439 cpumask_clear(frozen_cpus);
1440out:
1441 cpu_maps_update_done();
1442}
1443
1444static int __init alloc_frozen_cpus(void)
1445{
1446 if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
1447 return -ENOMEM;
1448 return 0;
1449}
1450core_initcall(alloc_frozen_cpus);
1451
1452/*
1453 * When callbacks for CPU hotplug notifications are being executed, we must
1454 * ensure that the state of the system with respect to the tasks being frozen
1455 * or not, as reported by the notification, remains unchanged *throughout the
1456 * duration* of the execution of the callbacks.
1457 * Hence we need to prevent the freezer from racing with regular CPU hotplug.
1458 *
1459 * This synchronization is implemented by mutually excluding regular CPU
1460 * hotplug and Suspend/Hibernate call paths by hooking onto the Suspend/
1461 * Hibernate notifications.
1462 */
1463static int
1464cpu_hotplug_pm_callback(struct notifier_block *nb,
1465 unsigned long action, void *ptr)
1466{
1467 switch (action) {
1468
1469 case PM_SUSPEND_PREPARE:
1470 case PM_HIBERNATION_PREPARE:
1471 cpu_hotplug_disable();
1472 break;
1473
1474 case PM_POST_SUSPEND:
1475 case PM_POST_HIBERNATION:
1476 cpu_hotplug_enable();
1477 break;
1478
1479 default:
1480 return NOTIFY_DONE;
1481 }
1482
1483 return NOTIFY_OK;
1484}
1485
1486
1487static int __init cpu_hotplug_pm_sync_init(void)
1488{
1489 /*
1490 * cpu_hotplug_pm_callback has higher priority than x86
1491 * bsp_pm_callback which depends on cpu_hotplug_pm_callback
1492 * to disable cpu hotplug to avoid cpu hotplug race.
1493 */
1494 pm_notifier(cpu_hotplug_pm_callback, 0);
1495 return 0;
1496}
1497core_initcall(cpu_hotplug_pm_sync_init);
1498
1499#endif /* CONFIG_PM_SLEEP_SMP */
1500
1501int __boot_cpu_id;
1502
1503#endif /* CONFIG_SMP */
1504
1505/* Boot processor state steps */
1506static struct cpuhp_step cpuhp_hp_states[] = {
1507 [CPUHP_OFFLINE] = {
1508 .name = "offline",
1509 .startup.single = NULL,
1510 .teardown.single = NULL,
1511 },
1512#ifdef CONFIG_SMP
1513 [CPUHP_CREATE_THREADS]= {
1514 .name = "threads:prepare",
1515 .startup.single = smpboot_create_threads,
1516 .teardown.single = NULL,
1517 .cant_stop = true,
1518 },
1519 [CPUHP_PERF_PREPARE] = {
1520 .name = "perf:prepare",
1521 .startup.single = perf_event_init_cpu,
1522 .teardown.single = perf_event_exit_cpu,
1523 },
1524 [CPUHP_WORKQUEUE_PREP] = {
1525 .name = "workqueue:prepare",
1526 .startup.single = workqueue_prepare_cpu,
1527 .teardown.single = NULL,
1528 },
1529 [CPUHP_HRTIMERS_PREPARE] = {
1530 .name = "hrtimers:prepare",
1531 .startup.single = hrtimers_prepare_cpu,
1532 .teardown.single = hrtimers_dead_cpu,
1533 },
1534 [CPUHP_SMPCFD_PREPARE] = {
1535 .name = "smpcfd:prepare",
1536 .startup.single = smpcfd_prepare_cpu,
1537 .teardown.single = smpcfd_dead_cpu,
1538 },
1539 [CPUHP_RELAY_PREPARE] = {
1540 .name = "relay:prepare",
1541 .startup.single = relay_prepare_cpu,
1542 .teardown.single = NULL,
1543 },
1544 [CPUHP_SLAB_PREPARE] = {
1545 .name = "slab:prepare",
1546 .startup.single = slab_prepare_cpu,
1547 .teardown.single = slab_dead_cpu,
1548 },
1549 [CPUHP_RCUTREE_PREP] = {
1550 .name = "RCU/tree:prepare",
1551 .startup.single = rcutree_prepare_cpu,
1552 .teardown.single = rcutree_dead_cpu,
1553 },
1554 /*
1555 * On the tear-down path, timers_dead_cpu() must be invoked
1556 * before blk_mq_queue_reinit_notify() from notify_dead(),
1557 * otherwise a RCU stall occurs.
1558 */
1559 [CPUHP_TIMERS_PREPARE] = {
1560 .name = "timers:prepare",
1561 .startup.single = timers_prepare_cpu,
1562 .teardown.single = timers_dead_cpu,
1563 },
1564 /* Kicks the plugged cpu into life */
1565 [CPUHP_BRINGUP_CPU] = {
1566 .name = "cpu:bringup",
1567 .startup.single = bringup_cpu,
1568 .teardown.single = finish_cpu,
1569 .cant_stop = true,
1570 },
1571 /* Final state before CPU kills itself */
1572 [CPUHP_AP_IDLE_DEAD] = {
1573 .name = "idle:dead",
1574 },
1575 /*
1576 * Last state before CPU enters the idle loop to die. Transient state
1577 * for synchronization.
1578 */
1579 [CPUHP_AP_OFFLINE] = {
1580 .name = "ap:offline",
1581 .cant_stop = true,
1582 },
1583 /* First state is scheduler control. Interrupts are disabled */
1584 [CPUHP_AP_SCHED_STARTING] = {
1585 .name = "sched:starting",
1586 .startup.single = sched_cpu_starting,
1587 .teardown.single = sched_cpu_dying,
1588 },
1589 [CPUHP_AP_RCUTREE_DYING] = {
1590 .name = "RCU/tree:dying",
1591 .startup.single = NULL,
1592 .teardown.single = rcutree_dying_cpu,
1593 },
1594 [CPUHP_AP_SMPCFD_DYING] = {
1595 .name = "smpcfd:dying",
1596 .startup.single = NULL,
1597 .teardown.single = smpcfd_dying_cpu,
1598 },
1599 /* Entry state on starting. Interrupts enabled from here on. Transient
1600 * state for synchronsization */
1601 [CPUHP_AP_ONLINE] = {
1602 .name = "ap:online",
1603 },
1604 /*
1605 * Handled on controll processor until the plugged processor manages
1606 * this itself.
1607 */
1608 [CPUHP_TEARDOWN_CPU] = {
1609 .name = "cpu:teardown",
1610 .startup.single = NULL,
1611 .teardown.single = takedown_cpu,
1612 .cant_stop = true,
1613 },
1614 /* Handle smpboot threads park/unpark */
1615 [CPUHP_AP_SMPBOOT_THREADS] = {
1616 .name = "smpboot/threads:online",
1617 .startup.single = smpboot_unpark_threads,
1618 .teardown.single = smpboot_park_threads,
1619 },
1620 [CPUHP_AP_IRQ_AFFINITY_ONLINE] = {
1621 .name = "irq/affinity:online",
1622 .startup.single = irq_affinity_online_cpu,
1623 .teardown.single = NULL,
1624 },
1625 [CPUHP_AP_PERF_ONLINE] = {
1626 .name = "perf:online",
1627 .startup.single = perf_event_init_cpu,
1628 .teardown.single = perf_event_exit_cpu,
1629 },
1630 [CPUHP_AP_WATCHDOG_ONLINE] = {
1631 .name = "lockup_detector:online",
1632 .startup.single = lockup_detector_online_cpu,
1633 .teardown.single = lockup_detector_offline_cpu,
1634 },
1635 [CPUHP_AP_WORKQUEUE_ONLINE] = {
1636 .name = "workqueue:online",
1637 .startup.single = workqueue_online_cpu,
1638 .teardown.single = workqueue_offline_cpu,
1639 },
1640 [CPUHP_AP_RCUTREE_ONLINE] = {
1641 .name = "RCU/tree:online",
1642 .startup.single = rcutree_online_cpu,
1643 .teardown.single = rcutree_offline_cpu,
1644 },
1645#endif
1646 /*
1647 * The dynamically registered state space is here
1648 */
1649
1650#ifdef CONFIG_SMP
1651 /* Last state is scheduler control setting the cpu active */
1652 [CPUHP_AP_ACTIVE] = {
1653 .name = "sched:active",
1654 .startup.single = sched_cpu_activate,
1655 .teardown.single = sched_cpu_deactivate,
1656 },
1657#endif
1658
1659 /* CPU is fully up and running. */
1660 [CPUHP_ONLINE] = {
1661 .name = "online",
1662 .startup.single = NULL,
1663 .teardown.single = NULL,
1664 },
1665};
1666
1667/* Sanity check for callbacks */
1668static int cpuhp_cb_check(enum cpuhp_state state)
1669{
1670 if (state <= CPUHP_OFFLINE || state >= CPUHP_ONLINE)
1671 return -EINVAL;
1672 return 0;
1673}
1674
1675/*
1676 * Returns a free for dynamic slot assignment of the Online state. The states
1677 * are protected by the cpuhp_slot_states mutex and an empty slot is identified
1678 * by having no name assigned.
1679 */
1680static int cpuhp_reserve_state(enum cpuhp_state state)
1681{
1682 enum cpuhp_state i, end;
1683 struct cpuhp_step *step;
1684
1685 switch (state) {
1686 case CPUHP_AP_ONLINE_DYN:
1687 step = cpuhp_hp_states + CPUHP_AP_ONLINE_DYN;
1688 end = CPUHP_AP_ONLINE_DYN_END;
1689 break;
1690 case CPUHP_BP_PREPARE_DYN:
1691 step = cpuhp_hp_states + CPUHP_BP_PREPARE_DYN;
1692 end = CPUHP_BP_PREPARE_DYN_END;
1693 break;
1694 default:
1695 return -EINVAL;
1696 }
1697
1698 for (i = state; i <= end; i++, step++) {
1699 if (!step->name)
1700 return i;
1701 }
1702 WARN(1, "No more dynamic states available for CPU hotplug\n");
1703 return -ENOSPC;
1704}
1705
1706static int cpuhp_store_callbacks(enum cpuhp_state state, const char *name,
1707 int (*startup)(unsigned int cpu),
1708 int (*teardown)(unsigned int cpu),
1709 bool multi_instance)
1710{
1711 /* (Un)Install the callbacks for further cpu hotplug operations */
1712 struct cpuhp_step *sp;
1713 int ret = 0;
1714
1715 /*
1716 * If name is NULL, then the state gets removed.
1717 *
1718 * CPUHP_AP_ONLINE_DYN and CPUHP_BP_PREPARE_DYN are handed out on
1719 * the first allocation from these dynamic ranges, so the removal
1720 * would trigger a new allocation and clear the wrong (already
1721 * empty) state, leaving the callbacks of the to be cleared state
1722 * dangling, which causes wreckage on the next hotplug operation.
1723 */
1724 if (name && (state == CPUHP_AP_ONLINE_DYN ||
1725 state == CPUHP_BP_PREPARE_DYN)) {
1726 ret = cpuhp_reserve_state(state);
1727 if (ret < 0)
1728 return ret;
1729 state = ret;
1730 }
1731 sp = cpuhp_get_step(state);
1732 if (name && sp->name)
1733 return -EBUSY;
1734
1735 sp->startup.single = startup;
1736 sp->teardown.single = teardown;
1737 sp->name = name;
1738 sp->multi_instance = multi_instance;
1739 INIT_HLIST_HEAD(&sp->list);
1740 return ret;
1741}
1742
1743static void *cpuhp_get_teardown_cb(enum cpuhp_state state)
1744{
1745 return cpuhp_get_step(state)->teardown.single;
1746}
1747
1748/*
1749 * Call the startup/teardown function for a step either on the AP or
1750 * on the current CPU.
1751 */
1752static int cpuhp_issue_call(int cpu, enum cpuhp_state state, bool bringup,
1753 struct hlist_node *node)
1754{
1755 struct cpuhp_step *sp = cpuhp_get_step(state);
1756 int ret;
1757
1758 /*
1759 * If there's nothing to do, we done.
1760 * Relies on the union for multi_instance.
1761 */
1762 if ((bringup && !sp->startup.single) ||
1763 (!bringup && !sp->teardown.single))
1764 return 0;
1765 /*
1766 * The non AP bound callbacks can fail on bringup. On teardown
1767 * e.g. module removal we crash for now.
1768 */
1769#ifdef CONFIG_SMP
1770 if (cpuhp_is_ap_state(state))
1771 ret = cpuhp_invoke_ap_callback(cpu, state, bringup, node);
1772 else
1773 ret = cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
1774#else
1775 ret = cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
1776#endif
1777 BUG_ON(ret && !bringup);
1778 return ret;
1779}
1780
1781/*
1782 * Called from __cpuhp_setup_state on a recoverable failure.
1783 *
1784 * Note: The teardown callbacks for rollback are not allowed to fail!
1785 */
1786static void cpuhp_rollback_install(int failedcpu, enum cpuhp_state state,
1787 struct hlist_node *node)
1788{
1789 int cpu;
1790
1791 /* Roll back the already executed steps on the other cpus */
1792 for_each_present_cpu(cpu) {
1793 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1794 int cpustate = st->state;
1795
1796 if (cpu >= failedcpu)
1797 break;
1798
1799 /* Did we invoke the startup call on that cpu ? */
1800 if (cpustate >= state)
1801 cpuhp_issue_call(cpu, state, false, node);
1802 }
1803}
1804
1805int __cpuhp_state_add_instance_cpuslocked(enum cpuhp_state state,
1806 struct hlist_node *node,
1807 bool invoke)
1808{
1809 struct cpuhp_step *sp;
1810 int cpu;
1811 int ret;
1812
1813 lockdep_assert_cpus_held();
1814
1815 sp = cpuhp_get_step(state);
1816 if (sp->multi_instance == false)
1817 return -EINVAL;
1818
1819 mutex_lock(&cpuhp_state_mutex);
1820
1821 if (!invoke || !sp->startup.multi)
1822 goto add_node;
1823
1824 /*
1825 * Try to call the startup callback for each present cpu
1826 * depending on the hotplug state of the cpu.
1827 */
1828 for_each_present_cpu(cpu) {
1829 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1830 int cpustate = st->state;
1831
1832 if (cpustate < state)
1833 continue;
1834
1835 ret = cpuhp_issue_call(cpu, state, true, node);
1836 if (ret) {
1837 if (sp->teardown.multi)
1838 cpuhp_rollback_install(cpu, state, node);
1839 goto unlock;
1840 }
1841 }
1842add_node:
1843 ret = 0;
1844 hlist_add_head(node, &sp->list);
1845unlock:
1846 mutex_unlock(&cpuhp_state_mutex);
1847 return ret;
1848}
1849
1850int __cpuhp_state_add_instance(enum cpuhp_state state, struct hlist_node *node,
1851 bool invoke)
1852{
1853 int ret;
1854
1855 cpus_read_lock();
1856 ret = __cpuhp_state_add_instance_cpuslocked(state, node, invoke);
1857 cpus_read_unlock();
1858 return ret;
1859}
1860EXPORT_SYMBOL_GPL(__cpuhp_state_add_instance);
1861
1862/**
1863 * __cpuhp_setup_state_cpuslocked - Setup the callbacks for an hotplug machine state
1864 * @state: The state to setup
1865 * @invoke: If true, the startup function is invoked for cpus where
1866 * cpu state >= @state
1867 * @startup: startup callback function
1868 * @teardown: teardown callback function
1869 * @multi_instance: State is set up for multiple instances which get
1870 * added afterwards.
1871 *
1872 * The caller needs to hold cpus read locked while calling this function.
1873 * Returns:
1874 * On success:
1875 * Positive state number if @state is CPUHP_AP_ONLINE_DYN
1876 * 0 for all other states
1877 * On failure: proper (negative) error code
1878 */
1879int __cpuhp_setup_state_cpuslocked(enum cpuhp_state state,
1880 const char *name, bool invoke,
1881 int (*startup)(unsigned int cpu),
1882 int (*teardown)(unsigned int cpu),
1883 bool multi_instance)
1884{
1885 int cpu, ret = 0;
1886 bool dynstate;
1887
1888 lockdep_assert_cpus_held();
1889
1890 if (cpuhp_cb_check(state) || !name)
1891 return -EINVAL;
1892
1893 mutex_lock(&cpuhp_state_mutex);
1894
1895 ret = cpuhp_store_callbacks(state, name, startup, teardown,
1896 multi_instance);
1897
1898 dynstate = state == CPUHP_AP_ONLINE_DYN;
1899 if (ret > 0 && dynstate) {
1900 state = ret;
1901 ret = 0;
1902 }
1903
1904 if (ret || !invoke || !startup)
1905 goto out;
1906
1907 /*
1908 * Try to call the startup callback for each present cpu
1909 * depending on the hotplug state of the cpu.
1910 */
1911 for_each_present_cpu(cpu) {
1912 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1913 int cpustate = st->state;
1914
1915 if (cpustate < state)
1916 continue;
1917
1918 ret = cpuhp_issue_call(cpu, state, true, NULL);
1919 if (ret) {
1920 if (teardown)
1921 cpuhp_rollback_install(cpu, state, NULL);
1922 cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
1923 goto out;
1924 }
1925 }
1926out:
1927 mutex_unlock(&cpuhp_state_mutex);
1928 /*
1929 * If the requested state is CPUHP_AP_ONLINE_DYN, return the
1930 * dynamically allocated state in case of success.
1931 */
1932 if (!ret && dynstate)
1933 return state;
1934 return ret;
1935}
1936EXPORT_SYMBOL(__cpuhp_setup_state_cpuslocked);
1937
1938int __cpuhp_setup_state(enum cpuhp_state state,
1939 const char *name, bool invoke,
1940 int (*startup)(unsigned int cpu),
1941 int (*teardown)(unsigned int cpu),
1942 bool multi_instance)
1943{
1944 int ret;
1945
1946 cpus_read_lock();
1947 ret = __cpuhp_setup_state_cpuslocked(state, name, invoke, startup,
1948 teardown, multi_instance);
1949 cpus_read_unlock();
1950 return ret;
1951}
1952EXPORT_SYMBOL(__cpuhp_setup_state);
1953
1954int __cpuhp_state_remove_instance(enum cpuhp_state state,
1955 struct hlist_node *node, bool invoke)
1956{
1957 struct cpuhp_step *sp = cpuhp_get_step(state);
1958 int cpu;
1959
1960 BUG_ON(cpuhp_cb_check(state));
1961
1962 if (!sp->multi_instance)
1963 return -EINVAL;
1964
1965 cpus_read_lock();
1966 mutex_lock(&cpuhp_state_mutex);
1967
1968 if (!invoke || !cpuhp_get_teardown_cb(state))
1969 goto remove;
1970 /*
1971 * Call the teardown callback for each present cpu depending
1972 * on the hotplug state of the cpu. This function is not
1973 * allowed to fail currently!
1974 */
1975 for_each_present_cpu(cpu) {
1976 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1977 int cpustate = st->state;
1978
1979 if (cpustate >= state)
1980 cpuhp_issue_call(cpu, state, false, node);
1981 }
1982
1983remove:
1984 hlist_del(node);
1985 mutex_unlock(&cpuhp_state_mutex);
1986 cpus_read_unlock();
1987
1988 return 0;
1989}
1990EXPORT_SYMBOL_GPL(__cpuhp_state_remove_instance);
1991
1992/**
1993 * __cpuhp_remove_state_cpuslocked - Remove the callbacks for an hotplug machine state
1994 * @state: The state to remove
1995 * @invoke: If true, the teardown function is invoked for cpus where
1996 * cpu state >= @state
1997 *
1998 * The caller needs to hold cpus read locked while calling this function.
1999 * The teardown callback is currently not allowed to fail. Think
2000 * about module removal!
2001 */
2002void __cpuhp_remove_state_cpuslocked(enum cpuhp_state state, bool invoke)
2003{
2004 struct cpuhp_step *sp = cpuhp_get_step(state);
2005 int cpu;
2006
2007 BUG_ON(cpuhp_cb_check(state));
2008
2009 lockdep_assert_cpus_held();
2010
2011 mutex_lock(&cpuhp_state_mutex);
2012 if (sp->multi_instance) {
2013 WARN(!hlist_empty(&sp->list),
2014 "Error: Removing state %d which has instances left.\n",
2015 state);
2016 goto remove;
2017 }
2018
2019 if (!invoke || !cpuhp_get_teardown_cb(state))
2020 goto remove;
2021
2022 /*
2023 * Call the teardown callback for each present cpu depending
2024 * on the hotplug state of the cpu. This function is not
2025 * allowed to fail currently!
2026 */
2027 for_each_present_cpu(cpu) {
2028 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
2029 int cpustate = st->state;
2030
2031 if (cpustate >= state)
2032 cpuhp_issue_call(cpu, state, false, NULL);
2033 }
2034remove:
2035 cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
2036 mutex_unlock(&cpuhp_state_mutex);
2037}
2038EXPORT_SYMBOL(__cpuhp_remove_state_cpuslocked);
2039
2040void __cpuhp_remove_state(enum cpuhp_state state, bool invoke)
2041{
2042 cpus_read_lock();
2043 __cpuhp_remove_state_cpuslocked(state, invoke);
2044 cpus_read_unlock();
2045}
2046EXPORT_SYMBOL(__cpuhp_remove_state);
2047
2048#ifdef CONFIG_HOTPLUG_SMT
2049static void cpuhp_offline_cpu_device(unsigned int cpu)
2050{
2051 struct device *dev = get_cpu_device(cpu);
2052
2053 dev->offline = true;
2054 /* Tell user space about the state change */
2055 kobject_uevent(&dev->kobj, KOBJ_OFFLINE);
2056}
2057
2058static void cpuhp_online_cpu_device(unsigned int cpu)
2059{
2060 struct device *dev = get_cpu_device(cpu);
2061
2062 dev->offline = false;
2063 /* Tell user space about the state change */
2064 kobject_uevent(&dev->kobj, KOBJ_ONLINE);
2065}
2066
2067int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval)
2068{
2069 int cpu, ret = 0;
2070
2071 cpu_maps_update_begin();
2072 for_each_online_cpu(cpu) {
2073 if (topology_is_primary_thread(cpu))
2074 continue;
2075 ret = cpu_down_maps_locked(cpu, CPUHP_OFFLINE);
2076 if (ret)
2077 break;
2078 /*
2079 * As this needs to hold the cpu maps lock it's impossible
2080 * to call device_offline() because that ends up calling
2081 * cpu_down() which takes cpu maps lock. cpu maps lock
2082 * needs to be held as this might race against in kernel
2083 * abusers of the hotplug machinery (thermal management).
2084 *
2085 * So nothing would update device:offline state. That would
2086 * leave the sysfs entry stale and prevent onlining after
2087 * smt control has been changed to 'off' again. This is
2088 * called under the sysfs hotplug lock, so it is properly
2089 * serialized against the regular offline usage.
2090 */
2091 cpuhp_offline_cpu_device(cpu);
2092 }
2093 if (!ret)
2094 cpu_smt_control = ctrlval;
2095 cpu_maps_update_done();
2096 return ret;
2097}
2098
2099int cpuhp_smt_enable(void)
2100{
2101 int cpu, ret = 0;
2102
2103 cpu_maps_update_begin();
2104 cpu_smt_control = CPU_SMT_ENABLED;
2105 for_each_present_cpu(cpu) {
2106 /* Skip online CPUs and CPUs on offline nodes */
2107 if (cpu_online(cpu) || !node_online(cpu_to_node(cpu)))
2108 continue;
2109 ret = _cpu_up(cpu, 0, CPUHP_ONLINE);
2110 if (ret)
2111 break;
2112 /* See comment in cpuhp_smt_disable() */
2113 cpuhp_online_cpu_device(cpu);
2114 }
2115 cpu_maps_update_done();
2116 return ret;
2117}
2118#endif
2119
2120#if defined(CONFIG_SYSFS) && defined(CONFIG_HOTPLUG_CPU)
2121static ssize_t show_cpuhp_state(struct device *dev,
2122 struct device_attribute *attr, char *buf)
2123{
2124 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2125
2126 return sprintf(buf, "%d\n", st->state);
2127}
2128static DEVICE_ATTR(state, 0444, show_cpuhp_state, NULL);
2129
2130static ssize_t write_cpuhp_target(struct device *dev,
2131 struct device_attribute *attr,
2132 const char *buf, size_t count)
2133{
2134 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2135 struct cpuhp_step *sp;
2136 int target, ret;
2137
2138 ret = kstrtoint(buf, 10, &target);
2139 if (ret)
2140 return ret;
2141
2142#ifdef CONFIG_CPU_HOTPLUG_STATE_CONTROL
2143 if (target < CPUHP_OFFLINE || target > CPUHP_ONLINE)
2144 return -EINVAL;
2145#else
2146 if (target != CPUHP_OFFLINE && target != CPUHP_ONLINE)
2147 return -EINVAL;
2148#endif
2149
2150 ret = lock_device_hotplug_sysfs();
2151 if (ret)
2152 return ret;
2153
2154 mutex_lock(&cpuhp_state_mutex);
2155 sp = cpuhp_get_step(target);
2156 ret = !sp->name || sp->cant_stop ? -EINVAL : 0;
2157 mutex_unlock(&cpuhp_state_mutex);
2158 if (ret)
2159 goto out;
2160
2161 if (st->state < target)
2162 ret = cpu_up(dev->id, target);
2163 else
2164 ret = cpu_down(dev->id, target);
2165out:
2166 unlock_device_hotplug();
2167 return ret ? ret : count;
2168}
2169
2170static ssize_t show_cpuhp_target(struct device *dev,
2171 struct device_attribute *attr, char *buf)
2172{
2173 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2174
2175 return sprintf(buf, "%d\n", st->target);
2176}
2177static DEVICE_ATTR(target, 0644, show_cpuhp_target, write_cpuhp_target);
2178
2179
2180static ssize_t write_cpuhp_fail(struct device *dev,
2181 struct device_attribute *attr,
2182 const char *buf, size_t count)
2183{
2184 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2185 struct cpuhp_step *sp;
2186 int fail, ret;
2187
2188 ret = kstrtoint(buf, 10, &fail);
2189 if (ret)
2190 return ret;
2191
2192 if (fail < CPUHP_OFFLINE || fail > CPUHP_ONLINE)
2193 return -EINVAL;
2194
2195 /*
2196 * Cannot fail STARTING/DYING callbacks.
2197 */
2198 if (cpuhp_is_atomic_state(fail))
2199 return -EINVAL;
2200
2201 /*
2202 * Cannot fail anything that doesn't have callbacks.
2203 */
2204 mutex_lock(&cpuhp_state_mutex);
2205 sp = cpuhp_get_step(fail);
2206 if (!sp->startup.single && !sp->teardown.single)
2207 ret = -EINVAL;
2208 mutex_unlock(&cpuhp_state_mutex);
2209 if (ret)
2210 return ret;
2211
2212 st->fail = fail;
2213
2214 return count;
2215}
2216
2217static ssize_t show_cpuhp_fail(struct device *dev,
2218 struct device_attribute *attr, char *buf)
2219{
2220 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2221
2222 return sprintf(buf, "%d\n", st->fail);
2223}
2224
2225static DEVICE_ATTR(fail, 0644, show_cpuhp_fail, write_cpuhp_fail);
2226
2227static struct attribute *cpuhp_cpu_attrs[] = {
2228 &dev_attr_state.attr,
2229 &dev_attr_target.attr,
2230 &dev_attr_fail.attr,
2231 NULL
2232};
2233
2234static const struct attribute_group cpuhp_cpu_attr_group = {
2235 .attrs = cpuhp_cpu_attrs,
2236 .name = "hotplug",
2237 NULL
2238};
2239
2240static ssize_t show_cpuhp_states(struct device *dev,
2241 struct device_attribute *attr, char *buf)
2242{
2243 ssize_t cur, res = 0;
2244 int i;
2245
2246 mutex_lock(&cpuhp_state_mutex);
2247 for (i = CPUHP_OFFLINE; i <= CPUHP_ONLINE; i++) {
2248 struct cpuhp_step *sp = cpuhp_get_step(i);
2249
2250 if (sp->name) {
2251 cur = sprintf(buf, "%3d: %s\n", i, sp->name);
2252 buf += cur;
2253 res += cur;
2254 }
2255 }
2256 mutex_unlock(&cpuhp_state_mutex);
2257 return res;
2258}
2259static DEVICE_ATTR(states, 0444, show_cpuhp_states, NULL);
2260
2261static struct attribute *cpuhp_cpu_root_attrs[] = {
2262 &dev_attr_states.attr,
2263 NULL
2264};
2265
2266static const struct attribute_group cpuhp_cpu_root_attr_group = {
2267 .attrs = cpuhp_cpu_root_attrs,
2268 .name = "hotplug",
2269 NULL
2270};
2271
2272#ifdef CONFIG_HOTPLUG_SMT
2273
2274static ssize_t
2275__store_smt_control(struct device *dev, struct device_attribute *attr,
2276 const char *buf, size_t count)
2277{
2278 int ctrlval, ret;
2279
2280 if (sysfs_streq(buf, "on"))
2281 ctrlval = CPU_SMT_ENABLED;
2282 else if (sysfs_streq(buf, "off"))
2283 ctrlval = CPU_SMT_DISABLED;
2284 else if (sysfs_streq(buf, "forceoff"))
2285 ctrlval = CPU_SMT_FORCE_DISABLED;
2286 else
2287 return -EINVAL;
2288
2289 if (cpu_smt_control == CPU_SMT_FORCE_DISABLED)
2290 return -EPERM;
2291
2292 if (cpu_smt_control == CPU_SMT_NOT_SUPPORTED)
2293 return -ENODEV;
2294
2295 ret = lock_device_hotplug_sysfs();
2296 if (ret)
2297 return ret;
2298
2299 if (ctrlval != cpu_smt_control) {
2300 switch (ctrlval) {
2301 case CPU_SMT_ENABLED:
2302 ret = cpuhp_smt_enable();
2303 break;
2304 case CPU_SMT_DISABLED:
2305 case CPU_SMT_FORCE_DISABLED:
2306 ret = cpuhp_smt_disable(ctrlval);
2307 break;
2308 }
2309 }
2310
2311 unlock_device_hotplug();
2312 return ret ? ret : count;
2313}
2314
2315#else /* !CONFIG_HOTPLUG_SMT */
2316static ssize_t
2317__store_smt_control(struct device *dev, struct device_attribute *attr,
2318 const char *buf, size_t count)
2319{
2320 return -ENODEV;
2321}
2322#endif /* CONFIG_HOTPLUG_SMT */
2323
2324static const char *smt_states[] = {
2325 [CPU_SMT_ENABLED] = "on",
2326 [CPU_SMT_DISABLED] = "off",
2327 [CPU_SMT_FORCE_DISABLED] = "forceoff",
2328 [CPU_SMT_NOT_SUPPORTED] = "notsupported",
2329 [CPU_SMT_NOT_IMPLEMENTED] = "notimplemented",
2330};
2331
2332static ssize_t
2333show_smt_control(struct device *dev, struct device_attribute *attr, char *buf)
2334{
2335 const char *state = smt_states[cpu_smt_control];
2336
2337 return snprintf(buf, PAGE_SIZE - 2, "%s\n", state);
2338}
2339
2340static ssize_t
2341store_smt_control(struct device *dev, struct device_attribute *attr,
2342 const char *buf, size_t count)
2343{
2344 return __store_smt_control(dev, attr, buf, count);
2345}
2346static DEVICE_ATTR(control, 0644, show_smt_control, store_smt_control);
2347
2348static ssize_t
2349show_smt_active(struct device *dev, struct device_attribute *attr, char *buf)
2350{
2351 return snprintf(buf, PAGE_SIZE - 2, "%d\n", sched_smt_active());
2352}
2353static DEVICE_ATTR(active, 0444, show_smt_active, NULL);
2354
2355static struct attribute *cpuhp_smt_attrs[] = {
2356 &dev_attr_control.attr,
2357 &dev_attr_active.attr,
2358 NULL
2359};
2360
2361static const struct attribute_group cpuhp_smt_attr_group = {
2362 .attrs = cpuhp_smt_attrs,
2363 .name = "smt",
2364 NULL
2365};
2366
2367static int __init cpu_smt_sysfs_init(void)
2368{
2369 return sysfs_create_group(&cpu_subsys.dev_root->kobj,
2370 &cpuhp_smt_attr_group);
2371}
2372
2373static int __init cpuhp_sysfs_init(void)
2374{
2375 int cpu, ret;
2376
2377 ret = cpu_smt_sysfs_init();
2378 if (ret)
2379 return ret;
2380
2381 ret = sysfs_create_group(&cpu_subsys.dev_root->kobj,
2382 &cpuhp_cpu_root_attr_group);
2383 if (ret)
2384 return ret;
2385
2386 for_each_possible_cpu(cpu) {
2387 struct device *dev = get_cpu_device(cpu);
2388
2389 if (!dev)
2390 continue;
2391 ret = sysfs_create_group(&dev->kobj, &cpuhp_cpu_attr_group);
2392 if (ret)
2393 return ret;
2394 }
2395 return 0;
2396}
2397device_initcall(cpuhp_sysfs_init);
2398#endif /* CONFIG_SYSFS && CONFIG_HOTPLUG_CPU */
2399
2400/*
2401 * cpu_bit_bitmap[] is a special, "compressed" data structure that
2402 * represents all NR_CPUS bits binary values of 1<<nr.
2403 *
2404 * It is used by cpumask_of() to get a constant address to a CPU
2405 * mask value that has a single bit set only.
2406 */
2407
2408/* cpu_bit_bitmap[0] is empty - so we can back into it */
2409#define MASK_DECLARE_1(x) [x+1][0] = (1UL << (x))
2410#define MASK_DECLARE_2(x) MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
2411#define MASK_DECLARE_4(x) MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
2412#define MASK_DECLARE_8(x) MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
2413
2414const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
2415
2416 MASK_DECLARE_8(0), MASK_DECLARE_8(8),
2417 MASK_DECLARE_8(16), MASK_DECLARE_8(24),
2418#if BITS_PER_LONG > 32
2419 MASK_DECLARE_8(32), MASK_DECLARE_8(40),
2420 MASK_DECLARE_8(48), MASK_DECLARE_8(56),
2421#endif
2422};
2423EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
2424
2425const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
2426EXPORT_SYMBOL(cpu_all_bits);
2427
2428#ifdef CONFIG_INIT_ALL_POSSIBLE
2429struct cpumask __cpu_possible_mask __read_mostly
2430 = {CPU_BITS_ALL};
2431#else
2432struct cpumask __cpu_possible_mask __read_mostly;
2433#endif
2434EXPORT_SYMBOL(__cpu_possible_mask);
2435
2436struct cpumask __cpu_online_mask __read_mostly;
2437EXPORT_SYMBOL(__cpu_online_mask);
2438
2439struct cpumask __cpu_present_mask __read_mostly;
2440EXPORT_SYMBOL(__cpu_present_mask);
2441
2442struct cpumask __cpu_active_mask __read_mostly;
2443EXPORT_SYMBOL(__cpu_active_mask);
2444
2445atomic_t __num_online_cpus __read_mostly;
2446EXPORT_SYMBOL(__num_online_cpus);
2447
2448void init_cpu_present(const struct cpumask *src)
2449{
2450 cpumask_copy(&__cpu_present_mask, src);
2451}
2452
2453void init_cpu_possible(const struct cpumask *src)
2454{
2455 cpumask_copy(&__cpu_possible_mask, src);
2456}
2457
2458void init_cpu_online(const struct cpumask *src)
2459{
2460 cpumask_copy(&__cpu_online_mask, src);
2461}
2462
2463void set_cpu_online(unsigned int cpu, bool online)
2464{
2465 /*
2466 * atomic_inc/dec() is required to handle the horrid abuse of this
2467 * function by the reboot and kexec code which invoke it from
2468 * IPI/NMI broadcasts when shutting down CPUs. Invocation from
2469 * regular CPU hotplug is properly serialized.
2470 *
2471 * Note, that the fact that __num_online_cpus is of type atomic_t
2472 * does not protect readers which are not serialized against
2473 * concurrent hotplug operations.
2474 */
2475 if (online) {
2476 if (!cpumask_test_and_set_cpu(cpu, &__cpu_online_mask))
2477 atomic_inc(&__num_online_cpus);
2478 } else {
2479 if (cpumask_test_and_clear_cpu(cpu, &__cpu_online_mask))
2480 atomic_dec(&__num_online_cpus);
2481 }
2482}
2483
2484/*
2485 * Activate the first processor.
2486 */
2487void __init boot_cpu_init(void)
2488{
2489 int cpu = smp_processor_id();
2490
2491 /* Mark the boot cpu "present", "online" etc for SMP and UP case */
2492 set_cpu_online(cpu, true);
2493 set_cpu_active(cpu, true);
2494 set_cpu_present(cpu, true);
2495 set_cpu_possible(cpu, true);
2496
2497#ifdef CONFIG_SMP
2498 __boot_cpu_id = cpu;
2499#endif
2500}
2501
2502/*
2503 * Must be called _AFTER_ setting up the per_cpu areas
2504 */
2505void __init boot_cpu_hotplug_init(void)
2506{
2507#ifdef CONFIG_SMP
2508 cpumask_set_cpu(smp_processor_id(), &cpus_booted_once_mask);
2509#endif
2510 this_cpu_write(cpuhp_state.state, CPUHP_ONLINE);
2511}
2512
2513/*
2514 * These are used for a global "mitigations=" cmdline option for toggling
2515 * optional CPU mitigations.
2516 */
2517enum cpu_mitigations {
2518 CPU_MITIGATIONS_OFF,
2519 CPU_MITIGATIONS_AUTO,
2520 CPU_MITIGATIONS_AUTO_NOSMT,
2521};
2522
2523static enum cpu_mitigations cpu_mitigations __ro_after_init =
2524 CPU_MITIGATIONS_AUTO;
2525
2526static int __init mitigations_parse_cmdline(char *arg)
2527{
2528 if (!strcmp(arg, "off"))
2529 cpu_mitigations = CPU_MITIGATIONS_OFF;
2530 else if (!strcmp(arg, "auto"))
2531 cpu_mitigations = CPU_MITIGATIONS_AUTO;
2532 else if (!strcmp(arg, "auto,nosmt"))
2533 cpu_mitigations = CPU_MITIGATIONS_AUTO_NOSMT;
2534 else
2535 pr_crit("Unsupported mitigations=%s, system may still be vulnerable\n",
2536 arg);
2537
2538 return 0;
2539}
2540early_param("mitigations", mitigations_parse_cmdline);
2541
2542/* mitigations=off */
2543bool cpu_mitigations_off(void)
2544{
2545 return cpu_mitigations == CPU_MITIGATIONS_OFF;
2546}
2547EXPORT_SYMBOL_GPL(cpu_mitigations_off);
2548
2549/* mitigations=auto,nosmt */
2550bool cpu_mitigations_auto_nosmt(void)
2551{
2552 return cpu_mitigations == CPU_MITIGATIONS_AUTO_NOSMT;
2553}
2554EXPORT_SYMBOL_GPL(cpu_mitigations_auto_nosmt);