projects/linux·blob v5.6-rc1 · refs

2423 lines · 58.0 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/proc_fs.h>
7#include <linux/smp.h>
8#include <linux/init.h>
9#include <linux/notifier.h>
10#include <linux/sched/signal.h>
11#include <linux/sched/hotplug.h>
12#include <linux/sched/isolation.h>
13#include <linux/sched/task.h>
14#include <linux/sched/smt.h>
15#include <linux/unistd.h>
16#include <linux/cpu.h>
17#include <linux/oom.h>
18#include <linux/rcupdate.h>
19#include <linux/export.h>
20#include <linux/bug.h>
21#include <linux/kthread.h>
22#include <linux/stop_machine.h>
23#include <linux/mutex.h>
24#include <linux/gfp.h>
25#include <linux/suspend.h>
26#include <linux/lockdep.h>
27#include <linux/tick.h>
28#include <linux/irq.h>
29#include <linux/nmi.h>
30#include <linux/smpboot.h>
31#include <linux/relay.h>
32#include <linux/slab.h>
33#include <linux/percpu-rwsem.h>
34
35#include <trace/events/power.h>
36#define CREATE_TRACE_POINTS
37#include <trace/events/cpuhp.h>
38
39#include "smpboot.h"
40
41/**
42 * cpuhp_cpu_state - Per cpu hotplug state storage
43 * @state: The current cpu state
44 * @target: The target state
45 * @thread: Pointer to the hotplug thread
46 * @should_run: Thread should execute
47 * @rollback: Perform a rollback
48 * @single: Single callback invocation
49 * @bringup: Single callback bringup or teardown selector
50 * @cb_state: The state for a single callback (install/uninstall)
51 * @result: Result of the operation
52 * @done_up: Signal completion to the issuer of the task for cpu-up
53 * @done_down: Signal completion to the issuer of the task for cpu-down
54 */
55struct cpuhp_cpu_state {
56 enum cpuhp_state state;
57 enum cpuhp_state target;
58 enum cpuhp_state fail;
59#ifdef CONFIG_SMP
60 struct task_struct *thread;
61 bool should_run;
62 bool rollback;
63 bool single;
64 bool bringup;
65 struct hlist_node *node;
66 struct hlist_node *last;
67 enum cpuhp_state cb_state;
68 int result;
69 struct completion done_up;
70 struct completion done_down;
71#endif
72};
73
74static DEFINE_PER_CPU(struct cpuhp_cpu_state, cpuhp_state) = {
75 .fail = CPUHP_INVALID,
76};
77
78#ifdef CONFIG_SMP
79cpumask_t cpus_booted_once_mask;
80#endif
81
82#if defined(CONFIG_LOCKDEP) && defined(CONFIG_SMP)
83static struct lockdep_map cpuhp_state_up_map =
84 STATIC_LOCKDEP_MAP_INIT("cpuhp_state-up", &cpuhp_state_up_map);
85static struct lockdep_map cpuhp_state_down_map =
86 STATIC_LOCKDEP_MAP_INIT("cpuhp_state-down", &cpuhp_state_down_map);
87
88
89static inline void cpuhp_lock_acquire(bool bringup)
90{
91 lock_map_acquire(bringup ? &cpuhp_state_up_map : &cpuhp_state_down_map);
92}
93
94static inline void cpuhp_lock_release(bool bringup)
95{
96 lock_map_release(bringup ? &cpuhp_state_up_map : &cpuhp_state_down_map);
97}
98#else
99
100static inline void cpuhp_lock_acquire(bool bringup) { }
101static inline void cpuhp_lock_release(bool bringup) { }
102
103#endif
104
105/**
106 * cpuhp_step - Hotplug state machine step
107 * @name: Name of the step
108 * @startup: Startup function of the step
109 * @teardown: Teardown function of the step
110 * @cant_stop: Bringup/teardown can't be stopped at this step
111 */
112struct cpuhp_step {
113 const char *name;
114 union {
115 int (*single)(unsigned int cpu);
116 int (*multi)(unsigned int cpu,
117 struct hlist_node *node);
118 } startup;
119 union {
120 int (*single)(unsigned int cpu);
121 int (*multi)(unsigned int cpu,
122 struct hlist_node *node);
123 } teardown;
124 struct hlist_head list;
125 bool cant_stop;
126 bool multi_instance;
127};
128
129static DEFINE_MUTEX(cpuhp_state_mutex);
130static struct cpuhp_step cpuhp_hp_states[];
131
132static struct cpuhp_step *cpuhp_get_step(enum cpuhp_state state)
133{
134 return cpuhp_hp_states + state;
135}
136
137/**
138 * cpuhp_invoke_callback _ Invoke the callbacks for a given state
139 * @cpu: The cpu for which the callback should be invoked
140 * @state: The state to do callbacks for
141 * @bringup: True if the bringup callback should be invoked
142 * @node: For multi-instance, do a single entry callback for install/remove
143 * @lastp: For multi-instance rollback, remember how far we got
144 *
145 * Called from cpu hotplug and from the state register machinery.
146 */
147static int cpuhp_invoke_callback(unsigned int cpu, enum cpuhp_state state,
148 bool bringup, struct hlist_node *node,
149 struct hlist_node **lastp)
150{
151 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
152 struct cpuhp_step *step = cpuhp_get_step(state);
153 int (*cbm)(unsigned int cpu, struct hlist_node *node);
154 int (*cb)(unsigned int cpu);
155 int ret, cnt;
156
157 if (st->fail == state) {
158 st->fail = CPUHP_INVALID;
159
160 if (!(bringup ? step->startup.single : step->teardown.single))
161 return 0;
162
163 return -EAGAIN;
164 }
165
166 if (!step->multi_instance) {
167 WARN_ON_ONCE(lastp && *lastp);
168 cb = bringup ? step->startup.single : step->teardown.single;
169 if (!cb)
170 return 0;
171 trace_cpuhp_enter(cpu, st->target, state, cb);
172 ret = cb(cpu);
173 trace_cpuhp_exit(cpu, st->state, state, ret);
174 return ret;
175 }
176 cbm = bringup ? step->startup.multi : step->teardown.multi;
177 if (!cbm)
178 return 0;
179
180 /* Single invocation for instance add/remove */
181 if (node) {
182 WARN_ON_ONCE(lastp && *lastp);
183 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
184 ret = cbm(cpu, node);
185 trace_cpuhp_exit(cpu, st->state, state, ret);
186 return ret;
187 }
188
189 /* State transition. Invoke on all instances */
190 cnt = 0;
191 hlist_for_each(node, &step->list) {
192 if (lastp && node == *lastp)
193 break;
194
195 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
196 ret = cbm(cpu, node);
197 trace_cpuhp_exit(cpu, st->state, state, ret);
198 if (ret) {
199 if (!lastp)
200 goto err;
201
202 *lastp = node;
203 return ret;
204 }
205 cnt++;
206 }
207 if (lastp)
208 *lastp = NULL;
209 return 0;
210err:
211 /* Rollback the instances if one failed */
212 cbm = !bringup ? step->startup.multi : step->teardown.multi;
213 if (!cbm)
214 return ret;
215
216 hlist_for_each(node, &step->list) {
217 if (!cnt--)
218 break;
219
220 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
221 ret = cbm(cpu, node);
222 trace_cpuhp_exit(cpu, st->state, state, ret);
223 /*
224 * Rollback must not fail,
225 */
226 WARN_ON_ONCE(ret);
227 }
228 return ret;
229}
230
231#ifdef CONFIG_SMP
232static bool cpuhp_is_ap_state(enum cpuhp_state state)
233{
234 /*
235 * The extra check for CPUHP_TEARDOWN_CPU is only for documentation
236 * purposes as that state is handled explicitly in cpu_down.
237 */
238 return state > CPUHP_BRINGUP_CPU && state != CPUHP_TEARDOWN_CPU;
239}
240
241static inline void wait_for_ap_thread(struct cpuhp_cpu_state *st, bool bringup)
242{
243 struct completion *done = bringup ? &st->done_up : &st->done_down;
244 wait_for_completion(done);
245}
246
247static inline void complete_ap_thread(struct cpuhp_cpu_state *st, bool bringup)
248{
249 struct completion *done = bringup ? &st->done_up : &st->done_down;
250 complete(done);
251}
252
253/*
254 * The former STARTING/DYING states, ran with IRQs disabled and must not fail.
255 */
256static bool cpuhp_is_atomic_state(enum cpuhp_state state)
257{
258 return CPUHP_AP_IDLE_DEAD <= state && state < CPUHP_AP_ONLINE;
259}
260
261/* Serializes the updates to cpu_online_mask, cpu_present_mask */
262static DEFINE_MUTEX(cpu_add_remove_lock);
263bool cpuhp_tasks_frozen;
264EXPORT_SYMBOL_GPL(cpuhp_tasks_frozen);
265
266/*
267 * The following two APIs (cpu_maps_update_begin/done) must be used when
268 * attempting to serialize the updates to cpu_online_mask & cpu_present_mask.
269 */
270void cpu_maps_update_begin(void)
271{
272 mutex_lock(&cpu_add_remove_lock);
273}
274
275void cpu_maps_update_done(void)
276{
277 mutex_unlock(&cpu_add_remove_lock);
278}
279
280/*
281 * If set, cpu_up and cpu_down will return -EBUSY and do nothing.
282 * Should always be manipulated under cpu_add_remove_lock
283 */
284static int cpu_hotplug_disabled;
285
286#ifdef CONFIG_HOTPLUG_CPU
287
288DEFINE_STATIC_PERCPU_RWSEM(cpu_hotplug_lock);
289
290void cpus_read_lock(void)
291{
292 percpu_down_read(&cpu_hotplug_lock);
293}
294EXPORT_SYMBOL_GPL(cpus_read_lock);
295
296int cpus_read_trylock(void)
297{
298 return percpu_down_read_trylock(&cpu_hotplug_lock);
299}
300EXPORT_SYMBOL_GPL(cpus_read_trylock);
301
302void cpus_read_unlock(void)
303{
304 percpu_up_read(&cpu_hotplug_lock);
305}
306EXPORT_SYMBOL_GPL(cpus_read_unlock);
307
308void cpus_write_lock(void)
309{
310 percpu_down_write(&cpu_hotplug_lock);
311}
312
313void cpus_write_unlock(void)
314{
315 percpu_up_write(&cpu_hotplug_lock);
316}
317
318void lockdep_assert_cpus_held(void)
319{
320 /*
321 * We can't have hotplug operations before userspace starts running,
322 * and some init codepaths will knowingly not take the hotplug lock.
323 * This is all valid, so mute lockdep until it makes sense to report
324 * unheld locks.
325 */
326 if (system_state < SYSTEM_RUNNING)
327 return;
328
329 percpu_rwsem_assert_held(&cpu_hotplug_lock);
330}
331
332static void lockdep_acquire_cpus_lock(void)
333{
334 rwsem_acquire(&cpu_hotplug_lock.rw_sem.dep_map, 0, 0, _THIS_IP_);
335}
336
337static void lockdep_release_cpus_lock(void)
338{
339 rwsem_release(&cpu_hotplug_lock.rw_sem.dep_map, _THIS_IP_);
340}
341
342/*
343 * Wait for currently running CPU hotplug operations to complete (if any) and
344 * disable future CPU hotplug (from sysfs). The 'cpu_add_remove_lock' protects
345 * the 'cpu_hotplug_disabled' flag. The same lock is also acquired by the
346 * hotplug path before performing hotplug operations. So acquiring that lock
347 * guarantees mutual exclusion from any currently running hotplug operations.
348 */
349void cpu_hotplug_disable(void)
350{
351 cpu_maps_update_begin();
352 cpu_hotplug_disabled++;
353 cpu_maps_update_done();
354}
355EXPORT_SYMBOL_GPL(cpu_hotplug_disable);
356
357static void __cpu_hotplug_enable(void)
358{
359 if (WARN_ONCE(!cpu_hotplug_disabled, "Unbalanced cpu hotplug enable\n"))
360 return;
361 cpu_hotplug_disabled--;
362}
363
364void cpu_hotplug_enable(void)
365{
366 cpu_maps_update_begin();
367 __cpu_hotplug_enable();
368 cpu_maps_update_done();
369}
370EXPORT_SYMBOL_GPL(cpu_hotplug_enable);
371
372#else
373
374static void lockdep_acquire_cpus_lock(void)
375{
376}
377
378static void lockdep_release_cpus_lock(void)
379{
380}
381
382#endif /* CONFIG_HOTPLUG_CPU */
383
384/*
385 * Architectures that need SMT-specific errata handling during SMT hotplug
386 * should override this.
387 */
388void __weak arch_smt_update(void) { }
389
390#ifdef CONFIG_HOTPLUG_SMT
391enum cpuhp_smt_control cpu_smt_control __read_mostly = CPU_SMT_ENABLED;
392
393void __init cpu_smt_disable(bool force)
394{
395 if (!cpu_smt_possible())
396 return;
397
398 if (force) {
399 pr_info("SMT: Force disabled\n");
400 cpu_smt_control = CPU_SMT_FORCE_DISABLED;
401 } else {
402 pr_info("SMT: disabled\n");
403 cpu_smt_control = CPU_SMT_DISABLED;
404 }
405}
406
407/*
408 * The decision whether SMT is supported can only be done after the full
409 * CPU identification. Called from architecture code.
410 */
411void __init cpu_smt_check_topology(void)
412{
413 if (!topology_smt_supported())
414 cpu_smt_control = CPU_SMT_NOT_SUPPORTED;
415}
416
417static int __init smt_cmdline_disable(char *str)
418{
419 cpu_smt_disable(str && !strcmp(str, "force"));
420 return 0;
421}
422early_param("nosmt", smt_cmdline_disable);
423
424static inline bool cpu_smt_allowed(unsigned int cpu)
425{
426 if (cpu_smt_control == CPU_SMT_ENABLED)
427 return true;
428
429 if (topology_is_primary_thread(cpu))
430 return true;
431
432 /*
433 * On x86 it's required to boot all logical CPUs at least once so
434 * that the init code can get a chance to set CR4.MCE on each
435 * CPU. Otherwise, a broadacasted MCE observing CR4.MCE=0b on any
436 * core will shutdown the machine.
437 */
438 return !cpumask_test_cpu(cpu, &cpus_booted_once_mask);
439}
440
441/* Returns true if SMT is not supported of forcefully (irreversibly) disabled */
442bool cpu_smt_possible(void)
443{
444 return cpu_smt_control != CPU_SMT_FORCE_DISABLED &&
445 cpu_smt_control != CPU_SMT_NOT_SUPPORTED;
446}
447EXPORT_SYMBOL_GPL(cpu_smt_possible);
448#else
449static inline bool cpu_smt_allowed(unsigned int cpu) { return true; }
450#endif
451
452static inline enum cpuhp_state
453cpuhp_set_state(struct cpuhp_cpu_state *st, enum cpuhp_state target)
454{
455 enum cpuhp_state prev_state = st->state;
456
457 st->rollback = false;
458 st->last = NULL;
459
460 st->target = target;
461 st->single = false;
462 st->bringup = st->state < target;
463
464 return prev_state;
465}
466
467static inline void
468cpuhp_reset_state(struct cpuhp_cpu_state *st, enum cpuhp_state prev_state)
469{
470 st->rollback = true;
471
472 /*
473 * If we have st->last we need to undo partial multi_instance of this
474 * state first. Otherwise start undo at the previous state.
475 */
476 if (!st->last) {
477 if (st->bringup)
478 st->state--;
479 else
480 st->state++;
481 }
482
483 st->target = prev_state;
484 st->bringup = !st->bringup;
485}
486
487/* Regular hotplug invocation of the AP hotplug thread */
488static void __cpuhp_kick_ap(struct cpuhp_cpu_state *st)
489{
490 if (!st->single && st->state == st->target)
491 return;
492
493 st->result = 0;
494 /*
495 * Make sure the above stores are visible before should_run becomes
496 * true. Paired with the mb() above in cpuhp_thread_fun()
497 */
498 smp_mb();
499 st->should_run = true;
500 wake_up_process(st->thread);
501 wait_for_ap_thread(st, st->bringup);
502}
503
504static int cpuhp_kick_ap(struct cpuhp_cpu_state *st, enum cpuhp_state target)
505{
506 enum cpuhp_state prev_state;
507 int ret;
508
509 prev_state = cpuhp_set_state(st, target);
510 __cpuhp_kick_ap(st);
511 if ((ret = st->result)) {
512 cpuhp_reset_state(st, prev_state);
513 __cpuhp_kick_ap(st);
514 }
515
516 return ret;
517}
518
519static int bringup_wait_for_ap(unsigned int cpu)
520{
521 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
522
523 /* Wait for the CPU to reach CPUHP_AP_ONLINE_IDLE */
524 wait_for_ap_thread(st, true);
525 if (WARN_ON_ONCE((!cpu_online(cpu))))
526 return -ECANCELED;
527
528 /* Unpark the hotplug thread of the target cpu */
529 kthread_unpark(st->thread);
530
531 /*
532 * SMT soft disabling on X86 requires to bring the CPU out of the
533 * BIOS 'wait for SIPI' state in order to set the CR4.MCE bit. The
534 * CPU marked itself as booted_once in notify_cpu_starting() so the
535 * cpu_smt_allowed() check will now return false if this is not the
536 * primary sibling.
537 */
538 if (!cpu_smt_allowed(cpu))
539 return -ECANCELED;
540
541 if (st->target <= CPUHP_AP_ONLINE_IDLE)
542 return 0;
543
544 return cpuhp_kick_ap(st, st->target);
545}
546
547static int bringup_cpu(unsigned int cpu)
548{
549 struct task_struct *idle = idle_thread_get(cpu);
550 int ret;
551
552 /*
553 * Some architectures have to walk the irq descriptors to
554 * setup the vector space for the cpu which comes online.
555 * Prevent irq alloc/free across the bringup.
556 */
557 irq_lock_sparse();
558
559 /* Arch-specific enabling code. */
560 ret = __cpu_up(cpu, idle);
561 irq_unlock_sparse();
562 if (ret)
563 return ret;
564 return bringup_wait_for_ap(cpu);
565}
566
567/*
568 * Hotplug state machine related functions
569 */
570
571static void undo_cpu_up(unsigned int cpu, struct cpuhp_cpu_state *st)
572{
573 for (st->state--; st->state > st->target; st->state--)
574 cpuhp_invoke_callback(cpu, st->state, false, NULL, NULL);
575}
576
577static inline bool can_rollback_cpu(struct cpuhp_cpu_state *st)
578{
579 if (IS_ENABLED(CONFIG_HOTPLUG_CPU))
580 return true;
581 /*
582 * When CPU hotplug is disabled, then taking the CPU down is not
583 * possible because takedown_cpu() and the architecture and
584 * subsystem specific mechanisms are not available. So the CPU
585 * which would be completely unplugged again needs to stay around
586 * in the current state.
587 */
588 return st->state <= CPUHP_BRINGUP_CPU;
589}
590
591static int cpuhp_up_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
592 enum cpuhp_state target)
593{
594 enum cpuhp_state prev_state = st->state;
595 int ret = 0;
596
597 while (st->state < target) {
598 st->state++;
599 ret = cpuhp_invoke_callback(cpu, st->state, true, NULL, NULL);
600 if (ret) {
601 if (can_rollback_cpu(st)) {
602 st->target = prev_state;
603 undo_cpu_up(cpu, st);
604 }
605 break;
606 }
607 }
608 return ret;
609}
610
611/*
612 * The cpu hotplug threads manage the bringup and teardown of the cpus
613 */
614static void cpuhp_create(unsigned int cpu)
615{
616 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
617
618 init_completion(&st->done_up);
619 init_completion(&st->done_down);
620}
621
622static int cpuhp_should_run(unsigned int cpu)
623{
624 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
625
626 return st->should_run;
627}
628
629/*
630 * Execute teardown/startup callbacks on the plugged cpu. Also used to invoke
631 * callbacks when a state gets [un]installed at runtime.
632 *
633 * Each invocation of this function by the smpboot thread does a single AP
634 * state callback.
635 *
636 * It has 3 modes of operation:
637 * - single: runs st->cb_state
638 * - up: runs ++st->state, while st->state < st->target
639 * - down: runs st->state--, while st->state > st->target
640 *
641 * When complete or on error, should_run is cleared and the completion is fired.
642 */
643static void cpuhp_thread_fun(unsigned int cpu)
644{
645 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
646 bool bringup = st->bringup;
647 enum cpuhp_state state;
648
649 if (WARN_ON_ONCE(!st->should_run))
650 return;
651
652 /*
653 * ACQUIRE for the cpuhp_should_run() load of ->should_run. Ensures
654 * that if we see ->should_run we also see the rest of the state.
655 */
656 smp_mb();
657
658 /*
659 * The BP holds the hotplug lock, but we're now running on the AP,
660 * ensure that anybody asserting the lock is held, will actually find
661 * it so.
662 */
663 lockdep_acquire_cpus_lock();
664 cpuhp_lock_acquire(bringup);
665
666 if (st->single) {
667 state = st->cb_state;
668 st->should_run = false;
669 } else {
670 if (bringup) {
671 st->state++;
672 state = st->state;
673 st->should_run = (st->state < st->target);
674 WARN_ON_ONCE(st->state > st->target);
675 } else {
676 state = st->state;
677 st->state--;
678 st->should_run = (st->state > st->target);
679 WARN_ON_ONCE(st->state < st->target);
680 }
681 }
682
683 WARN_ON_ONCE(!cpuhp_is_ap_state(state));
684
685 if (cpuhp_is_atomic_state(state)) {
686 local_irq_disable();
687 st->result = cpuhp_invoke_callback(cpu, state, bringup, st->node, &st->last);
688 local_irq_enable();
689
690 /*
691 * STARTING/DYING must not fail!
692 */
693 WARN_ON_ONCE(st->result);
694 } else {
695 st->result = cpuhp_invoke_callback(cpu, state, bringup, st->node, &st->last);
696 }
697
698 if (st->result) {
699 /*
700 * If we fail on a rollback, we're up a creek without no
701 * paddle, no way forward, no way back. We loose, thanks for
702 * playing.
703 */
704 WARN_ON_ONCE(st->rollback);
705 st->should_run = false;
706 }
707
708 cpuhp_lock_release(bringup);
709 lockdep_release_cpus_lock();
710
711 if (!st->should_run)
712 complete_ap_thread(st, bringup);
713}
714
715/* Invoke a single callback on a remote cpu */
716static int
717cpuhp_invoke_ap_callback(int cpu, enum cpuhp_state state, bool bringup,
718 struct hlist_node *node)
719{
720 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
721 int ret;
722
723 if (!cpu_online(cpu))
724 return 0;
725
726 cpuhp_lock_acquire(false);
727 cpuhp_lock_release(false);
728
729 cpuhp_lock_acquire(true);
730 cpuhp_lock_release(true);
731
732 /*
733 * If we are up and running, use the hotplug thread. For early calls
734 * we invoke the thread function directly.
735 */
736 if (!st->thread)
737 return cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
738
739 st->rollback = false;
740 st->last = NULL;
741
742 st->node = node;
743 st->bringup = bringup;
744 st->cb_state = state;
745 st->single = true;
746
747 __cpuhp_kick_ap(st);
748
749 /*
750 * If we failed and did a partial, do a rollback.
751 */
752 if ((ret = st->result) && st->last) {
753 st->rollback = true;
754 st->bringup = !bringup;
755
756 __cpuhp_kick_ap(st);
757 }
758
759 /*
760 * Clean up the leftovers so the next hotplug operation wont use stale
761 * data.
762 */
763 st->node = st->last = NULL;
764 return ret;
765}
766
767static int cpuhp_kick_ap_work(unsigned int cpu)
768{
769 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
770 enum cpuhp_state prev_state = st->state;
771 int ret;
772
773 cpuhp_lock_acquire(false);
774 cpuhp_lock_release(false);
775
776 cpuhp_lock_acquire(true);
777 cpuhp_lock_release(true);
778
779 trace_cpuhp_enter(cpu, st->target, prev_state, cpuhp_kick_ap_work);
780 ret = cpuhp_kick_ap(st, st->target);
781 trace_cpuhp_exit(cpu, st->state, prev_state, ret);
782
783 return ret;
784}
785
786static struct smp_hotplug_thread cpuhp_threads = {
787 .store = &cpuhp_state.thread,
788 .create = &cpuhp_create,
789 .thread_should_run = cpuhp_should_run,
790 .thread_fn = cpuhp_thread_fun,
791 .thread_comm = "cpuhp/%u",
792 .selfparking = true,
793};
794
795void __init cpuhp_threads_init(void)
796{
797 BUG_ON(smpboot_register_percpu_thread(&cpuhp_threads));
798 kthread_unpark(this_cpu_read(cpuhp_state.thread));
799}
800
801#ifdef CONFIG_HOTPLUG_CPU
802/**
803 * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
804 * @cpu: a CPU id
805 *
806 * This function walks all processes, finds a valid mm struct for each one and
807 * then clears a corresponding bit in mm's cpumask. While this all sounds
808 * trivial, there are various non-obvious corner cases, which this function
809 * tries to solve in a safe manner.
810 *
811 * Also note that the function uses a somewhat relaxed locking scheme, so it may
812 * be called only for an already offlined CPU.
813 */
814void clear_tasks_mm_cpumask(int cpu)
815{
816 struct task_struct *p;
817
818 /*
819 * This function is called after the cpu is taken down and marked
820 * offline, so its not like new tasks will ever get this cpu set in
821 * their mm mask. -- Peter Zijlstra
822 * Thus, we may use rcu_read_lock() here, instead of grabbing
823 * full-fledged tasklist_lock.
824 */
825 WARN_ON(cpu_online(cpu));
826 rcu_read_lock();
827 for_each_process(p) {
828 struct task_struct *t;
829
830 /*
831 * Main thread might exit, but other threads may still have
832 * a valid mm. Find one.
833 */
834 t = find_lock_task_mm(p);
835 if (!t)
836 continue;
837 cpumask_clear_cpu(cpu, mm_cpumask(t->mm));
838 task_unlock(t);
839 }
840 rcu_read_unlock();
841}
842
843/* Take this CPU down. */
844static int take_cpu_down(void *_param)
845{
846 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
847 enum cpuhp_state target = max((int)st->target, CPUHP_AP_OFFLINE);
848 int err, cpu = smp_processor_id();
849 int ret;
850
851 /* Ensure this CPU doesn't handle any more interrupts. */
852 err = __cpu_disable();
853 if (err < 0)
854 return err;
855
856 /*
857 * We get here while we are in CPUHP_TEARDOWN_CPU state and we must not
858 * do this step again.
859 */
860 WARN_ON(st->state != CPUHP_TEARDOWN_CPU);
861 st->state--;
862 /* Invoke the former CPU_DYING callbacks */
863 for (; st->state > target; st->state--) {
864 ret = cpuhp_invoke_callback(cpu, st->state, false, NULL, NULL);
865 /*
866 * DYING must not fail!
867 */
868 WARN_ON_ONCE(ret);
869 }
870
871 /* Give up timekeeping duties */
872 tick_handover_do_timer();
873 /* Remove CPU from timer broadcasting */
874 tick_offline_cpu(cpu);
875 /* Park the stopper thread */
876 stop_machine_park(cpu);
877 return 0;
878}
879
880static int takedown_cpu(unsigned int cpu)
881{
882 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
883 int err;
884
885 /* Park the smpboot threads */
886 kthread_park(per_cpu_ptr(&cpuhp_state, cpu)->thread);
887
888 /*
889 * Prevent irq alloc/free while the dying cpu reorganizes the
890 * interrupt affinities.
891 */
892 irq_lock_sparse();
893
894 /*
895 * So now all preempt/rcu users must observe !cpu_active().
896 */
897 err = stop_machine_cpuslocked(take_cpu_down, NULL, cpumask_of(cpu));
898 if (err) {
899 /* CPU refused to die */
900 irq_unlock_sparse();
901 /* Unpark the hotplug thread so we can rollback there */
902 kthread_unpark(per_cpu_ptr(&cpuhp_state, cpu)->thread);
903 return err;
904 }
905 BUG_ON(cpu_online(cpu));
906
907 /*
908 * The teardown callback for CPUHP_AP_SCHED_STARTING will have removed
909 * all runnable tasks from the CPU, there's only the idle task left now
910 * that the migration thread is done doing the stop_machine thing.
911 *
912 * Wait for the stop thread to go away.
913 */
914 wait_for_ap_thread(st, false);
915 BUG_ON(st->state != CPUHP_AP_IDLE_DEAD);
916
917 /* Interrupts are moved away from the dying cpu, reenable alloc/free */
918 irq_unlock_sparse();
919
920 hotplug_cpu__broadcast_tick_pull(cpu);
921 /* This actually kills the CPU. */
922 __cpu_die(cpu);
923
924 tick_cleanup_dead_cpu(cpu);
925 rcutree_migrate_callbacks(cpu);
926 return 0;
927}
928
929static void cpuhp_complete_idle_dead(void *arg)
930{
931 struct cpuhp_cpu_state *st = arg;
932
933 complete_ap_thread(st, false);
934}
935
936void cpuhp_report_idle_dead(void)
937{
938 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
939
940 BUG_ON(st->state != CPUHP_AP_OFFLINE);
941 rcu_report_dead(smp_processor_id());
942 st->state = CPUHP_AP_IDLE_DEAD;
943 /*
944 * We cannot call complete after rcu_report_dead() so we delegate it
945 * to an online cpu.
946 */
947 smp_call_function_single(cpumask_first(cpu_online_mask),
948 cpuhp_complete_idle_dead, st, 0);
949}
950
951static void undo_cpu_down(unsigned int cpu, struct cpuhp_cpu_state *st)
952{
953 for (st->state++; st->state < st->target; st->state++)
954 cpuhp_invoke_callback(cpu, st->state, true, NULL, NULL);
955}
956
957static int cpuhp_down_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
958 enum cpuhp_state target)
959{
960 enum cpuhp_state prev_state = st->state;
961 int ret = 0;
962
963 for (; st->state > target; st->state--) {
964 ret = cpuhp_invoke_callback(cpu, st->state, false, NULL, NULL);
965 if (ret) {
966 st->target = prev_state;
967 if (st->state < prev_state)
968 undo_cpu_down(cpu, st);
969 break;
970 }
971 }
972 return ret;
973}
974
975/* Requires cpu_add_remove_lock to be held */
976static int __ref _cpu_down(unsigned int cpu, int tasks_frozen,
977 enum cpuhp_state target)
978{
979 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
980 int prev_state, ret = 0;
981
982 if (num_online_cpus() == 1)
983 return -EBUSY;
984
985 if (!cpu_present(cpu))
986 return -EINVAL;
987
988 cpus_write_lock();
989
990 cpuhp_tasks_frozen = tasks_frozen;
991
992 prev_state = cpuhp_set_state(st, target);
993 /*
994 * If the current CPU state is in the range of the AP hotplug thread,
995 * then we need to kick the thread.
996 */
997 if (st->state > CPUHP_TEARDOWN_CPU) {
998 st->target = max((int)target, CPUHP_TEARDOWN_CPU);
999 ret = cpuhp_kick_ap_work(cpu);
1000 /*
1001 * The AP side has done the error rollback already. Just
1002 * return the error code..
1003 */
1004 if (ret)
1005 goto out;
1006
1007 /*
1008 * We might have stopped still in the range of the AP hotplug
1009 * thread. Nothing to do anymore.
1010 */
1011 if (st->state > CPUHP_TEARDOWN_CPU)
1012 goto out;
1013
1014 st->target = target;
1015 }
1016 /*
1017 * The AP brought itself down to CPUHP_TEARDOWN_CPU. So we need
1018 * to do the further cleanups.
1019 */
1020 ret = cpuhp_down_callbacks(cpu, st, target);
1021 if (ret && st->state == CPUHP_TEARDOWN_CPU && st->state < prev_state) {
1022 cpuhp_reset_state(st, prev_state);
1023 __cpuhp_kick_ap(st);
1024 }
1025
1026out:
1027 cpus_write_unlock();
1028 /*
1029 * Do post unplug cleanup. This is still protected against
1030 * concurrent CPU hotplug via cpu_add_remove_lock.
1031 */
1032 lockup_detector_cleanup();
1033 arch_smt_update();
1034 return ret;
1035}
1036
1037static int cpu_down_maps_locked(unsigned int cpu, enum cpuhp_state target)
1038{
1039 if (cpu_hotplug_disabled)
1040 return -EBUSY;
1041 return _cpu_down(cpu, 0, target);
1042}
1043
1044static int do_cpu_down(unsigned int cpu, enum cpuhp_state target)
1045{
1046 int err;
1047
1048 cpu_maps_update_begin();
1049 err = cpu_down_maps_locked(cpu, target);
1050 cpu_maps_update_done();
1051 return err;
1052}
1053
1054int cpu_down(unsigned int cpu)
1055{
1056 return do_cpu_down(cpu, CPUHP_OFFLINE);
1057}
1058EXPORT_SYMBOL(cpu_down);
1059
1060#else
1061#define takedown_cpu NULL
1062#endif /*CONFIG_HOTPLUG_CPU*/
1063
1064/**
1065 * notify_cpu_starting(cpu) - Invoke the callbacks on the starting CPU
1066 * @cpu: cpu that just started
1067 *
1068 * It must be called by the arch code on the new cpu, before the new cpu
1069 * enables interrupts and before the "boot" cpu returns from __cpu_up().
1070 */
1071void notify_cpu_starting(unsigned int cpu)
1072{
1073 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1074 enum cpuhp_state target = min((int)st->target, CPUHP_AP_ONLINE);
1075 int ret;
1076
1077 rcu_cpu_starting(cpu); /* Enables RCU usage on this CPU. */
1078 cpumask_set_cpu(cpu, &cpus_booted_once_mask);
1079 while (st->state < target) {
1080 st->state++;
1081 ret = cpuhp_invoke_callback(cpu, st->state, true, NULL, NULL);
1082 /*
1083 * STARTING must not fail!
1084 */
1085 WARN_ON_ONCE(ret);
1086 }
1087}
1088
1089/*
1090 * Called from the idle task. Wake up the controlling task which brings the
1091 * hotplug thread of the upcoming CPU up and then delegates the rest of the
1092 * online bringup to the hotplug thread.
1093 */
1094void cpuhp_online_idle(enum cpuhp_state state)
1095{
1096 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
1097
1098 /* Happens for the boot cpu */
1099 if (state != CPUHP_AP_ONLINE_IDLE)
1100 return;
1101
1102 /*
1103 * Unpart the stopper thread before we start the idle loop (and start
1104 * scheduling); this ensures the stopper task is always available.
1105 */
1106 stop_machine_unpark(smp_processor_id());
1107
1108 st->state = CPUHP_AP_ONLINE_IDLE;
1109 complete_ap_thread(st, true);
1110}
1111
1112/* Requires cpu_add_remove_lock to be held */
1113static int _cpu_up(unsigned int cpu, int tasks_frozen, enum cpuhp_state target)
1114{
1115 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1116 struct task_struct *idle;
1117 int ret = 0;
1118
1119 cpus_write_lock();
1120
1121 if (!cpu_present(cpu)) {
1122 ret = -EINVAL;
1123 goto out;
1124 }
1125
1126 /*
1127 * The caller of do_cpu_up might have raced with another
1128 * caller. Ignore it for now.
1129 */
1130 if (st->state >= target)
1131 goto out;
1132
1133 if (st->state == CPUHP_OFFLINE) {
1134 /* Let it fail before we try to bring the cpu up */
1135 idle = idle_thread_get(cpu);
1136 if (IS_ERR(idle)) {
1137 ret = PTR_ERR(idle);
1138 goto out;
1139 }
1140 }
1141
1142 cpuhp_tasks_frozen = tasks_frozen;
1143
1144 cpuhp_set_state(st, target);
1145 /*
1146 * If the current CPU state is in the range of the AP hotplug thread,
1147 * then we need to kick the thread once more.
1148 */
1149 if (st->state > CPUHP_BRINGUP_CPU) {
1150 ret = cpuhp_kick_ap_work(cpu);
1151 /*
1152 * The AP side has done the error rollback already. Just
1153 * return the error code..
1154 */
1155 if (ret)
1156 goto out;
1157 }
1158
1159 /*
1160 * Try to reach the target state. We max out on the BP at
1161 * CPUHP_BRINGUP_CPU. After that the AP hotplug thread is
1162 * responsible for bringing it up to the target state.
1163 */
1164 target = min((int)target, CPUHP_BRINGUP_CPU);
1165 ret = cpuhp_up_callbacks(cpu, st, target);
1166out:
1167 cpus_write_unlock();
1168 arch_smt_update();
1169 return ret;
1170}
1171
1172static int do_cpu_up(unsigned int cpu, enum cpuhp_state target)
1173{
1174 int err = 0;
1175
1176 if (!cpu_possible(cpu)) {
1177 pr_err("can't online cpu %d because it is not configured as may-hotadd at boot time\n",
1178 cpu);
1179#if defined(CONFIG_IA64)
1180 pr_err("please check additional_cpus= boot parameter\n");
1181#endif
1182 return -EINVAL;
1183 }
1184
1185 err = try_online_node(cpu_to_node(cpu));
1186 if (err)
1187 return err;
1188
1189 cpu_maps_update_begin();
1190
1191 if (cpu_hotplug_disabled) {
1192 err = -EBUSY;
1193 goto out;
1194 }
1195 if (!cpu_smt_allowed(cpu)) {
1196 err = -EPERM;
1197 goto out;
1198 }
1199
1200 err = _cpu_up(cpu, 0, target);
1201out:
1202 cpu_maps_update_done();
1203 return err;
1204}
1205
1206int cpu_up(unsigned int cpu)
1207{
1208 return do_cpu_up(cpu, CPUHP_ONLINE);
1209}
1210EXPORT_SYMBOL_GPL(cpu_up);
1211
1212#ifdef CONFIG_PM_SLEEP_SMP
1213static cpumask_var_t frozen_cpus;
1214
1215int freeze_secondary_cpus(int primary)
1216{
1217 int cpu, error = 0;
1218
1219 cpu_maps_update_begin();
1220 if (primary == -1) {
1221 primary = cpumask_first(cpu_online_mask);
1222 if (!housekeeping_cpu(primary, HK_FLAG_TIMER))
1223 primary = housekeeping_any_cpu(HK_FLAG_TIMER);
1224 } else {
1225 if (!cpu_online(primary))
1226 primary = cpumask_first(cpu_online_mask);
1227 }
1228
1229 /*
1230 * We take down all of the non-boot CPUs in one shot to avoid races
1231 * with the userspace trying to use the CPU hotplug at the same time
1232 */
1233 cpumask_clear(frozen_cpus);
1234
1235 pr_info("Disabling non-boot CPUs ...\n");
1236 for_each_online_cpu(cpu) {
1237 if (cpu == primary)
1238 continue;
1239
1240 if (pm_wakeup_pending()) {
1241 pr_info("Wakeup pending. Abort CPU freeze\n");
1242 error = -EBUSY;
1243 break;
1244 }
1245
1246 trace_suspend_resume(TPS("CPU_OFF"), cpu, true);
1247 error = _cpu_down(cpu, 1, CPUHP_OFFLINE);
1248 trace_suspend_resume(TPS("CPU_OFF"), cpu, false);
1249 if (!error)
1250 cpumask_set_cpu(cpu, frozen_cpus);
1251 else {
1252 pr_err("Error taking CPU%d down: %d\n", cpu, error);
1253 break;
1254 }
1255 }
1256
1257 if (!error)
1258 BUG_ON(num_online_cpus() > 1);
1259 else
1260 pr_err("Non-boot CPUs are not disabled\n");
1261
1262 /*
1263 * Make sure the CPUs won't be enabled by someone else. We need to do
1264 * this even in case of failure as all disable_nonboot_cpus() users are
1265 * supposed to do enable_nonboot_cpus() on the failure path.
1266 */
1267 cpu_hotplug_disabled++;
1268
1269 cpu_maps_update_done();
1270 return error;
1271}
1272
1273void __weak arch_enable_nonboot_cpus_begin(void)
1274{
1275}
1276
1277void __weak arch_enable_nonboot_cpus_end(void)
1278{
1279}
1280
1281void enable_nonboot_cpus(void)
1282{
1283 int cpu, error;
1284
1285 /* Allow everyone to use the CPU hotplug again */
1286 cpu_maps_update_begin();
1287 __cpu_hotplug_enable();
1288 if (cpumask_empty(frozen_cpus))
1289 goto out;
1290
1291 pr_info("Enabling non-boot CPUs ...\n");
1292
1293 arch_enable_nonboot_cpus_begin();
1294
1295 for_each_cpu(cpu, frozen_cpus) {
1296 trace_suspend_resume(TPS("CPU_ON"), cpu, true);
1297 error = _cpu_up(cpu, 1, CPUHP_ONLINE);
1298 trace_suspend_resume(TPS("CPU_ON"), cpu, false);
1299 if (!error) {
1300 pr_info("CPU%d is up\n", cpu);
1301 continue;
1302 }
1303 pr_warn("Error taking CPU%d up: %d\n", cpu, error);
1304 }
1305
1306 arch_enable_nonboot_cpus_end();
1307
1308 cpumask_clear(frozen_cpus);
1309out:
1310 cpu_maps_update_done();
1311}
1312
1313static int __init alloc_frozen_cpus(void)
1314{
1315 if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
1316 return -ENOMEM;
1317 return 0;
1318}
1319core_initcall(alloc_frozen_cpus);
1320
1321/*
1322 * When callbacks for CPU hotplug notifications are being executed, we must
1323 * ensure that the state of the system with respect to the tasks being frozen
1324 * or not, as reported by the notification, remains unchanged *throughout the
1325 * duration* of the execution of the callbacks.
1326 * Hence we need to prevent the freezer from racing with regular CPU hotplug.
1327 *
1328 * This synchronization is implemented by mutually excluding regular CPU
1329 * hotplug and Suspend/Hibernate call paths by hooking onto the Suspend/
1330 * Hibernate notifications.
1331 */
1332static int
1333cpu_hotplug_pm_callback(struct notifier_block *nb,
1334 unsigned long action, void *ptr)
1335{
1336 switch (action) {
1337
1338 case PM_SUSPEND_PREPARE:
1339 case PM_HIBERNATION_PREPARE:
1340 cpu_hotplug_disable();
1341 break;
1342
1343 case PM_POST_SUSPEND:
1344 case PM_POST_HIBERNATION:
1345 cpu_hotplug_enable();
1346 break;
1347
1348 default:
1349 return NOTIFY_DONE;
1350 }
1351
1352 return NOTIFY_OK;
1353}
1354
1355
1356static int __init cpu_hotplug_pm_sync_init(void)
1357{
1358 /*
1359 * cpu_hotplug_pm_callback has higher priority than x86
1360 * bsp_pm_callback which depends on cpu_hotplug_pm_callback
1361 * to disable cpu hotplug to avoid cpu hotplug race.
1362 */
1363 pm_notifier(cpu_hotplug_pm_callback, 0);
1364 return 0;
1365}
1366core_initcall(cpu_hotplug_pm_sync_init);
1367
1368#endif /* CONFIG_PM_SLEEP_SMP */
1369
1370int __boot_cpu_id;
1371
1372#endif /* CONFIG_SMP */
1373
1374/* Boot processor state steps */
1375static struct cpuhp_step cpuhp_hp_states[] = {
1376 [CPUHP_OFFLINE] = {
1377 .name = "offline",
1378 .startup.single = NULL,
1379 .teardown.single = NULL,
1380 },
1381#ifdef CONFIG_SMP
1382 [CPUHP_CREATE_THREADS]= {
1383 .name = "threads:prepare",
1384 .startup.single = smpboot_create_threads,
1385 .teardown.single = NULL,
1386 .cant_stop = true,
1387 },
1388 [CPUHP_PERF_PREPARE] = {
1389 .name = "perf:prepare",
1390 .startup.single = perf_event_init_cpu,
1391 .teardown.single = perf_event_exit_cpu,
1392 },
1393 [CPUHP_WORKQUEUE_PREP] = {
1394 .name = "workqueue:prepare",
1395 .startup.single = workqueue_prepare_cpu,
1396 .teardown.single = NULL,
1397 },
1398 [CPUHP_HRTIMERS_PREPARE] = {
1399 .name = "hrtimers:prepare",
1400 .startup.single = hrtimers_prepare_cpu,
1401 .teardown.single = hrtimers_dead_cpu,
1402 },
1403 [CPUHP_SMPCFD_PREPARE] = {
1404 .name = "smpcfd:prepare",
1405 .startup.single = smpcfd_prepare_cpu,
1406 .teardown.single = smpcfd_dead_cpu,
1407 },
1408 [CPUHP_RELAY_PREPARE] = {
1409 .name = "relay:prepare",
1410 .startup.single = relay_prepare_cpu,
1411 .teardown.single = NULL,
1412 },
1413 [CPUHP_SLAB_PREPARE] = {
1414 .name = "slab:prepare",
1415 .startup.single = slab_prepare_cpu,
1416 .teardown.single = slab_dead_cpu,
1417 },
1418 [CPUHP_RCUTREE_PREP] = {
1419 .name = "RCU/tree:prepare",
1420 .startup.single = rcutree_prepare_cpu,
1421 .teardown.single = rcutree_dead_cpu,
1422 },
1423 /*
1424 * On the tear-down path, timers_dead_cpu() must be invoked
1425 * before blk_mq_queue_reinit_notify() from notify_dead(),
1426 * otherwise a RCU stall occurs.
1427 */
1428 [CPUHP_TIMERS_PREPARE] = {
1429 .name = "timers:prepare",
1430 .startup.single = timers_prepare_cpu,
1431 .teardown.single = timers_dead_cpu,
1432 },
1433 /* Kicks the plugged cpu into life */
1434 [CPUHP_BRINGUP_CPU] = {
1435 .name = "cpu:bringup",
1436 .startup.single = bringup_cpu,
1437 .teardown.single = NULL,
1438 .cant_stop = true,
1439 },
1440 /* Final state before CPU kills itself */
1441 [CPUHP_AP_IDLE_DEAD] = {
1442 .name = "idle:dead",
1443 },
1444 /*
1445 * Last state before CPU enters the idle loop to die. Transient state
1446 * for synchronization.
1447 */
1448 [CPUHP_AP_OFFLINE] = {
1449 .name = "ap:offline",
1450 .cant_stop = true,
1451 },
1452 /* First state is scheduler control. Interrupts are disabled */
1453 [CPUHP_AP_SCHED_STARTING] = {
1454 .name = "sched:starting",
1455 .startup.single = sched_cpu_starting,
1456 .teardown.single = sched_cpu_dying,
1457 },
1458 [CPUHP_AP_RCUTREE_DYING] = {
1459 .name = "RCU/tree:dying",
1460 .startup.single = NULL,
1461 .teardown.single = rcutree_dying_cpu,
1462 },
1463 [CPUHP_AP_SMPCFD_DYING] = {
1464 .name = "smpcfd:dying",
1465 .startup.single = NULL,
1466 .teardown.single = smpcfd_dying_cpu,
1467 },
1468 /* Entry state on starting. Interrupts enabled from here on. Transient
1469 * state for synchronsization */
1470 [CPUHP_AP_ONLINE] = {
1471 .name = "ap:online",
1472 },
1473 /*
1474 * Handled on controll processor until the plugged processor manages
1475 * this itself.
1476 */
1477 [CPUHP_TEARDOWN_CPU] = {
1478 .name = "cpu:teardown",
1479 .startup.single = NULL,
1480 .teardown.single = takedown_cpu,
1481 .cant_stop = true,
1482 },
1483 /* Handle smpboot threads park/unpark */
1484 [CPUHP_AP_SMPBOOT_THREADS] = {
1485 .name = "smpboot/threads:online",
1486 .startup.single = smpboot_unpark_threads,
1487 .teardown.single = smpboot_park_threads,
1488 },
1489 [CPUHP_AP_IRQ_AFFINITY_ONLINE] = {
1490 .name = "irq/affinity:online",
1491 .startup.single = irq_affinity_online_cpu,
1492 .teardown.single = NULL,
1493 },
1494 [CPUHP_AP_PERF_ONLINE] = {
1495 .name = "perf:online",
1496 .startup.single = perf_event_init_cpu,
1497 .teardown.single = perf_event_exit_cpu,
1498 },
1499 [CPUHP_AP_WATCHDOG_ONLINE] = {
1500 .name = "lockup_detector:online",
1501 .startup.single = lockup_detector_online_cpu,
1502 .teardown.single = lockup_detector_offline_cpu,
1503 },
1504 [CPUHP_AP_WORKQUEUE_ONLINE] = {
1505 .name = "workqueue:online",
1506 .startup.single = workqueue_online_cpu,
1507 .teardown.single = workqueue_offline_cpu,
1508 },
1509 [CPUHP_AP_RCUTREE_ONLINE] = {
1510 .name = "RCU/tree:online",
1511 .startup.single = rcutree_online_cpu,
1512 .teardown.single = rcutree_offline_cpu,
1513 },
1514#endif
1515 /*
1516 * The dynamically registered state space is here
1517 */
1518
1519#ifdef CONFIG_SMP
1520 /* Last state is scheduler control setting the cpu active */
1521 [CPUHP_AP_ACTIVE] = {
1522 .name = "sched:active",
1523 .startup.single = sched_cpu_activate,
1524 .teardown.single = sched_cpu_deactivate,
1525 },
1526#endif
1527
1528 /* CPU is fully up and running. */
1529 [CPUHP_ONLINE] = {
1530 .name = "online",
1531 .startup.single = NULL,
1532 .teardown.single = NULL,
1533 },
1534};
1535
1536/* Sanity check for callbacks */
1537static int cpuhp_cb_check(enum cpuhp_state state)
1538{
1539 if (state <= CPUHP_OFFLINE || state >= CPUHP_ONLINE)
1540 return -EINVAL;
1541 return 0;
1542}
1543
1544/*
1545 * Returns a free for dynamic slot assignment of the Online state. The states
1546 * are protected by the cpuhp_slot_states mutex and an empty slot is identified
1547 * by having no name assigned.
1548 */
1549static int cpuhp_reserve_state(enum cpuhp_state state)
1550{
1551 enum cpuhp_state i, end;
1552 struct cpuhp_step *step;
1553
1554 switch (state) {
1555 case CPUHP_AP_ONLINE_DYN:
1556 step = cpuhp_hp_states + CPUHP_AP_ONLINE_DYN;
1557 end = CPUHP_AP_ONLINE_DYN_END;
1558 break;
1559 case CPUHP_BP_PREPARE_DYN:
1560 step = cpuhp_hp_states + CPUHP_BP_PREPARE_DYN;
1561 end = CPUHP_BP_PREPARE_DYN_END;
1562 break;
1563 default:
1564 return -EINVAL;
1565 }
1566
1567 for (i = state; i <= end; i++, step++) {
1568 if (!step->name)
1569 return i;
1570 }
1571 WARN(1, "No more dynamic states available for CPU hotplug\n");
1572 return -ENOSPC;
1573}
1574
1575static int cpuhp_store_callbacks(enum cpuhp_state state, const char *name,
1576 int (*startup)(unsigned int cpu),
1577 int (*teardown)(unsigned int cpu),
1578 bool multi_instance)
1579{
1580 /* (Un)Install the callbacks for further cpu hotplug operations */
1581 struct cpuhp_step *sp;
1582 int ret = 0;
1583
1584 /*
1585 * If name is NULL, then the state gets removed.
1586 *
1587 * CPUHP_AP_ONLINE_DYN and CPUHP_BP_PREPARE_DYN are handed out on
1588 * the first allocation from these dynamic ranges, so the removal
1589 * would trigger a new allocation and clear the wrong (already
1590 * empty) state, leaving the callbacks of the to be cleared state
1591 * dangling, which causes wreckage on the next hotplug operation.
1592 */
1593 if (name && (state == CPUHP_AP_ONLINE_DYN ||
1594 state == CPUHP_BP_PREPARE_DYN)) {
1595 ret = cpuhp_reserve_state(state);
1596 if (ret < 0)
1597 return ret;
1598 state = ret;
1599 }
1600 sp = cpuhp_get_step(state);
1601 if (name && sp->name)
1602 return -EBUSY;
1603
1604 sp->startup.single = startup;
1605 sp->teardown.single = teardown;
1606 sp->name = name;
1607 sp->multi_instance = multi_instance;
1608 INIT_HLIST_HEAD(&sp->list);
1609 return ret;
1610}
1611
1612static void *cpuhp_get_teardown_cb(enum cpuhp_state state)
1613{
1614 return cpuhp_get_step(state)->teardown.single;
1615}
1616
1617/*
1618 * Call the startup/teardown function for a step either on the AP or
1619 * on the current CPU.
1620 */
1621static int cpuhp_issue_call(int cpu, enum cpuhp_state state, bool bringup,
1622 struct hlist_node *node)
1623{
1624 struct cpuhp_step *sp = cpuhp_get_step(state);
1625 int ret;
1626
1627 /*
1628 * If there's nothing to do, we done.
1629 * Relies on the union for multi_instance.
1630 */
1631 if ((bringup && !sp->startup.single) ||
1632 (!bringup && !sp->teardown.single))
1633 return 0;
1634 /*
1635 * The non AP bound callbacks can fail on bringup. On teardown
1636 * e.g. module removal we crash for now.
1637 */
1638#ifdef CONFIG_SMP
1639 if (cpuhp_is_ap_state(state))
1640 ret = cpuhp_invoke_ap_callback(cpu, state, bringup, node);
1641 else
1642 ret = cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
1643#else
1644 ret = cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
1645#endif
1646 BUG_ON(ret && !bringup);
1647 return ret;
1648}
1649
1650/*
1651 * Called from __cpuhp_setup_state on a recoverable failure.
1652 *
1653 * Note: The teardown callbacks for rollback are not allowed to fail!
1654 */
1655static void cpuhp_rollback_install(int failedcpu, enum cpuhp_state state,
1656 struct hlist_node *node)
1657{
1658 int cpu;
1659
1660 /* Roll back the already executed steps on the other cpus */
1661 for_each_present_cpu(cpu) {
1662 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1663 int cpustate = st->state;
1664
1665 if (cpu >= failedcpu)
1666 break;
1667
1668 /* Did we invoke the startup call on that cpu ? */
1669 if (cpustate >= state)
1670 cpuhp_issue_call(cpu, state, false, node);
1671 }
1672}
1673
1674int __cpuhp_state_add_instance_cpuslocked(enum cpuhp_state state,
1675 struct hlist_node *node,
1676 bool invoke)
1677{
1678 struct cpuhp_step *sp;
1679 int cpu;
1680 int ret;
1681
1682 lockdep_assert_cpus_held();
1683
1684 sp = cpuhp_get_step(state);
1685 if (sp->multi_instance == false)
1686 return -EINVAL;
1687
1688 mutex_lock(&cpuhp_state_mutex);
1689
1690 if (!invoke || !sp->startup.multi)
1691 goto add_node;
1692
1693 /*
1694 * Try to call the startup callback for each present cpu
1695 * depending on the hotplug state of the cpu.
1696 */
1697 for_each_present_cpu(cpu) {
1698 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1699 int cpustate = st->state;
1700
1701 if (cpustate < state)
1702 continue;
1703
1704 ret = cpuhp_issue_call(cpu, state, true, node);
1705 if (ret) {
1706 if (sp->teardown.multi)
1707 cpuhp_rollback_install(cpu, state, node);
1708 goto unlock;
1709 }
1710 }
1711add_node:
1712 ret = 0;
1713 hlist_add_head(node, &sp->list);
1714unlock:
1715 mutex_unlock(&cpuhp_state_mutex);
1716 return ret;
1717}
1718
1719int __cpuhp_state_add_instance(enum cpuhp_state state, struct hlist_node *node,
1720 bool invoke)
1721{
1722 int ret;
1723
1724 cpus_read_lock();
1725 ret = __cpuhp_state_add_instance_cpuslocked(state, node, invoke);
1726 cpus_read_unlock();
1727 return ret;
1728}
1729EXPORT_SYMBOL_GPL(__cpuhp_state_add_instance);
1730
1731/**
1732 * __cpuhp_setup_state_cpuslocked - Setup the callbacks for an hotplug machine state
1733 * @state: The state to setup
1734 * @invoke: If true, the startup function is invoked for cpus where
1735 * cpu state >= @state
1736 * @startup: startup callback function
1737 * @teardown: teardown callback function
1738 * @multi_instance: State is set up for multiple instances which get
1739 * added afterwards.
1740 *
1741 * The caller needs to hold cpus read locked while calling this function.
1742 * Returns:
1743 * On success:
1744 * Positive state number if @state is CPUHP_AP_ONLINE_DYN
1745 * 0 for all other states
1746 * On failure: proper (negative) error code
1747 */
1748int __cpuhp_setup_state_cpuslocked(enum cpuhp_state state,
1749 const char *name, bool invoke,
1750 int (*startup)(unsigned int cpu),
1751 int (*teardown)(unsigned int cpu),
1752 bool multi_instance)
1753{
1754 int cpu, ret = 0;
1755 bool dynstate;
1756
1757 lockdep_assert_cpus_held();
1758
1759 if (cpuhp_cb_check(state) || !name)
1760 return -EINVAL;
1761
1762 mutex_lock(&cpuhp_state_mutex);
1763
1764 ret = cpuhp_store_callbacks(state, name, startup, teardown,
1765 multi_instance);
1766
1767 dynstate = state == CPUHP_AP_ONLINE_DYN;
1768 if (ret > 0 && dynstate) {
1769 state = ret;
1770 ret = 0;
1771 }
1772
1773 if (ret || !invoke || !startup)
1774 goto out;
1775
1776 /*
1777 * Try to call the startup callback for each present cpu
1778 * depending on the hotplug state of the cpu.
1779 */
1780 for_each_present_cpu(cpu) {
1781 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1782 int cpustate = st->state;
1783
1784 if (cpustate < state)
1785 continue;
1786
1787 ret = cpuhp_issue_call(cpu, state, true, NULL);
1788 if (ret) {
1789 if (teardown)
1790 cpuhp_rollback_install(cpu, state, NULL);
1791 cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
1792 goto out;
1793 }
1794 }
1795out:
1796 mutex_unlock(&cpuhp_state_mutex);
1797 /*
1798 * If the requested state is CPUHP_AP_ONLINE_DYN, return the
1799 * dynamically allocated state in case of success.
1800 */
1801 if (!ret && dynstate)
1802 return state;
1803 return ret;
1804}
1805EXPORT_SYMBOL(__cpuhp_setup_state_cpuslocked);
1806
1807int __cpuhp_setup_state(enum cpuhp_state state,
1808 const char *name, bool invoke,
1809 int (*startup)(unsigned int cpu),
1810 int (*teardown)(unsigned int cpu),
1811 bool multi_instance)
1812{
1813 int ret;
1814
1815 cpus_read_lock();
1816 ret = __cpuhp_setup_state_cpuslocked(state, name, invoke, startup,
1817 teardown, multi_instance);
1818 cpus_read_unlock();
1819 return ret;
1820}
1821EXPORT_SYMBOL(__cpuhp_setup_state);
1822
1823int __cpuhp_state_remove_instance(enum cpuhp_state state,
1824 struct hlist_node *node, bool invoke)
1825{
1826 struct cpuhp_step *sp = cpuhp_get_step(state);
1827 int cpu;
1828
1829 BUG_ON(cpuhp_cb_check(state));
1830
1831 if (!sp->multi_instance)
1832 return -EINVAL;
1833
1834 cpus_read_lock();
1835 mutex_lock(&cpuhp_state_mutex);
1836
1837 if (!invoke || !cpuhp_get_teardown_cb(state))
1838 goto remove;
1839 /*
1840 * Call the teardown callback for each present cpu depending
1841 * on the hotplug state of the cpu. This function is not
1842 * allowed to fail currently!
1843 */
1844 for_each_present_cpu(cpu) {
1845 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1846 int cpustate = st->state;
1847
1848 if (cpustate >= state)
1849 cpuhp_issue_call(cpu, state, false, node);
1850 }
1851
1852remove:
1853 hlist_del(node);
1854 mutex_unlock(&cpuhp_state_mutex);
1855 cpus_read_unlock();
1856
1857 return 0;
1858}
1859EXPORT_SYMBOL_GPL(__cpuhp_state_remove_instance);
1860
1861/**
1862 * __cpuhp_remove_state_cpuslocked - Remove the callbacks for an hotplug machine state
1863 * @state: The state to remove
1864 * @invoke: If true, the teardown function is invoked for cpus where
1865 * cpu state >= @state
1866 *
1867 * The caller needs to hold cpus read locked while calling this function.
1868 * The teardown callback is currently not allowed to fail. Think
1869 * about module removal!
1870 */
1871void __cpuhp_remove_state_cpuslocked(enum cpuhp_state state, bool invoke)
1872{
1873 struct cpuhp_step *sp = cpuhp_get_step(state);
1874 int cpu;
1875
1876 BUG_ON(cpuhp_cb_check(state));
1877
1878 lockdep_assert_cpus_held();
1879
1880 mutex_lock(&cpuhp_state_mutex);
1881 if (sp->multi_instance) {
1882 WARN(!hlist_empty(&sp->list),
1883 "Error: Removing state %d which has instances left.\n",
1884 state);
1885 goto remove;
1886 }
1887
1888 if (!invoke || !cpuhp_get_teardown_cb(state))
1889 goto remove;
1890
1891 /*
1892 * Call the teardown callback for each present cpu depending
1893 * on the hotplug state of the cpu. This function is not
1894 * allowed to fail currently!
1895 */
1896 for_each_present_cpu(cpu) {
1897 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1898 int cpustate = st->state;
1899
1900 if (cpustate >= state)
1901 cpuhp_issue_call(cpu, state, false, NULL);
1902 }
1903remove:
1904 cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
1905 mutex_unlock(&cpuhp_state_mutex);
1906}
1907EXPORT_SYMBOL(__cpuhp_remove_state_cpuslocked);
1908
1909void __cpuhp_remove_state(enum cpuhp_state state, bool invoke)
1910{
1911 cpus_read_lock();
1912 __cpuhp_remove_state_cpuslocked(state, invoke);
1913 cpus_read_unlock();
1914}
1915EXPORT_SYMBOL(__cpuhp_remove_state);
1916
1917#ifdef CONFIG_HOTPLUG_SMT
1918static void cpuhp_offline_cpu_device(unsigned int cpu)
1919{
1920 struct device *dev = get_cpu_device(cpu);
1921
1922 dev->offline = true;
1923 /* Tell user space about the state change */
1924 kobject_uevent(&dev->kobj, KOBJ_OFFLINE);
1925}
1926
1927static void cpuhp_online_cpu_device(unsigned int cpu)
1928{
1929 struct device *dev = get_cpu_device(cpu);
1930
1931 dev->offline = false;
1932 /* Tell user space about the state change */
1933 kobject_uevent(&dev->kobj, KOBJ_ONLINE);
1934}
1935
1936int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval)
1937{
1938 int cpu, ret = 0;
1939
1940 cpu_maps_update_begin();
1941 for_each_online_cpu(cpu) {
1942 if (topology_is_primary_thread(cpu))
1943 continue;
1944 ret = cpu_down_maps_locked(cpu, CPUHP_OFFLINE);
1945 if (ret)
1946 break;
1947 /*
1948 * As this needs to hold the cpu maps lock it's impossible
1949 * to call device_offline() because that ends up calling
1950 * cpu_down() which takes cpu maps lock. cpu maps lock
1951 * needs to be held as this might race against in kernel
1952 * abusers of the hotplug machinery (thermal management).
1953 *
1954 * So nothing would update device:offline state. That would
1955 * leave the sysfs entry stale and prevent onlining after
1956 * smt control has been changed to 'off' again. This is
1957 * called under the sysfs hotplug lock, so it is properly
1958 * serialized against the regular offline usage.
1959 */
1960 cpuhp_offline_cpu_device(cpu);
1961 }
1962 if (!ret)
1963 cpu_smt_control = ctrlval;
1964 cpu_maps_update_done();
1965 return ret;
1966}
1967
1968int cpuhp_smt_enable(void)
1969{
1970 int cpu, ret = 0;
1971
1972 cpu_maps_update_begin();
1973 cpu_smt_control = CPU_SMT_ENABLED;
1974 for_each_present_cpu(cpu) {
1975 /* Skip online CPUs and CPUs on offline nodes */
1976 if (cpu_online(cpu) || !node_online(cpu_to_node(cpu)))
1977 continue;
1978 ret = _cpu_up(cpu, 0, CPUHP_ONLINE);
1979 if (ret)
1980 break;
1981 /* See comment in cpuhp_smt_disable() */
1982 cpuhp_online_cpu_device(cpu);
1983 }
1984 cpu_maps_update_done();
1985 return ret;
1986}
1987#endif
1988
1989#if defined(CONFIG_SYSFS) && defined(CONFIG_HOTPLUG_CPU)
1990static ssize_t show_cpuhp_state(struct device *dev,
1991 struct device_attribute *attr, char *buf)
1992{
1993 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
1994
1995 return sprintf(buf, "%d\n", st->state);
1996}
1997static DEVICE_ATTR(state, 0444, show_cpuhp_state, NULL);
1998
1999static ssize_t write_cpuhp_target(struct device *dev,
2000 struct device_attribute *attr,
2001 const char *buf, size_t count)
2002{
2003 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2004 struct cpuhp_step *sp;
2005 int target, ret;
2006
2007 ret = kstrtoint(buf, 10, &target);
2008 if (ret)
2009 return ret;
2010
2011#ifdef CONFIG_CPU_HOTPLUG_STATE_CONTROL
2012 if (target < CPUHP_OFFLINE || target > CPUHP_ONLINE)
2013 return -EINVAL;
2014#else
2015 if (target != CPUHP_OFFLINE && target != CPUHP_ONLINE)
2016 return -EINVAL;
2017#endif
2018
2019 ret = lock_device_hotplug_sysfs();
2020 if (ret)
2021 return ret;
2022
2023 mutex_lock(&cpuhp_state_mutex);
2024 sp = cpuhp_get_step(target);
2025 ret = !sp->name || sp->cant_stop ? -EINVAL : 0;
2026 mutex_unlock(&cpuhp_state_mutex);
2027 if (ret)
2028 goto out;
2029
2030 if (st->state < target)
2031 ret = do_cpu_up(dev->id, target);
2032 else
2033 ret = do_cpu_down(dev->id, target);
2034out:
2035 unlock_device_hotplug();
2036 return ret ? ret : count;
2037}
2038
2039static ssize_t show_cpuhp_target(struct device *dev,
2040 struct device_attribute *attr, char *buf)
2041{
2042 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2043
2044 return sprintf(buf, "%d\n", st->target);
2045}
2046static DEVICE_ATTR(target, 0644, show_cpuhp_target, write_cpuhp_target);
2047
2048
2049static ssize_t write_cpuhp_fail(struct device *dev,
2050 struct device_attribute *attr,
2051 const char *buf, size_t count)
2052{
2053 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2054 struct cpuhp_step *sp;
2055 int fail, ret;
2056
2057 ret = kstrtoint(buf, 10, &fail);
2058 if (ret)
2059 return ret;
2060
2061 if (fail < CPUHP_OFFLINE || fail > CPUHP_ONLINE)
2062 return -EINVAL;
2063
2064 /*
2065 * Cannot fail STARTING/DYING callbacks.
2066 */
2067 if (cpuhp_is_atomic_state(fail))
2068 return -EINVAL;
2069
2070 /*
2071 * Cannot fail anything that doesn't have callbacks.
2072 */
2073 mutex_lock(&cpuhp_state_mutex);
2074 sp = cpuhp_get_step(fail);
2075 if (!sp->startup.single && !sp->teardown.single)
2076 ret = -EINVAL;
2077 mutex_unlock(&cpuhp_state_mutex);
2078 if (ret)
2079 return ret;
2080
2081 st->fail = fail;
2082
2083 return count;
2084}
2085
2086static ssize_t show_cpuhp_fail(struct device *dev,
2087 struct device_attribute *attr, char *buf)
2088{
2089 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2090
2091 return sprintf(buf, "%d\n", st->fail);
2092}
2093
2094static DEVICE_ATTR(fail, 0644, show_cpuhp_fail, write_cpuhp_fail);
2095
2096static struct attribute *cpuhp_cpu_attrs[] = {
2097 &dev_attr_state.attr,
2098 &dev_attr_target.attr,
2099 &dev_attr_fail.attr,
2100 NULL
2101};
2102
2103static const struct attribute_group cpuhp_cpu_attr_group = {
2104 .attrs = cpuhp_cpu_attrs,
2105 .name = "hotplug",
2106 NULL
2107};
2108
2109static ssize_t show_cpuhp_states(struct device *dev,
2110 struct device_attribute *attr, char *buf)
2111{
2112 ssize_t cur, res = 0;
2113 int i;
2114
2115 mutex_lock(&cpuhp_state_mutex);
2116 for (i = CPUHP_OFFLINE; i <= CPUHP_ONLINE; i++) {
2117 struct cpuhp_step *sp = cpuhp_get_step(i);
2118
2119 if (sp->name) {
2120 cur = sprintf(buf, "%3d: %s\n", i, sp->name);
2121 buf += cur;
2122 res += cur;
2123 }
2124 }
2125 mutex_unlock(&cpuhp_state_mutex);
2126 return res;
2127}
2128static DEVICE_ATTR(states, 0444, show_cpuhp_states, NULL);
2129
2130static struct attribute *cpuhp_cpu_root_attrs[] = {
2131 &dev_attr_states.attr,
2132 NULL
2133};
2134
2135static const struct attribute_group cpuhp_cpu_root_attr_group = {
2136 .attrs = cpuhp_cpu_root_attrs,
2137 .name = "hotplug",
2138 NULL
2139};
2140
2141#ifdef CONFIG_HOTPLUG_SMT
2142
2143static ssize_t
2144__store_smt_control(struct device *dev, struct device_attribute *attr,
2145 const char *buf, size_t count)
2146{
2147 int ctrlval, ret;
2148
2149 if (sysfs_streq(buf, "on"))
2150 ctrlval = CPU_SMT_ENABLED;
2151 else if (sysfs_streq(buf, "off"))
2152 ctrlval = CPU_SMT_DISABLED;
2153 else if (sysfs_streq(buf, "forceoff"))
2154 ctrlval = CPU_SMT_FORCE_DISABLED;
2155 else
2156 return -EINVAL;
2157
2158 if (cpu_smt_control == CPU_SMT_FORCE_DISABLED)
2159 return -EPERM;
2160
2161 if (cpu_smt_control == CPU_SMT_NOT_SUPPORTED)
2162 return -ENODEV;
2163
2164 ret = lock_device_hotplug_sysfs();
2165 if (ret)
2166 return ret;
2167
2168 if (ctrlval != cpu_smt_control) {
2169 switch (ctrlval) {
2170 case CPU_SMT_ENABLED:
2171 ret = cpuhp_smt_enable();
2172 break;
2173 case CPU_SMT_DISABLED:
2174 case CPU_SMT_FORCE_DISABLED:
2175 ret = cpuhp_smt_disable(ctrlval);
2176 break;
2177 }
2178 }
2179
2180 unlock_device_hotplug();
2181 return ret ? ret : count;
2182}
2183
2184#else /* !CONFIG_HOTPLUG_SMT */
2185static ssize_t
2186__store_smt_control(struct device *dev, struct device_attribute *attr,
2187 const char *buf, size_t count)
2188{
2189 return -ENODEV;
2190}
2191#endif /* CONFIG_HOTPLUG_SMT */
2192
2193static const char *smt_states[] = {
2194 [CPU_SMT_ENABLED] = "on",
2195 [CPU_SMT_DISABLED] = "off",
2196 [CPU_SMT_FORCE_DISABLED] = "forceoff",
2197 [CPU_SMT_NOT_SUPPORTED] = "notsupported",
2198 [CPU_SMT_NOT_IMPLEMENTED] = "notimplemented",
2199};
2200
2201static ssize_t
2202show_smt_control(struct device *dev, struct device_attribute *attr, char *buf)
2203{
2204 const char *state = smt_states[cpu_smt_control];
2205
2206 return snprintf(buf, PAGE_SIZE - 2, "%s\n", state);
2207}
2208
2209static ssize_t
2210store_smt_control(struct device *dev, struct device_attribute *attr,
2211 const char *buf, size_t count)
2212{
2213 return __store_smt_control(dev, attr, buf, count);
2214}
2215static DEVICE_ATTR(control, 0644, show_smt_control, store_smt_control);
2216
2217static ssize_t
2218show_smt_active(struct device *dev, struct device_attribute *attr, char *buf)
2219{
2220 return snprintf(buf, PAGE_SIZE - 2, "%d\n", sched_smt_active());
2221}
2222static DEVICE_ATTR(active, 0444, show_smt_active, NULL);
2223
2224static struct attribute *cpuhp_smt_attrs[] = {
2225 &dev_attr_control.attr,
2226 &dev_attr_active.attr,
2227 NULL
2228};
2229
2230static const struct attribute_group cpuhp_smt_attr_group = {
2231 .attrs = cpuhp_smt_attrs,
2232 .name = "smt",
2233 NULL
2234};
2235
2236static int __init cpu_smt_sysfs_init(void)
2237{
2238 return sysfs_create_group(&cpu_subsys.dev_root->kobj,
2239 &cpuhp_smt_attr_group);
2240}
2241
2242static int __init cpuhp_sysfs_init(void)
2243{
2244 int cpu, ret;
2245
2246 ret = cpu_smt_sysfs_init();
2247 if (ret)
2248 return ret;
2249
2250 ret = sysfs_create_group(&cpu_subsys.dev_root->kobj,
2251 &cpuhp_cpu_root_attr_group);
2252 if (ret)
2253 return ret;
2254
2255 for_each_possible_cpu(cpu) {
2256 struct device *dev = get_cpu_device(cpu);
2257
2258 if (!dev)
2259 continue;
2260 ret = sysfs_create_group(&dev->kobj, &cpuhp_cpu_attr_group);
2261 if (ret)
2262 return ret;
2263 }
2264 return 0;
2265}
2266device_initcall(cpuhp_sysfs_init);
2267#endif /* CONFIG_SYSFS && CONFIG_HOTPLUG_CPU */
2268
2269/*
2270 * cpu_bit_bitmap[] is a special, "compressed" data structure that
2271 * represents all NR_CPUS bits binary values of 1<<nr.
2272 *
2273 * It is used by cpumask_of() to get a constant address to a CPU
2274 * mask value that has a single bit set only.
2275 */
2276
2277/* cpu_bit_bitmap[0] is empty - so we can back into it */
2278#define MASK_DECLARE_1(x) [x+1][0] = (1UL << (x))
2279#define MASK_DECLARE_2(x) MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
2280#define MASK_DECLARE_4(x) MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
2281#define MASK_DECLARE_8(x) MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
2282
2283const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
2284
2285 MASK_DECLARE_8(0), MASK_DECLARE_8(8),
2286 MASK_DECLARE_8(16), MASK_DECLARE_8(24),
2287#if BITS_PER_LONG > 32
2288 MASK_DECLARE_8(32), MASK_DECLARE_8(40),
2289 MASK_DECLARE_8(48), MASK_DECLARE_8(56),
2290#endif
2291};
2292EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
2293
2294const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
2295EXPORT_SYMBOL(cpu_all_bits);
2296
2297#ifdef CONFIG_INIT_ALL_POSSIBLE
2298struct cpumask __cpu_possible_mask __read_mostly
2299 = {CPU_BITS_ALL};
2300#else
2301struct cpumask __cpu_possible_mask __read_mostly;
2302#endif
2303EXPORT_SYMBOL(__cpu_possible_mask);
2304
2305struct cpumask __cpu_online_mask __read_mostly;
2306EXPORT_SYMBOL(__cpu_online_mask);
2307
2308struct cpumask __cpu_present_mask __read_mostly;
2309EXPORT_SYMBOL(__cpu_present_mask);
2310
2311struct cpumask __cpu_active_mask __read_mostly;
2312EXPORT_SYMBOL(__cpu_active_mask);
2313
2314atomic_t __num_online_cpus __read_mostly;
2315EXPORT_SYMBOL(__num_online_cpus);
2316
2317void init_cpu_present(const struct cpumask *src)
2318{
2319 cpumask_copy(&__cpu_present_mask, src);
2320}
2321
2322void init_cpu_possible(const struct cpumask *src)
2323{
2324 cpumask_copy(&__cpu_possible_mask, src);
2325}
2326
2327void init_cpu_online(const struct cpumask *src)
2328{
2329 cpumask_copy(&__cpu_online_mask, src);
2330}
2331
2332void set_cpu_online(unsigned int cpu, bool online)
2333{
2334 /*
2335 * atomic_inc/dec() is required to handle the horrid abuse of this
2336 * function by the reboot and kexec code which invoke it from
2337 * IPI/NMI broadcasts when shutting down CPUs. Invocation from
2338 * regular CPU hotplug is properly serialized.
2339 *
2340 * Note, that the fact that __num_online_cpus is of type atomic_t
2341 * does not protect readers which are not serialized against
2342 * concurrent hotplug operations.
2343 */
2344 if (online) {
2345 if (!cpumask_test_and_set_cpu(cpu, &__cpu_online_mask))
2346 atomic_inc(&__num_online_cpus);
2347 } else {
2348 if (cpumask_test_and_clear_cpu(cpu, &__cpu_online_mask))
2349 atomic_dec(&__num_online_cpus);
2350 }
2351}
2352
2353/*
2354 * Activate the first processor.
2355 */
2356void __init boot_cpu_init(void)
2357{
2358 int cpu = smp_processor_id();
2359
2360 /* Mark the boot cpu "present", "online" etc for SMP and UP case */
2361 set_cpu_online(cpu, true);
2362 set_cpu_active(cpu, true);
2363 set_cpu_present(cpu, true);
2364 set_cpu_possible(cpu, true);
2365
2366#ifdef CONFIG_SMP
2367 __boot_cpu_id = cpu;
2368#endif
2369}
2370
2371/*
2372 * Must be called _AFTER_ setting up the per_cpu areas
2373 */
2374void __init boot_cpu_hotplug_init(void)
2375{
2376#ifdef CONFIG_SMP
2377 cpumask_set_cpu(smp_processor_id(), &cpus_booted_once_mask);
2378#endif
2379 this_cpu_write(cpuhp_state.state, CPUHP_ONLINE);
2380}
2381
2382/*
2383 * These are used for a global "mitigations=" cmdline option for toggling
2384 * optional CPU mitigations.
2385 */
2386enum cpu_mitigations {
2387 CPU_MITIGATIONS_OFF,
2388 CPU_MITIGATIONS_AUTO,
2389 CPU_MITIGATIONS_AUTO_NOSMT,
2390};
2391
2392static enum cpu_mitigations cpu_mitigations __ro_after_init =
2393 CPU_MITIGATIONS_AUTO;
2394
2395static int __init mitigations_parse_cmdline(char *arg)
2396{
2397 if (!strcmp(arg, "off"))
2398 cpu_mitigations = CPU_MITIGATIONS_OFF;
2399 else if (!strcmp(arg, "auto"))
2400 cpu_mitigations = CPU_MITIGATIONS_AUTO;
2401 else if (!strcmp(arg, "auto,nosmt"))
2402 cpu_mitigations = CPU_MITIGATIONS_AUTO_NOSMT;
2403 else
2404 pr_crit("Unsupported mitigations=%s, system may still be vulnerable\n",
2405 arg);
2406
2407 return 0;
2408}
2409early_param("mitigations", mitigations_parse_cmdline);
2410
2411/* mitigations=off */
2412bool cpu_mitigations_off(void)
2413{
2414 return cpu_mitigations == CPU_MITIGATIONS_OFF;
2415}
2416EXPORT_SYMBOL_GPL(cpu_mitigations_off);
2417
2418/* mitigations=auto,nosmt */
2419bool cpu_mitigations_auto_nosmt(void)
2420{
2421 return cpu_mitigations == CPU_MITIGATIONS_AUTO_NOSMT;
2422}
2423EXPORT_SYMBOL_GPL(cpu_mitigations_auto_nosmt);