projects/linux·blob v6.10-rc6 · refs

3202 lines · 77.7 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/delay.h>
21#include <linux/export.h>
22#include <linux/bug.h>
23#include <linux/kthread.h>
24#include <linux/stop_machine.h>
25#include <linux/mutex.h>
26#include <linux/gfp.h>
27#include <linux/suspend.h>
28#include <linux/lockdep.h>
29#include <linux/tick.h>
30#include <linux/irq.h>
31#include <linux/nmi.h>
32#include <linux/smpboot.h>
33#include <linux/relay.h>
34#include <linux/slab.h>
35#include <linux/scs.h>
36#include <linux/percpu-rwsem.h>
37#include <linux/cpuset.h>
38#include <linux/random.h>
39#include <linux/cc_platform.h>
40
41#include <trace/events/power.h>
42#define CREATE_TRACE_POINTS
43#include <trace/events/cpuhp.h>
44
45#include "smpboot.h"
46
47/**
48 * struct cpuhp_cpu_state - Per cpu hotplug state storage
49 * @state: The current cpu state
50 * @target: The target state
51 * @fail: Current CPU hotplug callback state
52 * @thread: Pointer to the hotplug thread
53 * @should_run: Thread should execute
54 * @rollback: Perform a rollback
55 * @single: Single callback invocation
56 * @bringup: Single callback bringup or teardown selector
57 * @node: Remote CPU node; for multi-instance, do a
58 * single entry callback for install/remove
59 * @last: For multi-instance rollback, remember how far we got
60 * @cb_state: The state for a single callback (install/uninstall)
61 * @result: Result of the operation
62 * @ap_sync_state: State for AP synchronization
63 * @done_up: Signal completion to the issuer of the task for cpu-up
64 * @done_down: Signal completion to the issuer of the task for cpu-down
65 */
66struct cpuhp_cpu_state {
67 enum cpuhp_state state;
68 enum cpuhp_state target;
69 enum cpuhp_state fail;
70#ifdef CONFIG_SMP
71 struct task_struct *thread;
72 bool should_run;
73 bool rollback;
74 bool single;
75 bool bringup;
76 struct hlist_node *node;
77 struct hlist_node *last;
78 enum cpuhp_state cb_state;
79 int result;
80 atomic_t ap_sync_state;
81 struct completion done_up;
82 struct completion done_down;
83#endif
84};
85
86static DEFINE_PER_CPU(struct cpuhp_cpu_state, cpuhp_state) = {
87 .fail = CPUHP_INVALID,
88};
89
90#ifdef CONFIG_SMP
91cpumask_t cpus_booted_once_mask;
92#endif
93
94#if defined(CONFIG_LOCKDEP) && defined(CONFIG_SMP)
95static struct lockdep_map cpuhp_state_up_map =
96 STATIC_LOCKDEP_MAP_INIT("cpuhp_state-up", &cpuhp_state_up_map);
97static struct lockdep_map cpuhp_state_down_map =
98 STATIC_LOCKDEP_MAP_INIT("cpuhp_state-down", &cpuhp_state_down_map);
99
100
101static inline void cpuhp_lock_acquire(bool bringup)
102{
103 lock_map_acquire(bringup ? &cpuhp_state_up_map : &cpuhp_state_down_map);
104}
105
106static inline void cpuhp_lock_release(bool bringup)
107{
108 lock_map_release(bringup ? &cpuhp_state_up_map : &cpuhp_state_down_map);
109}
110#else
111
112static inline void cpuhp_lock_acquire(bool bringup) { }
113static inline void cpuhp_lock_release(bool bringup) { }
114
115#endif
116
117/**
118 * struct cpuhp_step - Hotplug state machine step
119 * @name: Name of the step
120 * @startup: Startup function of the step
121 * @teardown: Teardown function of the step
122 * @cant_stop: Bringup/teardown can't be stopped at this step
123 * @multi_instance: State has multiple instances which get added afterwards
124 */
125struct cpuhp_step {
126 const char *name;
127 union {
128 int (*single)(unsigned int cpu);
129 int (*multi)(unsigned int cpu,
130 struct hlist_node *node);
131 } startup;
132 union {
133 int (*single)(unsigned int cpu);
134 int (*multi)(unsigned int cpu,
135 struct hlist_node *node);
136 } teardown;
137 /* private: */
138 struct hlist_head list;
139 /* public: */
140 bool cant_stop;
141 bool multi_instance;
142};
143
144static DEFINE_MUTEX(cpuhp_state_mutex);
145static struct cpuhp_step cpuhp_hp_states[];
146
147static struct cpuhp_step *cpuhp_get_step(enum cpuhp_state state)
148{
149 return cpuhp_hp_states + state;
150}
151
152static bool cpuhp_step_empty(bool bringup, struct cpuhp_step *step)
153{
154 return bringup ? !step->startup.single : !step->teardown.single;
155}
156
157/**
158 * cpuhp_invoke_callback - Invoke the callbacks for a given state
159 * @cpu: The cpu for which the callback should be invoked
160 * @state: The state to do callbacks for
161 * @bringup: True if the bringup callback should be invoked
162 * @node: For multi-instance, do a single entry callback for install/remove
163 * @lastp: For multi-instance rollback, remember how far we got
164 *
165 * Called from cpu hotplug and from the state register machinery.
166 *
167 * Return: %0 on success or a negative errno code
168 */
169static int cpuhp_invoke_callback(unsigned int cpu, enum cpuhp_state state,
170 bool bringup, struct hlist_node *node,
171 struct hlist_node **lastp)
172{
173 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
174 struct cpuhp_step *step = cpuhp_get_step(state);
175 int (*cbm)(unsigned int cpu, struct hlist_node *node);
176 int (*cb)(unsigned int cpu);
177 int ret, cnt;
178
179 if (st->fail == state) {
180 st->fail = CPUHP_INVALID;
181 return -EAGAIN;
182 }
183
184 if (cpuhp_step_empty(bringup, step)) {
185 WARN_ON_ONCE(1);
186 return 0;
187 }
188
189 if (!step->multi_instance) {
190 WARN_ON_ONCE(lastp && *lastp);
191 cb = bringup ? step->startup.single : step->teardown.single;
192
193 trace_cpuhp_enter(cpu, st->target, state, cb);
194 ret = cb(cpu);
195 trace_cpuhp_exit(cpu, st->state, state, ret);
196 return ret;
197 }
198 cbm = bringup ? step->startup.multi : step->teardown.multi;
199
200 /* Single invocation for instance add/remove */
201 if (node) {
202 WARN_ON_ONCE(lastp && *lastp);
203 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
204 ret = cbm(cpu, node);
205 trace_cpuhp_exit(cpu, st->state, state, ret);
206 return ret;
207 }
208
209 /* State transition. Invoke on all instances */
210 cnt = 0;
211 hlist_for_each(node, &step->list) {
212 if (lastp && node == *lastp)
213 break;
214
215 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
216 ret = cbm(cpu, node);
217 trace_cpuhp_exit(cpu, st->state, state, ret);
218 if (ret) {
219 if (!lastp)
220 goto err;
221
222 *lastp = node;
223 return ret;
224 }
225 cnt++;
226 }
227 if (lastp)
228 *lastp = NULL;
229 return 0;
230err:
231 /* Rollback the instances if one failed */
232 cbm = !bringup ? step->startup.multi : step->teardown.multi;
233 if (!cbm)
234 return ret;
235
236 hlist_for_each(node, &step->list) {
237 if (!cnt--)
238 break;
239
240 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
241 ret = cbm(cpu, node);
242 trace_cpuhp_exit(cpu, st->state, state, ret);
243 /*
244 * Rollback must not fail,
245 */
246 WARN_ON_ONCE(ret);
247 }
248 return ret;
249}
250
251#ifdef CONFIG_SMP
252static bool cpuhp_is_ap_state(enum cpuhp_state state)
253{
254 /*
255 * The extra check for CPUHP_TEARDOWN_CPU is only for documentation
256 * purposes as that state is handled explicitly in cpu_down.
257 */
258 return state > CPUHP_BRINGUP_CPU && state != CPUHP_TEARDOWN_CPU;
259}
260
261static inline void wait_for_ap_thread(struct cpuhp_cpu_state *st, bool bringup)
262{
263 struct completion *done = bringup ? &st->done_up : &st->done_down;
264 wait_for_completion(done);
265}
266
267static inline void complete_ap_thread(struct cpuhp_cpu_state *st, bool bringup)
268{
269 struct completion *done = bringup ? &st->done_up : &st->done_down;
270 complete(done);
271}
272
273/*
274 * The former STARTING/DYING states, ran with IRQs disabled and must not fail.
275 */
276static bool cpuhp_is_atomic_state(enum cpuhp_state state)
277{
278 return CPUHP_AP_IDLE_DEAD <= state && state < CPUHP_AP_ONLINE;
279}
280
281/* Synchronization state management */
282enum cpuhp_sync_state {
283 SYNC_STATE_DEAD,
284 SYNC_STATE_KICKED,
285 SYNC_STATE_SHOULD_DIE,
286 SYNC_STATE_ALIVE,
287 SYNC_STATE_SHOULD_ONLINE,
288 SYNC_STATE_ONLINE,
289};
290
291#ifdef CONFIG_HOTPLUG_CORE_SYNC
292/**
293 * cpuhp_ap_update_sync_state - Update synchronization state during bringup/teardown
294 * @state: The synchronization state to set
295 *
296 * No synchronization point. Just update of the synchronization state, but implies
297 * a full barrier so that the AP changes are visible before the control CPU proceeds.
298 */
299static inline void cpuhp_ap_update_sync_state(enum cpuhp_sync_state state)
300{
301 atomic_t *st = this_cpu_ptr(&cpuhp_state.ap_sync_state);
302
303 (void)atomic_xchg(st, state);
304}
305
306void __weak arch_cpuhp_sync_state_poll(void) { cpu_relax(); }
307
308static bool cpuhp_wait_for_sync_state(unsigned int cpu, enum cpuhp_sync_state state,
309 enum cpuhp_sync_state next_state)
310{
311 atomic_t *st = per_cpu_ptr(&cpuhp_state.ap_sync_state, cpu);
312 ktime_t now, end, start = ktime_get();
313 int sync;
314
315 end = start + 10ULL * NSEC_PER_SEC;
316
317 sync = atomic_read(st);
318 while (1) {
319 if (sync == state) {
320 if (!atomic_try_cmpxchg(st, &sync, next_state))
321 continue;
322 return true;
323 }
324
325 now = ktime_get();
326 if (now > end) {
327 /* Timeout. Leave the state unchanged */
328 return false;
329 } else if (now - start < NSEC_PER_MSEC) {
330 /* Poll for one millisecond */
331 arch_cpuhp_sync_state_poll();
332 } else {
333 usleep_range_state(USEC_PER_MSEC, 2 * USEC_PER_MSEC, TASK_UNINTERRUPTIBLE);
334 }
335 sync = atomic_read(st);
336 }
337 return true;
338}
339#else /* CONFIG_HOTPLUG_CORE_SYNC */
340static inline void cpuhp_ap_update_sync_state(enum cpuhp_sync_state state) { }
341#endif /* !CONFIG_HOTPLUG_CORE_SYNC */
342
343#ifdef CONFIG_HOTPLUG_CORE_SYNC_DEAD
344/**
345 * cpuhp_ap_report_dead - Update synchronization state to DEAD
346 *
347 * No synchronization point. Just update of the synchronization state.
348 */
349void cpuhp_ap_report_dead(void)
350{
351 cpuhp_ap_update_sync_state(SYNC_STATE_DEAD);
352}
353
354void __weak arch_cpuhp_cleanup_dead_cpu(unsigned int cpu) { }
355
356/*
357 * Late CPU shutdown synchronization point. Cannot use cpuhp_state::done_down
358 * because the AP cannot issue complete() at this stage.
359 */
360static void cpuhp_bp_sync_dead(unsigned int cpu)
361{
362 atomic_t *st = per_cpu_ptr(&cpuhp_state.ap_sync_state, cpu);
363 int sync = atomic_read(st);
364
365 do {
366 /* CPU can have reported dead already. Don't overwrite that! */
367 if (sync == SYNC_STATE_DEAD)
368 break;
369 } while (!atomic_try_cmpxchg(st, &sync, SYNC_STATE_SHOULD_DIE));
370
371 if (cpuhp_wait_for_sync_state(cpu, SYNC_STATE_DEAD, SYNC_STATE_DEAD)) {
372 /* CPU reached dead state. Invoke the cleanup function */
373 arch_cpuhp_cleanup_dead_cpu(cpu);
374 return;
375 }
376
377 /* No further action possible. Emit message and give up. */
378 pr_err("CPU%u failed to report dead state\n", cpu);
379}
380#else /* CONFIG_HOTPLUG_CORE_SYNC_DEAD */
381static inline void cpuhp_bp_sync_dead(unsigned int cpu) { }
382#endif /* !CONFIG_HOTPLUG_CORE_SYNC_DEAD */
383
384#ifdef CONFIG_HOTPLUG_CORE_SYNC_FULL
385/**
386 * cpuhp_ap_sync_alive - Synchronize AP with the control CPU once it is alive
387 *
388 * Updates the AP synchronization state to SYNC_STATE_ALIVE and waits
389 * for the BP to release it.
390 */
391void cpuhp_ap_sync_alive(void)
392{
393 atomic_t *st = this_cpu_ptr(&cpuhp_state.ap_sync_state);
394
395 cpuhp_ap_update_sync_state(SYNC_STATE_ALIVE);
396
397 /* Wait for the control CPU to release it. */
398 while (atomic_read(st) != SYNC_STATE_SHOULD_ONLINE)
399 cpu_relax();
400}
401
402static bool cpuhp_can_boot_ap(unsigned int cpu)
403{
404 atomic_t *st = per_cpu_ptr(&cpuhp_state.ap_sync_state, cpu);
405 int sync = atomic_read(st);
406
407again:
408 switch (sync) {
409 case SYNC_STATE_DEAD:
410 /* CPU is properly dead */
411 break;
412 case SYNC_STATE_KICKED:
413 /* CPU did not come up in previous attempt */
414 break;
415 case SYNC_STATE_ALIVE:
416 /* CPU is stuck cpuhp_ap_sync_alive(). */
417 break;
418 default:
419 /* CPU failed to report online or dead and is in limbo state. */
420 return false;
421 }
422
423 /* Prepare for booting */
424 if (!atomic_try_cmpxchg(st, &sync, SYNC_STATE_KICKED))
425 goto again;
426
427 return true;
428}
429
430void __weak arch_cpuhp_cleanup_kick_cpu(unsigned int cpu) { }
431
432/*
433 * Early CPU bringup synchronization point. Cannot use cpuhp_state::done_up
434 * because the AP cannot issue complete() so early in the bringup.
435 */
436static int cpuhp_bp_sync_alive(unsigned int cpu)
437{
438 int ret = 0;
439
440 if (!IS_ENABLED(CONFIG_HOTPLUG_CORE_SYNC_FULL))
441 return 0;
442
443 if (!cpuhp_wait_for_sync_state(cpu, SYNC_STATE_ALIVE, SYNC_STATE_SHOULD_ONLINE)) {
444 pr_err("CPU%u failed to report alive state\n", cpu);
445 ret = -EIO;
446 }
447
448 /* Let the architecture cleanup the kick alive mechanics. */
449 arch_cpuhp_cleanup_kick_cpu(cpu);
450 return ret;
451}
452#else /* CONFIG_HOTPLUG_CORE_SYNC_FULL */
453static inline int cpuhp_bp_sync_alive(unsigned int cpu) { return 0; }
454static inline bool cpuhp_can_boot_ap(unsigned int cpu) { return true; }
455#endif /* !CONFIG_HOTPLUG_CORE_SYNC_FULL */
456
457/* Serializes the updates to cpu_online_mask, cpu_present_mask */
458static DEFINE_MUTEX(cpu_add_remove_lock);
459bool cpuhp_tasks_frozen;
460EXPORT_SYMBOL_GPL(cpuhp_tasks_frozen);
461
462/*
463 * The following two APIs (cpu_maps_update_begin/done) must be used when
464 * attempting to serialize the updates to cpu_online_mask & cpu_present_mask.
465 */
466void cpu_maps_update_begin(void)
467{
468 mutex_lock(&cpu_add_remove_lock);
469}
470
471void cpu_maps_update_done(void)
472{
473 mutex_unlock(&cpu_add_remove_lock);
474}
475
476/*
477 * If set, cpu_up and cpu_down will return -EBUSY and do nothing.
478 * Should always be manipulated under cpu_add_remove_lock
479 */
480static int cpu_hotplug_disabled;
481
482#ifdef CONFIG_HOTPLUG_CPU
483
484DEFINE_STATIC_PERCPU_RWSEM(cpu_hotplug_lock);
485
486void cpus_read_lock(void)
487{
488 percpu_down_read(&cpu_hotplug_lock);
489}
490EXPORT_SYMBOL_GPL(cpus_read_lock);
491
492int cpus_read_trylock(void)
493{
494 return percpu_down_read_trylock(&cpu_hotplug_lock);
495}
496EXPORT_SYMBOL_GPL(cpus_read_trylock);
497
498void cpus_read_unlock(void)
499{
500 percpu_up_read(&cpu_hotplug_lock);
501}
502EXPORT_SYMBOL_GPL(cpus_read_unlock);
503
504void cpus_write_lock(void)
505{
506 percpu_down_write(&cpu_hotplug_lock);
507}
508
509void cpus_write_unlock(void)
510{
511 percpu_up_write(&cpu_hotplug_lock);
512}
513
514void lockdep_assert_cpus_held(void)
515{
516 /*
517 * We can't have hotplug operations before userspace starts running,
518 * and some init codepaths will knowingly not take the hotplug lock.
519 * This is all valid, so mute lockdep until it makes sense to report
520 * unheld locks.
521 */
522 if (system_state < SYSTEM_RUNNING)
523 return;
524
525 percpu_rwsem_assert_held(&cpu_hotplug_lock);
526}
527
528#ifdef CONFIG_LOCKDEP
529int lockdep_is_cpus_held(void)
530{
531 return percpu_rwsem_is_held(&cpu_hotplug_lock);
532}
533#endif
534
535static void lockdep_acquire_cpus_lock(void)
536{
537 rwsem_acquire(&cpu_hotplug_lock.dep_map, 0, 0, _THIS_IP_);
538}
539
540static void lockdep_release_cpus_lock(void)
541{
542 rwsem_release(&cpu_hotplug_lock.dep_map, _THIS_IP_);
543}
544
545/*
546 * Wait for currently running CPU hotplug operations to complete (if any) and
547 * disable future CPU hotplug (from sysfs). The 'cpu_add_remove_lock' protects
548 * the 'cpu_hotplug_disabled' flag. The same lock is also acquired by the
549 * hotplug path before performing hotplug operations. So acquiring that lock
550 * guarantees mutual exclusion from any currently running hotplug operations.
551 */
552void cpu_hotplug_disable(void)
553{
554 cpu_maps_update_begin();
555 cpu_hotplug_disabled++;
556 cpu_maps_update_done();
557}
558EXPORT_SYMBOL_GPL(cpu_hotplug_disable);
559
560static void __cpu_hotplug_enable(void)
561{
562 if (WARN_ONCE(!cpu_hotplug_disabled, "Unbalanced cpu hotplug enable\n"))
563 return;
564 cpu_hotplug_disabled--;
565}
566
567void cpu_hotplug_enable(void)
568{
569 cpu_maps_update_begin();
570 __cpu_hotplug_enable();
571 cpu_maps_update_done();
572}
573EXPORT_SYMBOL_GPL(cpu_hotplug_enable);
574
575#else
576
577static void lockdep_acquire_cpus_lock(void)
578{
579}
580
581static void lockdep_release_cpus_lock(void)
582{
583}
584
585#endif /* CONFIG_HOTPLUG_CPU */
586
587/*
588 * Architectures that need SMT-specific errata handling during SMT hotplug
589 * should override this.
590 */
591void __weak arch_smt_update(void) { }
592
593#ifdef CONFIG_HOTPLUG_SMT
594
595enum cpuhp_smt_control cpu_smt_control __read_mostly = CPU_SMT_ENABLED;
596static unsigned int cpu_smt_max_threads __ro_after_init;
597unsigned int cpu_smt_num_threads __read_mostly = UINT_MAX;
598
599void __init cpu_smt_disable(bool force)
600{
601 if (!cpu_smt_possible())
602 return;
603
604 if (force) {
605 pr_info("SMT: Force disabled\n");
606 cpu_smt_control = CPU_SMT_FORCE_DISABLED;
607 } else {
608 pr_info("SMT: disabled\n");
609 cpu_smt_control = CPU_SMT_DISABLED;
610 }
611 cpu_smt_num_threads = 1;
612}
613
614/*
615 * The decision whether SMT is supported can only be done after the full
616 * CPU identification. Called from architecture code.
617 */
618void __init cpu_smt_set_num_threads(unsigned int num_threads,
619 unsigned int max_threads)
620{
621 WARN_ON(!num_threads || (num_threads > max_threads));
622
623 if (max_threads == 1)
624 cpu_smt_control = CPU_SMT_NOT_SUPPORTED;
625
626 cpu_smt_max_threads = max_threads;
627
628 /*
629 * If SMT has been disabled via the kernel command line or SMT is
630 * not supported, set cpu_smt_num_threads to 1 for consistency.
631 * If enabled, take the architecture requested number of threads
632 * to bring up into account.
633 */
634 if (cpu_smt_control != CPU_SMT_ENABLED)
635 cpu_smt_num_threads = 1;
636 else if (num_threads < cpu_smt_num_threads)
637 cpu_smt_num_threads = num_threads;
638}
639
640static int __init smt_cmdline_disable(char *str)
641{
642 cpu_smt_disable(str && !strcmp(str, "force"));
643 return 0;
644}
645early_param("nosmt", smt_cmdline_disable);
646
647/*
648 * For Archicture supporting partial SMT states check if the thread is allowed.
649 * Otherwise this has already been checked through cpu_smt_max_threads when
650 * setting the SMT level.
651 */
652static inline bool cpu_smt_thread_allowed(unsigned int cpu)
653{
654#ifdef CONFIG_SMT_NUM_THREADS_DYNAMIC
655 return topology_smt_thread_allowed(cpu);
656#else
657 return true;
658#endif
659}
660
661static inline bool cpu_bootable(unsigned int cpu)
662{
663 if (cpu_smt_control == CPU_SMT_ENABLED && cpu_smt_thread_allowed(cpu))
664 return true;
665
666 /* All CPUs are bootable if controls are not configured */
667 if (cpu_smt_control == CPU_SMT_NOT_IMPLEMENTED)
668 return true;
669
670 /* All CPUs are bootable if CPU is not SMT capable */
671 if (cpu_smt_control == CPU_SMT_NOT_SUPPORTED)
672 return true;
673
674 if (topology_is_primary_thread(cpu))
675 return true;
676
677 /*
678 * On x86 it's required to boot all logical CPUs at least once so
679 * that the init code can get a chance to set CR4.MCE on each
680 * CPU. Otherwise, a broadcasted MCE observing CR4.MCE=0b on any
681 * core will shutdown the machine.
682 */
683 return !cpumask_test_cpu(cpu, &cpus_booted_once_mask);
684}
685
686/* Returns true if SMT is supported and not forcefully (irreversibly) disabled */
687bool cpu_smt_possible(void)
688{
689 return cpu_smt_control != CPU_SMT_FORCE_DISABLED &&
690 cpu_smt_control != CPU_SMT_NOT_SUPPORTED;
691}
692EXPORT_SYMBOL_GPL(cpu_smt_possible);
693
694#else
695static inline bool cpu_bootable(unsigned int cpu) { return true; }
696#endif
697
698static inline enum cpuhp_state
699cpuhp_set_state(int cpu, struct cpuhp_cpu_state *st, enum cpuhp_state target)
700{
701 enum cpuhp_state prev_state = st->state;
702 bool bringup = st->state < target;
703
704 st->rollback = false;
705 st->last = NULL;
706
707 st->target = target;
708 st->single = false;
709 st->bringup = bringup;
710 if (cpu_dying(cpu) != !bringup)
711 set_cpu_dying(cpu, !bringup);
712
713 return prev_state;
714}
715
716static inline void
717cpuhp_reset_state(int cpu, struct cpuhp_cpu_state *st,
718 enum cpuhp_state prev_state)
719{
720 bool bringup = !st->bringup;
721
722 st->target = prev_state;
723
724 /*
725 * Already rolling back. No need invert the bringup value or to change
726 * the current state.
727 */
728 if (st->rollback)
729 return;
730
731 st->rollback = true;
732
733 /*
734 * If we have st->last we need to undo partial multi_instance of this
735 * state first. Otherwise start undo at the previous state.
736 */
737 if (!st->last) {
738 if (st->bringup)
739 st->state--;
740 else
741 st->state++;
742 }
743
744 st->bringup = bringup;
745 if (cpu_dying(cpu) != !bringup)
746 set_cpu_dying(cpu, !bringup);
747}
748
749/* Regular hotplug invocation of the AP hotplug thread */
750static void __cpuhp_kick_ap(struct cpuhp_cpu_state *st)
751{
752 if (!st->single && st->state == st->target)
753 return;
754
755 st->result = 0;
756 /*
757 * Make sure the above stores are visible before should_run becomes
758 * true. Paired with the mb() above in cpuhp_thread_fun()
759 */
760 smp_mb();
761 st->should_run = true;
762 wake_up_process(st->thread);
763 wait_for_ap_thread(st, st->bringup);
764}
765
766static int cpuhp_kick_ap(int cpu, struct cpuhp_cpu_state *st,
767 enum cpuhp_state target)
768{
769 enum cpuhp_state prev_state;
770 int ret;
771
772 prev_state = cpuhp_set_state(cpu, st, target);
773 __cpuhp_kick_ap(st);
774 if ((ret = st->result)) {
775 cpuhp_reset_state(cpu, st, prev_state);
776 __cpuhp_kick_ap(st);
777 }
778
779 return ret;
780}
781
782static int bringup_wait_for_ap_online(unsigned int cpu)
783{
784 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
785
786 /* Wait for the CPU to reach CPUHP_AP_ONLINE_IDLE */
787 wait_for_ap_thread(st, true);
788 if (WARN_ON_ONCE((!cpu_online(cpu))))
789 return -ECANCELED;
790
791 /* Unpark the hotplug thread of the target cpu */
792 kthread_unpark(st->thread);
793
794 /*
795 * SMT soft disabling on X86 requires to bring the CPU out of the
796 * BIOS 'wait for SIPI' state in order to set the CR4.MCE bit. The
797 * CPU marked itself as booted_once in notify_cpu_starting() so the
798 * cpu_bootable() check will now return false if this is not the
799 * primary sibling.
800 */
801 if (!cpu_bootable(cpu))
802 return -ECANCELED;
803 return 0;
804}
805
806#ifdef CONFIG_HOTPLUG_SPLIT_STARTUP
807static int cpuhp_kick_ap_alive(unsigned int cpu)
808{
809 if (!cpuhp_can_boot_ap(cpu))
810 return -EAGAIN;
811
812 return arch_cpuhp_kick_ap_alive(cpu, idle_thread_get(cpu));
813}
814
815static int cpuhp_bringup_ap(unsigned int cpu)
816{
817 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
818 int ret;
819
820 /*
821 * Some architectures have to walk the irq descriptors to
822 * setup the vector space for the cpu which comes online.
823 * Prevent irq alloc/free across the bringup.
824 */
825 irq_lock_sparse();
826
827 ret = cpuhp_bp_sync_alive(cpu);
828 if (ret)
829 goto out_unlock;
830
831 ret = bringup_wait_for_ap_online(cpu);
832 if (ret)
833 goto out_unlock;
834
835 irq_unlock_sparse();
836
837 if (st->target <= CPUHP_AP_ONLINE_IDLE)
838 return 0;
839
840 return cpuhp_kick_ap(cpu, st, st->target);
841
842out_unlock:
843 irq_unlock_sparse();
844 return ret;
845}
846#else
847static int bringup_cpu(unsigned int cpu)
848{
849 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
850 struct task_struct *idle = idle_thread_get(cpu);
851 int ret;
852
853 if (!cpuhp_can_boot_ap(cpu))
854 return -EAGAIN;
855
856 /*
857 * Some architectures have to walk the irq descriptors to
858 * setup the vector space for the cpu which comes online.
859 *
860 * Prevent irq alloc/free across the bringup by acquiring the
861 * sparse irq lock. Hold it until the upcoming CPU completes the
862 * startup in cpuhp_online_idle() which allows to avoid
863 * intermediate synchronization points in the architecture code.
864 */
865 irq_lock_sparse();
866
867 ret = __cpu_up(cpu, idle);
868 if (ret)
869 goto out_unlock;
870
871 ret = cpuhp_bp_sync_alive(cpu);
872 if (ret)
873 goto out_unlock;
874
875 ret = bringup_wait_for_ap_online(cpu);
876 if (ret)
877 goto out_unlock;
878
879 irq_unlock_sparse();
880
881 if (st->target <= CPUHP_AP_ONLINE_IDLE)
882 return 0;
883
884 return cpuhp_kick_ap(cpu, st, st->target);
885
886out_unlock:
887 irq_unlock_sparse();
888 return ret;
889}
890#endif
891
892static int finish_cpu(unsigned int cpu)
893{
894 struct task_struct *idle = idle_thread_get(cpu);
895 struct mm_struct *mm = idle->active_mm;
896
897 /*
898 * idle_task_exit() will have switched to &init_mm, now
899 * clean up any remaining active_mm state.
900 */
901 if (mm != &init_mm)
902 idle->active_mm = &init_mm;
903 mmdrop_lazy_tlb(mm);
904 return 0;
905}
906
907/*
908 * Hotplug state machine related functions
909 */
910
911/*
912 * Get the next state to run. Empty ones will be skipped. Returns true if a
913 * state must be run.
914 *
915 * st->state will be modified ahead of time, to match state_to_run, as if it
916 * has already ran.
917 */
918static bool cpuhp_next_state(bool bringup,
919 enum cpuhp_state *state_to_run,
920 struct cpuhp_cpu_state *st,
921 enum cpuhp_state target)
922{
923 do {
924 if (bringup) {
925 if (st->state >= target)
926 return false;
927
928 *state_to_run = ++st->state;
929 } else {
930 if (st->state <= target)
931 return false;
932
933 *state_to_run = st->state--;
934 }
935
936 if (!cpuhp_step_empty(bringup, cpuhp_get_step(*state_to_run)))
937 break;
938 } while (true);
939
940 return true;
941}
942
943static int __cpuhp_invoke_callback_range(bool bringup,
944 unsigned int cpu,
945 struct cpuhp_cpu_state *st,
946 enum cpuhp_state target,
947 bool nofail)
948{
949 enum cpuhp_state state;
950 int ret = 0;
951
952 while (cpuhp_next_state(bringup, &state, st, target)) {
953 int err;
954
955 err = cpuhp_invoke_callback(cpu, state, bringup, NULL, NULL);
956 if (!err)
957 continue;
958
959 if (nofail) {
960 pr_warn("CPU %u %s state %s (%d) failed (%d)\n",
961 cpu, bringup ? "UP" : "DOWN",
962 cpuhp_get_step(st->state)->name,
963 st->state, err);
964 ret = -1;
965 } else {
966 ret = err;
967 break;
968 }
969 }
970
971 return ret;
972}
973
974static inline int cpuhp_invoke_callback_range(bool bringup,
975 unsigned int cpu,
976 struct cpuhp_cpu_state *st,
977 enum cpuhp_state target)
978{
979 return __cpuhp_invoke_callback_range(bringup, cpu, st, target, false);
980}
981
982static inline void cpuhp_invoke_callback_range_nofail(bool bringup,
983 unsigned int cpu,
984 struct cpuhp_cpu_state *st,
985 enum cpuhp_state target)
986{
987 __cpuhp_invoke_callback_range(bringup, cpu, st, target, true);
988}
989
990static inline bool can_rollback_cpu(struct cpuhp_cpu_state *st)
991{
992 if (IS_ENABLED(CONFIG_HOTPLUG_CPU))
993 return true;
994 /*
995 * When CPU hotplug is disabled, then taking the CPU down is not
996 * possible because takedown_cpu() and the architecture and
997 * subsystem specific mechanisms are not available. So the CPU
998 * which would be completely unplugged again needs to stay around
999 * in the current state.
1000 */
1001 return st->state <= CPUHP_BRINGUP_CPU;
1002}
1003
1004static int cpuhp_up_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
1005 enum cpuhp_state target)
1006{
1007 enum cpuhp_state prev_state = st->state;
1008 int ret = 0;
1009
1010 ret = cpuhp_invoke_callback_range(true, cpu, st, target);
1011 if (ret) {
1012 pr_debug("CPU UP failed (%d) CPU %u state %s (%d)\n",
1013 ret, cpu, cpuhp_get_step(st->state)->name,
1014 st->state);
1015
1016 cpuhp_reset_state(cpu, st, prev_state);
1017 if (can_rollback_cpu(st))
1018 WARN_ON(cpuhp_invoke_callback_range(false, cpu, st,
1019 prev_state));
1020 }
1021 return ret;
1022}
1023
1024/*
1025 * The cpu hotplug threads manage the bringup and teardown of the cpus
1026 */
1027static int cpuhp_should_run(unsigned int cpu)
1028{
1029 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
1030
1031 return st->should_run;
1032}
1033
1034/*
1035 * Execute teardown/startup callbacks on the plugged cpu. Also used to invoke
1036 * callbacks when a state gets [un]installed at runtime.
1037 *
1038 * Each invocation of this function by the smpboot thread does a single AP
1039 * state callback.
1040 *
1041 * It has 3 modes of operation:
1042 * - single: runs st->cb_state
1043 * - up: runs ++st->state, while st->state < st->target
1044 * - down: runs st->state--, while st->state > st->target
1045 *
1046 * When complete or on error, should_run is cleared and the completion is fired.
1047 */
1048static void cpuhp_thread_fun(unsigned int cpu)
1049{
1050 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
1051 bool bringup = st->bringup;
1052 enum cpuhp_state state;
1053
1054 if (WARN_ON_ONCE(!st->should_run))
1055 return;
1056
1057 /*
1058 * ACQUIRE for the cpuhp_should_run() load of ->should_run. Ensures
1059 * that if we see ->should_run we also see the rest of the state.
1060 */
1061 smp_mb();
1062
1063 /*
1064 * The BP holds the hotplug lock, but we're now running on the AP,
1065 * ensure that anybody asserting the lock is held, will actually find
1066 * it so.
1067 */
1068 lockdep_acquire_cpus_lock();
1069 cpuhp_lock_acquire(bringup);
1070
1071 if (st->single) {
1072 state = st->cb_state;
1073 st->should_run = false;
1074 } else {
1075 st->should_run = cpuhp_next_state(bringup, &state, st, st->target);
1076 if (!st->should_run)
1077 goto end;
1078 }
1079
1080 WARN_ON_ONCE(!cpuhp_is_ap_state(state));
1081
1082 if (cpuhp_is_atomic_state(state)) {
1083 local_irq_disable();
1084 st->result = cpuhp_invoke_callback(cpu, state, bringup, st->node, &st->last);
1085 local_irq_enable();
1086
1087 /*
1088 * STARTING/DYING must not fail!
1089 */
1090 WARN_ON_ONCE(st->result);
1091 } else {
1092 st->result = cpuhp_invoke_callback(cpu, state, bringup, st->node, &st->last);
1093 }
1094
1095 if (st->result) {
1096 /*
1097 * If we fail on a rollback, we're up a creek without no
1098 * paddle, no way forward, no way back. We loose, thanks for
1099 * playing.
1100 */
1101 WARN_ON_ONCE(st->rollback);
1102 st->should_run = false;
1103 }
1104
1105end:
1106 cpuhp_lock_release(bringup);
1107 lockdep_release_cpus_lock();
1108
1109 if (!st->should_run)
1110 complete_ap_thread(st, bringup);
1111}
1112
1113/* Invoke a single callback on a remote cpu */
1114static int
1115cpuhp_invoke_ap_callback(int cpu, enum cpuhp_state state, bool bringup,
1116 struct hlist_node *node)
1117{
1118 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1119 int ret;
1120
1121 if (!cpu_online(cpu))
1122 return 0;
1123
1124 cpuhp_lock_acquire(false);
1125 cpuhp_lock_release(false);
1126
1127 cpuhp_lock_acquire(true);
1128 cpuhp_lock_release(true);
1129
1130 /*
1131 * If we are up and running, use the hotplug thread. For early calls
1132 * we invoke the thread function directly.
1133 */
1134 if (!st->thread)
1135 return cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
1136
1137 st->rollback = false;
1138 st->last = NULL;
1139
1140 st->node = node;
1141 st->bringup = bringup;
1142 st->cb_state = state;
1143 st->single = true;
1144
1145 __cpuhp_kick_ap(st);
1146
1147 /*
1148 * If we failed and did a partial, do a rollback.
1149 */
1150 if ((ret = st->result) && st->last) {
1151 st->rollback = true;
1152 st->bringup = !bringup;
1153
1154 __cpuhp_kick_ap(st);
1155 }
1156
1157 /*
1158 * Clean up the leftovers so the next hotplug operation wont use stale
1159 * data.
1160 */
1161 st->node = st->last = NULL;
1162 return ret;
1163}
1164
1165static int cpuhp_kick_ap_work(unsigned int cpu)
1166{
1167 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1168 enum cpuhp_state prev_state = st->state;
1169 int ret;
1170
1171 cpuhp_lock_acquire(false);
1172 cpuhp_lock_release(false);
1173
1174 cpuhp_lock_acquire(true);
1175 cpuhp_lock_release(true);
1176
1177 trace_cpuhp_enter(cpu, st->target, prev_state, cpuhp_kick_ap_work);
1178 ret = cpuhp_kick_ap(cpu, st, st->target);
1179 trace_cpuhp_exit(cpu, st->state, prev_state, ret);
1180
1181 return ret;
1182}
1183
1184static struct smp_hotplug_thread cpuhp_threads = {
1185 .store = &cpuhp_state.thread,
1186 .thread_should_run = cpuhp_should_run,
1187 .thread_fn = cpuhp_thread_fun,
1188 .thread_comm = "cpuhp/%u",
1189 .selfparking = true,
1190};
1191
1192static __init void cpuhp_init_state(void)
1193{
1194 struct cpuhp_cpu_state *st;
1195 int cpu;
1196
1197 for_each_possible_cpu(cpu) {
1198 st = per_cpu_ptr(&cpuhp_state, cpu);
1199 init_completion(&st->done_up);
1200 init_completion(&st->done_down);
1201 }
1202}
1203
1204void __init cpuhp_threads_init(void)
1205{
1206 cpuhp_init_state();
1207 BUG_ON(smpboot_register_percpu_thread(&cpuhp_threads));
1208 kthread_unpark(this_cpu_read(cpuhp_state.thread));
1209}
1210
1211#ifdef CONFIG_HOTPLUG_CPU
1212#ifndef arch_clear_mm_cpumask_cpu
1213#define arch_clear_mm_cpumask_cpu(cpu, mm) cpumask_clear_cpu(cpu, mm_cpumask(mm))
1214#endif
1215
1216/**
1217 * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
1218 * @cpu: a CPU id
1219 *
1220 * This function walks all processes, finds a valid mm struct for each one and
1221 * then clears a corresponding bit in mm's cpumask. While this all sounds
1222 * trivial, there are various non-obvious corner cases, which this function
1223 * tries to solve in a safe manner.
1224 *
1225 * Also note that the function uses a somewhat relaxed locking scheme, so it may
1226 * be called only for an already offlined CPU.
1227 */
1228void clear_tasks_mm_cpumask(int cpu)
1229{
1230 struct task_struct *p;
1231
1232 /*
1233 * This function is called after the cpu is taken down and marked
1234 * offline, so its not like new tasks will ever get this cpu set in
1235 * their mm mask. -- Peter Zijlstra
1236 * Thus, we may use rcu_read_lock() here, instead of grabbing
1237 * full-fledged tasklist_lock.
1238 */
1239 WARN_ON(cpu_online(cpu));
1240 rcu_read_lock();
1241 for_each_process(p) {
1242 struct task_struct *t;
1243
1244 /*
1245 * Main thread might exit, but other threads may still have
1246 * a valid mm. Find one.
1247 */
1248 t = find_lock_task_mm(p);
1249 if (!t)
1250 continue;
1251 arch_clear_mm_cpumask_cpu(cpu, t->mm);
1252 task_unlock(t);
1253 }
1254 rcu_read_unlock();
1255}
1256
1257/* Take this CPU down. */
1258static int take_cpu_down(void *_param)
1259{
1260 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
1261 enum cpuhp_state target = max((int)st->target, CPUHP_AP_OFFLINE);
1262 int err, cpu = smp_processor_id();
1263
1264 /* Ensure this CPU doesn't handle any more interrupts. */
1265 err = __cpu_disable();
1266 if (err < 0)
1267 return err;
1268
1269 /*
1270 * Must be called from CPUHP_TEARDOWN_CPU, which means, as we are going
1271 * down, that the current state is CPUHP_TEARDOWN_CPU - 1.
1272 */
1273 WARN_ON(st->state != (CPUHP_TEARDOWN_CPU - 1));
1274
1275 /*
1276 * Invoke the former CPU_DYING callbacks. DYING must not fail!
1277 */
1278 cpuhp_invoke_callback_range_nofail(false, cpu, st, target);
1279
1280 /* Park the stopper thread */
1281 stop_machine_park(cpu);
1282 return 0;
1283}
1284
1285static int takedown_cpu(unsigned int cpu)
1286{
1287 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1288 int err;
1289
1290 /* Park the smpboot threads */
1291 kthread_park(st->thread);
1292
1293 /*
1294 * Prevent irq alloc/free while the dying cpu reorganizes the
1295 * interrupt affinities.
1296 */
1297 irq_lock_sparse();
1298
1299 /*
1300 * So now all preempt/rcu users must observe !cpu_active().
1301 */
1302 err = stop_machine_cpuslocked(take_cpu_down, NULL, cpumask_of(cpu));
1303 if (err) {
1304 /* CPU refused to die */
1305 irq_unlock_sparse();
1306 /* Unpark the hotplug thread so we can rollback there */
1307 kthread_unpark(st->thread);
1308 return err;
1309 }
1310 BUG_ON(cpu_online(cpu));
1311
1312 /*
1313 * The teardown callback for CPUHP_AP_SCHED_STARTING will have removed
1314 * all runnable tasks from the CPU, there's only the idle task left now
1315 * that the migration thread is done doing the stop_machine thing.
1316 *
1317 * Wait for the stop thread to go away.
1318 */
1319 wait_for_ap_thread(st, false);
1320 BUG_ON(st->state != CPUHP_AP_IDLE_DEAD);
1321
1322 /* Interrupts are moved away from the dying cpu, reenable alloc/free */
1323 irq_unlock_sparse();
1324
1325 hotplug_cpu__broadcast_tick_pull(cpu);
1326 /* This actually kills the CPU. */
1327 __cpu_die(cpu);
1328
1329 cpuhp_bp_sync_dead(cpu);
1330
1331 tick_cleanup_dead_cpu(cpu);
1332
1333 /*
1334 * Callbacks must be re-integrated right away to the RCU state machine.
1335 * Otherwise an RCU callback could block a further teardown function
1336 * waiting for its completion.
1337 */
1338 rcutree_migrate_callbacks(cpu);
1339
1340 return 0;
1341}
1342
1343static void cpuhp_complete_idle_dead(void *arg)
1344{
1345 struct cpuhp_cpu_state *st = arg;
1346
1347 complete_ap_thread(st, false);
1348}
1349
1350void cpuhp_report_idle_dead(void)
1351{
1352 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
1353
1354 BUG_ON(st->state != CPUHP_AP_OFFLINE);
1355 tick_assert_timekeeping_handover();
1356 rcutree_report_cpu_dead();
1357 st->state = CPUHP_AP_IDLE_DEAD;
1358 /*
1359 * We cannot call complete after rcutree_report_cpu_dead() so we delegate it
1360 * to an online cpu.
1361 */
1362 smp_call_function_single(cpumask_first(cpu_online_mask),
1363 cpuhp_complete_idle_dead, st, 0);
1364}
1365
1366static int cpuhp_down_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
1367 enum cpuhp_state target)
1368{
1369 enum cpuhp_state prev_state = st->state;
1370 int ret = 0;
1371
1372 ret = cpuhp_invoke_callback_range(false, cpu, st, target);
1373 if (ret) {
1374 pr_debug("CPU DOWN failed (%d) CPU %u state %s (%d)\n",
1375 ret, cpu, cpuhp_get_step(st->state)->name,
1376 st->state);
1377
1378 cpuhp_reset_state(cpu, st, prev_state);
1379
1380 if (st->state < prev_state)
1381 WARN_ON(cpuhp_invoke_callback_range(true, cpu, st,
1382 prev_state));
1383 }
1384
1385 return ret;
1386}
1387
1388/* Requires cpu_add_remove_lock to be held */
1389static int __ref _cpu_down(unsigned int cpu, int tasks_frozen,
1390 enum cpuhp_state target)
1391{
1392 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1393 int prev_state, ret = 0;
1394
1395 if (num_online_cpus() == 1)
1396 return -EBUSY;
1397
1398 if (!cpu_present(cpu))
1399 return -EINVAL;
1400
1401 cpus_write_lock();
1402
1403 cpuhp_tasks_frozen = tasks_frozen;
1404
1405 prev_state = cpuhp_set_state(cpu, st, target);
1406 /*
1407 * If the current CPU state is in the range of the AP hotplug thread,
1408 * then we need to kick the thread.
1409 */
1410 if (st->state > CPUHP_TEARDOWN_CPU) {
1411 st->target = max((int)target, CPUHP_TEARDOWN_CPU);
1412 ret = cpuhp_kick_ap_work(cpu);
1413 /*
1414 * The AP side has done the error rollback already. Just
1415 * return the error code..
1416 */
1417 if (ret)
1418 goto out;
1419
1420 /*
1421 * We might have stopped still in the range of the AP hotplug
1422 * thread. Nothing to do anymore.
1423 */
1424 if (st->state > CPUHP_TEARDOWN_CPU)
1425 goto out;
1426
1427 st->target = target;
1428 }
1429 /*
1430 * The AP brought itself down to CPUHP_TEARDOWN_CPU. So we need
1431 * to do the further cleanups.
1432 */
1433 ret = cpuhp_down_callbacks(cpu, st, target);
1434 if (ret && st->state < prev_state) {
1435 if (st->state == CPUHP_TEARDOWN_CPU) {
1436 cpuhp_reset_state(cpu, st, prev_state);
1437 __cpuhp_kick_ap(st);
1438 } else {
1439 WARN(1, "DEAD callback error for CPU%d", cpu);
1440 }
1441 }
1442
1443out:
1444 cpus_write_unlock();
1445 /*
1446 * Do post unplug cleanup. This is still protected against
1447 * concurrent CPU hotplug via cpu_add_remove_lock.
1448 */
1449 lockup_detector_cleanup();
1450 arch_smt_update();
1451 return ret;
1452}
1453
1454struct cpu_down_work {
1455 unsigned int cpu;
1456 enum cpuhp_state target;
1457};
1458
1459static long __cpu_down_maps_locked(void *arg)
1460{
1461 struct cpu_down_work *work = arg;
1462
1463 return _cpu_down(work->cpu, 0, work->target);
1464}
1465
1466static int cpu_down_maps_locked(unsigned int cpu, enum cpuhp_state target)
1467{
1468 struct cpu_down_work work = { .cpu = cpu, .target = target, };
1469
1470 /*
1471 * If the platform does not support hotplug, report it explicitly to
1472 * differentiate it from a transient offlining failure.
1473 */
1474 if (cc_platform_has(CC_ATTR_HOTPLUG_DISABLED))
1475 return -EOPNOTSUPP;
1476 if (cpu_hotplug_disabled)
1477 return -EBUSY;
1478
1479 /*
1480 * Ensure that the control task does not run on the to be offlined
1481 * CPU to prevent a deadlock against cfs_b->period_timer.
1482 * Also keep at least one housekeeping cpu onlined to avoid generating
1483 * an empty sched_domain span.
1484 */
1485 for_each_cpu_and(cpu, cpu_online_mask, housekeeping_cpumask(HK_TYPE_DOMAIN)) {
1486 if (cpu != work.cpu)
1487 return work_on_cpu(cpu, __cpu_down_maps_locked, &work);
1488 }
1489 return -EBUSY;
1490}
1491
1492static int cpu_down(unsigned int cpu, enum cpuhp_state target)
1493{
1494 int err;
1495
1496 cpu_maps_update_begin();
1497 err = cpu_down_maps_locked(cpu, target);
1498 cpu_maps_update_done();
1499 return err;
1500}
1501
1502/**
1503 * cpu_device_down - Bring down a cpu device
1504 * @dev: Pointer to the cpu device to offline
1505 *
1506 * This function is meant to be used by device core cpu subsystem only.
1507 *
1508 * Other subsystems should use remove_cpu() instead.
1509 *
1510 * Return: %0 on success or a negative errno code
1511 */
1512int cpu_device_down(struct device *dev)
1513{
1514 return cpu_down(dev->id, CPUHP_OFFLINE);
1515}
1516
1517int remove_cpu(unsigned int cpu)
1518{
1519 int ret;
1520
1521 lock_device_hotplug();
1522 ret = device_offline(get_cpu_device(cpu));
1523 unlock_device_hotplug();
1524
1525 return ret;
1526}
1527EXPORT_SYMBOL_GPL(remove_cpu);
1528
1529void smp_shutdown_nonboot_cpus(unsigned int primary_cpu)
1530{
1531 unsigned int cpu;
1532 int error;
1533
1534 cpu_maps_update_begin();
1535
1536 /*
1537 * Make certain the cpu I'm about to reboot on is online.
1538 *
1539 * This is inline to what migrate_to_reboot_cpu() already do.
1540 */
1541 if (!cpu_online(primary_cpu))
1542 primary_cpu = cpumask_first(cpu_online_mask);
1543
1544 for_each_online_cpu(cpu) {
1545 if (cpu == primary_cpu)
1546 continue;
1547
1548 error = cpu_down_maps_locked(cpu, CPUHP_OFFLINE);
1549 if (error) {
1550 pr_err("Failed to offline CPU%d - error=%d",
1551 cpu, error);
1552 break;
1553 }
1554 }
1555
1556 /*
1557 * Ensure all but the reboot CPU are offline.
1558 */
1559 BUG_ON(num_online_cpus() > 1);
1560
1561 /*
1562 * Make sure the CPUs won't be enabled by someone else after this
1563 * point. Kexec will reboot to a new kernel shortly resetting
1564 * everything along the way.
1565 */
1566 cpu_hotplug_disabled++;
1567
1568 cpu_maps_update_done();
1569}
1570
1571#else
1572#define takedown_cpu NULL
1573#endif /*CONFIG_HOTPLUG_CPU*/
1574
1575/**
1576 * notify_cpu_starting(cpu) - Invoke the callbacks on the starting CPU
1577 * @cpu: cpu that just started
1578 *
1579 * It must be called by the arch code on the new cpu, before the new cpu
1580 * enables interrupts and before the "boot" cpu returns from __cpu_up().
1581 */
1582void notify_cpu_starting(unsigned int cpu)
1583{
1584 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1585 enum cpuhp_state target = min((int)st->target, CPUHP_AP_ONLINE);
1586
1587 rcutree_report_cpu_starting(cpu); /* Enables RCU usage on this CPU. */
1588 cpumask_set_cpu(cpu, &cpus_booted_once_mask);
1589
1590 /*
1591 * STARTING must not fail!
1592 */
1593 cpuhp_invoke_callback_range_nofail(true, cpu, st, target);
1594}
1595
1596/*
1597 * Called from the idle task. Wake up the controlling task which brings the
1598 * hotplug thread of the upcoming CPU up and then delegates the rest of the
1599 * online bringup to the hotplug thread.
1600 */
1601void cpuhp_online_idle(enum cpuhp_state state)
1602{
1603 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
1604
1605 /* Happens for the boot cpu */
1606 if (state != CPUHP_AP_ONLINE_IDLE)
1607 return;
1608
1609 cpuhp_ap_update_sync_state(SYNC_STATE_ONLINE);
1610
1611 /*
1612 * Unpark the stopper thread before we start the idle loop (and start
1613 * scheduling); this ensures the stopper task is always available.
1614 */
1615 stop_machine_unpark(smp_processor_id());
1616
1617 st->state = CPUHP_AP_ONLINE_IDLE;
1618 complete_ap_thread(st, true);
1619}
1620
1621/* Requires cpu_add_remove_lock to be held */
1622static int _cpu_up(unsigned int cpu, int tasks_frozen, enum cpuhp_state target)
1623{
1624 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1625 struct task_struct *idle;
1626 int ret = 0;
1627
1628 cpus_write_lock();
1629
1630 if (!cpu_present(cpu)) {
1631 ret = -EINVAL;
1632 goto out;
1633 }
1634
1635 /*
1636 * The caller of cpu_up() might have raced with another
1637 * caller. Nothing to do.
1638 */
1639 if (st->state >= target)
1640 goto out;
1641
1642 if (st->state == CPUHP_OFFLINE) {
1643 /* Let it fail before we try to bring the cpu up */
1644 idle = idle_thread_get(cpu);
1645 if (IS_ERR(idle)) {
1646 ret = PTR_ERR(idle);
1647 goto out;
1648 }
1649
1650 /*
1651 * Reset stale stack state from the last time this CPU was online.
1652 */
1653 scs_task_reset(idle);
1654 kasan_unpoison_task_stack(idle);
1655 }
1656
1657 cpuhp_tasks_frozen = tasks_frozen;
1658
1659 cpuhp_set_state(cpu, st, target);
1660 /*
1661 * If the current CPU state is in the range of the AP hotplug thread,
1662 * then we need to kick the thread once more.
1663 */
1664 if (st->state > CPUHP_BRINGUP_CPU) {
1665 ret = cpuhp_kick_ap_work(cpu);
1666 /*
1667 * The AP side has done the error rollback already. Just
1668 * return the error code..
1669 */
1670 if (ret)
1671 goto out;
1672 }
1673
1674 /*
1675 * Try to reach the target state. We max out on the BP at
1676 * CPUHP_BRINGUP_CPU. After that the AP hotplug thread is
1677 * responsible for bringing it up to the target state.
1678 */
1679 target = min((int)target, CPUHP_BRINGUP_CPU);
1680 ret = cpuhp_up_callbacks(cpu, st, target);
1681out:
1682 cpus_write_unlock();
1683 arch_smt_update();
1684 return ret;
1685}
1686
1687static int cpu_up(unsigned int cpu, enum cpuhp_state target)
1688{
1689 int err = 0;
1690
1691 if (!cpu_possible(cpu)) {
1692 pr_err("can't online cpu %d because it is not configured as may-hotadd at boot time\n",
1693 cpu);
1694 return -EINVAL;
1695 }
1696
1697 err = try_online_node(cpu_to_node(cpu));
1698 if (err)
1699 return err;
1700
1701 cpu_maps_update_begin();
1702
1703 if (cpu_hotplug_disabled) {
1704 err = -EBUSY;
1705 goto out;
1706 }
1707 if (!cpu_bootable(cpu)) {
1708 err = -EPERM;
1709 goto out;
1710 }
1711
1712 err = _cpu_up(cpu, 0, target);
1713out:
1714 cpu_maps_update_done();
1715 return err;
1716}
1717
1718/**
1719 * cpu_device_up - Bring up a cpu device
1720 * @dev: Pointer to the cpu device to online
1721 *
1722 * This function is meant to be used by device core cpu subsystem only.
1723 *
1724 * Other subsystems should use add_cpu() instead.
1725 *
1726 * Return: %0 on success or a negative errno code
1727 */
1728int cpu_device_up(struct device *dev)
1729{
1730 return cpu_up(dev->id, CPUHP_ONLINE);
1731}
1732
1733int add_cpu(unsigned int cpu)
1734{
1735 int ret;
1736
1737 lock_device_hotplug();
1738 ret = device_online(get_cpu_device(cpu));
1739 unlock_device_hotplug();
1740
1741 return ret;
1742}
1743EXPORT_SYMBOL_GPL(add_cpu);
1744
1745/**
1746 * bringup_hibernate_cpu - Bring up the CPU that we hibernated on
1747 * @sleep_cpu: The cpu we hibernated on and should be brought up.
1748 *
1749 * On some architectures like arm64, we can hibernate on any CPU, but on
1750 * wake up the CPU we hibernated on might be offline as a side effect of
1751 * using maxcpus= for example.
1752 *
1753 * Return: %0 on success or a negative errno code
1754 */
1755int bringup_hibernate_cpu(unsigned int sleep_cpu)
1756{
1757 int ret;
1758
1759 if (!cpu_online(sleep_cpu)) {
1760 pr_info("Hibernated on a CPU that is offline! Bringing CPU up.\n");
1761 ret = cpu_up(sleep_cpu, CPUHP_ONLINE);
1762 if (ret) {
1763 pr_err("Failed to bring hibernate-CPU up!\n");
1764 return ret;
1765 }
1766 }
1767 return 0;
1768}
1769
1770static void __init cpuhp_bringup_mask(const struct cpumask *mask, unsigned int ncpus,
1771 enum cpuhp_state target)
1772{
1773 unsigned int cpu;
1774
1775 for_each_cpu(cpu, mask) {
1776 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1777
1778 if (cpu_up(cpu, target) && can_rollback_cpu(st)) {
1779 /*
1780 * If this failed then cpu_up() might have only
1781 * rolled back to CPUHP_BP_KICK_AP for the final
1782 * online. Clean it up. NOOP if already rolled back.
1783 */
1784 WARN_ON(cpuhp_invoke_callback_range(false, cpu, st, CPUHP_OFFLINE));
1785 }
1786
1787 if (!--ncpus)
1788 break;
1789 }
1790}
1791
1792#ifdef CONFIG_HOTPLUG_PARALLEL
1793static bool __cpuhp_parallel_bringup __ro_after_init = true;
1794
1795static int __init parallel_bringup_parse_param(char *arg)
1796{
1797 return kstrtobool(arg, &__cpuhp_parallel_bringup);
1798}
1799early_param("cpuhp.parallel", parallel_bringup_parse_param);
1800
1801static inline bool cpuhp_smt_aware(void)
1802{
1803 return cpu_smt_max_threads > 1;
1804}
1805
1806static inline const struct cpumask *cpuhp_get_primary_thread_mask(void)
1807{
1808 return cpu_primary_thread_mask;
1809}
1810
1811/*
1812 * On architectures which have enabled parallel bringup this invokes all BP
1813 * prepare states for each of the to be onlined APs first. The last state
1814 * sends the startup IPI to the APs. The APs proceed through the low level
1815 * bringup code in parallel and then wait for the control CPU to release
1816 * them one by one for the final onlining procedure.
1817 *
1818 * This avoids waiting for each AP to respond to the startup IPI in
1819 * CPUHP_BRINGUP_CPU.
1820 */
1821static bool __init cpuhp_bringup_cpus_parallel(unsigned int ncpus)
1822{
1823 const struct cpumask *mask = cpu_present_mask;
1824
1825 if (__cpuhp_parallel_bringup)
1826 __cpuhp_parallel_bringup = arch_cpuhp_init_parallel_bringup();
1827 if (!__cpuhp_parallel_bringup)
1828 return false;
1829
1830 if (cpuhp_smt_aware()) {
1831 const struct cpumask *pmask = cpuhp_get_primary_thread_mask();
1832 static struct cpumask tmp_mask __initdata;
1833
1834 /*
1835 * X86 requires to prevent that SMT siblings stopped while
1836 * the primary thread does a microcode update for various
1837 * reasons. Bring the primary threads up first.
1838 */
1839 cpumask_and(&tmp_mask, mask, pmask);
1840 cpuhp_bringup_mask(&tmp_mask, ncpus, CPUHP_BP_KICK_AP);
1841 cpuhp_bringup_mask(&tmp_mask, ncpus, CPUHP_ONLINE);
1842 /* Account for the online CPUs */
1843 ncpus -= num_online_cpus();
1844 if (!ncpus)
1845 return true;
1846 /* Create the mask for secondary CPUs */
1847 cpumask_andnot(&tmp_mask, mask, pmask);
1848 mask = &tmp_mask;
1849 }
1850
1851 /* Bring the not-yet started CPUs up */
1852 cpuhp_bringup_mask(mask, ncpus, CPUHP_BP_KICK_AP);
1853 cpuhp_bringup_mask(mask, ncpus, CPUHP_ONLINE);
1854 return true;
1855}
1856#else
1857static inline bool cpuhp_bringup_cpus_parallel(unsigned int ncpus) { return false; }
1858#endif /* CONFIG_HOTPLUG_PARALLEL */
1859
1860void __init bringup_nonboot_cpus(unsigned int max_cpus)
1861{
1862 if (!max_cpus)
1863 return;
1864
1865 /* Try parallel bringup optimization if enabled */
1866 if (cpuhp_bringup_cpus_parallel(max_cpus))
1867 return;
1868
1869 /* Full per CPU serialized bringup */
1870 cpuhp_bringup_mask(cpu_present_mask, max_cpus, CPUHP_ONLINE);
1871}
1872
1873#ifdef CONFIG_PM_SLEEP_SMP
1874static cpumask_var_t frozen_cpus;
1875
1876int freeze_secondary_cpus(int primary)
1877{
1878 int cpu, error = 0;
1879
1880 cpu_maps_update_begin();
1881 if (primary == -1) {
1882 primary = cpumask_first(cpu_online_mask);
1883 if (!housekeeping_cpu(primary, HK_TYPE_TIMER))
1884 primary = housekeeping_any_cpu(HK_TYPE_TIMER);
1885 } else {
1886 if (!cpu_online(primary))
1887 primary = cpumask_first(cpu_online_mask);
1888 }
1889
1890 /*
1891 * We take down all of the non-boot CPUs in one shot to avoid races
1892 * with the userspace trying to use the CPU hotplug at the same time
1893 */
1894 cpumask_clear(frozen_cpus);
1895
1896 pr_info("Disabling non-boot CPUs ...\n");
1897 for_each_online_cpu(cpu) {
1898 if (cpu == primary)
1899 continue;
1900
1901 if (pm_wakeup_pending()) {
1902 pr_info("Wakeup pending. Abort CPU freeze\n");
1903 error = -EBUSY;
1904 break;
1905 }
1906
1907 trace_suspend_resume(TPS("CPU_OFF"), cpu, true);
1908 error = _cpu_down(cpu, 1, CPUHP_OFFLINE);
1909 trace_suspend_resume(TPS("CPU_OFF"), cpu, false);
1910 if (!error)
1911 cpumask_set_cpu(cpu, frozen_cpus);
1912 else {
1913 pr_err("Error taking CPU%d down: %d\n", cpu, error);
1914 break;
1915 }
1916 }
1917
1918 if (!error)
1919 BUG_ON(num_online_cpus() > 1);
1920 else
1921 pr_err("Non-boot CPUs are not disabled\n");
1922
1923 /*
1924 * Make sure the CPUs won't be enabled by someone else. We need to do
1925 * this even in case of failure as all freeze_secondary_cpus() users are
1926 * supposed to do thaw_secondary_cpus() on the failure path.
1927 */
1928 cpu_hotplug_disabled++;
1929
1930 cpu_maps_update_done();
1931 return error;
1932}
1933
1934void __weak arch_thaw_secondary_cpus_begin(void)
1935{
1936}
1937
1938void __weak arch_thaw_secondary_cpus_end(void)
1939{
1940}
1941
1942void thaw_secondary_cpus(void)
1943{
1944 int cpu, error;
1945
1946 /* Allow everyone to use the CPU hotplug again */
1947 cpu_maps_update_begin();
1948 __cpu_hotplug_enable();
1949 if (cpumask_empty(frozen_cpus))
1950 goto out;
1951
1952 pr_info("Enabling non-boot CPUs ...\n");
1953
1954 arch_thaw_secondary_cpus_begin();
1955
1956 for_each_cpu(cpu, frozen_cpus) {
1957 trace_suspend_resume(TPS("CPU_ON"), cpu, true);
1958 error = _cpu_up(cpu, 1, CPUHP_ONLINE);
1959 trace_suspend_resume(TPS("CPU_ON"), cpu, false);
1960 if (!error) {
1961 pr_info("CPU%d is up\n", cpu);
1962 continue;
1963 }
1964 pr_warn("Error taking CPU%d up: %d\n", cpu, error);
1965 }
1966
1967 arch_thaw_secondary_cpus_end();
1968
1969 cpumask_clear(frozen_cpus);
1970out:
1971 cpu_maps_update_done();
1972}
1973
1974static int __init alloc_frozen_cpus(void)
1975{
1976 if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
1977 return -ENOMEM;
1978 return 0;
1979}
1980core_initcall(alloc_frozen_cpus);
1981
1982/*
1983 * When callbacks for CPU hotplug notifications are being executed, we must
1984 * ensure that the state of the system with respect to the tasks being frozen
1985 * or not, as reported by the notification, remains unchanged *throughout the
1986 * duration* of the execution of the callbacks.
1987 * Hence we need to prevent the freezer from racing with regular CPU hotplug.
1988 *
1989 * This synchronization is implemented by mutually excluding regular CPU
1990 * hotplug and Suspend/Hibernate call paths by hooking onto the Suspend/
1991 * Hibernate notifications.
1992 */
1993static int
1994cpu_hotplug_pm_callback(struct notifier_block *nb,
1995 unsigned long action, void *ptr)
1996{
1997 switch (action) {
1998
1999 case PM_SUSPEND_PREPARE:
2000 case PM_HIBERNATION_PREPARE:
2001 cpu_hotplug_disable();
2002 break;
2003
2004 case PM_POST_SUSPEND:
2005 case PM_POST_HIBERNATION:
2006 cpu_hotplug_enable();
2007 break;
2008
2009 default:
2010 return NOTIFY_DONE;
2011 }
2012
2013 return NOTIFY_OK;
2014}
2015
2016
2017static int __init cpu_hotplug_pm_sync_init(void)
2018{
2019 /*
2020 * cpu_hotplug_pm_callback has higher priority than x86
2021 * bsp_pm_callback which depends on cpu_hotplug_pm_callback
2022 * to disable cpu hotplug to avoid cpu hotplug race.
2023 */
2024 pm_notifier(cpu_hotplug_pm_callback, 0);
2025 return 0;
2026}
2027core_initcall(cpu_hotplug_pm_sync_init);
2028
2029#endif /* CONFIG_PM_SLEEP_SMP */
2030
2031int __boot_cpu_id;
2032
2033#endif /* CONFIG_SMP */
2034
2035/* Boot processor state steps */
2036static struct cpuhp_step cpuhp_hp_states[] = {
2037 [CPUHP_OFFLINE] = {
2038 .name = "offline",
2039 .startup.single = NULL,
2040 .teardown.single = NULL,
2041 },
2042#ifdef CONFIG_SMP
2043 [CPUHP_CREATE_THREADS]= {
2044 .name = "threads:prepare",
2045 .startup.single = smpboot_create_threads,
2046 .teardown.single = NULL,
2047 .cant_stop = true,
2048 },
2049 [CPUHP_PERF_PREPARE] = {
2050 .name = "perf:prepare",
2051 .startup.single = perf_event_init_cpu,
2052 .teardown.single = perf_event_exit_cpu,
2053 },
2054 [CPUHP_RANDOM_PREPARE] = {
2055 .name = "random:prepare",
2056 .startup.single = random_prepare_cpu,
2057 .teardown.single = NULL,
2058 },
2059 [CPUHP_WORKQUEUE_PREP] = {
2060 .name = "workqueue:prepare",
2061 .startup.single = workqueue_prepare_cpu,
2062 .teardown.single = NULL,
2063 },
2064 [CPUHP_HRTIMERS_PREPARE] = {
2065 .name = "hrtimers:prepare",
2066 .startup.single = hrtimers_prepare_cpu,
2067 .teardown.single = NULL,
2068 },
2069 [CPUHP_SMPCFD_PREPARE] = {
2070 .name = "smpcfd:prepare",
2071 .startup.single = smpcfd_prepare_cpu,
2072 .teardown.single = smpcfd_dead_cpu,
2073 },
2074 [CPUHP_RELAY_PREPARE] = {
2075 .name = "relay:prepare",
2076 .startup.single = relay_prepare_cpu,
2077 .teardown.single = NULL,
2078 },
2079 [CPUHP_RCUTREE_PREP] = {
2080 .name = "RCU/tree:prepare",
2081 .startup.single = rcutree_prepare_cpu,
2082 .teardown.single = rcutree_dead_cpu,
2083 },
2084 /*
2085 * On the tear-down path, timers_dead_cpu() must be invoked
2086 * before blk_mq_queue_reinit_notify() from notify_dead(),
2087 * otherwise a RCU stall occurs.
2088 */
2089 [CPUHP_TIMERS_PREPARE] = {
2090 .name = "timers:prepare",
2091 .startup.single = timers_prepare_cpu,
2092 .teardown.single = timers_dead_cpu,
2093 },
2094
2095#ifdef CONFIG_HOTPLUG_SPLIT_STARTUP
2096 /*
2097 * Kicks the AP alive. AP will wait in cpuhp_ap_sync_alive() until
2098 * the next step will release it.
2099 */
2100 [CPUHP_BP_KICK_AP] = {
2101 .name = "cpu:kick_ap",
2102 .startup.single = cpuhp_kick_ap_alive,
2103 },
2104
2105 /*
2106 * Waits for the AP to reach cpuhp_ap_sync_alive() and then
2107 * releases it for the complete bringup.
2108 */
2109 [CPUHP_BRINGUP_CPU] = {
2110 .name = "cpu:bringup",
2111 .startup.single = cpuhp_bringup_ap,
2112 .teardown.single = finish_cpu,
2113 .cant_stop = true,
2114 },
2115#else
2116 /*
2117 * All-in-one CPU bringup state which includes the kick alive.
2118 */
2119 [CPUHP_BRINGUP_CPU] = {
2120 .name = "cpu:bringup",
2121 .startup.single = bringup_cpu,
2122 .teardown.single = finish_cpu,
2123 .cant_stop = true,
2124 },
2125#endif
2126 /* Final state before CPU kills itself */
2127 [CPUHP_AP_IDLE_DEAD] = {
2128 .name = "idle:dead",
2129 },
2130 /*
2131 * Last state before CPU enters the idle loop to die. Transient state
2132 * for synchronization.
2133 */
2134 [CPUHP_AP_OFFLINE] = {
2135 .name = "ap:offline",
2136 .cant_stop = true,
2137 },
2138 /* First state is scheduler control. Interrupts are disabled */
2139 [CPUHP_AP_SCHED_STARTING] = {
2140 .name = "sched:starting",
2141 .startup.single = sched_cpu_starting,
2142 .teardown.single = sched_cpu_dying,
2143 },
2144 [CPUHP_AP_RCUTREE_DYING] = {
2145 .name = "RCU/tree:dying",
2146 .startup.single = NULL,
2147 .teardown.single = rcutree_dying_cpu,
2148 },
2149 [CPUHP_AP_SMPCFD_DYING] = {
2150 .name = "smpcfd:dying",
2151 .startup.single = NULL,
2152 .teardown.single = smpcfd_dying_cpu,
2153 },
2154 [CPUHP_AP_HRTIMERS_DYING] = {
2155 .name = "hrtimers:dying",
2156 .startup.single = NULL,
2157 .teardown.single = hrtimers_cpu_dying,
2158 },
2159 [CPUHP_AP_TICK_DYING] = {
2160 .name = "tick:dying",
2161 .startup.single = NULL,
2162 .teardown.single = tick_cpu_dying,
2163 },
2164 /* Entry state on starting. Interrupts enabled from here on. Transient
2165 * state for synchronsization */
2166 [CPUHP_AP_ONLINE] = {
2167 .name = "ap:online",
2168 },
2169 /*
2170 * Handled on control processor until the plugged processor manages
2171 * this itself.
2172 */
2173 [CPUHP_TEARDOWN_CPU] = {
2174 .name = "cpu:teardown",
2175 .startup.single = NULL,
2176 .teardown.single = takedown_cpu,
2177 .cant_stop = true,
2178 },
2179
2180 [CPUHP_AP_SCHED_WAIT_EMPTY] = {
2181 .name = "sched:waitempty",
2182 .startup.single = NULL,
2183 .teardown.single = sched_cpu_wait_empty,
2184 },
2185
2186 /* Handle smpboot threads park/unpark */
2187 [CPUHP_AP_SMPBOOT_THREADS] = {
2188 .name = "smpboot/threads:online",
2189 .startup.single = smpboot_unpark_threads,
2190 .teardown.single = smpboot_park_threads,
2191 },
2192 [CPUHP_AP_IRQ_AFFINITY_ONLINE] = {
2193 .name = "irq/affinity:online",
2194 .startup.single = irq_affinity_online_cpu,
2195 .teardown.single = NULL,
2196 },
2197 [CPUHP_AP_PERF_ONLINE] = {
2198 .name = "perf:online",
2199 .startup.single = perf_event_init_cpu,
2200 .teardown.single = perf_event_exit_cpu,
2201 },
2202 [CPUHP_AP_WATCHDOG_ONLINE] = {
2203 .name = "lockup_detector:online",
2204 .startup.single = lockup_detector_online_cpu,
2205 .teardown.single = lockup_detector_offline_cpu,
2206 },
2207 [CPUHP_AP_WORKQUEUE_ONLINE] = {
2208 .name = "workqueue:online",
2209 .startup.single = workqueue_online_cpu,
2210 .teardown.single = workqueue_offline_cpu,
2211 },
2212 [CPUHP_AP_RANDOM_ONLINE] = {
2213 .name = "random:online",
2214 .startup.single = random_online_cpu,
2215 .teardown.single = NULL,
2216 },
2217 [CPUHP_AP_RCUTREE_ONLINE] = {
2218 .name = "RCU/tree:online",
2219 .startup.single = rcutree_online_cpu,
2220 .teardown.single = rcutree_offline_cpu,
2221 },
2222#endif
2223 /*
2224 * The dynamically registered state space is here
2225 */
2226
2227#ifdef CONFIG_SMP
2228 /* Last state is scheduler control setting the cpu active */
2229 [CPUHP_AP_ACTIVE] = {
2230 .name = "sched:active",
2231 .startup.single = sched_cpu_activate,
2232 .teardown.single = sched_cpu_deactivate,
2233 },
2234#endif
2235
2236 /* CPU is fully up and running. */
2237 [CPUHP_ONLINE] = {
2238 .name = "online",
2239 .startup.single = NULL,
2240 .teardown.single = NULL,
2241 },
2242};
2243
2244/* Sanity check for callbacks */
2245static int cpuhp_cb_check(enum cpuhp_state state)
2246{
2247 if (state <= CPUHP_OFFLINE || state >= CPUHP_ONLINE)
2248 return -EINVAL;
2249 return 0;
2250}
2251
2252/*
2253 * Returns a free for dynamic slot assignment of the Online state. The states
2254 * are protected by the cpuhp_slot_states mutex and an empty slot is identified
2255 * by having no name assigned.
2256 */
2257static int cpuhp_reserve_state(enum cpuhp_state state)
2258{
2259 enum cpuhp_state i, end;
2260 struct cpuhp_step *step;
2261
2262 switch (state) {
2263 case CPUHP_AP_ONLINE_DYN:
2264 step = cpuhp_hp_states + CPUHP_AP_ONLINE_DYN;
2265 end = CPUHP_AP_ONLINE_DYN_END;
2266 break;
2267 case CPUHP_BP_PREPARE_DYN:
2268 step = cpuhp_hp_states + CPUHP_BP_PREPARE_DYN;
2269 end = CPUHP_BP_PREPARE_DYN_END;
2270 break;
2271 default:
2272 return -EINVAL;
2273 }
2274
2275 for (i = state; i <= end; i++, step++) {
2276 if (!step->name)
2277 return i;
2278 }
2279 WARN(1, "No more dynamic states available for CPU hotplug\n");
2280 return -ENOSPC;
2281}
2282
2283static int cpuhp_store_callbacks(enum cpuhp_state state, const char *name,
2284 int (*startup)(unsigned int cpu),
2285 int (*teardown)(unsigned int cpu),
2286 bool multi_instance)
2287{
2288 /* (Un)Install the callbacks for further cpu hotplug operations */
2289 struct cpuhp_step *sp;
2290 int ret = 0;
2291
2292 /*
2293 * If name is NULL, then the state gets removed.
2294 *
2295 * CPUHP_AP_ONLINE_DYN and CPUHP_BP_PREPARE_DYN are handed out on
2296 * the first allocation from these dynamic ranges, so the removal
2297 * would trigger a new allocation and clear the wrong (already
2298 * empty) state, leaving the callbacks of the to be cleared state
2299 * dangling, which causes wreckage on the next hotplug operation.
2300 */
2301 if (name && (state == CPUHP_AP_ONLINE_DYN ||
2302 state == CPUHP_BP_PREPARE_DYN)) {
2303 ret = cpuhp_reserve_state(state);
2304 if (ret < 0)
2305 return ret;
2306 state = ret;
2307 }
2308 sp = cpuhp_get_step(state);
2309 if (name && sp->name)
2310 return -EBUSY;
2311
2312 sp->startup.single = startup;
2313 sp->teardown.single = teardown;
2314 sp->name = name;
2315 sp->multi_instance = multi_instance;
2316 INIT_HLIST_HEAD(&sp->list);
2317 return ret;
2318}
2319
2320static void *cpuhp_get_teardown_cb(enum cpuhp_state state)
2321{
2322 return cpuhp_get_step(state)->teardown.single;
2323}
2324
2325/*
2326 * Call the startup/teardown function for a step either on the AP or
2327 * on the current CPU.
2328 */
2329static int cpuhp_issue_call(int cpu, enum cpuhp_state state, bool bringup,
2330 struct hlist_node *node)
2331{
2332 struct cpuhp_step *sp = cpuhp_get_step(state);
2333 int ret;
2334
2335 /*
2336 * If there's nothing to do, we done.
2337 * Relies on the union for multi_instance.
2338 */
2339 if (cpuhp_step_empty(bringup, sp))
2340 return 0;
2341 /*
2342 * The non AP bound callbacks can fail on bringup. On teardown
2343 * e.g. module removal we crash for now.
2344 */
2345#ifdef CONFIG_SMP
2346 if (cpuhp_is_ap_state(state))
2347 ret = cpuhp_invoke_ap_callback(cpu, state, bringup, node);
2348 else
2349 ret = cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
2350#else
2351 ret = cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
2352#endif
2353 BUG_ON(ret && !bringup);
2354 return ret;
2355}
2356
2357/*
2358 * Called from __cpuhp_setup_state on a recoverable failure.
2359 *
2360 * Note: The teardown callbacks for rollback are not allowed to fail!
2361 */
2362static void cpuhp_rollback_install(int failedcpu, enum cpuhp_state state,
2363 struct hlist_node *node)
2364{
2365 int cpu;
2366
2367 /* Roll back the already executed steps on the other cpus */
2368 for_each_present_cpu(cpu) {
2369 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
2370 int cpustate = st->state;
2371
2372 if (cpu >= failedcpu)
2373 break;
2374
2375 /* Did we invoke the startup call on that cpu ? */
2376 if (cpustate >= state)
2377 cpuhp_issue_call(cpu, state, false, node);
2378 }
2379}
2380
2381int __cpuhp_state_add_instance_cpuslocked(enum cpuhp_state state,
2382 struct hlist_node *node,
2383 bool invoke)
2384{
2385 struct cpuhp_step *sp;
2386 int cpu;
2387 int ret;
2388
2389 lockdep_assert_cpus_held();
2390
2391 sp = cpuhp_get_step(state);
2392 if (sp->multi_instance == false)
2393 return -EINVAL;
2394
2395 mutex_lock(&cpuhp_state_mutex);
2396
2397 if (!invoke || !sp->startup.multi)
2398 goto add_node;
2399
2400 /*
2401 * Try to call the startup callback for each present cpu
2402 * depending on the hotplug state of the cpu.
2403 */
2404 for_each_present_cpu(cpu) {
2405 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
2406 int cpustate = st->state;
2407
2408 if (cpustate < state)
2409 continue;
2410
2411 ret = cpuhp_issue_call(cpu, state, true, node);
2412 if (ret) {
2413 if (sp->teardown.multi)
2414 cpuhp_rollback_install(cpu, state, node);
2415 goto unlock;
2416 }
2417 }
2418add_node:
2419 ret = 0;
2420 hlist_add_head(node, &sp->list);
2421unlock:
2422 mutex_unlock(&cpuhp_state_mutex);
2423 return ret;
2424}
2425
2426int __cpuhp_state_add_instance(enum cpuhp_state state, struct hlist_node *node,
2427 bool invoke)
2428{
2429 int ret;
2430
2431 cpus_read_lock();
2432 ret = __cpuhp_state_add_instance_cpuslocked(state, node, invoke);
2433 cpus_read_unlock();
2434 return ret;
2435}
2436EXPORT_SYMBOL_GPL(__cpuhp_state_add_instance);
2437
2438/**
2439 * __cpuhp_setup_state_cpuslocked - Setup the callbacks for an hotplug machine state
2440 * @state: The state to setup
2441 * @name: Name of the step
2442 * @invoke: If true, the startup function is invoked for cpus where
2443 * cpu state >= @state
2444 * @startup: startup callback function
2445 * @teardown: teardown callback function
2446 * @multi_instance: State is set up for multiple instances which get
2447 * added afterwards.
2448 *
2449 * The caller needs to hold cpus read locked while calling this function.
2450 * Return:
2451 * On success:
2452 * Positive state number if @state is CPUHP_AP_ONLINE_DYN or CPUHP_BP_PREPARE_DYN;
2453 * 0 for all other states
2454 * On failure: proper (negative) error code
2455 */
2456int __cpuhp_setup_state_cpuslocked(enum cpuhp_state state,
2457 const char *name, bool invoke,
2458 int (*startup)(unsigned int cpu),
2459 int (*teardown)(unsigned int cpu),
2460 bool multi_instance)
2461{
2462 int cpu, ret = 0;
2463 bool dynstate;
2464
2465 lockdep_assert_cpus_held();
2466
2467 if (cpuhp_cb_check(state) || !name)
2468 return -EINVAL;
2469
2470 mutex_lock(&cpuhp_state_mutex);
2471
2472 ret = cpuhp_store_callbacks(state, name, startup, teardown,
2473 multi_instance);
2474
2475 dynstate = state == CPUHP_AP_ONLINE_DYN || state == CPUHP_BP_PREPARE_DYN;
2476 if (ret > 0 && dynstate) {
2477 state = ret;
2478 ret = 0;
2479 }
2480
2481 if (ret || !invoke || !startup)
2482 goto out;
2483
2484 /*
2485 * Try to call the startup callback for each present cpu
2486 * depending on the hotplug state of the cpu.
2487 */
2488 for_each_present_cpu(cpu) {
2489 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
2490 int cpustate = st->state;
2491
2492 if (cpustate < state)
2493 continue;
2494
2495 ret = cpuhp_issue_call(cpu, state, true, NULL);
2496 if (ret) {
2497 if (teardown)
2498 cpuhp_rollback_install(cpu, state, NULL);
2499 cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
2500 goto out;
2501 }
2502 }
2503out:
2504 mutex_unlock(&cpuhp_state_mutex);
2505 /*
2506 * If the requested state is CPUHP_AP_ONLINE_DYN or CPUHP_BP_PREPARE_DYN,
2507 * return the dynamically allocated state in case of success.
2508 */
2509 if (!ret && dynstate)
2510 return state;
2511 return ret;
2512}
2513EXPORT_SYMBOL(__cpuhp_setup_state_cpuslocked);
2514
2515int __cpuhp_setup_state(enum cpuhp_state state,
2516 const char *name, bool invoke,
2517 int (*startup)(unsigned int cpu),
2518 int (*teardown)(unsigned int cpu),
2519 bool multi_instance)
2520{
2521 int ret;
2522
2523 cpus_read_lock();
2524 ret = __cpuhp_setup_state_cpuslocked(state, name, invoke, startup,
2525 teardown, multi_instance);
2526 cpus_read_unlock();
2527 return ret;
2528}
2529EXPORT_SYMBOL(__cpuhp_setup_state);
2530
2531int __cpuhp_state_remove_instance(enum cpuhp_state state,
2532 struct hlist_node *node, bool invoke)
2533{
2534 struct cpuhp_step *sp = cpuhp_get_step(state);
2535 int cpu;
2536
2537 BUG_ON(cpuhp_cb_check(state));
2538
2539 if (!sp->multi_instance)
2540 return -EINVAL;
2541
2542 cpus_read_lock();
2543 mutex_lock(&cpuhp_state_mutex);
2544
2545 if (!invoke || !cpuhp_get_teardown_cb(state))
2546 goto remove;
2547 /*
2548 * Call the teardown callback for each present cpu depending
2549 * on the hotplug state of the cpu. This function is not
2550 * allowed to fail currently!
2551 */
2552 for_each_present_cpu(cpu) {
2553 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
2554 int cpustate = st->state;
2555
2556 if (cpustate >= state)
2557 cpuhp_issue_call(cpu, state, false, node);
2558 }
2559
2560remove:
2561 hlist_del(node);
2562 mutex_unlock(&cpuhp_state_mutex);
2563 cpus_read_unlock();
2564
2565 return 0;
2566}
2567EXPORT_SYMBOL_GPL(__cpuhp_state_remove_instance);
2568
2569/**
2570 * __cpuhp_remove_state_cpuslocked - Remove the callbacks for an hotplug machine state
2571 * @state: The state to remove
2572 * @invoke: If true, the teardown function is invoked for cpus where
2573 * cpu state >= @state
2574 *
2575 * The caller needs to hold cpus read locked while calling this function.
2576 * The teardown callback is currently not allowed to fail. Think
2577 * about module removal!
2578 */
2579void __cpuhp_remove_state_cpuslocked(enum cpuhp_state state, bool invoke)
2580{
2581 struct cpuhp_step *sp = cpuhp_get_step(state);
2582 int cpu;
2583
2584 BUG_ON(cpuhp_cb_check(state));
2585
2586 lockdep_assert_cpus_held();
2587
2588 mutex_lock(&cpuhp_state_mutex);
2589 if (sp->multi_instance) {
2590 WARN(!hlist_empty(&sp->list),
2591 "Error: Removing state %d which has instances left.\n",
2592 state);
2593 goto remove;
2594 }
2595
2596 if (!invoke || !cpuhp_get_teardown_cb(state))
2597 goto remove;
2598
2599 /*
2600 * Call the teardown callback for each present cpu depending
2601 * on the hotplug state of the cpu. This function is not
2602 * allowed to fail currently!
2603 */
2604 for_each_present_cpu(cpu) {
2605 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
2606 int cpustate = st->state;
2607
2608 if (cpustate >= state)
2609 cpuhp_issue_call(cpu, state, false, NULL);
2610 }
2611remove:
2612 cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
2613 mutex_unlock(&cpuhp_state_mutex);
2614}
2615EXPORT_SYMBOL(__cpuhp_remove_state_cpuslocked);
2616
2617void __cpuhp_remove_state(enum cpuhp_state state, bool invoke)
2618{
2619 cpus_read_lock();
2620 __cpuhp_remove_state_cpuslocked(state, invoke);
2621 cpus_read_unlock();
2622}
2623EXPORT_SYMBOL(__cpuhp_remove_state);
2624
2625#ifdef CONFIG_HOTPLUG_SMT
2626static void cpuhp_offline_cpu_device(unsigned int cpu)
2627{
2628 struct device *dev = get_cpu_device(cpu);
2629
2630 dev->offline = true;
2631 /* Tell user space about the state change */
2632 kobject_uevent(&dev->kobj, KOBJ_OFFLINE);
2633}
2634
2635static void cpuhp_online_cpu_device(unsigned int cpu)
2636{
2637 struct device *dev = get_cpu_device(cpu);
2638
2639 dev->offline = false;
2640 /* Tell user space about the state change */
2641 kobject_uevent(&dev->kobj, KOBJ_ONLINE);
2642}
2643
2644int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval)
2645{
2646 int cpu, ret = 0;
2647
2648 cpu_maps_update_begin();
2649 for_each_online_cpu(cpu) {
2650 if (topology_is_primary_thread(cpu))
2651 continue;
2652 /*
2653 * Disable can be called with CPU_SMT_ENABLED when changing
2654 * from a higher to lower number of SMT threads per core.
2655 */
2656 if (ctrlval == CPU_SMT_ENABLED && cpu_smt_thread_allowed(cpu))
2657 continue;
2658 ret = cpu_down_maps_locked(cpu, CPUHP_OFFLINE);
2659 if (ret)
2660 break;
2661 /*
2662 * As this needs to hold the cpu maps lock it's impossible
2663 * to call device_offline() because that ends up calling
2664 * cpu_down() which takes cpu maps lock. cpu maps lock
2665 * needs to be held as this might race against in kernel
2666 * abusers of the hotplug machinery (thermal management).
2667 *
2668 * So nothing would update device:offline state. That would
2669 * leave the sysfs entry stale and prevent onlining after
2670 * smt control has been changed to 'off' again. This is
2671 * called under the sysfs hotplug lock, so it is properly
2672 * serialized against the regular offline usage.
2673 */
2674 cpuhp_offline_cpu_device(cpu);
2675 }
2676 if (!ret)
2677 cpu_smt_control = ctrlval;
2678 cpu_maps_update_done();
2679 return ret;
2680}
2681
2682int cpuhp_smt_enable(void)
2683{
2684 int cpu, ret = 0;
2685
2686 cpu_maps_update_begin();
2687 cpu_smt_control = CPU_SMT_ENABLED;
2688 for_each_present_cpu(cpu) {
2689 /* Skip online CPUs and CPUs on offline nodes */
2690 if (cpu_online(cpu) || !node_online(cpu_to_node(cpu)))
2691 continue;
2692 if (!cpu_smt_thread_allowed(cpu))
2693 continue;
2694 ret = _cpu_up(cpu, 0, CPUHP_ONLINE);
2695 if (ret)
2696 break;
2697 /* See comment in cpuhp_smt_disable() */
2698 cpuhp_online_cpu_device(cpu);
2699 }
2700 cpu_maps_update_done();
2701 return ret;
2702}
2703#endif
2704
2705#if defined(CONFIG_SYSFS) && defined(CONFIG_HOTPLUG_CPU)
2706static ssize_t state_show(struct device *dev,
2707 struct device_attribute *attr, char *buf)
2708{
2709 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2710
2711 return sprintf(buf, "%d\n", st->state);
2712}
2713static DEVICE_ATTR_RO(state);
2714
2715static ssize_t target_store(struct device *dev, struct device_attribute *attr,
2716 const char *buf, size_t count)
2717{
2718 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2719 struct cpuhp_step *sp;
2720 int target, ret;
2721
2722 ret = kstrtoint(buf, 10, &target);
2723 if (ret)
2724 return ret;
2725
2726#ifdef CONFIG_CPU_HOTPLUG_STATE_CONTROL
2727 if (target < CPUHP_OFFLINE || target > CPUHP_ONLINE)
2728 return -EINVAL;
2729#else
2730 if (target != CPUHP_OFFLINE && target != CPUHP_ONLINE)
2731 return -EINVAL;
2732#endif
2733
2734 ret = lock_device_hotplug_sysfs();
2735 if (ret)
2736 return ret;
2737
2738 mutex_lock(&cpuhp_state_mutex);
2739 sp = cpuhp_get_step(target);
2740 ret = !sp->name || sp->cant_stop ? -EINVAL : 0;
2741 mutex_unlock(&cpuhp_state_mutex);
2742 if (ret)
2743 goto out;
2744
2745 if (st->state < target)
2746 ret = cpu_up(dev->id, target);
2747 else if (st->state > target)
2748 ret = cpu_down(dev->id, target);
2749 else if (WARN_ON(st->target != target))
2750 st->target = target;
2751out:
2752 unlock_device_hotplug();
2753 return ret ? ret : count;
2754}
2755
2756static ssize_t target_show(struct device *dev,
2757 struct device_attribute *attr, char *buf)
2758{
2759 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2760
2761 return sprintf(buf, "%d\n", st->target);
2762}
2763static DEVICE_ATTR_RW(target);
2764
2765static ssize_t fail_store(struct device *dev, struct device_attribute *attr,
2766 const char *buf, size_t count)
2767{
2768 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2769 struct cpuhp_step *sp;
2770 int fail, ret;
2771
2772 ret = kstrtoint(buf, 10, &fail);
2773 if (ret)
2774 return ret;
2775
2776 if (fail == CPUHP_INVALID) {
2777 st->fail = fail;
2778 return count;
2779 }
2780
2781 if (fail < CPUHP_OFFLINE || fail > CPUHP_ONLINE)
2782 return -EINVAL;
2783
2784 /*
2785 * Cannot fail STARTING/DYING callbacks.
2786 */
2787 if (cpuhp_is_atomic_state(fail))
2788 return -EINVAL;
2789
2790 /*
2791 * DEAD callbacks cannot fail...
2792 * ... neither can CPUHP_BRINGUP_CPU during hotunplug. The latter
2793 * triggering STARTING callbacks, a failure in this state would
2794 * hinder rollback.
2795 */
2796 if (fail <= CPUHP_BRINGUP_CPU && st->state > CPUHP_BRINGUP_CPU)
2797 return -EINVAL;
2798
2799 /*
2800 * Cannot fail anything that doesn't have callbacks.
2801 */
2802 mutex_lock(&cpuhp_state_mutex);
2803 sp = cpuhp_get_step(fail);
2804 if (!sp->startup.single && !sp->teardown.single)
2805 ret = -EINVAL;
2806 mutex_unlock(&cpuhp_state_mutex);
2807 if (ret)
2808 return ret;
2809
2810 st->fail = fail;
2811
2812 return count;
2813}
2814
2815static ssize_t fail_show(struct device *dev,
2816 struct device_attribute *attr, char *buf)
2817{
2818 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2819
2820 return sprintf(buf, "%d\n", st->fail);
2821}
2822
2823static DEVICE_ATTR_RW(fail);
2824
2825static struct attribute *cpuhp_cpu_attrs[] = {
2826 &dev_attr_state.attr,
2827 &dev_attr_target.attr,
2828 &dev_attr_fail.attr,
2829 NULL
2830};
2831
2832static const struct attribute_group cpuhp_cpu_attr_group = {
2833 .attrs = cpuhp_cpu_attrs,
2834 .name = "hotplug",
2835 NULL
2836};
2837
2838static ssize_t states_show(struct device *dev,
2839 struct device_attribute *attr, char *buf)
2840{
2841 ssize_t cur, res = 0;
2842 int i;
2843
2844 mutex_lock(&cpuhp_state_mutex);
2845 for (i = CPUHP_OFFLINE; i <= CPUHP_ONLINE; i++) {
2846 struct cpuhp_step *sp = cpuhp_get_step(i);
2847
2848 if (sp->name) {
2849 cur = sprintf(buf, "%3d: %s\n", i, sp->name);
2850 buf += cur;
2851 res += cur;
2852 }
2853 }
2854 mutex_unlock(&cpuhp_state_mutex);
2855 return res;
2856}
2857static DEVICE_ATTR_RO(states);
2858
2859static struct attribute *cpuhp_cpu_root_attrs[] = {
2860 &dev_attr_states.attr,
2861 NULL
2862};
2863
2864static const struct attribute_group cpuhp_cpu_root_attr_group = {
2865 .attrs = cpuhp_cpu_root_attrs,
2866 .name = "hotplug",
2867 NULL
2868};
2869
2870#ifdef CONFIG_HOTPLUG_SMT
2871
2872static bool cpu_smt_num_threads_valid(unsigned int threads)
2873{
2874 if (IS_ENABLED(CONFIG_SMT_NUM_THREADS_DYNAMIC))
2875 return threads >= 1 && threads <= cpu_smt_max_threads;
2876 return threads == 1 || threads == cpu_smt_max_threads;
2877}
2878
2879static ssize_t
2880__store_smt_control(struct device *dev, struct device_attribute *attr,
2881 const char *buf, size_t count)
2882{
2883 int ctrlval, ret, num_threads, orig_threads;
2884 bool force_off;
2885
2886 if (cpu_smt_control == CPU_SMT_FORCE_DISABLED)
2887 return -EPERM;
2888
2889 if (cpu_smt_control == CPU_SMT_NOT_SUPPORTED)
2890 return -ENODEV;
2891
2892 if (sysfs_streq(buf, "on")) {
2893 ctrlval = CPU_SMT_ENABLED;
2894 num_threads = cpu_smt_max_threads;
2895 } else if (sysfs_streq(buf, "off")) {
2896 ctrlval = CPU_SMT_DISABLED;
2897 num_threads = 1;
2898 } else if (sysfs_streq(buf, "forceoff")) {
2899 ctrlval = CPU_SMT_FORCE_DISABLED;
2900 num_threads = 1;
2901 } else if (kstrtoint(buf, 10, &num_threads) == 0) {
2902 if (num_threads == 1)
2903 ctrlval = CPU_SMT_DISABLED;
2904 else if (cpu_smt_num_threads_valid(num_threads))
2905 ctrlval = CPU_SMT_ENABLED;
2906 else
2907 return -EINVAL;
2908 } else {
2909 return -EINVAL;
2910 }
2911
2912 ret = lock_device_hotplug_sysfs();
2913 if (ret)
2914 return ret;
2915
2916 orig_threads = cpu_smt_num_threads;
2917 cpu_smt_num_threads = num_threads;
2918
2919 force_off = ctrlval != cpu_smt_control && ctrlval == CPU_SMT_FORCE_DISABLED;
2920
2921 if (num_threads > orig_threads)
2922 ret = cpuhp_smt_enable();
2923 else if (num_threads < orig_threads || force_off)
2924 ret = cpuhp_smt_disable(ctrlval);
2925
2926 unlock_device_hotplug();
2927 return ret ? ret : count;
2928}
2929
2930#else /* !CONFIG_HOTPLUG_SMT */
2931static ssize_t
2932__store_smt_control(struct device *dev, struct device_attribute *attr,
2933 const char *buf, size_t count)
2934{
2935 return -ENODEV;
2936}
2937#endif /* CONFIG_HOTPLUG_SMT */
2938
2939static const char *smt_states[] = {
2940 [CPU_SMT_ENABLED] = "on",
2941 [CPU_SMT_DISABLED] = "off",
2942 [CPU_SMT_FORCE_DISABLED] = "forceoff",
2943 [CPU_SMT_NOT_SUPPORTED] = "notsupported",
2944 [CPU_SMT_NOT_IMPLEMENTED] = "notimplemented",
2945};
2946
2947static ssize_t control_show(struct device *dev,
2948 struct device_attribute *attr, char *buf)
2949{
2950 const char *state = smt_states[cpu_smt_control];
2951
2952#ifdef CONFIG_HOTPLUG_SMT
2953 /*
2954 * If SMT is enabled but not all threads are enabled then show the
2955 * number of threads. If all threads are enabled show "on". Otherwise
2956 * show the state name.
2957 */
2958 if (cpu_smt_control == CPU_SMT_ENABLED &&
2959 cpu_smt_num_threads != cpu_smt_max_threads)
2960 return sysfs_emit(buf, "%d\n", cpu_smt_num_threads);
2961#endif
2962
2963 return sysfs_emit(buf, "%s\n", state);
2964}
2965
2966static ssize_t control_store(struct device *dev, struct device_attribute *attr,
2967 const char *buf, size_t count)
2968{
2969 return __store_smt_control(dev, attr, buf, count);
2970}
2971static DEVICE_ATTR_RW(control);
2972
2973static ssize_t active_show(struct device *dev,
2974 struct device_attribute *attr, char *buf)
2975{
2976 return sysfs_emit(buf, "%d\n", sched_smt_active());
2977}
2978static DEVICE_ATTR_RO(active);
2979
2980static struct attribute *cpuhp_smt_attrs[] = {
2981 &dev_attr_control.attr,
2982 &dev_attr_active.attr,
2983 NULL
2984};
2985
2986static const struct attribute_group cpuhp_smt_attr_group = {
2987 .attrs = cpuhp_smt_attrs,
2988 .name = "smt",
2989 NULL
2990};
2991
2992static int __init cpu_smt_sysfs_init(void)
2993{
2994 struct device *dev_root;
2995 int ret = -ENODEV;
2996
2997 dev_root = bus_get_dev_root(&cpu_subsys);
2998 if (dev_root) {
2999 ret = sysfs_create_group(&dev_root->kobj, &cpuhp_smt_attr_group);
3000 put_device(dev_root);
3001 }
3002 return ret;
3003}
3004
3005static int __init cpuhp_sysfs_init(void)
3006{
3007 struct device *dev_root;
3008 int cpu, ret;
3009
3010 ret = cpu_smt_sysfs_init();
3011 if (ret)
3012 return ret;
3013
3014 dev_root = bus_get_dev_root(&cpu_subsys);
3015 if (dev_root) {
3016 ret = sysfs_create_group(&dev_root->kobj, &cpuhp_cpu_root_attr_group);
3017 put_device(dev_root);
3018 if (ret)
3019 return ret;
3020 }
3021
3022 for_each_possible_cpu(cpu) {
3023 struct device *dev = get_cpu_device(cpu);
3024
3025 if (!dev)
3026 continue;
3027 ret = sysfs_create_group(&dev->kobj, &cpuhp_cpu_attr_group);
3028 if (ret)
3029 return ret;
3030 }
3031 return 0;
3032}
3033device_initcall(cpuhp_sysfs_init);
3034#endif /* CONFIG_SYSFS && CONFIG_HOTPLUG_CPU */
3035
3036/*
3037 * cpu_bit_bitmap[] is a special, "compressed" data structure that
3038 * represents all NR_CPUS bits binary values of 1<<nr.
3039 *
3040 * It is used by cpumask_of() to get a constant address to a CPU
3041 * mask value that has a single bit set only.
3042 */
3043
3044/* cpu_bit_bitmap[0] is empty - so we can back into it */
3045#define MASK_DECLARE_1(x) [x+1][0] = (1UL << (x))
3046#define MASK_DECLARE_2(x) MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
3047#define MASK_DECLARE_4(x) MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
3048#define MASK_DECLARE_8(x) MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
3049
3050const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
3051
3052 MASK_DECLARE_8(0), MASK_DECLARE_8(8),
3053 MASK_DECLARE_8(16), MASK_DECLARE_8(24),
3054#if BITS_PER_LONG > 32
3055 MASK_DECLARE_8(32), MASK_DECLARE_8(40),
3056 MASK_DECLARE_8(48), MASK_DECLARE_8(56),
3057#endif
3058};
3059EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
3060
3061const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
3062EXPORT_SYMBOL(cpu_all_bits);
3063
3064#ifdef CONFIG_INIT_ALL_POSSIBLE
3065struct cpumask __cpu_possible_mask __ro_after_init
3066 = {CPU_BITS_ALL};
3067#else
3068struct cpumask __cpu_possible_mask __ro_after_init;
3069#endif
3070EXPORT_SYMBOL(__cpu_possible_mask);
3071
3072struct cpumask __cpu_online_mask __read_mostly;
3073EXPORT_SYMBOL(__cpu_online_mask);
3074
3075struct cpumask __cpu_present_mask __read_mostly;
3076EXPORT_SYMBOL(__cpu_present_mask);
3077
3078struct cpumask __cpu_active_mask __read_mostly;
3079EXPORT_SYMBOL(__cpu_active_mask);
3080
3081struct cpumask __cpu_dying_mask __read_mostly;
3082EXPORT_SYMBOL(__cpu_dying_mask);
3083
3084atomic_t __num_online_cpus __read_mostly;
3085EXPORT_SYMBOL(__num_online_cpus);
3086
3087void init_cpu_present(const struct cpumask *src)
3088{
3089 cpumask_copy(&__cpu_present_mask, src);
3090}
3091
3092void init_cpu_possible(const struct cpumask *src)
3093{
3094 cpumask_copy(&__cpu_possible_mask, src);
3095}
3096
3097void init_cpu_online(const struct cpumask *src)
3098{
3099 cpumask_copy(&__cpu_online_mask, src);
3100}
3101
3102void set_cpu_online(unsigned int cpu, bool online)
3103{
3104 /*
3105 * atomic_inc/dec() is required to handle the horrid abuse of this
3106 * function by the reboot and kexec code which invoke it from
3107 * IPI/NMI broadcasts when shutting down CPUs. Invocation from
3108 * regular CPU hotplug is properly serialized.
3109 *
3110 * Note, that the fact that __num_online_cpus is of type atomic_t
3111 * does not protect readers which are not serialized against
3112 * concurrent hotplug operations.
3113 */
3114 if (online) {
3115 if (!cpumask_test_and_set_cpu(cpu, &__cpu_online_mask))
3116 atomic_inc(&__num_online_cpus);
3117 } else {
3118 if (cpumask_test_and_clear_cpu(cpu, &__cpu_online_mask))
3119 atomic_dec(&__num_online_cpus);
3120 }
3121}
3122
3123/*
3124 * Activate the first processor.
3125 */
3126void __init boot_cpu_init(void)
3127{
3128 int cpu = smp_processor_id();
3129
3130 /* Mark the boot cpu "present", "online" etc for SMP and UP case */
3131 set_cpu_online(cpu, true);
3132 set_cpu_active(cpu, true);
3133 set_cpu_present(cpu, true);
3134 set_cpu_possible(cpu, true);
3135
3136#ifdef CONFIG_SMP
3137 __boot_cpu_id = cpu;
3138#endif
3139}
3140
3141/*
3142 * Must be called _AFTER_ setting up the per_cpu areas
3143 */
3144void __init boot_cpu_hotplug_init(void)
3145{
3146#ifdef CONFIG_SMP
3147 cpumask_set_cpu(smp_processor_id(), &cpus_booted_once_mask);
3148 atomic_set(this_cpu_ptr(&cpuhp_state.ap_sync_state), SYNC_STATE_ONLINE);
3149#endif
3150 this_cpu_write(cpuhp_state.state, CPUHP_ONLINE);
3151 this_cpu_write(cpuhp_state.target, CPUHP_ONLINE);
3152}
3153
3154#ifdef CONFIG_CPU_MITIGATIONS
3155/*
3156 * These are used for a global "mitigations=" cmdline option for toggling
3157 * optional CPU mitigations.
3158 */
3159enum cpu_mitigations {
3160 CPU_MITIGATIONS_OFF,
3161 CPU_MITIGATIONS_AUTO,
3162 CPU_MITIGATIONS_AUTO_NOSMT,
3163};
3164
3165static enum cpu_mitigations cpu_mitigations __ro_after_init = CPU_MITIGATIONS_AUTO;
3166
3167static int __init mitigations_parse_cmdline(char *arg)
3168{
3169 if (!strcmp(arg, "off"))
3170 cpu_mitigations = CPU_MITIGATIONS_OFF;
3171 else if (!strcmp(arg, "auto"))
3172 cpu_mitigations = CPU_MITIGATIONS_AUTO;
3173 else if (!strcmp(arg, "auto,nosmt"))
3174 cpu_mitigations = CPU_MITIGATIONS_AUTO_NOSMT;
3175 else
3176 pr_crit("Unsupported mitigations=%s, system may still be vulnerable\n",
3177 arg);
3178
3179 return 0;
3180}
3181
3182/* mitigations=off */
3183bool cpu_mitigations_off(void)
3184{
3185 return cpu_mitigations == CPU_MITIGATIONS_OFF;
3186}
3187EXPORT_SYMBOL_GPL(cpu_mitigations_off);
3188
3189/* mitigations=auto,nosmt */
3190bool cpu_mitigations_auto_nosmt(void)
3191{
3192 return cpu_mitigations == CPU_MITIGATIONS_AUTO_NOSMT;
3193}
3194EXPORT_SYMBOL_GPL(cpu_mitigations_auto_nosmt);
3195#else
3196static int __init mitigations_parse_cmdline(char *arg)
3197{
3198 pr_crit("Kernel compiled without mitigations, ignoring 'mitigations'; system may still be vulnerable\n");
3199 return 0;
3200}
3201#endif
3202early_param("mitigations", mitigations_parse_cmdline);