2 * (C) 2001, 2002, 2003, 2004 Rusty Russell
4 * This code is licenced under the GPL.
6 #include <linux/proc_fs.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/task.h>
13 #include <linux/sched/smt.h>
14 #include <linux/unistd.h>
15 #include <linux/cpu.h>
16 #include <linux/oom.h>
17 #include <linux/rcupdate.h>
18 #include <linux/export.h>
19 #include <linux/bug.h>
20 #include <linux/kthread.h>
21 #include <linux/stop_machine.h>
22 #include <linux/mutex.h>
23 #include <linux/gfp.h>
24 #include <linux/suspend.h>
25 #include <linux/lockdep.h>
26 #include <linux/tick.h>
27 #include <linux/irq.h>
28 #include <linux/nmi.h>
29 #include <linux/smpboot.h>
30 #include <linux/relay.h>
31 #include <linux/slab.h>
32 #include <linux/percpu-rwsem.h>
34 #include <trace/events/power.h>
35 #define CREATE_TRACE_POINTS
36 #include <trace/events/cpuhp.h>
41 * cpuhp_cpu_state - Per cpu hotplug state storage
42 * @state: The current cpu state
43 * @target: The target state
44 * @thread: Pointer to the hotplug thread
45 * @should_run: Thread should execute
46 * @rollback: Perform a rollback
47 * @single: Single callback invocation
48 * @bringup: Single callback bringup or teardown selector
49 * @cb_state: The state for a single callback (install/uninstall)
50 * @result: Result of the operation
51 * @done_up: Signal completion to the issuer of the task for cpu-up
52 * @done_down: Signal completion to the issuer of the task for cpu-down
54 struct cpuhp_cpu_state {
55 enum cpuhp_state state;
56 enum cpuhp_state target;
57 enum cpuhp_state fail;
59 struct task_struct *thread;
65 struct hlist_node *node;
66 struct hlist_node *last;
67 enum cpuhp_state cb_state;
69 struct completion done_up;
70 struct completion done_down;
74 static DEFINE_PER_CPU(struct cpuhp_cpu_state, cpuhp_state) = {
75 .fail = CPUHP_INVALID,
78 #if defined(CONFIG_LOCKDEP) && defined(CONFIG_SMP)
79 static struct lockdep_map cpuhp_state_up_map =
80 STATIC_LOCKDEP_MAP_INIT("cpuhp_state-up", &cpuhp_state_up_map);
81 static struct lockdep_map cpuhp_state_down_map =
82 STATIC_LOCKDEP_MAP_INIT("cpuhp_state-down", &cpuhp_state_down_map);
85 static void inline cpuhp_lock_acquire(bool bringup)
87 lock_map_acquire(bringup ? &cpuhp_state_up_map : &cpuhp_state_down_map);
90 static void inline cpuhp_lock_release(bool bringup)
92 lock_map_release(bringup ? &cpuhp_state_up_map : &cpuhp_state_down_map);
96 static void inline cpuhp_lock_acquire(bool bringup) { }
97 static void inline cpuhp_lock_release(bool bringup) { }
102 * cpuhp_step - Hotplug state machine step
103 * @name: Name of the step
104 * @startup: Startup function of the step
105 * @teardown: Teardown function of the step
106 * @skip_onerr: Do not invoke the functions on error rollback
107 * Will go away once the notifiers are gone
108 * @cant_stop: Bringup/teardown can't be stopped at this step
113 int (*single)(unsigned int cpu);
114 int (*multi)(unsigned int cpu,
115 struct hlist_node *node);
118 int (*single)(unsigned int cpu);
119 int (*multi)(unsigned int cpu,
120 struct hlist_node *node);
122 struct hlist_head list;
128 static DEFINE_MUTEX(cpuhp_state_mutex);
129 static struct cpuhp_step cpuhp_bp_states[];
130 static struct cpuhp_step cpuhp_ap_states[];
132 static bool cpuhp_is_ap_state(enum cpuhp_state state)
135 * The extra check for CPUHP_TEARDOWN_CPU is only for documentation
136 * purposes as that state is handled explicitly in cpu_down.
138 return state > CPUHP_BRINGUP_CPU && state != CPUHP_TEARDOWN_CPU;
141 static struct cpuhp_step *cpuhp_get_step(enum cpuhp_state state)
143 struct cpuhp_step *sp;
145 sp = cpuhp_is_ap_state(state) ? cpuhp_ap_states : cpuhp_bp_states;
150 * cpuhp_invoke_callback _ Invoke the callbacks for a given state
151 * @cpu: The cpu for which the callback should be invoked
152 * @state: The state to do callbacks for
153 * @bringup: True if the bringup callback should be invoked
154 * @node: For multi-instance, do a single entry callback for install/remove
155 * @lastp: For multi-instance rollback, remember how far we got
157 * Called from cpu hotplug and from the state register machinery.
159 static int cpuhp_invoke_callback(unsigned int cpu, enum cpuhp_state state,
160 bool bringup, struct hlist_node *node,
161 struct hlist_node **lastp)
163 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
164 struct cpuhp_step *step = cpuhp_get_step(state);
165 int (*cbm)(unsigned int cpu, struct hlist_node *node);
166 int (*cb)(unsigned int cpu);
169 if (st->fail == state) {
170 st->fail = CPUHP_INVALID;
172 if (!(bringup ? step->startup.single : step->teardown.single))
178 if (!step->multi_instance) {
179 WARN_ON_ONCE(lastp && *lastp);
180 cb = bringup ? step->startup.single : step->teardown.single;
183 trace_cpuhp_enter(cpu, st->target, state, cb);
185 trace_cpuhp_exit(cpu, st->state, state, ret);
188 cbm = bringup ? step->startup.multi : step->teardown.multi;
192 /* Single invocation for instance add/remove */
194 WARN_ON_ONCE(lastp && *lastp);
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);
201 /* State transition. Invoke on all instances */
203 hlist_for_each(node, &step->list) {
204 if (lastp && node == *lastp)
207 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
208 ret = cbm(cpu, node);
209 trace_cpuhp_exit(cpu, st->state, state, ret);
223 /* Rollback the instances if one failed */
224 cbm = !bringup ? step->startup.multi : step->teardown.multi;
228 hlist_for_each(node, &step->list) {
232 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
233 ret = cbm(cpu, node);
234 trace_cpuhp_exit(cpu, st->state, state, ret);
236 * Rollback must not fail,
244 static inline void wait_for_ap_thread(struct cpuhp_cpu_state *st, bool bringup)
246 struct completion *done = bringup ? &st->done_up : &st->done_down;
247 wait_for_completion(done);
250 static inline void complete_ap_thread(struct cpuhp_cpu_state *st, bool bringup)
252 struct completion *done = bringup ? &st->done_up : &st->done_down;
257 * The former STARTING/DYING states, ran with IRQs disabled and must not fail.
259 static bool cpuhp_is_atomic_state(enum cpuhp_state state)
261 return CPUHP_AP_IDLE_DEAD <= state && state < CPUHP_AP_ONLINE;
264 /* Serializes the updates to cpu_online_mask, cpu_present_mask */
265 static DEFINE_MUTEX(cpu_add_remove_lock);
266 bool cpuhp_tasks_frozen;
267 EXPORT_SYMBOL_GPL(cpuhp_tasks_frozen);
270 * The following two APIs (cpu_maps_update_begin/done) must be used when
271 * attempting to serialize the updates to cpu_online_mask & cpu_present_mask.
273 void cpu_maps_update_begin(void)
275 mutex_lock(&cpu_add_remove_lock);
278 void cpu_maps_update_done(void)
280 mutex_unlock(&cpu_add_remove_lock);
284 * If set, cpu_up and cpu_down will return -EBUSY and do nothing.
285 * Should always be manipulated under cpu_add_remove_lock
287 static int cpu_hotplug_disabled;
289 #ifdef CONFIG_HOTPLUG_CPU
291 DEFINE_STATIC_PERCPU_RWSEM(cpu_hotplug_lock);
293 void cpus_read_lock(void)
295 percpu_down_read(&cpu_hotplug_lock);
297 EXPORT_SYMBOL_GPL(cpus_read_lock);
299 void cpus_read_unlock(void)
301 percpu_up_read(&cpu_hotplug_lock);
303 EXPORT_SYMBOL_GPL(cpus_read_unlock);
305 void cpus_write_lock(void)
307 percpu_down_write(&cpu_hotplug_lock);
310 void cpus_write_unlock(void)
312 percpu_up_write(&cpu_hotplug_lock);
315 void lockdep_assert_cpus_held(void)
317 percpu_rwsem_assert_held(&cpu_hotplug_lock);
321 * Wait for currently running CPU hotplug operations to complete (if any) and
322 * disable future CPU hotplug (from sysfs). The 'cpu_add_remove_lock' protects
323 * the 'cpu_hotplug_disabled' flag. The same lock is also acquired by the
324 * hotplug path before performing hotplug operations. So acquiring that lock
325 * guarantees mutual exclusion from any currently running hotplug operations.
327 void cpu_hotplug_disable(void)
329 cpu_maps_update_begin();
330 cpu_hotplug_disabled++;
331 cpu_maps_update_done();
333 EXPORT_SYMBOL_GPL(cpu_hotplug_disable);
335 static void __cpu_hotplug_enable(void)
337 if (WARN_ONCE(!cpu_hotplug_disabled, "Unbalanced cpu hotplug enable\n"))
339 cpu_hotplug_disabled--;
342 void cpu_hotplug_enable(void)
344 cpu_maps_update_begin();
345 __cpu_hotplug_enable();
346 cpu_maps_update_done();
348 EXPORT_SYMBOL_GPL(cpu_hotplug_enable);
349 #endif /* CONFIG_HOTPLUG_CPU */
352 * Architectures that need SMT-specific errata handling during SMT hotplug
353 * should override this.
355 void __weak arch_smt_update(void) { }
357 #ifdef CONFIG_HOTPLUG_SMT
358 enum cpuhp_smt_control cpu_smt_control __read_mostly = CPU_SMT_ENABLED;
360 void __init cpu_smt_disable(bool force)
362 if (cpu_smt_control == CPU_SMT_FORCE_DISABLED ||
363 cpu_smt_control == CPU_SMT_NOT_SUPPORTED)
367 pr_info("SMT: Force disabled\n");
368 cpu_smt_control = CPU_SMT_FORCE_DISABLED;
370 cpu_smt_control = CPU_SMT_DISABLED;
375 * The decision whether SMT is supported can only be done after the full
376 * CPU identification. Called from architecture code.
378 void __init cpu_smt_check_topology(void)
380 if (!topology_smt_supported())
381 cpu_smt_control = CPU_SMT_NOT_SUPPORTED;
384 static int __init smt_cmdline_disable(char *str)
386 cpu_smt_disable(str && !strcmp(str, "force"));
389 early_param("nosmt", smt_cmdline_disable);
391 static inline bool cpu_smt_allowed(unsigned int cpu)
393 if (cpu_smt_control == CPU_SMT_ENABLED)
396 if (topology_is_primary_thread(cpu))
400 * On x86 it's required to boot all logical CPUs at least once so
401 * that the init code can get a chance to set CR4.MCE on each
402 * CPU. Otherwise, a broadacasted MCE observing CR4.MCE=0b on any
403 * core will shutdown the machine.
405 return !per_cpu(cpuhp_state, cpu).booted_once;
408 static inline bool cpu_smt_allowed(unsigned int cpu) { return true; }
411 static inline enum cpuhp_state
412 cpuhp_set_state(struct cpuhp_cpu_state *st, enum cpuhp_state target)
414 enum cpuhp_state prev_state = st->state;
416 st->rollback = false;
421 st->bringup = st->state < target;
427 cpuhp_reset_state(struct cpuhp_cpu_state *st, enum cpuhp_state prev_state)
432 * If we have st->last we need to undo partial multi_instance of this
433 * state first. Otherwise start undo at the previous state.
442 st->target = prev_state;
443 st->bringup = !st->bringup;
446 /* Regular hotplug invocation of the AP hotplug thread */
447 static void __cpuhp_kick_ap(struct cpuhp_cpu_state *st)
449 if (!st->single && st->state == st->target)
454 * Make sure the above stores are visible before should_run becomes
455 * true. Paired with the mb() above in cpuhp_thread_fun()
458 st->should_run = true;
459 wake_up_process(st->thread);
460 wait_for_ap_thread(st, st->bringup);
463 static int cpuhp_kick_ap(struct cpuhp_cpu_state *st, enum cpuhp_state target)
465 enum cpuhp_state prev_state;
468 prev_state = cpuhp_set_state(st, target);
470 if ((ret = st->result)) {
471 cpuhp_reset_state(st, prev_state);
478 static int bringup_wait_for_ap(unsigned int cpu)
480 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
482 /* Wait for the CPU to reach CPUHP_AP_ONLINE_IDLE */
483 wait_for_ap_thread(st, true);
484 if (WARN_ON_ONCE((!cpu_online(cpu))))
487 /* Unpark the stopper thread and the hotplug thread of the target cpu */
488 stop_machine_unpark(cpu);
489 kthread_unpark(st->thread);
492 * SMT soft disabling on X86 requires to bring the CPU out of the
493 * BIOS 'wait for SIPI' state in order to set the CR4.MCE bit. The
494 * CPU marked itself as booted_once in cpu_notify_starting() so the
495 * cpu_smt_allowed() check will now return false if this is not the
498 if (!cpu_smt_allowed(cpu))
501 if (st->target <= CPUHP_AP_ONLINE_IDLE)
504 return cpuhp_kick_ap(st, st->target);
507 static int bringup_cpu(unsigned int cpu)
509 struct task_struct *idle = idle_thread_get(cpu);
513 * Some architectures have to walk the irq descriptors to
514 * setup the vector space for the cpu which comes online.
515 * Prevent irq alloc/free across the bringup.
519 /* Arch-specific enabling code. */
520 ret = __cpu_up(cpu, idle);
524 return bringup_wait_for_ap(cpu);
528 * Hotplug state machine related functions
531 static void undo_cpu_up(unsigned int cpu, struct cpuhp_cpu_state *st)
533 for (st->state--; st->state > st->target; st->state--) {
534 struct cpuhp_step *step = cpuhp_get_step(st->state);
536 if (!step->skip_onerr)
537 cpuhp_invoke_callback(cpu, st->state, false, NULL, NULL);
541 static int cpuhp_up_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
542 enum cpuhp_state target)
544 enum cpuhp_state prev_state = st->state;
547 while (st->state < target) {
549 ret = cpuhp_invoke_callback(cpu, st->state, true, NULL, NULL);
551 st->target = prev_state;
552 undo_cpu_up(cpu, st);
560 * The cpu hotplug threads manage the bringup and teardown of the cpus
562 static void cpuhp_create(unsigned int cpu)
564 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
566 init_completion(&st->done_up);
567 init_completion(&st->done_down);
570 static int cpuhp_should_run(unsigned int cpu)
572 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
574 return st->should_run;
578 * Execute teardown/startup callbacks on the plugged cpu. Also used to invoke
579 * callbacks when a state gets [un]installed at runtime.
581 * Each invocation of this function by the smpboot thread does a single AP
584 * It has 3 modes of operation:
585 * - single: runs st->cb_state
586 * - up: runs ++st->state, while st->state < st->target
587 * - down: runs st->state--, while st->state > st->target
589 * When complete or on error, should_run is cleared and the completion is fired.
591 static void cpuhp_thread_fun(unsigned int cpu)
593 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
594 bool bringup = st->bringup;
595 enum cpuhp_state state;
597 if (WARN_ON_ONCE(!st->should_run))
601 * ACQUIRE for the cpuhp_should_run() load of ->should_run. Ensures
602 * that if we see ->should_run we also see the rest of the state.
606 cpuhp_lock_acquire(bringup);
609 state = st->cb_state;
610 st->should_run = false;
615 st->should_run = (st->state < st->target);
616 WARN_ON_ONCE(st->state > st->target);
620 st->should_run = (st->state > st->target);
621 WARN_ON_ONCE(st->state < st->target);
625 WARN_ON_ONCE(!cpuhp_is_ap_state(state));
628 struct cpuhp_step *step = cpuhp_get_step(state);
629 if (step->skip_onerr)
633 if (cpuhp_is_atomic_state(state)) {
635 st->result = cpuhp_invoke_callback(cpu, state, bringup, st->node, &st->last);
639 * STARTING/DYING must not fail!
641 WARN_ON_ONCE(st->result);
643 st->result = cpuhp_invoke_callback(cpu, state, bringup, st->node, &st->last);
648 * If we fail on a rollback, we're up a creek without no
649 * paddle, no way forward, no way back. We loose, thanks for
652 WARN_ON_ONCE(st->rollback);
653 st->should_run = false;
657 cpuhp_lock_release(bringup);
660 complete_ap_thread(st, bringup);
663 /* Invoke a single callback on a remote cpu */
665 cpuhp_invoke_ap_callback(int cpu, enum cpuhp_state state, bool bringup,
666 struct hlist_node *node)
668 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
671 if (!cpu_online(cpu))
674 cpuhp_lock_acquire(false);
675 cpuhp_lock_release(false);
677 cpuhp_lock_acquire(true);
678 cpuhp_lock_release(true);
681 * If we are up and running, use the hotplug thread. For early calls
682 * we invoke the thread function directly.
685 return cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
687 st->rollback = false;
691 st->bringup = bringup;
692 st->cb_state = state;
698 * If we failed and did a partial, do a rollback.
700 if ((ret = st->result) && st->last) {
702 st->bringup = !bringup;
708 * Clean up the leftovers so the next hotplug operation wont use stale
711 st->node = st->last = NULL;
715 static int cpuhp_kick_ap_work(unsigned int cpu)
717 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
718 enum cpuhp_state prev_state = st->state;
721 cpuhp_lock_acquire(false);
722 cpuhp_lock_release(false);
724 cpuhp_lock_acquire(true);
725 cpuhp_lock_release(true);
727 trace_cpuhp_enter(cpu, st->target, prev_state, cpuhp_kick_ap_work);
728 ret = cpuhp_kick_ap(st, st->target);
729 trace_cpuhp_exit(cpu, st->state, prev_state, ret);
734 static struct smp_hotplug_thread cpuhp_threads = {
735 .store = &cpuhp_state.thread,
736 .create = &cpuhp_create,
737 .thread_should_run = cpuhp_should_run,
738 .thread_fn = cpuhp_thread_fun,
739 .thread_comm = "cpuhp/%u",
743 void __init cpuhp_threads_init(void)
745 BUG_ON(smpboot_register_percpu_thread(&cpuhp_threads));
746 kthread_unpark(this_cpu_read(cpuhp_state.thread));
749 #ifdef CONFIG_HOTPLUG_CPU
751 * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
754 * This function walks all processes, finds a valid mm struct for each one and
755 * then clears a corresponding bit in mm's cpumask. While this all sounds
756 * trivial, there are various non-obvious corner cases, which this function
757 * tries to solve in a safe manner.
759 * Also note that the function uses a somewhat relaxed locking scheme, so it may
760 * be called only for an already offlined CPU.
762 void clear_tasks_mm_cpumask(int cpu)
764 struct task_struct *p;
767 * This function is called after the cpu is taken down and marked
768 * offline, so its not like new tasks will ever get this cpu set in
769 * their mm mask. -- Peter Zijlstra
770 * Thus, we may use rcu_read_lock() here, instead of grabbing
771 * full-fledged tasklist_lock.
773 WARN_ON(cpu_online(cpu));
775 for_each_process(p) {
776 struct task_struct *t;
779 * Main thread might exit, but other threads may still have
780 * a valid mm. Find one.
782 t = find_lock_task_mm(p);
785 cpumask_clear_cpu(cpu, mm_cpumask(t->mm));
791 /* Take this CPU down. */
792 static int take_cpu_down(void *_param)
794 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
795 enum cpuhp_state target = max((int)st->target, CPUHP_AP_OFFLINE);
796 int err, cpu = smp_processor_id();
799 /* Ensure this CPU doesn't handle any more interrupts. */
800 err = __cpu_disable();
805 * We get here while we are in CPUHP_TEARDOWN_CPU state and we must not
806 * do this step again.
808 WARN_ON(st->state != CPUHP_TEARDOWN_CPU);
810 /* Invoke the former CPU_DYING callbacks */
811 for (; st->state > target; st->state--) {
812 ret = cpuhp_invoke_callback(cpu, st->state, false, NULL, NULL);
814 * DYING must not fail!
819 /* Give up timekeeping duties */
820 tick_handover_do_timer();
821 /* Park the stopper thread */
822 stop_machine_park(cpu);
826 static int takedown_cpu(unsigned int cpu)
828 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
831 /* Park the smpboot threads */
832 kthread_park(per_cpu_ptr(&cpuhp_state, cpu)->thread);
835 * Prevent irq alloc/free while the dying cpu reorganizes the
836 * interrupt affinities.
841 * So now all preempt/rcu users must observe !cpu_active().
843 err = stop_machine_cpuslocked(take_cpu_down, NULL, cpumask_of(cpu));
845 /* CPU refused to die */
847 /* Unpark the hotplug thread so we can rollback there */
848 kthread_unpark(per_cpu_ptr(&cpuhp_state, cpu)->thread);
851 BUG_ON(cpu_online(cpu));
854 * The CPUHP_AP_SCHED_MIGRATE_DYING callback will have removed all
855 * runnable tasks from the cpu, there's only the idle task left now
856 * that the migration thread is done doing the stop_machine thing.
858 * Wait for the stop thread to go away.
860 wait_for_ap_thread(st, false);
861 BUG_ON(st->state != CPUHP_AP_IDLE_DEAD);
863 /* Interrupts are moved away from the dying cpu, reenable alloc/free */
866 hotplug_cpu__broadcast_tick_pull(cpu);
867 /* This actually kills the CPU. */
870 tick_cleanup_dead_cpu(cpu);
871 rcutree_migrate_callbacks(cpu);
875 static void cpuhp_complete_idle_dead(void *arg)
877 struct cpuhp_cpu_state *st = arg;
879 complete_ap_thread(st, false);
882 void cpuhp_report_idle_dead(void)
884 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
886 BUG_ON(st->state != CPUHP_AP_OFFLINE);
887 rcu_report_dead(smp_processor_id());
888 st->state = CPUHP_AP_IDLE_DEAD;
890 * We cannot call complete after rcu_report_dead() so we delegate it
893 smp_call_function_single(cpumask_first(cpu_online_mask),
894 cpuhp_complete_idle_dead, st, 0);
897 static void undo_cpu_down(unsigned int cpu, struct cpuhp_cpu_state *st)
899 for (st->state++; st->state < st->target; st->state++) {
900 struct cpuhp_step *step = cpuhp_get_step(st->state);
902 if (!step->skip_onerr)
903 cpuhp_invoke_callback(cpu, st->state, true, NULL, NULL);
907 static int cpuhp_down_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
908 enum cpuhp_state target)
910 enum cpuhp_state prev_state = st->state;
913 for (; st->state > target; st->state--) {
914 ret = cpuhp_invoke_callback(cpu, st->state, false, NULL, NULL);
916 st->target = prev_state;
917 if (st->state < prev_state)
918 undo_cpu_down(cpu, st);
925 /* Requires cpu_add_remove_lock to be held */
926 static int __ref _cpu_down(unsigned int cpu, int tasks_frozen,
927 enum cpuhp_state target)
929 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
930 int prev_state, ret = 0;
932 if (num_online_cpus() == 1)
935 if (!cpu_present(cpu))
940 cpuhp_tasks_frozen = tasks_frozen;
942 prev_state = cpuhp_set_state(st, target);
944 * If the current CPU state is in the range of the AP hotplug thread,
945 * then we need to kick the thread.
947 if (st->state > CPUHP_TEARDOWN_CPU) {
948 st->target = max((int)target, CPUHP_TEARDOWN_CPU);
949 ret = cpuhp_kick_ap_work(cpu);
951 * The AP side has done the error rollback already. Just
952 * return the error code..
958 * We might have stopped still in the range of the AP hotplug
959 * thread. Nothing to do anymore.
961 if (st->state > CPUHP_TEARDOWN_CPU)
967 * The AP brought itself down to CPUHP_TEARDOWN_CPU. So we need
968 * to do the further cleanups.
970 ret = cpuhp_down_callbacks(cpu, st, target);
971 if (ret && st->state == CPUHP_TEARDOWN_CPU && st->state < prev_state) {
972 cpuhp_reset_state(st, prev_state);
979 * Do post unplug cleanup. This is still protected against
980 * concurrent CPU hotplug via cpu_add_remove_lock.
982 lockup_detector_cleanup();
987 static int cpu_down_maps_locked(unsigned int cpu, enum cpuhp_state target)
989 if (cpu_hotplug_disabled)
991 return _cpu_down(cpu, 0, target);
994 static int do_cpu_down(unsigned int cpu, enum cpuhp_state target)
998 cpu_maps_update_begin();
999 err = cpu_down_maps_locked(cpu, target);
1000 cpu_maps_update_done();
1004 int cpu_down(unsigned int cpu)
1006 return do_cpu_down(cpu, CPUHP_OFFLINE);
1008 EXPORT_SYMBOL(cpu_down);
1011 #define takedown_cpu NULL
1012 #endif /*CONFIG_HOTPLUG_CPU*/
1015 * notify_cpu_starting(cpu) - Invoke the callbacks on the starting CPU
1016 * @cpu: cpu that just started
1018 * It must be called by the arch code on the new cpu, before the new cpu
1019 * enables interrupts and before the "boot" cpu returns from __cpu_up().
1021 void notify_cpu_starting(unsigned int cpu)
1023 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1024 enum cpuhp_state target = min((int)st->target, CPUHP_AP_ONLINE);
1027 rcu_cpu_starting(cpu); /* Enables RCU usage on this CPU. */
1028 st->booted_once = true;
1029 while (st->state < target) {
1031 ret = cpuhp_invoke_callback(cpu, st->state, true, NULL, NULL);
1033 * STARTING must not fail!
1040 * Called from the idle task. Wake up the controlling task which brings the
1041 * stopper and the hotplug thread of the upcoming CPU up and then delegates
1042 * the rest of the online bringup to the hotplug thread.
1044 void cpuhp_online_idle(enum cpuhp_state state)
1046 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
1048 /* Happens for the boot cpu */
1049 if (state != CPUHP_AP_ONLINE_IDLE)
1052 st->state = CPUHP_AP_ONLINE_IDLE;
1053 complete_ap_thread(st, true);
1056 /* Requires cpu_add_remove_lock to be held */
1057 static int _cpu_up(unsigned int cpu, int tasks_frozen, enum cpuhp_state target)
1059 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1060 struct task_struct *idle;
1065 if (!cpu_present(cpu)) {
1071 * The caller of do_cpu_up might have raced with another
1072 * caller. Ignore it for now.
1074 if (st->state >= target)
1077 if (st->state == CPUHP_OFFLINE) {
1078 /* Let it fail before we try to bring the cpu up */
1079 idle = idle_thread_get(cpu);
1081 ret = PTR_ERR(idle);
1086 cpuhp_tasks_frozen = tasks_frozen;
1088 cpuhp_set_state(st, target);
1090 * If the current CPU state is in the range of the AP hotplug thread,
1091 * then we need to kick the thread once more.
1093 if (st->state > CPUHP_BRINGUP_CPU) {
1094 ret = cpuhp_kick_ap_work(cpu);
1096 * The AP side has done the error rollback already. Just
1097 * return the error code..
1104 * Try to reach the target state. We max out on the BP at
1105 * CPUHP_BRINGUP_CPU. After that the AP hotplug thread is
1106 * responsible for bringing it up to the target state.
1108 target = min((int)target, CPUHP_BRINGUP_CPU);
1109 ret = cpuhp_up_callbacks(cpu, st, target);
1111 cpus_write_unlock();
1116 static int do_cpu_up(unsigned int cpu, enum cpuhp_state target)
1120 if (!cpu_possible(cpu)) {
1121 pr_err("can't online cpu %d because it is not configured as may-hotadd at boot time\n",
1123 #if defined(CONFIG_IA64)
1124 pr_err("please check additional_cpus= boot parameter\n");
1129 err = try_online_node(cpu_to_node(cpu));
1133 cpu_maps_update_begin();
1135 if (cpu_hotplug_disabled) {
1139 if (!cpu_smt_allowed(cpu)) {
1144 err = _cpu_up(cpu, 0, target);
1146 cpu_maps_update_done();
1150 int cpu_up(unsigned int cpu)
1152 return do_cpu_up(cpu, CPUHP_ONLINE);
1154 EXPORT_SYMBOL_GPL(cpu_up);
1156 #ifdef CONFIG_PM_SLEEP_SMP
1157 static cpumask_var_t frozen_cpus;
1159 int freeze_secondary_cpus(int primary)
1163 cpu_maps_update_begin();
1164 if (!cpu_online(primary))
1165 primary = cpumask_first(cpu_online_mask);
1167 * We take down all of the non-boot CPUs in one shot to avoid races
1168 * with the userspace trying to use the CPU hotplug at the same time
1170 cpumask_clear(frozen_cpus);
1172 pr_info("Disabling non-boot CPUs ...\n");
1173 for_each_online_cpu(cpu) {
1176 trace_suspend_resume(TPS("CPU_OFF"), cpu, true);
1177 error = _cpu_down(cpu, 1, CPUHP_OFFLINE);
1178 trace_suspend_resume(TPS("CPU_OFF"), cpu, false);
1180 cpumask_set_cpu(cpu, frozen_cpus);
1182 pr_err("Error taking CPU%d down: %d\n", cpu, error);
1188 BUG_ON(num_online_cpus() > 1);
1190 pr_err("Non-boot CPUs are not disabled\n");
1193 * Make sure the CPUs won't be enabled by someone else. We need to do
1194 * this even in case of failure as all disable_nonboot_cpus() users are
1195 * supposed to do enable_nonboot_cpus() on the failure path.
1197 cpu_hotplug_disabled++;
1199 cpu_maps_update_done();
1203 void __weak arch_enable_nonboot_cpus_begin(void)
1207 void __weak arch_enable_nonboot_cpus_end(void)
1211 void enable_nonboot_cpus(void)
1215 /* Allow everyone to use the CPU hotplug again */
1216 cpu_maps_update_begin();
1217 __cpu_hotplug_enable();
1218 if (cpumask_empty(frozen_cpus))
1221 pr_info("Enabling non-boot CPUs ...\n");
1223 arch_enable_nonboot_cpus_begin();
1225 for_each_cpu(cpu, frozen_cpus) {
1226 trace_suspend_resume(TPS("CPU_ON"), cpu, true);
1227 error = _cpu_up(cpu, 1, CPUHP_ONLINE);
1228 trace_suspend_resume(TPS("CPU_ON"), cpu, false);
1230 pr_info("CPU%d is up\n", cpu);
1233 pr_warn("Error taking CPU%d up: %d\n", cpu, error);
1236 arch_enable_nonboot_cpus_end();
1238 cpumask_clear(frozen_cpus);
1240 cpu_maps_update_done();
1243 static int __init alloc_frozen_cpus(void)
1245 if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
1249 core_initcall(alloc_frozen_cpus);
1252 * When callbacks for CPU hotplug notifications are being executed, we must
1253 * ensure that the state of the system with respect to the tasks being frozen
1254 * or not, as reported by the notification, remains unchanged *throughout the
1255 * duration* of the execution of the callbacks.
1256 * Hence we need to prevent the freezer from racing with regular CPU hotplug.
1258 * This synchronization is implemented by mutually excluding regular CPU
1259 * hotplug and Suspend/Hibernate call paths by hooking onto the Suspend/
1260 * Hibernate notifications.
1263 cpu_hotplug_pm_callback(struct notifier_block *nb,
1264 unsigned long action, void *ptr)
1268 case PM_SUSPEND_PREPARE:
1269 case PM_HIBERNATION_PREPARE:
1270 cpu_hotplug_disable();
1273 case PM_POST_SUSPEND:
1274 case PM_POST_HIBERNATION:
1275 cpu_hotplug_enable();
1286 static int __init cpu_hotplug_pm_sync_init(void)
1289 * cpu_hotplug_pm_callback has higher priority than x86
1290 * bsp_pm_callback which depends on cpu_hotplug_pm_callback
1291 * to disable cpu hotplug to avoid cpu hotplug race.
1293 pm_notifier(cpu_hotplug_pm_callback, 0);
1296 core_initcall(cpu_hotplug_pm_sync_init);
1298 #endif /* CONFIG_PM_SLEEP_SMP */
1302 #endif /* CONFIG_SMP */
1304 /* Boot processor state steps */
1305 static struct cpuhp_step cpuhp_bp_states[] = {
1308 .startup.single = NULL,
1309 .teardown.single = NULL,
1312 [CPUHP_CREATE_THREADS]= {
1313 .name = "threads:prepare",
1314 .startup.single = smpboot_create_threads,
1315 .teardown.single = NULL,
1318 [CPUHP_PERF_PREPARE] = {
1319 .name = "perf:prepare",
1320 .startup.single = perf_event_init_cpu,
1321 .teardown.single = perf_event_exit_cpu,
1323 [CPUHP_WORKQUEUE_PREP] = {
1324 .name = "workqueue:prepare",
1325 .startup.single = workqueue_prepare_cpu,
1326 .teardown.single = NULL,
1328 [CPUHP_HRTIMERS_PREPARE] = {
1329 .name = "hrtimers:prepare",
1330 .startup.single = hrtimers_prepare_cpu,
1331 .teardown.single = hrtimers_dead_cpu,
1333 [CPUHP_SMPCFD_PREPARE] = {
1334 .name = "smpcfd:prepare",
1335 .startup.single = smpcfd_prepare_cpu,
1336 .teardown.single = smpcfd_dead_cpu,
1338 [CPUHP_RELAY_PREPARE] = {
1339 .name = "relay:prepare",
1340 .startup.single = relay_prepare_cpu,
1341 .teardown.single = NULL,
1343 [CPUHP_SLAB_PREPARE] = {
1344 .name = "slab:prepare",
1345 .startup.single = slab_prepare_cpu,
1346 .teardown.single = slab_dead_cpu,
1348 [CPUHP_RCUTREE_PREP] = {
1349 .name = "RCU/tree:prepare",
1350 .startup.single = rcutree_prepare_cpu,
1351 .teardown.single = rcutree_dead_cpu,
1354 * On the tear-down path, timers_dead_cpu() must be invoked
1355 * before blk_mq_queue_reinit_notify() from notify_dead(),
1356 * otherwise a RCU stall occurs.
1358 [CPUHP_TIMERS_PREPARE] = {
1359 .name = "timers:dead",
1360 .startup.single = timers_prepare_cpu,
1361 .teardown.single = timers_dead_cpu,
1363 /* Kicks the plugged cpu into life */
1364 [CPUHP_BRINGUP_CPU] = {
1365 .name = "cpu:bringup",
1366 .startup.single = bringup_cpu,
1367 .teardown.single = NULL,
1371 * Handled on controll processor until the plugged processor manages
1374 [CPUHP_TEARDOWN_CPU] = {
1375 .name = "cpu:teardown",
1376 .startup.single = NULL,
1377 .teardown.single = takedown_cpu,
1381 [CPUHP_BRINGUP_CPU] = { },
1385 /* Application processor state steps */
1386 static struct cpuhp_step cpuhp_ap_states[] = {
1388 /* Final state before CPU kills itself */
1389 [CPUHP_AP_IDLE_DEAD] = {
1390 .name = "idle:dead",
1393 * Last state before CPU enters the idle loop to die. Transient state
1394 * for synchronization.
1396 [CPUHP_AP_OFFLINE] = {
1397 .name = "ap:offline",
1400 /* First state is scheduler control. Interrupts are disabled */
1401 [CPUHP_AP_SCHED_STARTING] = {
1402 .name = "sched:starting",
1403 .startup.single = sched_cpu_starting,
1404 .teardown.single = sched_cpu_dying,
1406 [CPUHP_AP_RCUTREE_DYING] = {
1407 .name = "RCU/tree:dying",
1408 .startup.single = NULL,
1409 .teardown.single = rcutree_dying_cpu,
1411 [CPUHP_AP_SMPCFD_DYING] = {
1412 .name = "smpcfd:dying",
1413 .startup.single = NULL,
1414 .teardown.single = smpcfd_dying_cpu,
1416 /* Entry state on starting. Interrupts enabled from here on. Transient
1417 * state for synchronsization */
1418 [CPUHP_AP_ONLINE] = {
1419 .name = "ap:online",
1421 /* Handle smpboot threads park/unpark */
1422 [CPUHP_AP_SMPBOOT_THREADS] = {
1423 .name = "smpboot/threads:online",
1424 .startup.single = smpboot_unpark_threads,
1425 .teardown.single = smpboot_park_threads,
1427 [CPUHP_AP_IRQ_AFFINITY_ONLINE] = {
1428 .name = "irq/affinity:online",
1429 .startup.single = irq_affinity_online_cpu,
1430 .teardown.single = NULL,
1432 [CPUHP_AP_PERF_ONLINE] = {
1433 .name = "perf:online",
1434 .startup.single = perf_event_init_cpu,
1435 .teardown.single = perf_event_exit_cpu,
1437 [CPUHP_AP_WORKQUEUE_ONLINE] = {
1438 .name = "workqueue:online",
1439 .startup.single = workqueue_online_cpu,
1440 .teardown.single = workqueue_offline_cpu,
1442 [CPUHP_AP_RCUTREE_ONLINE] = {
1443 .name = "RCU/tree:online",
1444 .startup.single = rcutree_online_cpu,
1445 .teardown.single = rcutree_offline_cpu,
1449 * The dynamically registered state space is here
1453 /* Last state is scheduler control setting the cpu active */
1454 [CPUHP_AP_ACTIVE] = {
1455 .name = "sched:active",
1456 .startup.single = sched_cpu_activate,
1457 .teardown.single = sched_cpu_deactivate,
1461 /* CPU is fully up and running. */
1464 .startup.single = NULL,
1465 .teardown.single = NULL,
1469 /* Sanity check for callbacks */
1470 static int cpuhp_cb_check(enum cpuhp_state state)
1472 if (state <= CPUHP_OFFLINE || state >= CPUHP_ONLINE)
1478 * Returns a free for dynamic slot assignment of the Online state. The states
1479 * are protected by the cpuhp_slot_states mutex and an empty slot is identified
1480 * by having no name assigned.
1482 static int cpuhp_reserve_state(enum cpuhp_state state)
1484 enum cpuhp_state i, end;
1485 struct cpuhp_step *step;
1488 case CPUHP_AP_ONLINE_DYN:
1489 step = cpuhp_ap_states + CPUHP_AP_ONLINE_DYN;
1490 end = CPUHP_AP_ONLINE_DYN_END;
1492 case CPUHP_BP_PREPARE_DYN:
1493 step = cpuhp_bp_states + CPUHP_BP_PREPARE_DYN;
1494 end = CPUHP_BP_PREPARE_DYN_END;
1500 for (i = state; i <= end; i++, step++) {
1504 WARN(1, "No more dynamic states available for CPU hotplug\n");
1508 static int cpuhp_store_callbacks(enum cpuhp_state state, const char *name,
1509 int (*startup)(unsigned int cpu),
1510 int (*teardown)(unsigned int cpu),
1511 bool multi_instance)
1513 /* (Un)Install the callbacks for further cpu hotplug operations */
1514 struct cpuhp_step *sp;
1518 * If name is NULL, then the state gets removed.
1520 * CPUHP_AP_ONLINE_DYN and CPUHP_BP_PREPARE_DYN are handed out on
1521 * the first allocation from these dynamic ranges, so the removal
1522 * would trigger a new allocation and clear the wrong (already
1523 * empty) state, leaving the callbacks of the to be cleared state
1524 * dangling, which causes wreckage on the next hotplug operation.
1526 if (name && (state == CPUHP_AP_ONLINE_DYN ||
1527 state == CPUHP_BP_PREPARE_DYN)) {
1528 ret = cpuhp_reserve_state(state);
1533 sp = cpuhp_get_step(state);
1534 if (name && sp->name)
1537 sp->startup.single = startup;
1538 sp->teardown.single = teardown;
1540 sp->multi_instance = multi_instance;
1541 INIT_HLIST_HEAD(&sp->list);
1545 static void *cpuhp_get_teardown_cb(enum cpuhp_state state)
1547 return cpuhp_get_step(state)->teardown.single;
1551 * Call the startup/teardown function for a step either on the AP or
1552 * on the current CPU.
1554 static int cpuhp_issue_call(int cpu, enum cpuhp_state state, bool bringup,
1555 struct hlist_node *node)
1557 struct cpuhp_step *sp = cpuhp_get_step(state);
1561 * If there's nothing to do, we done.
1562 * Relies on the union for multi_instance.
1564 if ((bringup && !sp->startup.single) ||
1565 (!bringup && !sp->teardown.single))
1568 * The non AP bound callbacks can fail on bringup. On teardown
1569 * e.g. module removal we crash for now.
1572 if (cpuhp_is_ap_state(state))
1573 ret = cpuhp_invoke_ap_callback(cpu, state, bringup, node);
1575 ret = cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
1577 ret = cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
1579 BUG_ON(ret && !bringup);
1584 * Called from __cpuhp_setup_state on a recoverable failure.
1586 * Note: The teardown callbacks for rollback are not allowed to fail!
1588 static void cpuhp_rollback_install(int failedcpu, enum cpuhp_state state,
1589 struct hlist_node *node)
1593 /* Roll back the already executed steps on the other cpus */
1594 for_each_present_cpu(cpu) {
1595 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1596 int cpustate = st->state;
1598 if (cpu >= failedcpu)
1601 /* Did we invoke the startup call on that cpu ? */
1602 if (cpustate >= state)
1603 cpuhp_issue_call(cpu, state, false, node);
1607 int __cpuhp_state_add_instance_cpuslocked(enum cpuhp_state state,
1608 struct hlist_node *node,
1611 struct cpuhp_step *sp;
1615 lockdep_assert_cpus_held();
1617 sp = cpuhp_get_step(state);
1618 if (sp->multi_instance == false)
1621 mutex_lock(&cpuhp_state_mutex);
1623 if (!invoke || !sp->startup.multi)
1627 * Try to call the startup callback for each present cpu
1628 * depending on the hotplug state of the cpu.
1630 for_each_present_cpu(cpu) {
1631 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1632 int cpustate = st->state;
1634 if (cpustate < state)
1637 ret = cpuhp_issue_call(cpu, state, true, node);
1639 if (sp->teardown.multi)
1640 cpuhp_rollback_install(cpu, state, node);
1646 hlist_add_head(node, &sp->list);
1648 mutex_unlock(&cpuhp_state_mutex);
1652 int __cpuhp_state_add_instance(enum cpuhp_state state, struct hlist_node *node,
1658 ret = __cpuhp_state_add_instance_cpuslocked(state, node, invoke);
1662 EXPORT_SYMBOL_GPL(__cpuhp_state_add_instance);
1665 * __cpuhp_setup_state_cpuslocked - Setup the callbacks for an hotplug machine state
1666 * @state: The state to setup
1667 * @invoke: If true, the startup function is invoked for cpus where
1668 * cpu state >= @state
1669 * @startup: startup callback function
1670 * @teardown: teardown callback function
1671 * @multi_instance: State is set up for multiple instances which get
1674 * The caller needs to hold cpus read locked while calling this function.
1677 * Positive state number if @state is CPUHP_AP_ONLINE_DYN
1678 * 0 for all other states
1679 * On failure: proper (negative) error code
1681 int __cpuhp_setup_state_cpuslocked(enum cpuhp_state state,
1682 const char *name, bool invoke,
1683 int (*startup)(unsigned int cpu),
1684 int (*teardown)(unsigned int cpu),
1685 bool multi_instance)
1690 lockdep_assert_cpus_held();
1692 if (cpuhp_cb_check(state) || !name)
1695 mutex_lock(&cpuhp_state_mutex);
1697 ret = cpuhp_store_callbacks(state, name, startup, teardown,
1700 dynstate = state == CPUHP_AP_ONLINE_DYN;
1701 if (ret > 0 && dynstate) {
1706 if (ret || !invoke || !startup)
1710 * Try to call the startup callback for each present cpu
1711 * depending on the hotplug state of the cpu.
1713 for_each_present_cpu(cpu) {
1714 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1715 int cpustate = st->state;
1717 if (cpustate < state)
1720 ret = cpuhp_issue_call(cpu, state, true, NULL);
1723 cpuhp_rollback_install(cpu, state, NULL);
1724 cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
1729 mutex_unlock(&cpuhp_state_mutex);
1731 * If the requested state is CPUHP_AP_ONLINE_DYN, return the
1732 * dynamically allocated state in case of success.
1734 if (!ret && dynstate)
1738 EXPORT_SYMBOL(__cpuhp_setup_state_cpuslocked);
1740 int __cpuhp_setup_state(enum cpuhp_state state,
1741 const char *name, bool invoke,
1742 int (*startup)(unsigned int cpu),
1743 int (*teardown)(unsigned int cpu),
1744 bool multi_instance)
1749 ret = __cpuhp_setup_state_cpuslocked(state, name, invoke, startup,
1750 teardown, multi_instance);
1754 EXPORT_SYMBOL(__cpuhp_setup_state);
1756 int __cpuhp_state_remove_instance(enum cpuhp_state state,
1757 struct hlist_node *node, bool invoke)
1759 struct cpuhp_step *sp = cpuhp_get_step(state);
1762 BUG_ON(cpuhp_cb_check(state));
1764 if (!sp->multi_instance)
1768 mutex_lock(&cpuhp_state_mutex);
1770 if (!invoke || !cpuhp_get_teardown_cb(state))
1773 * Call the teardown callback for each present cpu depending
1774 * on the hotplug state of the cpu. This function is not
1775 * allowed to fail currently!
1777 for_each_present_cpu(cpu) {
1778 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1779 int cpustate = st->state;
1781 if (cpustate >= state)
1782 cpuhp_issue_call(cpu, state, false, node);
1787 mutex_unlock(&cpuhp_state_mutex);
1792 EXPORT_SYMBOL_GPL(__cpuhp_state_remove_instance);
1795 * __cpuhp_remove_state_cpuslocked - Remove the callbacks for an hotplug machine state
1796 * @state: The state to remove
1797 * @invoke: If true, the teardown function is invoked for cpus where
1798 * cpu state >= @state
1800 * The caller needs to hold cpus read locked while calling this function.
1801 * The teardown callback is currently not allowed to fail. Think
1802 * about module removal!
1804 void __cpuhp_remove_state_cpuslocked(enum cpuhp_state state, bool invoke)
1806 struct cpuhp_step *sp = cpuhp_get_step(state);
1809 BUG_ON(cpuhp_cb_check(state));
1811 lockdep_assert_cpus_held();
1813 mutex_lock(&cpuhp_state_mutex);
1814 if (sp->multi_instance) {
1815 WARN(!hlist_empty(&sp->list),
1816 "Error: Removing state %d which has instances left.\n",
1821 if (!invoke || !cpuhp_get_teardown_cb(state))
1825 * Call the teardown callback for each present cpu depending
1826 * on the hotplug state of the cpu. This function is not
1827 * allowed to fail currently!
1829 for_each_present_cpu(cpu) {
1830 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1831 int cpustate = st->state;
1833 if (cpustate >= state)
1834 cpuhp_issue_call(cpu, state, false, NULL);
1837 cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
1838 mutex_unlock(&cpuhp_state_mutex);
1840 EXPORT_SYMBOL(__cpuhp_remove_state_cpuslocked);
1842 void __cpuhp_remove_state(enum cpuhp_state state, bool invoke)
1845 __cpuhp_remove_state_cpuslocked(state, invoke);
1848 EXPORT_SYMBOL(__cpuhp_remove_state);
1850 #if defined(CONFIG_SYSFS) && defined(CONFIG_HOTPLUG_CPU)
1851 static ssize_t show_cpuhp_state(struct device *dev,
1852 struct device_attribute *attr, char *buf)
1854 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
1856 return sprintf(buf, "%d\n", st->state);
1858 static DEVICE_ATTR(state, 0444, show_cpuhp_state, NULL);
1860 static ssize_t write_cpuhp_target(struct device *dev,
1861 struct device_attribute *attr,
1862 const char *buf, size_t count)
1864 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
1865 struct cpuhp_step *sp;
1868 ret = kstrtoint(buf, 10, &target);
1872 #ifdef CONFIG_CPU_HOTPLUG_STATE_CONTROL
1873 if (target < CPUHP_OFFLINE || target > CPUHP_ONLINE)
1876 if (target != CPUHP_OFFLINE && target != CPUHP_ONLINE)
1880 ret = lock_device_hotplug_sysfs();
1884 mutex_lock(&cpuhp_state_mutex);
1885 sp = cpuhp_get_step(target);
1886 ret = !sp->name || sp->cant_stop ? -EINVAL : 0;
1887 mutex_unlock(&cpuhp_state_mutex);
1891 if (st->state < target)
1892 ret = do_cpu_up(dev->id, target);
1894 ret = do_cpu_down(dev->id, target);
1896 unlock_device_hotplug();
1897 return ret ? ret : count;
1900 static ssize_t show_cpuhp_target(struct device *dev,
1901 struct device_attribute *attr, char *buf)
1903 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
1905 return sprintf(buf, "%d\n", st->target);
1907 static DEVICE_ATTR(target, 0644, show_cpuhp_target, write_cpuhp_target);
1910 static ssize_t write_cpuhp_fail(struct device *dev,
1911 struct device_attribute *attr,
1912 const char *buf, size_t count)
1914 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
1915 struct cpuhp_step *sp;
1918 ret = kstrtoint(buf, 10, &fail);
1923 * Cannot fail STARTING/DYING callbacks.
1925 if (cpuhp_is_atomic_state(fail))
1929 * Cannot fail anything that doesn't have callbacks.
1931 mutex_lock(&cpuhp_state_mutex);
1932 sp = cpuhp_get_step(fail);
1933 if (!sp->startup.single && !sp->teardown.single)
1935 mutex_unlock(&cpuhp_state_mutex);
1944 static ssize_t show_cpuhp_fail(struct device *dev,
1945 struct device_attribute *attr, char *buf)
1947 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
1949 return sprintf(buf, "%d\n", st->fail);
1952 static DEVICE_ATTR(fail, 0644, show_cpuhp_fail, write_cpuhp_fail);
1954 static struct attribute *cpuhp_cpu_attrs[] = {
1955 &dev_attr_state.attr,
1956 &dev_attr_target.attr,
1957 &dev_attr_fail.attr,
1961 static const struct attribute_group cpuhp_cpu_attr_group = {
1962 .attrs = cpuhp_cpu_attrs,
1967 static ssize_t show_cpuhp_states(struct device *dev,
1968 struct device_attribute *attr, char *buf)
1970 ssize_t cur, res = 0;
1973 mutex_lock(&cpuhp_state_mutex);
1974 for (i = CPUHP_OFFLINE; i <= CPUHP_ONLINE; i++) {
1975 struct cpuhp_step *sp = cpuhp_get_step(i);
1978 cur = sprintf(buf, "%3d: %s\n", i, sp->name);
1983 mutex_unlock(&cpuhp_state_mutex);
1986 static DEVICE_ATTR(states, 0444, show_cpuhp_states, NULL);
1988 static struct attribute *cpuhp_cpu_root_attrs[] = {
1989 &dev_attr_states.attr,
1993 static const struct attribute_group cpuhp_cpu_root_attr_group = {
1994 .attrs = cpuhp_cpu_root_attrs,
1999 #ifdef CONFIG_HOTPLUG_SMT
2001 static const char *smt_states[] = {
2002 [CPU_SMT_ENABLED] = "on",
2003 [CPU_SMT_DISABLED] = "off",
2004 [CPU_SMT_FORCE_DISABLED] = "forceoff",
2005 [CPU_SMT_NOT_SUPPORTED] = "notsupported",
2009 show_smt_control(struct device *dev, struct device_attribute *attr, char *buf)
2011 return snprintf(buf, PAGE_SIZE - 2, "%s\n", smt_states[cpu_smt_control]);
2014 static void cpuhp_offline_cpu_device(unsigned int cpu)
2016 struct device *dev = get_cpu_device(cpu);
2018 dev->offline = true;
2019 /* Tell user space about the state change */
2020 kobject_uevent(&dev->kobj, KOBJ_OFFLINE);
2023 static void cpuhp_online_cpu_device(unsigned int cpu)
2025 struct device *dev = get_cpu_device(cpu);
2027 dev->offline = false;
2028 /* Tell user space about the state change */
2029 kobject_uevent(&dev->kobj, KOBJ_ONLINE);
2032 static int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval)
2036 cpu_maps_update_begin();
2037 for_each_online_cpu(cpu) {
2038 if (topology_is_primary_thread(cpu))
2040 ret = cpu_down_maps_locked(cpu, CPUHP_OFFLINE);
2044 * As this needs to hold the cpu maps lock it's impossible
2045 * to call device_offline() because that ends up calling
2046 * cpu_down() which takes cpu maps lock. cpu maps lock
2047 * needs to be held as this might race against in kernel
2048 * abusers of the hotplug machinery (thermal management).
2050 * So nothing would update device:offline state. That would
2051 * leave the sysfs entry stale and prevent onlining after
2052 * smt control has been changed to 'off' again. This is
2053 * called under the sysfs hotplug lock, so it is properly
2054 * serialized against the regular offline usage.
2056 cpuhp_offline_cpu_device(cpu);
2059 cpu_smt_control = ctrlval;
2062 cpu_maps_update_done();
2066 static int cpuhp_smt_enable(void)
2070 cpu_maps_update_begin();
2071 cpu_smt_control = CPU_SMT_ENABLED;
2073 for_each_present_cpu(cpu) {
2074 /* Skip online CPUs and CPUs on offline nodes */
2075 if (cpu_online(cpu) || !node_online(cpu_to_node(cpu)))
2077 ret = _cpu_up(cpu, 0, CPUHP_ONLINE);
2080 /* See comment in cpuhp_smt_disable() */
2081 cpuhp_online_cpu_device(cpu);
2083 cpu_maps_update_done();
2088 store_smt_control(struct device *dev, struct device_attribute *attr,
2089 const char *buf, size_t count)
2093 if (sysfs_streq(buf, "on"))
2094 ctrlval = CPU_SMT_ENABLED;
2095 else if (sysfs_streq(buf, "off"))
2096 ctrlval = CPU_SMT_DISABLED;
2097 else if (sysfs_streq(buf, "forceoff"))
2098 ctrlval = CPU_SMT_FORCE_DISABLED;
2102 if (cpu_smt_control == CPU_SMT_FORCE_DISABLED)
2105 if (cpu_smt_control == CPU_SMT_NOT_SUPPORTED)
2108 ret = lock_device_hotplug_sysfs();
2112 if (ctrlval != cpu_smt_control) {
2114 case CPU_SMT_ENABLED:
2115 ret = cpuhp_smt_enable();
2117 case CPU_SMT_DISABLED:
2118 case CPU_SMT_FORCE_DISABLED:
2119 ret = cpuhp_smt_disable(ctrlval);
2124 unlock_device_hotplug();
2125 return ret ? ret : count;
2127 static DEVICE_ATTR(control, 0644, show_smt_control, store_smt_control);
2130 show_smt_active(struct device *dev, struct device_attribute *attr, char *buf)
2132 bool active = topology_max_smt_threads() > 1;
2134 return snprintf(buf, PAGE_SIZE - 2, "%d\n", active);
2136 static DEVICE_ATTR(active, 0444, show_smt_active, NULL);
2138 static struct attribute *cpuhp_smt_attrs[] = {
2139 &dev_attr_control.attr,
2140 &dev_attr_active.attr,
2144 static const struct attribute_group cpuhp_smt_attr_group = {
2145 .attrs = cpuhp_smt_attrs,
2150 static int __init cpu_smt_state_init(void)
2152 return sysfs_create_group(&cpu_subsys.dev_root->kobj,
2153 &cpuhp_smt_attr_group);
2157 static inline int cpu_smt_state_init(void) { return 0; }
2160 static int __init cpuhp_sysfs_init(void)
2164 ret = cpu_smt_state_init();
2168 ret = sysfs_create_group(&cpu_subsys.dev_root->kobj,
2169 &cpuhp_cpu_root_attr_group);
2173 for_each_possible_cpu(cpu) {
2174 struct device *dev = get_cpu_device(cpu);
2178 ret = sysfs_create_group(&dev->kobj, &cpuhp_cpu_attr_group);
2184 device_initcall(cpuhp_sysfs_init);
2188 * cpu_bit_bitmap[] is a special, "compressed" data structure that
2189 * represents all NR_CPUS bits binary values of 1<<nr.
2191 * It is used by cpumask_of() to get a constant address to a CPU
2192 * mask value that has a single bit set only.
2195 /* cpu_bit_bitmap[0] is empty - so we can back into it */
2196 #define MASK_DECLARE_1(x) [x+1][0] = (1UL << (x))
2197 #define MASK_DECLARE_2(x) MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
2198 #define MASK_DECLARE_4(x) MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
2199 #define MASK_DECLARE_8(x) MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
2201 const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
2203 MASK_DECLARE_8(0), MASK_DECLARE_8(8),
2204 MASK_DECLARE_8(16), MASK_DECLARE_8(24),
2205 #if BITS_PER_LONG > 32
2206 MASK_DECLARE_8(32), MASK_DECLARE_8(40),
2207 MASK_DECLARE_8(48), MASK_DECLARE_8(56),
2210 EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
2212 const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
2213 EXPORT_SYMBOL(cpu_all_bits);
2215 #ifdef CONFIG_INIT_ALL_POSSIBLE
2216 struct cpumask __cpu_possible_mask __read_mostly
2219 struct cpumask __cpu_possible_mask __read_mostly;
2221 EXPORT_SYMBOL(__cpu_possible_mask);
2223 struct cpumask __cpu_online_mask __read_mostly;
2224 EXPORT_SYMBOL(__cpu_online_mask);
2226 struct cpumask __cpu_present_mask __read_mostly;
2227 EXPORT_SYMBOL(__cpu_present_mask);
2229 struct cpumask __cpu_active_mask __read_mostly;
2230 EXPORT_SYMBOL(__cpu_active_mask);
2232 void init_cpu_present(const struct cpumask *src)
2234 cpumask_copy(&__cpu_present_mask, src);
2237 void init_cpu_possible(const struct cpumask *src)
2239 cpumask_copy(&__cpu_possible_mask, src);
2242 void init_cpu_online(const struct cpumask *src)
2244 cpumask_copy(&__cpu_online_mask, src);
2248 * Activate the first processor.
2250 void __init boot_cpu_init(void)
2252 int cpu = smp_processor_id();
2254 /* Mark the boot cpu "present", "online" etc for SMP and UP case */
2255 set_cpu_online(cpu, true);
2256 set_cpu_active(cpu, true);
2257 set_cpu_present(cpu, true);
2258 set_cpu_possible(cpu, true);
2261 __boot_cpu_id = cpu;
2266 * Must be called _AFTER_ setting up the per_cpu areas
2268 void __init boot_cpu_hotplug_init(void)
2271 this_cpu_write(cpuhp_state.booted_once, true);
2273 this_cpu_write(cpuhp_state.state, CPUHP_ONLINE);