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.h>
11 #include <linux/unistd.h>
12 #include <linux/cpu.h>
13 #include <linux/oom.h>
14 #include <linux/rcupdate.h>
15 #include <linux/export.h>
16 #include <linux/bug.h>
17 #include <linux/kthread.h>
18 #include <linux/stop_machine.h>
19 #include <linux/mutex.h>
20 #include <linux/gfp.h>
21 #include <linux/suspend.h>
22 #include <linux/lockdep.h>
23 #include <linux/tick.h>
24 #include <linux/irq.h>
25 #include <linux/smpboot.h>
27 #include <trace/events/power.h>
28 #define CREATE_TRACE_POINTS
29 #include <trace/events/cpuhp.h>
34 * cpuhp_cpu_state - Per cpu hotplug state storage
35 * @state: The current cpu state
36 * @target: The target state
37 * @thread: Pointer to the hotplug thread
38 * @should_run: Thread should execute
39 * @cb_stat: The state for a single callback (install/uninstall)
40 * @cb: Single callback function (install/uninstall)
41 * @result: Result of the operation
42 * @done: Signal completion to the issuer of the task
44 struct cpuhp_cpu_state
{
45 enum cpuhp_state state
;
46 enum cpuhp_state target
;
48 struct task_struct
*thread
;
50 enum cpuhp_state cb_state
;
51 int (*cb
)(unsigned int cpu
);
53 struct completion done
;
57 static DEFINE_PER_CPU(struct cpuhp_cpu_state
, cpuhp_state
);
60 * cpuhp_step - Hotplug state machine step
61 * @name: Name of the step
62 * @startup: Startup function of the step
63 * @teardown: Teardown function of the step
64 * @skip_onerr: Do not invoke the functions on error rollback
65 * Will go away once the notifiers are gone
66 * @cant_stop: Bringup/teardown can't be stopped at this step
70 int (*startup
)(unsigned int cpu
);
71 int (*teardown
)(unsigned int cpu
);
76 static DEFINE_MUTEX(cpuhp_state_mutex
);
77 static struct cpuhp_step cpuhp_bp_states
[];
78 static struct cpuhp_step cpuhp_ap_states
[];
81 * cpuhp_invoke_callback _ Invoke the callbacks for a given state
82 * @cpu: The cpu for which the callback should be invoked
83 * @step: The step in the state machine
84 * @cb: The callback function to invoke
86 * Called from cpu hotplug and from the state register machinery
88 static int cpuhp_invoke_callback(unsigned int cpu
, enum cpuhp_state step
,
89 int (*cb
)(unsigned int))
91 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, cpu
);
95 trace_cpuhp_enter(cpu
, st
->target
, step
, cb
);
97 trace_cpuhp_exit(cpu
, st
->state
, step
, ret
);
103 /* Serializes the updates to cpu_online_mask, cpu_present_mask */
104 static DEFINE_MUTEX(cpu_add_remove_lock
);
105 bool cpuhp_tasks_frozen
;
106 EXPORT_SYMBOL_GPL(cpuhp_tasks_frozen
);
109 * The following two APIs (cpu_maps_update_begin/done) must be used when
110 * attempting to serialize the updates to cpu_online_mask & cpu_present_mask.
111 * The APIs cpu_notifier_register_begin/done() must be used to protect CPU
112 * hotplug callback (un)registration performed using __register_cpu_notifier()
113 * or __unregister_cpu_notifier().
115 void cpu_maps_update_begin(void)
117 mutex_lock(&cpu_add_remove_lock
);
119 EXPORT_SYMBOL(cpu_notifier_register_begin
);
121 void cpu_maps_update_done(void)
123 mutex_unlock(&cpu_add_remove_lock
);
125 EXPORT_SYMBOL(cpu_notifier_register_done
);
127 static RAW_NOTIFIER_HEAD(cpu_chain
);
129 /* If set, cpu_up and cpu_down will return -EBUSY and do nothing.
130 * Should always be manipulated under cpu_add_remove_lock
132 static int cpu_hotplug_disabled
;
134 #ifdef CONFIG_HOTPLUG_CPU
137 struct task_struct
*active_writer
;
138 /* wait queue to wake up the active_writer */
139 wait_queue_head_t wq
;
140 /* verifies that no writer will get active while readers are active */
143 * Also blocks the new readers during
144 * an ongoing cpu hotplug operation.
148 #ifdef CONFIG_DEBUG_LOCK_ALLOC
149 struct lockdep_map dep_map
;
152 .active_writer
= NULL
,
153 .wq
= __WAIT_QUEUE_HEAD_INITIALIZER(cpu_hotplug
.wq
),
154 .lock
= __MUTEX_INITIALIZER(cpu_hotplug
.lock
),
155 #ifdef CONFIG_DEBUG_LOCK_ALLOC
156 .dep_map
= {.name
= "cpu_hotplug.lock" },
160 /* Lockdep annotations for get/put_online_cpus() and cpu_hotplug_begin/end() */
161 #define cpuhp_lock_acquire_read() lock_map_acquire_read(&cpu_hotplug.dep_map)
162 #define cpuhp_lock_acquire_tryread() \
163 lock_map_acquire_tryread(&cpu_hotplug.dep_map)
164 #define cpuhp_lock_acquire() lock_map_acquire(&cpu_hotplug.dep_map)
165 #define cpuhp_lock_release() lock_map_release(&cpu_hotplug.dep_map)
168 void get_online_cpus(void)
171 if (cpu_hotplug
.active_writer
== current
)
173 cpuhp_lock_acquire_read();
174 mutex_lock(&cpu_hotplug
.lock
);
175 atomic_inc(&cpu_hotplug
.refcount
);
176 mutex_unlock(&cpu_hotplug
.lock
);
178 EXPORT_SYMBOL_GPL(get_online_cpus
);
180 void put_online_cpus(void)
184 if (cpu_hotplug
.active_writer
== current
)
187 refcount
= atomic_dec_return(&cpu_hotplug
.refcount
);
188 if (WARN_ON(refcount
< 0)) /* try to fix things up */
189 atomic_inc(&cpu_hotplug
.refcount
);
191 if (refcount
<= 0 && waitqueue_active(&cpu_hotplug
.wq
))
192 wake_up(&cpu_hotplug
.wq
);
194 cpuhp_lock_release();
197 EXPORT_SYMBOL_GPL(put_online_cpus
);
200 * This ensures that the hotplug operation can begin only when the
201 * refcount goes to zero.
203 * Note that during a cpu-hotplug operation, the new readers, if any,
204 * will be blocked by the cpu_hotplug.lock
206 * Since cpu_hotplug_begin() is always called after invoking
207 * cpu_maps_update_begin(), we can be sure that only one writer is active.
209 * Note that theoretically, there is a possibility of a livelock:
210 * - Refcount goes to zero, last reader wakes up the sleeping
212 * - Last reader unlocks the cpu_hotplug.lock.
213 * - A new reader arrives at this moment, bumps up the refcount.
214 * - The writer acquires the cpu_hotplug.lock finds the refcount
215 * non zero and goes to sleep again.
217 * However, this is very difficult to achieve in practice since
218 * get_online_cpus() not an api which is called all that often.
221 void cpu_hotplug_begin(void)
225 cpu_hotplug
.active_writer
= current
;
226 cpuhp_lock_acquire();
229 mutex_lock(&cpu_hotplug
.lock
);
230 prepare_to_wait(&cpu_hotplug
.wq
, &wait
, TASK_UNINTERRUPTIBLE
);
231 if (likely(!atomic_read(&cpu_hotplug
.refcount
)))
233 mutex_unlock(&cpu_hotplug
.lock
);
236 finish_wait(&cpu_hotplug
.wq
, &wait
);
239 void cpu_hotplug_done(void)
241 cpu_hotplug
.active_writer
= NULL
;
242 mutex_unlock(&cpu_hotplug
.lock
);
243 cpuhp_lock_release();
247 * Wait for currently running CPU hotplug operations to complete (if any) and
248 * disable future CPU hotplug (from sysfs). The 'cpu_add_remove_lock' protects
249 * the 'cpu_hotplug_disabled' flag. The same lock is also acquired by the
250 * hotplug path before performing hotplug operations. So acquiring that lock
251 * guarantees mutual exclusion from any currently running hotplug operations.
253 void cpu_hotplug_disable(void)
255 cpu_maps_update_begin();
256 cpu_hotplug_disabled
++;
257 cpu_maps_update_done();
259 EXPORT_SYMBOL_GPL(cpu_hotplug_disable
);
261 void cpu_hotplug_enable(void)
263 cpu_maps_update_begin();
264 WARN_ON(--cpu_hotplug_disabled
< 0);
265 cpu_maps_update_done();
267 EXPORT_SYMBOL_GPL(cpu_hotplug_enable
);
268 #endif /* CONFIG_HOTPLUG_CPU */
270 /* Need to know about CPUs going up/down? */
271 int register_cpu_notifier(struct notifier_block
*nb
)
274 cpu_maps_update_begin();
275 ret
= raw_notifier_chain_register(&cpu_chain
, nb
);
276 cpu_maps_update_done();
280 int __register_cpu_notifier(struct notifier_block
*nb
)
282 return raw_notifier_chain_register(&cpu_chain
, nb
);
285 static int __cpu_notify(unsigned long val
, unsigned int cpu
, int nr_to_call
,
288 unsigned long mod
= cpuhp_tasks_frozen
? CPU_TASKS_FROZEN
: 0;
289 void *hcpu
= (void *)(long)cpu
;
293 ret
= __raw_notifier_call_chain(&cpu_chain
, val
| mod
, hcpu
, nr_to_call
,
296 return notifier_to_errno(ret
);
299 static int cpu_notify(unsigned long val
, unsigned int cpu
)
301 return __cpu_notify(val
, cpu
, -1, NULL
);
304 /* Notifier wrappers for transitioning to state machine */
305 static int notify_prepare(unsigned int cpu
)
310 ret
= __cpu_notify(CPU_UP_PREPARE
, cpu
, -1, &nr_calls
);
313 printk(KERN_WARNING
"%s: attempt to bring up CPU %u failed\n",
315 __cpu_notify(CPU_UP_CANCELED
, cpu
, nr_calls
, NULL
);
320 static int notify_online(unsigned int cpu
)
322 cpu_notify(CPU_ONLINE
, cpu
);
326 static int notify_starting(unsigned int cpu
)
328 cpu_notify(CPU_STARTING
, cpu
);
332 static int bringup_wait_for_ap(unsigned int cpu
)
334 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, cpu
);
336 wait_for_completion(&st
->done
);
340 static int bringup_cpu(unsigned int cpu
)
342 struct task_struct
*idle
= idle_thread_get(cpu
);
345 /* Arch-specific enabling code. */
346 ret
= __cpu_up(cpu
, idle
);
348 cpu_notify(CPU_UP_CANCELED
, cpu
);
351 ret
= bringup_wait_for_ap(cpu
);
352 BUG_ON(!cpu_online(cpu
));
357 * Hotplug state machine related functions
359 static void undo_cpu_down(unsigned int cpu
, struct cpuhp_cpu_state
*st
,
360 struct cpuhp_step
*steps
)
362 for (st
->state
++; st
->state
< st
->target
; st
->state
++) {
363 struct cpuhp_step
*step
= steps
+ st
->state
;
365 if (!step
->skip_onerr
)
366 cpuhp_invoke_callback(cpu
, st
->state
, step
->startup
);
370 static int cpuhp_down_callbacks(unsigned int cpu
, struct cpuhp_cpu_state
*st
,
371 struct cpuhp_step
*steps
, enum cpuhp_state target
)
373 enum cpuhp_state prev_state
= st
->state
;
376 for (; st
->state
> target
; st
->state
--) {
377 struct cpuhp_step
*step
= steps
+ st
->state
;
379 ret
= cpuhp_invoke_callback(cpu
, st
->state
, step
->teardown
);
381 st
->target
= prev_state
;
382 undo_cpu_down(cpu
, st
, steps
);
389 static void undo_cpu_up(unsigned int cpu
, struct cpuhp_cpu_state
*st
,
390 struct cpuhp_step
*steps
)
392 for (st
->state
--; st
->state
> st
->target
; st
->state
--) {
393 struct cpuhp_step
*step
= steps
+ st
->state
;
395 if (!step
->skip_onerr
)
396 cpuhp_invoke_callback(cpu
, st
->state
, step
->teardown
);
400 static int cpuhp_up_callbacks(unsigned int cpu
, struct cpuhp_cpu_state
*st
,
401 struct cpuhp_step
*steps
, enum cpuhp_state target
)
403 enum cpuhp_state prev_state
= st
->state
;
406 while (st
->state
< target
) {
407 struct cpuhp_step
*step
;
410 step
= steps
+ st
->state
;
411 ret
= cpuhp_invoke_callback(cpu
, st
->state
, step
->startup
);
413 st
->target
= prev_state
;
414 undo_cpu_up(cpu
, st
, steps
);
422 * The cpu hotplug threads manage the bringup and teardown of the cpus
424 static void cpuhp_create(unsigned int cpu
)
426 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, cpu
);
428 init_completion(&st
->done
);
431 static int cpuhp_should_run(unsigned int cpu
)
433 struct cpuhp_cpu_state
*st
= this_cpu_ptr(&cpuhp_state
);
435 return st
->should_run
;
438 /* Execute the teardown callbacks. Used to be CPU_DOWN_PREPARE */
439 static int cpuhp_ap_offline(unsigned int cpu
, struct cpuhp_cpu_state
*st
)
441 enum cpuhp_state target
= max((int)st
->target
, CPUHP_TEARDOWN_CPU
);
443 return cpuhp_down_callbacks(cpu
, st
, cpuhp_ap_states
, target
);
446 /* Execute the online startup callbacks. Used to be CPU_ONLINE */
447 static int cpuhp_ap_online(unsigned int cpu
, struct cpuhp_cpu_state
*st
)
449 return cpuhp_up_callbacks(cpu
, st
, cpuhp_ap_states
, st
->target
);
453 * Execute teardown/startup callbacks on the plugged cpu. Also used to invoke
454 * callbacks when a state gets [un]installed at runtime.
456 static void cpuhp_thread_fun(unsigned int cpu
)
458 struct cpuhp_cpu_state
*st
= this_cpu_ptr(&cpuhp_state
);
462 * Paired with the mb() in cpuhp_kick_ap_work and
463 * cpuhp_invoke_ap_callback, so the work set is consistent visible.
469 st
->should_run
= false;
471 /* Single callback invocation for [un]install ? */
473 if (st
->cb_state
< CPUHP_AP_ONLINE
) {
475 ret
= cpuhp_invoke_callback(cpu
, st
->cb_state
, st
->cb
);
478 ret
= cpuhp_invoke_callback(cpu
, st
->cb_state
, st
->cb
);
481 /* Cannot happen .... */
482 BUG_ON(st
->state
< CPUHP_AP_ONLINE_IDLE
);
484 /* Regular hotplug work */
485 if (st
->state
< st
->target
)
486 ret
= cpuhp_ap_online(cpu
, st
);
487 else if (st
->state
> st
->target
)
488 ret
= cpuhp_ap_offline(cpu
, st
);
494 /* Invoke a single callback on a remote cpu */
495 static int cpuhp_invoke_ap_callback(int cpu
, enum cpuhp_state state
,
496 int (*cb
)(unsigned int))
498 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, cpu
);
500 if (!cpu_online(cpu
))
503 st
->cb_state
= state
;
506 * Make sure the above stores are visible before should_run becomes
507 * true. Paired with the mb() above in cpuhp_thread_fun()
510 st
->should_run
= true;
511 wake_up_process(st
->thread
);
512 wait_for_completion(&st
->done
);
516 /* Regular hotplug invocation of the AP hotplug thread */
517 static void __cpuhp_kick_ap_work(struct cpuhp_cpu_state
*st
)
522 * Make sure the above stores are visible before should_run becomes
523 * true. Paired with the mb() above in cpuhp_thread_fun()
526 st
->should_run
= true;
527 wake_up_process(st
->thread
);
530 static int cpuhp_kick_ap_work(unsigned int cpu
)
532 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, cpu
);
533 enum cpuhp_state state
= st
->state
;
535 trace_cpuhp_enter(cpu
, st
->target
, state
, cpuhp_kick_ap_work
);
536 __cpuhp_kick_ap_work(st
);
537 wait_for_completion(&st
->done
);
538 trace_cpuhp_exit(cpu
, st
->state
, state
, st
->result
);
542 static struct smp_hotplug_thread cpuhp_threads
= {
543 .store
= &cpuhp_state
.thread
,
544 .create
= &cpuhp_create
,
545 .thread_should_run
= cpuhp_should_run
,
546 .thread_fn
= cpuhp_thread_fun
,
547 .thread_comm
= "cpuhp/%u",
551 void __init
cpuhp_threads_init(void)
553 BUG_ON(smpboot_register_percpu_thread(&cpuhp_threads
));
554 kthread_unpark(this_cpu_read(cpuhp_state
.thread
));
557 #ifdef CONFIG_HOTPLUG_CPU
558 EXPORT_SYMBOL(register_cpu_notifier
);
559 EXPORT_SYMBOL(__register_cpu_notifier
);
560 void unregister_cpu_notifier(struct notifier_block
*nb
)
562 cpu_maps_update_begin();
563 raw_notifier_chain_unregister(&cpu_chain
, nb
);
564 cpu_maps_update_done();
566 EXPORT_SYMBOL(unregister_cpu_notifier
);
568 void __unregister_cpu_notifier(struct notifier_block
*nb
)
570 raw_notifier_chain_unregister(&cpu_chain
, nb
);
572 EXPORT_SYMBOL(__unregister_cpu_notifier
);
575 * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
578 * This function walks all processes, finds a valid mm struct for each one and
579 * then clears a corresponding bit in mm's cpumask. While this all sounds
580 * trivial, there are various non-obvious corner cases, which this function
581 * tries to solve in a safe manner.
583 * Also note that the function uses a somewhat relaxed locking scheme, so it may
584 * be called only for an already offlined CPU.
586 void clear_tasks_mm_cpumask(int cpu
)
588 struct task_struct
*p
;
591 * This function is called after the cpu is taken down and marked
592 * offline, so its not like new tasks will ever get this cpu set in
593 * their mm mask. -- Peter Zijlstra
594 * Thus, we may use rcu_read_lock() here, instead of grabbing
595 * full-fledged tasklist_lock.
597 WARN_ON(cpu_online(cpu
));
599 for_each_process(p
) {
600 struct task_struct
*t
;
603 * Main thread might exit, but other threads may still have
604 * a valid mm. Find one.
606 t
= find_lock_task_mm(p
);
609 cpumask_clear_cpu(cpu
, mm_cpumask(t
->mm
));
615 static inline void check_for_tasks(int dead_cpu
)
617 struct task_struct
*g
, *p
;
619 read_lock(&tasklist_lock
);
620 for_each_process_thread(g
, p
) {
624 * We do the check with unlocked task_rq(p)->lock.
625 * Order the reading to do not warn about a task,
626 * which was running on this cpu in the past, and
627 * it's just been woken on another cpu.
630 if (task_cpu(p
) != dead_cpu
)
633 pr_warn("Task %s (pid=%d) is on cpu %d (state=%ld, flags=%x)\n",
634 p
->comm
, task_pid_nr(p
), dead_cpu
, p
->state
, p
->flags
);
636 read_unlock(&tasklist_lock
);
639 static void cpu_notify_nofail(unsigned long val
, unsigned int cpu
)
641 BUG_ON(cpu_notify(val
, cpu
));
644 static int notify_down_prepare(unsigned int cpu
)
646 int err
, nr_calls
= 0;
648 err
= __cpu_notify(CPU_DOWN_PREPARE
, cpu
, -1, &nr_calls
);
651 __cpu_notify(CPU_DOWN_FAILED
, cpu
, nr_calls
, NULL
);
652 pr_warn("%s: attempt to take down CPU %u failed\n",
658 static int notify_dying(unsigned int cpu
)
660 cpu_notify(CPU_DYING
, cpu
);
664 /* Take this CPU down. */
665 static int take_cpu_down(void *_param
)
667 struct cpuhp_cpu_state
*st
= this_cpu_ptr(&cpuhp_state
);
668 enum cpuhp_state target
= max((int)st
->target
, CPUHP_AP_OFFLINE
);
669 int err
, cpu
= smp_processor_id();
671 /* Ensure this CPU doesn't handle any more interrupts. */
672 err
= __cpu_disable();
676 /* Invoke the former CPU_DYING callbacks */
677 for (; st
->state
> target
; st
->state
--) {
678 struct cpuhp_step
*step
= cpuhp_ap_states
+ st
->state
;
680 cpuhp_invoke_callback(cpu
, st
->state
, step
->teardown
);
682 /* Give up timekeeping duties */
683 tick_handover_do_timer();
684 /* Park the stopper thread */
685 stop_machine_park(cpu
);
689 static int takedown_cpu(unsigned int cpu
)
694 * By now we've cleared cpu_active_mask, wait for all preempt-disabled
695 * and RCU users of this state to go away such that all new such users
698 * For CONFIG_PREEMPT we have preemptible RCU and its sync_rcu() might
699 * not imply sync_sched(), so wait for both.
701 * Do sync before park smpboot threads to take care the rcu boost case.
703 if (IS_ENABLED(CONFIG_PREEMPT
))
704 synchronize_rcu_mult(call_rcu
, call_rcu_sched
);
708 /* Park the hotplug thread */
709 kthread_park(per_cpu_ptr(&cpuhp_state
, cpu
)->thread
);
712 * Prevent irq alloc/free while the dying cpu reorganizes the
713 * interrupt affinities.
718 * So now all preempt/rcu users must observe !cpu_active().
720 err
= stop_machine(take_cpu_down
, NULL
, cpumask_of(cpu
));
722 /* CPU didn't die: tell everyone. Can't complain. */
723 cpu_notify_nofail(CPU_DOWN_FAILED
, cpu
);
727 BUG_ON(cpu_online(cpu
));
730 * The migration_call() CPU_DYING callback will have removed all
731 * runnable tasks from the cpu, there's only the idle task left now
732 * that the migration thread is done doing the stop_machine thing.
734 * Wait for the stop thread to go away.
736 while (!per_cpu(cpu_dead_idle
, cpu
))
738 smp_mb(); /* Read from cpu_dead_idle before __cpu_die(). */
739 per_cpu(cpu_dead_idle
, cpu
) = false;
741 /* Interrupts are moved away from the dying cpu, reenable alloc/free */
744 hotplug_cpu__broadcast_tick_pull(cpu
);
745 /* This actually kills the CPU. */
748 tick_cleanup_dead_cpu(cpu
);
752 static int notify_dead(unsigned int cpu
)
754 cpu_notify_nofail(CPU_DEAD
, cpu
);
755 check_for_tasks(cpu
);
760 #define notify_down_prepare NULL
761 #define takedown_cpu NULL
762 #define notify_dead NULL
763 #define notify_dying NULL
766 #ifdef CONFIG_HOTPLUG_CPU
768 /* Requires cpu_add_remove_lock to be held */
769 static int __ref
_cpu_down(unsigned int cpu
, int tasks_frozen
,
770 enum cpuhp_state target
)
772 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, cpu
);
773 int prev_state
, ret
= 0;
774 bool hasdied
= false;
776 if (num_online_cpus() == 1)
779 if (!cpu_present(cpu
))
784 cpuhp_tasks_frozen
= tasks_frozen
;
786 prev_state
= st
->state
;
789 * If the current CPU state is in the range of the AP hotplug thread,
790 * then we need to kick the thread.
792 if (st
->state
> CPUHP_TEARDOWN_CPU
) {
793 ret
= cpuhp_kick_ap_work(cpu
);
795 * The AP side has done the error rollback already. Just
796 * return the error code..
802 * We might have stopped still in the range of the AP hotplug
803 * thread. Nothing to do anymore.
805 if (st
->state
> CPUHP_TEARDOWN_CPU
)
809 * The AP brought itself down to CPUHP_TEARDOWN_CPU. So we need
810 * to do the further cleanups.
812 ret
= cpuhp_down_callbacks(cpu
, st
, cpuhp_bp_states
, target
);
814 hasdied
= prev_state
!= st
->state
&& st
->state
== CPUHP_OFFLINE
;
817 /* This post dead nonsense must die */
819 cpu_notify_nofail(CPU_POST_DEAD
, cpu
);
823 static int do_cpu_down(unsigned int cpu
, enum cpuhp_state target
)
827 cpu_maps_update_begin();
829 if (cpu_hotplug_disabled
) {
834 err
= _cpu_down(cpu
, 0, target
);
837 cpu_maps_update_done();
840 int cpu_down(unsigned int cpu
)
842 return do_cpu_down(cpu
, CPUHP_OFFLINE
);
844 EXPORT_SYMBOL(cpu_down
);
845 #endif /*CONFIG_HOTPLUG_CPU*/
848 * notify_cpu_starting(cpu) - call the CPU_STARTING notifiers
849 * @cpu: cpu that just started
851 * This function calls the cpu_chain notifiers with CPU_STARTING.
852 * It must be called by the arch code on the new cpu, before the new cpu
853 * enables interrupts and before the "boot" cpu returns from __cpu_up().
855 void notify_cpu_starting(unsigned int cpu
)
857 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, cpu
);
858 enum cpuhp_state target
= min((int)st
->target
, CPUHP_AP_ONLINE
);
860 while (st
->state
< target
) {
861 struct cpuhp_step
*step
;
864 step
= cpuhp_ap_states
+ st
->state
;
865 cpuhp_invoke_callback(cpu
, st
->state
, step
->startup
);
870 * Called from the idle task. We need to set active here, so we can kick off
871 * the stopper thread and unpark the smpboot threads. If the target state is
872 * beyond CPUHP_AP_ONLINE_IDLE we kick cpuhp thread and let it bring up the
875 void cpuhp_online_idle(enum cpuhp_state state
)
877 struct cpuhp_cpu_state
*st
= this_cpu_ptr(&cpuhp_state
);
878 unsigned int cpu
= smp_processor_id();
880 /* Happens for the boot cpu */
881 if (state
!= CPUHP_AP_ONLINE_IDLE
)
884 st
->state
= CPUHP_AP_ONLINE_IDLE
;
886 /* The cpu is marked online, set it active now */
887 set_cpu_active(cpu
, true);
888 /* Unpark the stopper thread and the hotplug thread of this cpu */
889 stop_machine_unpark(cpu
);
890 kthread_unpark(st
->thread
);
892 /* Should we go further up ? */
893 if (st
->target
> CPUHP_AP_ONLINE_IDLE
)
894 __cpuhp_kick_ap_work(st
);
899 /* Requires cpu_add_remove_lock to be held */
900 static int _cpu_up(unsigned int cpu
, int tasks_frozen
, enum cpuhp_state target
)
902 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, cpu
);
903 struct task_struct
*idle
;
908 if (!cpu_present(cpu
)) {
914 * The caller of do_cpu_up might have raced with another
915 * caller. Ignore it for now.
917 if (st
->state
>= target
)
920 if (st
->state
== CPUHP_OFFLINE
) {
921 /* Let it fail before we try to bring the cpu up */
922 idle
= idle_thread_get(cpu
);
929 cpuhp_tasks_frozen
= tasks_frozen
;
933 * If the current CPU state is in the range of the AP hotplug thread,
934 * then we need to kick the thread once more.
936 if (st
->state
> CPUHP_BRINGUP_CPU
) {
937 ret
= cpuhp_kick_ap_work(cpu
);
939 * The AP side has done the error rollback already. Just
940 * return the error code..
947 * Try to reach the target state. We max out on the BP at
948 * CPUHP_BRINGUP_CPU. After that the AP hotplug thread is
949 * responsible for bringing it up to the target state.
951 target
= min((int)target
, CPUHP_BRINGUP_CPU
);
952 ret
= cpuhp_up_callbacks(cpu
, st
, cpuhp_bp_states
, target
);
958 static int do_cpu_up(unsigned int cpu
, enum cpuhp_state target
)
962 if (!cpu_possible(cpu
)) {
963 pr_err("can't online cpu %d because it is not configured as may-hotadd at boot time\n",
965 #if defined(CONFIG_IA64)
966 pr_err("please check additional_cpus= boot parameter\n");
971 err
= try_online_node(cpu_to_node(cpu
));
975 cpu_maps_update_begin();
977 if (cpu_hotplug_disabled
) {
982 err
= _cpu_up(cpu
, 0, target
);
984 cpu_maps_update_done();
988 int cpu_up(unsigned int cpu
)
990 return do_cpu_up(cpu
, CPUHP_ONLINE
);
992 EXPORT_SYMBOL_GPL(cpu_up
);
994 #ifdef CONFIG_PM_SLEEP_SMP
995 static cpumask_var_t frozen_cpus
;
997 int disable_nonboot_cpus(void)
999 int cpu
, first_cpu
, error
= 0;
1001 cpu_maps_update_begin();
1002 first_cpu
= cpumask_first(cpu_online_mask
);
1004 * We take down all of the non-boot CPUs in one shot to avoid races
1005 * with the userspace trying to use the CPU hotplug at the same time
1007 cpumask_clear(frozen_cpus
);
1009 pr_info("Disabling non-boot CPUs ...\n");
1010 for_each_online_cpu(cpu
) {
1011 if (cpu
== first_cpu
)
1013 trace_suspend_resume(TPS("CPU_OFF"), cpu
, true);
1014 error
= _cpu_down(cpu
, 1, CPUHP_OFFLINE
);
1015 trace_suspend_resume(TPS("CPU_OFF"), cpu
, false);
1017 cpumask_set_cpu(cpu
, frozen_cpus
);
1019 pr_err("Error taking CPU%d down: %d\n", cpu
, error
);
1025 BUG_ON(num_online_cpus() > 1);
1027 pr_err("Non-boot CPUs are not disabled\n");
1030 * Make sure the CPUs won't be enabled by someone else. We need to do
1031 * this even in case of failure as all disable_nonboot_cpus() users are
1032 * supposed to do enable_nonboot_cpus() on the failure path.
1034 cpu_hotplug_disabled
++;
1036 cpu_maps_update_done();
1040 void __weak
arch_enable_nonboot_cpus_begin(void)
1044 void __weak
arch_enable_nonboot_cpus_end(void)
1048 void enable_nonboot_cpus(void)
1052 /* Allow everyone to use the CPU hotplug again */
1053 cpu_maps_update_begin();
1054 WARN_ON(--cpu_hotplug_disabled
< 0);
1055 if (cpumask_empty(frozen_cpus
))
1058 pr_info("Enabling non-boot CPUs ...\n");
1060 arch_enable_nonboot_cpus_begin();
1062 for_each_cpu(cpu
, frozen_cpus
) {
1063 trace_suspend_resume(TPS("CPU_ON"), cpu
, true);
1064 error
= _cpu_up(cpu
, 1, CPUHP_ONLINE
);
1065 trace_suspend_resume(TPS("CPU_ON"), cpu
, false);
1067 pr_info("CPU%d is up\n", cpu
);
1070 pr_warn("Error taking CPU%d up: %d\n", cpu
, error
);
1073 arch_enable_nonboot_cpus_end();
1075 cpumask_clear(frozen_cpus
);
1077 cpu_maps_update_done();
1080 static int __init
alloc_frozen_cpus(void)
1082 if (!alloc_cpumask_var(&frozen_cpus
, GFP_KERNEL
|__GFP_ZERO
))
1086 core_initcall(alloc_frozen_cpus
);
1089 * When callbacks for CPU hotplug notifications are being executed, we must
1090 * ensure that the state of the system with respect to the tasks being frozen
1091 * or not, as reported by the notification, remains unchanged *throughout the
1092 * duration* of the execution of the callbacks.
1093 * Hence we need to prevent the freezer from racing with regular CPU hotplug.
1095 * This synchronization is implemented by mutually excluding regular CPU
1096 * hotplug and Suspend/Hibernate call paths by hooking onto the Suspend/
1097 * Hibernate notifications.
1100 cpu_hotplug_pm_callback(struct notifier_block
*nb
,
1101 unsigned long action
, void *ptr
)
1105 case PM_SUSPEND_PREPARE
:
1106 case PM_HIBERNATION_PREPARE
:
1107 cpu_hotplug_disable();
1110 case PM_POST_SUSPEND
:
1111 case PM_POST_HIBERNATION
:
1112 cpu_hotplug_enable();
1123 static int __init
cpu_hotplug_pm_sync_init(void)
1126 * cpu_hotplug_pm_callback has higher priority than x86
1127 * bsp_pm_callback which depends on cpu_hotplug_pm_callback
1128 * to disable cpu hotplug to avoid cpu hotplug race.
1130 pm_notifier(cpu_hotplug_pm_callback
, 0);
1133 core_initcall(cpu_hotplug_pm_sync_init
);
1135 #endif /* CONFIG_PM_SLEEP_SMP */
1137 #endif /* CONFIG_SMP */
1139 /* Boot processor state steps */
1140 static struct cpuhp_step cpuhp_bp_states
[] = {
1147 [CPUHP_CREATE_THREADS
]= {
1148 .name
= "threads:create",
1149 .startup
= smpboot_create_threads
,
1153 [CPUHP_NOTIFY_PREPARE
] = {
1154 .name
= "notify:prepare",
1155 .startup
= notify_prepare
,
1156 .teardown
= notify_dead
,
1160 [CPUHP_BRINGUP_CPU
] = {
1161 .name
= "cpu:bringup",
1162 .startup
= bringup_cpu
,
1166 [CPUHP_TEARDOWN_CPU
] = {
1167 .name
= "cpu:teardown",
1169 .teardown
= takedown_cpu
,
1175 /* Application processor state steps */
1176 static struct cpuhp_step cpuhp_ap_states
[] = {
1178 [CPUHP_AP_NOTIFY_STARTING
] = {
1179 .name
= "notify:starting",
1180 .startup
= notify_starting
,
1181 .teardown
= notify_dying
,
1185 [CPUHP_AP_SMPBOOT_THREADS
] = {
1186 .name
= "smpboot:threads",
1187 .startup
= smpboot_unpark_threads
,
1188 .teardown
= smpboot_park_threads
,
1190 [CPUHP_AP_NOTIFY_ONLINE
] = {
1191 .name
= "notify:online",
1192 .startup
= notify_online
,
1193 .teardown
= notify_down_prepare
,
1203 /* Sanity check for callbacks */
1204 static int cpuhp_cb_check(enum cpuhp_state state
)
1206 if (state
<= CPUHP_OFFLINE
|| state
>= CPUHP_ONLINE
)
1211 static bool cpuhp_is_ap_state(enum cpuhp_state state
)
1213 if (state
>= CPUHP_AP_OFFLINE
&& state
<= CPUHP_AP_ONLINE
)
1215 return state
> CPUHP_BRINGUP_CPU
;
1218 static struct cpuhp_step
*cpuhp_get_step(enum cpuhp_state state
)
1220 struct cpuhp_step
*sp
;
1222 sp
= cpuhp_is_ap_state(state
) ? cpuhp_ap_states
: cpuhp_bp_states
;
1226 static void cpuhp_store_callbacks(enum cpuhp_state state
,
1228 int (*startup
)(unsigned int cpu
),
1229 int (*teardown
)(unsigned int cpu
))
1231 /* (Un)Install the callbacks for further cpu hotplug operations */
1232 struct cpuhp_step
*sp
;
1234 mutex_lock(&cpuhp_state_mutex
);
1235 sp
= cpuhp_get_step(state
);
1236 sp
->startup
= startup
;
1237 sp
->teardown
= teardown
;
1239 mutex_unlock(&cpuhp_state_mutex
);
1242 static void *cpuhp_get_teardown_cb(enum cpuhp_state state
)
1244 return cpuhp_get_step(state
)->teardown
;
1248 * Call the startup/teardown function for a step either on the AP or
1249 * on the current CPU.
1251 static int cpuhp_issue_call(int cpu
, enum cpuhp_state state
,
1252 int (*cb
)(unsigned int), bool bringup
)
1259 * The non AP bound callbacks can fail on bringup. On teardown
1260 * e.g. module removal we crash for now.
1263 if (cpuhp_is_ap_state(state
))
1264 ret
= cpuhp_invoke_ap_callback(cpu
, state
, cb
);
1266 ret
= cpuhp_invoke_callback(cpu
, state
, cb
);
1268 ret
= cpuhp_invoke_callback(cpu
, state
, cb
);
1270 BUG_ON(ret
&& !bringup
);
1275 * Called from __cpuhp_setup_state on a recoverable failure.
1277 * Note: The teardown callbacks for rollback are not allowed to fail!
1279 static void cpuhp_rollback_install(int failedcpu
, enum cpuhp_state state
,
1280 int (*teardown
)(unsigned int cpu
))
1287 /* Roll back the already executed steps on the other cpus */
1288 for_each_present_cpu(cpu
) {
1289 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, cpu
);
1290 int cpustate
= st
->state
;
1292 if (cpu
>= failedcpu
)
1295 /* Did we invoke the startup call on that cpu ? */
1296 if (cpustate
>= state
)
1297 cpuhp_issue_call(cpu
, state
, teardown
, false);
1302 * Returns a free for dynamic slot assignment of the Online state. The states
1303 * are protected by the cpuhp_slot_states mutex and an empty slot is identified
1304 * by having no name assigned.
1306 static int cpuhp_reserve_state(enum cpuhp_state state
)
1310 mutex_lock(&cpuhp_state_mutex
);
1311 for (i
= CPUHP_AP_ONLINE_DYN
; i
<= CPUHP_AP_ONLINE_DYN_END
; i
++) {
1312 if (cpuhp_ap_states
[i
].name
)
1315 cpuhp_ap_states
[i
].name
= "Reserved";
1316 mutex_unlock(&cpuhp_state_mutex
);
1319 mutex_unlock(&cpuhp_state_mutex
);
1320 WARN(1, "No more dynamic states available for CPU hotplug\n");
1325 * __cpuhp_setup_state - Setup the callbacks for an hotplug machine state
1326 * @state: The state to setup
1327 * @invoke: If true, the startup function is invoked for cpus where
1328 * cpu state >= @state
1329 * @startup: startup callback function
1330 * @teardown: teardown callback function
1332 * Returns 0 if successful, otherwise a proper error code
1334 int __cpuhp_setup_state(enum cpuhp_state state
,
1335 const char *name
, bool invoke
,
1336 int (*startup
)(unsigned int cpu
),
1337 int (*teardown
)(unsigned int cpu
))
1342 if (cpuhp_cb_check(state
) || !name
)
1347 /* currently assignments for the ONLINE state are possible */
1348 if (state
== CPUHP_AP_ONLINE_DYN
) {
1350 ret
= cpuhp_reserve_state(state
);
1356 cpuhp_store_callbacks(state
, name
, startup
, teardown
);
1358 if (!invoke
|| !startup
)
1362 * Try to call the startup callback for each present cpu
1363 * depending on the hotplug state of the cpu.
1365 for_each_present_cpu(cpu
) {
1366 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, cpu
);
1367 int cpustate
= st
->state
;
1369 if (cpustate
< state
)
1372 ret
= cpuhp_issue_call(cpu
, state
, startup
, true);
1374 cpuhp_rollback_install(cpu
, state
, teardown
);
1375 cpuhp_store_callbacks(state
, NULL
, NULL
, NULL
);
1381 if (!ret
&& dyn_state
)
1385 EXPORT_SYMBOL(__cpuhp_setup_state
);
1388 * __cpuhp_remove_state - Remove the callbacks for an hotplug machine state
1389 * @state: The state to remove
1390 * @invoke: If true, the teardown function is invoked for cpus where
1391 * cpu state >= @state
1393 * The teardown callback is currently not allowed to fail. Think
1394 * about module removal!
1396 void __cpuhp_remove_state(enum cpuhp_state state
, bool invoke
)
1398 int (*teardown
)(unsigned int cpu
) = cpuhp_get_teardown_cb(state
);
1401 BUG_ON(cpuhp_cb_check(state
));
1405 if (!invoke
|| !teardown
)
1409 * Call the teardown callback for each present cpu depending
1410 * on the hotplug state of the cpu. This function is not
1411 * allowed to fail currently!
1413 for_each_present_cpu(cpu
) {
1414 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, cpu
);
1415 int cpustate
= st
->state
;
1417 if (cpustate
>= state
)
1418 cpuhp_issue_call(cpu
, state
, teardown
, false);
1421 cpuhp_store_callbacks(state
, NULL
, NULL
, NULL
);
1424 EXPORT_SYMBOL(__cpuhp_remove_state
);
1426 #if defined(CONFIG_SYSFS) && defined(CONFIG_HOTPLUG_CPU)
1427 static ssize_t
show_cpuhp_state(struct device
*dev
,
1428 struct device_attribute
*attr
, char *buf
)
1430 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, dev
->id
);
1432 return sprintf(buf
, "%d\n", st
->state
);
1434 static DEVICE_ATTR(state
, 0444, show_cpuhp_state
, NULL
);
1436 static ssize_t
write_cpuhp_target(struct device
*dev
,
1437 struct device_attribute
*attr
,
1438 const char *buf
, size_t count
)
1440 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, dev
->id
);
1441 struct cpuhp_step
*sp
;
1444 ret
= kstrtoint(buf
, 10, &target
);
1448 #ifdef CONFIG_CPU_HOTPLUG_STATE_CONTROL
1449 if (target
< CPUHP_OFFLINE
|| target
> CPUHP_ONLINE
)
1452 if (target
!= CPUHP_OFFLINE
&& target
!= CPUHP_ONLINE
)
1456 ret
= lock_device_hotplug_sysfs();
1460 mutex_lock(&cpuhp_state_mutex
);
1461 sp
= cpuhp_get_step(target
);
1462 ret
= !sp
->name
|| sp
->cant_stop
? -EINVAL
: 0;
1463 mutex_unlock(&cpuhp_state_mutex
);
1467 if (st
->state
< target
)
1468 ret
= do_cpu_up(dev
->id
, target
);
1470 ret
= do_cpu_down(dev
->id
, target
);
1472 unlock_device_hotplug();
1473 return ret
? ret
: count
;
1476 static ssize_t
show_cpuhp_target(struct device
*dev
,
1477 struct device_attribute
*attr
, char *buf
)
1479 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, dev
->id
);
1481 return sprintf(buf
, "%d\n", st
->target
);
1483 static DEVICE_ATTR(target
, 0644, show_cpuhp_target
, write_cpuhp_target
);
1485 static struct attribute
*cpuhp_cpu_attrs
[] = {
1486 &dev_attr_state
.attr
,
1487 &dev_attr_target
.attr
,
1491 static struct attribute_group cpuhp_cpu_attr_group
= {
1492 .attrs
= cpuhp_cpu_attrs
,
1497 static ssize_t
show_cpuhp_states(struct device
*dev
,
1498 struct device_attribute
*attr
, char *buf
)
1500 ssize_t cur
, res
= 0;
1503 mutex_lock(&cpuhp_state_mutex
);
1504 for (i
= CPUHP_OFFLINE
; i
<= CPUHP_ONLINE
; i
++) {
1505 struct cpuhp_step
*sp
= cpuhp_get_step(i
);
1508 cur
= sprintf(buf
, "%3d: %s\n", i
, sp
->name
);
1513 mutex_unlock(&cpuhp_state_mutex
);
1516 static DEVICE_ATTR(states
, 0444, show_cpuhp_states
, NULL
);
1518 static struct attribute
*cpuhp_cpu_root_attrs
[] = {
1519 &dev_attr_states
.attr
,
1523 static struct attribute_group cpuhp_cpu_root_attr_group
= {
1524 .attrs
= cpuhp_cpu_root_attrs
,
1529 static int __init
cpuhp_sysfs_init(void)
1533 ret
= sysfs_create_group(&cpu_subsys
.dev_root
->kobj
,
1534 &cpuhp_cpu_root_attr_group
);
1538 for_each_possible_cpu(cpu
) {
1539 struct device
*dev
= get_cpu_device(cpu
);
1543 ret
= sysfs_create_group(&dev
->kobj
, &cpuhp_cpu_attr_group
);
1549 device_initcall(cpuhp_sysfs_init
);
1553 * cpu_bit_bitmap[] is a special, "compressed" data structure that
1554 * represents all NR_CPUS bits binary values of 1<<nr.
1556 * It is used by cpumask_of() to get a constant address to a CPU
1557 * mask value that has a single bit set only.
1560 /* cpu_bit_bitmap[0] is empty - so we can back into it */
1561 #define MASK_DECLARE_1(x) [x+1][0] = (1UL << (x))
1562 #define MASK_DECLARE_2(x) MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
1563 #define MASK_DECLARE_4(x) MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
1564 #define MASK_DECLARE_8(x) MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
1566 const unsigned long cpu_bit_bitmap
[BITS_PER_LONG
+1][BITS_TO_LONGS(NR_CPUS
)] = {
1568 MASK_DECLARE_8(0), MASK_DECLARE_8(8),
1569 MASK_DECLARE_8(16), MASK_DECLARE_8(24),
1570 #if BITS_PER_LONG > 32
1571 MASK_DECLARE_8(32), MASK_DECLARE_8(40),
1572 MASK_DECLARE_8(48), MASK_DECLARE_8(56),
1575 EXPORT_SYMBOL_GPL(cpu_bit_bitmap
);
1577 const DECLARE_BITMAP(cpu_all_bits
, NR_CPUS
) = CPU_BITS_ALL
;
1578 EXPORT_SYMBOL(cpu_all_bits
);
1580 #ifdef CONFIG_INIT_ALL_POSSIBLE
1581 struct cpumask __cpu_possible_mask __read_mostly
1584 struct cpumask __cpu_possible_mask __read_mostly
;
1586 EXPORT_SYMBOL(__cpu_possible_mask
);
1588 struct cpumask __cpu_online_mask __read_mostly
;
1589 EXPORT_SYMBOL(__cpu_online_mask
);
1591 struct cpumask __cpu_present_mask __read_mostly
;
1592 EXPORT_SYMBOL(__cpu_present_mask
);
1594 struct cpumask __cpu_active_mask __read_mostly
;
1595 EXPORT_SYMBOL(__cpu_active_mask
);
1597 void init_cpu_present(const struct cpumask
*src
)
1599 cpumask_copy(&__cpu_present_mask
, src
);
1602 void init_cpu_possible(const struct cpumask
*src
)
1604 cpumask_copy(&__cpu_possible_mask
, src
);
1607 void init_cpu_online(const struct cpumask
*src
)
1609 cpumask_copy(&__cpu_online_mask
, src
);
1613 * Activate the first processor.
1615 void __init
boot_cpu_init(void)
1617 int cpu
= smp_processor_id();
1619 /* Mark the boot cpu "present", "online" etc for SMP and UP case */
1620 set_cpu_online(cpu
, true);
1621 set_cpu_active(cpu
, true);
1622 set_cpu_present(cpu
, true);
1623 set_cpu_possible(cpu
, true);
1627 * Must be called _AFTER_ setting up the per_cpu areas
1629 void __init
boot_cpu_state_init(void)
1631 per_cpu_ptr(&cpuhp_state
, smp_processor_id())->state
= CPUHP_ONLINE
;