2 * (C) 2001, 2002, 2003, 2004 Rusty Russell
4 * This code is licenced under the GPL.
6 #include <linux/sched/mm.h>
7 #include <linux/proc_fs.h>
9 #include <linux/init.h>
10 #include <linux/notifier.h>
11 #include <linux/sched/signal.h>
12 #include <linux/sched/hotplug.h>
13 #include <linux/sched/isolation.h>
14 #include <linux/sched/task.h>
15 #include <linux/sched/smt.h>
16 #include <linux/unistd.h>
17 #include <linux/cpu.h>
18 #include <linux/oom.h>
19 #include <linux/rcupdate.h>
20 #include <linux/export.h>
21 #include <linux/bug.h>
22 #include <linux/kthread.h>
23 #include <linux/stop_machine.h>
24 #include <linux/mutex.h>
25 #include <linux/gfp.h>
26 #include <linux/suspend.h>
27 #include <linux/lockdep.h>
28 #include <linux/tick.h>
29 #include <linux/irq.h>
30 #include <linux/nmi.h>
31 #include <linux/smpboot.h>
32 #include <linux/relay.h>
33 #include <linux/slab.h>
34 #include <linux/scs.h>
35 #include <linux/percpu-rwsem.h>
36 #include <linux/cpuset.h>
37 #include <linux/random.h>
39 #include <trace/events/power.h>
40 #define CREATE_TRACE_POINTS
41 #include <trace/events/cpuhp.h>
46 * struct cpuhp_cpu_state - Per cpu hotplug state storage
47 * @state: The current cpu state
48 * @target: The target state
49 * @fail: Current CPU hotplug callback state
50 * @thread: Pointer to the hotplug thread
51 * @should_run: Thread should execute
52 * @rollback: Perform a rollback
53 * @single: Single callback invocation
54 * @bringup: Single callback bringup or teardown selector
56 * @node: Remote CPU node; for multi-instance, do a
57 * single entry callback for install/remove
58 * @last: For multi-instance rollback, remember how far we got
59 * @cb_state: The state for a single callback (install/uninstall)
60 * @result: Result of the operation
61 * @done_up: Signal completion to the issuer of the task for cpu-up
62 * @done_down: Signal completion to the issuer of the task for cpu-down
64 struct cpuhp_cpu_state
{
65 enum cpuhp_state state
;
66 enum cpuhp_state target
;
67 enum cpuhp_state fail
;
69 struct task_struct
*thread
;
74 struct hlist_node
*node
;
75 struct hlist_node
*last
;
76 enum cpuhp_state cb_state
;
78 struct completion done_up
;
79 struct completion done_down
;
83 static DEFINE_PER_CPU(struct cpuhp_cpu_state
, cpuhp_state
) = {
84 .fail
= CPUHP_INVALID
,
88 cpumask_t cpus_booted_once_mask
;
91 #if defined(CONFIG_LOCKDEP) && defined(CONFIG_SMP)
92 static struct lockdep_map cpuhp_state_up_map
=
93 STATIC_LOCKDEP_MAP_INIT("cpuhp_state-up", &cpuhp_state_up_map
);
94 static struct lockdep_map cpuhp_state_down_map
=
95 STATIC_LOCKDEP_MAP_INIT("cpuhp_state-down", &cpuhp_state_down_map
);
98 static inline void cpuhp_lock_acquire(bool bringup
)
100 lock_map_acquire(bringup
? &cpuhp_state_up_map
: &cpuhp_state_down_map
);
103 static inline void cpuhp_lock_release(bool bringup
)
105 lock_map_release(bringup
? &cpuhp_state_up_map
: &cpuhp_state_down_map
);
109 static inline void cpuhp_lock_acquire(bool bringup
) { }
110 static inline void cpuhp_lock_release(bool bringup
) { }
115 * struct cpuhp_step - Hotplug state machine step
116 * @name: Name of the step
117 * @startup: Startup function of the step
118 * @teardown: Teardown function of the step
119 * @cant_stop: Bringup/teardown can't be stopped at this step
120 * @multi_instance: State has multiple instances which get added afterwards
125 int (*single
)(unsigned int cpu
);
126 int (*multi
)(unsigned int cpu
,
127 struct hlist_node
*node
);
130 int (*single
)(unsigned int cpu
);
131 int (*multi
)(unsigned int cpu
,
132 struct hlist_node
*node
);
135 struct hlist_head list
;
141 static DEFINE_MUTEX(cpuhp_state_mutex
);
142 static struct cpuhp_step cpuhp_hp_states
[];
144 static struct cpuhp_step
*cpuhp_get_step(enum cpuhp_state state
)
146 return cpuhp_hp_states
+ state
;
149 static bool cpuhp_step_empty(bool bringup
, struct cpuhp_step
*step
)
151 return bringup
? !step
->startup
.single
: !step
->teardown
.single
;
155 * cpuhp_invoke_callback - Invoke the callbacks for a given state
156 * @cpu: The cpu for which the callback should be invoked
157 * @state: The state to do callbacks for
158 * @bringup: True if the bringup callback should be invoked
159 * @node: For multi-instance, do a single entry callback for install/remove
160 * @lastp: For multi-instance rollback, remember how far we got
162 * Called from cpu hotplug and from the state register machinery.
164 * Return: %0 on success or a negative errno code
166 static int cpuhp_invoke_callback(unsigned int cpu
, enum cpuhp_state state
,
167 bool bringup
, struct hlist_node
*node
,
168 struct hlist_node
**lastp
)
170 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, cpu
);
171 struct cpuhp_step
*step
= cpuhp_get_step(state
);
172 int (*cbm
)(unsigned int cpu
, struct hlist_node
*node
);
173 int (*cb
)(unsigned int cpu
);
176 if (st
->fail
== state
) {
177 st
->fail
= CPUHP_INVALID
;
181 if (cpuhp_step_empty(bringup
, step
)) {
186 if (!step
->multi_instance
) {
187 WARN_ON_ONCE(lastp
&& *lastp
);
188 cb
= bringup
? step
->startup
.single
: step
->teardown
.single
;
190 trace_cpuhp_enter(cpu
, st
->target
, state
, cb
);
192 trace_cpuhp_exit(cpu
, st
->state
, state
, ret
);
195 cbm
= bringup
? step
->startup
.multi
: step
->teardown
.multi
;
197 /* Single invocation for instance add/remove */
199 WARN_ON_ONCE(lastp
&& *lastp
);
200 trace_cpuhp_multi_enter(cpu
, st
->target
, state
, cbm
, node
);
201 ret
= cbm(cpu
, node
);
202 trace_cpuhp_exit(cpu
, st
->state
, state
, ret
);
206 /* State transition. Invoke on all instances */
208 hlist_for_each(node
, &step
->list
) {
209 if (lastp
&& node
== *lastp
)
212 trace_cpuhp_multi_enter(cpu
, st
->target
, state
, cbm
, node
);
213 ret
= cbm(cpu
, node
);
214 trace_cpuhp_exit(cpu
, st
->state
, state
, ret
);
228 /* Rollback the instances if one failed */
229 cbm
= !bringup
? step
->startup
.multi
: step
->teardown
.multi
;
233 hlist_for_each(node
, &step
->list
) {
237 trace_cpuhp_multi_enter(cpu
, st
->target
, state
, cbm
, node
);
238 ret
= cbm(cpu
, node
);
239 trace_cpuhp_exit(cpu
, st
->state
, state
, ret
);
241 * Rollback must not fail,
249 static bool cpuhp_is_ap_state(enum cpuhp_state state
)
252 * The extra check for CPUHP_TEARDOWN_CPU is only for documentation
253 * purposes as that state is handled explicitly in cpu_down.
255 return state
> CPUHP_BRINGUP_CPU
&& state
!= CPUHP_TEARDOWN_CPU
;
258 static inline void wait_for_ap_thread(struct cpuhp_cpu_state
*st
, bool bringup
)
260 struct completion
*done
= bringup
? &st
->done_up
: &st
->done_down
;
261 wait_for_completion(done
);
264 static inline void complete_ap_thread(struct cpuhp_cpu_state
*st
, bool bringup
)
266 struct completion
*done
= bringup
? &st
->done_up
: &st
->done_down
;
271 * The former STARTING/DYING states, ran with IRQs disabled and must not fail.
273 static bool cpuhp_is_atomic_state(enum cpuhp_state state
)
275 return CPUHP_AP_IDLE_DEAD
<= state
&& state
< CPUHP_AP_ONLINE
;
278 /* Serializes the updates to cpu_online_mask, cpu_present_mask */
279 static DEFINE_MUTEX(cpu_add_remove_lock
);
280 bool cpuhp_tasks_frozen
;
281 EXPORT_SYMBOL_GPL(cpuhp_tasks_frozen
);
284 * The following two APIs (cpu_maps_update_begin/done) must be used when
285 * attempting to serialize the updates to cpu_online_mask & cpu_present_mask.
287 void cpu_maps_update_begin(void)
289 mutex_lock(&cpu_add_remove_lock
);
292 void cpu_maps_update_done(void)
294 mutex_unlock(&cpu_add_remove_lock
);
298 * If set, cpu_up and cpu_down will return -EBUSY and do nothing.
299 * Should always be manipulated under cpu_add_remove_lock
301 static int cpu_hotplug_disabled
;
303 #ifdef CONFIG_HOTPLUG_CPU
305 DEFINE_STATIC_PERCPU_RWSEM(cpu_hotplug_lock
);
307 void cpus_read_lock(void)
309 percpu_down_read(&cpu_hotplug_lock
);
311 EXPORT_SYMBOL_GPL(cpus_read_lock
);
313 int cpus_read_trylock(void)
315 return percpu_down_read_trylock(&cpu_hotplug_lock
);
317 EXPORT_SYMBOL_GPL(cpus_read_trylock
);
319 void cpus_read_unlock(void)
321 percpu_up_read(&cpu_hotplug_lock
);
323 EXPORT_SYMBOL_GPL(cpus_read_unlock
);
325 void cpus_write_lock(void)
327 percpu_down_write(&cpu_hotplug_lock
);
330 void cpus_write_unlock(void)
332 percpu_up_write(&cpu_hotplug_lock
);
335 void lockdep_assert_cpus_held(void)
338 * We can't have hotplug operations before userspace starts running,
339 * and some init codepaths will knowingly not take the hotplug lock.
340 * This is all valid, so mute lockdep until it makes sense to report
343 if (system_state
< SYSTEM_RUNNING
)
346 percpu_rwsem_assert_held(&cpu_hotplug_lock
);
349 #ifdef CONFIG_LOCKDEP
350 int lockdep_is_cpus_held(void)
352 return percpu_rwsem_is_held(&cpu_hotplug_lock
);
356 static void lockdep_acquire_cpus_lock(void)
358 rwsem_acquire(&cpu_hotplug_lock
.dep_map
, 0, 0, _THIS_IP_
);
361 static void lockdep_release_cpus_lock(void)
363 rwsem_release(&cpu_hotplug_lock
.dep_map
, _THIS_IP_
);
367 * Wait for currently running CPU hotplug operations to complete (if any) and
368 * disable future CPU hotplug (from sysfs). The 'cpu_add_remove_lock' protects
369 * the 'cpu_hotplug_disabled' flag. The same lock is also acquired by the
370 * hotplug path before performing hotplug operations. So acquiring that lock
371 * guarantees mutual exclusion from any currently running hotplug operations.
373 void cpu_hotplug_disable(void)
375 cpu_maps_update_begin();
376 cpu_hotplug_disabled
++;
377 cpu_maps_update_done();
379 EXPORT_SYMBOL_GPL(cpu_hotplug_disable
);
381 static void __cpu_hotplug_enable(void)
383 if (WARN_ONCE(!cpu_hotplug_disabled
, "Unbalanced cpu hotplug enable\n"))
385 cpu_hotplug_disabled
--;
388 void cpu_hotplug_enable(void)
390 cpu_maps_update_begin();
391 __cpu_hotplug_enable();
392 cpu_maps_update_done();
394 EXPORT_SYMBOL_GPL(cpu_hotplug_enable
);
398 static void lockdep_acquire_cpus_lock(void)
402 static void lockdep_release_cpus_lock(void)
406 #endif /* CONFIG_HOTPLUG_CPU */
409 * Architectures that need SMT-specific errata handling during SMT hotplug
410 * should override this.
412 void __weak
arch_smt_update(void) { }
414 #ifdef CONFIG_HOTPLUG_SMT
415 enum cpuhp_smt_control cpu_smt_control __read_mostly
= CPU_SMT_ENABLED
;
417 void __init
cpu_smt_disable(bool force
)
419 if (!cpu_smt_possible())
423 pr_info("SMT: Force disabled\n");
424 cpu_smt_control
= CPU_SMT_FORCE_DISABLED
;
426 pr_info("SMT: disabled\n");
427 cpu_smt_control
= CPU_SMT_DISABLED
;
432 * The decision whether SMT is supported can only be done after the full
433 * CPU identification. Called from architecture code.
435 void __init
cpu_smt_check_topology(void)
437 if (!topology_smt_supported())
438 cpu_smt_control
= CPU_SMT_NOT_SUPPORTED
;
441 static int __init
smt_cmdline_disable(char *str
)
443 cpu_smt_disable(str
&& !strcmp(str
, "force"));
446 early_param("nosmt", smt_cmdline_disable
);
448 static inline bool cpu_smt_allowed(unsigned int cpu
)
450 if (cpu_smt_control
== CPU_SMT_ENABLED
)
453 if (topology_is_primary_thread(cpu
))
457 * On x86 it's required to boot all logical CPUs at least once so
458 * that the init code can get a chance to set CR4.MCE on each
459 * CPU. Otherwise, a broadcasted MCE observing CR4.MCE=0b on any
460 * core will shutdown the machine.
462 return !cpumask_test_cpu(cpu
, &cpus_booted_once_mask
);
465 /* Returns true if SMT is not supported of forcefully (irreversibly) disabled */
466 bool cpu_smt_possible(void)
468 return cpu_smt_control
!= CPU_SMT_FORCE_DISABLED
&&
469 cpu_smt_control
!= CPU_SMT_NOT_SUPPORTED
;
471 EXPORT_SYMBOL_GPL(cpu_smt_possible
);
473 static inline bool cpu_smt_allowed(unsigned int cpu
) { return true; }
476 static inline enum cpuhp_state
477 cpuhp_set_state(int cpu
, struct cpuhp_cpu_state
*st
, enum cpuhp_state target
)
479 enum cpuhp_state prev_state
= st
->state
;
480 bool bringup
= st
->state
< target
;
482 st
->rollback
= false;
487 st
->bringup
= bringup
;
488 if (cpu_dying(cpu
) != !bringup
)
489 set_cpu_dying(cpu
, !bringup
);
495 cpuhp_reset_state(int cpu
, struct cpuhp_cpu_state
*st
,
496 enum cpuhp_state prev_state
)
498 bool bringup
= !st
->bringup
;
500 st
->target
= prev_state
;
503 * Already rolling back. No need invert the bringup value or to change
512 * If we have st->last we need to undo partial multi_instance of this
513 * state first. Otherwise start undo at the previous state.
522 st
->bringup
= bringup
;
523 if (cpu_dying(cpu
) != !bringup
)
524 set_cpu_dying(cpu
, !bringup
);
527 /* Regular hotplug invocation of the AP hotplug thread */
528 static void __cpuhp_kick_ap(struct cpuhp_cpu_state
*st
)
530 if (!st
->single
&& st
->state
== st
->target
)
535 * Make sure the above stores are visible before should_run becomes
536 * true. Paired with the mb() above in cpuhp_thread_fun()
539 st
->should_run
= true;
540 wake_up_process(st
->thread
);
541 wait_for_ap_thread(st
, st
->bringup
);
544 static int cpuhp_kick_ap(int cpu
, struct cpuhp_cpu_state
*st
,
545 enum cpuhp_state target
)
547 enum cpuhp_state prev_state
;
550 prev_state
= cpuhp_set_state(cpu
, st
, target
);
552 if ((ret
= st
->result
)) {
553 cpuhp_reset_state(cpu
, st
, prev_state
);
560 static int bringup_wait_for_ap(unsigned int cpu
)
562 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, cpu
);
564 /* Wait for the CPU to reach CPUHP_AP_ONLINE_IDLE */
565 wait_for_ap_thread(st
, true);
566 if (WARN_ON_ONCE((!cpu_online(cpu
))))
569 /* Unpark the hotplug thread of the target cpu */
570 kthread_unpark(st
->thread
);
573 * SMT soft disabling on X86 requires to bring the CPU out of the
574 * BIOS 'wait for SIPI' state in order to set the CR4.MCE bit. The
575 * CPU marked itself as booted_once in notify_cpu_starting() so the
576 * cpu_smt_allowed() check will now return false if this is not the
579 if (!cpu_smt_allowed(cpu
))
582 if (st
->target
<= CPUHP_AP_ONLINE_IDLE
)
585 return cpuhp_kick_ap(cpu
, st
, st
->target
);
588 static int bringup_cpu(unsigned int cpu
)
590 struct task_struct
*idle
= idle_thread_get(cpu
);
594 * Reset stale stack state from the last time this CPU was online.
596 scs_task_reset(idle
);
597 kasan_unpoison_task_stack(idle
);
600 * Some architectures have to walk the irq descriptors to
601 * setup the vector space for the cpu which comes online.
602 * Prevent irq alloc/free across the bringup.
606 /* Arch-specific enabling code. */
607 ret
= __cpu_up(cpu
, idle
);
611 return bringup_wait_for_ap(cpu
);
614 static int finish_cpu(unsigned int cpu
)
616 struct task_struct
*idle
= idle_thread_get(cpu
);
617 struct mm_struct
*mm
= idle
->active_mm
;
620 * idle_task_exit() will have switched to &init_mm, now
621 * clean up any remaining active_mm state.
624 idle
->active_mm
= &init_mm
;
630 * Hotplug state machine related functions
634 * Get the next state to run. Empty ones will be skipped. Returns true if a
637 * st->state will be modified ahead of time, to match state_to_run, as if it
640 static bool cpuhp_next_state(bool bringup
,
641 enum cpuhp_state
*state_to_run
,
642 struct cpuhp_cpu_state
*st
,
643 enum cpuhp_state target
)
647 if (st
->state
>= target
)
650 *state_to_run
= ++st
->state
;
652 if (st
->state
<= target
)
655 *state_to_run
= st
->state
--;
658 if (!cpuhp_step_empty(bringup
, cpuhp_get_step(*state_to_run
)))
665 static int cpuhp_invoke_callback_range(bool bringup
,
667 struct cpuhp_cpu_state
*st
,
668 enum cpuhp_state target
)
670 enum cpuhp_state state
;
673 while (cpuhp_next_state(bringup
, &state
, st
, target
)) {
674 err
= cpuhp_invoke_callback(cpu
, state
, bringup
, NULL
, NULL
);
682 static inline bool can_rollback_cpu(struct cpuhp_cpu_state
*st
)
684 if (IS_ENABLED(CONFIG_HOTPLUG_CPU
))
687 * When CPU hotplug is disabled, then taking the CPU down is not
688 * possible because takedown_cpu() and the architecture and
689 * subsystem specific mechanisms are not available. So the CPU
690 * which would be completely unplugged again needs to stay around
691 * in the current state.
693 return st
->state
<= CPUHP_BRINGUP_CPU
;
696 static int cpuhp_up_callbacks(unsigned int cpu
, struct cpuhp_cpu_state
*st
,
697 enum cpuhp_state target
)
699 enum cpuhp_state prev_state
= st
->state
;
702 ret
= cpuhp_invoke_callback_range(true, cpu
, st
, target
);
704 pr_debug("CPU UP failed (%d) CPU %u state %s (%d)\n",
705 ret
, cpu
, cpuhp_get_step(st
->state
)->name
,
708 cpuhp_reset_state(cpu
, st
, prev_state
);
709 if (can_rollback_cpu(st
))
710 WARN_ON(cpuhp_invoke_callback_range(false, cpu
, st
,
717 * The cpu hotplug threads manage the bringup and teardown of the cpus
719 static void cpuhp_create(unsigned int cpu
)
721 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, cpu
);
723 init_completion(&st
->done_up
);
724 init_completion(&st
->done_down
);
727 static int cpuhp_should_run(unsigned int cpu
)
729 struct cpuhp_cpu_state
*st
= this_cpu_ptr(&cpuhp_state
);
731 return st
->should_run
;
735 * Execute teardown/startup callbacks on the plugged cpu. Also used to invoke
736 * callbacks when a state gets [un]installed at runtime.
738 * Each invocation of this function by the smpboot thread does a single AP
741 * It has 3 modes of operation:
742 * - single: runs st->cb_state
743 * - up: runs ++st->state, while st->state < st->target
744 * - down: runs st->state--, while st->state > st->target
746 * When complete or on error, should_run is cleared and the completion is fired.
748 static void cpuhp_thread_fun(unsigned int cpu
)
750 struct cpuhp_cpu_state
*st
= this_cpu_ptr(&cpuhp_state
);
751 bool bringup
= st
->bringup
;
752 enum cpuhp_state state
;
754 if (WARN_ON_ONCE(!st
->should_run
))
758 * ACQUIRE for the cpuhp_should_run() load of ->should_run. Ensures
759 * that if we see ->should_run we also see the rest of the state.
764 * The BP holds the hotplug lock, but we're now running on the AP,
765 * ensure that anybody asserting the lock is held, will actually find
768 lockdep_acquire_cpus_lock();
769 cpuhp_lock_acquire(bringup
);
772 state
= st
->cb_state
;
773 st
->should_run
= false;
775 st
->should_run
= cpuhp_next_state(bringup
, &state
, st
, st
->target
);
780 WARN_ON_ONCE(!cpuhp_is_ap_state(state
));
782 if (cpuhp_is_atomic_state(state
)) {
784 st
->result
= cpuhp_invoke_callback(cpu
, state
, bringup
, st
->node
, &st
->last
);
788 * STARTING/DYING must not fail!
790 WARN_ON_ONCE(st
->result
);
792 st
->result
= cpuhp_invoke_callback(cpu
, state
, bringup
, st
->node
, &st
->last
);
797 * If we fail on a rollback, we're up a creek without no
798 * paddle, no way forward, no way back. We loose, thanks for
801 WARN_ON_ONCE(st
->rollback
);
802 st
->should_run
= false;
806 cpuhp_lock_release(bringup
);
807 lockdep_release_cpus_lock();
810 complete_ap_thread(st
, bringup
);
813 /* Invoke a single callback on a remote cpu */
815 cpuhp_invoke_ap_callback(int cpu
, enum cpuhp_state state
, bool bringup
,
816 struct hlist_node
*node
)
818 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, cpu
);
821 if (!cpu_online(cpu
))
824 cpuhp_lock_acquire(false);
825 cpuhp_lock_release(false);
827 cpuhp_lock_acquire(true);
828 cpuhp_lock_release(true);
831 * If we are up and running, use the hotplug thread. For early calls
832 * we invoke the thread function directly.
835 return cpuhp_invoke_callback(cpu
, state
, bringup
, node
, NULL
);
837 st
->rollback
= false;
841 st
->bringup
= bringup
;
842 st
->cb_state
= state
;
848 * If we failed and did a partial, do a rollback.
850 if ((ret
= st
->result
) && st
->last
) {
852 st
->bringup
= !bringup
;
858 * Clean up the leftovers so the next hotplug operation wont use stale
861 st
->node
= st
->last
= NULL
;
865 static int cpuhp_kick_ap_work(unsigned int cpu
)
867 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, cpu
);
868 enum cpuhp_state prev_state
= st
->state
;
871 cpuhp_lock_acquire(false);
872 cpuhp_lock_release(false);
874 cpuhp_lock_acquire(true);
875 cpuhp_lock_release(true);
877 trace_cpuhp_enter(cpu
, st
->target
, prev_state
, cpuhp_kick_ap_work
);
878 ret
= cpuhp_kick_ap(cpu
, st
, st
->target
);
879 trace_cpuhp_exit(cpu
, st
->state
, prev_state
, ret
);
884 static struct smp_hotplug_thread cpuhp_threads
= {
885 .store
= &cpuhp_state
.thread
,
886 .create
= &cpuhp_create
,
887 .thread_should_run
= cpuhp_should_run
,
888 .thread_fn
= cpuhp_thread_fun
,
889 .thread_comm
= "cpuhp/%u",
893 void __init
cpuhp_threads_init(void)
895 BUG_ON(smpboot_register_percpu_thread(&cpuhp_threads
));
896 kthread_unpark(this_cpu_read(cpuhp_state
.thread
));
901 * Serialize hotplug trainwrecks outside of the cpu_hotplug_lock
904 * The operation is still serialized against concurrent CPU hotplug via
905 * cpu_add_remove_lock, i.e. CPU map protection. But it is _not_
906 * serialized against other hotplug related activity like adding or
907 * removing of state callbacks and state instances, which invoke either the
908 * startup or the teardown callback of the affected state.
910 * This is required for subsystems which are unfixable vs. CPU hotplug and
911 * evade lock inversion problems by scheduling work which has to be
912 * completed _before_ cpu_up()/_cpu_down() returns.
914 * Don't even think about adding anything to this for any new code or even
915 * drivers. It's only purpose is to keep existing lock order trainwrecks
918 * For cpu_down() there might be valid reasons to finish cleanups which are
919 * not required to be done under cpu_hotplug_lock, but that's a different
920 * story and would be not invoked via this.
922 static void cpu_up_down_serialize_trainwrecks(bool tasks_frozen
)
925 * cpusets delegate hotplug operations to a worker to "solve" the
926 * lock order problems. Wait for the worker, but only if tasks are
927 * _not_ frozen (suspend, hibernate) as that would wait forever.
929 * The wait is required because otherwise the hotplug operation
930 * returns with inconsistent state, which could even be observed in
931 * user space when a new CPU is brought up. The CPU plug uevent
932 * would be delivered and user space reacting on it would fail to
933 * move tasks to the newly plugged CPU up to the point where the
934 * work has finished because up to that point the newly plugged CPU
935 * is not assignable in cpusets/cgroups. On unplug that's not
936 * necessarily a visible issue, but it is still inconsistent state,
937 * which is the real problem which needs to be "fixed". This can't
938 * prevent the transient state between scheduling the work and
939 * returning from waiting for it.
942 cpuset_wait_for_hotplug();
945 #ifdef CONFIG_HOTPLUG_CPU
946 #ifndef arch_clear_mm_cpumask_cpu
947 #define arch_clear_mm_cpumask_cpu(cpu, mm) cpumask_clear_cpu(cpu, mm_cpumask(mm))
951 * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
954 * This function walks all processes, finds a valid mm struct for each one and
955 * then clears a corresponding bit in mm's cpumask. While this all sounds
956 * trivial, there are various non-obvious corner cases, which this function
957 * tries to solve in a safe manner.
959 * Also note that the function uses a somewhat relaxed locking scheme, so it may
960 * be called only for an already offlined CPU.
962 void clear_tasks_mm_cpumask(int cpu
)
964 struct task_struct
*p
;
967 * This function is called after the cpu is taken down and marked
968 * offline, so its not like new tasks will ever get this cpu set in
969 * their mm mask. -- Peter Zijlstra
970 * Thus, we may use rcu_read_lock() here, instead of grabbing
971 * full-fledged tasklist_lock.
973 WARN_ON(cpu_online(cpu
));
975 for_each_process(p
) {
976 struct task_struct
*t
;
979 * Main thread might exit, but other threads may still have
980 * a valid mm. Find one.
982 t
= find_lock_task_mm(p
);
985 arch_clear_mm_cpumask_cpu(cpu
, t
->mm
);
991 /* Take this CPU down. */
992 static int take_cpu_down(void *_param
)
994 struct cpuhp_cpu_state
*st
= this_cpu_ptr(&cpuhp_state
);
995 enum cpuhp_state target
= max((int)st
->target
, CPUHP_AP_OFFLINE
);
996 int err
, cpu
= smp_processor_id();
999 /* Ensure this CPU doesn't handle any more interrupts. */
1000 err
= __cpu_disable();
1005 * Must be called from CPUHP_TEARDOWN_CPU, which means, as we are going
1006 * down, that the current state is CPUHP_TEARDOWN_CPU - 1.
1008 WARN_ON(st
->state
!= (CPUHP_TEARDOWN_CPU
- 1));
1010 /* Invoke the former CPU_DYING callbacks */
1011 ret
= cpuhp_invoke_callback_range(false, cpu
, st
, target
);
1014 * DYING must not fail!
1018 /* Give up timekeeping duties */
1019 tick_handover_do_timer();
1020 /* Remove CPU from timer broadcasting */
1021 tick_offline_cpu(cpu
);
1022 /* Park the stopper thread */
1023 stop_machine_park(cpu
);
1027 static int takedown_cpu(unsigned int cpu
)
1029 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, cpu
);
1032 /* Park the smpboot threads */
1033 kthread_park(st
->thread
);
1036 * Prevent irq alloc/free while the dying cpu reorganizes the
1037 * interrupt affinities.
1042 * So now all preempt/rcu users must observe !cpu_active().
1044 err
= stop_machine_cpuslocked(take_cpu_down
, NULL
, cpumask_of(cpu
));
1046 /* CPU refused to die */
1047 irq_unlock_sparse();
1048 /* Unpark the hotplug thread so we can rollback there */
1049 kthread_unpark(st
->thread
);
1052 BUG_ON(cpu_online(cpu
));
1055 * The teardown callback for CPUHP_AP_SCHED_STARTING will have removed
1056 * all runnable tasks from the CPU, there's only the idle task left now
1057 * that the migration thread is done doing the stop_machine thing.
1059 * Wait for the stop thread to go away.
1061 wait_for_ap_thread(st
, false);
1062 BUG_ON(st
->state
!= CPUHP_AP_IDLE_DEAD
);
1064 /* Interrupts are moved away from the dying cpu, reenable alloc/free */
1065 irq_unlock_sparse();
1067 hotplug_cpu__broadcast_tick_pull(cpu
);
1068 /* This actually kills the CPU. */
1071 tick_cleanup_dead_cpu(cpu
);
1072 rcutree_migrate_callbacks(cpu
);
1076 static void cpuhp_complete_idle_dead(void *arg
)
1078 struct cpuhp_cpu_state
*st
= arg
;
1080 complete_ap_thread(st
, false);
1083 void cpuhp_report_idle_dead(void)
1085 struct cpuhp_cpu_state
*st
= this_cpu_ptr(&cpuhp_state
);
1087 BUG_ON(st
->state
!= CPUHP_AP_OFFLINE
);
1088 rcu_report_dead(smp_processor_id());
1089 st
->state
= CPUHP_AP_IDLE_DEAD
;
1091 * We cannot call complete after rcu_report_dead() so we delegate it
1094 smp_call_function_single(cpumask_first(cpu_online_mask
),
1095 cpuhp_complete_idle_dead
, st
, 0);
1098 static int cpuhp_down_callbacks(unsigned int cpu
, struct cpuhp_cpu_state
*st
,
1099 enum cpuhp_state target
)
1101 enum cpuhp_state prev_state
= st
->state
;
1104 ret
= cpuhp_invoke_callback_range(false, cpu
, st
, target
);
1106 pr_debug("CPU DOWN failed (%d) CPU %u state %s (%d)\n",
1107 ret
, cpu
, cpuhp_get_step(st
->state
)->name
,
1110 cpuhp_reset_state(cpu
, st
, prev_state
);
1112 if (st
->state
< prev_state
)
1113 WARN_ON(cpuhp_invoke_callback_range(true, cpu
, st
,
1120 /* Requires cpu_add_remove_lock to be held */
1121 static int __ref
_cpu_down(unsigned int cpu
, int tasks_frozen
,
1122 enum cpuhp_state target
)
1124 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, cpu
);
1125 int prev_state
, ret
= 0;
1127 if (num_online_cpus() == 1)
1130 if (!cpu_present(cpu
))
1135 cpuhp_tasks_frozen
= tasks_frozen
;
1137 prev_state
= cpuhp_set_state(cpu
, st
, target
);
1139 * If the current CPU state is in the range of the AP hotplug thread,
1140 * then we need to kick the thread.
1142 if (st
->state
> CPUHP_TEARDOWN_CPU
) {
1143 st
->target
= max((int)target
, CPUHP_TEARDOWN_CPU
);
1144 ret
= cpuhp_kick_ap_work(cpu
);
1146 * The AP side has done the error rollback already. Just
1147 * return the error code..
1153 * We might have stopped still in the range of the AP hotplug
1154 * thread. Nothing to do anymore.
1156 if (st
->state
> CPUHP_TEARDOWN_CPU
)
1159 st
->target
= target
;
1162 * The AP brought itself down to CPUHP_TEARDOWN_CPU. So we need
1163 * to do the further cleanups.
1165 ret
= cpuhp_down_callbacks(cpu
, st
, target
);
1166 if (ret
&& st
->state
< prev_state
) {
1167 if (st
->state
== CPUHP_TEARDOWN_CPU
) {
1168 cpuhp_reset_state(cpu
, st
, prev_state
);
1169 __cpuhp_kick_ap(st
);
1171 WARN(1, "DEAD callback error for CPU%d", cpu
);
1176 cpus_write_unlock();
1178 * Do post unplug cleanup. This is still protected against
1179 * concurrent CPU hotplug via cpu_add_remove_lock.
1181 lockup_detector_cleanup();
1183 cpu_up_down_serialize_trainwrecks(tasks_frozen
);
1187 static int cpu_down_maps_locked(unsigned int cpu
, enum cpuhp_state target
)
1189 if (cpu_hotplug_disabled
)
1191 return _cpu_down(cpu
, 0, target
);
1194 static int cpu_down(unsigned int cpu
, enum cpuhp_state target
)
1198 cpu_maps_update_begin();
1199 err
= cpu_down_maps_locked(cpu
, target
);
1200 cpu_maps_update_done();
1205 * cpu_device_down - Bring down a cpu device
1206 * @dev: Pointer to the cpu device to offline
1208 * This function is meant to be used by device core cpu subsystem only.
1210 * Other subsystems should use remove_cpu() instead.
1212 * Return: %0 on success or a negative errno code
1214 int cpu_device_down(struct device
*dev
)
1216 return cpu_down(dev
->id
, CPUHP_OFFLINE
);
1219 int remove_cpu(unsigned int cpu
)
1223 lock_device_hotplug();
1224 ret
= device_offline(get_cpu_device(cpu
));
1225 unlock_device_hotplug();
1229 EXPORT_SYMBOL_GPL(remove_cpu
);
1231 void smp_shutdown_nonboot_cpus(unsigned int primary_cpu
)
1236 cpu_maps_update_begin();
1239 * Make certain the cpu I'm about to reboot on is online.
1241 * This is inline to what migrate_to_reboot_cpu() already do.
1243 if (!cpu_online(primary_cpu
))
1244 primary_cpu
= cpumask_first(cpu_online_mask
);
1246 for_each_online_cpu(cpu
) {
1247 if (cpu
== primary_cpu
)
1250 error
= cpu_down_maps_locked(cpu
, CPUHP_OFFLINE
);
1252 pr_err("Failed to offline CPU%d - error=%d",
1259 * Ensure all but the reboot CPU are offline.
1261 BUG_ON(num_online_cpus() > 1);
1264 * Make sure the CPUs won't be enabled by someone else after this
1265 * point. Kexec will reboot to a new kernel shortly resetting
1266 * everything along the way.
1268 cpu_hotplug_disabled
++;
1270 cpu_maps_update_done();
1274 #define takedown_cpu NULL
1275 #endif /*CONFIG_HOTPLUG_CPU*/
1278 * notify_cpu_starting(cpu) - Invoke the callbacks on the starting CPU
1279 * @cpu: cpu that just started
1281 * It must be called by the arch code on the new cpu, before the new cpu
1282 * enables interrupts and before the "boot" cpu returns from __cpu_up().
1284 void notify_cpu_starting(unsigned int cpu
)
1286 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, cpu
);
1287 enum cpuhp_state target
= min((int)st
->target
, CPUHP_AP_ONLINE
);
1290 rcu_cpu_starting(cpu
); /* Enables RCU usage on this CPU. */
1291 cpumask_set_cpu(cpu
, &cpus_booted_once_mask
);
1292 ret
= cpuhp_invoke_callback_range(true, cpu
, st
, target
);
1295 * STARTING must not fail!
1301 * Called from the idle task. Wake up the controlling task which brings the
1302 * hotplug thread of the upcoming CPU up and then delegates the rest of the
1303 * online bringup to the hotplug thread.
1305 void cpuhp_online_idle(enum cpuhp_state state
)
1307 struct cpuhp_cpu_state
*st
= this_cpu_ptr(&cpuhp_state
);
1309 /* Happens for the boot cpu */
1310 if (state
!= CPUHP_AP_ONLINE_IDLE
)
1314 * Unpart the stopper thread before we start the idle loop (and start
1315 * scheduling); this ensures the stopper task is always available.
1317 stop_machine_unpark(smp_processor_id());
1319 st
->state
= CPUHP_AP_ONLINE_IDLE
;
1320 complete_ap_thread(st
, true);
1323 /* Requires cpu_add_remove_lock to be held */
1324 static int _cpu_up(unsigned int cpu
, int tasks_frozen
, enum cpuhp_state target
)
1326 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, cpu
);
1327 struct task_struct
*idle
;
1332 if (!cpu_present(cpu
)) {
1338 * The caller of cpu_up() might have raced with another
1339 * caller. Nothing to do.
1341 if (st
->state
>= target
)
1344 if (st
->state
== CPUHP_OFFLINE
) {
1345 /* Let it fail before we try to bring the cpu up */
1346 idle
= idle_thread_get(cpu
);
1348 ret
= PTR_ERR(idle
);
1353 cpuhp_tasks_frozen
= tasks_frozen
;
1355 cpuhp_set_state(cpu
, st
, target
);
1357 * If the current CPU state is in the range of the AP hotplug thread,
1358 * then we need to kick the thread once more.
1360 if (st
->state
> CPUHP_BRINGUP_CPU
) {
1361 ret
= cpuhp_kick_ap_work(cpu
);
1363 * The AP side has done the error rollback already. Just
1364 * return the error code..
1371 * Try to reach the target state. We max out on the BP at
1372 * CPUHP_BRINGUP_CPU. After that the AP hotplug thread is
1373 * responsible for bringing it up to the target state.
1375 target
= min((int)target
, CPUHP_BRINGUP_CPU
);
1376 ret
= cpuhp_up_callbacks(cpu
, st
, target
);
1378 cpus_write_unlock();
1380 cpu_up_down_serialize_trainwrecks(tasks_frozen
);
1384 static int cpu_up(unsigned int cpu
, enum cpuhp_state target
)
1388 if (!cpu_possible(cpu
)) {
1389 pr_err("can't online cpu %d because it is not configured as may-hotadd at boot time\n",
1391 #if defined(CONFIG_IA64)
1392 pr_err("please check additional_cpus= boot parameter\n");
1397 err
= try_online_node(cpu_to_node(cpu
));
1401 cpu_maps_update_begin();
1403 if (cpu_hotplug_disabled
) {
1407 if (!cpu_smt_allowed(cpu
)) {
1412 err
= _cpu_up(cpu
, 0, target
);
1414 cpu_maps_update_done();
1419 * cpu_device_up - Bring up a cpu device
1420 * @dev: Pointer to the cpu device to online
1422 * This function is meant to be used by device core cpu subsystem only.
1424 * Other subsystems should use add_cpu() instead.
1426 * Return: %0 on success or a negative errno code
1428 int cpu_device_up(struct device
*dev
)
1430 return cpu_up(dev
->id
, CPUHP_ONLINE
);
1433 int add_cpu(unsigned int cpu
)
1437 lock_device_hotplug();
1438 ret
= device_online(get_cpu_device(cpu
));
1439 unlock_device_hotplug();
1443 EXPORT_SYMBOL_GPL(add_cpu
);
1446 * bringup_hibernate_cpu - Bring up the CPU that we hibernated on
1447 * @sleep_cpu: The cpu we hibernated on and should be brought up.
1449 * On some architectures like arm64, we can hibernate on any CPU, but on
1450 * wake up the CPU we hibernated on might be offline as a side effect of
1451 * using maxcpus= for example.
1453 * Return: %0 on success or a negative errno code
1455 int bringup_hibernate_cpu(unsigned int sleep_cpu
)
1459 if (!cpu_online(sleep_cpu
)) {
1460 pr_info("Hibernated on a CPU that is offline! Bringing CPU up.\n");
1461 ret
= cpu_up(sleep_cpu
, CPUHP_ONLINE
);
1463 pr_err("Failed to bring hibernate-CPU up!\n");
1470 void bringup_nonboot_cpus(unsigned int setup_max_cpus
)
1474 for_each_present_cpu(cpu
) {
1475 if (num_online_cpus() >= setup_max_cpus
)
1477 if (!cpu_online(cpu
))
1478 cpu_up(cpu
, CPUHP_ONLINE
);
1482 #ifdef CONFIG_PM_SLEEP_SMP
1483 static cpumask_var_t frozen_cpus
;
1485 int freeze_secondary_cpus(int primary
)
1489 cpu_maps_update_begin();
1490 if (primary
== -1) {
1491 primary
= cpumask_first(cpu_online_mask
);
1492 if (!housekeeping_cpu(primary
, HK_FLAG_TIMER
))
1493 primary
= housekeeping_any_cpu(HK_FLAG_TIMER
);
1495 if (!cpu_online(primary
))
1496 primary
= cpumask_first(cpu_online_mask
);
1500 * We take down all of the non-boot CPUs in one shot to avoid races
1501 * with the userspace trying to use the CPU hotplug at the same time
1503 cpumask_clear(frozen_cpus
);
1505 pr_info("Disabling non-boot CPUs ...\n");
1506 for_each_online_cpu(cpu
) {
1510 if (pm_wakeup_pending()) {
1511 pr_info("Wakeup pending. Abort CPU freeze\n");
1516 trace_suspend_resume(TPS("CPU_OFF"), cpu
, true);
1517 error
= _cpu_down(cpu
, 1, CPUHP_OFFLINE
);
1518 trace_suspend_resume(TPS("CPU_OFF"), cpu
, false);
1520 cpumask_set_cpu(cpu
, frozen_cpus
);
1522 pr_err("Error taking CPU%d down: %d\n", cpu
, error
);
1528 BUG_ON(num_online_cpus() > 1);
1530 pr_err("Non-boot CPUs are not disabled\n");
1533 * Make sure the CPUs won't be enabled by someone else. We need to do
1534 * this even in case of failure as all freeze_secondary_cpus() users are
1535 * supposed to do thaw_secondary_cpus() on the failure path.
1537 cpu_hotplug_disabled
++;
1539 cpu_maps_update_done();
1543 void __weak
arch_thaw_secondary_cpus_begin(void)
1547 void __weak
arch_thaw_secondary_cpus_end(void)
1551 void thaw_secondary_cpus(void)
1555 /* Allow everyone to use the CPU hotplug again */
1556 cpu_maps_update_begin();
1557 __cpu_hotplug_enable();
1558 if (cpumask_empty(frozen_cpus
))
1561 pr_info("Enabling non-boot CPUs ...\n");
1563 arch_thaw_secondary_cpus_begin();
1565 for_each_cpu(cpu
, frozen_cpus
) {
1566 trace_suspend_resume(TPS("CPU_ON"), cpu
, true);
1567 error
= _cpu_up(cpu
, 1, CPUHP_ONLINE
);
1568 trace_suspend_resume(TPS("CPU_ON"), cpu
, false);
1570 pr_info("CPU%d is up\n", cpu
);
1573 pr_warn("Error taking CPU%d up: %d\n", cpu
, error
);
1576 arch_thaw_secondary_cpus_end();
1578 cpumask_clear(frozen_cpus
);
1580 cpu_maps_update_done();
1583 static int __init
alloc_frozen_cpus(void)
1585 if (!alloc_cpumask_var(&frozen_cpus
, GFP_KERNEL
|__GFP_ZERO
))
1589 core_initcall(alloc_frozen_cpus
);
1592 * When callbacks for CPU hotplug notifications are being executed, we must
1593 * ensure that the state of the system with respect to the tasks being frozen
1594 * or not, as reported by the notification, remains unchanged *throughout the
1595 * duration* of the execution of the callbacks.
1596 * Hence we need to prevent the freezer from racing with regular CPU hotplug.
1598 * This synchronization is implemented by mutually excluding regular CPU
1599 * hotplug and Suspend/Hibernate call paths by hooking onto the Suspend/
1600 * Hibernate notifications.
1603 cpu_hotplug_pm_callback(struct notifier_block
*nb
,
1604 unsigned long action
, void *ptr
)
1608 case PM_SUSPEND_PREPARE
:
1609 case PM_HIBERNATION_PREPARE
:
1610 cpu_hotplug_disable();
1613 case PM_POST_SUSPEND
:
1614 case PM_POST_HIBERNATION
:
1615 cpu_hotplug_enable();
1626 static int __init
cpu_hotplug_pm_sync_init(void)
1629 * cpu_hotplug_pm_callback has higher priority than x86
1630 * bsp_pm_callback which depends on cpu_hotplug_pm_callback
1631 * to disable cpu hotplug to avoid cpu hotplug race.
1633 pm_notifier(cpu_hotplug_pm_callback
, 0);
1636 core_initcall(cpu_hotplug_pm_sync_init
);
1638 #endif /* CONFIG_PM_SLEEP_SMP */
1642 #endif /* CONFIG_SMP */
1644 /* Boot processor state steps */
1645 static struct cpuhp_step cpuhp_hp_states
[] = {
1648 .startup
.single
= NULL
,
1649 .teardown
.single
= NULL
,
1652 [CPUHP_CREATE_THREADS
]= {
1653 .name
= "threads:prepare",
1654 .startup
.single
= smpboot_create_threads
,
1655 .teardown
.single
= NULL
,
1658 [CPUHP_PERF_PREPARE
] = {
1659 .name
= "perf:prepare",
1660 .startup
.single
= perf_event_init_cpu
,
1661 .teardown
.single
= perf_event_exit_cpu
,
1663 [CPUHP_RANDOM_PREPARE
] = {
1664 .name
= "random:prepare",
1665 .startup
.single
= random_prepare_cpu
,
1666 .teardown
.single
= NULL
,
1668 [CPUHP_WORKQUEUE_PREP
] = {
1669 .name
= "workqueue:prepare",
1670 .startup
.single
= workqueue_prepare_cpu
,
1671 .teardown
.single
= NULL
,
1673 [CPUHP_HRTIMERS_PREPARE
] = {
1674 .name
= "hrtimers:prepare",
1675 .startup
.single
= hrtimers_prepare_cpu
,
1676 .teardown
.single
= hrtimers_dead_cpu
,
1678 [CPUHP_SMPCFD_PREPARE
] = {
1679 .name
= "smpcfd:prepare",
1680 .startup
.single
= smpcfd_prepare_cpu
,
1681 .teardown
.single
= smpcfd_dead_cpu
,
1683 [CPUHP_RELAY_PREPARE
] = {
1684 .name
= "relay:prepare",
1685 .startup
.single
= relay_prepare_cpu
,
1686 .teardown
.single
= NULL
,
1688 [CPUHP_SLAB_PREPARE
] = {
1689 .name
= "slab:prepare",
1690 .startup
.single
= slab_prepare_cpu
,
1691 .teardown
.single
= slab_dead_cpu
,
1693 [CPUHP_RCUTREE_PREP
] = {
1694 .name
= "RCU/tree:prepare",
1695 .startup
.single
= rcutree_prepare_cpu
,
1696 .teardown
.single
= rcutree_dead_cpu
,
1699 * On the tear-down path, timers_dead_cpu() must be invoked
1700 * before blk_mq_queue_reinit_notify() from notify_dead(),
1701 * otherwise a RCU stall occurs.
1703 [CPUHP_TIMERS_PREPARE
] = {
1704 .name
= "timers:prepare",
1705 .startup
.single
= timers_prepare_cpu
,
1706 .teardown
.single
= timers_dead_cpu
,
1708 /* Kicks the plugged cpu into life */
1709 [CPUHP_BRINGUP_CPU
] = {
1710 .name
= "cpu:bringup",
1711 .startup
.single
= bringup_cpu
,
1712 .teardown
.single
= finish_cpu
,
1715 /* Final state before CPU kills itself */
1716 [CPUHP_AP_IDLE_DEAD
] = {
1717 .name
= "idle:dead",
1720 * Last state before CPU enters the idle loop to die. Transient state
1721 * for synchronization.
1723 [CPUHP_AP_OFFLINE
] = {
1724 .name
= "ap:offline",
1727 /* First state is scheduler control. Interrupts are disabled */
1728 [CPUHP_AP_SCHED_STARTING
] = {
1729 .name
= "sched:starting",
1730 .startup
.single
= sched_cpu_starting
,
1731 .teardown
.single
= sched_cpu_dying
,
1733 [CPUHP_AP_RCUTREE_DYING
] = {
1734 .name
= "RCU/tree:dying",
1735 .startup
.single
= NULL
,
1736 .teardown
.single
= rcutree_dying_cpu
,
1738 [CPUHP_AP_SMPCFD_DYING
] = {
1739 .name
= "smpcfd:dying",
1740 .startup
.single
= NULL
,
1741 .teardown
.single
= smpcfd_dying_cpu
,
1743 /* Entry state on starting. Interrupts enabled from here on. Transient
1744 * state for synchronsization */
1745 [CPUHP_AP_ONLINE
] = {
1746 .name
= "ap:online",
1749 * Handled on control processor until the plugged processor manages
1752 [CPUHP_TEARDOWN_CPU
] = {
1753 .name
= "cpu:teardown",
1754 .startup
.single
= NULL
,
1755 .teardown
.single
= takedown_cpu
,
1759 [CPUHP_AP_SCHED_WAIT_EMPTY
] = {
1760 .name
= "sched:waitempty",
1761 .startup
.single
= NULL
,
1762 .teardown
.single
= sched_cpu_wait_empty
,
1765 /* Handle smpboot threads park/unpark */
1766 [CPUHP_AP_SMPBOOT_THREADS
] = {
1767 .name
= "smpboot/threads:online",
1768 .startup
.single
= smpboot_unpark_threads
,
1769 .teardown
.single
= smpboot_park_threads
,
1771 [CPUHP_AP_IRQ_AFFINITY_ONLINE
] = {
1772 .name
= "irq/affinity:online",
1773 .startup
.single
= irq_affinity_online_cpu
,
1774 .teardown
.single
= NULL
,
1776 [CPUHP_AP_PERF_ONLINE
] = {
1777 .name
= "perf:online",
1778 .startup
.single
= perf_event_init_cpu
,
1779 .teardown
.single
= perf_event_exit_cpu
,
1781 [CPUHP_AP_WATCHDOG_ONLINE
] = {
1782 .name
= "lockup_detector:online",
1783 .startup
.single
= lockup_detector_online_cpu
,
1784 .teardown
.single
= lockup_detector_offline_cpu
,
1786 [CPUHP_AP_WORKQUEUE_ONLINE
] = {
1787 .name
= "workqueue:online",
1788 .startup
.single
= workqueue_online_cpu
,
1789 .teardown
.single
= workqueue_offline_cpu
,
1791 [CPUHP_AP_RANDOM_ONLINE
] = {
1792 .name
= "random:online",
1793 .startup
.single
= random_online_cpu
,
1794 .teardown
.single
= NULL
,
1796 [CPUHP_AP_RCUTREE_ONLINE
] = {
1797 .name
= "RCU/tree:online",
1798 .startup
.single
= rcutree_online_cpu
,
1799 .teardown
.single
= rcutree_offline_cpu
,
1803 * The dynamically registered state space is here
1807 /* Last state is scheduler control setting the cpu active */
1808 [CPUHP_AP_ACTIVE
] = {
1809 .name
= "sched:active",
1810 .startup
.single
= sched_cpu_activate
,
1811 .teardown
.single
= sched_cpu_deactivate
,
1815 /* CPU is fully up and running. */
1818 .startup
.single
= NULL
,
1819 .teardown
.single
= NULL
,
1823 /* Sanity check for callbacks */
1824 static int cpuhp_cb_check(enum cpuhp_state state
)
1826 if (state
<= CPUHP_OFFLINE
|| state
>= CPUHP_ONLINE
)
1832 * Returns a free for dynamic slot assignment of the Online state. The states
1833 * are protected by the cpuhp_slot_states mutex and an empty slot is identified
1834 * by having no name assigned.
1836 static int cpuhp_reserve_state(enum cpuhp_state state
)
1838 enum cpuhp_state i
, end
;
1839 struct cpuhp_step
*step
;
1842 case CPUHP_AP_ONLINE_DYN
:
1843 step
= cpuhp_hp_states
+ CPUHP_AP_ONLINE_DYN
;
1844 end
= CPUHP_AP_ONLINE_DYN_END
;
1846 case CPUHP_BP_PREPARE_DYN
:
1847 step
= cpuhp_hp_states
+ CPUHP_BP_PREPARE_DYN
;
1848 end
= CPUHP_BP_PREPARE_DYN_END
;
1854 for (i
= state
; i
<= end
; i
++, step
++) {
1858 WARN(1, "No more dynamic states available for CPU hotplug\n");
1862 static int cpuhp_store_callbacks(enum cpuhp_state state
, const char *name
,
1863 int (*startup
)(unsigned int cpu
),
1864 int (*teardown
)(unsigned int cpu
),
1865 bool multi_instance
)
1867 /* (Un)Install the callbacks for further cpu hotplug operations */
1868 struct cpuhp_step
*sp
;
1872 * If name is NULL, then the state gets removed.
1874 * CPUHP_AP_ONLINE_DYN and CPUHP_BP_PREPARE_DYN are handed out on
1875 * the first allocation from these dynamic ranges, so the removal
1876 * would trigger a new allocation and clear the wrong (already
1877 * empty) state, leaving the callbacks of the to be cleared state
1878 * dangling, which causes wreckage on the next hotplug operation.
1880 if (name
&& (state
== CPUHP_AP_ONLINE_DYN
||
1881 state
== CPUHP_BP_PREPARE_DYN
)) {
1882 ret
= cpuhp_reserve_state(state
);
1887 sp
= cpuhp_get_step(state
);
1888 if (name
&& sp
->name
)
1891 sp
->startup
.single
= startup
;
1892 sp
->teardown
.single
= teardown
;
1894 sp
->multi_instance
= multi_instance
;
1895 INIT_HLIST_HEAD(&sp
->list
);
1899 static void *cpuhp_get_teardown_cb(enum cpuhp_state state
)
1901 return cpuhp_get_step(state
)->teardown
.single
;
1905 * Call the startup/teardown function for a step either on the AP or
1906 * on the current CPU.
1908 static int cpuhp_issue_call(int cpu
, enum cpuhp_state state
, bool bringup
,
1909 struct hlist_node
*node
)
1911 struct cpuhp_step
*sp
= cpuhp_get_step(state
);
1915 * If there's nothing to do, we done.
1916 * Relies on the union for multi_instance.
1918 if (cpuhp_step_empty(bringup
, sp
))
1921 * The non AP bound callbacks can fail on bringup. On teardown
1922 * e.g. module removal we crash for now.
1925 if (cpuhp_is_ap_state(state
))
1926 ret
= cpuhp_invoke_ap_callback(cpu
, state
, bringup
, node
);
1928 ret
= cpuhp_invoke_callback(cpu
, state
, bringup
, node
, NULL
);
1930 ret
= cpuhp_invoke_callback(cpu
, state
, bringup
, node
, NULL
);
1932 BUG_ON(ret
&& !bringup
);
1937 * Called from __cpuhp_setup_state on a recoverable failure.
1939 * Note: The teardown callbacks for rollback are not allowed to fail!
1941 static void cpuhp_rollback_install(int failedcpu
, enum cpuhp_state state
,
1942 struct hlist_node
*node
)
1946 /* Roll back the already executed steps on the other cpus */
1947 for_each_present_cpu(cpu
) {
1948 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, cpu
);
1949 int cpustate
= st
->state
;
1951 if (cpu
>= failedcpu
)
1954 /* Did we invoke the startup call on that cpu ? */
1955 if (cpustate
>= state
)
1956 cpuhp_issue_call(cpu
, state
, false, node
);
1960 int __cpuhp_state_add_instance_cpuslocked(enum cpuhp_state state
,
1961 struct hlist_node
*node
,
1964 struct cpuhp_step
*sp
;
1968 lockdep_assert_cpus_held();
1970 sp
= cpuhp_get_step(state
);
1971 if (sp
->multi_instance
== false)
1974 mutex_lock(&cpuhp_state_mutex
);
1976 if (!invoke
|| !sp
->startup
.multi
)
1980 * Try to call the startup callback for each present cpu
1981 * depending on the hotplug state of the cpu.
1983 for_each_present_cpu(cpu
) {
1984 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, cpu
);
1985 int cpustate
= st
->state
;
1987 if (cpustate
< state
)
1990 ret
= cpuhp_issue_call(cpu
, state
, true, node
);
1992 if (sp
->teardown
.multi
)
1993 cpuhp_rollback_install(cpu
, state
, node
);
1999 hlist_add_head(node
, &sp
->list
);
2001 mutex_unlock(&cpuhp_state_mutex
);
2005 int __cpuhp_state_add_instance(enum cpuhp_state state
, struct hlist_node
*node
,
2011 ret
= __cpuhp_state_add_instance_cpuslocked(state
, node
, invoke
);
2015 EXPORT_SYMBOL_GPL(__cpuhp_state_add_instance
);
2018 * __cpuhp_setup_state_cpuslocked - Setup the callbacks for an hotplug machine state
2019 * @state: The state to setup
2020 * @name: Name of the step
2021 * @invoke: If true, the startup function is invoked for cpus where
2022 * cpu state >= @state
2023 * @startup: startup callback function
2024 * @teardown: teardown callback function
2025 * @multi_instance: State is set up for multiple instances which get
2028 * The caller needs to hold cpus read locked while calling this function.
2031 * Positive state number if @state is CPUHP_AP_ONLINE_DYN;
2032 * 0 for all other states
2033 * On failure: proper (negative) error code
2035 int __cpuhp_setup_state_cpuslocked(enum cpuhp_state state
,
2036 const char *name
, bool invoke
,
2037 int (*startup
)(unsigned int cpu
),
2038 int (*teardown
)(unsigned int cpu
),
2039 bool multi_instance
)
2044 lockdep_assert_cpus_held();
2046 if (cpuhp_cb_check(state
) || !name
)
2049 mutex_lock(&cpuhp_state_mutex
);
2051 ret
= cpuhp_store_callbacks(state
, name
, startup
, teardown
,
2054 dynstate
= state
== CPUHP_AP_ONLINE_DYN
;
2055 if (ret
> 0 && dynstate
) {
2060 if (ret
|| !invoke
|| !startup
)
2064 * Try to call the startup callback for each present cpu
2065 * depending on the hotplug state of the cpu.
2067 for_each_present_cpu(cpu
) {
2068 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, cpu
);
2069 int cpustate
= st
->state
;
2071 if (cpustate
< state
)
2074 ret
= cpuhp_issue_call(cpu
, state
, true, NULL
);
2077 cpuhp_rollback_install(cpu
, state
, NULL
);
2078 cpuhp_store_callbacks(state
, NULL
, NULL
, NULL
, false);
2083 mutex_unlock(&cpuhp_state_mutex
);
2085 * If the requested state is CPUHP_AP_ONLINE_DYN, return the
2086 * dynamically allocated state in case of success.
2088 if (!ret
&& dynstate
)
2092 EXPORT_SYMBOL(__cpuhp_setup_state_cpuslocked
);
2094 int __cpuhp_setup_state(enum cpuhp_state state
,
2095 const char *name
, bool invoke
,
2096 int (*startup
)(unsigned int cpu
),
2097 int (*teardown
)(unsigned int cpu
),
2098 bool multi_instance
)
2103 ret
= __cpuhp_setup_state_cpuslocked(state
, name
, invoke
, startup
,
2104 teardown
, multi_instance
);
2108 EXPORT_SYMBOL(__cpuhp_setup_state
);
2110 int __cpuhp_state_remove_instance(enum cpuhp_state state
,
2111 struct hlist_node
*node
, bool invoke
)
2113 struct cpuhp_step
*sp
= cpuhp_get_step(state
);
2116 BUG_ON(cpuhp_cb_check(state
));
2118 if (!sp
->multi_instance
)
2122 mutex_lock(&cpuhp_state_mutex
);
2124 if (!invoke
|| !cpuhp_get_teardown_cb(state
))
2127 * Call the teardown callback for each present cpu depending
2128 * on the hotplug state of the cpu. This function is not
2129 * allowed to fail currently!
2131 for_each_present_cpu(cpu
) {
2132 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, cpu
);
2133 int cpustate
= st
->state
;
2135 if (cpustate
>= state
)
2136 cpuhp_issue_call(cpu
, state
, false, node
);
2141 mutex_unlock(&cpuhp_state_mutex
);
2146 EXPORT_SYMBOL_GPL(__cpuhp_state_remove_instance
);
2149 * __cpuhp_remove_state_cpuslocked - Remove the callbacks for an hotplug machine state
2150 * @state: The state to remove
2151 * @invoke: If true, the teardown function is invoked for cpus where
2152 * cpu state >= @state
2154 * The caller needs to hold cpus read locked while calling this function.
2155 * The teardown callback is currently not allowed to fail. Think
2156 * about module removal!
2158 void __cpuhp_remove_state_cpuslocked(enum cpuhp_state state
, bool invoke
)
2160 struct cpuhp_step
*sp
= cpuhp_get_step(state
);
2163 BUG_ON(cpuhp_cb_check(state
));
2165 lockdep_assert_cpus_held();
2167 mutex_lock(&cpuhp_state_mutex
);
2168 if (sp
->multi_instance
) {
2169 WARN(!hlist_empty(&sp
->list
),
2170 "Error: Removing state %d which has instances left.\n",
2175 if (!invoke
|| !cpuhp_get_teardown_cb(state
))
2179 * Call the teardown callback for each present cpu depending
2180 * on the hotplug state of the cpu. This function is not
2181 * allowed to fail currently!
2183 for_each_present_cpu(cpu
) {
2184 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, cpu
);
2185 int cpustate
= st
->state
;
2187 if (cpustate
>= state
)
2188 cpuhp_issue_call(cpu
, state
, false, NULL
);
2191 cpuhp_store_callbacks(state
, NULL
, NULL
, NULL
, false);
2192 mutex_unlock(&cpuhp_state_mutex
);
2194 EXPORT_SYMBOL(__cpuhp_remove_state_cpuslocked
);
2196 void __cpuhp_remove_state(enum cpuhp_state state
, bool invoke
)
2199 __cpuhp_remove_state_cpuslocked(state
, invoke
);
2202 EXPORT_SYMBOL(__cpuhp_remove_state
);
2204 #ifdef CONFIG_HOTPLUG_SMT
2205 static void cpuhp_offline_cpu_device(unsigned int cpu
)
2207 struct device
*dev
= get_cpu_device(cpu
);
2209 dev
->offline
= true;
2210 /* Tell user space about the state change */
2211 kobject_uevent(&dev
->kobj
, KOBJ_OFFLINE
);
2214 static void cpuhp_online_cpu_device(unsigned int cpu
)
2216 struct device
*dev
= get_cpu_device(cpu
);
2218 dev
->offline
= false;
2219 /* Tell user space about the state change */
2220 kobject_uevent(&dev
->kobj
, KOBJ_ONLINE
);
2223 int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval
)
2227 cpu_maps_update_begin();
2228 for_each_online_cpu(cpu
) {
2229 if (topology_is_primary_thread(cpu
))
2231 ret
= cpu_down_maps_locked(cpu
, CPUHP_OFFLINE
);
2235 * As this needs to hold the cpu maps lock it's impossible
2236 * to call device_offline() because that ends up calling
2237 * cpu_down() which takes cpu maps lock. cpu maps lock
2238 * needs to be held as this might race against in kernel
2239 * abusers of the hotplug machinery (thermal management).
2241 * So nothing would update device:offline state. That would
2242 * leave the sysfs entry stale and prevent onlining after
2243 * smt control has been changed to 'off' again. This is
2244 * called under the sysfs hotplug lock, so it is properly
2245 * serialized against the regular offline usage.
2247 cpuhp_offline_cpu_device(cpu
);
2250 cpu_smt_control
= ctrlval
;
2251 cpu_maps_update_done();
2255 int cpuhp_smt_enable(void)
2259 cpu_maps_update_begin();
2260 cpu_smt_control
= CPU_SMT_ENABLED
;
2261 for_each_present_cpu(cpu
) {
2262 /* Skip online CPUs and CPUs on offline nodes */
2263 if (cpu_online(cpu
) || !node_online(cpu_to_node(cpu
)))
2265 ret
= _cpu_up(cpu
, 0, CPUHP_ONLINE
);
2268 /* See comment in cpuhp_smt_disable() */
2269 cpuhp_online_cpu_device(cpu
);
2271 cpu_maps_update_done();
2276 #if defined(CONFIG_SYSFS) && defined(CONFIG_HOTPLUG_CPU)
2277 static ssize_t
state_show(struct device
*dev
,
2278 struct device_attribute
*attr
, char *buf
)
2280 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, dev
->id
);
2282 return sprintf(buf
, "%d\n", st
->state
);
2284 static DEVICE_ATTR_RO(state
);
2286 static ssize_t
target_store(struct device
*dev
, struct device_attribute
*attr
,
2287 const char *buf
, size_t count
)
2289 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, dev
->id
);
2290 struct cpuhp_step
*sp
;
2293 ret
= kstrtoint(buf
, 10, &target
);
2297 #ifdef CONFIG_CPU_HOTPLUG_STATE_CONTROL
2298 if (target
< CPUHP_OFFLINE
|| target
> CPUHP_ONLINE
)
2301 if (target
!= CPUHP_OFFLINE
&& target
!= CPUHP_ONLINE
)
2305 ret
= lock_device_hotplug_sysfs();
2309 mutex_lock(&cpuhp_state_mutex
);
2310 sp
= cpuhp_get_step(target
);
2311 ret
= !sp
->name
|| sp
->cant_stop
? -EINVAL
: 0;
2312 mutex_unlock(&cpuhp_state_mutex
);
2316 if (st
->state
< target
)
2317 ret
= cpu_up(dev
->id
, target
);
2319 ret
= cpu_down(dev
->id
, target
);
2321 unlock_device_hotplug();
2322 return ret
? ret
: count
;
2325 static ssize_t
target_show(struct device
*dev
,
2326 struct device_attribute
*attr
, char *buf
)
2328 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, dev
->id
);
2330 return sprintf(buf
, "%d\n", st
->target
);
2332 static DEVICE_ATTR_RW(target
);
2334 static ssize_t
fail_store(struct device
*dev
, struct device_attribute
*attr
,
2335 const char *buf
, size_t count
)
2337 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, dev
->id
);
2338 struct cpuhp_step
*sp
;
2341 ret
= kstrtoint(buf
, 10, &fail
);
2345 if (fail
== CPUHP_INVALID
) {
2350 if (fail
< CPUHP_OFFLINE
|| fail
> CPUHP_ONLINE
)
2354 * Cannot fail STARTING/DYING callbacks.
2356 if (cpuhp_is_atomic_state(fail
))
2360 * DEAD callbacks cannot fail...
2361 * ... neither can CPUHP_BRINGUP_CPU during hotunplug. The latter
2362 * triggering STARTING callbacks, a failure in this state would
2365 if (fail
<= CPUHP_BRINGUP_CPU
&& st
->state
> CPUHP_BRINGUP_CPU
)
2369 * Cannot fail anything that doesn't have callbacks.
2371 mutex_lock(&cpuhp_state_mutex
);
2372 sp
= cpuhp_get_step(fail
);
2373 if (!sp
->startup
.single
&& !sp
->teardown
.single
)
2375 mutex_unlock(&cpuhp_state_mutex
);
2384 static ssize_t
fail_show(struct device
*dev
,
2385 struct device_attribute
*attr
, char *buf
)
2387 struct cpuhp_cpu_state
*st
= per_cpu_ptr(&cpuhp_state
, dev
->id
);
2389 return sprintf(buf
, "%d\n", st
->fail
);
2392 static DEVICE_ATTR_RW(fail
);
2394 static struct attribute
*cpuhp_cpu_attrs
[] = {
2395 &dev_attr_state
.attr
,
2396 &dev_attr_target
.attr
,
2397 &dev_attr_fail
.attr
,
2401 static const struct attribute_group cpuhp_cpu_attr_group
= {
2402 .attrs
= cpuhp_cpu_attrs
,
2407 static ssize_t
states_show(struct device
*dev
,
2408 struct device_attribute
*attr
, char *buf
)
2410 ssize_t cur
, res
= 0;
2413 mutex_lock(&cpuhp_state_mutex
);
2414 for (i
= CPUHP_OFFLINE
; i
<= CPUHP_ONLINE
; i
++) {
2415 struct cpuhp_step
*sp
= cpuhp_get_step(i
);
2418 cur
= sprintf(buf
, "%3d: %s\n", i
, sp
->name
);
2423 mutex_unlock(&cpuhp_state_mutex
);
2426 static DEVICE_ATTR_RO(states
);
2428 static struct attribute
*cpuhp_cpu_root_attrs
[] = {
2429 &dev_attr_states
.attr
,
2433 static const struct attribute_group cpuhp_cpu_root_attr_group
= {
2434 .attrs
= cpuhp_cpu_root_attrs
,
2439 #ifdef CONFIG_HOTPLUG_SMT
2442 __store_smt_control(struct device
*dev
, struct device_attribute
*attr
,
2443 const char *buf
, size_t count
)
2447 if (sysfs_streq(buf
, "on"))
2448 ctrlval
= CPU_SMT_ENABLED
;
2449 else if (sysfs_streq(buf
, "off"))
2450 ctrlval
= CPU_SMT_DISABLED
;
2451 else if (sysfs_streq(buf
, "forceoff"))
2452 ctrlval
= CPU_SMT_FORCE_DISABLED
;
2456 if (cpu_smt_control
== CPU_SMT_FORCE_DISABLED
)
2459 if (cpu_smt_control
== CPU_SMT_NOT_SUPPORTED
)
2462 ret
= lock_device_hotplug_sysfs();
2466 if (ctrlval
!= cpu_smt_control
) {
2468 case CPU_SMT_ENABLED
:
2469 ret
= cpuhp_smt_enable();
2471 case CPU_SMT_DISABLED
:
2472 case CPU_SMT_FORCE_DISABLED
:
2473 ret
= cpuhp_smt_disable(ctrlval
);
2478 unlock_device_hotplug();
2479 return ret
? ret
: count
;
2482 #else /* !CONFIG_HOTPLUG_SMT */
2484 __store_smt_control(struct device
*dev
, struct device_attribute
*attr
,
2485 const char *buf
, size_t count
)
2489 #endif /* CONFIG_HOTPLUG_SMT */
2491 static const char *smt_states
[] = {
2492 [CPU_SMT_ENABLED
] = "on",
2493 [CPU_SMT_DISABLED
] = "off",
2494 [CPU_SMT_FORCE_DISABLED
] = "forceoff",
2495 [CPU_SMT_NOT_SUPPORTED
] = "notsupported",
2496 [CPU_SMT_NOT_IMPLEMENTED
] = "notimplemented",
2499 static ssize_t
control_show(struct device
*dev
,
2500 struct device_attribute
*attr
, char *buf
)
2502 const char *state
= smt_states
[cpu_smt_control
];
2504 return snprintf(buf
, PAGE_SIZE
- 2, "%s\n", state
);
2507 static ssize_t
control_store(struct device
*dev
, struct device_attribute
*attr
,
2508 const char *buf
, size_t count
)
2510 return __store_smt_control(dev
, attr
, buf
, count
);
2512 static DEVICE_ATTR_RW(control
);
2514 static ssize_t
active_show(struct device
*dev
,
2515 struct device_attribute
*attr
, char *buf
)
2517 return snprintf(buf
, PAGE_SIZE
- 2, "%d\n", sched_smt_active());
2519 static DEVICE_ATTR_RO(active
);
2521 static struct attribute
*cpuhp_smt_attrs
[] = {
2522 &dev_attr_control
.attr
,
2523 &dev_attr_active
.attr
,
2527 static const struct attribute_group cpuhp_smt_attr_group
= {
2528 .attrs
= cpuhp_smt_attrs
,
2533 static int __init
cpu_smt_sysfs_init(void)
2535 return sysfs_create_group(&cpu_subsys
.dev_root
->kobj
,
2536 &cpuhp_smt_attr_group
);
2539 static int __init
cpuhp_sysfs_init(void)
2543 ret
= cpu_smt_sysfs_init();
2547 ret
= sysfs_create_group(&cpu_subsys
.dev_root
->kobj
,
2548 &cpuhp_cpu_root_attr_group
);
2552 for_each_possible_cpu(cpu
) {
2553 struct device
*dev
= get_cpu_device(cpu
);
2557 ret
= sysfs_create_group(&dev
->kobj
, &cpuhp_cpu_attr_group
);
2563 device_initcall(cpuhp_sysfs_init
);
2564 #endif /* CONFIG_SYSFS && CONFIG_HOTPLUG_CPU */
2567 * cpu_bit_bitmap[] is a special, "compressed" data structure that
2568 * represents all NR_CPUS bits binary values of 1<<nr.
2570 * It is used by cpumask_of() to get a constant address to a CPU
2571 * mask value that has a single bit set only.
2574 /* cpu_bit_bitmap[0] is empty - so we can back into it */
2575 #define MASK_DECLARE_1(x) [x+1][0] = (1UL << (x))
2576 #define MASK_DECLARE_2(x) MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
2577 #define MASK_DECLARE_4(x) MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
2578 #define MASK_DECLARE_8(x) MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
2580 const unsigned long cpu_bit_bitmap
[BITS_PER_LONG
+1][BITS_TO_LONGS(NR_CPUS
)] = {
2582 MASK_DECLARE_8(0), MASK_DECLARE_8(8),
2583 MASK_DECLARE_8(16), MASK_DECLARE_8(24),
2584 #if BITS_PER_LONG > 32
2585 MASK_DECLARE_8(32), MASK_DECLARE_8(40),
2586 MASK_DECLARE_8(48), MASK_DECLARE_8(56),
2589 EXPORT_SYMBOL_GPL(cpu_bit_bitmap
);
2591 const DECLARE_BITMAP(cpu_all_bits
, NR_CPUS
) = CPU_BITS_ALL
;
2592 EXPORT_SYMBOL(cpu_all_bits
);
2594 #ifdef CONFIG_INIT_ALL_POSSIBLE
2595 struct cpumask __cpu_possible_mask __read_mostly
2598 struct cpumask __cpu_possible_mask __read_mostly
;
2600 EXPORT_SYMBOL(__cpu_possible_mask
);
2602 struct cpumask __cpu_online_mask __read_mostly
;
2603 EXPORT_SYMBOL(__cpu_online_mask
);
2605 struct cpumask __cpu_present_mask __read_mostly
;
2606 EXPORT_SYMBOL(__cpu_present_mask
);
2608 struct cpumask __cpu_active_mask __read_mostly
;
2609 EXPORT_SYMBOL(__cpu_active_mask
);
2611 struct cpumask __cpu_dying_mask __read_mostly
;
2612 EXPORT_SYMBOL(__cpu_dying_mask
);
2614 atomic_t __num_online_cpus __read_mostly
;
2615 EXPORT_SYMBOL(__num_online_cpus
);
2617 void init_cpu_present(const struct cpumask
*src
)
2619 cpumask_copy(&__cpu_present_mask
, src
);
2622 void init_cpu_possible(const struct cpumask
*src
)
2624 cpumask_copy(&__cpu_possible_mask
, src
);
2627 void init_cpu_online(const struct cpumask
*src
)
2629 cpumask_copy(&__cpu_online_mask
, src
);
2632 void set_cpu_online(unsigned int cpu
, bool online
)
2635 * atomic_inc/dec() is required to handle the horrid abuse of this
2636 * function by the reboot and kexec code which invoke it from
2637 * IPI/NMI broadcasts when shutting down CPUs. Invocation from
2638 * regular CPU hotplug is properly serialized.
2640 * Note, that the fact that __num_online_cpus is of type atomic_t
2641 * does not protect readers which are not serialized against
2642 * concurrent hotplug operations.
2645 if (!cpumask_test_and_set_cpu(cpu
, &__cpu_online_mask
))
2646 atomic_inc(&__num_online_cpus
);
2648 if (cpumask_test_and_clear_cpu(cpu
, &__cpu_online_mask
))
2649 atomic_dec(&__num_online_cpus
);
2654 * Activate the first processor.
2656 void __init
boot_cpu_init(void)
2658 int cpu
= smp_processor_id();
2660 /* Mark the boot cpu "present", "online" etc for SMP and UP case */
2661 set_cpu_online(cpu
, true);
2662 set_cpu_active(cpu
, true);
2663 set_cpu_present(cpu
, true);
2664 set_cpu_possible(cpu
, true);
2667 __boot_cpu_id
= cpu
;
2672 * Must be called _AFTER_ setting up the per_cpu areas
2674 void __init
boot_cpu_hotplug_init(void)
2677 cpumask_set_cpu(smp_processor_id(), &cpus_booted_once_mask
);
2679 this_cpu_write(cpuhp_state
.state
, CPUHP_ONLINE
);
2683 * These are used for a global "mitigations=" cmdline option for toggling
2684 * optional CPU mitigations.
2686 enum cpu_mitigations
{
2687 CPU_MITIGATIONS_OFF
,
2688 CPU_MITIGATIONS_AUTO
,
2689 CPU_MITIGATIONS_AUTO_NOSMT
,
2692 static enum cpu_mitigations cpu_mitigations __ro_after_init
=
2693 CPU_MITIGATIONS_AUTO
;
2695 static int __init
mitigations_parse_cmdline(char *arg
)
2697 if (!strcmp(arg
, "off"))
2698 cpu_mitigations
= CPU_MITIGATIONS_OFF
;
2699 else if (!strcmp(arg
, "auto"))
2700 cpu_mitigations
= CPU_MITIGATIONS_AUTO
;
2701 else if (!strcmp(arg
, "auto,nosmt"))
2702 cpu_mitigations
= CPU_MITIGATIONS_AUTO_NOSMT
;
2704 pr_crit("Unsupported mitigations=%s, system may still be vulnerable\n",
2709 early_param("mitigations", mitigations_parse_cmdline
);
2711 /* mitigations=off */
2712 bool cpu_mitigations_off(void)
2714 return cpu_mitigations
== CPU_MITIGATIONS_OFF
;
2716 EXPORT_SYMBOL_GPL(cpu_mitigations_off
);
2718 /* mitigations=auto,nosmt */
2719 bool cpu_mitigations_auto_nosmt(void)
2721 return cpu_mitigations
== CPU_MITIGATIONS_AUTO_NOSMT
;
2723 EXPORT_SYMBOL_GPL(cpu_mitigations_auto_nosmt
);