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>
38 #include <trace/events/power.h>
39 #define CREATE_TRACE_POINTS
40 #include <trace/events/cpuhp.h>
45 * struct cpuhp_cpu_state - Per cpu hotplug state storage
46 * @state: The current cpu state
47 * @target: The target state
48 * @fail: Current CPU hotplug callback state
49 * @thread: Pointer to the hotplug thread
50 * @should_run: Thread should execute
51 * @rollback: Perform a rollback
52 * @single: Single callback invocation
53 * @bringup: Single callback bringup or teardown selector
55 * @node: Remote CPU node; for multi-instance, do a
56 * single entry callback for install/remove
57 * @last: For multi-instance rollback, remember how far we got
58 * @cb_state: The state for a single callback (install/uninstall)
59 * @result: Result of the operation
60 * @done_up: Signal completion to the issuer of the task for cpu-up
61 * @done_down: Signal completion to the issuer of the task for cpu-down
63 struct cpuhp_cpu_state {
64 enum cpuhp_state state;
65 enum cpuhp_state target;
66 enum cpuhp_state fail;
68 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(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(st->cpu) != !bringup)
489 set_cpu_dying(st->cpu, !bringup);
495 cpuhp_reset_state(struct cpuhp_cpu_state *st, enum cpuhp_state prev_state)
497 bool bringup = !st->bringup;
499 st->target = prev_state;
502 * Already rolling back. No need invert the bringup value or to change
511 * If we have st->last we need to undo partial multi_instance of this
512 * state first. Otherwise start undo at the previous state.
521 st->bringup = bringup;
522 if (cpu_dying(st->cpu) != !bringup)
523 set_cpu_dying(st->cpu, !bringup);
526 /* Regular hotplug invocation of the AP hotplug thread */
527 static void __cpuhp_kick_ap(struct cpuhp_cpu_state *st)
529 if (!st->single && st->state == st->target)
534 * Make sure the above stores are visible before should_run becomes
535 * true. Paired with the mb() above in cpuhp_thread_fun()
538 st->should_run = true;
539 wake_up_process(st->thread);
540 wait_for_ap_thread(st, st->bringup);
543 static int cpuhp_kick_ap(struct cpuhp_cpu_state *st, enum cpuhp_state target)
545 enum cpuhp_state prev_state;
548 prev_state = cpuhp_set_state(st, target);
550 if ((ret = st->result)) {
551 cpuhp_reset_state(st, prev_state);
558 static int bringup_wait_for_ap(unsigned int cpu)
560 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
562 /* Wait for the CPU to reach CPUHP_AP_ONLINE_IDLE */
563 wait_for_ap_thread(st, true);
564 if (WARN_ON_ONCE((!cpu_online(cpu))))
567 /* Unpark the hotplug thread of the target cpu */
568 kthread_unpark(st->thread);
571 * SMT soft disabling on X86 requires to bring the CPU out of the
572 * BIOS 'wait for SIPI' state in order to set the CR4.MCE bit. The
573 * CPU marked itself as booted_once in notify_cpu_starting() so the
574 * cpu_smt_allowed() check will now return false if this is not the
577 if (!cpu_smt_allowed(cpu))
580 if (st->target <= CPUHP_AP_ONLINE_IDLE)
583 return cpuhp_kick_ap(st, st->target);
586 static int bringup_cpu(unsigned int cpu)
588 struct task_struct *idle = idle_thread_get(cpu);
592 * Reset stale stack state from the last time this CPU was online.
594 scs_task_reset(idle);
595 kasan_unpoison_task_stack(idle);
598 * Some architectures have to walk the irq descriptors to
599 * setup the vector space for the cpu which comes online.
600 * Prevent irq alloc/free across the bringup.
604 /* Arch-specific enabling code. */
605 ret = __cpu_up(cpu, idle);
609 return bringup_wait_for_ap(cpu);
612 static int finish_cpu(unsigned int cpu)
614 struct task_struct *idle = idle_thread_get(cpu);
615 struct mm_struct *mm = idle->active_mm;
618 * idle_task_exit() will have switched to &init_mm, now
619 * clean up any remaining active_mm state.
622 idle->active_mm = &init_mm;
628 * Hotplug state machine related functions
632 * Get the next state to run. Empty ones will be skipped. Returns true if a
635 * st->state will be modified ahead of time, to match state_to_run, as if it
638 static bool cpuhp_next_state(bool bringup,
639 enum cpuhp_state *state_to_run,
640 struct cpuhp_cpu_state *st,
641 enum cpuhp_state target)
645 if (st->state >= target)
648 *state_to_run = ++st->state;
650 if (st->state <= target)
653 *state_to_run = st->state--;
656 if (!cpuhp_step_empty(bringup, cpuhp_get_step(*state_to_run)))
663 static int cpuhp_invoke_callback_range(bool bringup,
665 struct cpuhp_cpu_state *st,
666 enum cpuhp_state target)
668 enum cpuhp_state state;
671 while (cpuhp_next_state(bringup, &state, st, target)) {
672 err = cpuhp_invoke_callback(cpu, state, bringup, NULL, NULL);
680 static inline bool can_rollback_cpu(struct cpuhp_cpu_state *st)
682 if (IS_ENABLED(CONFIG_HOTPLUG_CPU))
685 * When CPU hotplug is disabled, then taking the CPU down is not
686 * possible because takedown_cpu() and the architecture and
687 * subsystem specific mechanisms are not available. So the CPU
688 * which would be completely unplugged again needs to stay around
689 * in the current state.
691 return st->state <= CPUHP_BRINGUP_CPU;
694 static int cpuhp_up_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
695 enum cpuhp_state target)
697 enum cpuhp_state prev_state = st->state;
700 ret = cpuhp_invoke_callback_range(true, cpu, st, target);
702 pr_debug("CPU UP failed (%d) CPU %u state %s (%d)\n",
703 ret, cpu, cpuhp_get_step(st->state)->name,
706 cpuhp_reset_state(st, prev_state);
707 if (can_rollback_cpu(st))
708 WARN_ON(cpuhp_invoke_callback_range(false, cpu, st,
715 * The cpu hotplug threads manage the bringup and teardown of the cpus
717 static void cpuhp_create(unsigned int cpu)
719 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
721 init_completion(&st->done_up);
722 init_completion(&st->done_down);
726 static int cpuhp_should_run(unsigned int cpu)
728 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
730 return st->should_run;
734 * Execute teardown/startup callbacks on the plugged cpu. Also used to invoke
735 * callbacks when a state gets [un]installed at runtime.
737 * Each invocation of this function by the smpboot thread does a single AP
740 * It has 3 modes of operation:
741 * - single: runs st->cb_state
742 * - up: runs ++st->state, while st->state < st->target
743 * - down: runs st->state--, while st->state > st->target
745 * When complete or on error, should_run is cleared and the completion is fired.
747 static void cpuhp_thread_fun(unsigned int cpu)
749 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
750 bool bringup = st->bringup;
751 enum cpuhp_state state;
753 if (WARN_ON_ONCE(!st->should_run))
757 * ACQUIRE for the cpuhp_should_run() load of ->should_run. Ensures
758 * that if we see ->should_run we also see the rest of the state.
763 * The BP holds the hotplug lock, but we're now running on the AP,
764 * ensure that anybody asserting the lock is held, will actually find
767 lockdep_acquire_cpus_lock();
768 cpuhp_lock_acquire(bringup);
771 state = st->cb_state;
772 st->should_run = false;
774 st->should_run = cpuhp_next_state(bringup, &state, st, st->target);
779 WARN_ON_ONCE(!cpuhp_is_ap_state(state));
781 if (cpuhp_is_atomic_state(state)) {
783 st->result = cpuhp_invoke_callback(cpu, state, bringup, st->node, &st->last);
787 * STARTING/DYING must not fail!
789 WARN_ON_ONCE(st->result);
791 st->result = cpuhp_invoke_callback(cpu, state, bringup, st->node, &st->last);
796 * If we fail on a rollback, we're up a creek without no
797 * paddle, no way forward, no way back. We loose, thanks for
800 WARN_ON_ONCE(st->rollback);
801 st->should_run = false;
805 cpuhp_lock_release(bringup);
806 lockdep_release_cpus_lock();
809 complete_ap_thread(st, bringup);
812 /* Invoke a single callback on a remote cpu */
814 cpuhp_invoke_ap_callback(int cpu, enum cpuhp_state state, bool bringup,
815 struct hlist_node *node)
817 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
820 if (!cpu_online(cpu))
823 cpuhp_lock_acquire(false);
824 cpuhp_lock_release(false);
826 cpuhp_lock_acquire(true);
827 cpuhp_lock_release(true);
830 * If we are up and running, use the hotplug thread. For early calls
831 * we invoke the thread function directly.
834 return cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
836 st->rollback = false;
840 st->bringup = bringup;
841 st->cb_state = state;
847 * If we failed and did a partial, do a rollback.
849 if ((ret = st->result) && st->last) {
851 st->bringup = !bringup;
857 * Clean up the leftovers so the next hotplug operation wont use stale
860 st->node = st->last = NULL;
864 static int cpuhp_kick_ap_work(unsigned int cpu)
866 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
867 enum cpuhp_state prev_state = st->state;
870 cpuhp_lock_acquire(false);
871 cpuhp_lock_release(false);
873 cpuhp_lock_acquire(true);
874 cpuhp_lock_release(true);
876 trace_cpuhp_enter(cpu, st->target, prev_state, cpuhp_kick_ap_work);
877 ret = cpuhp_kick_ap(st, st->target);
878 trace_cpuhp_exit(cpu, st->state, prev_state, ret);
883 static struct smp_hotplug_thread cpuhp_threads = {
884 .store = &cpuhp_state.thread,
885 .create = &cpuhp_create,
886 .thread_should_run = cpuhp_should_run,
887 .thread_fn = cpuhp_thread_fun,
888 .thread_comm = "cpuhp/%u",
892 void __init cpuhp_threads_init(void)
894 BUG_ON(smpboot_register_percpu_thread(&cpuhp_threads));
895 kthread_unpark(this_cpu_read(cpuhp_state.thread));
900 * Serialize hotplug trainwrecks outside of the cpu_hotplug_lock
903 * The operation is still serialized against concurrent CPU hotplug via
904 * cpu_add_remove_lock, i.e. CPU map protection. But it is _not_
905 * serialized against other hotplug related activity like adding or
906 * removing of state callbacks and state instances, which invoke either the
907 * startup or the teardown callback of the affected state.
909 * This is required for subsystems which are unfixable vs. CPU hotplug and
910 * evade lock inversion problems by scheduling work which has to be
911 * completed _before_ cpu_up()/_cpu_down() returns.
913 * Don't even think about adding anything to this for any new code or even
914 * drivers. It's only purpose is to keep existing lock order trainwrecks
917 * For cpu_down() there might be valid reasons to finish cleanups which are
918 * not required to be done under cpu_hotplug_lock, but that's a different
919 * story and would be not invoked via this.
921 static void cpu_up_down_serialize_trainwrecks(bool tasks_frozen)
924 * cpusets delegate hotplug operations to a worker to "solve" the
925 * lock order problems. Wait for the worker, but only if tasks are
926 * _not_ frozen (suspend, hibernate) as that would wait forever.
928 * The wait is required because otherwise the hotplug operation
929 * returns with inconsistent state, which could even be observed in
930 * user space when a new CPU is brought up. The CPU plug uevent
931 * would be delivered and user space reacting on it would fail to
932 * move tasks to the newly plugged CPU up to the point where the
933 * work has finished because up to that point the newly plugged CPU
934 * is not assignable in cpusets/cgroups. On unplug that's not
935 * necessarily a visible issue, but it is still inconsistent state,
936 * which is the real problem which needs to be "fixed". This can't
937 * prevent the transient state between scheduling the work and
938 * returning from waiting for it.
941 cpuset_wait_for_hotplug();
944 #ifdef CONFIG_HOTPLUG_CPU
945 #ifndef arch_clear_mm_cpumask_cpu
946 #define arch_clear_mm_cpumask_cpu(cpu, mm) cpumask_clear_cpu(cpu, mm_cpumask(mm))
950 * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
953 * This function walks all processes, finds a valid mm struct for each one and
954 * then clears a corresponding bit in mm's cpumask. While this all sounds
955 * trivial, there are various non-obvious corner cases, which this function
956 * tries to solve in a safe manner.
958 * Also note that the function uses a somewhat relaxed locking scheme, so it may
959 * be called only for an already offlined CPU.
961 void clear_tasks_mm_cpumask(int cpu)
963 struct task_struct *p;
966 * This function is called after the cpu is taken down and marked
967 * offline, so its not like new tasks will ever get this cpu set in
968 * their mm mask. -- Peter Zijlstra
969 * Thus, we may use rcu_read_lock() here, instead of grabbing
970 * full-fledged tasklist_lock.
972 WARN_ON(cpu_online(cpu));
974 for_each_process(p) {
975 struct task_struct *t;
978 * Main thread might exit, but other threads may still have
979 * a valid mm. Find one.
981 t = find_lock_task_mm(p);
984 arch_clear_mm_cpumask_cpu(cpu, t->mm);
990 /* Take this CPU down. */
991 static int take_cpu_down(void *_param)
993 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
994 enum cpuhp_state target = max((int)st->target, CPUHP_AP_OFFLINE);
995 int err, cpu = smp_processor_id();
998 /* Ensure this CPU doesn't handle any more interrupts. */
999 err = __cpu_disable();
1004 * Must be called from CPUHP_TEARDOWN_CPU, which means, as we are going
1005 * down, that the current state is CPUHP_TEARDOWN_CPU - 1.
1007 WARN_ON(st->state != (CPUHP_TEARDOWN_CPU - 1));
1009 /* Invoke the former CPU_DYING callbacks */
1010 ret = cpuhp_invoke_callback_range(false, cpu, st, target);
1013 * DYING must not fail!
1017 /* Give up timekeeping duties */
1018 tick_handover_do_timer();
1019 /* Remove CPU from timer broadcasting */
1020 tick_offline_cpu(cpu);
1021 /* Park the stopper thread */
1022 stop_machine_park(cpu);
1026 static int takedown_cpu(unsigned int cpu)
1028 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1031 /* Park the smpboot threads */
1032 kthread_park(st->thread);
1035 * Prevent irq alloc/free while the dying cpu reorganizes the
1036 * interrupt affinities.
1041 * So now all preempt/rcu users must observe !cpu_active().
1043 err = stop_machine_cpuslocked(take_cpu_down, NULL, cpumask_of(cpu));
1045 /* CPU refused to die */
1046 irq_unlock_sparse();
1047 /* Unpark the hotplug thread so we can rollback there */
1048 kthread_unpark(st->thread);
1051 BUG_ON(cpu_online(cpu));
1054 * The teardown callback for CPUHP_AP_SCHED_STARTING will have removed
1055 * all runnable tasks from the CPU, there's only the idle task left now
1056 * that the migration thread is done doing the stop_machine thing.
1058 * Wait for the stop thread to go away.
1060 wait_for_ap_thread(st, false);
1061 BUG_ON(st->state != CPUHP_AP_IDLE_DEAD);
1063 /* Interrupts are moved away from the dying cpu, reenable alloc/free */
1064 irq_unlock_sparse();
1066 hotplug_cpu__broadcast_tick_pull(cpu);
1067 /* This actually kills the CPU. */
1070 tick_cleanup_dead_cpu(cpu);
1071 rcutree_migrate_callbacks(cpu);
1075 static void cpuhp_complete_idle_dead(void *arg)
1077 struct cpuhp_cpu_state *st = arg;
1079 complete_ap_thread(st, false);
1082 void cpuhp_report_idle_dead(void)
1084 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
1086 BUG_ON(st->state != CPUHP_AP_OFFLINE);
1087 rcu_report_dead(smp_processor_id());
1088 st->state = CPUHP_AP_IDLE_DEAD;
1090 * We cannot call complete after rcu_report_dead() so we delegate it
1093 smp_call_function_single(cpumask_first(cpu_online_mask),
1094 cpuhp_complete_idle_dead, st, 0);
1097 static int cpuhp_down_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
1098 enum cpuhp_state target)
1100 enum cpuhp_state prev_state = st->state;
1103 ret = cpuhp_invoke_callback_range(false, cpu, st, target);
1105 pr_debug("CPU DOWN failed (%d) CPU %u state %s (%d)\n",
1106 ret, cpu, cpuhp_get_step(st->state)->name,
1109 cpuhp_reset_state(st, prev_state);
1111 if (st->state < prev_state)
1112 WARN_ON(cpuhp_invoke_callback_range(true, cpu, st,
1119 /* Requires cpu_add_remove_lock to be held */
1120 static int __ref _cpu_down(unsigned int cpu, int tasks_frozen,
1121 enum cpuhp_state target)
1123 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1124 int prev_state, ret = 0;
1126 if (num_online_cpus() == 1)
1129 if (!cpu_present(cpu))
1134 cpuhp_tasks_frozen = tasks_frozen;
1136 prev_state = cpuhp_set_state(st, target);
1138 * If the current CPU state is in the range of the AP hotplug thread,
1139 * then we need to kick the thread.
1141 if (st->state > CPUHP_TEARDOWN_CPU) {
1142 st->target = max((int)target, CPUHP_TEARDOWN_CPU);
1143 ret = cpuhp_kick_ap_work(cpu);
1145 * The AP side has done the error rollback already. Just
1146 * return the error code..
1152 * We might have stopped still in the range of the AP hotplug
1153 * thread. Nothing to do anymore.
1155 if (st->state > CPUHP_TEARDOWN_CPU)
1158 st->target = target;
1161 * The AP brought itself down to CPUHP_TEARDOWN_CPU. So we need
1162 * to do the further cleanups.
1164 ret = cpuhp_down_callbacks(cpu, st, target);
1165 if (ret && st->state < prev_state) {
1166 if (st->state == CPUHP_TEARDOWN_CPU) {
1167 cpuhp_reset_state(st, prev_state);
1168 __cpuhp_kick_ap(st);
1170 WARN(1, "DEAD callback error for CPU%d", cpu);
1175 cpus_write_unlock();
1177 * Do post unplug cleanup. This is still protected against
1178 * concurrent CPU hotplug via cpu_add_remove_lock.
1180 lockup_detector_cleanup();
1182 cpu_up_down_serialize_trainwrecks(tasks_frozen);
1186 static int cpu_down_maps_locked(unsigned int cpu, enum cpuhp_state target)
1188 if (cpu_hotplug_disabled)
1190 return _cpu_down(cpu, 0, target);
1193 static int cpu_down(unsigned int cpu, enum cpuhp_state target)
1197 cpu_maps_update_begin();
1198 err = cpu_down_maps_locked(cpu, target);
1199 cpu_maps_update_done();
1204 * cpu_device_down - Bring down a cpu device
1205 * @dev: Pointer to the cpu device to offline
1207 * This function is meant to be used by device core cpu subsystem only.
1209 * Other subsystems should use remove_cpu() instead.
1211 * Return: %0 on success or a negative errno code
1213 int cpu_device_down(struct device *dev)
1215 return cpu_down(dev->id, CPUHP_OFFLINE);
1218 int remove_cpu(unsigned int cpu)
1222 lock_device_hotplug();
1223 ret = device_offline(get_cpu_device(cpu));
1224 unlock_device_hotplug();
1228 EXPORT_SYMBOL_GPL(remove_cpu);
1230 void smp_shutdown_nonboot_cpus(unsigned int primary_cpu)
1235 cpu_maps_update_begin();
1238 * Make certain the cpu I'm about to reboot on is online.
1240 * This is inline to what migrate_to_reboot_cpu() already do.
1242 if (!cpu_online(primary_cpu))
1243 primary_cpu = cpumask_first(cpu_online_mask);
1245 for_each_online_cpu(cpu) {
1246 if (cpu == primary_cpu)
1249 error = cpu_down_maps_locked(cpu, CPUHP_OFFLINE);
1251 pr_err("Failed to offline CPU%d - error=%d",
1258 * Ensure all but the reboot CPU are offline.
1260 BUG_ON(num_online_cpus() > 1);
1263 * Make sure the CPUs won't be enabled by someone else after this
1264 * point. Kexec will reboot to a new kernel shortly resetting
1265 * everything along the way.
1267 cpu_hotplug_disabled++;
1269 cpu_maps_update_done();
1273 #define takedown_cpu NULL
1274 #endif /*CONFIG_HOTPLUG_CPU*/
1277 * notify_cpu_starting(cpu) - Invoke the callbacks on the starting CPU
1278 * @cpu: cpu that just started
1280 * It must be called by the arch code on the new cpu, before the new cpu
1281 * enables interrupts and before the "boot" cpu returns from __cpu_up().
1283 void notify_cpu_starting(unsigned int cpu)
1285 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1286 enum cpuhp_state target = min((int)st->target, CPUHP_AP_ONLINE);
1289 rcu_cpu_starting(cpu); /* Enables RCU usage on this CPU. */
1290 cpumask_set_cpu(cpu, &cpus_booted_once_mask);
1291 ret = cpuhp_invoke_callback_range(true, cpu, st, target);
1294 * STARTING must not fail!
1300 * Called from the idle task. Wake up the controlling task which brings the
1301 * hotplug thread of the upcoming CPU up and then delegates the rest of the
1302 * online bringup to the hotplug thread.
1304 void cpuhp_online_idle(enum cpuhp_state state)
1306 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
1308 /* Happens for the boot cpu */
1309 if (state != CPUHP_AP_ONLINE_IDLE)
1313 * Unpart the stopper thread before we start the idle loop (and start
1314 * scheduling); this ensures the stopper task is always available.
1316 stop_machine_unpark(smp_processor_id());
1318 st->state = CPUHP_AP_ONLINE_IDLE;
1319 complete_ap_thread(st, true);
1322 /* Requires cpu_add_remove_lock to be held */
1323 static int _cpu_up(unsigned int cpu, int tasks_frozen, enum cpuhp_state target)
1325 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1326 struct task_struct *idle;
1331 if (!cpu_present(cpu)) {
1337 * The caller of cpu_up() might have raced with another
1338 * caller. Nothing to do.
1340 if (st->state >= target)
1343 if (st->state == CPUHP_OFFLINE) {
1344 /* Let it fail before we try to bring the cpu up */
1345 idle = idle_thread_get(cpu);
1347 ret = PTR_ERR(idle);
1352 cpuhp_tasks_frozen = tasks_frozen;
1354 cpuhp_set_state(st, target);
1356 * If the current CPU state is in the range of the AP hotplug thread,
1357 * then we need to kick the thread once more.
1359 if (st->state > CPUHP_BRINGUP_CPU) {
1360 ret = cpuhp_kick_ap_work(cpu);
1362 * The AP side has done the error rollback already. Just
1363 * return the error code..
1370 * Try to reach the target state. We max out on the BP at
1371 * CPUHP_BRINGUP_CPU. After that the AP hotplug thread is
1372 * responsible for bringing it up to the target state.
1374 target = min((int)target, CPUHP_BRINGUP_CPU);
1375 ret = cpuhp_up_callbacks(cpu, st, target);
1377 cpus_write_unlock();
1379 cpu_up_down_serialize_trainwrecks(tasks_frozen);
1383 static int cpu_up(unsigned int cpu, enum cpuhp_state target)
1387 if (!cpu_possible(cpu)) {
1388 pr_err("can't online cpu %d because it is not configured as may-hotadd at boot time\n",
1390 #if defined(CONFIG_IA64)
1391 pr_err("please check additional_cpus= boot parameter\n");
1396 err = try_online_node(cpu_to_node(cpu));
1400 cpu_maps_update_begin();
1402 if (cpu_hotplug_disabled) {
1406 if (!cpu_smt_allowed(cpu)) {
1411 err = _cpu_up(cpu, 0, target);
1413 cpu_maps_update_done();
1418 * cpu_device_up - Bring up a cpu device
1419 * @dev: Pointer to the cpu device to online
1421 * This function is meant to be used by device core cpu subsystem only.
1423 * Other subsystems should use add_cpu() instead.
1425 * Return: %0 on success or a negative errno code
1427 int cpu_device_up(struct device *dev)
1429 return cpu_up(dev->id, CPUHP_ONLINE);
1432 int add_cpu(unsigned int cpu)
1436 lock_device_hotplug();
1437 ret = device_online(get_cpu_device(cpu));
1438 unlock_device_hotplug();
1442 EXPORT_SYMBOL_GPL(add_cpu);
1445 * bringup_hibernate_cpu - Bring up the CPU that we hibernated on
1446 * @sleep_cpu: The cpu we hibernated on and should be brought up.
1448 * On some architectures like arm64, we can hibernate on any CPU, but on
1449 * wake up the CPU we hibernated on might be offline as a side effect of
1450 * using maxcpus= for example.
1452 * Return: %0 on success or a negative errno code
1454 int bringup_hibernate_cpu(unsigned int sleep_cpu)
1458 if (!cpu_online(sleep_cpu)) {
1459 pr_info("Hibernated on a CPU that is offline! Bringing CPU up.\n");
1460 ret = cpu_up(sleep_cpu, CPUHP_ONLINE);
1462 pr_err("Failed to bring hibernate-CPU up!\n");
1469 void bringup_nonboot_cpus(unsigned int setup_max_cpus)
1473 for_each_present_cpu(cpu) {
1474 if (num_online_cpus() >= setup_max_cpus)
1476 if (!cpu_online(cpu))
1477 cpu_up(cpu, CPUHP_ONLINE);
1481 #ifdef CONFIG_PM_SLEEP_SMP
1482 static cpumask_var_t frozen_cpus;
1484 int freeze_secondary_cpus(int primary)
1488 cpu_maps_update_begin();
1489 if (primary == -1) {
1490 primary = cpumask_first(cpu_online_mask);
1491 if (!housekeeping_cpu(primary, HK_FLAG_TIMER))
1492 primary = housekeeping_any_cpu(HK_FLAG_TIMER);
1494 if (!cpu_online(primary))
1495 primary = cpumask_first(cpu_online_mask);
1499 * We take down all of the non-boot CPUs in one shot to avoid races
1500 * with the userspace trying to use the CPU hotplug at the same time
1502 cpumask_clear(frozen_cpus);
1504 pr_info("Disabling non-boot CPUs ...\n");
1505 for_each_online_cpu(cpu) {
1509 if (pm_wakeup_pending()) {
1510 pr_info("Wakeup pending. Abort CPU freeze\n");
1515 trace_suspend_resume(TPS("CPU_OFF"), cpu, true);
1516 error = _cpu_down(cpu, 1, CPUHP_OFFLINE);
1517 trace_suspend_resume(TPS("CPU_OFF"), cpu, false);
1519 cpumask_set_cpu(cpu, frozen_cpus);
1521 pr_err("Error taking CPU%d down: %d\n", cpu, error);
1527 BUG_ON(num_online_cpus() > 1);
1529 pr_err("Non-boot CPUs are not disabled\n");
1532 * Make sure the CPUs won't be enabled by someone else. We need to do
1533 * this even in case of failure as all freeze_secondary_cpus() users are
1534 * supposed to do thaw_secondary_cpus() on the failure path.
1536 cpu_hotplug_disabled++;
1538 cpu_maps_update_done();
1542 void __weak arch_thaw_secondary_cpus_begin(void)
1546 void __weak arch_thaw_secondary_cpus_end(void)
1550 void thaw_secondary_cpus(void)
1554 /* Allow everyone to use the CPU hotplug again */
1555 cpu_maps_update_begin();
1556 __cpu_hotplug_enable();
1557 if (cpumask_empty(frozen_cpus))
1560 pr_info("Enabling non-boot CPUs ...\n");
1562 arch_thaw_secondary_cpus_begin();
1564 for_each_cpu(cpu, frozen_cpus) {
1565 trace_suspend_resume(TPS("CPU_ON"), cpu, true);
1566 error = _cpu_up(cpu, 1, CPUHP_ONLINE);
1567 trace_suspend_resume(TPS("CPU_ON"), cpu, false);
1569 pr_info("CPU%d is up\n", cpu);
1572 pr_warn("Error taking CPU%d up: %d\n", cpu, error);
1575 arch_thaw_secondary_cpus_end();
1577 cpumask_clear(frozen_cpus);
1579 cpu_maps_update_done();
1582 static int __init alloc_frozen_cpus(void)
1584 if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
1588 core_initcall(alloc_frozen_cpus);
1591 * When callbacks for CPU hotplug notifications are being executed, we must
1592 * ensure that the state of the system with respect to the tasks being frozen
1593 * or not, as reported by the notification, remains unchanged *throughout the
1594 * duration* of the execution of the callbacks.
1595 * Hence we need to prevent the freezer from racing with regular CPU hotplug.
1597 * This synchronization is implemented by mutually excluding regular CPU
1598 * hotplug and Suspend/Hibernate call paths by hooking onto the Suspend/
1599 * Hibernate notifications.
1602 cpu_hotplug_pm_callback(struct notifier_block *nb,
1603 unsigned long action, void *ptr)
1607 case PM_SUSPEND_PREPARE:
1608 case PM_HIBERNATION_PREPARE:
1609 cpu_hotplug_disable();
1612 case PM_POST_SUSPEND:
1613 case PM_POST_HIBERNATION:
1614 cpu_hotplug_enable();
1625 static int __init cpu_hotplug_pm_sync_init(void)
1628 * cpu_hotplug_pm_callback has higher priority than x86
1629 * bsp_pm_callback which depends on cpu_hotplug_pm_callback
1630 * to disable cpu hotplug to avoid cpu hotplug race.
1632 pm_notifier(cpu_hotplug_pm_callback, 0);
1635 core_initcall(cpu_hotplug_pm_sync_init);
1637 #endif /* CONFIG_PM_SLEEP_SMP */
1641 #endif /* CONFIG_SMP */
1643 /* Boot processor state steps */
1644 static struct cpuhp_step cpuhp_hp_states[] = {
1647 .startup.single = NULL,
1648 .teardown.single = NULL,
1651 [CPUHP_CREATE_THREADS]= {
1652 .name = "threads:prepare",
1653 .startup.single = smpboot_create_threads,
1654 .teardown.single = NULL,
1657 [CPUHP_PERF_PREPARE] = {
1658 .name = "perf:prepare",
1659 .startup.single = perf_event_init_cpu,
1660 .teardown.single = perf_event_exit_cpu,
1662 [CPUHP_WORKQUEUE_PREP] = {
1663 .name = "workqueue:prepare",
1664 .startup.single = workqueue_prepare_cpu,
1665 .teardown.single = NULL,
1667 [CPUHP_HRTIMERS_PREPARE] = {
1668 .name = "hrtimers:prepare",
1669 .startup.single = hrtimers_prepare_cpu,
1670 .teardown.single = hrtimers_dead_cpu,
1672 [CPUHP_SMPCFD_PREPARE] = {
1673 .name = "smpcfd:prepare",
1674 .startup.single = smpcfd_prepare_cpu,
1675 .teardown.single = smpcfd_dead_cpu,
1677 [CPUHP_RELAY_PREPARE] = {
1678 .name = "relay:prepare",
1679 .startup.single = relay_prepare_cpu,
1680 .teardown.single = NULL,
1682 [CPUHP_SLAB_PREPARE] = {
1683 .name = "slab:prepare",
1684 .startup.single = slab_prepare_cpu,
1685 .teardown.single = slab_dead_cpu,
1687 [CPUHP_RCUTREE_PREP] = {
1688 .name = "RCU/tree:prepare",
1689 .startup.single = rcutree_prepare_cpu,
1690 .teardown.single = rcutree_dead_cpu,
1693 * On the tear-down path, timers_dead_cpu() must be invoked
1694 * before blk_mq_queue_reinit_notify() from notify_dead(),
1695 * otherwise a RCU stall occurs.
1697 [CPUHP_TIMERS_PREPARE] = {
1698 .name = "timers:prepare",
1699 .startup.single = timers_prepare_cpu,
1700 .teardown.single = timers_dead_cpu,
1702 /* Kicks the plugged cpu into life */
1703 [CPUHP_BRINGUP_CPU] = {
1704 .name = "cpu:bringup",
1705 .startup.single = bringup_cpu,
1706 .teardown.single = finish_cpu,
1709 /* Final state before CPU kills itself */
1710 [CPUHP_AP_IDLE_DEAD] = {
1711 .name = "idle:dead",
1714 * Last state before CPU enters the idle loop to die. Transient state
1715 * for synchronization.
1717 [CPUHP_AP_OFFLINE] = {
1718 .name = "ap:offline",
1721 /* First state is scheduler control. Interrupts are disabled */
1722 [CPUHP_AP_SCHED_STARTING] = {
1723 .name = "sched:starting",
1724 .startup.single = sched_cpu_starting,
1725 .teardown.single = sched_cpu_dying,
1727 [CPUHP_AP_RCUTREE_DYING] = {
1728 .name = "RCU/tree:dying",
1729 .startup.single = NULL,
1730 .teardown.single = rcutree_dying_cpu,
1732 [CPUHP_AP_SMPCFD_DYING] = {
1733 .name = "smpcfd:dying",
1734 .startup.single = NULL,
1735 .teardown.single = smpcfd_dying_cpu,
1737 /* Entry state on starting. Interrupts enabled from here on. Transient
1738 * state for synchronsization */
1739 [CPUHP_AP_ONLINE] = {
1740 .name = "ap:online",
1743 * Handled on control processor until the plugged processor manages
1746 [CPUHP_TEARDOWN_CPU] = {
1747 .name = "cpu:teardown",
1748 .startup.single = NULL,
1749 .teardown.single = takedown_cpu,
1753 [CPUHP_AP_SCHED_WAIT_EMPTY] = {
1754 .name = "sched:waitempty",
1755 .startup.single = NULL,
1756 .teardown.single = sched_cpu_wait_empty,
1759 /* Handle smpboot threads park/unpark */
1760 [CPUHP_AP_SMPBOOT_THREADS] = {
1761 .name = "smpboot/threads:online",
1762 .startup.single = smpboot_unpark_threads,
1763 .teardown.single = smpboot_park_threads,
1765 [CPUHP_AP_IRQ_AFFINITY_ONLINE] = {
1766 .name = "irq/affinity:online",
1767 .startup.single = irq_affinity_online_cpu,
1768 .teardown.single = NULL,
1770 [CPUHP_AP_PERF_ONLINE] = {
1771 .name = "perf:online",
1772 .startup.single = perf_event_init_cpu,
1773 .teardown.single = perf_event_exit_cpu,
1775 [CPUHP_AP_WATCHDOG_ONLINE] = {
1776 .name = "lockup_detector:online",
1777 .startup.single = lockup_detector_online_cpu,
1778 .teardown.single = lockup_detector_offline_cpu,
1780 [CPUHP_AP_WORKQUEUE_ONLINE] = {
1781 .name = "workqueue:online",
1782 .startup.single = workqueue_online_cpu,
1783 .teardown.single = workqueue_offline_cpu,
1785 [CPUHP_AP_RCUTREE_ONLINE] = {
1786 .name = "RCU/tree:online",
1787 .startup.single = rcutree_online_cpu,
1788 .teardown.single = rcutree_offline_cpu,
1792 * The dynamically registered state space is here
1796 /* Last state is scheduler control setting the cpu active */
1797 [CPUHP_AP_ACTIVE] = {
1798 .name = "sched:active",
1799 .startup.single = sched_cpu_activate,
1800 .teardown.single = sched_cpu_deactivate,
1804 /* CPU is fully up and running. */
1807 .startup.single = NULL,
1808 .teardown.single = NULL,
1812 /* Sanity check for callbacks */
1813 static int cpuhp_cb_check(enum cpuhp_state state)
1815 if (state <= CPUHP_OFFLINE || state >= CPUHP_ONLINE)
1821 * Returns a free for dynamic slot assignment of the Online state. The states
1822 * are protected by the cpuhp_slot_states mutex and an empty slot is identified
1823 * by having no name assigned.
1825 static int cpuhp_reserve_state(enum cpuhp_state state)
1827 enum cpuhp_state i, end;
1828 struct cpuhp_step *step;
1831 case CPUHP_AP_ONLINE_DYN:
1832 step = cpuhp_hp_states + CPUHP_AP_ONLINE_DYN;
1833 end = CPUHP_AP_ONLINE_DYN_END;
1835 case CPUHP_BP_PREPARE_DYN:
1836 step = cpuhp_hp_states + CPUHP_BP_PREPARE_DYN;
1837 end = CPUHP_BP_PREPARE_DYN_END;
1843 for (i = state; i <= end; i++, step++) {
1847 WARN(1, "No more dynamic states available for CPU hotplug\n");
1851 static int cpuhp_store_callbacks(enum cpuhp_state state, const char *name,
1852 int (*startup)(unsigned int cpu),
1853 int (*teardown)(unsigned int cpu),
1854 bool multi_instance)
1856 /* (Un)Install the callbacks for further cpu hotplug operations */
1857 struct cpuhp_step *sp;
1861 * If name is NULL, then the state gets removed.
1863 * CPUHP_AP_ONLINE_DYN and CPUHP_BP_PREPARE_DYN are handed out on
1864 * the first allocation from these dynamic ranges, so the removal
1865 * would trigger a new allocation and clear the wrong (already
1866 * empty) state, leaving the callbacks of the to be cleared state
1867 * dangling, which causes wreckage on the next hotplug operation.
1869 if (name && (state == CPUHP_AP_ONLINE_DYN ||
1870 state == CPUHP_BP_PREPARE_DYN)) {
1871 ret = cpuhp_reserve_state(state);
1876 sp = cpuhp_get_step(state);
1877 if (name && sp->name)
1880 sp->startup.single = startup;
1881 sp->teardown.single = teardown;
1883 sp->multi_instance = multi_instance;
1884 INIT_HLIST_HEAD(&sp->list);
1888 static void *cpuhp_get_teardown_cb(enum cpuhp_state state)
1890 return cpuhp_get_step(state)->teardown.single;
1894 * Call the startup/teardown function for a step either on the AP or
1895 * on the current CPU.
1897 static int cpuhp_issue_call(int cpu, enum cpuhp_state state, bool bringup,
1898 struct hlist_node *node)
1900 struct cpuhp_step *sp = cpuhp_get_step(state);
1904 * If there's nothing to do, we done.
1905 * Relies on the union for multi_instance.
1907 if (cpuhp_step_empty(bringup, sp))
1910 * The non AP bound callbacks can fail on bringup. On teardown
1911 * e.g. module removal we crash for now.
1914 if (cpuhp_is_ap_state(state))
1915 ret = cpuhp_invoke_ap_callback(cpu, state, bringup, node);
1917 ret = cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
1919 ret = cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
1921 BUG_ON(ret && !bringup);
1926 * Called from __cpuhp_setup_state on a recoverable failure.
1928 * Note: The teardown callbacks for rollback are not allowed to fail!
1930 static void cpuhp_rollback_install(int failedcpu, enum cpuhp_state state,
1931 struct hlist_node *node)
1935 /* Roll back the already executed steps on the other cpus */
1936 for_each_present_cpu(cpu) {
1937 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1938 int cpustate = st->state;
1940 if (cpu >= failedcpu)
1943 /* Did we invoke the startup call on that cpu ? */
1944 if (cpustate >= state)
1945 cpuhp_issue_call(cpu, state, false, node);
1949 int __cpuhp_state_add_instance_cpuslocked(enum cpuhp_state state,
1950 struct hlist_node *node,
1953 struct cpuhp_step *sp;
1957 lockdep_assert_cpus_held();
1959 sp = cpuhp_get_step(state);
1960 if (sp->multi_instance == false)
1963 mutex_lock(&cpuhp_state_mutex);
1965 if (!invoke || !sp->startup.multi)
1969 * Try to call the startup callback for each present cpu
1970 * depending on the hotplug state of the cpu.
1972 for_each_present_cpu(cpu) {
1973 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1974 int cpustate = st->state;
1976 if (cpustate < state)
1979 ret = cpuhp_issue_call(cpu, state, true, node);
1981 if (sp->teardown.multi)
1982 cpuhp_rollback_install(cpu, state, node);
1988 hlist_add_head(node, &sp->list);
1990 mutex_unlock(&cpuhp_state_mutex);
1994 int __cpuhp_state_add_instance(enum cpuhp_state state, struct hlist_node *node,
2000 ret = __cpuhp_state_add_instance_cpuslocked(state, node, invoke);
2004 EXPORT_SYMBOL_GPL(__cpuhp_state_add_instance);
2007 * __cpuhp_setup_state_cpuslocked - Setup the callbacks for an hotplug machine state
2008 * @state: The state to setup
2009 * @name: Name of the step
2010 * @invoke: If true, the startup function is invoked for cpus where
2011 * cpu state >= @state
2012 * @startup: startup callback function
2013 * @teardown: teardown callback function
2014 * @multi_instance: State is set up for multiple instances which get
2017 * The caller needs to hold cpus read locked while calling this function.
2020 * Positive state number if @state is CPUHP_AP_ONLINE_DYN;
2021 * 0 for all other states
2022 * On failure: proper (negative) error code
2024 int __cpuhp_setup_state_cpuslocked(enum cpuhp_state state,
2025 const char *name, bool invoke,
2026 int (*startup)(unsigned int cpu),
2027 int (*teardown)(unsigned int cpu),
2028 bool multi_instance)
2033 lockdep_assert_cpus_held();
2035 if (cpuhp_cb_check(state) || !name)
2038 mutex_lock(&cpuhp_state_mutex);
2040 ret = cpuhp_store_callbacks(state, name, startup, teardown,
2043 dynstate = state == CPUHP_AP_ONLINE_DYN;
2044 if (ret > 0 && dynstate) {
2049 if (ret || !invoke || !startup)
2053 * Try to call the startup callback for each present cpu
2054 * depending on the hotplug state of the cpu.
2056 for_each_present_cpu(cpu) {
2057 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
2058 int cpustate = st->state;
2060 if (cpustate < state)
2063 ret = cpuhp_issue_call(cpu, state, true, NULL);
2066 cpuhp_rollback_install(cpu, state, NULL);
2067 cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
2072 mutex_unlock(&cpuhp_state_mutex);
2074 * If the requested state is CPUHP_AP_ONLINE_DYN, return the
2075 * dynamically allocated state in case of success.
2077 if (!ret && dynstate)
2081 EXPORT_SYMBOL(__cpuhp_setup_state_cpuslocked);
2083 int __cpuhp_setup_state(enum cpuhp_state state,
2084 const char *name, bool invoke,
2085 int (*startup)(unsigned int cpu),
2086 int (*teardown)(unsigned int cpu),
2087 bool multi_instance)
2092 ret = __cpuhp_setup_state_cpuslocked(state, name, invoke, startup,
2093 teardown, multi_instance);
2097 EXPORT_SYMBOL(__cpuhp_setup_state);
2099 int __cpuhp_state_remove_instance(enum cpuhp_state state,
2100 struct hlist_node *node, bool invoke)
2102 struct cpuhp_step *sp = cpuhp_get_step(state);
2105 BUG_ON(cpuhp_cb_check(state));
2107 if (!sp->multi_instance)
2111 mutex_lock(&cpuhp_state_mutex);
2113 if (!invoke || !cpuhp_get_teardown_cb(state))
2116 * Call the teardown callback for each present cpu depending
2117 * on the hotplug state of the cpu. This function is not
2118 * allowed to fail currently!
2120 for_each_present_cpu(cpu) {
2121 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
2122 int cpustate = st->state;
2124 if (cpustate >= state)
2125 cpuhp_issue_call(cpu, state, false, node);
2130 mutex_unlock(&cpuhp_state_mutex);
2135 EXPORT_SYMBOL_GPL(__cpuhp_state_remove_instance);
2138 * __cpuhp_remove_state_cpuslocked - Remove the callbacks for an hotplug machine state
2139 * @state: The state to remove
2140 * @invoke: If true, the teardown function is invoked for cpus where
2141 * cpu state >= @state
2143 * The caller needs to hold cpus read locked while calling this function.
2144 * The teardown callback is currently not allowed to fail. Think
2145 * about module removal!
2147 void __cpuhp_remove_state_cpuslocked(enum cpuhp_state state, bool invoke)
2149 struct cpuhp_step *sp = cpuhp_get_step(state);
2152 BUG_ON(cpuhp_cb_check(state));
2154 lockdep_assert_cpus_held();
2156 mutex_lock(&cpuhp_state_mutex);
2157 if (sp->multi_instance) {
2158 WARN(!hlist_empty(&sp->list),
2159 "Error: Removing state %d which has instances left.\n",
2164 if (!invoke || !cpuhp_get_teardown_cb(state))
2168 * Call the teardown callback for each present cpu depending
2169 * on the hotplug state of the cpu. This function is not
2170 * allowed to fail currently!
2172 for_each_present_cpu(cpu) {
2173 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
2174 int cpustate = st->state;
2176 if (cpustate >= state)
2177 cpuhp_issue_call(cpu, state, false, NULL);
2180 cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
2181 mutex_unlock(&cpuhp_state_mutex);
2183 EXPORT_SYMBOL(__cpuhp_remove_state_cpuslocked);
2185 void __cpuhp_remove_state(enum cpuhp_state state, bool invoke)
2188 __cpuhp_remove_state_cpuslocked(state, invoke);
2191 EXPORT_SYMBOL(__cpuhp_remove_state);
2193 #ifdef CONFIG_HOTPLUG_SMT
2194 static void cpuhp_offline_cpu_device(unsigned int cpu)
2196 struct device *dev = get_cpu_device(cpu);
2198 dev->offline = true;
2199 /* Tell user space about the state change */
2200 kobject_uevent(&dev->kobj, KOBJ_OFFLINE);
2203 static void cpuhp_online_cpu_device(unsigned int cpu)
2205 struct device *dev = get_cpu_device(cpu);
2207 dev->offline = false;
2208 /* Tell user space about the state change */
2209 kobject_uevent(&dev->kobj, KOBJ_ONLINE);
2212 int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval)
2216 cpu_maps_update_begin();
2217 for_each_online_cpu(cpu) {
2218 if (topology_is_primary_thread(cpu))
2220 ret = cpu_down_maps_locked(cpu, CPUHP_OFFLINE);
2224 * As this needs to hold the cpu maps lock it's impossible
2225 * to call device_offline() because that ends up calling
2226 * cpu_down() which takes cpu maps lock. cpu maps lock
2227 * needs to be held as this might race against in kernel
2228 * abusers of the hotplug machinery (thermal management).
2230 * So nothing would update device:offline state. That would
2231 * leave the sysfs entry stale and prevent onlining after
2232 * smt control has been changed to 'off' again. This is
2233 * called under the sysfs hotplug lock, so it is properly
2234 * serialized against the regular offline usage.
2236 cpuhp_offline_cpu_device(cpu);
2239 cpu_smt_control = ctrlval;
2240 cpu_maps_update_done();
2244 int cpuhp_smt_enable(void)
2248 cpu_maps_update_begin();
2249 cpu_smt_control = CPU_SMT_ENABLED;
2250 for_each_present_cpu(cpu) {
2251 /* Skip online CPUs and CPUs on offline nodes */
2252 if (cpu_online(cpu) || !node_online(cpu_to_node(cpu)))
2254 ret = _cpu_up(cpu, 0, CPUHP_ONLINE);
2257 /* See comment in cpuhp_smt_disable() */
2258 cpuhp_online_cpu_device(cpu);
2260 cpu_maps_update_done();
2265 #if defined(CONFIG_SYSFS) && defined(CONFIG_HOTPLUG_CPU)
2266 static ssize_t state_show(struct device *dev,
2267 struct device_attribute *attr, char *buf)
2269 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2271 return sprintf(buf, "%d\n", st->state);
2273 static DEVICE_ATTR_RO(state);
2275 static ssize_t target_store(struct device *dev, struct device_attribute *attr,
2276 const char *buf, size_t count)
2278 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2279 struct cpuhp_step *sp;
2282 ret = kstrtoint(buf, 10, &target);
2286 #ifdef CONFIG_CPU_HOTPLUG_STATE_CONTROL
2287 if (target < CPUHP_OFFLINE || target > CPUHP_ONLINE)
2290 if (target != CPUHP_OFFLINE && target != CPUHP_ONLINE)
2294 ret = lock_device_hotplug_sysfs();
2298 mutex_lock(&cpuhp_state_mutex);
2299 sp = cpuhp_get_step(target);
2300 ret = !sp->name || sp->cant_stop ? -EINVAL : 0;
2301 mutex_unlock(&cpuhp_state_mutex);
2305 if (st->state < target)
2306 ret = cpu_up(dev->id, target);
2308 ret = cpu_down(dev->id, target);
2310 unlock_device_hotplug();
2311 return ret ? ret : count;
2314 static ssize_t target_show(struct device *dev,
2315 struct device_attribute *attr, char *buf)
2317 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2319 return sprintf(buf, "%d\n", st->target);
2321 static DEVICE_ATTR_RW(target);
2323 static ssize_t fail_store(struct device *dev, struct device_attribute *attr,
2324 const char *buf, size_t count)
2326 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2327 struct cpuhp_step *sp;
2330 ret = kstrtoint(buf, 10, &fail);
2334 if (fail == CPUHP_INVALID) {
2339 if (fail < CPUHP_OFFLINE || fail > CPUHP_ONLINE)
2343 * Cannot fail STARTING/DYING callbacks.
2345 if (cpuhp_is_atomic_state(fail))
2349 * DEAD callbacks cannot fail...
2350 * ... neither can CPUHP_BRINGUP_CPU during hotunplug. The latter
2351 * triggering STARTING callbacks, a failure in this state would
2354 if (fail <= CPUHP_BRINGUP_CPU && st->state > CPUHP_BRINGUP_CPU)
2358 * Cannot fail anything that doesn't have callbacks.
2360 mutex_lock(&cpuhp_state_mutex);
2361 sp = cpuhp_get_step(fail);
2362 if (!sp->startup.single && !sp->teardown.single)
2364 mutex_unlock(&cpuhp_state_mutex);
2373 static ssize_t fail_show(struct device *dev,
2374 struct device_attribute *attr, char *buf)
2376 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2378 return sprintf(buf, "%d\n", st->fail);
2381 static DEVICE_ATTR_RW(fail);
2383 static struct attribute *cpuhp_cpu_attrs[] = {
2384 &dev_attr_state.attr,
2385 &dev_attr_target.attr,
2386 &dev_attr_fail.attr,
2390 static const struct attribute_group cpuhp_cpu_attr_group = {
2391 .attrs = cpuhp_cpu_attrs,
2396 static ssize_t states_show(struct device *dev,
2397 struct device_attribute *attr, char *buf)
2399 ssize_t cur, res = 0;
2402 mutex_lock(&cpuhp_state_mutex);
2403 for (i = CPUHP_OFFLINE; i <= CPUHP_ONLINE; i++) {
2404 struct cpuhp_step *sp = cpuhp_get_step(i);
2407 cur = sprintf(buf, "%3d: %s\n", i, sp->name);
2412 mutex_unlock(&cpuhp_state_mutex);
2415 static DEVICE_ATTR_RO(states);
2417 static struct attribute *cpuhp_cpu_root_attrs[] = {
2418 &dev_attr_states.attr,
2422 static const struct attribute_group cpuhp_cpu_root_attr_group = {
2423 .attrs = cpuhp_cpu_root_attrs,
2428 #ifdef CONFIG_HOTPLUG_SMT
2431 __store_smt_control(struct device *dev, struct device_attribute *attr,
2432 const char *buf, size_t count)
2436 if (sysfs_streq(buf, "on"))
2437 ctrlval = CPU_SMT_ENABLED;
2438 else if (sysfs_streq(buf, "off"))
2439 ctrlval = CPU_SMT_DISABLED;
2440 else if (sysfs_streq(buf, "forceoff"))
2441 ctrlval = CPU_SMT_FORCE_DISABLED;
2445 if (cpu_smt_control == CPU_SMT_FORCE_DISABLED)
2448 if (cpu_smt_control == CPU_SMT_NOT_SUPPORTED)
2451 ret = lock_device_hotplug_sysfs();
2455 if (ctrlval != cpu_smt_control) {
2457 case CPU_SMT_ENABLED:
2458 ret = cpuhp_smt_enable();
2460 case CPU_SMT_DISABLED:
2461 case CPU_SMT_FORCE_DISABLED:
2462 ret = cpuhp_smt_disable(ctrlval);
2467 unlock_device_hotplug();
2468 return ret ? ret : count;
2471 #else /* !CONFIG_HOTPLUG_SMT */
2473 __store_smt_control(struct device *dev, struct device_attribute *attr,
2474 const char *buf, size_t count)
2478 #endif /* CONFIG_HOTPLUG_SMT */
2480 static const char *smt_states[] = {
2481 [CPU_SMT_ENABLED] = "on",
2482 [CPU_SMT_DISABLED] = "off",
2483 [CPU_SMT_FORCE_DISABLED] = "forceoff",
2484 [CPU_SMT_NOT_SUPPORTED] = "notsupported",
2485 [CPU_SMT_NOT_IMPLEMENTED] = "notimplemented",
2488 static ssize_t control_show(struct device *dev,
2489 struct device_attribute *attr, char *buf)
2491 const char *state = smt_states[cpu_smt_control];
2493 return snprintf(buf, PAGE_SIZE - 2, "%s\n", state);
2496 static ssize_t control_store(struct device *dev, struct device_attribute *attr,
2497 const char *buf, size_t count)
2499 return __store_smt_control(dev, attr, buf, count);
2501 static DEVICE_ATTR_RW(control);
2503 static ssize_t active_show(struct device *dev,
2504 struct device_attribute *attr, char *buf)
2506 return snprintf(buf, PAGE_SIZE - 2, "%d\n", sched_smt_active());
2508 static DEVICE_ATTR_RO(active);
2510 static struct attribute *cpuhp_smt_attrs[] = {
2511 &dev_attr_control.attr,
2512 &dev_attr_active.attr,
2516 static const struct attribute_group cpuhp_smt_attr_group = {
2517 .attrs = cpuhp_smt_attrs,
2522 static int __init cpu_smt_sysfs_init(void)
2524 return sysfs_create_group(&cpu_subsys.dev_root->kobj,
2525 &cpuhp_smt_attr_group);
2528 static int __init cpuhp_sysfs_init(void)
2532 ret = cpu_smt_sysfs_init();
2536 ret = sysfs_create_group(&cpu_subsys.dev_root->kobj,
2537 &cpuhp_cpu_root_attr_group);
2541 for_each_possible_cpu(cpu) {
2542 struct device *dev = get_cpu_device(cpu);
2546 ret = sysfs_create_group(&dev->kobj, &cpuhp_cpu_attr_group);
2552 device_initcall(cpuhp_sysfs_init);
2553 #endif /* CONFIG_SYSFS && CONFIG_HOTPLUG_CPU */
2556 * cpu_bit_bitmap[] is a special, "compressed" data structure that
2557 * represents all NR_CPUS bits binary values of 1<<nr.
2559 * It is used by cpumask_of() to get a constant address to a CPU
2560 * mask value that has a single bit set only.
2563 /* cpu_bit_bitmap[0] is empty - so we can back into it */
2564 #define MASK_DECLARE_1(x) [x+1][0] = (1UL << (x))
2565 #define MASK_DECLARE_2(x) MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
2566 #define MASK_DECLARE_4(x) MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
2567 #define MASK_DECLARE_8(x) MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
2569 const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
2571 MASK_DECLARE_8(0), MASK_DECLARE_8(8),
2572 MASK_DECLARE_8(16), MASK_DECLARE_8(24),
2573 #if BITS_PER_LONG > 32
2574 MASK_DECLARE_8(32), MASK_DECLARE_8(40),
2575 MASK_DECLARE_8(48), MASK_DECLARE_8(56),
2578 EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
2580 const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
2581 EXPORT_SYMBOL(cpu_all_bits);
2583 #ifdef CONFIG_INIT_ALL_POSSIBLE
2584 struct cpumask __cpu_possible_mask __read_mostly
2587 struct cpumask __cpu_possible_mask __read_mostly;
2589 EXPORT_SYMBOL(__cpu_possible_mask);
2591 struct cpumask __cpu_online_mask __read_mostly;
2592 EXPORT_SYMBOL(__cpu_online_mask);
2594 struct cpumask __cpu_present_mask __read_mostly;
2595 EXPORT_SYMBOL(__cpu_present_mask);
2597 struct cpumask __cpu_active_mask __read_mostly;
2598 EXPORT_SYMBOL(__cpu_active_mask);
2600 struct cpumask __cpu_dying_mask __read_mostly;
2601 EXPORT_SYMBOL(__cpu_dying_mask);
2603 atomic_t __num_online_cpus __read_mostly;
2604 EXPORT_SYMBOL(__num_online_cpus);
2606 void init_cpu_present(const struct cpumask *src)
2608 cpumask_copy(&__cpu_present_mask, src);
2611 void init_cpu_possible(const struct cpumask *src)
2613 cpumask_copy(&__cpu_possible_mask, src);
2616 void init_cpu_online(const struct cpumask *src)
2618 cpumask_copy(&__cpu_online_mask, src);
2621 void set_cpu_online(unsigned int cpu, bool online)
2624 * atomic_inc/dec() is required to handle the horrid abuse of this
2625 * function by the reboot and kexec code which invoke it from
2626 * IPI/NMI broadcasts when shutting down CPUs. Invocation from
2627 * regular CPU hotplug is properly serialized.
2629 * Note, that the fact that __num_online_cpus is of type atomic_t
2630 * does not protect readers which are not serialized against
2631 * concurrent hotplug operations.
2634 if (!cpumask_test_and_set_cpu(cpu, &__cpu_online_mask))
2635 atomic_inc(&__num_online_cpus);
2637 if (cpumask_test_and_clear_cpu(cpu, &__cpu_online_mask))
2638 atomic_dec(&__num_online_cpus);
2643 * Activate the first processor.
2645 void __init boot_cpu_init(void)
2647 int cpu = smp_processor_id();
2649 /* Mark the boot cpu "present", "online" etc for SMP and UP case */
2650 set_cpu_online(cpu, true);
2651 set_cpu_active(cpu, true);
2652 set_cpu_present(cpu, true);
2653 set_cpu_possible(cpu, true);
2656 __boot_cpu_id = cpu;
2661 * Must be called _AFTER_ setting up the per_cpu areas
2663 void __init boot_cpu_hotplug_init(void)
2666 cpumask_set_cpu(smp_processor_id(), &cpus_booted_once_mask);
2668 this_cpu_write(cpuhp_state.state, CPUHP_ONLINE);
2672 * These are used for a global "mitigations=" cmdline option for toggling
2673 * optional CPU mitigations.
2675 enum cpu_mitigations {
2676 CPU_MITIGATIONS_OFF,
2677 CPU_MITIGATIONS_AUTO,
2678 CPU_MITIGATIONS_AUTO_NOSMT,
2681 static enum cpu_mitigations cpu_mitigations __ro_after_init =
2682 CPU_MITIGATIONS_AUTO;
2684 static int __init mitigations_parse_cmdline(char *arg)
2686 if (!strcmp(arg, "off"))
2687 cpu_mitigations = CPU_MITIGATIONS_OFF;
2688 else if (!strcmp(arg, "auto"))
2689 cpu_mitigations = CPU_MITIGATIONS_AUTO;
2690 else if (!strcmp(arg, "auto,nosmt"))
2691 cpu_mitigations = CPU_MITIGATIONS_AUTO_NOSMT;
2693 pr_crit("Unsupported mitigations=%s, system may still be vulnerable\n",
2698 early_param("mitigations", mitigations_parse_cmdline);
2700 /* mitigations=off */
2701 bool cpu_mitigations_off(void)
2703 return cpu_mitigations == CPU_MITIGATIONS_OFF;
2705 EXPORT_SYMBOL_GPL(cpu_mitigations_off);
2707 /* mitigations=auto,nosmt */
2708 bool cpu_mitigations_auto_nosmt(void)
2710 return cpu_mitigations == CPU_MITIGATIONS_AUTO_NOSMT;
2712 EXPORT_SYMBOL_GPL(cpu_mitigations_auto_nosmt);