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/percpu-rwsem.h>
35 #include <linux/cpuset.h>
37 #include <trace/events/power.h>
38 #define CREATE_TRACE_POINTS
39 #include <trace/events/cpuhp.h>
44 * cpuhp_cpu_state - Per cpu hotplug state storage
45 * @state: The current cpu state
46 * @target: The target state
47 * @thread: Pointer to the hotplug thread
48 * @should_run: Thread should execute
49 * @rollback: Perform a rollback
50 * @single: Single callback invocation
51 * @bringup: Single callback bringup or teardown selector
52 * @cb_state: The state for a single callback (install/uninstall)
53 * @result: Result of the operation
54 * @done_up: Signal completion to the issuer of the task for cpu-up
55 * @done_down: Signal completion to the issuer of the task for cpu-down
57 struct cpuhp_cpu_state {
58 enum cpuhp_state state;
59 enum cpuhp_state target;
60 enum cpuhp_state fail;
62 struct task_struct *thread;
67 struct hlist_node *node;
68 struct hlist_node *last;
69 enum cpuhp_state cb_state;
71 struct completion done_up;
72 struct completion done_down;
76 static DEFINE_PER_CPU(struct cpuhp_cpu_state, cpuhp_state) = {
77 .fail = CPUHP_INVALID,
81 cpumask_t cpus_booted_once_mask;
84 #if defined(CONFIG_LOCKDEP) && defined(CONFIG_SMP)
85 static struct lockdep_map cpuhp_state_up_map =
86 STATIC_LOCKDEP_MAP_INIT("cpuhp_state-up", &cpuhp_state_up_map);
87 static struct lockdep_map cpuhp_state_down_map =
88 STATIC_LOCKDEP_MAP_INIT("cpuhp_state-down", &cpuhp_state_down_map);
91 static inline void cpuhp_lock_acquire(bool bringup)
93 lock_map_acquire(bringup ? &cpuhp_state_up_map : &cpuhp_state_down_map);
96 static inline void cpuhp_lock_release(bool bringup)
98 lock_map_release(bringup ? &cpuhp_state_up_map : &cpuhp_state_down_map);
102 static inline void cpuhp_lock_acquire(bool bringup) { }
103 static inline void cpuhp_lock_release(bool bringup) { }
108 * cpuhp_step - Hotplug state machine step
109 * @name: Name of the step
110 * @startup: Startup function of the step
111 * @teardown: Teardown function of the step
112 * @cant_stop: Bringup/teardown can't be stopped at this step
117 int (*single)(unsigned int cpu);
118 int (*multi)(unsigned int cpu,
119 struct hlist_node *node);
122 int (*single)(unsigned int cpu);
123 int (*multi)(unsigned int cpu,
124 struct hlist_node *node);
126 struct hlist_head list;
131 static DEFINE_MUTEX(cpuhp_state_mutex);
132 static struct cpuhp_step cpuhp_hp_states[];
134 static struct cpuhp_step *cpuhp_get_step(enum cpuhp_state state)
136 return cpuhp_hp_states + state;
140 * cpuhp_invoke_callback _ Invoke the callbacks for a given state
141 * @cpu: The cpu for which the callback should be invoked
142 * @state: The state to do callbacks for
143 * @bringup: True if the bringup callback should be invoked
144 * @node: For multi-instance, do a single entry callback for install/remove
145 * @lastp: For multi-instance rollback, remember how far we got
147 * Called from cpu hotplug and from the state register machinery.
149 static int cpuhp_invoke_callback(unsigned int cpu, enum cpuhp_state state,
150 bool bringup, struct hlist_node *node,
151 struct hlist_node **lastp)
153 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
154 struct cpuhp_step *step = cpuhp_get_step(state);
155 int (*cbm)(unsigned int cpu, struct hlist_node *node);
156 int (*cb)(unsigned int cpu);
159 if (st->fail == state) {
160 st->fail = CPUHP_INVALID;
162 if (!(bringup ? step->startup.single : step->teardown.single))
168 if (!step->multi_instance) {
169 WARN_ON_ONCE(lastp && *lastp);
170 cb = bringup ? step->startup.single : step->teardown.single;
173 trace_cpuhp_enter(cpu, st->target, state, cb);
175 trace_cpuhp_exit(cpu, st->state, state, ret);
178 cbm = bringup ? step->startup.multi : step->teardown.multi;
182 /* Single invocation for instance add/remove */
184 WARN_ON_ONCE(lastp && *lastp);
185 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
186 ret = cbm(cpu, node);
187 trace_cpuhp_exit(cpu, st->state, state, ret);
191 /* State transition. Invoke on all instances */
193 hlist_for_each(node, &step->list) {
194 if (lastp && node == *lastp)
197 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
198 ret = cbm(cpu, node);
199 trace_cpuhp_exit(cpu, st->state, state, ret);
213 /* Rollback the instances if one failed */
214 cbm = !bringup ? step->startup.multi : step->teardown.multi;
218 hlist_for_each(node, &step->list) {
222 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
223 ret = cbm(cpu, node);
224 trace_cpuhp_exit(cpu, st->state, state, ret);
226 * Rollback must not fail,
234 static bool cpuhp_is_ap_state(enum cpuhp_state state)
237 * The extra check for CPUHP_TEARDOWN_CPU is only for documentation
238 * purposes as that state is handled explicitly in cpu_down.
240 return state > CPUHP_BRINGUP_CPU && state != CPUHP_TEARDOWN_CPU;
243 static inline void wait_for_ap_thread(struct cpuhp_cpu_state *st, bool bringup)
245 struct completion *done = bringup ? &st->done_up : &st->done_down;
246 wait_for_completion(done);
249 static inline void complete_ap_thread(struct cpuhp_cpu_state *st, bool bringup)
251 struct completion *done = bringup ? &st->done_up : &st->done_down;
256 * The former STARTING/DYING states, ran with IRQs disabled and must not fail.
258 static bool cpuhp_is_atomic_state(enum cpuhp_state state)
260 return CPUHP_AP_IDLE_DEAD <= state && state < CPUHP_AP_ONLINE;
263 /* Serializes the updates to cpu_online_mask, cpu_present_mask */
264 static DEFINE_MUTEX(cpu_add_remove_lock);
265 bool cpuhp_tasks_frozen;
266 EXPORT_SYMBOL_GPL(cpuhp_tasks_frozen);
269 * The following two APIs (cpu_maps_update_begin/done) must be used when
270 * attempting to serialize the updates to cpu_online_mask & cpu_present_mask.
272 void cpu_maps_update_begin(void)
274 mutex_lock(&cpu_add_remove_lock);
277 void cpu_maps_update_done(void)
279 mutex_unlock(&cpu_add_remove_lock);
283 * If set, cpu_up and cpu_down will return -EBUSY and do nothing.
284 * Should always be manipulated under cpu_add_remove_lock
286 static int cpu_hotplug_disabled;
288 #ifdef CONFIG_HOTPLUG_CPU
290 DEFINE_STATIC_PERCPU_RWSEM(cpu_hotplug_lock);
292 void cpus_read_lock(void)
294 percpu_down_read(&cpu_hotplug_lock);
296 EXPORT_SYMBOL_GPL(cpus_read_lock);
298 int cpus_read_trylock(void)
300 return percpu_down_read_trylock(&cpu_hotplug_lock);
302 EXPORT_SYMBOL_GPL(cpus_read_trylock);
304 void cpus_read_unlock(void)
306 percpu_up_read(&cpu_hotplug_lock);
308 EXPORT_SYMBOL_GPL(cpus_read_unlock);
310 void cpus_write_lock(void)
312 percpu_down_write(&cpu_hotplug_lock);
315 void cpus_write_unlock(void)
317 percpu_up_write(&cpu_hotplug_lock);
320 void lockdep_assert_cpus_held(void)
323 * We can't have hotplug operations before userspace starts running,
324 * and some init codepaths will knowingly not take the hotplug lock.
325 * This is all valid, so mute lockdep until it makes sense to report
328 if (system_state < SYSTEM_RUNNING)
331 percpu_rwsem_assert_held(&cpu_hotplug_lock);
334 static void lockdep_acquire_cpus_lock(void)
336 rwsem_acquire(&cpu_hotplug_lock.dep_map, 0, 0, _THIS_IP_);
339 static void lockdep_release_cpus_lock(void)
341 rwsem_release(&cpu_hotplug_lock.dep_map, _THIS_IP_);
345 * Wait for currently running CPU hotplug operations to complete (if any) and
346 * disable future CPU hotplug (from sysfs). The 'cpu_add_remove_lock' protects
347 * the 'cpu_hotplug_disabled' flag. The same lock is also acquired by the
348 * hotplug path before performing hotplug operations. So acquiring that lock
349 * guarantees mutual exclusion from any currently running hotplug operations.
351 void cpu_hotplug_disable(void)
353 cpu_maps_update_begin();
354 cpu_hotplug_disabled++;
355 cpu_maps_update_done();
357 EXPORT_SYMBOL_GPL(cpu_hotplug_disable);
359 static void __cpu_hotplug_enable(void)
361 if (WARN_ONCE(!cpu_hotplug_disabled, "Unbalanced cpu hotplug enable\n"))
363 cpu_hotplug_disabled--;
366 void cpu_hotplug_enable(void)
368 cpu_maps_update_begin();
369 __cpu_hotplug_enable();
370 cpu_maps_update_done();
372 EXPORT_SYMBOL_GPL(cpu_hotplug_enable);
376 static void lockdep_acquire_cpus_lock(void)
380 static void lockdep_release_cpus_lock(void)
384 #endif /* CONFIG_HOTPLUG_CPU */
387 * Architectures that need SMT-specific errata handling during SMT hotplug
388 * should override this.
390 void __weak arch_smt_update(void) { }
392 #ifdef CONFIG_HOTPLUG_SMT
393 enum cpuhp_smt_control cpu_smt_control __read_mostly = CPU_SMT_ENABLED;
395 void __init cpu_smt_disable(bool force)
397 if (!cpu_smt_possible())
401 pr_info("SMT: Force disabled\n");
402 cpu_smt_control = CPU_SMT_FORCE_DISABLED;
404 pr_info("SMT: disabled\n");
405 cpu_smt_control = CPU_SMT_DISABLED;
410 * The decision whether SMT is supported can only be done after the full
411 * CPU identification. Called from architecture code.
413 void __init cpu_smt_check_topology(void)
415 if (!topology_smt_supported())
416 cpu_smt_control = CPU_SMT_NOT_SUPPORTED;
419 static int __init smt_cmdline_disable(char *str)
421 cpu_smt_disable(str && !strcmp(str, "force"));
424 early_param("nosmt", smt_cmdline_disable);
426 static inline bool cpu_smt_allowed(unsigned int cpu)
428 if (cpu_smt_control == CPU_SMT_ENABLED)
431 if (topology_is_primary_thread(cpu))
435 * On x86 it's required to boot all logical CPUs at least once so
436 * that the init code can get a chance to set CR4.MCE on each
437 * CPU. Otherwise, a broadcasted MCE observing CR4.MCE=0b on any
438 * core will shutdown the machine.
440 return !cpumask_test_cpu(cpu, &cpus_booted_once_mask);
443 /* Returns true if SMT is not supported of forcefully (irreversibly) disabled */
444 bool cpu_smt_possible(void)
446 return cpu_smt_control != CPU_SMT_FORCE_DISABLED &&
447 cpu_smt_control != CPU_SMT_NOT_SUPPORTED;
449 EXPORT_SYMBOL_GPL(cpu_smt_possible);
451 static inline bool cpu_smt_allowed(unsigned int cpu) { return true; }
454 static inline enum cpuhp_state
455 cpuhp_set_state(struct cpuhp_cpu_state *st, enum cpuhp_state target)
457 enum cpuhp_state prev_state = st->state;
459 st->rollback = false;
464 st->bringup = st->state < target;
470 cpuhp_reset_state(struct cpuhp_cpu_state *st, enum cpuhp_state prev_state)
475 * If we have st->last we need to undo partial multi_instance of this
476 * state first. Otherwise start undo at the previous state.
485 st->target = prev_state;
486 st->bringup = !st->bringup;
489 /* Regular hotplug invocation of the AP hotplug thread */
490 static void __cpuhp_kick_ap(struct cpuhp_cpu_state *st)
492 if (!st->single && st->state == st->target)
497 * Make sure the above stores are visible before should_run becomes
498 * true. Paired with the mb() above in cpuhp_thread_fun()
501 st->should_run = true;
502 wake_up_process(st->thread);
503 wait_for_ap_thread(st, st->bringup);
506 static int cpuhp_kick_ap(struct cpuhp_cpu_state *st, enum cpuhp_state target)
508 enum cpuhp_state prev_state;
511 prev_state = cpuhp_set_state(st, target);
513 if ((ret = st->result)) {
514 cpuhp_reset_state(st, prev_state);
521 static int bringup_wait_for_ap(unsigned int cpu)
523 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
525 /* Wait for the CPU to reach CPUHP_AP_ONLINE_IDLE */
526 wait_for_ap_thread(st, true);
527 if (WARN_ON_ONCE((!cpu_online(cpu))))
530 /* Unpark the hotplug thread of the target cpu */
531 kthread_unpark(st->thread);
534 * SMT soft disabling on X86 requires to bring the CPU out of the
535 * BIOS 'wait for SIPI' state in order to set the CR4.MCE bit. The
536 * CPU marked itself as booted_once in notify_cpu_starting() so the
537 * cpu_smt_allowed() check will now return false if this is not the
540 if (!cpu_smt_allowed(cpu))
543 if (st->target <= CPUHP_AP_ONLINE_IDLE)
546 return cpuhp_kick_ap(st, st->target);
549 static int bringup_cpu(unsigned int cpu)
551 struct task_struct *idle = idle_thread_get(cpu);
555 * Some architectures have to walk the irq descriptors to
556 * setup the vector space for the cpu which comes online.
557 * Prevent irq alloc/free across the bringup.
561 /* Arch-specific enabling code. */
562 ret = __cpu_up(cpu, idle);
566 return bringup_wait_for_ap(cpu);
569 static int finish_cpu(unsigned int cpu)
571 struct task_struct *idle = idle_thread_get(cpu);
572 struct mm_struct *mm = idle->active_mm;
575 * idle_task_exit() will have switched to &init_mm, now
576 * clean up any remaining active_mm state.
579 idle->active_mm = &init_mm;
585 * Hotplug state machine related functions
588 static void undo_cpu_up(unsigned int cpu, struct cpuhp_cpu_state *st)
590 for (st->state--; st->state > st->target; st->state--)
591 cpuhp_invoke_callback(cpu, st->state, false, NULL, NULL);
594 static inline bool can_rollback_cpu(struct cpuhp_cpu_state *st)
596 if (IS_ENABLED(CONFIG_HOTPLUG_CPU))
599 * When CPU hotplug is disabled, then taking the CPU down is not
600 * possible because takedown_cpu() and the architecture and
601 * subsystem specific mechanisms are not available. So the CPU
602 * which would be completely unplugged again needs to stay around
603 * in the current state.
605 return st->state <= CPUHP_BRINGUP_CPU;
608 static int cpuhp_up_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
609 enum cpuhp_state target)
611 enum cpuhp_state prev_state = st->state;
614 while (st->state < target) {
616 ret = cpuhp_invoke_callback(cpu, st->state, true, NULL, NULL);
618 if (can_rollback_cpu(st)) {
619 st->target = prev_state;
620 undo_cpu_up(cpu, st);
629 * The cpu hotplug threads manage the bringup and teardown of the cpus
631 static void cpuhp_create(unsigned int cpu)
633 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
635 init_completion(&st->done_up);
636 init_completion(&st->done_down);
639 static int cpuhp_should_run(unsigned int cpu)
641 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
643 return st->should_run;
647 * Execute teardown/startup callbacks on the plugged cpu. Also used to invoke
648 * callbacks when a state gets [un]installed at runtime.
650 * Each invocation of this function by the smpboot thread does a single AP
653 * It has 3 modes of operation:
654 * - single: runs st->cb_state
655 * - up: runs ++st->state, while st->state < st->target
656 * - down: runs st->state--, while st->state > st->target
658 * When complete or on error, should_run is cleared and the completion is fired.
660 static void cpuhp_thread_fun(unsigned int cpu)
662 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
663 bool bringup = st->bringup;
664 enum cpuhp_state state;
666 if (WARN_ON_ONCE(!st->should_run))
670 * ACQUIRE for the cpuhp_should_run() load of ->should_run. Ensures
671 * that if we see ->should_run we also see the rest of the state.
676 * The BP holds the hotplug lock, but we're now running on the AP,
677 * ensure that anybody asserting the lock is held, will actually find
680 lockdep_acquire_cpus_lock();
681 cpuhp_lock_acquire(bringup);
684 state = st->cb_state;
685 st->should_run = false;
690 st->should_run = (st->state < st->target);
691 WARN_ON_ONCE(st->state > st->target);
695 st->should_run = (st->state > st->target);
696 WARN_ON_ONCE(st->state < st->target);
700 WARN_ON_ONCE(!cpuhp_is_ap_state(state));
702 if (cpuhp_is_atomic_state(state)) {
704 st->result = cpuhp_invoke_callback(cpu, state, bringup, st->node, &st->last);
708 * STARTING/DYING must not fail!
710 WARN_ON_ONCE(st->result);
712 st->result = cpuhp_invoke_callback(cpu, state, bringup, st->node, &st->last);
717 * If we fail on a rollback, we're up a creek without no
718 * paddle, no way forward, no way back. We loose, thanks for
721 WARN_ON_ONCE(st->rollback);
722 st->should_run = false;
725 cpuhp_lock_release(bringup);
726 lockdep_release_cpus_lock();
729 complete_ap_thread(st, bringup);
732 /* Invoke a single callback on a remote cpu */
734 cpuhp_invoke_ap_callback(int cpu, enum cpuhp_state state, bool bringup,
735 struct hlist_node *node)
737 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
740 if (!cpu_online(cpu))
743 cpuhp_lock_acquire(false);
744 cpuhp_lock_release(false);
746 cpuhp_lock_acquire(true);
747 cpuhp_lock_release(true);
750 * If we are up and running, use the hotplug thread. For early calls
751 * we invoke the thread function directly.
754 return cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
756 st->rollback = false;
760 st->bringup = bringup;
761 st->cb_state = state;
767 * If we failed and did a partial, do a rollback.
769 if ((ret = st->result) && st->last) {
771 st->bringup = !bringup;
777 * Clean up the leftovers so the next hotplug operation wont use stale
780 st->node = st->last = NULL;
784 static int cpuhp_kick_ap_work(unsigned int cpu)
786 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
787 enum cpuhp_state prev_state = st->state;
790 cpuhp_lock_acquire(false);
791 cpuhp_lock_release(false);
793 cpuhp_lock_acquire(true);
794 cpuhp_lock_release(true);
796 trace_cpuhp_enter(cpu, st->target, prev_state, cpuhp_kick_ap_work);
797 ret = cpuhp_kick_ap(st, st->target);
798 trace_cpuhp_exit(cpu, st->state, prev_state, ret);
803 static struct smp_hotplug_thread cpuhp_threads = {
804 .store = &cpuhp_state.thread,
805 .create = &cpuhp_create,
806 .thread_should_run = cpuhp_should_run,
807 .thread_fn = cpuhp_thread_fun,
808 .thread_comm = "cpuhp/%u",
812 void __init cpuhp_threads_init(void)
814 BUG_ON(smpboot_register_percpu_thread(&cpuhp_threads));
815 kthread_unpark(this_cpu_read(cpuhp_state.thread));
820 * Serialize hotplug trainwrecks outside of the cpu_hotplug_lock
823 * The operation is still serialized against concurrent CPU hotplug via
824 * cpu_add_remove_lock, i.e. CPU map protection. But it is _not_
825 * serialized against other hotplug related activity like adding or
826 * removing of state callbacks and state instances, which invoke either the
827 * startup or the teardown callback of the affected state.
829 * This is required for subsystems which are unfixable vs. CPU hotplug and
830 * evade lock inversion problems by scheduling work which has to be
831 * completed _before_ cpu_up()/_cpu_down() returns.
833 * Don't even think about adding anything to this for any new code or even
834 * drivers. It's only purpose is to keep existing lock order trainwrecks
837 * For cpu_down() there might be valid reasons to finish cleanups which are
838 * not required to be done under cpu_hotplug_lock, but that's a different
839 * story and would be not invoked via this.
841 static void cpu_up_down_serialize_trainwrecks(bool tasks_frozen)
844 * cpusets delegate hotplug operations to a worker to "solve" the
845 * lock order problems. Wait for the worker, but only if tasks are
846 * _not_ frozen (suspend, hibernate) as that would wait forever.
848 * The wait is required because otherwise the hotplug operation
849 * returns with inconsistent state, which could even be observed in
850 * user space when a new CPU is brought up. The CPU plug uevent
851 * would be delivered and user space reacting on it would fail to
852 * move tasks to the newly plugged CPU up to the point where the
853 * work has finished because up to that point the newly plugged CPU
854 * is not assignable in cpusets/cgroups. On unplug that's not
855 * necessarily a visible issue, but it is still inconsistent state,
856 * which is the real problem which needs to be "fixed". This can't
857 * prevent the transient state between scheduling the work and
858 * returning from waiting for it.
861 cpuset_wait_for_hotplug();
864 #ifdef CONFIG_HOTPLUG_CPU
865 #ifndef arch_clear_mm_cpumask_cpu
866 #define arch_clear_mm_cpumask_cpu(cpu, mm) cpumask_clear_cpu(cpu, mm_cpumask(mm))
870 * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
873 * This function walks all processes, finds a valid mm struct for each one and
874 * then clears a corresponding bit in mm's cpumask. While this all sounds
875 * trivial, there are various non-obvious corner cases, which this function
876 * tries to solve in a safe manner.
878 * Also note that the function uses a somewhat relaxed locking scheme, so it may
879 * be called only for an already offlined CPU.
881 void clear_tasks_mm_cpumask(int cpu)
883 struct task_struct *p;
886 * This function is called after the cpu is taken down and marked
887 * offline, so its not like new tasks will ever get this cpu set in
888 * their mm mask. -- Peter Zijlstra
889 * Thus, we may use rcu_read_lock() here, instead of grabbing
890 * full-fledged tasklist_lock.
892 WARN_ON(cpu_online(cpu));
894 for_each_process(p) {
895 struct task_struct *t;
898 * Main thread might exit, but other threads may still have
899 * a valid mm. Find one.
901 t = find_lock_task_mm(p);
904 arch_clear_mm_cpumask_cpu(cpu, t->mm);
910 /* Take this CPU down. */
911 static int take_cpu_down(void *_param)
913 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
914 enum cpuhp_state target = max((int)st->target, CPUHP_AP_OFFLINE);
915 int err, cpu = smp_processor_id();
918 /* Ensure this CPU doesn't handle any more interrupts. */
919 err = __cpu_disable();
924 * We get here while we are in CPUHP_TEARDOWN_CPU state and we must not
925 * do this step again.
927 WARN_ON(st->state != CPUHP_TEARDOWN_CPU);
929 /* Invoke the former CPU_DYING callbacks */
930 for (; st->state > target; st->state--) {
931 ret = cpuhp_invoke_callback(cpu, st->state, false, NULL, NULL);
933 * DYING must not fail!
938 /* Give up timekeeping duties */
939 tick_handover_do_timer();
940 /* Remove CPU from timer broadcasting */
941 tick_offline_cpu(cpu);
942 /* Park the stopper thread */
943 stop_machine_park(cpu);
947 static int takedown_cpu(unsigned int cpu)
949 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
952 /* Park the smpboot threads */
953 kthread_park(per_cpu_ptr(&cpuhp_state, cpu)->thread);
956 * Prevent irq alloc/free while the dying cpu reorganizes the
957 * interrupt affinities.
962 * So now all preempt/rcu users must observe !cpu_active().
964 err = stop_machine_cpuslocked(take_cpu_down, NULL, cpumask_of(cpu));
966 /* CPU refused to die */
968 /* Unpark the hotplug thread so we can rollback there */
969 kthread_unpark(per_cpu_ptr(&cpuhp_state, cpu)->thread);
972 BUG_ON(cpu_online(cpu));
975 * The teardown callback for CPUHP_AP_SCHED_STARTING will have removed
976 * all runnable tasks from the CPU, there's only the idle task left now
977 * that the migration thread is done doing the stop_machine thing.
979 * Wait for the stop thread to go away.
981 wait_for_ap_thread(st, false);
982 BUG_ON(st->state != CPUHP_AP_IDLE_DEAD);
984 /* Interrupts are moved away from the dying cpu, reenable alloc/free */
987 hotplug_cpu__broadcast_tick_pull(cpu);
988 /* This actually kills the CPU. */
991 tick_cleanup_dead_cpu(cpu);
992 rcutree_migrate_callbacks(cpu);
996 static void cpuhp_complete_idle_dead(void *arg)
998 struct cpuhp_cpu_state *st = arg;
1000 complete_ap_thread(st, false);
1003 void cpuhp_report_idle_dead(void)
1005 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
1007 BUG_ON(st->state != CPUHP_AP_OFFLINE);
1008 rcu_report_dead(smp_processor_id());
1009 st->state = CPUHP_AP_IDLE_DEAD;
1011 * We cannot call complete after rcu_report_dead() so we delegate it
1014 smp_call_function_single(cpumask_first(cpu_online_mask),
1015 cpuhp_complete_idle_dead, st, 0);
1018 static void undo_cpu_down(unsigned int cpu, struct cpuhp_cpu_state *st)
1020 for (st->state++; st->state < st->target; st->state++)
1021 cpuhp_invoke_callback(cpu, st->state, true, NULL, NULL);
1024 static int cpuhp_down_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
1025 enum cpuhp_state target)
1027 enum cpuhp_state prev_state = st->state;
1030 for (; st->state > target; st->state--) {
1031 ret = cpuhp_invoke_callback(cpu, st->state, false, NULL, NULL);
1033 st->target = prev_state;
1034 if (st->state < prev_state)
1035 undo_cpu_down(cpu, st);
1042 /* Requires cpu_add_remove_lock to be held */
1043 static int __ref _cpu_down(unsigned int cpu, int tasks_frozen,
1044 enum cpuhp_state target)
1046 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1047 int prev_state, ret = 0;
1049 if (num_online_cpus() == 1)
1052 if (!cpu_present(cpu))
1057 cpuhp_tasks_frozen = tasks_frozen;
1059 prev_state = cpuhp_set_state(st, target);
1061 * If the current CPU state is in the range of the AP hotplug thread,
1062 * then we need to kick the thread.
1064 if (st->state > CPUHP_TEARDOWN_CPU) {
1065 st->target = max((int)target, CPUHP_TEARDOWN_CPU);
1066 ret = cpuhp_kick_ap_work(cpu);
1068 * The AP side has done the error rollback already. Just
1069 * return the error code..
1075 * We might have stopped still in the range of the AP hotplug
1076 * thread. Nothing to do anymore.
1078 if (st->state > CPUHP_TEARDOWN_CPU)
1081 st->target = target;
1084 * The AP brought itself down to CPUHP_TEARDOWN_CPU. So we need
1085 * to do the further cleanups.
1087 ret = cpuhp_down_callbacks(cpu, st, target);
1088 if (ret && st->state == CPUHP_TEARDOWN_CPU && st->state < prev_state) {
1089 cpuhp_reset_state(st, prev_state);
1090 __cpuhp_kick_ap(st);
1094 cpus_write_unlock();
1096 * Do post unplug cleanup. This is still protected against
1097 * concurrent CPU hotplug via cpu_add_remove_lock.
1099 lockup_detector_cleanup();
1101 cpu_up_down_serialize_trainwrecks(tasks_frozen);
1105 static int cpu_down_maps_locked(unsigned int cpu, enum cpuhp_state target)
1107 if (cpu_hotplug_disabled)
1109 return _cpu_down(cpu, 0, target);
1112 static int cpu_down(unsigned int cpu, enum cpuhp_state target)
1116 cpu_maps_update_begin();
1117 err = cpu_down_maps_locked(cpu, target);
1118 cpu_maps_update_done();
1123 * cpu_device_down - Bring down a cpu device
1124 * @dev: Pointer to the cpu device to offline
1126 * This function is meant to be used by device core cpu subsystem only.
1128 * Other subsystems should use remove_cpu() instead.
1130 int cpu_device_down(struct device *dev)
1132 return cpu_down(dev->id, CPUHP_OFFLINE);
1135 int remove_cpu(unsigned int cpu)
1139 lock_device_hotplug();
1140 ret = device_offline(get_cpu_device(cpu));
1141 unlock_device_hotplug();
1145 EXPORT_SYMBOL_GPL(remove_cpu);
1147 void smp_shutdown_nonboot_cpus(unsigned int primary_cpu)
1152 cpu_maps_update_begin();
1155 * Make certain the cpu I'm about to reboot on is online.
1157 * This is inline to what migrate_to_reboot_cpu() already do.
1159 if (!cpu_online(primary_cpu))
1160 primary_cpu = cpumask_first(cpu_online_mask);
1162 for_each_online_cpu(cpu) {
1163 if (cpu == primary_cpu)
1166 error = cpu_down_maps_locked(cpu, CPUHP_OFFLINE);
1168 pr_err("Failed to offline CPU%d - error=%d",
1175 * Ensure all but the reboot CPU are offline.
1177 BUG_ON(num_online_cpus() > 1);
1180 * Make sure the CPUs won't be enabled by someone else after this
1181 * point. Kexec will reboot to a new kernel shortly resetting
1182 * everything along the way.
1184 cpu_hotplug_disabled++;
1186 cpu_maps_update_done();
1190 #define takedown_cpu NULL
1191 #endif /*CONFIG_HOTPLUG_CPU*/
1194 * notify_cpu_starting(cpu) - Invoke the callbacks on the starting CPU
1195 * @cpu: cpu that just started
1197 * It must be called by the arch code on the new cpu, before the new cpu
1198 * enables interrupts and before the "boot" cpu returns from __cpu_up().
1200 void notify_cpu_starting(unsigned int cpu)
1202 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1203 enum cpuhp_state target = min((int)st->target, CPUHP_AP_ONLINE);
1206 rcu_cpu_starting(cpu); /* Enables RCU usage on this CPU. */
1207 cpumask_set_cpu(cpu, &cpus_booted_once_mask);
1208 while (st->state < target) {
1210 ret = cpuhp_invoke_callback(cpu, st->state, true, NULL, NULL);
1212 * STARTING must not fail!
1219 * Called from the idle task. Wake up the controlling task which brings the
1220 * hotplug thread of the upcoming CPU up and then delegates the rest of the
1221 * online bringup to the hotplug thread.
1223 void cpuhp_online_idle(enum cpuhp_state state)
1225 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
1227 /* Happens for the boot cpu */
1228 if (state != CPUHP_AP_ONLINE_IDLE)
1232 * Unpart the stopper thread before we start the idle loop (and start
1233 * scheduling); this ensures the stopper task is always available.
1235 stop_machine_unpark(smp_processor_id());
1237 st->state = CPUHP_AP_ONLINE_IDLE;
1238 complete_ap_thread(st, true);
1241 /* Requires cpu_add_remove_lock to be held */
1242 static int _cpu_up(unsigned int cpu, int tasks_frozen, enum cpuhp_state target)
1244 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1245 struct task_struct *idle;
1250 if (!cpu_present(cpu)) {
1256 * The caller of cpu_up() might have raced with another
1257 * caller. Nothing to do.
1259 if (st->state >= target)
1262 if (st->state == CPUHP_OFFLINE) {
1263 /* Let it fail before we try to bring the cpu up */
1264 idle = idle_thread_get(cpu);
1266 ret = PTR_ERR(idle);
1271 cpuhp_tasks_frozen = tasks_frozen;
1273 cpuhp_set_state(st, target);
1275 * If the current CPU state is in the range of the AP hotplug thread,
1276 * then we need to kick the thread once more.
1278 if (st->state > CPUHP_BRINGUP_CPU) {
1279 ret = cpuhp_kick_ap_work(cpu);
1281 * The AP side has done the error rollback already. Just
1282 * return the error code..
1289 * Try to reach the target state. We max out on the BP at
1290 * CPUHP_BRINGUP_CPU. After that the AP hotplug thread is
1291 * responsible for bringing it up to the target state.
1293 target = min((int)target, CPUHP_BRINGUP_CPU);
1294 ret = cpuhp_up_callbacks(cpu, st, target);
1296 cpus_write_unlock();
1298 cpu_up_down_serialize_trainwrecks(tasks_frozen);
1302 static int cpu_up(unsigned int cpu, enum cpuhp_state target)
1306 if (!cpu_possible(cpu)) {
1307 pr_err("can't online cpu %d because it is not configured as may-hotadd at boot time\n",
1309 #if defined(CONFIG_IA64)
1310 pr_err("please check additional_cpus= boot parameter\n");
1315 err = try_online_node(cpu_to_node(cpu));
1319 cpu_maps_update_begin();
1321 if (cpu_hotplug_disabled) {
1325 if (!cpu_smt_allowed(cpu)) {
1330 err = _cpu_up(cpu, 0, target);
1332 cpu_maps_update_done();
1337 * cpu_device_up - Bring up a cpu device
1338 * @dev: Pointer to the cpu device to online
1340 * This function is meant to be used by device core cpu subsystem only.
1342 * Other subsystems should use add_cpu() instead.
1344 int cpu_device_up(struct device *dev)
1346 return cpu_up(dev->id, CPUHP_ONLINE);
1349 int add_cpu(unsigned int cpu)
1353 lock_device_hotplug();
1354 ret = device_online(get_cpu_device(cpu));
1355 unlock_device_hotplug();
1359 EXPORT_SYMBOL_GPL(add_cpu);
1362 * bringup_hibernate_cpu - Bring up the CPU that we hibernated on
1363 * @sleep_cpu: The cpu we hibernated on and should be brought up.
1365 * On some architectures like arm64, we can hibernate on any CPU, but on
1366 * wake up the CPU we hibernated on might be offline as a side effect of
1367 * using maxcpus= for example.
1369 int bringup_hibernate_cpu(unsigned int sleep_cpu)
1373 if (!cpu_online(sleep_cpu)) {
1374 pr_info("Hibernated on a CPU that is offline! Bringing CPU up.\n");
1375 ret = cpu_up(sleep_cpu, CPUHP_ONLINE);
1377 pr_err("Failed to bring hibernate-CPU up!\n");
1384 void bringup_nonboot_cpus(unsigned int setup_max_cpus)
1388 for_each_present_cpu(cpu) {
1389 if (num_online_cpus() >= setup_max_cpus)
1391 if (!cpu_online(cpu))
1392 cpu_up(cpu, CPUHP_ONLINE);
1396 #ifdef CONFIG_PM_SLEEP_SMP
1397 static cpumask_var_t frozen_cpus;
1399 int freeze_secondary_cpus(int primary)
1403 cpu_maps_update_begin();
1404 if (primary == -1) {
1405 primary = cpumask_first(cpu_online_mask);
1406 if (!housekeeping_cpu(primary, HK_FLAG_TIMER))
1407 primary = housekeeping_any_cpu(HK_FLAG_TIMER);
1409 if (!cpu_online(primary))
1410 primary = cpumask_first(cpu_online_mask);
1414 * We take down all of the non-boot CPUs in one shot to avoid races
1415 * with the userspace trying to use the CPU hotplug at the same time
1417 cpumask_clear(frozen_cpus);
1419 pr_info("Disabling non-boot CPUs ...\n");
1420 for_each_online_cpu(cpu) {
1424 if (pm_wakeup_pending()) {
1425 pr_info("Wakeup pending. Abort CPU freeze\n");
1430 trace_suspend_resume(TPS("CPU_OFF"), cpu, true);
1431 error = _cpu_down(cpu, 1, CPUHP_OFFLINE);
1432 trace_suspend_resume(TPS("CPU_OFF"), cpu, false);
1434 cpumask_set_cpu(cpu, frozen_cpus);
1436 pr_err("Error taking CPU%d down: %d\n", cpu, error);
1442 BUG_ON(num_online_cpus() > 1);
1444 pr_err("Non-boot CPUs are not disabled\n");
1447 * Make sure the CPUs won't be enabled by someone else. We need to do
1448 * this even in case of failure as all freeze_secondary_cpus() users are
1449 * supposed to do thaw_secondary_cpus() on the failure path.
1451 cpu_hotplug_disabled++;
1453 cpu_maps_update_done();
1457 void __weak arch_thaw_secondary_cpus_begin(void)
1461 void __weak arch_thaw_secondary_cpus_end(void)
1465 void thaw_secondary_cpus(void)
1469 /* Allow everyone to use the CPU hotplug again */
1470 cpu_maps_update_begin();
1471 __cpu_hotplug_enable();
1472 if (cpumask_empty(frozen_cpus))
1475 pr_info("Enabling non-boot CPUs ...\n");
1477 arch_thaw_secondary_cpus_begin();
1479 for_each_cpu(cpu, frozen_cpus) {
1480 trace_suspend_resume(TPS("CPU_ON"), cpu, true);
1481 error = _cpu_up(cpu, 1, CPUHP_ONLINE);
1482 trace_suspend_resume(TPS("CPU_ON"), cpu, false);
1484 pr_info("CPU%d is up\n", cpu);
1487 pr_warn("Error taking CPU%d up: %d\n", cpu, error);
1490 arch_thaw_secondary_cpus_end();
1492 cpumask_clear(frozen_cpus);
1494 cpu_maps_update_done();
1497 static int __init alloc_frozen_cpus(void)
1499 if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
1503 core_initcall(alloc_frozen_cpus);
1506 * When callbacks for CPU hotplug notifications are being executed, we must
1507 * ensure that the state of the system with respect to the tasks being frozen
1508 * or not, as reported by the notification, remains unchanged *throughout the
1509 * duration* of the execution of the callbacks.
1510 * Hence we need to prevent the freezer from racing with regular CPU hotplug.
1512 * This synchronization is implemented by mutually excluding regular CPU
1513 * hotplug and Suspend/Hibernate call paths by hooking onto the Suspend/
1514 * Hibernate notifications.
1517 cpu_hotplug_pm_callback(struct notifier_block *nb,
1518 unsigned long action, void *ptr)
1522 case PM_SUSPEND_PREPARE:
1523 case PM_HIBERNATION_PREPARE:
1524 cpu_hotplug_disable();
1527 case PM_POST_SUSPEND:
1528 case PM_POST_HIBERNATION:
1529 cpu_hotplug_enable();
1540 static int __init cpu_hotplug_pm_sync_init(void)
1543 * cpu_hotplug_pm_callback has higher priority than x86
1544 * bsp_pm_callback which depends on cpu_hotplug_pm_callback
1545 * to disable cpu hotplug to avoid cpu hotplug race.
1547 pm_notifier(cpu_hotplug_pm_callback, 0);
1550 core_initcall(cpu_hotplug_pm_sync_init);
1552 #endif /* CONFIG_PM_SLEEP_SMP */
1556 #endif /* CONFIG_SMP */
1558 /* Boot processor state steps */
1559 static struct cpuhp_step cpuhp_hp_states[] = {
1562 .startup.single = NULL,
1563 .teardown.single = NULL,
1566 [CPUHP_CREATE_THREADS]= {
1567 .name = "threads:prepare",
1568 .startup.single = smpboot_create_threads,
1569 .teardown.single = NULL,
1572 [CPUHP_PERF_PREPARE] = {
1573 .name = "perf:prepare",
1574 .startup.single = perf_event_init_cpu,
1575 .teardown.single = perf_event_exit_cpu,
1577 [CPUHP_WORKQUEUE_PREP] = {
1578 .name = "workqueue:prepare",
1579 .startup.single = workqueue_prepare_cpu,
1580 .teardown.single = NULL,
1582 [CPUHP_HRTIMERS_PREPARE] = {
1583 .name = "hrtimers:prepare",
1584 .startup.single = hrtimers_prepare_cpu,
1585 .teardown.single = hrtimers_dead_cpu,
1587 [CPUHP_SMPCFD_PREPARE] = {
1588 .name = "smpcfd:prepare",
1589 .startup.single = smpcfd_prepare_cpu,
1590 .teardown.single = smpcfd_dead_cpu,
1592 [CPUHP_RELAY_PREPARE] = {
1593 .name = "relay:prepare",
1594 .startup.single = relay_prepare_cpu,
1595 .teardown.single = NULL,
1597 [CPUHP_SLAB_PREPARE] = {
1598 .name = "slab:prepare",
1599 .startup.single = slab_prepare_cpu,
1600 .teardown.single = slab_dead_cpu,
1602 [CPUHP_RCUTREE_PREP] = {
1603 .name = "RCU/tree:prepare",
1604 .startup.single = rcutree_prepare_cpu,
1605 .teardown.single = rcutree_dead_cpu,
1608 * On the tear-down path, timers_dead_cpu() must be invoked
1609 * before blk_mq_queue_reinit_notify() from notify_dead(),
1610 * otherwise a RCU stall occurs.
1612 [CPUHP_TIMERS_PREPARE] = {
1613 .name = "timers:prepare",
1614 .startup.single = timers_prepare_cpu,
1615 .teardown.single = timers_dead_cpu,
1617 /* Kicks the plugged cpu into life */
1618 [CPUHP_BRINGUP_CPU] = {
1619 .name = "cpu:bringup",
1620 .startup.single = bringup_cpu,
1621 .teardown.single = finish_cpu,
1624 /* Final state before CPU kills itself */
1625 [CPUHP_AP_IDLE_DEAD] = {
1626 .name = "idle:dead",
1629 * Last state before CPU enters the idle loop to die. Transient state
1630 * for synchronization.
1632 [CPUHP_AP_OFFLINE] = {
1633 .name = "ap:offline",
1636 /* First state is scheduler control. Interrupts are disabled */
1637 [CPUHP_AP_SCHED_STARTING] = {
1638 .name = "sched:starting",
1639 .startup.single = sched_cpu_starting,
1640 .teardown.single = sched_cpu_dying,
1642 [CPUHP_AP_RCUTREE_DYING] = {
1643 .name = "RCU/tree:dying",
1644 .startup.single = NULL,
1645 .teardown.single = rcutree_dying_cpu,
1647 [CPUHP_AP_SMPCFD_DYING] = {
1648 .name = "smpcfd:dying",
1649 .startup.single = NULL,
1650 .teardown.single = smpcfd_dying_cpu,
1652 /* Entry state on starting. Interrupts enabled from here on. Transient
1653 * state for synchronsization */
1654 [CPUHP_AP_ONLINE] = {
1655 .name = "ap:online",
1658 * Handled on controll processor until the plugged processor manages
1661 [CPUHP_TEARDOWN_CPU] = {
1662 .name = "cpu:teardown",
1663 .startup.single = NULL,
1664 .teardown.single = takedown_cpu,
1667 /* Handle smpboot threads park/unpark */
1668 [CPUHP_AP_SMPBOOT_THREADS] = {
1669 .name = "smpboot/threads:online",
1670 .startup.single = smpboot_unpark_threads,
1671 .teardown.single = smpboot_park_threads,
1673 [CPUHP_AP_IRQ_AFFINITY_ONLINE] = {
1674 .name = "irq/affinity:online",
1675 .startup.single = irq_affinity_online_cpu,
1676 .teardown.single = NULL,
1678 [CPUHP_AP_PERF_ONLINE] = {
1679 .name = "perf:online",
1680 .startup.single = perf_event_init_cpu,
1681 .teardown.single = perf_event_exit_cpu,
1683 [CPUHP_AP_WATCHDOG_ONLINE] = {
1684 .name = "lockup_detector:online",
1685 .startup.single = lockup_detector_online_cpu,
1686 .teardown.single = lockup_detector_offline_cpu,
1688 [CPUHP_AP_WORKQUEUE_ONLINE] = {
1689 .name = "workqueue:online",
1690 .startup.single = workqueue_online_cpu,
1691 .teardown.single = workqueue_offline_cpu,
1693 [CPUHP_AP_RCUTREE_ONLINE] = {
1694 .name = "RCU/tree:online",
1695 .startup.single = rcutree_online_cpu,
1696 .teardown.single = rcutree_offline_cpu,
1700 * The dynamically registered state space is here
1704 /* Last state is scheduler control setting the cpu active */
1705 [CPUHP_AP_ACTIVE] = {
1706 .name = "sched:active",
1707 .startup.single = sched_cpu_activate,
1708 .teardown.single = sched_cpu_deactivate,
1712 /* CPU is fully up and running. */
1715 .startup.single = NULL,
1716 .teardown.single = NULL,
1720 /* Sanity check for callbacks */
1721 static int cpuhp_cb_check(enum cpuhp_state state)
1723 if (state <= CPUHP_OFFLINE || state >= CPUHP_ONLINE)
1729 * Returns a free for dynamic slot assignment of the Online state. The states
1730 * are protected by the cpuhp_slot_states mutex and an empty slot is identified
1731 * by having no name assigned.
1733 static int cpuhp_reserve_state(enum cpuhp_state state)
1735 enum cpuhp_state i, end;
1736 struct cpuhp_step *step;
1739 case CPUHP_AP_ONLINE_DYN:
1740 step = cpuhp_hp_states + CPUHP_AP_ONLINE_DYN;
1741 end = CPUHP_AP_ONLINE_DYN_END;
1743 case CPUHP_BP_PREPARE_DYN:
1744 step = cpuhp_hp_states + CPUHP_BP_PREPARE_DYN;
1745 end = CPUHP_BP_PREPARE_DYN_END;
1751 for (i = state; i <= end; i++, step++) {
1755 WARN(1, "No more dynamic states available for CPU hotplug\n");
1759 static int cpuhp_store_callbacks(enum cpuhp_state state, const char *name,
1760 int (*startup)(unsigned int cpu),
1761 int (*teardown)(unsigned int cpu),
1762 bool multi_instance)
1764 /* (Un)Install the callbacks for further cpu hotplug operations */
1765 struct cpuhp_step *sp;
1769 * If name is NULL, then the state gets removed.
1771 * CPUHP_AP_ONLINE_DYN and CPUHP_BP_PREPARE_DYN are handed out on
1772 * the first allocation from these dynamic ranges, so the removal
1773 * would trigger a new allocation and clear the wrong (already
1774 * empty) state, leaving the callbacks of the to be cleared state
1775 * dangling, which causes wreckage on the next hotplug operation.
1777 if (name && (state == CPUHP_AP_ONLINE_DYN ||
1778 state == CPUHP_BP_PREPARE_DYN)) {
1779 ret = cpuhp_reserve_state(state);
1784 sp = cpuhp_get_step(state);
1785 if (name && sp->name)
1788 sp->startup.single = startup;
1789 sp->teardown.single = teardown;
1791 sp->multi_instance = multi_instance;
1792 INIT_HLIST_HEAD(&sp->list);
1796 static void *cpuhp_get_teardown_cb(enum cpuhp_state state)
1798 return cpuhp_get_step(state)->teardown.single;
1802 * Call the startup/teardown function for a step either on the AP or
1803 * on the current CPU.
1805 static int cpuhp_issue_call(int cpu, enum cpuhp_state state, bool bringup,
1806 struct hlist_node *node)
1808 struct cpuhp_step *sp = cpuhp_get_step(state);
1812 * If there's nothing to do, we done.
1813 * Relies on the union for multi_instance.
1815 if ((bringup && !sp->startup.single) ||
1816 (!bringup && !sp->teardown.single))
1819 * The non AP bound callbacks can fail on bringup. On teardown
1820 * e.g. module removal we crash for now.
1823 if (cpuhp_is_ap_state(state))
1824 ret = cpuhp_invoke_ap_callback(cpu, state, bringup, node);
1826 ret = cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
1828 ret = cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
1830 BUG_ON(ret && !bringup);
1835 * Called from __cpuhp_setup_state on a recoverable failure.
1837 * Note: The teardown callbacks for rollback are not allowed to fail!
1839 static void cpuhp_rollback_install(int failedcpu, enum cpuhp_state state,
1840 struct hlist_node *node)
1844 /* Roll back the already executed steps on the other cpus */
1845 for_each_present_cpu(cpu) {
1846 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1847 int cpustate = st->state;
1849 if (cpu >= failedcpu)
1852 /* Did we invoke the startup call on that cpu ? */
1853 if (cpustate >= state)
1854 cpuhp_issue_call(cpu, state, false, node);
1858 int __cpuhp_state_add_instance_cpuslocked(enum cpuhp_state state,
1859 struct hlist_node *node,
1862 struct cpuhp_step *sp;
1866 lockdep_assert_cpus_held();
1868 sp = cpuhp_get_step(state);
1869 if (sp->multi_instance == false)
1872 mutex_lock(&cpuhp_state_mutex);
1874 if (!invoke || !sp->startup.multi)
1878 * Try to call the startup callback for each present cpu
1879 * depending on the hotplug state of the cpu.
1881 for_each_present_cpu(cpu) {
1882 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1883 int cpustate = st->state;
1885 if (cpustate < state)
1888 ret = cpuhp_issue_call(cpu, state, true, node);
1890 if (sp->teardown.multi)
1891 cpuhp_rollback_install(cpu, state, node);
1897 hlist_add_head(node, &sp->list);
1899 mutex_unlock(&cpuhp_state_mutex);
1903 int __cpuhp_state_add_instance(enum cpuhp_state state, struct hlist_node *node,
1909 ret = __cpuhp_state_add_instance_cpuslocked(state, node, invoke);
1913 EXPORT_SYMBOL_GPL(__cpuhp_state_add_instance);
1916 * __cpuhp_setup_state_cpuslocked - Setup the callbacks for an hotplug machine state
1917 * @state: The state to setup
1918 * @invoke: If true, the startup function is invoked for cpus where
1919 * cpu state >= @state
1920 * @startup: startup callback function
1921 * @teardown: teardown callback function
1922 * @multi_instance: State is set up for multiple instances which get
1925 * The caller needs to hold cpus read locked while calling this function.
1928 * Positive state number if @state is CPUHP_AP_ONLINE_DYN
1929 * 0 for all other states
1930 * On failure: proper (negative) error code
1932 int __cpuhp_setup_state_cpuslocked(enum cpuhp_state state,
1933 const char *name, bool invoke,
1934 int (*startup)(unsigned int cpu),
1935 int (*teardown)(unsigned int cpu),
1936 bool multi_instance)
1941 lockdep_assert_cpus_held();
1943 if (cpuhp_cb_check(state) || !name)
1946 mutex_lock(&cpuhp_state_mutex);
1948 ret = cpuhp_store_callbacks(state, name, startup, teardown,
1951 dynstate = state == CPUHP_AP_ONLINE_DYN;
1952 if (ret > 0 && dynstate) {
1957 if (ret || !invoke || !startup)
1961 * Try to call the startup callback for each present cpu
1962 * depending on the hotplug state of the cpu.
1964 for_each_present_cpu(cpu) {
1965 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1966 int cpustate = st->state;
1968 if (cpustate < state)
1971 ret = cpuhp_issue_call(cpu, state, true, NULL);
1974 cpuhp_rollback_install(cpu, state, NULL);
1975 cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
1980 mutex_unlock(&cpuhp_state_mutex);
1982 * If the requested state is CPUHP_AP_ONLINE_DYN, return the
1983 * dynamically allocated state in case of success.
1985 if (!ret && dynstate)
1989 EXPORT_SYMBOL(__cpuhp_setup_state_cpuslocked);
1991 int __cpuhp_setup_state(enum cpuhp_state state,
1992 const char *name, bool invoke,
1993 int (*startup)(unsigned int cpu),
1994 int (*teardown)(unsigned int cpu),
1995 bool multi_instance)
2000 ret = __cpuhp_setup_state_cpuslocked(state, name, invoke, startup,
2001 teardown, multi_instance);
2005 EXPORT_SYMBOL(__cpuhp_setup_state);
2007 int __cpuhp_state_remove_instance(enum cpuhp_state state,
2008 struct hlist_node *node, bool invoke)
2010 struct cpuhp_step *sp = cpuhp_get_step(state);
2013 BUG_ON(cpuhp_cb_check(state));
2015 if (!sp->multi_instance)
2019 mutex_lock(&cpuhp_state_mutex);
2021 if (!invoke || !cpuhp_get_teardown_cb(state))
2024 * Call the teardown callback for each present cpu depending
2025 * on the hotplug state of the cpu. This function is not
2026 * allowed to fail currently!
2028 for_each_present_cpu(cpu) {
2029 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
2030 int cpustate = st->state;
2032 if (cpustate >= state)
2033 cpuhp_issue_call(cpu, state, false, node);
2038 mutex_unlock(&cpuhp_state_mutex);
2043 EXPORT_SYMBOL_GPL(__cpuhp_state_remove_instance);
2046 * __cpuhp_remove_state_cpuslocked - Remove the callbacks for an hotplug machine state
2047 * @state: The state to remove
2048 * @invoke: If true, the teardown function is invoked for cpus where
2049 * cpu state >= @state
2051 * The caller needs to hold cpus read locked while calling this function.
2052 * The teardown callback is currently not allowed to fail. Think
2053 * about module removal!
2055 void __cpuhp_remove_state_cpuslocked(enum cpuhp_state state, bool invoke)
2057 struct cpuhp_step *sp = cpuhp_get_step(state);
2060 BUG_ON(cpuhp_cb_check(state));
2062 lockdep_assert_cpus_held();
2064 mutex_lock(&cpuhp_state_mutex);
2065 if (sp->multi_instance) {
2066 WARN(!hlist_empty(&sp->list),
2067 "Error: Removing state %d which has instances left.\n",
2072 if (!invoke || !cpuhp_get_teardown_cb(state))
2076 * Call the teardown callback for each present cpu depending
2077 * on the hotplug state of the cpu. This function is not
2078 * allowed to fail currently!
2080 for_each_present_cpu(cpu) {
2081 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
2082 int cpustate = st->state;
2084 if (cpustate >= state)
2085 cpuhp_issue_call(cpu, state, false, NULL);
2088 cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
2089 mutex_unlock(&cpuhp_state_mutex);
2091 EXPORT_SYMBOL(__cpuhp_remove_state_cpuslocked);
2093 void __cpuhp_remove_state(enum cpuhp_state state, bool invoke)
2096 __cpuhp_remove_state_cpuslocked(state, invoke);
2099 EXPORT_SYMBOL(__cpuhp_remove_state);
2101 #ifdef CONFIG_HOTPLUG_SMT
2102 static void cpuhp_offline_cpu_device(unsigned int cpu)
2104 struct device *dev = get_cpu_device(cpu);
2106 dev->offline = true;
2107 /* Tell user space about the state change */
2108 kobject_uevent(&dev->kobj, KOBJ_OFFLINE);
2111 static void cpuhp_online_cpu_device(unsigned int cpu)
2113 struct device *dev = get_cpu_device(cpu);
2115 dev->offline = false;
2116 /* Tell user space about the state change */
2117 kobject_uevent(&dev->kobj, KOBJ_ONLINE);
2120 int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval)
2124 cpu_maps_update_begin();
2125 for_each_online_cpu(cpu) {
2126 if (topology_is_primary_thread(cpu))
2128 ret = cpu_down_maps_locked(cpu, CPUHP_OFFLINE);
2132 * As this needs to hold the cpu maps lock it's impossible
2133 * to call device_offline() because that ends up calling
2134 * cpu_down() which takes cpu maps lock. cpu maps lock
2135 * needs to be held as this might race against in kernel
2136 * abusers of the hotplug machinery (thermal management).
2138 * So nothing would update device:offline state. That would
2139 * leave the sysfs entry stale and prevent onlining after
2140 * smt control has been changed to 'off' again. This is
2141 * called under the sysfs hotplug lock, so it is properly
2142 * serialized against the regular offline usage.
2144 cpuhp_offline_cpu_device(cpu);
2147 cpu_smt_control = ctrlval;
2148 cpu_maps_update_done();
2152 int cpuhp_smt_enable(void)
2156 cpu_maps_update_begin();
2157 cpu_smt_control = CPU_SMT_ENABLED;
2158 for_each_present_cpu(cpu) {
2159 /* Skip online CPUs and CPUs on offline nodes */
2160 if (cpu_online(cpu) || !node_online(cpu_to_node(cpu)))
2162 ret = _cpu_up(cpu, 0, CPUHP_ONLINE);
2165 /* See comment in cpuhp_smt_disable() */
2166 cpuhp_online_cpu_device(cpu);
2168 cpu_maps_update_done();
2173 #if defined(CONFIG_SYSFS) && defined(CONFIG_HOTPLUG_CPU)
2174 static ssize_t show_cpuhp_state(struct device *dev,
2175 struct device_attribute *attr, char *buf)
2177 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2179 return sprintf(buf, "%d\n", st->state);
2181 static DEVICE_ATTR(state, 0444, show_cpuhp_state, NULL);
2183 static ssize_t write_cpuhp_target(struct device *dev,
2184 struct device_attribute *attr,
2185 const char *buf, size_t count)
2187 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2188 struct cpuhp_step *sp;
2191 ret = kstrtoint(buf, 10, &target);
2195 #ifdef CONFIG_CPU_HOTPLUG_STATE_CONTROL
2196 if (target < CPUHP_OFFLINE || target > CPUHP_ONLINE)
2199 if (target != CPUHP_OFFLINE && target != CPUHP_ONLINE)
2203 ret = lock_device_hotplug_sysfs();
2207 mutex_lock(&cpuhp_state_mutex);
2208 sp = cpuhp_get_step(target);
2209 ret = !sp->name || sp->cant_stop ? -EINVAL : 0;
2210 mutex_unlock(&cpuhp_state_mutex);
2214 if (st->state < target)
2215 ret = cpu_up(dev->id, target);
2217 ret = cpu_down(dev->id, target);
2219 unlock_device_hotplug();
2220 return ret ? ret : count;
2223 static ssize_t show_cpuhp_target(struct device *dev,
2224 struct device_attribute *attr, char *buf)
2226 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2228 return sprintf(buf, "%d\n", st->target);
2230 static DEVICE_ATTR(target, 0644, show_cpuhp_target, write_cpuhp_target);
2233 static ssize_t write_cpuhp_fail(struct device *dev,
2234 struct device_attribute *attr,
2235 const char *buf, size_t count)
2237 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2238 struct cpuhp_step *sp;
2241 ret = kstrtoint(buf, 10, &fail);
2245 if (fail < CPUHP_OFFLINE || fail > CPUHP_ONLINE)
2249 * Cannot fail STARTING/DYING callbacks.
2251 if (cpuhp_is_atomic_state(fail))
2255 * Cannot fail anything that doesn't have callbacks.
2257 mutex_lock(&cpuhp_state_mutex);
2258 sp = cpuhp_get_step(fail);
2259 if (!sp->startup.single && !sp->teardown.single)
2261 mutex_unlock(&cpuhp_state_mutex);
2270 static ssize_t show_cpuhp_fail(struct device *dev,
2271 struct device_attribute *attr, char *buf)
2273 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2275 return sprintf(buf, "%d\n", st->fail);
2278 static DEVICE_ATTR(fail, 0644, show_cpuhp_fail, write_cpuhp_fail);
2280 static struct attribute *cpuhp_cpu_attrs[] = {
2281 &dev_attr_state.attr,
2282 &dev_attr_target.attr,
2283 &dev_attr_fail.attr,
2287 static const struct attribute_group cpuhp_cpu_attr_group = {
2288 .attrs = cpuhp_cpu_attrs,
2293 static ssize_t show_cpuhp_states(struct device *dev,
2294 struct device_attribute *attr, char *buf)
2296 ssize_t cur, res = 0;
2299 mutex_lock(&cpuhp_state_mutex);
2300 for (i = CPUHP_OFFLINE; i <= CPUHP_ONLINE; i++) {
2301 struct cpuhp_step *sp = cpuhp_get_step(i);
2304 cur = sprintf(buf, "%3d: %s\n", i, sp->name);
2309 mutex_unlock(&cpuhp_state_mutex);
2312 static DEVICE_ATTR(states, 0444, show_cpuhp_states, NULL);
2314 static struct attribute *cpuhp_cpu_root_attrs[] = {
2315 &dev_attr_states.attr,
2319 static const struct attribute_group cpuhp_cpu_root_attr_group = {
2320 .attrs = cpuhp_cpu_root_attrs,
2325 #ifdef CONFIG_HOTPLUG_SMT
2328 __store_smt_control(struct device *dev, struct device_attribute *attr,
2329 const char *buf, size_t count)
2333 if (sysfs_streq(buf, "on"))
2334 ctrlval = CPU_SMT_ENABLED;
2335 else if (sysfs_streq(buf, "off"))
2336 ctrlval = CPU_SMT_DISABLED;
2337 else if (sysfs_streq(buf, "forceoff"))
2338 ctrlval = CPU_SMT_FORCE_DISABLED;
2342 if (cpu_smt_control == CPU_SMT_FORCE_DISABLED)
2345 if (cpu_smt_control == CPU_SMT_NOT_SUPPORTED)
2348 ret = lock_device_hotplug_sysfs();
2352 if (ctrlval != cpu_smt_control) {
2354 case CPU_SMT_ENABLED:
2355 ret = cpuhp_smt_enable();
2357 case CPU_SMT_DISABLED:
2358 case CPU_SMT_FORCE_DISABLED:
2359 ret = cpuhp_smt_disable(ctrlval);
2364 unlock_device_hotplug();
2365 return ret ? ret : count;
2368 #else /* !CONFIG_HOTPLUG_SMT */
2370 __store_smt_control(struct device *dev, struct device_attribute *attr,
2371 const char *buf, size_t count)
2375 #endif /* CONFIG_HOTPLUG_SMT */
2377 static const char *smt_states[] = {
2378 [CPU_SMT_ENABLED] = "on",
2379 [CPU_SMT_DISABLED] = "off",
2380 [CPU_SMT_FORCE_DISABLED] = "forceoff",
2381 [CPU_SMT_NOT_SUPPORTED] = "notsupported",
2382 [CPU_SMT_NOT_IMPLEMENTED] = "notimplemented",
2386 show_smt_control(struct device *dev, struct device_attribute *attr, char *buf)
2388 const char *state = smt_states[cpu_smt_control];
2390 return snprintf(buf, PAGE_SIZE - 2, "%s\n", state);
2394 store_smt_control(struct device *dev, struct device_attribute *attr,
2395 const char *buf, size_t count)
2397 return __store_smt_control(dev, attr, buf, count);
2399 static DEVICE_ATTR(control, 0644, show_smt_control, store_smt_control);
2402 show_smt_active(struct device *dev, struct device_attribute *attr, char *buf)
2404 return snprintf(buf, PAGE_SIZE - 2, "%d\n", sched_smt_active());
2406 static DEVICE_ATTR(active, 0444, show_smt_active, NULL);
2408 static struct attribute *cpuhp_smt_attrs[] = {
2409 &dev_attr_control.attr,
2410 &dev_attr_active.attr,
2414 static const struct attribute_group cpuhp_smt_attr_group = {
2415 .attrs = cpuhp_smt_attrs,
2420 static int __init cpu_smt_sysfs_init(void)
2422 return sysfs_create_group(&cpu_subsys.dev_root->kobj,
2423 &cpuhp_smt_attr_group);
2426 static int __init cpuhp_sysfs_init(void)
2430 ret = cpu_smt_sysfs_init();
2434 ret = sysfs_create_group(&cpu_subsys.dev_root->kobj,
2435 &cpuhp_cpu_root_attr_group);
2439 for_each_possible_cpu(cpu) {
2440 struct device *dev = get_cpu_device(cpu);
2444 ret = sysfs_create_group(&dev->kobj, &cpuhp_cpu_attr_group);
2450 device_initcall(cpuhp_sysfs_init);
2451 #endif /* CONFIG_SYSFS && CONFIG_HOTPLUG_CPU */
2454 * cpu_bit_bitmap[] is a special, "compressed" data structure that
2455 * represents all NR_CPUS bits binary values of 1<<nr.
2457 * It is used by cpumask_of() to get a constant address to a CPU
2458 * mask value that has a single bit set only.
2461 /* cpu_bit_bitmap[0] is empty - so we can back into it */
2462 #define MASK_DECLARE_1(x) [x+1][0] = (1UL << (x))
2463 #define MASK_DECLARE_2(x) MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
2464 #define MASK_DECLARE_4(x) MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
2465 #define MASK_DECLARE_8(x) MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
2467 const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
2469 MASK_DECLARE_8(0), MASK_DECLARE_8(8),
2470 MASK_DECLARE_8(16), MASK_DECLARE_8(24),
2471 #if BITS_PER_LONG > 32
2472 MASK_DECLARE_8(32), MASK_DECLARE_8(40),
2473 MASK_DECLARE_8(48), MASK_DECLARE_8(56),
2476 EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
2478 const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
2479 EXPORT_SYMBOL(cpu_all_bits);
2481 #ifdef CONFIG_INIT_ALL_POSSIBLE
2482 struct cpumask __cpu_possible_mask __read_mostly
2485 struct cpumask __cpu_possible_mask __read_mostly;
2487 EXPORT_SYMBOL(__cpu_possible_mask);
2489 struct cpumask __cpu_online_mask __read_mostly;
2490 EXPORT_SYMBOL(__cpu_online_mask);
2492 struct cpumask __cpu_present_mask __read_mostly;
2493 EXPORT_SYMBOL(__cpu_present_mask);
2495 struct cpumask __cpu_active_mask __read_mostly;
2496 EXPORT_SYMBOL(__cpu_active_mask);
2498 atomic_t __num_online_cpus __read_mostly;
2499 EXPORT_SYMBOL(__num_online_cpus);
2501 void init_cpu_present(const struct cpumask *src)
2503 cpumask_copy(&__cpu_present_mask, src);
2506 void init_cpu_possible(const struct cpumask *src)
2508 cpumask_copy(&__cpu_possible_mask, src);
2511 void init_cpu_online(const struct cpumask *src)
2513 cpumask_copy(&__cpu_online_mask, src);
2516 void set_cpu_online(unsigned int cpu, bool online)
2519 * atomic_inc/dec() is required to handle the horrid abuse of this
2520 * function by the reboot and kexec code which invoke it from
2521 * IPI/NMI broadcasts when shutting down CPUs. Invocation from
2522 * regular CPU hotplug is properly serialized.
2524 * Note, that the fact that __num_online_cpus is of type atomic_t
2525 * does not protect readers which are not serialized against
2526 * concurrent hotplug operations.
2529 if (!cpumask_test_and_set_cpu(cpu, &__cpu_online_mask))
2530 atomic_inc(&__num_online_cpus);
2532 if (cpumask_test_and_clear_cpu(cpu, &__cpu_online_mask))
2533 atomic_dec(&__num_online_cpus);
2538 * Activate the first processor.
2540 void __init boot_cpu_init(void)
2542 int cpu = smp_processor_id();
2544 /* Mark the boot cpu "present", "online" etc for SMP and UP case */
2545 set_cpu_online(cpu, true);
2546 set_cpu_active(cpu, true);
2547 set_cpu_present(cpu, true);
2548 set_cpu_possible(cpu, true);
2551 __boot_cpu_id = cpu;
2556 * Must be called _AFTER_ setting up the per_cpu areas
2558 void __init boot_cpu_hotplug_init(void)
2561 cpumask_set_cpu(smp_processor_id(), &cpus_booted_once_mask);
2563 this_cpu_write(cpuhp_state.state, CPUHP_ONLINE);
2567 * These are used for a global "mitigations=" cmdline option for toggling
2568 * optional CPU mitigations.
2570 enum cpu_mitigations {
2571 CPU_MITIGATIONS_OFF,
2572 CPU_MITIGATIONS_AUTO,
2573 CPU_MITIGATIONS_AUTO_NOSMT,
2576 static enum cpu_mitigations cpu_mitigations __ro_after_init =
2577 CPU_MITIGATIONS_AUTO;
2579 static int __init mitigations_parse_cmdline(char *arg)
2581 if (!strcmp(arg, "off"))
2582 cpu_mitigations = CPU_MITIGATIONS_OFF;
2583 else if (!strcmp(arg, "auto"))
2584 cpu_mitigations = CPU_MITIGATIONS_AUTO;
2585 else if (!strcmp(arg, "auto,nosmt"))
2586 cpu_mitigations = CPU_MITIGATIONS_AUTO_NOSMT;
2588 pr_crit("Unsupported mitigations=%s, system may still be vulnerable\n",
2593 early_param("mitigations", mitigations_parse_cmdline);
2595 /* mitigations=off */
2596 bool cpu_mitigations_off(void)
2598 return cpu_mitigations == CPU_MITIGATIONS_OFF;
2600 EXPORT_SYMBOL_GPL(cpu_mitigations_off);
2602 /* mitigations=auto,nosmt */
2603 bool cpu_mitigations_auto_nosmt(void)
2605 return cpu_mitigations == CPU_MITIGATIONS_AUTO_NOSMT;
2607 EXPORT_SYMBOL_GPL(cpu_mitigations_auto_nosmt);