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 * struct cpuhp_cpu_state - Per cpu hotplug state storage
45 * @state: The current cpu state
46 * @target: The target state
47 * @fail: Current CPU hotplug callback state
48 * @thread: Pointer to the hotplug thread
49 * @should_run: Thread should execute
50 * @rollback: Perform a rollback
51 * @single: Single callback invocation
52 * @bringup: Single callback bringup or teardown selector
54 * @node: Remote CPU node; for multi-instance, do a
55 * single entry callback for install/remove
56 * @last: For multi-instance rollback, remember how far we got
57 * @cb_state: The state for a single callback (install/uninstall)
58 * @result: Result of the operation
59 * @done_up: Signal completion to the issuer of the task for cpu-up
60 * @done_down: Signal completion to the issuer of the task for cpu-down
62 struct cpuhp_cpu_state {
63 enum cpuhp_state state;
64 enum cpuhp_state target;
65 enum cpuhp_state fail;
67 struct task_struct *thread;
73 struct hlist_node *node;
74 struct hlist_node *last;
75 enum cpuhp_state cb_state;
77 struct completion done_up;
78 struct completion done_down;
82 static DEFINE_PER_CPU(struct cpuhp_cpu_state, cpuhp_state) = {
83 .fail = CPUHP_INVALID,
87 cpumask_t cpus_booted_once_mask;
90 #if defined(CONFIG_LOCKDEP) && defined(CONFIG_SMP)
91 static struct lockdep_map cpuhp_state_up_map =
92 STATIC_LOCKDEP_MAP_INIT("cpuhp_state-up", &cpuhp_state_up_map);
93 static struct lockdep_map cpuhp_state_down_map =
94 STATIC_LOCKDEP_MAP_INIT("cpuhp_state-down", &cpuhp_state_down_map);
97 static inline void cpuhp_lock_acquire(bool bringup)
99 lock_map_acquire(bringup ? &cpuhp_state_up_map : &cpuhp_state_down_map);
102 static inline void cpuhp_lock_release(bool bringup)
104 lock_map_release(bringup ? &cpuhp_state_up_map : &cpuhp_state_down_map);
108 static inline void cpuhp_lock_acquire(bool bringup) { }
109 static inline void cpuhp_lock_release(bool bringup) { }
114 * struct cpuhp_step - Hotplug state machine step
115 * @name: Name of the step
116 * @startup: Startup function of the step
117 * @teardown: Teardown function of the step
118 * @cant_stop: Bringup/teardown can't be stopped at this step
119 * @multi_instance: State has multiple instances which get added afterwards
124 int (*single)(unsigned int cpu);
125 int (*multi)(unsigned int cpu,
126 struct hlist_node *node);
129 int (*single)(unsigned int cpu);
130 int (*multi)(unsigned int cpu,
131 struct hlist_node *node);
134 struct hlist_head list;
140 static DEFINE_MUTEX(cpuhp_state_mutex);
141 static struct cpuhp_step cpuhp_hp_states[];
143 static struct cpuhp_step *cpuhp_get_step(enum cpuhp_state state)
145 return cpuhp_hp_states + state;
148 static bool cpuhp_step_empty(bool bringup, struct cpuhp_step *step)
150 return bringup ? !step->startup.single : !step->teardown.single;
154 * cpuhp_invoke_callback - Invoke the callbacks for a given state
155 * @cpu: The cpu for which the callback should be invoked
156 * @state: The state to do callbacks for
157 * @bringup: True if the bringup callback should be invoked
158 * @node: For multi-instance, do a single entry callback for install/remove
159 * @lastp: For multi-instance rollback, remember how far we got
161 * Called from cpu hotplug and from the state register machinery.
163 * Return: %0 on success or a negative errno code
165 static int cpuhp_invoke_callback(unsigned int cpu, enum cpuhp_state state,
166 bool bringup, struct hlist_node *node,
167 struct hlist_node **lastp)
169 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
170 struct cpuhp_step *step = cpuhp_get_step(state);
171 int (*cbm)(unsigned int cpu, struct hlist_node *node);
172 int (*cb)(unsigned int cpu);
175 if (st->fail == state) {
176 st->fail = CPUHP_INVALID;
180 if (cpuhp_step_empty(bringup, step)) {
185 if (!step->multi_instance) {
186 WARN_ON_ONCE(lastp && *lastp);
187 cb = bringup ? step->startup.single : step->teardown.single;
189 trace_cpuhp_enter(cpu, st->target, state, cb);
191 trace_cpuhp_exit(cpu, st->state, state, ret);
194 cbm = bringup ? step->startup.multi : step->teardown.multi;
196 /* Single invocation for instance add/remove */
198 WARN_ON_ONCE(lastp && *lastp);
199 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
200 ret = cbm(cpu, node);
201 trace_cpuhp_exit(cpu, st->state, state, ret);
205 /* State transition. Invoke on all instances */
207 hlist_for_each(node, &step->list) {
208 if (lastp && node == *lastp)
211 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
212 ret = cbm(cpu, node);
213 trace_cpuhp_exit(cpu, st->state, state, ret);
227 /* Rollback the instances if one failed */
228 cbm = !bringup ? step->startup.multi : step->teardown.multi;
232 hlist_for_each(node, &step->list) {
236 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
237 ret = cbm(cpu, node);
238 trace_cpuhp_exit(cpu, st->state, state, ret);
240 * Rollback must not fail,
248 static bool cpuhp_is_ap_state(enum cpuhp_state state)
251 * The extra check for CPUHP_TEARDOWN_CPU is only for documentation
252 * purposes as that state is handled explicitly in cpu_down.
254 return state > CPUHP_BRINGUP_CPU && state != CPUHP_TEARDOWN_CPU;
257 static inline void wait_for_ap_thread(struct cpuhp_cpu_state *st, bool bringup)
259 struct completion *done = bringup ? &st->done_up : &st->done_down;
260 wait_for_completion(done);
263 static inline void complete_ap_thread(struct cpuhp_cpu_state *st, bool bringup)
265 struct completion *done = bringup ? &st->done_up : &st->done_down;
270 * The former STARTING/DYING states, ran with IRQs disabled and must not fail.
272 static bool cpuhp_is_atomic_state(enum cpuhp_state state)
274 return CPUHP_AP_IDLE_DEAD <= state && state < CPUHP_AP_ONLINE;
277 /* Serializes the updates to cpu_online_mask, cpu_present_mask */
278 static DEFINE_MUTEX(cpu_add_remove_lock);
279 bool cpuhp_tasks_frozen;
280 EXPORT_SYMBOL_GPL(cpuhp_tasks_frozen);
283 * The following two APIs (cpu_maps_update_begin/done) must be used when
284 * attempting to serialize the updates to cpu_online_mask & cpu_present_mask.
286 void cpu_maps_update_begin(void)
288 mutex_lock(&cpu_add_remove_lock);
291 void cpu_maps_update_done(void)
293 mutex_unlock(&cpu_add_remove_lock);
297 * If set, cpu_up and cpu_down will return -EBUSY and do nothing.
298 * Should always be manipulated under cpu_add_remove_lock
300 static int cpu_hotplug_disabled;
302 #ifdef CONFIG_HOTPLUG_CPU
304 DEFINE_STATIC_PERCPU_RWSEM(cpu_hotplug_lock);
306 void cpus_read_lock(void)
308 percpu_down_read(&cpu_hotplug_lock);
310 EXPORT_SYMBOL_GPL(cpus_read_lock);
312 int cpus_read_trylock(void)
314 return percpu_down_read_trylock(&cpu_hotplug_lock);
316 EXPORT_SYMBOL_GPL(cpus_read_trylock);
318 void cpus_read_unlock(void)
320 percpu_up_read(&cpu_hotplug_lock);
322 EXPORT_SYMBOL_GPL(cpus_read_unlock);
324 void cpus_write_lock(void)
326 percpu_down_write(&cpu_hotplug_lock);
329 void cpus_write_unlock(void)
331 percpu_up_write(&cpu_hotplug_lock);
334 void lockdep_assert_cpus_held(void)
337 * We can't have hotplug operations before userspace starts running,
338 * and some init codepaths will knowingly not take the hotplug lock.
339 * This is all valid, so mute lockdep until it makes sense to report
342 if (system_state < SYSTEM_RUNNING)
345 percpu_rwsem_assert_held(&cpu_hotplug_lock);
348 #ifdef CONFIG_LOCKDEP
349 int lockdep_is_cpus_held(void)
351 return percpu_rwsem_is_held(&cpu_hotplug_lock);
355 static void lockdep_acquire_cpus_lock(void)
357 rwsem_acquire(&cpu_hotplug_lock.dep_map, 0, 0, _THIS_IP_);
360 static void lockdep_release_cpus_lock(void)
362 rwsem_release(&cpu_hotplug_lock.dep_map, _THIS_IP_);
366 * Wait for currently running CPU hotplug operations to complete (if any) and
367 * disable future CPU hotplug (from sysfs). The 'cpu_add_remove_lock' protects
368 * the 'cpu_hotplug_disabled' flag. The same lock is also acquired by the
369 * hotplug path before performing hotplug operations. So acquiring that lock
370 * guarantees mutual exclusion from any currently running hotplug operations.
372 void cpu_hotplug_disable(void)
374 cpu_maps_update_begin();
375 cpu_hotplug_disabled++;
376 cpu_maps_update_done();
378 EXPORT_SYMBOL_GPL(cpu_hotplug_disable);
380 static void __cpu_hotplug_enable(void)
382 if (WARN_ONCE(!cpu_hotplug_disabled, "Unbalanced cpu hotplug enable\n"))
384 cpu_hotplug_disabled--;
387 void cpu_hotplug_enable(void)
389 cpu_maps_update_begin();
390 __cpu_hotplug_enable();
391 cpu_maps_update_done();
393 EXPORT_SYMBOL_GPL(cpu_hotplug_enable);
397 static void lockdep_acquire_cpus_lock(void)
401 static void lockdep_release_cpus_lock(void)
405 #endif /* CONFIG_HOTPLUG_CPU */
408 * Architectures that need SMT-specific errata handling during SMT hotplug
409 * should override this.
411 void __weak arch_smt_update(void) { }
413 #ifdef CONFIG_HOTPLUG_SMT
414 enum cpuhp_smt_control cpu_smt_control __read_mostly = CPU_SMT_ENABLED;
416 void __init cpu_smt_disable(bool force)
418 if (!cpu_smt_possible())
422 pr_info("SMT: Force disabled\n");
423 cpu_smt_control = CPU_SMT_FORCE_DISABLED;
425 pr_info("SMT: disabled\n");
426 cpu_smt_control = CPU_SMT_DISABLED;
431 * The decision whether SMT is supported can only be done after the full
432 * CPU identification. Called from architecture code.
434 void __init cpu_smt_check_topology(void)
436 if (!topology_smt_supported())
437 cpu_smt_control = CPU_SMT_NOT_SUPPORTED;
440 static int __init smt_cmdline_disable(char *str)
442 cpu_smt_disable(str && !strcmp(str, "force"));
445 early_param("nosmt", smt_cmdline_disable);
447 static inline bool cpu_smt_allowed(unsigned int cpu)
449 if (cpu_smt_control == CPU_SMT_ENABLED)
452 if (topology_is_primary_thread(cpu))
456 * On x86 it's required to boot all logical CPUs at least once so
457 * that the init code can get a chance to set CR4.MCE on each
458 * CPU. Otherwise, a broadcasted MCE observing CR4.MCE=0b on any
459 * core will shutdown the machine.
461 return !cpumask_test_cpu(cpu, &cpus_booted_once_mask);
464 /* Returns true if SMT is not supported of forcefully (irreversibly) disabled */
465 bool cpu_smt_possible(void)
467 return cpu_smt_control != CPU_SMT_FORCE_DISABLED &&
468 cpu_smt_control != CPU_SMT_NOT_SUPPORTED;
470 EXPORT_SYMBOL_GPL(cpu_smt_possible);
472 static inline bool cpu_smt_allowed(unsigned int cpu) { return true; }
475 static inline enum cpuhp_state
476 cpuhp_set_state(struct cpuhp_cpu_state *st, enum cpuhp_state target)
478 enum cpuhp_state prev_state = st->state;
479 bool bringup = st->state < target;
481 st->rollback = false;
486 st->bringup = bringup;
487 if (cpu_dying(st->cpu) != !bringup)
488 set_cpu_dying(st->cpu, !bringup);
494 cpuhp_reset_state(struct cpuhp_cpu_state *st, enum cpuhp_state prev_state)
496 bool bringup = !st->bringup;
498 st->target = prev_state;
501 * Already rolling back. No need invert the bringup value or to change
510 * If we have st->last we need to undo partial multi_instance of this
511 * state first. Otherwise start undo at the previous state.
520 st->bringup = bringup;
521 if (cpu_dying(st->cpu) != !bringup)
522 set_cpu_dying(st->cpu, !bringup);
525 /* Regular hotplug invocation of the AP hotplug thread */
526 static void __cpuhp_kick_ap(struct cpuhp_cpu_state *st)
528 if (!st->single && st->state == st->target)
533 * Make sure the above stores are visible before should_run becomes
534 * true. Paired with the mb() above in cpuhp_thread_fun()
537 st->should_run = true;
538 wake_up_process(st->thread);
539 wait_for_ap_thread(st, st->bringup);
542 static int cpuhp_kick_ap(struct cpuhp_cpu_state *st, enum cpuhp_state target)
544 enum cpuhp_state prev_state;
547 prev_state = cpuhp_set_state(st, target);
549 if ((ret = st->result)) {
550 cpuhp_reset_state(st, prev_state);
557 static int bringup_wait_for_ap(unsigned int cpu)
559 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
561 /* Wait for the CPU to reach CPUHP_AP_ONLINE_IDLE */
562 wait_for_ap_thread(st, true);
563 if (WARN_ON_ONCE((!cpu_online(cpu))))
566 /* Unpark the hotplug thread of the target cpu */
567 kthread_unpark(st->thread);
570 * SMT soft disabling on X86 requires to bring the CPU out of the
571 * BIOS 'wait for SIPI' state in order to set the CR4.MCE bit. The
572 * CPU marked itself as booted_once in notify_cpu_starting() so the
573 * cpu_smt_allowed() check will now return false if this is not the
576 if (!cpu_smt_allowed(cpu))
579 if (st->target <= CPUHP_AP_ONLINE_IDLE)
582 return cpuhp_kick_ap(st, st->target);
585 static int bringup_cpu(unsigned int cpu)
587 struct task_struct *idle = idle_thread_get(cpu);
591 * Some architectures have to walk the irq descriptors to
592 * setup the vector space for the cpu which comes online.
593 * Prevent irq alloc/free across the bringup.
597 /* Arch-specific enabling code. */
598 ret = __cpu_up(cpu, idle);
602 return bringup_wait_for_ap(cpu);
605 static int finish_cpu(unsigned int cpu)
607 struct task_struct *idle = idle_thread_get(cpu);
608 struct mm_struct *mm = idle->active_mm;
611 * idle_task_exit() will have switched to &init_mm, now
612 * clean up any remaining active_mm state.
615 idle->active_mm = &init_mm;
621 * Hotplug state machine related functions
625 * Get the next state to run. Empty ones will be skipped. Returns true if a
628 * st->state will be modified ahead of time, to match state_to_run, as if it
631 static bool cpuhp_next_state(bool bringup,
632 enum cpuhp_state *state_to_run,
633 struct cpuhp_cpu_state *st,
634 enum cpuhp_state target)
638 if (st->state >= target)
641 *state_to_run = ++st->state;
643 if (st->state <= target)
646 *state_to_run = st->state--;
649 if (!cpuhp_step_empty(bringup, cpuhp_get_step(*state_to_run)))
656 static int cpuhp_invoke_callback_range(bool bringup,
658 struct cpuhp_cpu_state *st,
659 enum cpuhp_state target)
661 enum cpuhp_state state;
664 while (cpuhp_next_state(bringup, &state, st, target)) {
665 err = cpuhp_invoke_callback(cpu, state, bringup, NULL, NULL);
673 static inline bool can_rollback_cpu(struct cpuhp_cpu_state *st)
675 if (IS_ENABLED(CONFIG_HOTPLUG_CPU))
678 * When CPU hotplug is disabled, then taking the CPU down is not
679 * possible because takedown_cpu() and the architecture and
680 * subsystem specific mechanisms are not available. So the CPU
681 * which would be completely unplugged again needs to stay around
682 * in the current state.
684 return st->state <= CPUHP_BRINGUP_CPU;
687 static int cpuhp_up_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
688 enum cpuhp_state target)
690 enum cpuhp_state prev_state = st->state;
693 ret = cpuhp_invoke_callback_range(true, cpu, st, target);
695 pr_debug("CPU UP failed (%d) CPU %u state %s (%d)\n",
696 ret, cpu, cpuhp_get_step(st->state)->name,
699 cpuhp_reset_state(st, prev_state);
700 if (can_rollback_cpu(st))
701 WARN_ON(cpuhp_invoke_callback_range(false, cpu, st,
708 * The cpu hotplug threads manage the bringup and teardown of the cpus
710 static void cpuhp_create(unsigned int cpu)
712 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
714 init_completion(&st->done_up);
715 init_completion(&st->done_down);
719 static int cpuhp_should_run(unsigned int cpu)
721 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
723 return st->should_run;
727 * Execute teardown/startup callbacks on the plugged cpu. Also used to invoke
728 * callbacks when a state gets [un]installed at runtime.
730 * Each invocation of this function by the smpboot thread does a single AP
733 * It has 3 modes of operation:
734 * - single: runs st->cb_state
735 * - up: runs ++st->state, while st->state < st->target
736 * - down: runs st->state--, while st->state > st->target
738 * When complete or on error, should_run is cleared and the completion is fired.
740 static void cpuhp_thread_fun(unsigned int cpu)
742 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
743 bool bringup = st->bringup;
744 enum cpuhp_state state;
746 if (WARN_ON_ONCE(!st->should_run))
750 * ACQUIRE for the cpuhp_should_run() load of ->should_run. Ensures
751 * that if we see ->should_run we also see the rest of the state.
756 * The BP holds the hotplug lock, but we're now running on the AP,
757 * ensure that anybody asserting the lock is held, will actually find
760 lockdep_acquire_cpus_lock();
761 cpuhp_lock_acquire(bringup);
764 state = st->cb_state;
765 st->should_run = false;
767 st->should_run = cpuhp_next_state(bringup, &state, st, st->target);
772 WARN_ON_ONCE(!cpuhp_is_ap_state(state));
774 if (cpuhp_is_atomic_state(state)) {
776 st->result = cpuhp_invoke_callback(cpu, state, bringup, st->node, &st->last);
780 * STARTING/DYING must not fail!
782 WARN_ON_ONCE(st->result);
784 st->result = cpuhp_invoke_callback(cpu, state, bringup, st->node, &st->last);
789 * If we fail on a rollback, we're up a creek without no
790 * paddle, no way forward, no way back. We loose, thanks for
793 WARN_ON_ONCE(st->rollback);
794 st->should_run = false;
798 cpuhp_lock_release(bringup);
799 lockdep_release_cpus_lock();
802 complete_ap_thread(st, bringup);
805 /* Invoke a single callback on a remote cpu */
807 cpuhp_invoke_ap_callback(int cpu, enum cpuhp_state state, bool bringup,
808 struct hlist_node *node)
810 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
813 if (!cpu_online(cpu))
816 cpuhp_lock_acquire(false);
817 cpuhp_lock_release(false);
819 cpuhp_lock_acquire(true);
820 cpuhp_lock_release(true);
823 * If we are up and running, use the hotplug thread. For early calls
824 * we invoke the thread function directly.
827 return cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
829 st->rollback = false;
833 st->bringup = bringup;
834 st->cb_state = state;
840 * If we failed and did a partial, do a rollback.
842 if ((ret = st->result) && st->last) {
844 st->bringup = !bringup;
850 * Clean up the leftovers so the next hotplug operation wont use stale
853 st->node = st->last = NULL;
857 static int cpuhp_kick_ap_work(unsigned int cpu)
859 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
860 enum cpuhp_state prev_state = st->state;
863 cpuhp_lock_acquire(false);
864 cpuhp_lock_release(false);
866 cpuhp_lock_acquire(true);
867 cpuhp_lock_release(true);
869 trace_cpuhp_enter(cpu, st->target, prev_state, cpuhp_kick_ap_work);
870 ret = cpuhp_kick_ap(st, st->target);
871 trace_cpuhp_exit(cpu, st->state, prev_state, ret);
876 static struct smp_hotplug_thread cpuhp_threads = {
877 .store = &cpuhp_state.thread,
878 .create = &cpuhp_create,
879 .thread_should_run = cpuhp_should_run,
880 .thread_fn = cpuhp_thread_fun,
881 .thread_comm = "cpuhp/%u",
885 void __init cpuhp_threads_init(void)
887 BUG_ON(smpboot_register_percpu_thread(&cpuhp_threads));
888 kthread_unpark(this_cpu_read(cpuhp_state.thread));
893 * Serialize hotplug trainwrecks outside of the cpu_hotplug_lock
896 * The operation is still serialized against concurrent CPU hotplug via
897 * cpu_add_remove_lock, i.e. CPU map protection. But it is _not_
898 * serialized against other hotplug related activity like adding or
899 * removing of state callbacks and state instances, which invoke either the
900 * startup or the teardown callback of the affected state.
902 * This is required for subsystems which are unfixable vs. CPU hotplug and
903 * evade lock inversion problems by scheduling work which has to be
904 * completed _before_ cpu_up()/_cpu_down() returns.
906 * Don't even think about adding anything to this for any new code or even
907 * drivers. It's only purpose is to keep existing lock order trainwrecks
910 * For cpu_down() there might be valid reasons to finish cleanups which are
911 * not required to be done under cpu_hotplug_lock, but that's a different
912 * story and would be not invoked via this.
914 static void cpu_up_down_serialize_trainwrecks(bool tasks_frozen)
917 * cpusets delegate hotplug operations to a worker to "solve" the
918 * lock order problems. Wait for the worker, but only if tasks are
919 * _not_ frozen (suspend, hibernate) as that would wait forever.
921 * The wait is required because otherwise the hotplug operation
922 * returns with inconsistent state, which could even be observed in
923 * user space when a new CPU is brought up. The CPU plug uevent
924 * would be delivered and user space reacting on it would fail to
925 * move tasks to the newly plugged CPU up to the point where the
926 * work has finished because up to that point the newly plugged CPU
927 * is not assignable in cpusets/cgroups. On unplug that's not
928 * necessarily a visible issue, but it is still inconsistent state,
929 * which is the real problem which needs to be "fixed". This can't
930 * prevent the transient state between scheduling the work and
931 * returning from waiting for it.
934 cpuset_wait_for_hotplug();
937 #ifdef CONFIG_HOTPLUG_CPU
938 #ifndef arch_clear_mm_cpumask_cpu
939 #define arch_clear_mm_cpumask_cpu(cpu, mm) cpumask_clear_cpu(cpu, mm_cpumask(mm))
943 * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
946 * This function walks all processes, finds a valid mm struct for each one and
947 * then clears a corresponding bit in mm's cpumask. While this all sounds
948 * trivial, there are various non-obvious corner cases, which this function
949 * tries to solve in a safe manner.
951 * Also note that the function uses a somewhat relaxed locking scheme, so it may
952 * be called only for an already offlined CPU.
954 void clear_tasks_mm_cpumask(int cpu)
956 struct task_struct *p;
959 * This function is called after the cpu is taken down and marked
960 * offline, so its not like new tasks will ever get this cpu set in
961 * their mm mask. -- Peter Zijlstra
962 * Thus, we may use rcu_read_lock() here, instead of grabbing
963 * full-fledged tasklist_lock.
965 WARN_ON(cpu_online(cpu));
967 for_each_process(p) {
968 struct task_struct *t;
971 * Main thread might exit, but other threads may still have
972 * a valid mm. Find one.
974 t = find_lock_task_mm(p);
977 arch_clear_mm_cpumask_cpu(cpu, t->mm);
983 /* Take this CPU down. */
984 static int take_cpu_down(void *_param)
986 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
987 enum cpuhp_state target = max((int)st->target, CPUHP_AP_OFFLINE);
988 int err, cpu = smp_processor_id();
991 /* Ensure this CPU doesn't handle any more interrupts. */
992 err = __cpu_disable();
997 * Must be called from CPUHP_TEARDOWN_CPU, which means, as we are going
998 * down, that the current state is CPUHP_TEARDOWN_CPU - 1.
1000 WARN_ON(st->state != (CPUHP_TEARDOWN_CPU - 1));
1002 /* Invoke the former CPU_DYING callbacks */
1003 ret = cpuhp_invoke_callback_range(false, cpu, st, target);
1006 * DYING must not fail!
1010 /* Give up timekeeping duties */
1011 tick_handover_do_timer();
1012 /* Remove CPU from timer broadcasting */
1013 tick_offline_cpu(cpu);
1014 /* Park the stopper thread */
1015 stop_machine_park(cpu);
1019 static int takedown_cpu(unsigned int cpu)
1021 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1024 /* Park the smpboot threads */
1025 kthread_park(st->thread);
1028 * Prevent irq alloc/free while the dying cpu reorganizes the
1029 * interrupt affinities.
1034 * So now all preempt/rcu users must observe !cpu_active().
1036 err = stop_machine_cpuslocked(take_cpu_down, NULL, cpumask_of(cpu));
1038 /* CPU refused to die */
1039 irq_unlock_sparse();
1040 /* Unpark the hotplug thread so we can rollback there */
1041 kthread_unpark(st->thread);
1044 BUG_ON(cpu_online(cpu));
1047 * The teardown callback for CPUHP_AP_SCHED_STARTING will have removed
1048 * all runnable tasks from the CPU, there's only the idle task left now
1049 * that the migration thread is done doing the stop_machine thing.
1051 * Wait for the stop thread to go away.
1053 wait_for_ap_thread(st, false);
1054 BUG_ON(st->state != CPUHP_AP_IDLE_DEAD);
1056 /* Interrupts are moved away from the dying cpu, reenable alloc/free */
1057 irq_unlock_sparse();
1059 hotplug_cpu__broadcast_tick_pull(cpu);
1060 /* This actually kills the CPU. */
1063 tick_cleanup_dead_cpu(cpu);
1064 rcutree_migrate_callbacks(cpu);
1068 static void cpuhp_complete_idle_dead(void *arg)
1070 struct cpuhp_cpu_state *st = arg;
1072 complete_ap_thread(st, false);
1075 void cpuhp_report_idle_dead(void)
1077 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
1079 BUG_ON(st->state != CPUHP_AP_OFFLINE);
1080 rcu_report_dead(smp_processor_id());
1081 st->state = CPUHP_AP_IDLE_DEAD;
1083 * We cannot call complete after rcu_report_dead() so we delegate it
1086 smp_call_function_single(cpumask_first(cpu_online_mask),
1087 cpuhp_complete_idle_dead, st, 0);
1090 static int cpuhp_down_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
1091 enum cpuhp_state target)
1093 enum cpuhp_state prev_state = st->state;
1096 ret = cpuhp_invoke_callback_range(false, cpu, st, target);
1098 pr_debug("CPU DOWN failed (%d) CPU %u state %s (%d)\n",
1099 ret, cpu, cpuhp_get_step(st->state)->name,
1102 cpuhp_reset_state(st, prev_state);
1104 if (st->state < prev_state)
1105 WARN_ON(cpuhp_invoke_callback_range(true, cpu, st,
1112 /* Requires cpu_add_remove_lock to be held */
1113 static int __ref _cpu_down(unsigned int cpu, int tasks_frozen,
1114 enum cpuhp_state target)
1116 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1117 int prev_state, ret = 0;
1119 if (num_online_cpus() == 1)
1122 if (!cpu_present(cpu))
1127 cpuhp_tasks_frozen = tasks_frozen;
1129 prev_state = cpuhp_set_state(st, target);
1131 * If the current CPU state is in the range of the AP hotplug thread,
1132 * then we need to kick the thread.
1134 if (st->state > CPUHP_TEARDOWN_CPU) {
1135 st->target = max((int)target, CPUHP_TEARDOWN_CPU);
1136 ret = cpuhp_kick_ap_work(cpu);
1138 * The AP side has done the error rollback already. Just
1139 * return the error code..
1145 * We might have stopped still in the range of the AP hotplug
1146 * thread. Nothing to do anymore.
1148 if (st->state > CPUHP_TEARDOWN_CPU)
1151 st->target = target;
1154 * The AP brought itself down to CPUHP_TEARDOWN_CPU. So we need
1155 * to do the further cleanups.
1157 ret = cpuhp_down_callbacks(cpu, st, target);
1158 if (ret && st->state < prev_state) {
1159 if (st->state == CPUHP_TEARDOWN_CPU) {
1160 cpuhp_reset_state(st, prev_state);
1161 __cpuhp_kick_ap(st);
1163 WARN(1, "DEAD callback error for CPU%d", cpu);
1168 cpus_write_unlock();
1170 * Do post unplug cleanup. This is still protected against
1171 * concurrent CPU hotplug via cpu_add_remove_lock.
1173 lockup_detector_cleanup();
1175 cpu_up_down_serialize_trainwrecks(tasks_frozen);
1179 static int cpu_down_maps_locked(unsigned int cpu, enum cpuhp_state target)
1181 if (cpu_hotplug_disabled)
1183 return _cpu_down(cpu, 0, target);
1186 static int cpu_down(unsigned int cpu, enum cpuhp_state target)
1190 cpu_maps_update_begin();
1191 err = cpu_down_maps_locked(cpu, target);
1192 cpu_maps_update_done();
1197 * cpu_device_down - Bring down a cpu device
1198 * @dev: Pointer to the cpu device to offline
1200 * This function is meant to be used by device core cpu subsystem only.
1202 * Other subsystems should use remove_cpu() instead.
1204 * Return: %0 on success or a negative errno code
1206 int cpu_device_down(struct device *dev)
1208 return cpu_down(dev->id, CPUHP_OFFLINE);
1211 int remove_cpu(unsigned int cpu)
1215 lock_device_hotplug();
1216 ret = device_offline(get_cpu_device(cpu));
1217 unlock_device_hotplug();
1221 EXPORT_SYMBOL_GPL(remove_cpu);
1223 void smp_shutdown_nonboot_cpus(unsigned int primary_cpu)
1228 cpu_maps_update_begin();
1231 * Make certain the cpu I'm about to reboot on is online.
1233 * This is inline to what migrate_to_reboot_cpu() already do.
1235 if (!cpu_online(primary_cpu))
1236 primary_cpu = cpumask_first(cpu_online_mask);
1238 for_each_online_cpu(cpu) {
1239 if (cpu == primary_cpu)
1242 error = cpu_down_maps_locked(cpu, CPUHP_OFFLINE);
1244 pr_err("Failed to offline CPU%d - error=%d",
1251 * Ensure all but the reboot CPU are offline.
1253 BUG_ON(num_online_cpus() > 1);
1256 * Make sure the CPUs won't be enabled by someone else after this
1257 * point. Kexec will reboot to a new kernel shortly resetting
1258 * everything along the way.
1260 cpu_hotplug_disabled++;
1262 cpu_maps_update_done();
1266 #define takedown_cpu NULL
1267 #endif /*CONFIG_HOTPLUG_CPU*/
1270 * notify_cpu_starting(cpu) - Invoke the callbacks on the starting CPU
1271 * @cpu: cpu that just started
1273 * It must be called by the arch code on the new cpu, before the new cpu
1274 * enables interrupts and before the "boot" cpu returns from __cpu_up().
1276 void notify_cpu_starting(unsigned int cpu)
1278 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1279 enum cpuhp_state target = min((int)st->target, CPUHP_AP_ONLINE);
1282 rcu_cpu_starting(cpu); /* Enables RCU usage on this CPU. */
1283 cpumask_set_cpu(cpu, &cpus_booted_once_mask);
1284 ret = cpuhp_invoke_callback_range(true, cpu, st, target);
1287 * STARTING must not fail!
1293 * Called from the idle task. Wake up the controlling task which brings the
1294 * hotplug thread of the upcoming CPU up and then delegates the rest of the
1295 * online bringup to the hotplug thread.
1297 void cpuhp_online_idle(enum cpuhp_state state)
1299 struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
1301 /* Happens for the boot cpu */
1302 if (state != CPUHP_AP_ONLINE_IDLE)
1306 * Unpart the stopper thread before we start the idle loop (and start
1307 * scheduling); this ensures the stopper task is always available.
1309 stop_machine_unpark(smp_processor_id());
1311 st->state = CPUHP_AP_ONLINE_IDLE;
1312 complete_ap_thread(st, true);
1315 /* Requires cpu_add_remove_lock to be held */
1316 static int _cpu_up(unsigned int cpu, int tasks_frozen, enum cpuhp_state target)
1318 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1319 struct task_struct *idle;
1324 if (!cpu_present(cpu)) {
1330 * The caller of cpu_up() might have raced with another
1331 * caller. Nothing to do.
1333 if (st->state >= target)
1336 if (st->state == CPUHP_OFFLINE) {
1337 /* Let it fail before we try to bring the cpu up */
1338 idle = idle_thread_get(cpu);
1340 ret = PTR_ERR(idle);
1345 cpuhp_tasks_frozen = tasks_frozen;
1347 cpuhp_set_state(st, target);
1349 * If the current CPU state is in the range of the AP hotplug thread,
1350 * then we need to kick the thread once more.
1352 if (st->state > CPUHP_BRINGUP_CPU) {
1353 ret = cpuhp_kick_ap_work(cpu);
1355 * The AP side has done the error rollback already. Just
1356 * return the error code..
1363 * Try to reach the target state. We max out on the BP at
1364 * CPUHP_BRINGUP_CPU. After that the AP hotplug thread is
1365 * responsible for bringing it up to the target state.
1367 target = min((int)target, CPUHP_BRINGUP_CPU);
1368 ret = cpuhp_up_callbacks(cpu, st, target);
1370 cpus_write_unlock();
1372 cpu_up_down_serialize_trainwrecks(tasks_frozen);
1376 static int cpu_up(unsigned int cpu, enum cpuhp_state target)
1380 if (!cpu_possible(cpu)) {
1381 pr_err("can't online cpu %d because it is not configured as may-hotadd at boot time\n",
1383 #if defined(CONFIG_IA64)
1384 pr_err("please check additional_cpus= boot parameter\n");
1389 err = try_online_node(cpu_to_node(cpu));
1393 cpu_maps_update_begin();
1395 if (cpu_hotplug_disabled) {
1399 if (!cpu_smt_allowed(cpu)) {
1404 err = _cpu_up(cpu, 0, target);
1406 cpu_maps_update_done();
1411 * cpu_device_up - Bring up a cpu device
1412 * @dev: Pointer to the cpu device to online
1414 * This function is meant to be used by device core cpu subsystem only.
1416 * Other subsystems should use add_cpu() instead.
1418 * Return: %0 on success or a negative errno code
1420 int cpu_device_up(struct device *dev)
1422 return cpu_up(dev->id, CPUHP_ONLINE);
1425 int add_cpu(unsigned int cpu)
1429 lock_device_hotplug();
1430 ret = device_online(get_cpu_device(cpu));
1431 unlock_device_hotplug();
1435 EXPORT_SYMBOL_GPL(add_cpu);
1438 * bringup_hibernate_cpu - Bring up the CPU that we hibernated on
1439 * @sleep_cpu: The cpu we hibernated on and should be brought up.
1441 * On some architectures like arm64, we can hibernate on any CPU, but on
1442 * wake up the CPU we hibernated on might be offline as a side effect of
1443 * using maxcpus= for example.
1445 * Return: %0 on success or a negative errno code
1447 int bringup_hibernate_cpu(unsigned int sleep_cpu)
1451 if (!cpu_online(sleep_cpu)) {
1452 pr_info("Hibernated on a CPU that is offline! Bringing CPU up.\n");
1453 ret = cpu_up(sleep_cpu, CPUHP_ONLINE);
1455 pr_err("Failed to bring hibernate-CPU up!\n");
1462 void bringup_nonboot_cpus(unsigned int setup_max_cpus)
1466 for_each_present_cpu(cpu) {
1467 if (num_online_cpus() >= setup_max_cpus)
1469 if (!cpu_online(cpu))
1470 cpu_up(cpu, CPUHP_ONLINE);
1474 #ifdef CONFIG_PM_SLEEP_SMP
1475 static cpumask_var_t frozen_cpus;
1477 int freeze_secondary_cpus(int primary)
1481 cpu_maps_update_begin();
1482 if (primary == -1) {
1483 primary = cpumask_first(cpu_online_mask);
1484 if (!housekeeping_cpu(primary, HK_FLAG_TIMER))
1485 primary = housekeeping_any_cpu(HK_FLAG_TIMER);
1487 if (!cpu_online(primary))
1488 primary = cpumask_first(cpu_online_mask);
1492 * We take down all of the non-boot CPUs in one shot to avoid races
1493 * with the userspace trying to use the CPU hotplug at the same time
1495 cpumask_clear(frozen_cpus);
1497 pr_info("Disabling non-boot CPUs ...\n");
1498 for_each_online_cpu(cpu) {
1502 if (pm_wakeup_pending()) {
1503 pr_info("Wakeup pending. Abort CPU freeze\n");
1508 trace_suspend_resume(TPS("CPU_OFF"), cpu, true);
1509 error = _cpu_down(cpu, 1, CPUHP_OFFLINE);
1510 trace_suspend_resume(TPS("CPU_OFF"), cpu, false);
1512 cpumask_set_cpu(cpu, frozen_cpus);
1514 pr_err("Error taking CPU%d down: %d\n", cpu, error);
1520 BUG_ON(num_online_cpus() > 1);
1522 pr_err("Non-boot CPUs are not disabled\n");
1525 * Make sure the CPUs won't be enabled by someone else. We need to do
1526 * this even in case of failure as all freeze_secondary_cpus() users are
1527 * supposed to do thaw_secondary_cpus() on the failure path.
1529 cpu_hotplug_disabled++;
1531 cpu_maps_update_done();
1535 void __weak arch_thaw_secondary_cpus_begin(void)
1539 void __weak arch_thaw_secondary_cpus_end(void)
1543 void thaw_secondary_cpus(void)
1547 /* Allow everyone to use the CPU hotplug again */
1548 cpu_maps_update_begin();
1549 __cpu_hotplug_enable();
1550 if (cpumask_empty(frozen_cpus))
1553 pr_info("Enabling non-boot CPUs ...\n");
1555 arch_thaw_secondary_cpus_begin();
1557 for_each_cpu(cpu, frozen_cpus) {
1558 trace_suspend_resume(TPS("CPU_ON"), cpu, true);
1559 error = _cpu_up(cpu, 1, CPUHP_ONLINE);
1560 trace_suspend_resume(TPS("CPU_ON"), cpu, false);
1562 pr_info("CPU%d is up\n", cpu);
1565 pr_warn("Error taking CPU%d up: %d\n", cpu, error);
1568 arch_thaw_secondary_cpus_end();
1570 cpumask_clear(frozen_cpus);
1572 cpu_maps_update_done();
1575 static int __init alloc_frozen_cpus(void)
1577 if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
1581 core_initcall(alloc_frozen_cpus);
1584 * When callbacks for CPU hotplug notifications are being executed, we must
1585 * ensure that the state of the system with respect to the tasks being frozen
1586 * or not, as reported by the notification, remains unchanged *throughout the
1587 * duration* of the execution of the callbacks.
1588 * Hence we need to prevent the freezer from racing with regular CPU hotplug.
1590 * This synchronization is implemented by mutually excluding regular CPU
1591 * hotplug and Suspend/Hibernate call paths by hooking onto the Suspend/
1592 * Hibernate notifications.
1595 cpu_hotplug_pm_callback(struct notifier_block *nb,
1596 unsigned long action, void *ptr)
1600 case PM_SUSPEND_PREPARE:
1601 case PM_HIBERNATION_PREPARE:
1602 cpu_hotplug_disable();
1605 case PM_POST_SUSPEND:
1606 case PM_POST_HIBERNATION:
1607 cpu_hotplug_enable();
1618 static int __init cpu_hotplug_pm_sync_init(void)
1621 * cpu_hotplug_pm_callback has higher priority than x86
1622 * bsp_pm_callback which depends on cpu_hotplug_pm_callback
1623 * to disable cpu hotplug to avoid cpu hotplug race.
1625 pm_notifier(cpu_hotplug_pm_callback, 0);
1628 core_initcall(cpu_hotplug_pm_sync_init);
1630 #endif /* CONFIG_PM_SLEEP_SMP */
1634 #endif /* CONFIG_SMP */
1636 /* Boot processor state steps */
1637 static struct cpuhp_step cpuhp_hp_states[] = {
1640 .startup.single = NULL,
1641 .teardown.single = NULL,
1644 [CPUHP_CREATE_THREADS]= {
1645 .name = "threads:prepare",
1646 .startup.single = smpboot_create_threads,
1647 .teardown.single = NULL,
1650 [CPUHP_PERF_PREPARE] = {
1651 .name = "perf:prepare",
1652 .startup.single = perf_event_init_cpu,
1653 .teardown.single = perf_event_exit_cpu,
1655 [CPUHP_WORKQUEUE_PREP] = {
1656 .name = "workqueue:prepare",
1657 .startup.single = workqueue_prepare_cpu,
1658 .teardown.single = NULL,
1660 [CPUHP_HRTIMERS_PREPARE] = {
1661 .name = "hrtimers:prepare",
1662 .startup.single = hrtimers_prepare_cpu,
1663 .teardown.single = hrtimers_dead_cpu,
1665 [CPUHP_SMPCFD_PREPARE] = {
1666 .name = "smpcfd:prepare",
1667 .startup.single = smpcfd_prepare_cpu,
1668 .teardown.single = smpcfd_dead_cpu,
1670 [CPUHP_RELAY_PREPARE] = {
1671 .name = "relay:prepare",
1672 .startup.single = relay_prepare_cpu,
1673 .teardown.single = NULL,
1675 [CPUHP_SLAB_PREPARE] = {
1676 .name = "slab:prepare",
1677 .startup.single = slab_prepare_cpu,
1678 .teardown.single = slab_dead_cpu,
1680 [CPUHP_RCUTREE_PREP] = {
1681 .name = "RCU/tree:prepare",
1682 .startup.single = rcutree_prepare_cpu,
1683 .teardown.single = rcutree_dead_cpu,
1686 * On the tear-down path, timers_dead_cpu() must be invoked
1687 * before blk_mq_queue_reinit_notify() from notify_dead(),
1688 * otherwise a RCU stall occurs.
1690 [CPUHP_TIMERS_PREPARE] = {
1691 .name = "timers:prepare",
1692 .startup.single = timers_prepare_cpu,
1693 .teardown.single = timers_dead_cpu,
1695 /* Kicks the plugged cpu into life */
1696 [CPUHP_BRINGUP_CPU] = {
1697 .name = "cpu:bringup",
1698 .startup.single = bringup_cpu,
1699 .teardown.single = finish_cpu,
1702 /* Final state before CPU kills itself */
1703 [CPUHP_AP_IDLE_DEAD] = {
1704 .name = "idle:dead",
1707 * Last state before CPU enters the idle loop to die. Transient state
1708 * for synchronization.
1710 [CPUHP_AP_OFFLINE] = {
1711 .name = "ap:offline",
1714 /* First state is scheduler control. Interrupts are disabled */
1715 [CPUHP_AP_SCHED_STARTING] = {
1716 .name = "sched:starting",
1717 .startup.single = sched_cpu_starting,
1718 .teardown.single = sched_cpu_dying,
1720 [CPUHP_AP_RCUTREE_DYING] = {
1721 .name = "RCU/tree:dying",
1722 .startup.single = NULL,
1723 .teardown.single = rcutree_dying_cpu,
1725 [CPUHP_AP_SMPCFD_DYING] = {
1726 .name = "smpcfd:dying",
1727 .startup.single = NULL,
1728 .teardown.single = smpcfd_dying_cpu,
1730 /* Entry state on starting. Interrupts enabled from here on. Transient
1731 * state for synchronsization */
1732 [CPUHP_AP_ONLINE] = {
1733 .name = "ap:online",
1736 * Handled on control processor until the plugged processor manages
1739 [CPUHP_TEARDOWN_CPU] = {
1740 .name = "cpu:teardown",
1741 .startup.single = NULL,
1742 .teardown.single = takedown_cpu,
1746 [CPUHP_AP_SCHED_WAIT_EMPTY] = {
1747 .name = "sched:waitempty",
1748 .startup.single = NULL,
1749 .teardown.single = sched_cpu_wait_empty,
1752 /* Handle smpboot threads park/unpark */
1753 [CPUHP_AP_SMPBOOT_THREADS] = {
1754 .name = "smpboot/threads:online",
1755 .startup.single = smpboot_unpark_threads,
1756 .teardown.single = smpboot_park_threads,
1758 [CPUHP_AP_IRQ_AFFINITY_ONLINE] = {
1759 .name = "irq/affinity:online",
1760 .startup.single = irq_affinity_online_cpu,
1761 .teardown.single = NULL,
1763 [CPUHP_AP_PERF_ONLINE] = {
1764 .name = "perf:online",
1765 .startup.single = perf_event_init_cpu,
1766 .teardown.single = perf_event_exit_cpu,
1768 [CPUHP_AP_WATCHDOG_ONLINE] = {
1769 .name = "lockup_detector:online",
1770 .startup.single = lockup_detector_online_cpu,
1771 .teardown.single = lockup_detector_offline_cpu,
1773 [CPUHP_AP_WORKQUEUE_ONLINE] = {
1774 .name = "workqueue:online",
1775 .startup.single = workqueue_online_cpu,
1776 .teardown.single = workqueue_offline_cpu,
1778 [CPUHP_AP_RCUTREE_ONLINE] = {
1779 .name = "RCU/tree:online",
1780 .startup.single = rcutree_online_cpu,
1781 .teardown.single = rcutree_offline_cpu,
1785 * The dynamically registered state space is here
1789 /* Last state is scheduler control setting the cpu active */
1790 [CPUHP_AP_ACTIVE] = {
1791 .name = "sched:active",
1792 .startup.single = sched_cpu_activate,
1793 .teardown.single = sched_cpu_deactivate,
1797 /* CPU is fully up and running. */
1800 .startup.single = NULL,
1801 .teardown.single = NULL,
1805 /* Sanity check for callbacks */
1806 static int cpuhp_cb_check(enum cpuhp_state state)
1808 if (state <= CPUHP_OFFLINE || state >= CPUHP_ONLINE)
1814 * Returns a free for dynamic slot assignment of the Online state. The states
1815 * are protected by the cpuhp_slot_states mutex and an empty slot is identified
1816 * by having no name assigned.
1818 static int cpuhp_reserve_state(enum cpuhp_state state)
1820 enum cpuhp_state i, end;
1821 struct cpuhp_step *step;
1824 case CPUHP_AP_ONLINE_DYN:
1825 step = cpuhp_hp_states + CPUHP_AP_ONLINE_DYN;
1826 end = CPUHP_AP_ONLINE_DYN_END;
1828 case CPUHP_BP_PREPARE_DYN:
1829 step = cpuhp_hp_states + CPUHP_BP_PREPARE_DYN;
1830 end = CPUHP_BP_PREPARE_DYN_END;
1836 for (i = state; i <= end; i++, step++) {
1840 WARN(1, "No more dynamic states available for CPU hotplug\n");
1844 static int cpuhp_store_callbacks(enum cpuhp_state state, const char *name,
1845 int (*startup)(unsigned int cpu),
1846 int (*teardown)(unsigned int cpu),
1847 bool multi_instance)
1849 /* (Un)Install the callbacks for further cpu hotplug operations */
1850 struct cpuhp_step *sp;
1854 * If name is NULL, then the state gets removed.
1856 * CPUHP_AP_ONLINE_DYN and CPUHP_BP_PREPARE_DYN are handed out on
1857 * the first allocation from these dynamic ranges, so the removal
1858 * would trigger a new allocation and clear the wrong (already
1859 * empty) state, leaving the callbacks of the to be cleared state
1860 * dangling, which causes wreckage on the next hotplug operation.
1862 if (name && (state == CPUHP_AP_ONLINE_DYN ||
1863 state == CPUHP_BP_PREPARE_DYN)) {
1864 ret = cpuhp_reserve_state(state);
1869 sp = cpuhp_get_step(state);
1870 if (name && sp->name)
1873 sp->startup.single = startup;
1874 sp->teardown.single = teardown;
1876 sp->multi_instance = multi_instance;
1877 INIT_HLIST_HEAD(&sp->list);
1881 static void *cpuhp_get_teardown_cb(enum cpuhp_state state)
1883 return cpuhp_get_step(state)->teardown.single;
1887 * Call the startup/teardown function for a step either on the AP or
1888 * on the current CPU.
1890 static int cpuhp_issue_call(int cpu, enum cpuhp_state state, bool bringup,
1891 struct hlist_node *node)
1893 struct cpuhp_step *sp = cpuhp_get_step(state);
1897 * If there's nothing to do, we done.
1898 * Relies on the union for multi_instance.
1900 if (cpuhp_step_empty(bringup, sp))
1903 * The non AP bound callbacks can fail on bringup. On teardown
1904 * e.g. module removal we crash for now.
1907 if (cpuhp_is_ap_state(state))
1908 ret = cpuhp_invoke_ap_callback(cpu, state, bringup, node);
1910 ret = cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
1912 ret = cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
1914 BUG_ON(ret && !bringup);
1919 * Called from __cpuhp_setup_state on a recoverable failure.
1921 * Note: The teardown callbacks for rollback are not allowed to fail!
1923 static void cpuhp_rollback_install(int failedcpu, enum cpuhp_state state,
1924 struct hlist_node *node)
1928 /* Roll back the already executed steps on the other cpus */
1929 for_each_present_cpu(cpu) {
1930 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1931 int cpustate = st->state;
1933 if (cpu >= failedcpu)
1936 /* Did we invoke the startup call on that cpu ? */
1937 if (cpustate >= state)
1938 cpuhp_issue_call(cpu, state, false, node);
1942 int __cpuhp_state_add_instance_cpuslocked(enum cpuhp_state state,
1943 struct hlist_node *node,
1946 struct cpuhp_step *sp;
1950 lockdep_assert_cpus_held();
1952 sp = cpuhp_get_step(state);
1953 if (sp->multi_instance == false)
1956 mutex_lock(&cpuhp_state_mutex);
1958 if (!invoke || !sp->startup.multi)
1962 * Try to call the startup callback for each present cpu
1963 * depending on the hotplug state of the cpu.
1965 for_each_present_cpu(cpu) {
1966 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1967 int cpustate = st->state;
1969 if (cpustate < state)
1972 ret = cpuhp_issue_call(cpu, state, true, node);
1974 if (sp->teardown.multi)
1975 cpuhp_rollback_install(cpu, state, node);
1981 hlist_add_head(node, &sp->list);
1983 mutex_unlock(&cpuhp_state_mutex);
1987 int __cpuhp_state_add_instance(enum cpuhp_state state, struct hlist_node *node,
1993 ret = __cpuhp_state_add_instance_cpuslocked(state, node, invoke);
1997 EXPORT_SYMBOL_GPL(__cpuhp_state_add_instance);
2000 * __cpuhp_setup_state_cpuslocked - Setup the callbacks for an hotplug machine state
2001 * @state: The state to setup
2002 * @name: Name of the step
2003 * @invoke: If true, the startup function is invoked for cpus where
2004 * cpu state >= @state
2005 * @startup: startup callback function
2006 * @teardown: teardown callback function
2007 * @multi_instance: State is set up for multiple instances which get
2010 * The caller needs to hold cpus read locked while calling this function.
2013 * Positive state number if @state is CPUHP_AP_ONLINE_DYN;
2014 * 0 for all other states
2015 * On failure: proper (negative) error code
2017 int __cpuhp_setup_state_cpuslocked(enum cpuhp_state state,
2018 const char *name, bool invoke,
2019 int (*startup)(unsigned int cpu),
2020 int (*teardown)(unsigned int cpu),
2021 bool multi_instance)
2026 lockdep_assert_cpus_held();
2028 if (cpuhp_cb_check(state) || !name)
2031 mutex_lock(&cpuhp_state_mutex);
2033 ret = cpuhp_store_callbacks(state, name, startup, teardown,
2036 dynstate = state == CPUHP_AP_ONLINE_DYN;
2037 if (ret > 0 && dynstate) {
2042 if (ret || !invoke || !startup)
2046 * Try to call the startup callback for each present cpu
2047 * depending on the hotplug state of the cpu.
2049 for_each_present_cpu(cpu) {
2050 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
2051 int cpustate = st->state;
2053 if (cpustate < state)
2056 ret = cpuhp_issue_call(cpu, state, true, NULL);
2059 cpuhp_rollback_install(cpu, state, NULL);
2060 cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
2065 mutex_unlock(&cpuhp_state_mutex);
2067 * If the requested state is CPUHP_AP_ONLINE_DYN, return the
2068 * dynamically allocated state in case of success.
2070 if (!ret && dynstate)
2074 EXPORT_SYMBOL(__cpuhp_setup_state_cpuslocked);
2076 int __cpuhp_setup_state(enum cpuhp_state state,
2077 const char *name, bool invoke,
2078 int (*startup)(unsigned int cpu),
2079 int (*teardown)(unsigned int cpu),
2080 bool multi_instance)
2085 ret = __cpuhp_setup_state_cpuslocked(state, name, invoke, startup,
2086 teardown, multi_instance);
2090 EXPORT_SYMBOL(__cpuhp_setup_state);
2092 int __cpuhp_state_remove_instance(enum cpuhp_state state,
2093 struct hlist_node *node, bool invoke)
2095 struct cpuhp_step *sp = cpuhp_get_step(state);
2098 BUG_ON(cpuhp_cb_check(state));
2100 if (!sp->multi_instance)
2104 mutex_lock(&cpuhp_state_mutex);
2106 if (!invoke || !cpuhp_get_teardown_cb(state))
2109 * Call the teardown callback for each present cpu depending
2110 * on the hotplug state of the cpu. This function is not
2111 * allowed to fail currently!
2113 for_each_present_cpu(cpu) {
2114 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
2115 int cpustate = st->state;
2117 if (cpustate >= state)
2118 cpuhp_issue_call(cpu, state, false, node);
2123 mutex_unlock(&cpuhp_state_mutex);
2128 EXPORT_SYMBOL_GPL(__cpuhp_state_remove_instance);
2131 * __cpuhp_remove_state_cpuslocked - Remove the callbacks for an hotplug machine state
2132 * @state: The state to remove
2133 * @invoke: If true, the teardown function is invoked for cpus where
2134 * cpu state >= @state
2136 * The caller needs to hold cpus read locked while calling this function.
2137 * The teardown callback is currently not allowed to fail. Think
2138 * about module removal!
2140 void __cpuhp_remove_state_cpuslocked(enum cpuhp_state state, bool invoke)
2142 struct cpuhp_step *sp = cpuhp_get_step(state);
2145 BUG_ON(cpuhp_cb_check(state));
2147 lockdep_assert_cpus_held();
2149 mutex_lock(&cpuhp_state_mutex);
2150 if (sp->multi_instance) {
2151 WARN(!hlist_empty(&sp->list),
2152 "Error: Removing state %d which has instances left.\n",
2157 if (!invoke || !cpuhp_get_teardown_cb(state))
2161 * Call the teardown callback for each present cpu depending
2162 * on the hotplug state of the cpu. This function is not
2163 * allowed to fail currently!
2165 for_each_present_cpu(cpu) {
2166 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
2167 int cpustate = st->state;
2169 if (cpustate >= state)
2170 cpuhp_issue_call(cpu, state, false, NULL);
2173 cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
2174 mutex_unlock(&cpuhp_state_mutex);
2176 EXPORT_SYMBOL(__cpuhp_remove_state_cpuslocked);
2178 void __cpuhp_remove_state(enum cpuhp_state state, bool invoke)
2181 __cpuhp_remove_state_cpuslocked(state, invoke);
2184 EXPORT_SYMBOL(__cpuhp_remove_state);
2186 #ifdef CONFIG_HOTPLUG_SMT
2187 static void cpuhp_offline_cpu_device(unsigned int cpu)
2189 struct device *dev = get_cpu_device(cpu);
2191 dev->offline = true;
2192 /* Tell user space about the state change */
2193 kobject_uevent(&dev->kobj, KOBJ_OFFLINE);
2196 static void cpuhp_online_cpu_device(unsigned int cpu)
2198 struct device *dev = get_cpu_device(cpu);
2200 dev->offline = false;
2201 /* Tell user space about the state change */
2202 kobject_uevent(&dev->kobj, KOBJ_ONLINE);
2205 int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval)
2209 cpu_maps_update_begin();
2210 for_each_online_cpu(cpu) {
2211 if (topology_is_primary_thread(cpu))
2213 ret = cpu_down_maps_locked(cpu, CPUHP_OFFLINE);
2217 * As this needs to hold the cpu maps lock it's impossible
2218 * to call device_offline() because that ends up calling
2219 * cpu_down() which takes cpu maps lock. cpu maps lock
2220 * needs to be held as this might race against in kernel
2221 * abusers of the hotplug machinery (thermal management).
2223 * So nothing would update device:offline state. That would
2224 * leave the sysfs entry stale and prevent onlining after
2225 * smt control has been changed to 'off' again. This is
2226 * called under the sysfs hotplug lock, so it is properly
2227 * serialized against the regular offline usage.
2229 cpuhp_offline_cpu_device(cpu);
2232 cpu_smt_control = ctrlval;
2233 cpu_maps_update_done();
2237 int cpuhp_smt_enable(void)
2241 cpu_maps_update_begin();
2242 cpu_smt_control = CPU_SMT_ENABLED;
2243 for_each_present_cpu(cpu) {
2244 /* Skip online CPUs and CPUs on offline nodes */
2245 if (cpu_online(cpu) || !node_online(cpu_to_node(cpu)))
2247 ret = _cpu_up(cpu, 0, CPUHP_ONLINE);
2250 /* See comment in cpuhp_smt_disable() */
2251 cpuhp_online_cpu_device(cpu);
2253 cpu_maps_update_done();
2258 #if defined(CONFIG_SYSFS) && defined(CONFIG_HOTPLUG_CPU)
2259 static ssize_t state_show(struct device *dev,
2260 struct device_attribute *attr, char *buf)
2262 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2264 return sprintf(buf, "%d\n", st->state);
2266 static DEVICE_ATTR_RO(state);
2268 static ssize_t target_store(struct device *dev, struct device_attribute *attr,
2269 const char *buf, size_t count)
2271 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2272 struct cpuhp_step *sp;
2275 ret = kstrtoint(buf, 10, &target);
2279 #ifdef CONFIG_CPU_HOTPLUG_STATE_CONTROL
2280 if (target < CPUHP_OFFLINE || target > CPUHP_ONLINE)
2283 if (target != CPUHP_OFFLINE && target != CPUHP_ONLINE)
2287 ret = lock_device_hotplug_sysfs();
2291 mutex_lock(&cpuhp_state_mutex);
2292 sp = cpuhp_get_step(target);
2293 ret = !sp->name || sp->cant_stop ? -EINVAL : 0;
2294 mutex_unlock(&cpuhp_state_mutex);
2298 if (st->state < target)
2299 ret = cpu_up(dev->id, target);
2301 ret = cpu_down(dev->id, target);
2303 unlock_device_hotplug();
2304 return ret ? ret : count;
2307 static ssize_t target_show(struct device *dev,
2308 struct device_attribute *attr, char *buf)
2310 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2312 return sprintf(buf, "%d\n", st->target);
2314 static DEVICE_ATTR_RW(target);
2316 static ssize_t fail_store(struct device *dev, struct device_attribute *attr,
2317 const char *buf, size_t count)
2319 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2320 struct cpuhp_step *sp;
2323 ret = kstrtoint(buf, 10, &fail);
2327 if (fail == CPUHP_INVALID) {
2332 if (fail < CPUHP_OFFLINE || fail > CPUHP_ONLINE)
2336 * Cannot fail STARTING/DYING callbacks.
2338 if (cpuhp_is_atomic_state(fail))
2342 * DEAD callbacks cannot fail...
2343 * ... neither can CPUHP_BRINGUP_CPU during hotunplug. The latter
2344 * triggering STARTING callbacks, a failure in this state would
2347 if (fail <= CPUHP_BRINGUP_CPU && st->state > CPUHP_BRINGUP_CPU)
2351 * Cannot fail anything that doesn't have callbacks.
2353 mutex_lock(&cpuhp_state_mutex);
2354 sp = cpuhp_get_step(fail);
2355 if (!sp->startup.single && !sp->teardown.single)
2357 mutex_unlock(&cpuhp_state_mutex);
2366 static ssize_t fail_show(struct device *dev,
2367 struct device_attribute *attr, char *buf)
2369 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2371 return sprintf(buf, "%d\n", st->fail);
2374 static DEVICE_ATTR_RW(fail);
2376 static struct attribute *cpuhp_cpu_attrs[] = {
2377 &dev_attr_state.attr,
2378 &dev_attr_target.attr,
2379 &dev_attr_fail.attr,
2383 static const struct attribute_group cpuhp_cpu_attr_group = {
2384 .attrs = cpuhp_cpu_attrs,
2389 static ssize_t states_show(struct device *dev,
2390 struct device_attribute *attr, char *buf)
2392 ssize_t cur, res = 0;
2395 mutex_lock(&cpuhp_state_mutex);
2396 for (i = CPUHP_OFFLINE; i <= CPUHP_ONLINE; i++) {
2397 struct cpuhp_step *sp = cpuhp_get_step(i);
2400 cur = sprintf(buf, "%3d: %s\n", i, sp->name);
2405 mutex_unlock(&cpuhp_state_mutex);
2408 static DEVICE_ATTR_RO(states);
2410 static struct attribute *cpuhp_cpu_root_attrs[] = {
2411 &dev_attr_states.attr,
2415 static const struct attribute_group cpuhp_cpu_root_attr_group = {
2416 .attrs = cpuhp_cpu_root_attrs,
2421 #ifdef CONFIG_HOTPLUG_SMT
2424 __store_smt_control(struct device *dev, struct device_attribute *attr,
2425 const char *buf, size_t count)
2429 if (sysfs_streq(buf, "on"))
2430 ctrlval = CPU_SMT_ENABLED;
2431 else if (sysfs_streq(buf, "off"))
2432 ctrlval = CPU_SMT_DISABLED;
2433 else if (sysfs_streq(buf, "forceoff"))
2434 ctrlval = CPU_SMT_FORCE_DISABLED;
2438 if (cpu_smt_control == CPU_SMT_FORCE_DISABLED)
2441 if (cpu_smt_control == CPU_SMT_NOT_SUPPORTED)
2444 ret = lock_device_hotplug_sysfs();
2448 if (ctrlval != cpu_smt_control) {
2450 case CPU_SMT_ENABLED:
2451 ret = cpuhp_smt_enable();
2453 case CPU_SMT_DISABLED:
2454 case CPU_SMT_FORCE_DISABLED:
2455 ret = cpuhp_smt_disable(ctrlval);
2460 unlock_device_hotplug();
2461 return ret ? ret : count;
2464 #else /* !CONFIG_HOTPLUG_SMT */
2466 __store_smt_control(struct device *dev, struct device_attribute *attr,
2467 const char *buf, size_t count)
2471 #endif /* CONFIG_HOTPLUG_SMT */
2473 static const char *smt_states[] = {
2474 [CPU_SMT_ENABLED] = "on",
2475 [CPU_SMT_DISABLED] = "off",
2476 [CPU_SMT_FORCE_DISABLED] = "forceoff",
2477 [CPU_SMT_NOT_SUPPORTED] = "notsupported",
2478 [CPU_SMT_NOT_IMPLEMENTED] = "notimplemented",
2481 static ssize_t control_show(struct device *dev,
2482 struct device_attribute *attr, char *buf)
2484 const char *state = smt_states[cpu_smt_control];
2486 return snprintf(buf, PAGE_SIZE - 2, "%s\n", state);
2489 static ssize_t control_store(struct device *dev, struct device_attribute *attr,
2490 const char *buf, size_t count)
2492 return __store_smt_control(dev, attr, buf, count);
2494 static DEVICE_ATTR_RW(control);
2496 static ssize_t active_show(struct device *dev,
2497 struct device_attribute *attr, char *buf)
2499 return snprintf(buf, PAGE_SIZE - 2, "%d\n", sched_smt_active());
2501 static DEVICE_ATTR_RO(active);
2503 static struct attribute *cpuhp_smt_attrs[] = {
2504 &dev_attr_control.attr,
2505 &dev_attr_active.attr,
2509 static const struct attribute_group cpuhp_smt_attr_group = {
2510 .attrs = cpuhp_smt_attrs,
2515 static int __init cpu_smt_sysfs_init(void)
2517 return sysfs_create_group(&cpu_subsys.dev_root->kobj,
2518 &cpuhp_smt_attr_group);
2521 static int __init cpuhp_sysfs_init(void)
2525 ret = cpu_smt_sysfs_init();
2529 ret = sysfs_create_group(&cpu_subsys.dev_root->kobj,
2530 &cpuhp_cpu_root_attr_group);
2534 for_each_possible_cpu(cpu) {
2535 struct device *dev = get_cpu_device(cpu);
2539 ret = sysfs_create_group(&dev->kobj, &cpuhp_cpu_attr_group);
2545 device_initcall(cpuhp_sysfs_init);
2546 #endif /* CONFIG_SYSFS && CONFIG_HOTPLUG_CPU */
2549 * cpu_bit_bitmap[] is a special, "compressed" data structure that
2550 * represents all NR_CPUS bits binary values of 1<<nr.
2552 * It is used by cpumask_of() to get a constant address to a CPU
2553 * mask value that has a single bit set only.
2556 /* cpu_bit_bitmap[0] is empty - so we can back into it */
2557 #define MASK_DECLARE_1(x) [x+1][0] = (1UL << (x))
2558 #define MASK_DECLARE_2(x) MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
2559 #define MASK_DECLARE_4(x) MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
2560 #define MASK_DECLARE_8(x) MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
2562 const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
2564 MASK_DECLARE_8(0), MASK_DECLARE_8(8),
2565 MASK_DECLARE_8(16), MASK_DECLARE_8(24),
2566 #if BITS_PER_LONG > 32
2567 MASK_DECLARE_8(32), MASK_DECLARE_8(40),
2568 MASK_DECLARE_8(48), MASK_DECLARE_8(56),
2571 EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
2573 const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
2574 EXPORT_SYMBOL(cpu_all_bits);
2576 #ifdef CONFIG_INIT_ALL_POSSIBLE
2577 struct cpumask __cpu_possible_mask __read_mostly
2580 struct cpumask __cpu_possible_mask __read_mostly;
2582 EXPORT_SYMBOL(__cpu_possible_mask);
2584 struct cpumask __cpu_online_mask __read_mostly;
2585 EXPORT_SYMBOL(__cpu_online_mask);
2587 struct cpumask __cpu_present_mask __read_mostly;
2588 EXPORT_SYMBOL(__cpu_present_mask);
2590 struct cpumask __cpu_active_mask __read_mostly;
2591 EXPORT_SYMBOL(__cpu_active_mask);
2593 struct cpumask __cpu_dying_mask __read_mostly;
2594 EXPORT_SYMBOL(__cpu_dying_mask);
2596 atomic_t __num_online_cpus __read_mostly;
2597 EXPORT_SYMBOL(__num_online_cpus);
2599 void init_cpu_present(const struct cpumask *src)
2601 cpumask_copy(&__cpu_present_mask, src);
2604 void init_cpu_possible(const struct cpumask *src)
2606 cpumask_copy(&__cpu_possible_mask, src);
2609 void init_cpu_online(const struct cpumask *src)
2611 cpumask_copy(&__cpu_online_mask, src);
2614 void set_cpu_online(unsigned int cpu, bool online)
2617 * atomic_inc/dec() is required to handle the horrid abuse of this
2618 * function by the reboot and kexec code which invoke it from
2619 * IPI/NMI broadcasts when shutting down CPUs. Invocation from
2620 * regular CPU hotplug is properly serialized.
2622 * Note, that the fact that __num_online_cpus is of type atomic_t
2623 * does not protect readers which are not serialized against
2624 * concurrent hotplug operations.
2627 if (!cpumask_test_and_set_cpu(cpu, &__cpu_online_mask))
2628 atomic_inc(&__num_online_cpus);
2630 if (cpumask_test_and_clear_cpu(cpu, &__cpu_online_mask))
2631 atomic_dec(&__num_online_cpus);
2636 * Activate the first processor.
2638 void __init boot_cpu_init(void)
2640 int cpu = smp_processor_id();
2642 /* Mark the boot cpu "present", "online" etc for SMP and UP case */
2643 set_cpu_online(cpu, true);
2644 set_cpu_active(cpu, true);
2645 set_cpu_present(cpu, true);
2646 set_cpu_possible(cpu, true);
2649 __boot_cpu_id = cpu;
2654 * Must be called _AFTER_ setting up the per_cpu areas
2656 void __init boot_cpu_hotplug_init(void)
2659 cpumask_set_cpu(smp_processor_id(), &cpus_booted_once_mask);
2661 this_cpu_write(cpuhp_state.state, CPUHP_ONLINE);
2665 * These are used for a global "mitigations=" cmdline option for toggling
2666 * optional CPU mitigations.
2668 enum cpu_mitigations {
2669 CPU_MITIGATIONS_OFF,
2670 CPU_MITIGATIONS_AUTO,
2671 CPU_MITIGATIONS_AUTO_NOSMT,
2674 static enum cpu_mitigations cpu_mitigations __ro_after_init =
2675 CPU_MITIGATIONS_AUTO;
2677 static int __init mitigations_parse_cmdline(char *arg)
2679 if (!strcmp(arg, "off"))
2680 cpu_mitigations = CPU_MITIGATIONS_OFF;
2681 else if (!strcmp(arg, "auto"))
2682 cpu_mitigations = CPU_MITIGATIONS_AUTO;
2683 else if (!strcmp(arg, "auto,nosmt"))
2684 cpu_mitigations = CPU_MITIGATIONS_AUTO_NOSMT;
2686 pr_crit("Unsupported mitigations=%s, system may still be vulnerable\n",
2691 early_param("mitigations", mitigations_parse_cmdline);
2693 /* mitigations=off */
2694 bool cpu_mitigations_off(void)
2696 return cpu_mitigations == CPU_MITIGATIONS_OFF;
2698 EXPORT_SYMBOL_GPL(cpu_mitigations_off);
2700 /* mitigations=auto,nosmt */
2701 bool cpu_mitigations_auto_nosmt(void)
2703 return cpu_mitigations == CPU_MITIGATIONS_AUTO_NOSMT;
2705 EXPORT_SYMBOL_GPL(cpu_mitigations_auto_nosmt);