2 * (C) 2001, 2002, 2003, 2004 Rusty Russell
4 * This code is licenced under the GPL.
6 #include <linux/proc_fs.h>
8 #include <linux/init.h>
9 #include <linux/notifier.h>
10 #include <linux/sched.h>
11 #include <linux/unistd.h>
12 #include <linux/cpu.h>
13 #include <linux/oom.h>
14 #include <linux/rcupdate.h>
15 #include <linux/export.h>
16 #include <linux/bug.h>
17 #include <linux/kthread.h>
18 #include <linux/stop_machine.h>
19 #include <linux/mutex.h>
20 #include <linux/gfp.h>
21 #include <linux/suspend.h>
22 #include <linux/lockdep.h>
23 #include <trace/events/power.h>
28 /* Serializes the updates to cpu_online_mask, cpu_present_mask */
29 static DEFINE_MUTEX(cpu_add_remove_lock);
32 * The following two APIs (cpu_maps_update_begin/done) must be used when
33 * attempting to serialize the updates to cpu_online_mask & cpu_present_mask.
34 * The APIs cpu_notifier_register_begin/done() must be used to protect CPU
35 * hotplug callback (un)registration performed using __register_cpu_notifier()
36 * or __unregister_cpu_notifier().
38 void cpu_maps_update_begin(void)
40 mutex_lock(&cpu_add_remove_lock);
42 EXPORT_SYMBOL(cpu_notifier_register_begin);
44 void cpu_maps_update_done(void)
46 mutex_unlock(&cpu_add_remove_lock);
48 EXPORT_SYMBOL(cpu_notifier_register_done);
50 static RAW_NOTIFIER_HEAD(cpu_chain);
52 /* If set, cpu_up and cpu_down will return -EBUSY and do nothing.
53 * Should always be manipulated under cpu_add_remove_lock
55 static int cpu_hotplug_disabled;
57 #ifdef CONFIG_HOTPLUG_CPU
60 struct task_struct *active_writer;
61 struct mutex lock; /* Synchronizes accesses to refcount, */
63 * Also blocks the new readers during
64 * an ongoing cpu hotplug operation.
68 #ifdef CONFIG_DEBUG_LOCK_ALLOC
69 struct lockdep_map dep_map;
72 .active_writer = NULL,
73 .lock = __MUTEX_INITIALIZER(cpu_hotplug.lock),
75 #ifdef CONFIG_DEBUG_LOCK_ALLOC
76 .dep_map = {.name = "cpu_hotplug.lock" },
80 /* Lockdep annotations for get/put_online_cpus() and cpu_hotplug_begin/end() */
81 #define cpuhp_lock_acquire_read() lock_map_acquire_read(&cpu_hotplug.dep_map)
82 #define cpuhp_lock_acquire() lock_map_acquire(&cpu_hotplug.dep_map)
83 #define cpuhp_lock_release() lock_map_release(&cpu_hotplug.dep_map)
85 void get_online_cpus(void)
88 if (cpu_hotplug.active_writer == current)
90 cpuhp_lock_acquire_read();
91 mutex_lock(&cpu_hotplug.lock);
92 cpu_hotplug.refcount++;
93 mutex_unlock(&cpu_hotplug.lock);
96 EXPORT_SYMBOL_GPL(get_online_cpus);
98 void put_online_cpus(void)
100 if (cpu_hotplug.active_writer == current)
102 mutex_lock(&cpu_hotplug.lock);
104 if (WARN_ON(!cpu_hotplug.refcount))
105 cpu_hotplug.refcount++; /* try to fix things up */
107 if (!--cpu_hotplug.refcount && unlikely(cpu_hotplug.active_writer))
108 wake_up_process(cpu_hotplug.active_writer);
109 mutex_unlock(&cpu_hotplug.lock);
110 cpuhp_lock_release();
113 EXPORT_SYMBOL_GPL(put_online_cpus);
116 * This ensures that the hotplug operation can begin only when the
117 * refcount goes to zero.
119 * Note that during a cpu-hotplug operation, the new readers, if any,
120 * will be blocked by the cpu_hotplug.lock
122 * Since cpu_hotplug_begin() is always called after invoking
123 * cpu_maps_update_begin(), we can be sure that only one writer is active.
125 * Note that theoretically, there is a possibility of a livelock:
126 * - Refcount goes to zero, last reader wakes up the sleeping
128 * - Last reader unlocks the cpu_hotplug.lock.
129 * - A new reader arrives at this moment, bumps up the refcount.
130 * - The writer acquires the cpu_hotplug.lock finds the refcount
131 * non zero and goes to sleep again.
133 * However, this is very difficult to achieve in practice since
134 * get_online_cpus() not an api which is called all that often.
137 void cpu_hotplug_begin(void)
139 cpu_hotplug.active_writer = current;
141 cpuhp_lock_acquire();
143 mutex_lock(&cpu_hotplug.lock);
144 if (likely(!cpu_hotplug.refcount))
146 __set_current_state(TASK_UNINTERRUPTIBLE);
147 mutex_unlock(&cpu_hotplug.lock);
152 void cpu_hotplug_done(void)
154 cpu_hotplug.active_writer = NULL;
155 mutex_unlock(&cpu_hotplug.lock);
156 cpuhp_lock_release();
160 * Wait for currently running CPU hotplug operations to complete (if any) and
161 * disable future CPU hotplug (from sysfs). The 'cpu_add_remove_lock' protects
162 * the 'cpu_hotplug_disabled' flag. The same lock is also acquired by the
163 * hotplug path before performing hotplug operations. So acquiring that lock
164 * guarantees mutual exclusion from any currently running hotplug operations.
166 void cpu_hotplug_disable(void)
168 cpu_maps_update_begin();
169 cpu_hotplug_disabled = 1;
170 cpu_maps_update_done();
173 void cpu_hotplug_enable(void)
175 cpu_maps_update_begin();
176 cpu_hotplug_disabled = 0;
177 cpu_maps_update_done();
180 #endif /* CONFIG_HOTPLUG_CPU */
182 /* Need to know about CPUs going up/down? */
183 int __ref register_cpu_notifier(struct notifier_block *nb)
186 cpu_maps_update_begin();
187 ret = raw_notifier_chain_register(&cpu_chain, nb);
188 cpu_maps_update_done();
192 int __ref __register_cpu_notifier(struct notifier_block *nb)
194 return raw_notifier_chain_register(&cpu_chain, nb);
197 static int __cpu_notify(unsigned long val, void *v, int nr_to_call,
202 ret = __raw_notifier_call_chain(&cpu_chain, val, v, nr_to_call,
205 return notifier_to_errno(ret);
208 static int cpu_notify(unsigned long val, void *v)
210 return __cpu_notify(val, v, -1, NULL);
213 #ifdef CONFIG_HOTPLUG_CPU
215 static void cpu_notify_nofail(unsigned long val, void *v)
217 BUG_ON(cpu_notify(val, v));
219 EXPORT_SYMBOL(register_cpu_notifier);
220 EXPORT_SYMBOL(__register_cpu_notifier);
222 void __ref unregister_cpu_notifier(struct notifier_block *nb)
224 cpu_maps_update_begin();
225 raw_notifier_chain_unregister(&cpu_chain, nb);
226 cpu_maps_update_done();
228 EXPORT_SYMBOL(unregister_cpu_notifier);
230 void __ref __unregister_cpu_notifier(struct notifier_block *nb)
232 raw_notifier_chain_unregister(&cpu_chain, nb);
234 EXPORT_SYMBOL(__unregister_cpu_notifier);
237 * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
240 * This function walks all processes, finds a valid mm struct for each one and
241 * then clears a corresponding bit in mm's cpumask. While this all sounds
242 * trivial, there are various non-obvious corner cases, which this function
243 * tries to solve in a safe manner.
245 * Also note that the function uses a somewhat relaxed locking scheme, so it may
246 * be called only for an already offlined CPU.
248 void clear_tasks_mm_cpumask(int cpu)
250 struct task_struct *p;
253 * This function is called after the cpu is taken down and marked
254 * offline, so its not like new tasks will ever get this cpu set in
255 * their mm mask. -- Peter Zijlstra
256 * Thus, we may use rcu_read_lock() here, instead of grabbing
257 * full-fledged tasklist_lock.
259 WARN_ON(cpu_online(cpu));
261 for_each_process(p) {
262 struct task_struct *t;
265 * Main thread might exit, but other threads may still have
266 * a valid mm. Find one.
268 t = find_lock_task_mm(p);
271 cpumask_clear_cpu(cpu, mm_cpumask(t->mm));
277 static inline void check_for_tasks(int dead_cpu)
279 struct task_struct *g, *p;
281 read_lock_irq(&tasklist_lock);
282 do_each_thread(g, p) {
286 * We do the check with unlocked task_rq(p)->lock.
287 * Order the reading to do not warn about a task,
288 * which was running on this cpu in the past, and
289 * it's just been woken on another cpu.
292 if (task_cpu(p) != dead_cpu)
295 pr_warn("Task %s (pid=%d) is on cpu %d (state=%ld, flags=%x)\n",
296 p->comm, task_pid_nr(p), dead_cpu, p->state, p->flags);
297 } while_each_thread(g, p);
298 read_unlock_irq(&tasklist_lock);
301 struct take_cpu_down_param {
306 /* Take this CPU down. */
307 static int __ref take_cpu_down(void *_param)
309 struct take_cpu_down_param *param = _param;
312 /* Ensure this CPU doesn't handle any more interrupts. */
313 err = __cpu_disable();
317 cpu_notify(CPU_DYING | param->mod, param->hcpu);
318 /* Park the stopper thread */
319 kthread_park(current);
323 /* Requires cpu_add_remove_lock to be held */
324 static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
326 int err, nr_calls = 0;
327 void *hcpu = (void *)(long)cpu;
328 unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
329 struct take_cpu_down_param tcd_param = {
334 if (num_online_cpus() == 1)
337 if (!cpu_online(cpu))
342 err = __cpu_notify(CPU_DOWN_PREPARE | mod, hcpu, -1, &nr_calls);
345 __cpu_notify(CPU_DOWN_FAILED | mod, hcpu, nr_calls, NULL);
346 pr_warn("%s: attempt to take down CPU %u failed\n",
352 * By now we've cleared cpu_active_mask, wait for all preempt-disabled
353 * and RCU users of this state to go away such that all new such users
356 * For CONFIG_PREEMPT we have preemptible RCU and its sync_rcu() might
357 * not imply sync_sched(), so explicitly call both.
359 * Do sync before park smpboot threads to take care the rcu boost case.
361 #ifdef CONFIG_PREEMPT
366 smpboot_park_threads(cpu);
369 * So now all preempt/rcu users must observe !cpu_active().
372 err = __stop_machine(take_cpu_down, &tcd_param, cpumask_of(cpu));
374 /* CPU didn't die: tell everyone. Can't complain. */
375 smpboot_unpark_threads(cpu);
376 cpu_notify_nofail(CPU_DOWN_FAILED | mod, hcpu);
379 BUG_ON(cpu_online(cpu));
382 * The migration_call() CPU_DYING callback will have removed all
383 * runnable tasks from the cpu, there's only the idle task left now
384 * that the migration thread is done doing the stop_machine thing.
386 * Wait for the stop thread to go away.
388 while (!idle_cpu(cpu))
391 /* This actually kills the CPU. */
394 /* CPU is completely dead: tell everyone. Too late to complain. */
395 cpu_notify_nofail(CPU_DEAD | mod, hcpu);
397 check_for_tasks(cpu);
402 cpu_notify_nofail(CPU_POST_DEAD | mod, hcpu);
406 int __ref cpu_down(unsigned int cpu)
410 cpu_maps_update_begin();
412 if (cpu_hotplug_disabled) {
417 err = _cpu_down(cpu, 0);
420 cpu_maps_update_done();
423 EXPORT_SYMBOL(cpu_down);
424 #endif /*CONFIG_HOTPLUG_CPU*/
426 /* Requires cpu_add_remove_lock to be held */
427 static int _cpu_up(unsigned int cpu, int tasks_frozen)
429 int ret, nr_calls = 0;
430 void *hcpu = (void *)(long)cpu;
431 unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
432 struct task_struct *idle;
436 if (cpu_online(cpu) || !cpu_present(cpu)) {
441 idle = idle_thread_get(cpu);
447 ret = smpboot_create_threads(cpu);
451 ret = __cpu_notify(CPU_UP_PREPARE | mod, hcpu, -1, &nr_calls);
454 pr_warn("%s: attempt to bring up CPU %u failed\n",
459 /* Arch-specific enabling code. */
460 ret = __cpu_up(cpu, idle);
463 BUG_ON(!cpu_online(cpu));
465 /* Wake the per cpu threads */
466 smpboot_unpark_threads(cpu);
468 /* Now call notifier in preparation. */
469 cpu_notify(CPU_ONLINE | mod, hcpu);
473 __cpu_notify(CPU_UP_CANCELED | mod, hcpu, nr_calls, NULL);
480 int cpu_up(unsigned int cpu)
484 if (!cpu_possible(cpu)) {
485 pr_err("can't online cpu %d because it is not configured as may-hotadd at boot time\n",
487 #if defined(CONFIG_IA64)
488 pr_err("please check additional_cpus= boot parameter\n");
493 err = try_online_node(cpu_to_node(cpu));
497 cpu_maps_update_begin();
499 if (cpu_hotplug_disabled) {
504 err = _cpu_up(cpu, 0);
507 cpu_maps_update_done();
510 EXPORT_SYMBOL_GPL(cpu_up);
512 #ifdef CONFIG_PM_SLEEP_SMP
513 static cpumask_var_t frozen_cpus;
515 int disable_nonboot_cpus(void)
517 int cpu, first_cpu, error = 0;
519 cpu_maps_update_begin();
520 first_cpu = cpumask_first(cpu_online_mask);
522 * We take down all of the non-boot CPUs in one shot to avoid races
523 * with the userspace trying to use the CPU hotplug at the same time
525 cpumask_clear(frozen_cpus);
527 pr_info("Disabling non-boot CPUs ...\n");
528 for_each_online_cpu(cpu) {
529 if (cpu == first_cpu)
531 trace_suspend_resume(TPS("CPU_OFF"), cpu, true);
532 error = _cpu_down(cpu, 1);
533 trace_suspend_resume(TPS("CPU_OFF"), cpu, false);
535 cpumask_set_cpu(cpu, frozen_cpus);
537 pr_err("Error taking CPU%d down: %d\n", cpu, error);
543 BUG_ON(num_online_cpus() > 1);
544 /* Make sure the CPUs won't be enabled by someone else */
545 cpu_hotplug_disabled = 1;
547 pr_err("Non-boot CPUs are not disabled\n");
549 cpu_maps_update_done();
553 void __weak arch_enable_nonboot_cpus_begin(void)
557 void __weak arch_enable_nonboot_cpus_end(void)
561 void __ref enable_nonboot_cpus(void)
565 /* Allow everyone to use the CPU hotplug again */
566 cpu_maps_update_begin();
567 cpu_hotplug_disabled = 0;
568 if (cpumask_empty(frozen_cpus))
571 pr_info("Enabling non-boot CPUs ...\n");
573 arch_enable_nonboot_cpus_begin();
575 for_each_cpu(cpu, frozen_cpus) {
576 trace_suspend_resume(TPS("CPU_ON"), cpu, true);
577 error = _cpu_up(cpu, 1);
578 trace_suspend_resume(TPS("CPU_ON"), cpu, false);
580 pr_info("CPU%d is up\n", cpu);
583 pr_warn("Error taking CPU%d up: %d\n", cpu, error);
586 arch_enable_nonboot_cpus_end();
588 cpumask_clear(frozen_cpus);
590 cpu_maps_update_done();
593 static int __init alloc_frozen_cpus(void)
595 if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
599 core_initcall(alloc_frozen_cpus);
602 * When callbacks for CPU hotplug notifications are being executed, we must
603 * ensure that the state of the system with respect to the tasks being frozen
604 * or not, as reported by the notification, remains unchanged *throughout the
605 * duration* of the execution of the callbacks.
606 * Hence we need to prevent the freezer from racing with regular CPU hotplug.
608 * This synchronization is implemented by mutually excluding regular CPU
609 * hotplug and Suspend/Hibernate call paths by hooking onto the Suspend/
610 * Hibernate notifications.
613 cpu_hotplug_pm_callback(struct notifier_block *nb,
614 unsigned long action, void *ptr)
618 case PM_SUSPEND_PREPARE:
619 case PM_HIBERNATION_PREPARE:
620 cpu_hotplug_disable();
623 case PM_POST_SUSPEND:
624 case PM_POST_HIBERNATION:
625 cpu_hotplug_enable();
636 static int __init cpu_hotplug_pm_sync_init(void)
639 * cpu_hotplug_pm_callback has higher priority than x86
640 * bsp_pm_callback which depends on cpu_hotplug_pm_callback
641 * to disable cpu hotplug to avoid cpu hotplug race.
643 pm_notifier(cpu_hotplug_pm_callback, 0);
646 core_initcall(cpu_hotplug_pm_sync_init);
648 #endif /* CONFIG_PM_SLEEP_SMP */
651 * notify_cpu_starting(cpu) - call the CPU_STARTING notifiers
652 * @cpu: cpu that just started
654 * This function calls the cpu_chain notifiers with CPU_STARTING.
655 * It must be called by the arch code on the new cpu, before the new cpu
656 * enables interrupts and before the "boot" cpu returns from __cpu_up().
658 void notify_cpu_starting(unsigned int cpu)
660 unsigned long val = CPU_STARTING;
662 #ifdef CONFIG_PM_SLEEP_SMP
663 if (frozen_cpus != NULL && cpumask_test_cpu(cpu, frozen_cpus))
664 val = CPU_STARTING_FROZEN;
665 #endif /* CONFIG_PM_SLEEP_SMP */
666 cpu_notify(val, (void *)(long)cpu);
669 #endif /* CONFIG_SMP */
672 * cpu_bit_bitmap[] is a special, "compressed" data structure that
673 * represents all NR_CPUS bits binary values of 1<<nr.
675 * It is used by cpumask_of() to get a constant address to a CPU
676 * mask value that has a single bit set only.
679 /* cpu_bit_bitmap[0] is empty - so we can back into it */
680 #define MASK_DECLARE_1(x) [x+1][0] = (1UL << (x))
681 #define MASK_DECLARE_2(x) MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
682 #define MASK_DECLARE_4(x) MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
683 #define MASK_DECLARE_8(x) MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
685 const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
687 MASK_DECLARE_8(0), MASK_DECLARE_8(8),
688 MASK_DECLARE_8(16), MASK_DECLARE_8(24),
689 #if BITS_PER_LONG > 32
690 MASK_DECLARE_8(32), MASK_DECLARE_8(40),
691 MASK_DECLARE_8(48), MASK_DECLARE_8(56),
694 EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
696 const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
697 EXPORT_SYMBOL(cpu_all_bits);
699 #ifdef CONFIG_INIT_ALL_POSSIBLE
700 static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly
703 static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly;
705 const struct cpumask *const cpu_possible_mask = to_cpumask(cpu_possible_bits);
706 EXPORT_SYMBOL(cpu_possible_mask);
708 static DECLARE_BITMAP(cpu_online_bits, CONFIG_NR_CPUS) __read_mostly;
709 const struct cpumask *const cpu_online_mask = to_cpumask(cpu_online_bits);
710 EXPORT_SYMBOL(cpu_online_mask);
712 static DECLARE_BITMAP(cpu_present_bits, CONFIG_NR_CPUS) __read_mostly;
713 const struct cpumask *const cpu_present_mask = to_cpumask(cpu_present_bits);
714 EXPORT_SYMBOL(cpu_present_mask);
716 static DECLARE_BITMAP(cpu_active_bits, CONFIG_NR_CPUS) __read_mostly;
717 const struct cpumask *const cpu_active_mask = to_cpumask(cpu_active_bits);
718 EXPORT_SYMBOL(cpu_active_mask);
720 void set_cpu_possible(unsigned int cpu, bool possible)
723 cpumask_set_cpu(cpu, to_cpumask(cpu_possible_bits));
725 cpumask_clear_cpu(cpu, to_cpumask(cpu_possible_bits));
728 void set_cpu_present(unsigned int cpu, bool present)
731 cpumask_set_cpu(cpu, to_cpumask(cpu_present_bits));
733 cpumask_clear_cpu(cpu, to_cpumask(cpu_present_bits));
736 void set_cpu_online(unsigned int cpu, bool online)
739 cpumask_set_cpu(cpu, to_cpumask(cpu_online_bits));
740 cpumask_set_cpu(cpu, to_cpumask(cpu_active_bits));
742 cpumask_clear_cpu(cpu, to_cpumask(cpu_online_bits));
746 void set_cpu_active(unsigned int cpu, bool active)
749 cpumask_set_cpu(cpu, to_cpumask(cpu_active_bits));
751 cpumask_clear_cpu(cpu, to_cpumask(cpu_active_bits));
754 void init_cpu_present(const struct cpumask *src)
756 cpumask_copy(to_cpumask(cpu_present_bits), src);
759 void init_cpu_possible(const struct cpumask *src)
761 cpumask_copy(to_cpumask(cpu_possible_bits), src);
764 void init_cpu_online(const struct cpumask *src)
766 cpumask_copy(to_cpumask(cpu_online_bits), src);