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 cpu)
279 struct task_struct *p;
280 cputime_t utime, stime;
282 write_lock_irq(&tasklist_lock);
283 for_each_process(p) {
284 task_cputime(p, &utime, &stime);
285 if (task_cpu(p) == cpu && p->state == TASK_RUNNING &&
287 printk(KERN_WARNING "Task %s (pid = %d) is on cpu %d "
288 "(state = %ld, flags = %x)\n",
289 p->comm, task_pid_nr(p), cpu,
292 write_unlock_irq(&tasklist_lock);
295 struct take_cpu_down_param {
300 /* Take this CPU down. */
301 static int __ref take_cpu_down(void *_param)
303 struct take_cpu_down_param *param = _param;
306 /* Ensure this CPU doesn't handle any more interrupts. */
307 err = __cpu_disable();
311 cpu_notify(CPU_DYING | param->mod, param->hcpu);
312 /* Park the stopper thread */
313 kthread_park(current);
317 /* Requires cpu_add_remove_lock to be held */
318 static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
320 int err, nr_calls = 0;
321 void *hcpu = (void *)(long)cpu;
322 unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
323 struct take_cpu_down_param tcd_param = {
328 if (num_online_cpus() == 1)
331 if (!cpu_online(cpu))
336 err = __cpu_notify(CPU_DOWN_PREPARE | mod, hcpu, -1, &nr_calls);
339 __cpu_notify(CPU_DOWN_FAILED | mod, hcpu, nr_calls, NULL);
340 printk("%s: attempt to take down CPU %u failed\n",
346 * By now we've cleared cpu_active_mask, wait for all preempt-disabled
347 * and RCU users of this state to go away such that all new such users
350 * For CONFIG_PREEMPT we have preemptible RCU and its sync_rcu() might
351 * not imply sync_sched(), so explicitly call both.
353 * Do sync before park smpboot threads to take care the rcu boost case.
355 #ifdef CONFIG_PREEMPT
360 smpboot_park_threads(cpu);
363 * So now all preempt/rcu users must observe !cpu_active().
366 err = __stop_machine(take_cpu_down, &tcd_param, cpumask_of(cpu));
368 /* CPU didn't die: tell everyone. Can't complain. */
369 smpboot_unpark_threads(cpu);
370 cpu_notify_nofail(CPU_DOWN_FAILED | mod, hcpu);
373 BUG_ON(cpu_online(cpu));
376 * The migration_call() CPU_DYING callback will have removed all
377 * runnable tasks from the cpu, there's only the idle task left now
378 * that the migration thread is done doing the stop_machine thing.
380 * Wait for the stop thread to go away.
382 while (!idle_cpu(cpu))
385 /* This actually kills the CPU. */
388 /* CPU is completely dead: tell everyone. Too late to complain. */
389 cpu_notify_nofail(CPU_DEAD | mod, hcpu);
391 check_for_tasks(cpu);
396 cpu_notify_nofail(CPU_POST_DEAD | mod, hcpu);
400 int __ref cpu_down(unsigned int cpu)
404 cpu_maps_update_begin();
406 if (cpu_hotplug_disabled) {
411 err = _cpu_down(cpu, 0);
414 cpu_maps_update_done();
417 EXPORT_SYMBOL(cpu_down);
418 #endif /*CONFIG_HOTPLUG_CPU*/
420 /* Requires cpu_add_remove_lock to be held */
421 static int _cpu_up(unsigned int cpu, int tasks_frozen)
423 int ret, nr_calls = 0;
424 void *hcpu = (void *)(long)cpu;
425 unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
426 struct task_struct *idle;
430 if (cpu_online(cpu) || !cpu_present(cpu)) {
435 idle = idle_thread_get(cpu);
441 ret = smpboot_create_threads(cpu);
445 ret = __cpu_notify(CPU_UP_PREPARE | mod, hcpu, -1, &nr_calls);
448 printk(KERN_WARNING "%s: attempt to bring up CPU %u failed\n",
453 /* Arch-specific enabling code. */
454 ret = __cpu_up(cpu, idle);
457 BUG_ON(!cpu_online(cpu));
459 /* Wake the per cpu threads */
460 smpboot_unpark_threads(cpu);
462 /* Now call notifier in preparation. */
463 cpu_notify(CPU_ONLINE | mod, hcpu);
467 __cpu_notify(CPU_UP_CANCELED | mod, hcpu, nr_calls, NULL);
474 int cpu_up(unsigned int cpu)
478 if (!cpu_possible(cpu)) {
479 printk(KERN_ERR "can't online cpu %d because it is not "
480 "configured as may-hotadd at boot time\n", cpu);
481 #if defined(CONFIG_IA64)
482 printk(KERN_ERR "please check additional_cpus= boot "
488 err = try_online_node(cpu_to_node(cpu));
492 cpu_maps_update_begin();
494 if (cpu_hotplug_disabled) {
499 err = _cpu_up(cpu, 0);
502 cpu_maps_update_done();
505 EXPORT_SYMBOL_GPL(cpu_up);
507 #ifdef CONFIG_PM_SLEEP_SMP
508 static cpumask_var_t frozen_cpus;
510 int disable_nonboot_cpus(void)
512 int cpu, first_cpu, error = 0;
514 cpu_maps_update_begin();
515 first_cpu = cpumask_first(cpu_online_mask);
517 * We take down all of the non-boot CPUs in one shot to avoid races
518 * with the userspace trying to use the CPU hotplug at the same time
520 cpumask_clear(frozen_cpus);
522 printk("Disabling non-boot CPUs ...\n");
523 for_each_online_cpu(cpu) {
524 if (cpu == first_cpu)
526 trace_suspend_resume(TPS("CPU_OFF"), cpu, true);
527 error = _cpu_down(cpu, 1);
528 trace_suspend_resume(TPS("CPU_OFF"), cpu, false);
530 cpumask_set_cpu(cpu, frozen_cpus);
532 printk(KERN_ERR "Error taking CPU%d down: %d\n",
539 BUG_ON(num_online_cpus() > 1);
540 /* Make sure the CPUs won't be enabled by someone else */
541 cpu_hotplug_disabled = 1;
543 printk(KERN_ERR "Non-boot CPUs are not disabled\n");
545 cpu_maps_update_done();
549 void __weak arch_enable_nonboot_cpus_begin(void)
553 void __weak arch_enable_nonboot_cpus_end(void)
557 void __ref enable_nonboot_cpus(void)
561 /* Allow everyone to use the CPU hotplug again */
562 cpu_maps_update_begin();
563 cpu_hotplug_disabled = 0;
564 if (cpumask_empty(frozen_cpus))
567 printk(KERN_INFO "Enabling non-boot CPUs ...\n");
569 arch_enable_nonboot_cpus_begin();
571 for_each_cpu(cpu, frozen_cpus) {
572 trace_suspend_resume(TPS("CPU_ON"), cpu, true);
573 error = _cpu_up(cpu, 1);
574 trace_suspend_resume(TPS("CPU_ON"), cpu, false);
576 printk(KERN_INFO "CPU%d is up\n", cpu);
579 printk(KERN_WARNING "Error taking CPU%d up: %d\n", cpu, error);
582 arch_enable_nonboot_cpus_end();
584 cpumask_clear(frozen_cpus);
586 cpu_maps_update_done();
589 static int __init alloc_frozen_cpus(void)
591 if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
595 core_initcall(alloc_frozen_cpus);
598 * When callbacks for CPU hotplug notifications are being executed, we must
599 * ensure that the state of the system with respect to the tasks being frozen
600 * or not, as reported by the notification, remains unchanged *throughout the
601 * duration* of the execution of the callbacks.
602 * Hence we need to prevent the freezer from racing with regular CPU hotplug.
604 * This synchronization is implemented by mutually excluding regular CPU
605 * hotplug and Suspend/Hibernate call paths by hooking onto the Suspend/
606 * Hibernate notifications.
609 cpu_hotplug_pm_callback(struct notifier_block *nb,
610 unsigned long action, void *ptr)
614 case PM_SUSPEND_PREPARE:
615 case PM_HIBERNATION_PREPARE:
616 cpu_hotplug_disable();
619 case PM_POST_SUSPEND:
620 case PM_POST_HIBERNATION:
621 cpu_hotplug_enable();
632 static int __init cpu_hotplug_pm_sync_init(void)
635 * cpu_hotplug_pm_callback has higher priority than x86
636 * bsp_pm_callback which depends on cpu_hotplug_pm_callback
637 * to disable cpu hotplug to avoid cpu hotplug race.
639 pm_notifier(cpu_hotplug_pm_callback, 0);
642 core_initcall(cpu_hotplug_pm_sync_init);
644 #endif /* CONFIG_PM_SLEEP_SMP */
647 * notify_cpu_starting(cpu) - call the CPU_STARTING notifiers
648 * @cpu: cpu that just started
650 * This function calls the cpu_chain notifiers with CPU_STARTING.
651 * It must be called by the arch code on the new cpu, before the new cpu
652 * enables interrupts and before the "boot" cpu returns from __cpu_up().
654 void notify_cpu_starting(unsigned int cpu)
656 unsigned long val = CPU_STARTING;
658 #ifdef CONFIG_PM_SLEEP_SMP
659 if (frozen_cpus != NULL && cpumask_test_cpu(cpu, frozen_cpus))
660 val = CPU_STARTING_FROZEN;
661 #endif /* CONFIG_PM_SLEEP_SMP */
662 cpu_notify(val, (void *)(long)cpu);
665 #endif /* CONFIG_SMP */
668 * cpu_bit_bitmap[] is a special, "compressed" data structure that
669 * represents all NR_CPUS bits binary values of 1<<nr.
671 * It is used by cpumask_of() to get a constant address to a CPU
672 * mask value that has a single bit set only.
675 /* cpu_bit_bitmap[0] is empty - so we can back into it */
676 #define MASK_DECLARE_1(x) [x+1][0] = (1UL << (x))
677 #define MASK_DECLARE_2(x) MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
678 #define MASK_DECLARE_4(x) MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
679 #define MASK_DECLARE_8(x) MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
681 const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
683 MASK_DECLARE_8(0), MASK_DECLARE_8(8),
684 MASK_DECLARE_8(16), MASK_DECLARE_8(24),
685 #if BITS_PER_LONG > 32
686 MASK_DECLARE_8(32), MASK_DECLARE_8(40),
687 MASK_DECLARE_8(48), MASK_DECLARE_8(56),
690 EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
692 const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
693 EXPORT_SYMBOL(cpu_all_bits);
695 #ifdef CONFIG_INIT_ALL_POSSIBLE
696 static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly
699 static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly;
701 const struct cpumask *const cpu_possible_mask = to_cpumask(cpu_possible_bits);
702 EXPORT_SYMBOL(cpu_possible_mask);
704 static DECLARE_BITMAP(cpu_online_bits, CONFIG_NR_CPUS) __read_mostly;
705 const struct cpumask *const cpu_online_mask = to_cpumask(cpu_online_bits);
706 EXPORT_SYMBOL(cpu_online_mask);
708 static DECLARE_BITMAP(cpu_present_bits, CONFIG_NR_CPUS) __read_mostly;
709 const struct cpumask *const cpu_present_mask = to_cpumask(cpu_present_bits);
710 EXPORT_SYMBOL(cpu_present_mask);
712 static DECLARE_BITMAP(cpu_active_bits, CONFIG_NR_CPUS) __read_mostly;
713 const struct cpumask *const cpu_active_mask = to_cpumask(cpu_active_bits);
714 EXPORT_SYMBOL(cpu_active_mask);
716 void set_cpu_possible(unsigned int cpu, bool possible)
719 cpumask_set_cpu(cpu, to_cpumask(cpu_possible_bits));
721 cpumask_clear_cpu(cpu, to_cpumask(cpu_possible_bits));
724 void set_cpu_present(unsigned int cpu, bool present)
727 cpumask_set_cpu(cpu, to_cpumask(cpu_present_bits));
729 cpumask_clear_cpu(cpu, to_cpumask(cpu_present_bits));
732 void set_cpu_online(unsigned int cpu, bool online)
735 cpumask_set_cpu(cpu, to_cpumask(cpu_online_bits));
736 cpumask_set_cpu(cpu, to_cpumask(cpu_active_bits));
738 cpumask_clear_cpu(cpu, to_cpumask(cpu_online_bits));
742 void set_cpu_active(unsigned int cpu, bool active)
745 cpumask_set_cpu(cpu, to_cpumask(cpu_active_bits));
747 cpumask_clear_cpu(cpu, to_cpumask(cpu_active_bits));
750 void init_cpu_present(const struct cpumask *src)
752 cpumask_copy(to_cpumask(cpu_present_bits), src);
755 void init_cpu_possible(const struct cpumask *src)
757 cpumask_copy(to_cpumask(cpu_possible_bits), src);
760 void init_cpu_online(const struct cpumask *src)
762 cpumask_copy(to_cpumask(cpu_online_bits), src);