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>
26 /* Serializes the updates to cpu_online_mask, cpu_present_mask */
27 static DEFINE_MUTEX(cpu_add_remove_lock);
30 * The following two API's must be used when attempting
31 * to serialize the updates to cpu_online_mask, cpu_present_mask.
33 void cpu_maps_update_begin(void)
35 mutex_lock(&cpu_add_remove_lock);
38 void cpu_maps_update_done(void)
40 mutex_unlock(&cpu_add_remove_lock);
43 static RAW_NOTIFIER_HEAD(cpu_chain);
45 /* If set, cpu_up and cpu_down will return -EBUSY and do nothing.
46 * Should always be manipulated under cpu_add_remove_lock
48 static int cpu_hotplug_disabled;
50 #ifdef CONFIG_HOTPLUG_CPU
53 struct task_struct *active_writer;
54 struct mutex lock; /* Synchronizes accesses to refcount, */
56 * Also blocks the new readers during
57 * an ongoing cpu hotplug operation.
61 .active_writer = NULL,
62 .lock = __MUTEX_INITIALIZER(cpu_hotplug.lock),
66 void get_online_cpus(void)
69 if (cpu_hotplug.active_writer == current)
71 mutex_lock(&cpu_hotplug.lock);
72 cpu_hotplug.refcount++;
73 mutex_unlock(&cpu_hotplug.lock);
76 EXPORT_SYMBOL_GPL(get_online_cpus);
78 void put_online_cpus(void)
80 if (cpu_hotplug.active_writer == current)
82 mutex_lock(&cpu_hotplug.lock);
84 if (WARN_ON(!cpu_hotplug.refcount))
85 cpu_hotplug.refcount++; /* try to fix things up */
87 if (!--cpu_hotplug.refcount && unlikely(cpu_hotplug.active_writer))
88 wake_up_process(cpu_hotplug.active_writer);
89 mutex_unlock(&cpu_hotplug.lock);
92 EXPORT_SYMBOL_GPL(put_online_cpus);
95 * This ensures that the hotplug operation can begin only when the
96 * refcount goes to zero.
98 * Note that during a cpu-hotplug operation, the new readers, if any,
99 * will be blocked by the cpu_hotplug.lock
101 * Since cpu_hotplug_begin() is always called after invoking
102 * cpu_maps_update_begin(), we can be sure that only one writer is active.
104 * Note that theoretically, there is a possibility of a livelock:
105 * - Refcount goes to zero, last reader wakes up the sleeping
107 * - Last reader unlocks the cpu_hotplug.lock.
108 * - A new reader arrives at this moment, bumps up the refcount.
109 * - The writer acquires the cpu_hotplug.lock finds the refcount
110 * non zero and goes to sleep again.
112 * However, this is very difficult to achieve in practice since
113 * get_online_cpus() not an api which is called all that often.
116 static void cpu_hotplug_begin(void)
118 cpu_hotplug.active_writer = current;
121 mutex_lock(&cpu_hotplug.lock);
122 if (likely(!cpu_hotplug.refcount))
124 __set_current_state(TASK_UNINTERRUPTIBLE);
125 mutex_unlock(&cpu_hotplug.lock);
130 static void cpu_hotplug_done(void)
132 cpu_hotplug.active_writer = NULL;
133 mutex_unlock(&cpu_hotplug.lock);
136 #else /* #if CONFIG_HOTPLUG_CPU */
137 static void cpu_hotplug_begin(void) {}
138 static void cpu_hotplug_done(void) {}
139 #endif /* #else #if CONFIG_HOTPLUG_CPU */
141 /* Need to know about CPUs going up/down? */
142 int __ref register_cpu_notifier(struct notifier_block *nb)
145 cpu_maps_update_begin();
146 ret = raw_notifier_chain_register(&cpu_chain, nb);
147 cpu_maps_update_done();
151 static int __cpu_notify(unsigned long val, void *v, int nr_to_call,
156 ret = __raw_notifier_call_chain(&cpu_chain, val, v, nr_to_call,
159 return notifier_to_errno(ret);
162 static int cpu_notify(unsigned long val, void *v)
164 return __cpu_notify(val, v, -1, NULL);
167 #ifdef CONFIG_HOTPLUG_CPU
169 static void cpu_notify_nofail(unsigned long val, void *v)
171 BUG_ON(cpu_notify(val, v));
173 EXPORT_SYMBOL(register_cpu_notifier);
175 void __ref unregister_cpu_notifier(struct notifier_block *nb)
177 cpu_maps_update_begin();
178 raw_notifier_chain_unregister(&cpu_chain, nb);
179 cpu_maps_update_done();
181 EXPORT_SYMBOL(unregister_cpu_notifier);
184 * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
187 * This function walks all processes, finds a valid mm struct for each one and
188 * then clears a corresponding bit in mm's cpumask. While this all sounds
189 * trivial, there are various non-obvious corner cases, which this function
190 * tries to solve in a safe manner.
192 * Also note that the function uses a somewhat relaxed locking scheme, so it may
193 * be called only for an already offlined CPU.
195 void clear_tasks_mm_cpumask(int cpu)
197 struct task_struct *p;
200 * This function is called after the cpu is taken down and marked
201 * offline, so its not like new tasks will ever get this cpu set in
202 * their mm mask. -- Peter Zijlstra
203 * Thus, we may use rcu_read_lock() here, instead of grabbing
204 * full-fledged tasklist_lock.
206 WARN_ON(cpu_online(cpu));
208 for_each_process(p) {
209 struct task_struct *t;
212 * Main thread might exit, but other threads may still have
213 * a valid mm. Find one.
215 t = find_lock_task_mm(p);
218 cpumask_clear_cpu(cpu, mm_cpumask(t->mm));
224 static inline void check_for_tasks(int cpu)
226 struct task_struct *p;
227 cputime_t utime, stime;
229 write_lock_irq(&tasklist_lock);
230 for_each_process(p) {
231 task_cputime(p, &utime, &stime);
232 if (task_cpu(p) == cpu && p->state == TASK_RUNNING &&
234 printk(KERN_WARNING "Task %s (pid = %d) is on cpu %d "
235 "(state = %ld, flags = %x)\n",
236 p->comm, task_pid_nr(p), cpu,
239 write_unlock_irq(&tasklist_lock);
242 struct take_cpu_down_param {
247 /* Take this CPU down. */
248 static int __ref take_cpu_down(void *_param)
250 struct take_cpu_down_param *param = _param;
253 /* Ensure this CPU doesn't handle any more interrupts. */
254 err = __cpu_disable();
258 cpu_notify(CPU_DYING | param->mod, param->hcpu);
262 /* Requires cpu_add_remove_lock to be held */
263 static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
265 int err, nr_calls = 0;
266 void *hcpu = (void *)(long)cpu;
267 unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
268 struct take_cpu_down_param tcd_param = {
273 if (num_online_cpus() == 1)
276 if (!cpu_online(cpu))
281 err = __cpu_notify(CPU_DOWN_PREPARE | mod, hcpu, -1, &nr_calls);
284 __cpu_notify(CPU_DOWN_FAILED | mod, hcpu, nr_calls, NULL);
285 printk("%s: attempt to take down CPU %u failed\n",
289 smpboot_park_threads(cpu);
291 err = __stop_machine(take_cpu_down, &tcd_param, cpumask_of(cpu));
293 /* CPU didn't die: tell everyone. Can't complain. */
294 smpboot_unpark_threads(cpu);
295 cpu_notify_nofail(CPU_DOWN_FAILED | mod, hcpu);
298 BUG_ON(cpu_online(cpu));
301 * The migration_call() CPU_DYING callback will have removed all
302 * runnable tasks from the cpu, there's only the idle task left now
303 * that the migration thread is done doing the stop_machine thing.
305 * Wait for the stop thread to go away.
307 while (!idle_cpu(cpu))
310 /* This actually kills the CPU. */
313 /* CPU is completely dead: tell everyone. Too late to complain. */
314 cpu_notify_nofail(CPU_DEAD | mod, hcpu);
316 check_for_tasks(cpu);
321 cpu_notify_nofail(CPU_POST_DEAD | mod, hcpu);
325 int __ref cpu_down(unsigned int cpu)
329 cpu_maps_update_begin();
331 if (cpu_hotplug_disabled) {
336 err = _cpu_down(cpu, 0);
339 cpu_maps_update_done();
342 EXPORT_SYMBOL(cpu_down);
343 #endif /*CONFIG_HOTPLUG_CPU*/
345 /* Requires cpu_add_remove_lock to be held */
346 static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen)
348 int ret, nr_calls = 0;
349 void *hcpu = (void *)(long)cpu;
350 unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
351 struct task_struct *idle;
355 if (cpu_online(cpu) || !cpu_present(cpu)) {
360 idle = idle_thread_get(cpu);
366 ret = smpboot_create_threads(cpu);
370 ret = __cpu_notify(CPU_UP_PREPARE | mod, hcpu, -1, &nr_calls);
373 printk(KERN_WARNING "%s: attempt to bring up CPU %u failed\n",
378 /* Arch-specific enabling code. */
379 ret = __cpu_up(cpu, idle);
382 BUG_ON(!cpu_online(cpu));
384 /* Wake the per cpu threads */
385 smpboot_unpark_threads(cpu);
387 /* Now call notifier in preparation. */
388 cpu_notify(CPU_ONLINE | mod, hcpu);
392 __cpu_notify(CPU_UP_CANCELED | mod, hcpu, nr_calls, NULL);
399 int __cpuinit cpu_up(unsigned int cpu)
403 #ifdef CONFIG_MEMORY_HOTPLUG
408 if (!cpu_possible(cpu)) {
409 printk(KERN_ERR "can't online cpu %d because it is not "
410 "configured as may-hotadd at boot time\n", cpu);
411 #if defined(CONFIG_IA64)
412 printk(KERN_ERR "please check additional_cpus= boot "
418 #ifdef CONFIG_MEMORY_HOTPLUG
419 nid = cpu_to_node(cpu);
420 if (!node_online(nid)) {
421 err = mem_online_node(nid);
426 pgdat = NODE_DATA(nid);
429 "Can't online cpu %d due to NULL pgdat\n", cpu);
433 if (pgdat->node_zonelists->_zonerefs->zone == NULL) {
434 mutex_lock(&zonelists_mutex);
435 build_all_zonelists(NULL, NULL);
436 mutex_unlock(&zonelists_mutex);
440 cpu_maps_update_begin();
442 if (cpu_hotplug_disabled) {
447 err = _cpu_up(cpu, 0);
450 cpu_maps_update_done();
453 EXPORT_SYMBOL_GPL(cpu_up);
455 #ifdef CONFIG_PM_SLEEP_SMP
456 static cpumask_var_t frozen_cpus;
458 int disable_nonboot_cpus(void)
460 int cpu, first_cpu, error = 0;
462 cpu_maps_update_begin();
463 first_cpu = cpumask_first(cpu_online_mask);
465 * We take down all of the non-boot CPUs in one shot to avoid races
466 * with the userspace trying to use the CPU hotplug at the same time
468 cpumask_clear(frozen_cpus);
470 printk("Disabling non-boot CPUs ...\n");
471 for_each_online_cpu(cpu) {
472 if (cpu == first_cpu)
474 error = _cpu_down(cpu, 1);
476 cpumask_set_cpu(cpu, frozen_cpus);
478 printk(KERN_ERR "Error taking CPU%d down: %d\n",
485 BUG_ON(num_online_cpus() > 1);
486 /* Make sure the CPUs won't be enabled by someone else */
487 cpu_hotplug_disabled = 1;
489 printk(KERN_ERR "Non-boot CPUs are not disabled\n");
491 cpu_maps_update_done();
495 void __weak arch_enable_nonboot_cpus_begin(void)
499 void __weak arch_enable_nonboot_cpus_end(void)
503 void __ref enable_nonboot_cpus(void)
507 /* Allow everyone to use the CPU hotplug again */
508 cpu_maps_update_begin();
509 cpu_hotplug_disabled = 0;
510 if (cpumask_empty(frozen_cpus))
513 printk(KERN_INFO "Enabling non-boot CPUs ...\n");
515 arch_enable_nonboot_cpus_begin();
517 for_each_cpu(cpu, frozen_cpus) {
518 error = _cpu_up(cpu, 1);
520 printk(KERN_INFO "CPU%d is up\n", cpu);
523 printk(KERN_WARNING "Error taking CPU%d up: %d\n", cpu, error);
526 arch_enable_nonboot_cpus_end();
528 cpumask_clear(frozen_cpus);
530 cpu_maps_update_done();
533 static int __init alloc_frozen_cpus(void)
535 if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
539 core_initcall(alloc_frozen_cpus);
542 * Prevent regular CPU hotplug from racing with the freezer, by disabling CPU
543 * hotplug when tasks are about to be frozen. Also, don't allow the freezer
544 * to continue until any currently running CPU hotplug operation gets
546 * To modify the 'cpu_hotplug_disabled' flag, we need to acquire the
547 * 'cpu_add_remove_lock'. And this same lock is also taken by the regular
548 * CPU hotplug path and released only after it is complete. Thus, we
549 * (and hence the freezer) will block here until any currently running CPU
550 * hotplug operation gets completed.
552 void cpu_hotplug_disable_before_freeze(void)
554 cpu_maps_update_begin();
555 cpu_hotplug_disabled = 1;
556 cpu_maps_update_done();
561 * When tasks have been thawed, re-enable regular CPU hotplug (which had been
562 * disabled while beginning to freeze tasks).
564 void cpu_hotplug_enable_after_thaw(void)
566 cpu_maps_update_begin();
567 cpu_hotplug_disabled = 0;
568 cpu_maps_update_done();
572 * When callbacks for CPU hotplug notifications are being executed, we must
573 * ensure that the state of the system with respect to the tasks being frozen
574 * or not, as reported by the notification, remains unchanged *throughout the
575 * duration* of the execution of the callbacks.
576 * Hence we need to prevent the freezer from racing with regular CPU hotplug.
578 * This synchronization is implemented by mutually excluding regular CPU
579 * hotplug and Suspend/Hibernate call paths by hooking onto the Suspend/
580 * Hibernate notifications.
583 cpu_hotplug_pm_callback(struct notifier_block *nb,
584 unsigned long action, void *ptr)
588 case PM_SUSPEND_PREPARE:
589 case PM_HIBERNATION_PREPARE:
590 cpu_hotplug_disable_before_freeze();
593 case PM_POST_SUSPEND:
594 case PM_POST_HIBERNATION:
595 cpu_hotplug_enable_after_thaw();
606 static int __init cpu_hotplug_pm_sync_init(void)
609 * cpu_hotplug_pm_callback has higher priority than x86
610 * bsp_pm_callback which depends on cpu_hotplug_pm_callback
611 * to disable cpu hotplug to avoid cpu hotplug race.
613 pm_notifier(cpu_hotplug_pm_callback, 0);
616 core_initcall(cpu_hotplug_pm_sync_init);
618 #endif /* CONFIG_PM_SLEEP_SMP */
621 * notify_cpu_starting(cpu) - call the CPU_STARTING notifiers
622 * @cpu: cpu that just started
624 * This function calls the cpu_chain notifiers with CPU_STARTING.
625 * It must be called by the arch code on the new cpu, before the new cpu
626 * enables interrupts and before the "boot" cpu returns from __cpu_up().
628 void __cpuinit notify_cpu_starting(unsigned int cpu)
630 unsigned long val = CPU_STARTING;
632 #ifdef CONFIG_PM_SLEEP_SMP
633 if (frozen_cpus != NULL && cpumask_test_cpu(cpu, frozen_cpus))
634 val = CPU_STARTING_FROZEN;
635 #endif /* CONFIG_PM_SLEEP_SMP */
636 cpu_notify(val, (void *)(long)cpu);
639 #endif /* CONFIG_SMP */
642 * cpu_bit_bitmap[] is a special, "compressed" data structure that
643 * represents all NR_CPUS bits binary values of 1<<nr.
645 * It is used by cpumask_of() to get a constant address to a CPU
646 * mask value that has a single bit set only.
649 /* cpu_bit_bitmap[0] is empty - so we can back into it */
650 #define MASK_DECLARE_1(x) [x+1][0] = (1UL << (x))
651 #define MASK_DECLARE_2(x) MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
652 #define MASK_DECLARE_4(x) MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
653 #define MASK_DECLARE_8(x) MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
655 const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
657 MASK_DECLARE_8(0), MASK_DECLARE_8(8),
658 MASK_DECLARE_8(16), MASK_DECLARE_8(24),
659 #if BITS_PER_LONG > 32
660 MASK_DECLARE_8(32), MASK_DECLARE_8(40),
661 MASK_DECLARE_8(48), MASK_DECLARE_8(56),
664 EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
666 const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
667 EXPORT_SYMBOL(cpu_all_bits);
669 #ifdef CONFIG_INIT_ALL_POSSIBLE
670 static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly
673 static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly;
675 const struct cpumask *const cpu_possible_mask = to_cpumask(cpu_possible_bits);
676 EXPORT_SYMBOL(cpu_possible_mask);
678 static DECLARE_BITMAP(cpu_online_bits, CONFIG_NR_CPUS) __read_mostly;
679 const struct cpumask *const cpu_online_mask = to_cpumask(cpu_online_bits);
680 EXPORT_SYMBOL(cpu_online_mask);
682 static DECLARE_BITMAP(cpu_present_bits, CONFIG_NR_CPUS) __read_mostly;
683 const struct cpumask *const cpu_present_mask = to_cpumask(cpu_present_bits);
684 EXPORT_SYMBOL(cpu_present_mask);
686 static DECLARE_BITMAP(cpu_active_bits, CONFIG_NR_CPUS) __read_mostly;
687 const struct cpumask *const cpu_active_mask = to_cpumask(cpu_active_bits);
688 EXPORT_SYMBOL(cpu_active_mask);
690 void set_cpu_possible(unsigned int cpu, bool possible)
693 cpumask_set_cpu(cpu, to_cpumask(cpu_possible_bits));
695 cpumask_clear_cpu(cpu, to_cpumask(cpu_possible_bits));
698 void set_cpu_present(unsigned int cpu, bool present)
701 cpumask_set_cpu(cpu, to_cpumask(cpu_present_bits));
703 cpumask_clear_cpu(cpu, to_cpumask(cpu_present_bits));
706 void set_cpu_online(unsigned int cpu, bool online)
709 cpumask_set_cpu(cpu, to_cpumask(cpu_online_bits));
711 cpumask_clear_cpu(cpu, to_cpumask(cpu_online_bits));
714 void set_cpu_active(unsigned int cpu, bool active)
717 cpumask_set_cpu(cpu, to_cpumask(cpu_active_bits));
719 cpumask_clear_cpu(cpu, to_cpumask(cpu_active_bits));
722 void init_cpu_present(const struct cpumask *src)
724 cpumask_copy(to_cpumask(cpu_present_bits), src);
727 void init_cpu_possible(const struct cpumask *src)
729 cpumask_copy(to_cpumask(cpu_possible_bits), src);
732 void init_cpu_online(const struct cpumask *src)
734 cpumask_copy(to_cpumask(cpu_online_bits), src);