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 APIs (cpu_maps_update_begin/done) must be used when
31 * attempting to serialize the updates to cpu_online_mask & cpu_present_mask.
32 * The APIs cpu_notifier_register_begin/done() must be used to protect CPU
33 * hotplug callback (un)registration performed using __register_cpu_notifier()
34 * or __unregister_cpu_notifier().
36 void cpu_maps_update_begin(void)
38 mutex_lock(&cpu_add_remove_lock);
40 EXPORT_SYMBOL(cpu_notifier_register_begin);
42 void cpu_maps_update_done(void)
44 mutex_unlock(&cpu_add_remove_lock);
46 EXPORT_SYMBOL(cpu_notifier_register_done);
48 static RAW_NOTIFIER_HEAD(cpu_chain);
50 /* If set, cpu_up and cpu_down will return -EBUSY and do nothing.
51 * Should always be manipulated under cpu_add_remove_lock
53 static int cpu_hotplug_disabled;
55 #ifdef CONFIG_HOTPLUG_CPU
58 struct task_struct *active_writer;
59 struct mutex lock; /* Synchronizes accesses to refcount, */
61 * Also blocks the new readers during
62 * an ongoing cpu hotplug operation.
66 .active_writer = NULL,
67 .lock = __MUTEX_INITIALIZER(cpu_hotplug.lock),
71 void get_online_cpus(void)
74 if (cpu_hotplug.active_writer == current)
76 mutex_lock(&cpu_hotplug.lock);
77 cpu_hotplug.refcount++;
78 mutex_unlock(&cpu_hotplug.lock);
81 EXPORT_SYMBOL_GPL(get_online_cpus);
83 void put_online_cpus(void)
85 if (cpu_hotplug.active_writer == current)
87 mutex_lock(&cpu_hotplug.lock);
89 if (WARN_ON(!cpu_hotplug.refcount))
90 cpu_hotplug.refcount++; /* try to fix things up */
92 if (!--cpu_hotplug.refcount && unlikely(cpu_hotplug.active_writer))
93 wake_up_process(cpu_hotplug.active_writer);
94 mutex_unlock(&cpu_hotplug.lock);
97 EXPORT_SYMBOL_GPL(put_online_cpus);
100 * This ensures that the hotplug operation can begin only when the
101 * refcount goes to zero.
103 * Note that during a cpu-hotplug operation, the new readers, if any,
104 * will be blocked by the cpu_hotplug.lock
106 * Since cpu_hotplug_begin() is always called after invoking
107 * cpu_maps_update_begin(), we can be sure that only one writer is active.
109 * Note that theoretically, there is a possibility of a livelock:
110 * - Refcount goes to zero, last reader wakes up the sleeping
112 * - Last reader unlocks the cpu_hotplug.lock.
113 * - A new reader arrives at this moment, bumps up the refcount.
114 * - The writer acquires the cpu_hotplug.lock finds the refcount
115 * non zero and goes to sleep again.
117 * However, this is very difficult to achieve in practice since
118 * get_online_cpus() not an api which is called all that often.
121 static void cpu_hotplug_begin(void)
123 cpu_hotplug.active_writer = current;
126 mutex_lock(&cpu_hotplug.lock);
127 if (likely(!cpu_hotplug.refcount))
129 __set_current_state(TASK_UNINTERRUPTIBLE);
130 mutex_unlock(&cpu_hotplug.lock);
135 static void cpu_hotplug_done(void)
137 cpu_hotplug.active_writer = NULL;
138 mutex_unlock(&cpu_hotplug.lock);
142 * Wait for currently running CPU hotplug operations to complete (if any) and
143 * disable future CPU hotplug (from sysfs). The 'cpu_add_remove_lock' protects
144 * the 'cpu_hotplug_disabled' flag. The same lock is also acquired by the
145 * hotplug path before performing hotplug operations. So acquiring that lock
146 * guarantees mutual exclusion from any currently running hotplug operations.
148 void cpu_hotplug_disable(void)
150 cpu_maps_update_begin();
151 cpu_hotplug_disabled = 1;
152 cpu_maps_update_done();
155 void cpu_hotplug_enable(void)
157 cpu_maps_update_begin();
158 cpu_hotplug_disabled = 0;
159 cpu_maps_update_done();
162 #else /* #if CONFIG_HOTPLUG_CPU */
163 static void cpu_hotplug_begin(void) {}
164 static void cpu_hotplug_done(void) {}
165 #endif /* #else #if CONFIG_HOTPLUG_CPU */
167 /* Need to know about CPUs going up/down? */
168 int __ref register_cpu_notifier(struct notifier_block *nb)
171 cpu_maps_update_begin();
172 ret = raw_notifier_chain_register(&cpu_chain, nb);
173 cpu_maps_update_done();
177 int __ref __register_cpu_notifier(struct notifier_block *nb)
179 return raw_notifier_chain_register(&cpu_chain, nb);
182 static int __cpu_notify(unsigned long val, void *v, int nr_to_call,
187 ret = __raw_notifier_call_chain(&cpu_chain, val, v, nr_to_call,
190 return notifier_to_errno(ret);
193 static int cpu_notify(unsigned long val, void *v)
195 return __cpu_notify(val, v, -1, NULL);
198 #ifdef CONFIG_HOTPLUG_CPU
200 static void cpu_notify_nofail(unsigned long val, void *v)
202 BUG_ON(cpu_notify(val, v));
204 EXPORT_SYMBOL(register_cpu_notifier);
205 EXPORT_SYMBOL(__register_cpu_notifier);
207 void __ref unregister_cpu_notifier(struct notifier_block *nb)
209 cpu_maps_update_begin();
210 raw_notifier_chain_unregister(&cpu_chain, nb);
211 cpu_maps_update_done();
213 EXPORT_SYMBOL(unregister_cpu_notifier);
215 void __ref __unregister_cpu_notifier(struct notifier_block *nb)
217 raw_notifier_chain_unregister(&cpu_chain, nb);
219 EXPORT_SYMBOL(__unregister_cpu_notifier);
222 * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
225 * This function walks all processes, finds a valid mm struct for each one and
226 * then clears a corresponding bit in mm's cpumask. While this all sounds
227 * trivial, there are various non-obvious corner cases, which this function
228 * tries to solve in a safe manner.
230 * Also note that the function uses a somewhat relaxed locking scheme, so it may
231 * be called only for an already offlined CPU.
233 void clear_tasks_mm_cpumask(int cpu)
235 struct task_struct *p;
238 * This function is called after the cpu is taken down and marked
239 * offline, so its not like new tasks will ever get this cpu set in
240 * their mm mask. -- Peter Zijlstra
241 * Thus, we may use rcu_read_lock() here, instead of grabbing
242 * full-fledged tasklist_lock.
244 WARN_ON(cpu_online(cpu));
246 for_each_process(p) {
247 struct task_struct *t;
250 * Main thread might exit, but other threads may still have
251 * a valid mm. Find one.
253 t = find_lock_task_mm(p);
256 cpumask_clear_cpu(cpu, mm_cpumask(t->mm));
262 static inline void check_for_tasks(int cpu)
264 struct task_struct *p;
265 cputime_t utime, stime;
267 write_lock_irq(&tasklist_lock);
268 for_each_process(p) {
269 task_cputime(p, &utime, &stime);
270 if (task_cpu(p) == cpu && p->state == TASK_RUNNING &&
272 printk(KERN_WARNING "Task %s (pid = %d) is on cpu %d "
273 "(state = %ld, flags = %x)\n",
274 p->comm, task_pid_nr(p), cpu,
277 write_unlock_irq(&tasklist_lock);
280 struct take_cpu_down_param {
285 /* Take this CPU down. */
286 static int __ref take_cpu_down(void *_param)
288 struct take_cpu_down_param *param = _param;
291 /* Ensure this CPU doesn't handle any more interrupts. */
292 err = __cpu_disable();
296 cpu_notify(CPU_DYING | param->mod, param->hcpu);
297 /* Park the stopper thread */
298 kthread_park(current);
302 /* Requires cpu_add_remove_lock to be held */
303 static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
305 int err, nr_calls = 0;
306 void *hcpu = (void *)(long)cpu;
307 unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
308 struct take_cpu_down_param tcd_param = {
313 if (num_online_cpus() == 1)
316 if (!cpu_online(cpu))
321 err = __cpu_notify(CPU_DOWN_PREPARE | mod, hcpu, -1, &nr_calls);
324 __cpu_notify(CPU_DOWN_FAILED | mod, hcpu, nr_calls, NULL);
325 printk("%s: attempt to take down CPU %u failed\n",
329 smpboot_park_threads(cpu);
331 err = __stop_machine(take_cpu_down, &tcd_param, cpumask_of(cpu));
333 /* CPU didn't die: tell everyone. Can't complain. */
334 smpboot_unpark_threads(cpu);
335 cpu_notify_nofail(CPU_DOWN_FAILED | mod, hcpu);
338 BUG_ON(cpu_online(cpu));
341 * The migration_call() CPU_DYING callback will have removed all
342 * runnable tasks from the cpu, there's only the idle task left now
343 * that the migration thread is done doing the stop_machine thing.
345 * Wait for the stop thread to go away.
347 while (!idle_cpu(cpu))
350 /* This actually kills the CPU. */
353 /* CPU is completely dead: tell everyone. Too late to complain. */
354 cpu_notify_nofail(CPU_DEAD | mod, hcpu);
356 check_for_tasks(cpu);
361 cpu_notify_nofail(CPU_POST_DEAD | mod, hcpu);
365 int __ref cpu_down(unsigned int cpu)
369 cpu_maps_update_begin();
371 if (cpu_hotplug_disabled) {
376 err = _cpu_down(cpu, 0);
379 cpu_maps_update_done();
382 EXPORT_SYMBOL(cpu_down);
383 #endif /*CONFIG_HOTPLUG_CPU*/
385 /* Requires cpu_add_remove_lock to be held */
386 static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen)
388 int ret, nr_calls = 0;
389 void *hcpu = (void *)(long)cpu;
390 unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
391 struct task_struct *idle;
395 if (cpu_online(cpu) || !cpu_present(cpu)) {
400 idle = idle_thread_get(cpu);
406 ret = smpboot_create_threads(cpu);
410 ret = __cpu_notify(CPU_UP_PREPARE | mod, hcpu, -1, &nr_calls);
413 printk(KERN_WARNING "%s: attempt to bring up CPU %u failed\n",
418 /* Arch-specific enabling code. */
419 ret = __cpu_up(cpu, idle);
422 BUG_ON(!cpu_online(cpu));
424 /* Wake the per cpu threads */
425 smpboot_unpark_threads(cpu);
427 /* Now call notifier in preparation. */
428 cpu_notify(CPU_ONLINE | mod, hcpu);
432 __cpu_notify(CPU_UP_CANCELED | mod, hcpu, nr_calls, NULL);
439 int __cpuinit cpu_up(unsigned int cpu)
443 #ifdef CONFIG_MEMORY_HOTPLUG
448 if (!cpu_possible(cpu)) {
449 printk(KERN_ERR "can't online cpu %d because it is not "
450 "configured as may-hotadd at boot time\n", cpu);
451 #if defined(CONFIG_IA64)
452 printk(KERN_ERR "please check additional_cpus= boot "
458 #ifdef CONFIG_MEMORY_HOTPLUG
459 nid = cpu_to_node(cpu);
460 if (!node_online(nid)) {
461 err = mem_online_node(nid);
466 pgdat = NODE_DATA(nid);
469 "Can't online cpu %d due to NULL pgdat\n", cpu);
473 if (pgdat->node_zonelists->_zonerefs->zone == NULL) {
474 mutex_lock(&zonelists_mutex);
475 build_all_zonelists(NULL, NULL);
476 mutex_unlock(&zonelists_mutex);
480 cpu_maps_update_begin();
482 if (cpu_hotplug_disabled) {
487 err = _cpu_up(cpu, 0);
490 cpu_maps_update_done();
493 EXPORT_SYMBOL_GPL(cpu_up);
495 #ifdef CONFIG_PM_SLEEP_SMP
496 static cpumask_var_t frozen_cpus;
498 int disable_nonboot_cpus(void)
500 int cpu, first_cpu, error = 0;
502 cpu_maps_update_begin();
503 first_cpu = cpumask_first(cpu_online_mask);
505 * We take down all of the non-boot CPUs in one shot to avoid races
506 * with the userspace trying to use the CPU hotplug at the same time
508 cpumask_clear(frozen_cpus);
510 printk("Disabling non-boot CPUs ...\n");
511 for_each_online_cpu(cpu) {
512 if (cpu == first_cpu)
514 error = _cpu_down(cpu, 1);
516 cpumask_set_cpu(cpu, frozen_cpus);
518 printk(KERN_ERR "Error taking CPU%d down: %d\n",
525 BUG_ON(num_online_cpus() > 1);
526 /* Make sure the CPUs won't be enabled by someone else */
527 cpu_hotplug_disabled = 1;
529 printk(KERN_ERR "Non-boot CPUs are not disabled\n");
531 cpu_maps_update_done();
535 void __weak arch_enable_nonboot_cpus_begin(void)
539 void __weak arch_enable_nonboot_cpus_end(void)
543 void __ref enable_nonboot_cpus(void)
547 /* Allow everyone to use the CPU hotplug again */
548 cpu_maps_update_begin();
549 cpu_hotplug_disabled = 0;
550 if (cpumask_empty(frozen_cpus))
553 printk(KERN_INFO "Enabling non-boot CPUs ...\n");
555 arch_enable_nonboot_cpus_begin();
557 for_each_cpu(cpu, frozen_cpus) {
558 error = _cpu_up(cpu, 1);
560 printk(KERN_INFO "CPU%d is up\n", cpu);
563 printk(KERN_WARNING "Error taking CPU%d up: %d\n", cpu, error);
566 arch_enable_nonboot_cpus_end();
568 cpumask_clear(frozen_cpus);
570 cpu_maps_update_done();
573 static int __init alloc_frozen_cpus(void)
575 if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
579 core_initcall(alloc_frozen_cpus);
582 * When callbacks for CPU hotplug notifications are being executed, we must
583 * ensure that the state of the system with respect to the tasks being frozen
584 * or not, as reported by the notification, remains unchanged *throughout the
585 * duration* of the execution of the callbacks.
586 * Hence we need to prevent the freezer from racing with regular CPU hotplug.
588 * This synchronization is implemented by mutually excluding regular CPU
589 * hotplug and Suspend/Hibernate call paths by hooking onto the Suspend/
590 * Hibernate notifications.
593 cpu_hotplug_pm_callback(struct notifier_block *nb,
594 unsigned long action, void *ptr)
598 case PM_SUSPEND_PREPARE:
599 case PM_HIBERNATION_PREPARE:
600 cpu_hotplug_disable();
603 case PM_POST_SUSPEND:
604 case PM_POST_HIBERNATION:
605 cpu_hotplug_enable();
616 static int __init cpu_hotplug_pm_sync_init(void)
619 * cpu_hotplug_pm_callback has higher priority than x86
620 * bsp_pm_callback which depends on cpu_hotplug_pm_callback
621 * to disable cpu hotplug to avoid cpu hotplug race.
623 pm_notifier(cpu_hotplug_pm_callback, 0);
626 core_initcall(cpu_hotplug_pm_sync_init);
628 #endif /* CONFIG_PM_SLEEP_SMP */
631 * notify_cpu_starting(cpu) - call the CPU_STARTING notifiers
632 * @cpu: cpu that just started
634 * This function calls the cpu_chain notifiers with CPU_STARTING.
635 * It must be called by the arch code on the new cpu, before the new cpu
636 * enables interrupts and before the "boot" cpu returns from __cpu_up().
638 void __cpuinit notify_cpu_starting(unsigned int cpu)
640 unsigned long val = CPU_STARTING;
642 #ifdef CONFIG_PM_SLEEP_SMP
643 if (frozen_cpus != NULL && cpumask_test_cpu(cpu, frozen_cpus))
644 val = CPU_STARTING_FROZEN;
645 #endif /* CONFIG_PM_SLEEP_SMP */
646 cpu_notify(val, (void *)(long)cpu);
649 #endif /* CONFIG_SMP */
652 * cpu_bit_bitmap[] is a special, "compressed" data structure that
653 * represents all NR_CPUS bits binary values of 1<<nr.
655 * It is used by cpumask_of() to get a constant address to a CPU
656 * mask value that has a single bit set only.
659 /* cpu_bit_bitmap[0] is empty - so we can back into it */
660 #define MASK_DECLARE_1(x) [x+1][0] = (1UL << (x))
661 #define MASK_DECLARE_2(x) MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
662 #define MASK_DECLARE_4(x) MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
663 #define MASK_DECLARE_8(x) MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
665 const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
667 MASK_DECLARE_8(0), MASK_DECLARE_8(8),
668 MASK_DECLARE_8(16), MASK_DECLARE_8(24),
669 #if BITS_PER_LONG > 32
670 MASK_DECLARE_8(32), MASK_DECLARE_8(40),
671 MASK_DECLARE_8(48), MASK_DECLARE_8(56),
674 EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
676 const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
677 EXPORT_SYMBOL(cpu_all_bits);
679 #ifdef CONFIG_INIT_ALL_POSSIBLE
680 static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly
683 static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly;
685 const struct cpumask *const cpu_possible_mask = to_cpumask(cpu_possible_bits);
686 EXPORT_SYMBOL(cpu_possible_mask);
688 static DECLARE_BITMAP(cpu_online_bits, CONFIG_NR_CPUS) __read_mostly;
689 const struct cpumask *const cpu_online_mask = to_cpumask(cpu_online_bits);
690 EXPORT_SYMBOL(cpu_online_mask);
692 static DECLARE_BITMAP(cpu_present_bits, CONFIG_NR_CPUS) __read_mostly;
693 const struct cpumask *const cpu_present_mask = to_cpumask(cpu_present_bits);
694 EXPORT_SYMBOL(cpu_present_mask);
696 static DECLARE_BITMAP(cpu_active_bits, CONFIG_NR_CPUS) __read_mostly;
697 const struct cpumask *const cpu_active_mask = to_cpumask(cpu_active_bits);
698 EXPORT_SYMBOL(cpu_active_mask);
700 void set_cpu_possible(unsigned int cpu, bool possible)
703 cpumask_set_cpu(cpu, to_cpumask(cpu_possible_bits));
705 cpumask_clear_cpu(cpu, to_cpumask(cpu_possible_bits));
708 void set_cpu_present(unsigned int cpu, bool present)
711 cpumask_set_cpu(cpu, to_cpumask(cpu_present_bits));
713 cpumask_clear_cpu(cpu, to_cpumask(cpu_present_bits));
716 void set_cpu_online(unsigned int cpu, bool online)
719 cpumask_set_cpu(cpu, to_cpumask(cpu_online_bits));
720 cpumask_set_cpu(cpu, to_cpumask(cpu_active_bits));
722 cpumask_clear_cpu(cpu, to_cpumask(cpu_online_bits));
726 void set_cpu_active(unsigned int cpu, bool active)
729 cpumask_set_cpu(cpu, to_cpumask(cpu_active_bits));
731 cpumask_clear_cpu(cpu, to_cpumask(cpu_active_bits));
734 void init_cpu_present(const struct cpumask *src)
736 cpumask_copy(to_cpumask(cpu_present_bits), src);
739 void init_cpu_possible(const struct cpumask *src)
741 cpumask_copy(to_cpumask(cpu_possible_bits), src);
744 void init_cpu_online(const struct cpumask *src)
746 cpumask_copy(to_cpumask(cpu_online_bits), src);
749 static ATOMIC_NOTIFIER_HEAD(idle_notifier);
751 void idle_notifier_register(struct notifier_block *n)
753 atomic_notifier_chain_register(&idle_notifier, n);
755 EXPORT_SYMBOL_GPL(idle_notifier_register);
757 void idle_notifier_unregister(struct notifier_block *n)
759 atomic_notifier_chain_unregister(&idle_notifier, n);
761 EXPORT_SYMBOL_GPL(idle_notifier_unregister);
763 void idle_notifier_call_chain(unsigned long val)
765 atomic_notifier_call_chain(&idle_notifier, val, NULL);
767 EXPORT_SYMBOL_GPL(idle_notifier_call_chain);