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 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 void cpu_hotplug_done(void)
132 cpu_hotplug.active_writer = NULL;
133 mutex_unlock(&cpu_hotplug.lock);
137 * Wait for currently running CPU hotplug operations to complete (if any) and
138 * disable future CPU hotplug (from sysfs). The 'cpu_add_remove_lock' protects
139 * the 'cpu_hotplug_disabled' flag. The same lock is also acquired by the
140 * hotplug path before performing hotplug operations. So acquiring that lock
141 * guarantees mutual exclusion from any currently running hotplug operations.
143 void cpu_hotplug_disable(void)
145 cpu_maps_update_begin();
146 cpu_hotplug_disabled = 1;
147 cpu_maps_update_done();
150 void cpu_hotplug_enable(void)
152 cpu_maps_update_begin();
153 cpu_hotplug_disabled = 0;
154 cpu_maps_update_done();
157 #endif /* CONFIG_HOTPLUG_CPU */
159 /* Need to know about CPUs going up/down? */
160 int __ref register_cpu_notifier(struct notifier_block *nb)
163 cpu_maps_update_begin();
164 ret = raw_notifier_chain_register(&cpu_chain, nb);
165 cpu_maps_update_done();
169 static int __cpu_notify(unsigned long val, void *v, int nr_to_call,
174 ret = __raw_notifier_call_chain(&cpu_chain, val, v, nr_to_call,
177 return notifier_to_errno(ret);
180 static int cpu_notify(unsigned long val, void *v)
182 return __cpu_notify(val, v, -1, NULL);
185 #ifdef CONFIG_HOTPLUG_CPU
187 static void cpu_notify_nofail(unsigned long val, void *v)
189 BUG_ON(cpu_notify(val, v));
191 EXPORT_SYMBOL(register_cpu_notifier);
193 void __ref unregister_cpu_notifier(struct notifier_block *nb)
195 cpu_maps_update_begin();
196 raw_notifier_chain_unregister(&cpu_chain, nb);
197 cpu_maps_update_done();
199 EXPORT_SYMBOL(unregister_cpu_notifier);
202 * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
205 * This function walks all processes, finds a valid mm struct for each one and
206 * then clears a corresponding bit in mm's cpumask. While this all sounds
207 * trivial, there are various non-obvious corner cases, which this function
208 * tries to solve in a safe manner.
210 * Also note that the function uses a somewhat relaxed locking scheme, so it may
211 * be called only for an already offlined CPU.
213 void clear_tasks_mm_cpumask(int cpu)
215 struct task_struct *p;
218 * This function is called after the cpu is taken down and marked
219 * offline, so its not like new tasks will ever get this cpu set in
220 * their mm mask. -- Peter Zijlstra
221 * Thus, we may use rcu_read_lock() here, instead of grabbing
222 * full-fledged tasklist_lock.
224 WARN_ON(cpu_online(cpu));
226 for_each_process(p) {
227 struct task_struct *t;
230 * Main thread might exit, but other threads may still have
231 * a valid mm. Find one.
233 t = find_lock_task_mm(p);
236 cpumask_clear_cpu(cpu, mm_cpumask(t->mm));
242 static inline void check_for_tasks(int cpu)
244 struct task_struct *p;
245 cputime_t utime, stime;
247 write_lock_irq(&tasklist_lock);
248 for_each_process(p) {
249 task_cputime(p, &utime, &stime);
250 if (task_cpu(p) == cpu && p->state == TASK_RUNNING &&
252 printk(KERN_WARNING "Task %s (pid = %d) is on cpu %d "
253 "(state = %ld, flags = %x)\n",
254 p->comm, task_pid_nr(p), cpu,
257 write_unlock_irq(&tasklist_lock);
260 struct take_cpu_down_param {
265 /* Take this CPU down. */
266 static int __ref take_cpu_down(void *_param)
268 struct take_cpu_down_param *param = _param;
271 /* Ensure this CPU doesn't handle any more interrupts. */
272 err = __cpu_disable();
276 cpu_notify(CPU_DYING | param->mod, param->hcpu);
277 /* Park the stopper thread */
278 kthread_park(current);
282 /* Requires cpu_add_remove_lock to be held */
283 static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
285 int err, nr_calls = 0;
286 void *hcpu = (void *)(long)cpu;
287 unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
288 struct take_cpu_down_param tcd_param = {
293 if (num_online_cpus() == 1)
296 if (!cpu_online(cpu))
301 err = __cpu_notify(CPU_DOWN_PREPARE | mod, hcpu, -1, &nr_calls);
304 __cpu_notify(CPU_DOWN_FAILED | mod, hcpu, nr_calls, NULL);
305 printk("%s: attempt to take down CPU %u failed\n",
309 smpboot_park_threads(cpu);
312 * By now we've cleared cpu_active_mask, wait for all preempt-disabled
313 * and RCU users of this state to go away such that all new such users
316 * For CONFIG_PREEMPT we have preemptible RCU and its sync_rcu() might
317 * not imply sync_sched(), so explicitly call both.
319 #ifdef CONFIG_PREEMPT
325 * So now all preempt/rcu users must observe !cpu_active().
328 err = __stop_machine(take_cpu_down, &tcd_param, cpumask_of(cpu));
330 /* CPU didn't die: tell everyone. Can't complain. */
331 smpboot_unpark_threads(cpu);
332 cpu_notify_nofail(CPU_DOWN_FAILED | mod, hcpu);
335 BUG_ON(cpu_online(cpu));
338 * The migration_call() CPU_DYING callback will have removed all
339 * runnable tasks from the cpu, there's only the idle task left now
340 * that the migration thread is done doing the stop_machine thing.
342 * Wait for the stop thread to go away.
344 while (!idle_cpu(cpu))
347 /* This actually kills the CPU. */
350 /* CPU is completely dead: tell everyone. Too late to complain. */
351 cpu_notify_nofail(CPU_DEAD | mod, hcpu);
353 check_for_tasks(cpu);
358 cpu_notify_nofail(CPU_POST_DEAD | mod, hcpu);
362 int __ref cpu_down(unsigned int cpu)
366 cpu_maps_update_begin();
368 if (cpu_hotplug_disabled) {
373 err = _cpu_down(cpu, 0);
376 cpu_maps_update_done();
379 EXPORT_SYMBOL(cpu_down);
380 #endif /*CONFIG_HOTPLUG_CPU*/
382 /* Requires cpu_add_remove_lock to be held */
383 static int _cpu_up(unsigned int cpu, int tasks_frozen)
385 int ret, nr_calls = 0;
386 void *hcpu = (void *)(long)cpu;
387 unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
388 struct task_struct *idle;
392 if (cpu_online(cpu) || !cpu_present(cpu)) {
397 idle = idle_thread_get(cpu);
403 ret = smpboot_create_threads(cpu);
407 ret = __cpu_notify(CPU_UP_PREPARE | mod, hcpu, -1, &nr_calls);
410 printk(KERN_WARNING "%s: attempt to bring up CPU %u failed\n",
415 /* Arch-specific enabling code. */
416 ret = __cpu_up(cpu, idle);
419 BUG_ON(!cpu_online(cpu));
421 /* Wake the per cpu threads */
422 smpboot_unpark_threads(cpu);
424 /* Now call notifier in preparation. */
425 cpu_notify(CPU_ONLINE | mod, hcpu);
429 __cpu_notify(CPU_UP_CANCELED | mod, hcpu, nr_calls, NULL);
436 int cpu_up(unsigned int cpu)
440 #ifdef CONFIG_MEMORY_HOTPLUG
445 if (!cpu_possible(cpu)) {
446 printk(KERN_ERR "can't online cpu %d because it is not "
447 "configured as may-hotadd at boot time\n", cpu);
448 #if defined(CONFIG_IA64)
449 printk(KERN_ERR "please check additional_cpus= boot "
455 #ifdef CONFIG_MEMORY_HOTPLUG
456 nid = cpu_to_node(cpu);
457 if (!node_online(nid)) {
458 err = mem_online_node(nid);
463 pgdat = NODE_DATA(nid);
466 "Can't online cpu %d due to NULL pgdat\n", cpu);
470 if (pgdat->node_zonelists->_zonerefs->zone == NULL) {
471 mutex_lock(&zonelists_mutex);
472 build_all_zonelists(NULL, NULL);
473 mutex_unlock(&zonelists_mutex);
477 cpu_maps_update_begin();
479 if (cpu_hotplug_disabled) {
484 err = _cpu_up(cpu, 0);
487 cpu_maps_update_done();
490 EXPORT_SYMBOL_GPL(cpu_up);
492 #ifdef CONFIG_PM_SLEEP_SMP
493 static cpumask_var_t frozen_cpus;
495 int disable_nonboot_cpus(void)
497 int cpu, first_cpu, error = 0;
499 cpu_maps_update_begin();
500 first_cpu = cpumask_first(cpu_online_mask);
502 * We take down all of the non-boot CPUs in one shot to avoid races
503 * with the userspace trying to use the CPU hotplug at the same time
505 cpumask_clear(frozen_cpus);
507 printk("Disabling non-boot CPUs ...\n");
508 for_each_online_cpu(cpu) {
509 if (cpu == first_cpu)
511 error = _cpu_down(cpu, 1);
513 cpumask_set_cpu(cpu, frozen_cpus);
515 printk(KERN_ERR "Error taking CPU%d down: %d\n",
522 BUG_ON(num_online_cpus() > 1);
523 /* Make sure the CPUs won't be enabled by someone else */
524 cpu_hotplug_disabled = 1;
526 printk(KERN_ERR "Non-boot CPUs are not disabled\n");
528 cpu_maps_update_done();
532 void __weak arch_enable_nonboot_cpus_begin(void)
536 void __weak arch_enable_nonboot_cpus_end(void)
540 void __ref enable_nonboot_cpus(void)
544 /* Allow everyone to use the CPU hotplug again */
545 cpu_maps_update_begin();
546 cpu_hotplug_disabled = 0;
547 if (cpumask_empty(frozen_cpus))
550 printk(KERN_INFO "Enabling non-boot CPUs ...\n");
552 arch_enable_nonboot_cpus_begin();
554 for_each_cpu(cpu, frozen_cpus) {
555 error = _cpu_up(cpu, 1);
557 printk(KERN_INFO "CPU%d is up\n", cpu);
560 printk(KERN_WARNING "Error taking CPU%d up: %d\n", cpu, error);
563 arch_enable_nonboot_cpus_end();
565 cpumask_clear(frozen_cpus);
567 cpu_maps_update_done();
570 static int __init alloc_frozen_cpus(void)
572 if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
576 core_initcall(alloc_frozen_cpus);
579 * When callbacks for CPU hotplug notifications are being executed, we must
580 * ensure that the state of the system with respect to the tasks being frozen
581 * or not, as reported by the notification, remains unchanged *throughout the
582 * duration* of the execution of the callbacks.
583 * Hence we need to prevent the freezer from racing with regular CPU hotplug.
585 * This synchronization is implemented by mutually excluding regular CPU
586 * hotplug and Suspend/Hibernate call paths by hooking onto the Suspend/
587 * Hibernate notifications.
590 cpu_hotplug_pm_callback(struct notifier_block *nb,
591 unsigned long action, void *ptr)
595 case PM_SUSPEND_PREPARE:
596 case PM_HIBERNATION_PREPARE:
597 cpu_hotplug_disable();
600 case PM_POST_SUSPEND:
601 case PM_POST_HIBERNATION:
602 cpu_hotplug_enable();
613 static int __init cpu_hotplug_pm_sync_init(void)
616 * cpu_hotplug_pm_callback has higher priority than x86
617 * bsp_pm_callback which depends on cpu_hotplug_pm_callback
618 * to disable cpu hotplug to avoid cpu hotplug race.
620 pm_notifier(cpu_hotplug_pm_callback, 0);
623 core_initcall(cpu_hotplug_pm_sync_init);
625 #endif /* CONFIG_PM_SLEEP_SMP */
628 * notify_cpu_starting(cpu) - call the CPU_STARTING notifiers
629 * @cpu: cpu that just started
631 * This function calls the cpu_chain notifiers with CPU_STARTING.
632 * It must be called by the arch code on the new cpu, before the new cpu
633 * enables interrupts and before the "boot" cpu returns from __cpu_up().
635 void notify_cpu_starting(unsigned int cpu)
637 unsigned long val = CPU_STARTING;
639 #ifdef CONFIG_PM_SLEEP_SMP
640 if (frozen_cpus != NULL && cpumask_test_cpu(cpu, frozen_cpus))
641 val = CPU_STARTING_FROZEN;
642 #endif /* CONFIG_PM_SLEEP_SMP */
643 cpu_notify(val, (void *)(long)cpu);
646 #endif /* CONFIG_SMP */
649 * cpu_bit_bitmap[] is a special, "compressed" data structure that
650 * represents all NR_CPUS bits binary values of 1<<nr.
652 * It is used by cpumask_of() to get a constant address to a CPU
653 * mask value that has a single bit set only.
656 /* cpu_bit_bitmap[0] is empty - so we can back into it */
657 #define MASK_DECLARE_1(x) [x+1][0] = (1UL << (x))
658 #define MASK_DECLARE_2(x) MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
659 #define MASK_DECLARE_4(x) MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
660 #define MASK_DECLARE_8(x) MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
662 const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
664 MASK_DECLARE_8(0), MASK_DECLARE_8(8),
665 MASK_DECLARE_8(16), MASK_DECLARE_8(24),
666 #if BITS_PER_LONG > 32
667 MASK_DECLARE_8(32), MASK_DECLARE_8(40),
668 MASK_DECLARE_8(48), MASK_DECLARE_8(56),
671 EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
673 const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
674 EXPORT_SYMBOL(cpu_all_bits);
676 #ifdef CONFIG_INIT_ALL_POSSIBLE
677 static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly
680 static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly;
682 const struct cpumask *const cpu_possible_mask = to_cpumask(cpu_possible_bits);
683 EXPORT_SYMBOL(cpu_possible_mask);
685 static DECLARE_BITMAP(cpu_online_bits, CONFIG_NR_CPUS) __read_mostly;
686 const struct cpumask *const cpu_online_mask = to_cpumask(cpu_online_bits);
687 EXPORT_SYMBOL(cpu_online_mask);
689 static DECLARE_BITMAP(cpu_present_bits, CONFIG_NR_CPUS) __read_mostly;
690 const struct cpumask *const cpu_present_mask = to_cpumask(cpu_present_bits);
691 EXPORT_SYMBOL(cpu_present_mask);
693 static DECLARE_BITMAP(cpu_active_bits, CONFIG_NR_CPUS) __read_mostly;
694 const struct cpumask *const cpu_active_mask = to_cpumask(cpu_active_bits);
695 EXPORT_SYMBOL(cpu_active_mask);
697 void set_cpu_possible(unsigned int cpu, bool possible)
700 cpumask_set_cpu(cpu, to_cpumask(cpu_possible_bits));
702 cpumask_clear_cpu(cpu, to_cpumask(cpu_possible_bits));
705 void set_cpu_present(unsigned int cpu, bool present)
708 cpumask_set_cpu(cpu, to_cpumask(cpu_present_bits));
710 cpumask_clear_cpu(cpu, to_cpumask(cpu_present_bits));
713 void set_cpu_online(unsigned int cpu, bool online)
716 cpumask_set_cpu(cpu, to_cpumask(cpu_online_bits));
718 cpumask_clear_cpu(cpu, to_cpumask(cpu_online_bits));
721 void set_cpu_active(unsigned int cpu, bool active)
724 cpumask_set_cpu(cpu, to_cpumask(cpu_active_bits));
726 cpumask_clear_cpu(cpu, to_cpumask(cpu_active_bits));
729 void init_cpu_present(const struct cpumask *src)
731 cpumask_copy(to_cpumask(cpu_present_bits), src);
734 void init_cpu_possible(const struct cpumask *src)
736 cpumask_copy(to_cpumask(cpu_possible_bits), src);
739 void init_cpu_online(const struct cpumask *src)
741 cpumask_copy(to_cpumask(cpu_online_bits), src);