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/export.h>
14 #include <linux/kthread.h>
15 #include <linux/stop_machine.h>
16 #include <linux/mutex.h>
17 #include <linux/gfp.h>
18 #include <linux/suspend.h>
21 /* Serializes the updates to cpu_online_mask, cpu_present_mask */
22 static DEFINE_MUTEX(cpu_add_remove_lock);
25 * The following two API's must be used when attempting
26 * to serialize the updates to cpu_online_mask, cpu_present_mask.
28 void cpu_maps_update_begin(void)
30 mutex_lock(&cpu_add_remove_lock);
33 void cpu_maps_update_done(void)
35 mutex_unlock(&cpu_add_remove_lock);
38 static RAW_NOTIFIER_HEAD(cpu_chain);
40 /* If set, cpu_up and cpu_down will return -EBUSY and do nothing.
41 * Should always be manipulated under cpu_add_remove_lock
43 static int cpu_hotplug_disabled;
45 #ifdef CONFIG_HOTPLUG_CPU
48 struct task_struct *active_writer;
49 struct mutex lock; /* Synchronizes accesses to refcount, */
51 * Also blocks the new readers during
52 * an ongoing cpu hotplug operation.
56 .active_writer = NULL,
57 .lock = __MUTEX_INITIALIZER(cpu_hotplug.lock),
61 void get_online_cpus(void)
64 if (cpu_hotplug.active_writer == current)
66 mutex_lock(&cpu_hotplug.lock);
67 cpu_hotplug.refcount++;
68 mutex_unlock(&cpu_hotplug.lock);
71 EXPORT_SYMBOL_GPL(get_online_cpus);
73 void put_online_cpus(void)
75 if (cpu_hotplug.active_writer == current)
77 mutex_lock(&cpu_hotplug.lock);
78 if (!--cpu_hotplug.refcount && unlikely(cpu_hotplug.active_writer))
79 wake_up_process(cpu_hotplug.active_writer);
80 mutex_unlock(&cpu_hotplug.lock);
83 EXPORT_SYMBOL_GPL(put_online_cpus);
86 * This ensures that the hotplug operation can begin only when the
87 * refcount goes to zero.
89 * Note that during a cpu-hotplug operation, the new readers, if any,
90 * will be blocked by the cpu_hotplug.lock
92 * Since cpu_hotplug_begin() is always called after invoking
93 * cpu_maps_update_begin(), we can be sure that only one writer is active.
95 * Note that theoretically, there is a possibility of a livelock:
96 * - Refcount goes to zero, last reader wakes up the sleeping
98 * - Last reader unlocks the cpu_hotplug.lock.
99 * - A new reader arrives at this moment, bumps up the refcount.
100 * - The writer acquires the cpu_hotplug.lock finds the refcount
101 * non zero and goes to sleep again.
103 * However, this is very difficult to achieve in practice since
104 * get_online_cpus() not an api which is called all that often.
107 static void cpu_hotplug_begin(void)
109 cpu_hotplug.active_writer = current;
112 mutex_lock(&cpu_hotplug.lock);
113 if (likely(!cpu_hotplug.refcount))
115 __set_current_state(TASK_UNINTERRUPTIBLE);
116 mutex_unlock(&cpu_hotplug.lock);
121 static void cpu_hotplug_done(void)
123 cpu_hotplug.active_writer = NULL;
124 mutex_unlock(&cpu_hotplug.lock);
128 * Wait for currently running CPU hotplug operations to complete (if any) and
129 * disable future CPU hotplug (from sysfs). The 'cpu_add_remove_lock' protects
130 * the 'cpu_hotplug_disabled' flag. The same lock is also acquired by the
131 * hotplug path before performing hotplug operations. So acquiring that lock
132 * guarantees mutual exclusion from any currently running hotplug operations.
134 void cpu_hotplug_disable(void)
136 cpu_maps_update_begin();
137 cpu_hotplug_disabled = 1;
138 cpu_maps_update_done();
141 void cpu_hotplug_enable(void)
143 cpu_maps_update_begin();
144 cpu_hotplug_disabled = 0;
145 cpu_maps_update_done();
148 #else /* #if CONFIG_HOTPLUG_CPU */
149 static void cpu_hotplug_begin(void) {}
150 static void cpu_hotplug_done(void) {}
151 #endif /* #else #if CONFIG_HOTPLUG_CPU */
153 /* Need to know about CPUs going up/down? */
154 int __ref register_cpu_notifier(struct notifier_block *nb)
157 cpu_maps_update_begin();
158 ret = raw_notifier_chain_register(&cpu_chain, nb);
159 cpu_maps_update_done();
163 static int __cpu_notify(unsigned long val, void *v, int nr_to_call,
168 ret = __raw_notifier_call_chain(&cpu_chain, val, v, nr_to_call,
171 return notifier_to_errno(ret);
174 static int cpu_notify(unsigned long val, void *v)
176 return __cpu_notify(val, v, -1, NULL);
179 #ifdef CONFIG_HOTPLUG_CPU
181 static void cpu_notify_nofail(unsigned long val, void *v)
183 BUG_ON(cpu_notify(val, v));
185 EXPORT_SYMBOL(register_cpu_notifier);
187 void __ref unregister_cpu_notifier(struct notifier_block *nb)
189 cpu_maps_update_begin();
190 raw_notifier_chain_unregister(&cpu_chain, nb);
191 cpu_maps_update_done();
193 EXPORT_SYMBOL(unregister_cpu_notifier);
195 static inline void check_for_tasks(int cpu)
197 struct task_struct *p;
199 write_lock_irq(&tasklist_lock);
200 for_each_process(p) {
201 if (task_cpu(p) == cpu && p->state == TASK_RUNNING &&
202 (!cputime_eq(p->utime, cputime_zero) ||
203 !cputime_eq(p->stime, cputime_zero)))
204 printk(KERN_WARNING "Task %s (pid = %d) is on cpu %d "
205 "(state = %ld, flags = %x)\n",
206 p->comm, task_pid_nr(p), cpu,
209 write_unlock_irq(&tasklist_lock);
212 struct take_cpu_down_param {
217 /* Take this CPU down. */
218 static int __ref take_cpu_down(void *_param)
220 struct take_cpu_down_param *param = _param;
223 /* Ensure this CPU doesn't handle any more interrupts. */
224 err = __cpu_disable();
228 cpu_notify(CPU_DYING | param->mod, param->hcpu);
232 /* Requires cpu_add_remove_lock to be held */
233 static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
235 int err, nr_calls = 0;
236 void *hcpu = (void *)(long)cpu;
237 unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
238 struct take_cpu_down_param tcd_param = {
243 if (num_online_cpus() == 1)
246 if (!cpu_online(cpu))
251 err = __cpu_notify(CPU_DOWN_PREPARE | mod, hcpu, -1, &nr_calls);
254 __cpu_notify(CPU_DOWN_FAILED | mod, hcpu, nr_calls, NULL);
255 printk("%s: attempt to take down CPU %u failed\n",
260 err = __stop_machine(take_cpu_down, &tcd_param, cpumask_of(cpu));
262 /* CPU didn't die: tell everyone. Can't complain. */
263 cpu_notify_nofail(CPU_DOWN_FAILED | mod, hcpu);
267 BUG_ON(cpu_online(cpu));
270 * The migration_call() CPU_DYING callback will have removed all
271 * runnable tasks from the cpu, there's only the idle task left now
272 * that the migration thread is done doing the stop_machine thing.
274 * Wait for the stop thread to go away.
276 while (!idle_cpu(cpu))
279 /* This actually kills the CPU. */
282 /* CPU is completely dead: tell everyone. Too late to complain. */
283 cpu_notify_nofail(CPU_DEAD | mod, hcpu);
285 check_for_tasks(cpu);
290 cpu_notify_nofail(CPU_POST_DEAD | mod, hcpu);
294 int __ref cpu_down(unsigned int cpu)
298 cpu_maps_update_begin();
300 if (cpu_hotplug_disabled) {
305 err = _cpu_down(cpu, 0);
308 cpu_maps_update_done();
311 EXPORT_SYMBOL(cpu_down);
312 #endif /*CONFIG_HOTPLUG_CPU*/
314 /* Requires cpu_add_remove_lock to be held */
315 static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen)
317 int ret, nr_calls = 0;
318 void *hcpu = (void *)(long)cpu;
319 unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
321 if (cpu_online(cpu) || !cpu_present(cpu))
325 ret = __cpu_notify(CPU_UP_PREPARE | mod, hcpu, -1, &nr_calls);
328 printk(KERN_WARNING "%s: attempt to bring up CPU %u failed\n",
333 /* Arch-specific enabling code. */
337 BUG_ON(!cpu_online(cpu));
339 /* Now call notifier in preparation. */
340 cpu_notify(CPU_ONLINE | mod, hcpu);
344 __cpu_notify(CPU_UP_CANCELED | mod, hcpu, nr_calls, NULL);
350 int __cpuinit cpu_up(unsigned int cpu)
354 #ifdef CONFIG_MEMORY_HOTPLUG
359 if (!cpu_possible(cpu)) {
360 printk(KERN_ERR "can't online cpu %d because it is not "
361 "configured as may-hotadd at boot time\n", cpu);
362 #if defined(CONFIG_IA64)
363 printk(KERN_ERR "please check additional_cpus= boot "
369 #ifdef CONFIG_MEMORY_HOTPLUG
370 nid = cpu_to_node(cpu);
371 if (!node_online(nid)) {
372 err = mem_online_node(nid);
377 pgdat = NODE_DATA(nid);
380 "Can't online cpu %d due to NULL pgdat\n", cpu);
384 if (pgdat->node_zonelists->_zonerefs->zone == NULL) {
385 mutex_lock(&zonelists_mutex);
386 build_all_zonelists(NULL);
387 mutex_unlock(&zonelists_mutex);
391 cpu_maps_update_begin();
393 if (cpu_hotplug_disabled) {
398 err = _cpu_up(cpu, 0);
401 cpu_maps_update_done();
405 #ifdef CONFIG_PM_SLEEP_SMP
406 static cpumask_var_t frozen_cpus;
408 void __weak arch_disable_nonboot_cpus_begin(void)
412 void __weak arch_disable_nonboot_cpus_end(void)
416 int disable_nonboot_cpus(void)
418 int cpu, first_cpu, error = 0;
420 cpu_maps_update_begin();
421 first_cpu = cpumask_first(cpu_online_mask);
423 * We take down all of the non-boot CPUs in one shot to avoid races
424 * with the userspace trying to use the CPU hotplug at the same time
426 cpumask_clear(frozen_cpus);
427 arch_disable_nonboot_cpus_begin();
429 printk("Disabling non-boot CPUs ...\n");
430 for_each_online_cpu(cpu) {
431 if (cpu == first_cpu)
433 error = _cpu_down(cpu, 1);
435 cpumask_set_cpu(cpu, frozen_cpus);
437 printk(KERN_ERR "Error taking CPU%d down: %d\n",
443 arch_disable_nonboot_cpus_end();
446 BUG_ON(num_online_cpus() > 1);
447 /* Make sure the CPUs won't be enabled by someone else */
448 cpu_hotplug_disabled = 1;
450 printk(KERN_ERR "Non-boot CPUs are not disabled\n");
452 cpu_maps_update_done();
456 void __weak arch_enable_nonboot_cpus_begin(void)
460 void __weak arch_enable_nonboot_cpus_end(void)
464 void __ref enable_nonboot_cpus(void)
468 /* Allow everyone to use the CPU hotplug again */
469 cpu_maps_update_begin();
470 cpu_hotplug_disabled = 0;
471 if (cpumask_empty(frozen_cpus))
474 printk(KERN_INFO "Enabling non-boot CPUs ...\n");
476 arch_enable_nonboot_cpus_begin();
478 for_each_cpu(cpu, frozen_cpus) {
479 error = _cpu_up(cpu, 1);
481 printk(KERN_INFO "CPU%d is up\n", cpu);
484 printk(KERN_WARNING "Error taking CPU%d up: %d\n", cpu, error);
487 arch_enable_nonboot_cpus_end();
489 cpumask_clear(frozen_cpus);
491 cpu_maps_update_done();
494 static int alloc_frozen_cpus(void)
496 if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
500 core_initcall(alloc_frozen_cpus);
503 * When callbacks for CPU hotplug notifications are being executed, we must
504 * ensure that the state of the system with respect to the tasks being frozen
505 * or not, as reported by the notification, remains unchanged *throughout the
506 * duration* of the execution of the callbacks.
507 * Hence we need to prevent the freezer from racing with regular CPU hotplug.
509 * This synchronization is implemented by mutually excluding regular CPU
510 * hotplug and Suspend/Hibernate call paths by hooking onto the Suspend/
511 * Hibernate notifications.
514 cpu_hotplug_pm_callback(struct notifier_block *nb,
515 unsigned long action, void *ptr)
519 case PM_SUSPEND_PREPARE:
520 case PM_HIBERNATION_PREPARE:
521 cpu_hotplug_disable();
524 case PM_POST_SUSPEND:
525 case PM_POST_HIBERNATION:
526 cpu_hotplug_enable();
537 int cpu_hotplug_pm_sync_init(void)
539 pm_notifier(cpu_hotplug_pm_callback, 0);
542 core_initcall(cpu_hotplug_pm_sync_init);
544 #endif /* CONFIG_PM_SLEEP_SMP */
547 * notify_cpu_starting(cpu) - call the CPU_STARTING notifiers
548 * @cpu: cpu that just started
550 * This function calls the cpu_chain notifiers with CPU_STARTING.
551 * It must be called by the arch code on the new cpu, before the new cpu
552 * enables interrupts and before the "boot" cpu returns from __cpu_up().
554 void __cpuinit notify_cpu_starting(unsigned int cpu)
556 unsigned long val = CPU_STARTING;
558 #ifdef CONFIG_PM_SLEEP_SMP
559 if (frozen_cpus != NULL && cpumask_test_cpu(cpu, frozen_cpus))
560 val = CPU_STARTING_FROZEN;
561 #endif /* CONFIG_PM_SLEEP_SMP */
562 cpu_notify(val, (void *)(long)cpu);
565 #endif /* CONFIG_SMP */
568 * cpu_bit_bitmap[] is a special, "compressed" data structure that
569 * represents all NR_CPUS bits binary values of 1<<nr.
571 * It is used by cpumask_of() to get a constant address to a CPU
572 * mask value that has a single bit set only.
575 /* cpu_bit_bitmap[0] is empty - so we can back into it */
576 #define MASK_DECLARE_1(x) [x+1][0] = (1UL << (x))
577 #define MASK_DECLARE_2(x) MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
578 #define MASK_DECLARE_4(x) MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
579 #define MASK_DECLARE_8(x) MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
581 const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
583 MASK_DECLARE_8(0), MASK_DECLARE_8(8),
584 MASK_DECLARE_8(16), MASK_DECLARE_8(24),
585 #if BITS_PER_LONG > 32
586 MASK_DECLARE_8(32), MASK_DECLARE_8(40),
587 MASK_DECLARE_8(48), MASK_DECLARE_8(56),
590 EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
592 const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
593 EXPORT_SYMBOL(cpu_all_bits);
595 #ifdef CONFIG_INIT_ALL_POSSIBLE
596 static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly
599 static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly;
601 const struct cpumask *const cpu_possible_mask = to_cpumask(cpu_possible_bits);
602 EXPORT_SYMBOL(cpu_possible_mask);
604 static DECLARE_BITMAP(cpu_online_bits, CONFIG_NR_CPUS) __read_mostly;
605 const struct cpumask *const cpu_online_mask = to_cpumask(cpu_online_bits);
606 EXPORT_SYMBOL(cpu_online_mask);
608 static DECLARE_BITMAP(cpu_present_bits, CONFIG_NR_CPUS) __read_mostly;
609 const struct cpumask *const cpu_present_mask = to_cpumask(cpu_present_bits);
610 EXPORT_SYMBOL(cpu_present_mask);
612 static DECLARE_BITMAP(cpu_active_bits, CONFIG_NR_CPUS) __read_mostly;
613 const struct cpumask *const cpu_active_mask = to_cpumask(cpu_active_bits);
614 EXPORT_SYMBOL(cpu_active_mask);
616 void set_cpu_possible(unsigned int cpu, bool possible)
619 cpumask_set_cpu(cpu, to_cpumask(cpu_possible_bits));
621 cpumask_clear_cpu(cpu, to_cpumask(cpu_possible_bits));
624 void set_cpu_present(unsigned int cpu, bool present)
627 cpumask_set_cpu(cpu, to_cpumask(cpu_present_bits));
629 cpumask_clear_cpu(cpu, to_cpumask(cpu_present_bits));
632 void set_cpu_online(unsigned int cpu, bool online)
635 cpumask_set_cpu(cpu, to_cpumask(cpu_online_bits));
637 cpumask_clear_cpu(cpu, to_cpumask(cpu_online_bits));
640 void set_cpu_active(unsigned int cpu, bool active)
643 cpumask_set_cpu(cpu, to_cpumask(cpu_active_bits));
645 cpumask_clear_cpu(cpu, to_cpumask(cpu_active_bits));
648 void init_cpu_present(const struct cpumask *src)
650 cpumask_copy(to_cpumask(cpu_present_bits), src);
653 void init_cpu_possible(const struct cpumask *src)
655 cpumask_copy(to_cpumask(cpu_possible_bits), src);
658 void init_cpu_online(const struct cpumask *src)
660 cpumask_copy(to_cpumask(cpu_online_bits), src);