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/module.h>
14 #include <linux/kthread.h>
15 #include <linux/stop_machine.h>
16 #include <linux/mutex.h>
17 #include <linux/gfp.h>
20 /* Serializes the updates to cpu_online_mask, cpu_present_mask */
21 static DEFINE_MUTEX(cpu_add_remove_lock);
23 static __cpuinitdata RAW_NOTIFIER_HEAD(cpu_chain);
25 /* If set, cpu_up and cpu_down will return -EBUSY and do nothing.
26 * Should always be manipulated under cpu_add_remove_lock
28 static int cpu_hotplug_disabled;
31 struct task_struct *active_writer;
32 struct mutex lock; /* Synchronizes accesses to refcount, */
34 * Also blocks the new readers during
35 * an ongoing cpu hotplug operation.
39 .active_writer = NULL,
40 .lock = __MUTEX_INITIALIZER(cpu_hotplug.lock),
44 #ifdef CONFIG_HOTPLUG_CPU
46 void get_online_cpus(void)
49 if (cpu_hotplug.active_writer == current)
51 mutex_lock(&cpu_hotplug.lock);
52 cpu_hotplug.refcount++;
53 mutex_unlock(&cpu_hotplug.lock);
56 EXPORT_SYMBOL_GPL(get_online_cpus);
58 void put_online_cpus(void)
60 if (cpu_hotplug.active_writer == current)
62 mutex_lock(&cpu_hotplug.lock);
63 if (!--cpu_hotplug.refcount && unlikely(cpu_hotplug.active_writer))
64 wake_up_process(cpu_hotplug.active_writer);
65 mutex_unlock(&cpu_hotplug.lock);
68 EXPORT_SYMBOL_GPL(put_online_cpus);
70 #endif /* CONFIG_HOTPLUG_CPU */
73 * The following two API's must be used when attempting
74 * to serialize the updates to cpu_online_mask, cpu_present_mask.
76 void cpu_maps_update_begin(void)
78 mutex_lock(&cpu_add_remove_lock);
81 void cpu_maps_update_done(void)
83 mutex_unlock(&cpu_add_remove_lock);
87 * This ensures that the hotplug operation can begin only when the
88 * refcount goes to zero.
90 * Note that during a cpu-hotplug operation, the new readers, if any,
91 * will be blocked by the cpu_hotplug.lock
93 * Since cpu_hotplug_begin() is always called after invoking
94 * cpu_maps_update_begin(), we can be sure that only one writer is active.
96 * Note that theoretically, there is a possibility of a livelock:
97 * - Refcount goes to zero, last reader wakes up the sleeping
99 * - Last reader unlocks the cpu_hotplug.lock.
100 * - A new reader arrives at this moment, bumps up the refcount.
101 * - The writer acquires the cpu_hotplug.lock finds the refcount
102 * non zero and goes to sleep again.
104 * However, this is very difficult to achieve in practice since
105 * get_online_cpus() not an api which is called all that often.
108 static void cpu_hotplug_begin(void)
110 cpu_hotplug.active_writer = current;
113 mutex_lock(&cpu_hotplug.lock);
114 if (likely(!cpu_hotplug.refcount))
116 __set_current_state(TASK_UNINTERRUPTIBLE);
117 mutex_unlock(&cpu_hotplug.lock);
122 static void cpu_hotplug_done(void)
124 cpu_hotplug.active_writer = NULL;
125 mutex_unlock(&cpu_hotplug.lock);
127 /* Need to know about CPUs going up/down? */
128 int __ref register_cpu_notifier(struct notifier_block *nb)
131 cpu_maps_update_begin();
132 ret = raw_notifier_chain_register(&cpu_chain, nb);
133 cpu_maps_update_done();
137 static int __cpu_notify(unsigned long val, void *v, int nr_to_call,
140 return __raw_notifier_call_chain(&cpu_chain, val, v, nr_to_call,
144 static int cpu_notify(unsigned long val, void *v)
146 return __cpu_notify(val, v, -1, NULL);
149 static void cpu_notify_nofail(unsigned long val, void *v)
153 err = cpu_notify(val, v);
154 BUG_ON(err == NOTIFY_BAD);
157 #ifdef CONFIG_HOTPLUG_CPU
159 EXPORT_SYMBOL(register_cpu_notifier);
161 void __ref unregister_cpu_notifier(struct notifier_block *nb)
163 cpu_maps_update_begin();
164 raw_notifier_chain_unregister(&cpu_chain, nb);
165 cpu_maps_update_done();
167 EXPORT_SYMBOL(unregister_cpu_notifier);
169 static inline void check_for_tasks(int cpu)
171 struct task_struct *p;
173 write_lock_irq(&tasklist_lock);
174 for_each_process(p) {
175 if (task_cpu(p) == cpu && p->state == TASK_RUNNING &&
176 (!cputime_eq(p->utime, cputime_zero) ||
177 !cputime_eq(p->stime, cputime_zero)))
178 printk(KERN_WARNING "Task %s (pid = %d) is on cpu %d "
179 "(state = %ld, flags = %x)\n",
180 p->comm, task_pid_nr(p), cpu,
183 write_unlock_irq(&tasklist_lock);
186 struct take_cpu_down_param {
187 struct task_struct *caller;
192 /* Take this CPU down. */
193 static int __ref take_cpu_down(void *_param)
195 struct take_cpu_down_param *param = _param;
196 unsigned int cpu = (unsigned long)param->hcpu;
199 /* Ensure this CPU doesn't handle any more interrupts. */
200 err = __cpu_disable();
204 cpu_notify(CPU_DYING | param->mod, param->hcpu);
206 if (task_cpu(param->caller) == cpu)
207 move_task_off_dead_cpu(cpu, param->caller);
208 /* Force idle task to run as soon as we yield: it should
209 immediately notice cpu is offline and die quickly. */
214 /* Requires cpu_add_remove_lock to be held */
215 static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
217 int err, nr_calls = 0;
218 void *hcpu = (void *)(long)cpu;
219 unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
220 struct take_cpu_down_param tcd_param = {
226 if (num_online_cpus() == 1)
229 if (!cpu_online(cpu))
233 set_cpu_active(cpu, false);
234 err = __cpu_notify(CPU_DOWN_PREPARE | mod, hcpu, -1, &nr_calls);
235 if (err == NOTIFY_BAD) {
236 set_cpu_active(cpu, true);
239 __cpu_notify(CPU_DOWN_FAILED | mod, hcpu, nr_calls, NULL);
240 printk("%s: attempt to take down CPU %u failed\n",
246 err = __stop_machine(take_cpu_down, &tcd_param, cpumask_of(cpu));
248 set_cpu_active(cpu, true);
249 /* CPU didn't die: tell everyone. Can't complain. */
250 cpu_notify_nofail(CPU_DOWN_FAILED | mod, hcpu);
254 BUG_ON(cpu_online(cpu));
256 /* Wait for it to sleep (leaving idle task). */
257 while (!idle_cpu(cpu))
260 /* This actually kills the CPU. */
263 /* CPU is completely dead: tell everyone. Too late to complain. */
264 cpu_notify_nofail(CPU_DEAD | mod, hcpu);
266 check_for_tasks(cpu);
271 cpu_notify_nofail(CPU_POST_DEAD | mod, hcpu);
275 int __ref cpu_down(unsigned int cpu)
279 cpu_maps_update_begin();
281 if (cpu_hotplug_disabled) {
286 err = _cpu_down(cpu, 0);
289 cpu_maps_update_done();
292 EXPORT_SYMBOL(cpu_down);
293 #endif /*CONFIG_HOTPLUG_CPU*/
295 /* Requires cpu_add_remove_lock to be held */
296 static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen)
298 int ret, nr_calls = 0;
299 void *hcpu = (void *)(long)cpu;
300 unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
302 if (cpu_online(cpu) || !cpu_present(cpu))
306 ret = __cpu_notify(CPU_UP_PREPARE | mod, hcpu, -1, &nr_calls);
307 if (ret == NOTIFY_BAD) {
309 printk("%s: attempt to bring up CPU %u failed\n",
315 /* Arch-specific enabling code. */
319 BUG_ON(!cpu_online(cpu));
321 set_cpu_active(cpu, true);
323 /* Now call notifier in preparation. */
324 cpu_notify(CPU_ONLINE | mod, hcpu);
328 __cpu_notify(CPU_UP_CANCELED | mod, hcpu, nr_calls, NULL);
334 int __cpuinit cpu_up(unsigned int cpu)
338 #ifdef CONFIG_MEMORY_HOTPLUG
343 if (!cpu_possible(cpu)) {
344 printk(KERN_ERR "can't online cpu %d because it is not "
345 "configured as may-hotadd at boot time\n", cpu);
346 #if defined(CONFIG_IA64)
347 printk(KERN_ERR "please check additional_cpus= boot "
353 #ifdef CONFIG_MEMORY_HOTPLUG
354 nid = cpu_to_node(cpu);
355 if (!node_online(nid)) {
356 err = mem_online_node(nid);
361 pgdat = NODE_DATA(nid);
364 "Can't online cpu %d due to NULL pgdat\n", cpu);
368 if (pgdat->node_zonelists->_zonerefs->zone == NULL) {
369 mutex_lock(&zonelists_mutex);
370 build_all_zonelists(NULL);
371 mutex_unlock(&zonelists_mutex);
375 cpu_maps_update_begin();
377 if (cpu_hotplug_disabled) {
382 err = _cpu_up(cpu, 0);
385 cpu_maps_update_done();
389 #ifdef CONFIG_PM_SLEEP_SMP
390 static cpumask_var_t frozen_cpus;
392 int disable_nonboot_cpus(void)
394 int cpu, first_cpu, error;
396 cpu_maps_update_begin();
397 first_cpu = cpumask_first(cpu_online_mask);
399 * We take down all of the non-boot CPUs in one shot to avoid races
400 * with the userspace trying to use the CPU hotplug at the same time
402 cpumask_clear(frozen_cpus);
404 printk("Disabling non-boot CPUs ...\n");
405 for_each_online_cpu(cpu) {
406 if (cpu == first_cpu)
408 error = _cpu_down(cpu, 1);
410 cpumask_set_cpu(cpu, frozen_cpus);
412 printk(KERN_ERR "Error taking CPU%d down: %d\n",
419 BUG_ON(num_online_cpus() > 1);
420 /* Make sure the CPUs won't be enabled by someone else */
421 cpu_hotplug_disabled = 1;
423 printk(KERN_ERR "Non-boot CPUs are not disabled\n");
425 cpu_maps_update_done();
429 void __weak arch_enable_nonboot_cpus_begin(void)
433 void __weak arch_enable_nonboot_cpus_end(void)
437 void __ref enable_nonboot_cpus(void)
441 /* Allow everyone to use the CPU hotplug again */
442 cpu_maps_update_begin();
443 cpu_hotplug_disabled = 0;
444 if (cpumask_empty(frozen_cpus))
447 printk("Enabling non-boot CPUs ...\n");
449 arch_enable_nonboot_cpus_begin();
451 for_each_cpu(cpu, frozen_cpus) {
452 error = _cpu_up(cpu, 1);
454 printk("CPU%d is up\n", cpu);
457 printk(KERN_WARNING "Error taking CPU%d up: %d\n", cpu, error);
460 arch_enable_nonboot_cpus_end();
462 cpumask_clear(frozen_cpus);
464 cpu_maps_update_done();
467 static int alloc_frozen_cpus(void)
469 if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
473 core_initcall(alloc_frozen_cpus);
474 #endif /* CONFIG_PM_SLEEP_SMP */
477 * notify_cpu_starting(cpu) - call the CPU_STARTING notifiers
478 * @cpu: cpu that just started
480 * This function calls the cpu_chain notifiers with CPU_STARTING.
481 * It must be called by the arch code on the new cpu, before the new cpu
482 * enables interrupts and before the "boot" cpu returns from __cpu_up().
484 void __cpuinit notify_cpu_starting(unsigned int cpu)
486 unsigned long val = CPU_STARTING;
488 #ifdef CONFIG_PM_SLEEP_SMP
489 if (frozen_cpus != NULL && cpumask_test_cpu(cpu, frozen_cpus))
490 val = CPU_STARTING_FROZEN;
491 #endif /* CONFIG_PM_SLEEP_SMP */
492 cpu_notify(val, (void *)(long)cpu);
495 #endif /* CONFIG_SMP */
498 * cpu_bit_bitmap[] is a special, "compressed" data structure that
499 * represents all NR_CPUS bits binary values of 1<<nr.
501 * It is used by cpumask_of() to get a constant address to a CPU
502 * mask value that has a single bit set only.
505 /* cpu_bit_bitmap[0] is empty - so we can back into it */
506 #define MASK_DECLARE_1(x) [x+1][0] = 1UL << (x)
507 #define MASK_DECLARE_2(x) MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
508 #define MASK_DECLARE_4(x) MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
509 #define MASK_DECLARE_8(x) MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
511 const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
513 MASK_DECLARE_8(0), MASK_DECLARE_8(8),
514 MASK_DECLARE_8(16), MASK_DECLARE_8(24),
515 #if BITS_PER_LONG > 32
516 MASK_DECLARE_8(32), MASK_DECLARE_8(40),
517 MASK_DECLARE_8(48), MASK_DECLARE_8(56),
520 EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
522 const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
523 EXPORT_SYMBOL(cpu_all_bits);
525 #ifdef CONFIG_INIT_ALL_POSSIBLE
526 static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly
529 static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly;
531 const struct cpumask *const cpu_possible_mask = to_cpumask(cpu_possible_bits);
532 EXPORT_SYMBOL(cpu_possible_mask);
534 static DECLARE_BITMAP(cpu_online_bits, CONFIG_NR_CPUS) __read_mostly;
535 const struct cpumask *const cpu_online_mask = to_cpumask(cpu_online_bits);
536 EXPORT_SYMBOL(cpu_online_mask);
538 static DECLARE_BITMAP(cpu_present_bits, CONFIG_NR_CPUS) __read_mostly;
539 const struct cpumask *const cpu_present_mask = to_cpumask(cpu_present_bits);
540 EXPORT_SYMBOL(cpu_present_mask);
542 static DECLARE_BITMAP(cpu_active_bits, CONFIG_NR_CPUS) __read_mostly;
543 const struct cpumask *const cpu_active_mask = to_cpumask(cpu_active_bits);
544 EXPORT_SYMBOL(cpu_active_mask);
546 void set_cpu_possible(unsigned int cpu, bool possible)
549 cpumask_set_cpu(cpu, to_cpumask(cpu_possible_bits));
551 cpumask_clear_cpu(cpu, to_cpumask(cpu_possible_bits));
554 void set_cpu_present(unsigned int cpu, bool present)
557 cpumask_set_cpu(cpu, to_cpumask(cpu_present_bits));
559 cpumask_clear_cpu(cpu, to_cpumask(cpu_present_bits));
562 void set_cpu_online(unsigned int cpu, bool online)
565 cpumask_set_cpu(cpu, to_cpumask(cpu_online_bits));
567 cpumask_clear_cpu(cpu, to_cpumask(cpu_online_bits));
570 void set_cpu_active(unsigned int cpu, bool active)
573 cpumask_set_cpu(cpu, to_cpumask(cpu_active_bits));
575 cpumask_clear_cpu(cpu, to_cpumask(cpu_active_bits));
578 void init_cpu_present(const struct cpumask *src)
580 cpumask_copy(to_cpumask(cpu_present_bits), src);
583 void init_cpu_possible(const struct cpumask *src)
585 cpumask_copy(to_cpumask(cpu_possible_bits), src);
588 void init_cpu_online(const struct cpumask *src)
590 cpumask_copy(to_cpumask(cpu_online_bits), src);