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1/* CPU control.
2 * (C) 2001, 2002, 2003, 2004 Rusty Russell
3 *
4 * This code is licenced under the GPL.
5 */
6#include <linux/proc_fs.h>
7#include <linux/smp.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>
22
23#include "smpboot.h"
24
25#ifdef CONFIG_SMP
26/* Serializes the updates to cpu_online_mask, cpu_present_mask */
27static DEFINE_MUTEX(cpu_add_remove_lock);
28
29/*
30 * The following two API's must be used when attempting
31 * to serialize the updates to cpu_online_mask, cpu_present_mask.
32 */
33void cpu_maps_update_begin(void)
34{
35 mutex_lock(&cpu_add_remove_lock);
36}
37
38void cpu_maps_update_done(void)
39{
40 mutex_unlock(&cpu_add_remove_lock);
41}
42
43static RAW_NOTIFIER_HEAD(cpu_chain);
44
45/* If set, cpu_up and cpu_down will return -EBUSY and do nothing.
46 * Should always be manipulated under cpu_add_remove_lock
47 */
48static int cpu_hotplug_disabled;
49
50#ifdef CONFIG_HOTPLUG_CPU
51
52static struct {
53 struct task_struct *active_writer;
54 struct mutex lock; /* Synchronizes accesses to refcount, */
55 /*
56 * Also blocks the new readers during
57 * an ongoing cpu hotplug operation.
58 */
59 int refcount;
60} cpu_hotplug = {
61 .active_writer = NULL,
62 .lock = __MUTEX_INITIALIZER(cpu_hotplug.lock),
63 .refcount = 0,
64};
65
66void get_online_cpus(void)
67{
68 might_sleep();
69 if (cpu_hotplug.active_writer == current)
70 return;
71 mutex_lock(&cpu_hotplug.lock);
72 cpu_hotplug.refcount++;
73 mutex_unlock(&cpu_hotplug.lock);
74
75}
76EXPORT_SYMBOL_GPL(get_online_cpus);
77
78void put_online_cpus(void)
79{
80 if (cpu_hotplug.active_writer == current)
81 return;
82 mutex_lock(&cpu_hotplug.lock);
83 if (!--cpu_hotplug.refcount && unlikely(cpu_hotplug.active_writer))
84 wake_up_process(cpu_hotplug.active_writer);
85 mutex_unlock(&cpu_hotplug.lock);
86
87}
88EXPORT_SYMBOL_GPL(put_online_cpus);
89
90/*
91 * This ensures that the hotplug operation can begin only when the
92 * refcount goes to zero.
93 *
94 * Note that during a cpu-hotplug operation, the new readers, if any,
95 * will be blocked by the cpu_hotplug.lock
96 *
97 * Since cpu_hotplug_begin() is always called after invoking
98 * cpu_maps_update_begin(), we can be sure that only one writer is active.
99 *
100 * Note that theoretically, there is a possibility of a livelock:
101 * - Refcount goes to zero, last reader wakes up the sleeping
102 * writer.
103 * - Last reader unlocks the cpu_hotplug.lock.
104 * - A new reader arrives at this moment, bumps up the refcount.
105 * - The writer acquires the cpu_hotplug.lock finds the refcount
106 * non zero and goes to sleep again.
107 *
108 * However, this is very difficult to achieve in practice since
109 * get_online_cpus() not an api which is called all that often.
110 *
111 */
112static void cpu_hotplug_begin(void)
113{
114 cpu_hotplug.active_writer = current;
115
116 for (;;) {
117 mutex_lock(&cpu_hotplug.lock);
118 if (likely(!cpu_hotplug.refcount))
119 break;
120 __set_current_state(TASK_UNINTERRUPTIBLE);
121 mutex_unlock(&cpu_hotplug.lock);
122 schedule();
123 }
124}
125
126static void cpu_hotplug_done(void)
127{
128 cpu_hotplug.active_writer = NULL;
129 mutex_unlock(&cpu_hotplug.lock);
130}
131
132#else /* #if CONFIG_HOTPLUG_CPU */
133static void cpu_hotplug_begin(void) {}
134static void cpu_hotplug_done(void) {}
135#endif /* #else #if CONFIG_HOTPLUG_CPU */
136
137/* Need to know about CPUs going up/down? */
138int __ref register_cpu_notifier(struct notifier_block *nb)
139{
140 int ret;
141 cpu_maps_update_begin();
142 ret = raw_notifier_chain_register(&cpu_chain, nb);
143 cpu_maps_update_done();
144 return ret;
145}
146
147static int __cpu_notify(unsigned long val, void *v, int nr_to_call,
148 int *nr_calls)
149{
150 int ret;
151
152 ret = __raw_notifier_call_chain(&cpu_chain, val, v, nr_to_call,
153 nr_calls);
154
155 return notifier_to_errno(ret);
156}
157
158static int cpu_notify(unsigned long val, void *v)
159{
160 return __cpu_notify(val, v, -1, NULL);
161}
162
163#ifdef CONFIG_HOTPLUG_CPU
164
165static void cpu_notify_nofail(unsigned long val, void *v)
166{
167 BUG_ON(cpu_notify(val, v));
168}
169EXPORT_SYMBOL(register_cpu_notifier);
170
171void __ref unregister_cpu_notifier(struct notifier_block *nb)
172{
173 cpu_maps_update_begin();
174 raw_notifier_chain_unregister(&cpu_chain, nb);
175 cpu_maps_update_done();
176}
177EXPORT_SYMBOL(unregister_cpu_notifier);
178
179/**
180 * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
181 * @cpu: a CPU id
182 *
183 * This function walks all processes, finds a valid mm struct for each one and
184 * then clears a corresponding bit in mm's cpumask. While this all sounds
185 * trivial, there are various non-obvious corner cases, which this function
186 * tries to solve in a safe manner.
187 *
188 * Also note that the function uses a somewhat relaxed locking scheme, so it may
189 * be called only for an already offlined CPU.
190 */
191void clear_tasks_mm_cpumask(int cpu)
192{
193 struct task_struct *p;
194
195 /*
196 * This function is called after the cpu is taken down and marked
197 * offline, so its not like new tasks will ever get this cpu set in
198 * their mm mask. -- Peter Zijlstra
199 * Thus, we may use rcu_read_lock() here, instead of grabbing
200 * full-fledged tasklist_lock.
201 */
202 WARN_ON(cpu_online(cpu));
203 rcu_read_lock();
204 for_each_process(p) {
205 struct task_struct *t;
206
207 /*
208 * Main thread might exit, but other threads may still have
209 * a valid mm. Find one.
210 */
211 t = find_lock_task_mm(p);
212 if (!t)
213 continue;
214 cpumask_clear_cpu(cpu, mm_cpumask(t->mm));
215 task_unlock(t);
216 }
217 rcu_read_unlock();
218}
219
220static inline void check_for_tasks(int cpu)
221{
222 struct task_struct *p;
223
224 write_lock_irq(&tasklist_lock);
225 for_each_process(p) {
226 if (task_cpu(p) == cpu && p->state == TASK_RUNNING &&
227 (p->utime || p->stime))
228 printk(KERN_WARNING "Task %s (pid = %d) is on cpu %d "
229 "(state = %ld, flags = %x)\n",
230 p->comm, task_pid_nr(p), cpu,
231 p->state, p->flags);
232 }
233 write_unlock_irq(&tasklist_lock);
234}
235
236struct take_cpu_down_param {
237 unsigned long mod;
238 void *hcpu;
239};
240
241/* Take this CPU down. */
242static int __ref take_cpu_down(void *_param)
243{
244 struct take_cpu_down_param *param = _param;
245 int err;
246
247 /* Ensure this CPU doesn't handle any more interrupts. */
248 err = __cpu_disable();
249 if (err < 0)
250 return err;
251
252 cpu_notify(CPU_DYING | param->mod, param->hcpu);
253 return 0;
254}
255
256/* Requires cpu_add_remove_lock to be held */
257static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
258{
259 int err, nr_calls = 0;
260 void *hcpu = (void *)(long)cpu;
261 unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
262 struct take_cpu_down_param tcd_param = {
263 .mod = mod,
264 .hcpu = hcpu,
265 };
266
267 if (num_online_cpus() == 1)
268 return -EBUSY;
269
270 if (!cpu_online(cpu))
271 return -EINVAL;
272
273 cpu_hotplug_begin();
274
275 err = __cpu_notify(CPU_DOWN_PREPARE | mod, hcpu, -1, &nr_calls);
276 if (err) {
277 nr_calls--;
278 __cpu_notify(CPU_DOWN_FAILED | mod, hcpu, nr_calls, NULL);
279 printk("%s: attempt to take down CPU %u failed\n",
280 __func__, cpu);
281 goto out_release;
282 }
283
284 err = __stop_machine(take_cpu_down, &tcd_param, cpumask_of(cpu));
285 if (err) {
286 /* CPU didn't die: tell everyone. Can't complain. */
287 cpu_notify_nofail(CPU_DOWN_FAILED | mod, hcpu);
288
289 goto out_release;
290 }
291 BUG_ON(cpu_online(cpu));
292
293 /*
294 * The migration_call() CPU_DYING callback will have removed all
295 * runnable tasks from the cpu, there's only the idle task left now
296 * that the migration thread is done doing the stop_machine thing.
297 *
298 * Wait for the stop thread to go away.
299 */
300 while (!idle_cpu(cpu))
301 cpu_relax();
302
303 /* This actually kills the CPU. */
304 __cpu_die(cpu);
305
306 /* CPU is completely dead: tell everyone. Too late to complain. */
307 cpu_notify_nofail(CPU_DEAD | mod, hcpu);
308
309 check_for_tasks(cpu);
310
311out_release:
312 cpu_hotplug_done();
313 if (!err)
314 cpu_notify_nofail(CPU_POST_DEAD | mod, hcpu);
315 return err;
316}
317
318int __ref cpu_down(unsigned int cpu)
319{
320 int err;
321
322 cpu_maps_update_begin();
323
324 if (cpu_hotplug_disabled) {
325 err = -EBUSY;
326 goto out;
327 }
328
329 err = _cpu_down(cpu, 0);
330
331out:
332 cpu_maps_update_done();
333 return err;
334}
335EXPORT_SYMBOL(cpu_down);
336#endif /*CONFIG_HOTPLUG_CPU*/
337
338/* Requires cpu_add_remove_lock to be held */
339static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen)
340{
341 int ret, nr_calls = 0;
342 void *hcpu = (void *)(long)cpu;
343 unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
344 struct task_struct *idle;
345
346 if (cpu_online(cpu) || !cpu_present(cpu))
347 return -EINVAL;
348
349 cpu_hotplug_begin();
350
351 idle = idle_thread_get(cpu);
352 if (IS_ERR(idle)) {
353 ret = PTR_ERR(idle);
354 goto out;
355 }
356
357 ret = __cpu_notify(CPU_UP_PREPARE | mod, hcpu, -1, &nr_calls);
358 if (ret) {
359 nr_calls--;
360 printk(KERN_WARNING "%s: attempt to bring up CPU %u failed\n",
361 __func__, cpu);
362 goto out_notify;
363 }
364
365 /* Arch-specific enabling code. */
366 ret = __cpu_up(cpu, idle);
367 if (ret != 0)
368 goto out_notify;
369 BUG_ON(!cpu_online(cpu));
370
371 /* Now call notifier in preparation. */
372 cpu_notify(CPU_ONLINE | mod, hcpu);
373
374out_notify:
375 if (ret != 0)
376 __cpu_notify(CPU_UP_CANCELED | mod, hcpu, nr_calls, NULL);
377out:
378 cpu_hotplug_done();
379
380 return ret;
381}
382
383int __cpuinit cpu_up(unsigned int cpu)
384{
385 int err = 0;
386
387#ifdef CONFIG_MEMORY_HOTPLUG
388 int nid;
389 pg_data_t *pgdat;
390#endif
391
392 if (!cpu_possible(cpu)) {
393 printk(KERN_ERR "can't online cpu %d because it is not "
394 "configured as may-hotadd at boot time\n", cpu);
395#if defined(CONFIG_IA64)
396 printk(KERN_ERR "please check additional_cpus= boot "
397 "parameter\n");
398#endif
399 return -EINVAL;
400 }
401
402#ifdef CONFIG_MEMORY_HOTPLUG
403 nid = cpu_to_node(cpu);
404 if (!node_online(nid)) {
405 err = mem_online_node(nid);
406 if (err)
407 return err;
408 }
409
410 pgdat = NODE_DATA(nid);
411 if (!pgdat) {
412 printk(KERN_ERR
413 "Can't online cpu %d due to NULL pgdat\n", cpu);
414 return -ENOMEM;
415 }
416
417 if (pgdat->node_zonelists->_zonerefs->zone == NULL) {
418 mutex_lock(&zonelists_mutex);
419 build_all_zonelists(NULL);
420 mutex_unlock(&zonelists_mutex);
421 }
422#endif
423
424 cpu_maps_update_begin();
425
426 if (cpu_hotplug_disabled) {
427 err = -EBUSY;
428 goto out;
429 }
430
431 err = _cpu_up(cpu, 0);
432
433out:
434 cpu_maps_update_done();
435 return err;
436}
437EXPORT_SYMBOL_GPL(cpu_up);
438
439#ifdef CONFIG_PM_SLEEP_SMP
440static cpumask_var_t frozen_cpus;
441
442void __weak arch_disable_nonboot_cpus_begin(void)
443{
444}
445
446void __weak arch_disable_nonboot_cpus_end(void)
447{
448}
449
450int disable_nonboot_cpus(void)
451{
452 int cpu, first_cpu, error = 0;
453
454 cpu_maps_update_begin();
455 first_cpu = cpumask_first(cpu_online_mask);
456 /*
457 * We take down all of the non-boot CPUs in one shot to avoid races
458 * with the userspace trying to use the CPU hotplug at the same time
459 */
460 cpumask_clear(frozen_cpus);
461 arch_disable_nonboot_cpus_begin();
462
463 printk("Disabling non-boot CPUs ...\n");
464 for_each_online_cpu(cpu) {
465 if (cpu == first_cpu)
466 continue;
467 error = _cpu_down(cpu, 1);
468 if (!error)
469 cpumask_set_cpu(cpu, frozen_cpus);
470 else {
471 printk(KERN_ERR "Error taking CPU%d down: %d\n",
472 cpu, error);
473 break;
474 }
475 }
476
477 arch_disable_nonboot_cpus_end();
478
479 if (!error) {
480 BUG_ON(num_online_cpus() > 1);
481 /* Make sure the CPUs won't be enabled by someone else */
482 cpu_hotplug_disabled = 1;
483 } else {
484 printk(KERN_ERR "Non-boot CPUs are not disabled\n");
485 }
486 cpu_maps_update_done();
487 return error;
488}
489
490void __weak arch_enable_nonboot_cpus_begin(void)
491{
492}
493
494void __weak arch_enable_nonboot_cpus_end(void)
495{
496}
497
498void __ref enable_nonboot_cpus(void)
499{
500 int cpu, error;
501
502 /* Allow everyone to use the CPU hotplug again */
503 cpu_maps_update_begin();
504 cpu_hotplug_disabled = 0;
505 if (cpumask_empty(frozen_cpus))
506 goto out;
507
508 printk(KERN_INFO "Enabling non-boot CPUs ...\n");
509
510 arch_enable_nonboot_cpus_begin();
511
512 for_each_cpu(cpu, frozen_cpus) {
513 error = _cpu_up(cpu, 1);
514 if (!error) {
515 printk(KERN_INFO "CPU%d is up\n", cpu);
516 continue;
517 }
518 printk(KERN_WARNING "Error taking CPU%d up: %d\n", cpu, error);
519 }
520
521 arch_enable_nonboot_cpus_end();
522
523 cpumask_clear(frozen_cpus);
524out:
525 cpu_maps_update_done();
526}
527
528static int __init alloc_frozen_cpus(void)
529{
530 if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
531 return -ENOMEM;
532 return 0;
533}
534core_initcall(alloc_frozen_cpus);
535
536/*
537 * Prevent regular CPU hotplug from racing with the freezer, by disabling CPU
538 * hotplug when tasks are about to be frozen. Also, don't allow the freezer
539 * to continue until any currently running CPU hotplug operation gets
540 * completed.
541 * To modify the 'cpu_hotplug_disabled' flag, we need to acquire the
542 * 'cpu_add_remove_lock'. And this same lock is also taken by the regular
543 * CPU hotplug path and released only after it is complete. Thus, we
544 * (and hence the freezer) will block here until any currently running CPU
545 * hotplug operation gets completed.
546 */
547void cpu_hotplug_disable_before_freeze(void)
548{
549 cpu_maps_update_begin();
550 cpu_hotplug_disabled = 1;
551 cpu_maps_update_done();
552}
553
554
555/*
556 * When tasks have been thawed, re-enable regular CPU hotplug (which had been
557 * disabled while beginning to freeze tasks).
558 */
559void cpu_hotplug_enable_after_thaw(void)
560{
561 cpu_maps_update_begin();
562 cpu_hotplug_disabled = 0;
563 cpu_maps_update_done();
564}
565
566/*
567 * When callbacks for CPU hotplug notifications are being executed, we must
568 * ensure that the state of the system with respect to the tasks being frozen
569 * or not, as reported by the notification, remains unchanged *throughout the
570 * duration* of the execution of the callbacks.
571 * Hence we need to prevent the freezer from racing with regular CPU hotplug.
572 *
573 * This synchronization is implemented by mutually excluding regular CPU
574 * hotplug and Suspend/Hibernate call paths by hooking onto the Suspend/
575 * Hibernate notifications.
576 */
577static int
578cpu_hotplug_pm_callback(struct notifier_block *nb,
579 unsigned long action, void *ptr)
580{
581 switch (action) {
582
583 case PM_SUSPEND_PREPARE:
584 case PM_HIBERNATION_PREPARE:
585 cpu_hotplug_disable_before_freeze();
586 break;
587
588 case PM_POST_SUSPEND:
589 case PM_POST_HIBERNATION:
590 cpu_hotplug_enable_after_thaw();
591 break;
592
593 default:
594 return NOTIFY_DONE;
595 }
596
597 return NOTIFY_OK;
598}
599
600
601static int __init cpu_hotplug_pm_sync_init(void)
602{
603 pm_notifier(cpu_hotplug_pm_callback, 0);
604 return 0;
605}
606core_initcall(cpu_hotplug_pm_sync_init);
607
608#endif /* CONFIG_PM_SLEEP_SMP */
609
610/**
611 * notify_cpu_starting(cpu) - call the CPU_STARTING notifiers
612 * @cpu: cpu that just started
613 *
614 * This function calls the cpu_chain notifiers with CPU_STARTING.
615 * It must be called by the arch code on the new cpu, before the new cpu
616 * enables interrupts and before the "boot" cpu returns from __cpu_up().
617 */
618void __cpuinit notify_cpu_starting(unsigned int cpu)
619{
620 unsigned long val = CPU_STARTING;
621
622#ifdef CONFIG_PM_SLEEP_SMP
623 if (frozen_cpus != NULL && cpumask_test_cpu(cpu, frozen_cpus))
624 val = CPU_STARTING_FROZEN;
625#endif /* CONFIG_PM_SLEEP_SMP */
626 cpu_notify(val, (void *)(long)cpu);
627}
628
629#endif /* CONFIG_SMP */
630
631/*
632 * cpu_bit_bitmap[] is a special, "compressed" data structure that
633 * represents all NR_CPUS bits binary values of 1<<nr.
634 *
635 * It is used by cpumask_of() to get a constant address to a CPU
636 * mask value that has a single bit set only.
637 */
638
639/* cpu_bit_bitmap[0] is empty - so we can back into it */
640#define MASK_DECLARE_1(x) [x+1][0] = (1UL << (x))
641#define MASK_DECLARE_2(x) MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
642#define MASK_DECLARE_4(x) MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
643#define MASK_DECLARE_8(x) MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
644
645const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
646
647 MASK_DECLARE_8(0), MASK_DECLARE_8(8),
648 MASK_DECLARE_8(16), MASK_DECLARE_8(24),
649#if BITS_PER_LONG > 32
650 MASK_DECLARE_8(32), MASK_DECLARE_8(40),
651 MASK_DECLARE_8(48), MASK_DECLARE_8(56),
652#endif
653};
654EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
655
656const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
657EXPORT_SYMBOL(cpu_all_bits);
658
659#ifdef CONFIG_INIT_ALL_POSSIBLE
660static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly
661 = CPU_BITS_ALL;
662#else
663static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly;
664#endif
665const struct cpumask *const cpu_possible_mask = to_cpumask(cpu_possible_bits);
666EXPORT_SYMBOL(cpu_possible_mask);
667
668static DECLARE_BITMAP(cpu_online_bits, CONFIG_NR_CPUS) __read_mostly;
669const struct cpumask *const cpu_online_mask = to_cpumask(cpu_online_bits);
670EXPORT_SYMBOL(cpu_online_mask);
671
672static DECLARE_BITMAP(cpu_present_bits, CONFIG_NR_CPUS) __read_mostly;
673const struct cpumask *const cpu_present_mask = to_cpumask(cpu_present_bits);
674EXPORT_SYMBOL(cpu_present_mask);
675
676static DECLARE_BITMAP(cpu_active_bits, CONFIG_NR_CPUS) __read_mostly;
677const struct cpumask *const cpu_active_mask = to_cpumask(cpu_active_bits);
678EXPORT_SYMBOL(cpu_active_mask);
679
680void set_cpu_possible(unsigned int cpu, bool possible)
681{
682 if (possible)
683 cpumask_set_cpu(cpu, to_cpumask(cpu_possible_bits));
684 else
685 cpumask_clear_cpu(cpu, to_cpumask(cpu_possible_bits));
686}
687
688void set_cpu_present(unsigned int cpu, bool present)
689{
690 if (present)
691 cpumask_set_cpu(cpu, to_cpumask(cpu_present_bits));
692 else
693 cpumask_clear_cpu(cpu, to_cpumask(cpu_present_bits));
694}
695
696void set_cpu_online(unsigned int cpu, bool online)
697{
698 if (online)
699 cpumask_set_cpu(cpu, to_cpumask(cpu_online_bits));
700 else
701 cpumask_clear_cpu(cpu, to_cpumask(cpu_online_bits));
702}
703
704void set_cpu_active(unsigned int cpu, bool active)
705{
706 if (active)
707 cpumask_set_cpu(cpu, to_cpumask(cpu_active_bits));
708 else
709 cpumask_clear_cpu(cpu, to_cpumask(cpu_active_bits));
710}
711
712void init_cpu_present(const struct cpumask *src)
713{
714 cpumask_copy(to_cpumask(cpu_present_bits), src);
715}
716
717void init_cpu_possible(const struct cpumask *src)
718{
719 cpumask_copy(to_cpumask(cpu_possible_bits), src);
720}
721
722void init_cpu_online(const struct cpumask *src)
723{
724 cpumask_copy(to_cpumask(cpu_online_bits), src);
725}
1/* CPU control.
2 * (C) 2001, 2002, 2003, 2004 Rusty Russell
3 *
4 * This code is licenced under the GPL.
5 */
6#include <linux/proc_fs.h>
7#include <linux/smp.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>
18
19#ifdef CONFIG_SMP
20/* Serializes the updates to cpu_online_mask, cpu_present_mask */
21static DEFINE_MUTEX(cpu_add_remove_lock);
22
23/*
24 * The following two API's must be used when attempting
25 * to serialize the updates to cpu_online_mask, cpu_present_mask.
26 */
27void cpu_maps_update_begin(void)
28{
29 mutex_lock(&cpu_add_remove_lock);
30}
31
32void cpu_maps_update_done(void)
33{
34 mutex_unlock(&cpu_add_remove_lock);
35}
36
37static RAW_NOTIFIER_HEAD(cpu_chain);
38
39/* If set, cpu_up and cpu_down will return -EBUSY and do nothing.
40 * Should always be manipulated under cpu_add_remove_lock
41 */
42static int cpu_hotplug_disabled;
43
44#ifdef CONFIG_HOTPLUG_CPU
45
46static struct {
47 struct task_struct *active_writer;
48 struct mutex lock; /* Synchronizes accesses to refcount, */
49 /*
50 * Also blocks the new readers during
51 * an ongoing cpu hotplug operation.
52 */
53 int refcount;
54} cpu_hotplug = {
55 .active_writer = NULL,
56 .lock = __MUTEX_INITIALIZER(cpu_hotplug.lock),
57 .refcount = 0,
58};
59
60void get_online_cpus(void)
61{
62 might_sleep();
63 if (cpu_hotplug.active_writer == current)
64 return;
65 mutex_lock(&cpu_hotplug.lock);
66 cpu_hotplug.refcount++;
67 mutex_unlock(&cpu_hotplug.lock);
68
69}
70EXPORT_SYMBOL_GPL(get_online_cpus);
71
72void put_online_cpus(void)
73{
74 if (cpu_hotplug.active_writer == current)
75 return;
76 mutex_lock(&cpu_hotplug.lock);
77 if (!--cpu_hotplug.refcount && unlikely(cpu_hotplug.active_writer))
78 wake_up_process(cpu_hotplug.active_writer);
79 mutex_unlock(&cpu_hotplug.lock);
80
81}
82EXPORT_SYMBOL_GPL(put_online_cpus);
83
84/*
85 * This ensures that the hotplug operation can begin only when the
86 * refcount goes to zero.
87 *
88 * Note that during a cpu-hotplug operation, the new readers, if any,
89 * will be blocked by the cpu_hotplug.lock
90 *
91 * Since cpu_hotplug_begin() is always called after invoking
92 * cpu_maps_update_begin(), we can be sure that only one writer is active.
93 *
94 * Note that theoretically, there is a possibility of a livelock:
95 * - Refcount goes to zero, last reader wakes up the sleeping
96 * writer.
97 * - Last reader unlocks the cpu_hotplug.lock.
98 * - A new reader arrives at this moment, bumps up the refcount.
99 * - The writer acquires the cpu_hotplug.lock finds the refcount
100 * non zero and goes to sleep again.
101 *
102 * However, this is very difficult to achieve in practice since
103 * get_online_cpus() not an api which is called all that often.
104 *
105 */
106static void cpu_hotplug_begin(void)
107{
108 cpu_hotplug.active_writer = current;
109
110 for (;;) {
111 mutex_lock(&cpu_hotplug.lock);
112 if (likely(!cpu_hotplug.refcount))
113 break;
114 __set_current_state(TASK_UNINTERRUPTIBLE);
115 mutex_unlock(&cpu_hotplug.lock);
116 schedule();
117 }
118}
119
120static void cpu_hotplug_done(void)
121{
122 cpu_hotplug.active_writer = NULL;
123 mutex_unlock(&cpu_hotplug.lock);
124}
125
126#else /* #if CONFIG_HOTPLUG_CPU */
127static void cpu_hotplug_begin(void) {}
128static void cpu_hotplug_done(void) {}
129#endif /* #else #if CONFIG_HOTPLUG_CPU */
130
131/* Need to know about CPUs going up/down? */
132int __ref register_cpu_notifier(struct notifier_block *nb)
133{
134 int ret;
135 cpu_maps_update_begin();
136 ret = raw_notifier_chain_register(&cpu_chain, nb);
137 cpu_maps_update_done();
138 return ret;
139}
140
141static int __cpu_notify(unsigned long val, void *v, int nr_to_call,
142 int *nr_calls)
143{
144 int ret;
145
146 ret = __raw_notifier_call_chain(&cpu_chain, val, v, nr_to_call,
147 nr_calls);
148
149 return notifier_to_errno(ret);
150}
151
152static int cpu_notify(unsigned long val, void *v)
153{
154 return __cpu_notify(val, v, -1, NULL);
155}
156
157#ifdef CONFIG_HOTPLUG_CPU
158
159static void cpu_notify_nofail(unsigned long val, void *v)
160{
161 BUG_ON(cpu_notify(val, v));
162}
163EXPORT_SYMBOL(register_cpu_notifier);
164
165void __ref unregister_cpu_notifier(struct notifier_block *nb)
166{
167 cpu_maps_update_begin();
168 raw_notifier_chain_unregister(&cpu_chain, nb);
169 cpu_maps_update_done();
170}
171EXPORT_SYMBOL(unregister_cpu_notifier);
172
173static inline void check_for_tasks(int cpu)
174{
175 struct task_struct *p;
176
177 write_lock_irq(&tasklist_lock);
178 for_each_process(p) {
179 if (task_cpu(p) == cpu && p->state == TASK_RUNNING &&
180 (!cputime_eq(p->utime, cputime_zero) ||
181 !cputime_eq(p->stime, cputime_zero)))
182 printk(KERN_WARNING "Task %s (pid = %d) is on cpu %d "
183 "(state = %ld, flags = %x)\n",
184 p->comm, task_pid_nr(p), cpu,
185 p->state, p->flags);
186 }
187 write_unlock_irq(&tasklist_lock);
188}
189
190struct take_cpu_down_param {
191 unsigned long mod;
192 void *hcpu;
193};
194
195/* Take this CPU down. */
196static int __ref take_cpu_down(void *_param)
197{
198 struct take_cpu_down_param *param = _param;
199 int err;
200
201 /* Ensure this CPU doesn't handle any more interrupts. */
202 err = __cpu_disable();
203 if (err < 0)
204 return err;
205
206 cpu_notify(CPU_DYING | param->mod, param->hcpu);
207 return 0;
208}
209
210/* Requires cpu_add_remove_lock to be held */
211static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
212{
213 int err, nr_calls = 0;
214 void *hcpu = (void *)(long)cpu;
215 unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
216 struct take_cpu_down_param tcd_param = {
217 .mod = mod,
218 .hcpu = hcpu,
219 };
220
221 if (num_online_cpus() == 1)
222 return -EBUSY;
223
224 if (!cpu_online(cpu))
225 return -EINVAL;
226
227 cpu_hotplug_begin();
228
229 err = __cpu_notify(CPU_DOWN_PREPARE | mod, hcpu, -1, &nr_calls);
230 if (err) {
231 nr_calls--;
232 __cpu_notify(CPU_DOWN_FAILED | mod, hcpu, nr_calls, NULL);
233 printk("%s: attempt to take down CPU %u failed\n",
234 __func__, cpu);
235 goto out_release;
236 }
237
238 err = __stop_machine(take_cpu_down, &tcd_param, cpumask_of(cpu));
239 if (err) {
240 /* CPU didn't die: tell everyone. Can't complain. */
241 cpu_notify_nofail(CPU_DOWN_FAILED | mod, hcpu);
242
243 goto out_release;
244 }
245 BUG_ON(cpu_online(cpu));
246
247 /*
248 * The migration_call() CPU_DYING callback will have removed all
249 * runnable tasks from the cpu, there's only the idle task left now
250 * that the migration thread is done doing the stop_machine thing.
251 *
252 * Wait for the stop thread to go away.
253 */
254 while (!idle_cpu(cpu))
255 cpu_relax();
256
257 /* This actually kills the CPU. */
258 __cpu_die(cpu);
259
260 /* CPU is completely dead: tell everyone. Too late to complain. */
261 cpu_notify_nofail(CPU_DEAD | mod, hcpu);
262
263 check_for_tasks(cpu);
264
265out_release:
266 cpu_hotplug_done();
267 if (!err)
268 cpu_notify_nofail(CPU_POST_DEAD | mod, hcpu);
269 return err;
270}
271
272int __ref cpu_down(unsigned int cpu)
273{
274 int err;
275
276 cpu_maps_update_begin();
277
278 if (cpu_hotplug_disabled) {
279 err = -EBUSY;
280 goto out;
281 }
282
283 err = _cpu_down(cpu, 0);
284
285out:
286 cpu_maps_update_done();
287 return err;
288}
289EXPORT_SYMBOL(cpu_down);
290#endif /*CONFIG_HOTPLUG_CPU*/
291
292/* Requires cpu_add_remove_lock to be held */
293static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen)
294{
295 int ret, nr_calls = 0;
296 void *hcpu = (void *)(long)cpu;
297 unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
298
299 if (cpu_online(cpu) || !cpu_present(cpu))
300 return -EINVAL;
301
302 cpu_hotplug_begin();
303 ret = __cpu_notify(CPU_UP_PREPARE | mod, hcpu, -1, &nr_calls);
304 if (ret) {
305 nr_calls--;
306 printk(KERN_WARNING "%s: attempt to bring up CPU %u failed\n",
307 __func__, cpu);
308 goto out_notify;
309 }
310
311 /* Arch-specific enabling code. */
312 ret = __cpu_up(cpu);
313 if (ret != 0)
314 goto out_notify;
315 BUG_ON(!cpu_online(cpu));
316
317 /* Now call notifier in preparation. */
318 cpu_notify(CPU_ONLINE | mod, hcpu);
319
320out_notify:
321 if (ret != 0)
322 __cpu_notify(CPU_UP_CANCELED | mod, hcpu, nr_calls, NULL);
323 cpu_hotplug_done();
324
325 return ret;
326}
327
328int __cpuinit cpu_up(unsigned int cpu)
329{
330 int err = 0;
331
332#ifdef CONFIG_MEMORY_HOTPLUG
333 int nid;
334 pg_data_t *pgdat;
335#endif
336
337 if (!cpu_possible(cpu)) {
338 printk(KERN_ERR "can't online cpu %d because it is not "
339 "configured as may-hotadd at boot time\n", cpu);
340#if defined(CONFIG_IA64)
341 printk(KERN_ERR "please check additional_cpus= boot "
342 "parameter\n");
343#endif
344 return -EINVAL;
345 }
346
347#ifdef CONFIG_MEMORY_HOTPLUG
348 nid = cpu_to_node(cpu);
349 if (!node_online(nid)) {
350 err = mem_online_node(nid);
351 if (err)
352 return err;
353 }
354
355 pgdat = NODE_DATA(nid);
356 if (!pgdat) {
357 printk(KERN_ERR
358 "Can't online cpu %d due to NULL pgdat\n", cpu);
359 return -ENOMEM;
360 }
361
362 if (pgdat->node_zonelists->_zonerefs->zone == NULL) {
363 mutex_lock(&zonelists_mutex);
364 build_all_zonelists(NULL);
365 mutex_unlock(&zonelists_mutex);
366 }
367#endif
368
369 cpu_maps_update_begin();
370
371 if (cpu_hotplug_disabled) {
372 err = -EBUSY;
373 goto out;
374 }
375
376 err = _cpu_up(cpu, 0);
377
378out:
379 cpu_maps_update_done();
380 return err;
381}
382
383#ifdef CONFIG_PM_SLEEP_SMP
384static cpumask_var_t frozen_cpus;
385
386void __weak arch_disable_nonboot_cpus_begin(void)
387{
388}
389
390void __weak arch_disable_nonboot_cpus_end(void)
391{
392}
393
394int disable_nonboot_cpus(void)
395{
396 int cpu, first_cpu, error = 0;
397
398 cpu_maps_update_begin();
399 first_cpu = cpumask_first(cpu_online_mask);
400 /*
401 * We take down all of the non-boot CPUs in one shot to avoid races
402 * with the userspace trying to use the CPU hotplug at the same time
403 */
404 cpumask_clear(frozen_cpus);
405 arch_disable_nonboot_cpus_begin();
406
407 printk("Disabling non-boot CPUs ...\n");
408 for_each_online_cpu(cpu) {
409 if (cpu == first_cpu)
410 continue;
411 error = _cpu_down(cpu, 1);
412 if (!error)
413 cpumask_set_cpu(cpu, frozen_cpus);
414 else {
415 printk(KERN_ERR "Error taking CPU%d down: %d\n",
416 cpu, error);
417 break;
418 }
419 }
420
421 arch_disable_nonboot_cpus_end();
422
423 if (!error) {
424 BUG_ON(num_online_cpus() > 1);
425 /* Make sure the CPUs won't be enabled by someone else */
426 cpu_hotplug_disabled = 1;
427 } else {
428 printk(KERN_ERR "Non-boot CPUs are not disabled\n");
429 }
430 cpu_maps_update_done();
431 return error;
432}
433
434void __weak arch_enable_nonboot_cpus_begin(void)
435{
436}
437
438void __weak arch_enable_nonboot_cpus_end(void)
439{
440}
441
442void __ref enable_nonboot_cpus(void)
443{
444 int cpu, error;
445
446 /* Allow everyone to use the CPU hotplug again */
447 cpu_maps_update_begin();
448 cpu_hotplug_disabled = 0;
449 if (cpumask_empty(frozen_cpus))
450 goto out;
451
452 printk(KERN_INFO "Enabling non-boot CPUs ...\n");
453
454 arch_enable_nonboot_cpus_begin();
455
456 for_each_cpu(cpu, frozen_cpus) {
457 error = _cpu_up(cpu, 1);
458 if (!error) {
459 printk(KERN_INFO "CPU%d is up\n", cpu);
460 continue;
461 }
462 printk(KERN_WARNING "Error taking CPU%d up: %d\n", cpu, error);
463 }
464
465 arch_enable_nonboot_cpus_end();
466
467 cpumask_clear(frozen_cpus);
468out:
469 cpu_maps_update_done();
470}
471
472static int alloc_frozen_cpus(void)
473{
474 if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
475 return -ENOMEM;
476 return 0;
477}
478core_initcall(alloc_frozen_cpus);
479#endif /* CONFIG_PM_SLEEP_SMP */
480
481/**
482 * notify_cpu_starting(cpu) - call the CPU_STARTING notifiers
483 * @cpu: cpu that just started
484 *
485 * This function calls the cpu_chain notifiers with CPU_STARTING.
486 * It must be called by the arch code on the new cpu, before the new cpu
487 * enables interrupts and before the "boot" cpu returns from __cpu_up().
488 */
489void __cpuinit notify_cpu_starting(unsigned int cpu)
490{
491 unsigned long val = CPU_STARTING;
492
493#ifdef CONFIG_PM_SLEEP_SMP
494 if (frozen_cpus != NULL && cpumask_test_cpu(cpu, frozen_cpus))
495 val = CPU_STARTING_FROZEN;
496#endif /* CONFIG_PM_SLEEP_SMP */
497 cpu_notify(val, (void *)(long)cpu);
498}
499
500#endif /* CONFIG_SMP */
501
502/*
503 * cpu_bit_bitmap[] is a special, "compressed" data structure that
504 * represents all NR_CPUS bits binary values of 1<<nr.
505 *
506 * It is used by cpumask_of() to get a constant address to a CPU
507 * mask value that has a single bit set only.
508 */
509
510/* cpu_bit_bitmap[0] is empty - so we can back into it */
511#define MASK_DECLARE_1(x) [x+1][0] = (1UL << (x))
512#define MASK_DECLARE_2(x) MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
513#define MASK_DECLARE_4(x) MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
514#define MASK_DECLARE_8(x) MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
515
516const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
517
518 MASK_DECLARE_8(0), MASK_DECLARE_8(8),
519 MASK_DECLARE_8(16), MASK_DECLARE_8(24),
520#if BITS_PER_LONG > 32
521 MASK_DECLARE_8(32), MASK_DECLARE_8(40),
522 MASK_DECLARE_8(48), MASK_DECLARE_8(56),
523#endif
524};
525EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
526
527const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
528EXPORT_SYMBOL(cpu_all_bits);
529
530#ifdef CONFIG_INIT_ALL_POSSIBLE
531static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly
532 = CPU_BITS_ALL;
533#else
534static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly;
535#endif
536const struct cpumask *const cpu_possible_mask = to_cpumask(cpu_possible_bits);
537EXPORT_SYMBOL(cpu_possible_mask);
538
539static DECLARE_BITMAP(cpu_online_bits, CONFIG_NR_CPUS) __read_mostly;
540const struct cpumask *const cpu_online_mask = to_cpumask(cpu_online_bits);
541EXPORT_SYMBOL(cpu_online_mask);
542
543static DECLARE_BITMAP(cpu_present_bits, CONFIG_NR_CPUS) __read_mostly;
544const struct cpumask *const cpu_present_mask = to_cpumask(cpu_present_bits);
545EXPORT_SYMBOL(cpu_present_mask);
546
547static DECLARE_BITMAP(cpu_active_bits, CONFIG_NR_CPUS) __read_mostly;
548const struct cpumask *const cpu_active_mask = to_cpumask(cpu_active_bits);
549EXPORT_SYMBOL(cpu_active_mask);
550
551void set_cpu_possible(unsigned int cpu, bool possible)
552{
553 if (possible)
554 cpumask_set_cpu(cpu, to_cpumask(cpu_possible_bits));
555 else
556 cpumask_clear_cpu(cpu, to_cpumask(cpu_possible_bits));
557}
558
559void set_cpu_present(unsigned int cpu, bool present)
560{
561 if (present)
562 cpumask_set_cpu(cpu, to_cpumask(cpu_present_bits));
563 else
564 cpumask_clear_cpu(cpu, to_cpumask(cpu_present_bits));
565}
566
567void set_cpu_online(unsigned int cpu, bool online)
568{
569 if (online)
570 cpumask_set_cpu(cpu, to_cpumask(cpu_online_bits));
571 else
572 cpumask_clear_cpu(cpu, to_cpumask(cpu_online_bits));
573}
574
575void set_cpu_active(unsigned int cpu, bool active)
576{
577 if (active)
578 cpumask_set_cpu(cpu, to_cpumask(cpu_active_bits));
579 else
580 cpumask_clear_cpu(cpu, to_cpumask(cpu_active_bits));
581}
582
583void init_cpu_present(const struct cpumask *src)
584{
585 cpumask_copy(to_cpumask(cpu_present_bits), src);
586}
587
588void init_cpu_possible(const struct cpumask *src)
589{
590 cpumask_copy(to_cpumask(cpu_possible_bits), src);
591}
592
593void init_cpu_online(const struct cpumask *src)
594{
595 cpumask_copy(to_cpumask(cpu_online_bits), src);
596}