projects/linux·blob v2.6.30-rc6 · refs

567 lines · 13.8 KiB

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
18#ifdef CONFIG_SMP
19/* Serializes the updates to cpu_online_mask, cpu_present_mask */
20static DEFINE_MUTEX(cpu_add_remove_lock);
21
22static __cpuinitdata RAW_NOTIFIER_HEAD(cpu_chain);
23
24/* If set, cpu_up and cpu_down will return -EBUSY and do nothing.
25 * Should always be manipulated under cpu_add_remove_lock
26 */
27static int cpu_hotplug_disabled;
28
29static struct {
30 struct task_struct *active_writer;
31 struct mutex lock; /* Synchronizes accesses to refcount, */
32 /*
33 * Also blocks the new readers during
34 * an ongoing cpu hotplug operation.
35 */
36 int refcount;
37} cpu_hotplug;
38
39void __init cpu_hotplug_init(void)
40{
41 cpu_hotplug.active_writer = NULL;
42 mutex_init(&cpu_hotplug.lock);
43 cpu_hotplug.refcount = 0;
44}
45
46#ifdef CONFIG_HOTPLUG_CPU
47
48void get_online_cpus(void)
49{
50 might_sleep();
51 if (cpu_hotplug.active_writer == current)
52 return;
53 mutex_lock(&cpu_hotplug.lock);
54 cpu_hotplug.refcount++;
55 mutex_unlock(&cpu_hotplug.lock);
56
57}
58EXPORT_SYMBOL_GPL(get_online_cpus);
59
60void put_online_cpus(void)
61{
62 if (cpu_hotplug.active_writer == current)
63 return;
64 mutex_lock(&cpu_hotplug.lock);
65 if (!--cpu_hotplug.refcount && unlikely(cpu_hotplug.active_writer))
66 wake_up_process(cpu_hotplug.active_writer);
67 mutex_unlock(&cpu_hotplug.lock);
68
69}
70EXPORT_SYMBOL_GPL(put_online_cpus);
71
72#endif /* CONFIG_HOTPLUG_CPU */
73
74/*
75 * The following two API's must be used when attempting
76 * to serialize the updates to cpu_online_mask, cpu_present_mask.
77 */
78void cpu_maps_update_begin(void)
79{
80 mutex_lock(&cpu_add_remove_lock);
81}
82
83void cpu_maps_update_done(void)
84{
85 mutex_unlock(&cpu_add_remove_lock);
86}
87
88/*
89 * This ensures that the hotplug operation can begin only when the
90 * refcount goes to zero.
91 *
92 * Note that during a cpu-hotplug operation, the new readers, if any,
93 * will be blocked by the cpu_hotplug.lock
94 *
95 * Since cpu_hotplug_begin() is always called after invoking
96 * cpu_maps_update_begin(), we can be sure that only one writer is active.
97 *
98 * Note that theoretically, there is a possibility of a livelock:
99 * - Refcount goes to zero, last reader wakes up the sleeping
100 * writer.
101 * - Last reader unlocks the cpu_hotplug.lock.
102 * - A new reader arrives at this moment, bumps up the refcount.
103 * - The writer acquires the cpu_hotplug.lock finds the refcount
104 * non zero and goes to sleep again.
105 *
106 * However, this is very difficult to achieve in practice since
107 * get_online_cpus() not an api which is called all that often.
108 *
109 */
110static void cpu_hotplug_begin(void)
111{
112 cpu_hotplug.active_writer = current;
113
114 for (;;) {
115 mutex_lock(&cpu_hotplug.lock);
116 if (likely(!cpu_hotplug.refcount))
117 break;
118 __set_current_state(TASK_UNINTERRUPTIBLE);
119 mutex_unlock(&cpu_hotplug.lock);
120 schedule();
121 }
122}
123
124static void cpu_hotplug_done(void)
125{
126 cpu_hotplug.active_writer = NULL;
127 mutex_unlock(&cpu_hotplug.lock);
128}
129/* Need to know about CPUs going up/down? */
130int __ref register_cpu_notifier(struct notifier_block *nb)
131{
132 int ret;
133 cpu_maps_update_begin();
134 ret = raw_notifier_chain_register(&cpu_chain, nb);
135 cpu_maps_update_done();
136 return ret;
137}
138
139#ifdef CONFIG_HOTPLUG_CPU
140
141EXPORT_SYMBOL(register_cpu_notifier);
142
143void __ref unregister_cpu_notifier(struct notifier_block *nb)
144{
145 cpu_maps_update_begin();
146 raw_notifier_chain_unregister(&cpu_chain, nb);
147 cpu_maps_update_done();
148}
149EXPORT_SYMBOL(unregister_cpu_notifier);
150
151static inline void check_for_tasks(int cpu)
152{
153 struct task_struct *p;
154
155 write_lock_irq(&tasklist_lock);
156 for_each_process(p) {
157 if (task_cpu(p) == cpu &&
158 (!cputime_eq(p->utime, cputime_zero) ||
159 !cputime_eq(p->stime, cputime_zero)))
160 printk(KERN_WARNING "Task %s (pid = %d) is on cpu %d\
161 (state = %ld, flags = %x) \n",
162 p->comm, task_pid_nr(p), cpu,
163 p->state, p->flags);
164 }
165 write_unlock_irq(&tasklist_lock);
166}
167
168struct take_cpu_down_param {
169 unsigned long mod;
170 void *hcpu;
171};
172
173/* Take this CPU down. */
174static int __ref take_cpu_down(void *_param)
175{
176 struct take_cpu_down_param *param = _param;
177 int err;
178
179 /* Ensure this CPU doesn't handle any more interrupts. */
180 err = __cpu_disable();
181 if (err < 0)
182 return err;
183
184 raw_notifier_call_chain(&cpu_chain, CPU_DYING | param->mod,
185 param->hcpu);
186
187 /* Force idle task to run as soon as we yield: it should
188 immediately notice cpu is offline and die quickly. */
189 sched_idle_next();
190 return 0;
191}
192
193/* Requires cpu_add_remove_lock to be held */
194static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
195{
196 int err, nr_calls = 0;
197 cpumask_var_t old_allowed;
198 void *hcpu = (void *)(long)cpu;
199 unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
200 struct take_cpu_down_param tcd_param = {
201 .mod = mod,
202 .hcpu = hcpu,
203 };
204
205 if (num_online_cpus() == 1)
206 return -EBUSY;
207
208 if (!cpu_online(cpu))
209 return -EINVAL;
210
211 if (!alloc_cpumask_var(&old_allowed, GFP_KERNEL))
212 return -ENOMEM;
213
214 cpu_hotplug_begin();
215 err = __raw_notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE | mod,
216 hcpu, -1, &nr_calls);
217 if (err == NOTIFY_BAD) {
218 nr_calls--;
219 __raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED | mod,
220 hcpu, nr_calls, NULL);
221 printk("%s: attempt to take down CPU %u failed\n",
222 __func__, cpu);
223 err = -EINVAL;
224 goto out_release;
225 }
226
227 /* Ensure that we are not runnable on dying cpu */
228 cpumask_copy(old_allowed, &current->cpus_allowed);
229 set_cpus_allowed_ptr(current,
230 cpumask_of(cpumask_any_but(cpu_online_mask, cpu)));
231
232 err = __stop_machine(take_cpu_down, &tcd_param, cpumask_of(cpu));
233 if (err) {
234 /* CPU didn't die: tell everyone. Can't complain. */
235 if (raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED | mod,
236 hcpu) == NOTIFY_BAD)
237 BUG();
238
239 goto out_allowed;
240 }
241 BUG_ON(cpu_online(cpu));
242
243 /* Wait for it to sleep (leaving idle task). */
244 while (!idle_cpu(cpu))
245 yield();
246
247 /* This actually kills the CPU. */
248 __cpu_die(cpu);
249
250 /* CPU is completely dead: tell everyone. Too late to complain. */
251 if (raw_notifier_call_chain(&cpu_chain, CPU_DEAD | mod,
252 hcpu) == NOTIFY_BAD)
253 BUG();
254
255 check_for_tasks(cpu);
256
257out_allowed:
258 set_cpus_allowed_ptr(current, old_allowed);
259out_release:
260 cpu_hotplug_done();
261 if (!err) {
262 if (raw_notifier_call_chain(&cpu_chain, CPU_POST_DEAD | mod,
263 hcpu) == NOTIFY_BAD)
264 BUG();
265 }
266 free_cpumask_var(old_allowed);
267 return err;
268}
269
270int __ref cpu_down(unsigned int cpu)
271{
272 int err;
273
274 err = stop_machine_create();
275 if (err)
276 return err;
277 cpu_maps_update_begin();
278
279 if (cpu_hotplug_disabled) {
280 err = -EBUSY;
281 goto out;
282 }
283
284 set_cpu_active(cpu, false);
285
286 /*
287 * Make sure the all cpus did the reschedule and are not
288 * using stale version of the cpu_active_mask.
289 * This is not strictly necessary becuase stop_machine()
290 * that we run down the line already provides the required
291 * synchronization. But it's really a side effect and we do not
292 * want to depend on the innards of the stop_machine here.
293 */
294 synchronize_sched();
295
296 err = _cpu_down(cpu, 0);
297
298 if (cpu_online(cpu))
299 set_cpu_active(cpu, true);
300
301out:
302 cpu_maps_update_done();
303 stop_machine_destroy();
304 return err;
305}
306EXPORT_SYMBOL(cpu_down);
307#endif /*CONFIG_HOTPLUG_CPU*/
308
309/* Requires cpu_add_remove_lock to be held */
310static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen)
311{
312 int ret, nr_calls = 0;
313 void *hcpu = (void *)(long)cpu;
314 unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
315
316 if (cpu_online(cpu) || !cpu_present(cpu))
317 return -EINVAL;
318
319 cpu_hotplug_begin();
320 ret = __raw_notifier_call_chain(&cpu_chain, CPU_UP_PREPARE | mod, hcpu,
321 -1, &nr_calls);
322 if (ret == NOTIFY_BAD) {
323 nr_calls--;
324 printk("%s: attempt to bring up CPU %u failed\n",
325 __func__, cpu);
326 ret = -EINVAL;
327 goto out_notify;
328 }
329
330 /* Arch-specific enabling code. */
331 ret = __cpu_up(cpu);
332 if (ret != 0)
333 goto out_notify;
334 BUG_ON(!cpu_online(cpu));
335
336 set_cpu_active(cpu, true);
337
338 /* Now call notifier in preparation. */
339 raw_notifier_call_chain(&cpu_chain, CPU_ONLINE | mod, hcpu);
340
341out_notify:
342 if (ret != 0)
343 __raw_notifier_call_chain(&cpu_chain,
344 CPU_UP_CANCELED | mod, hcpu, nr_calls, NULL);
345 cpu_hotplug_done();
346
347 return ret;
348}
349
350int __cpuinit cpu_up(unsigned int cpu)
351{
352 int err = 0;
353 if (!cpu_possible(cpu)) {
354 printk(KERN_ERR "can't online cpu %d because it is not "
355 "configured as may-hotadd at boot time\n", cpu);
356#if defined(CONFIG_IA64) || defined(CONFIG_X86_64)
357 printk(KERN_ERR "please check additional_cpus= boot "
358 "parameter\n");
359#endif
360 return -EINVAL;
361 }
362
363 cpu_maps_update_begin();
364
365 if (cpu_hotplug_disabled) {
366 err = -EBUSY;
367 goto out;
368 }
369
370 err = _cpu_up(cpu, 0);
371
372out:
373 cpu_maps_update_done();
374 return err;
375}
376
377#ifdef CONFIG_PM_SLEEP_SMP
378static cpumask_var_t frozen_cpus;
379
380int disable_nonboot_cpus(void)
381{
382 int cpu, first_cpu, error;
383
384 error = stop_machine_create();
385 if (error)
386 return error;
387 cpu_maps_update_begin();
388 first_cpu = cpumask_first(cpu_online_mask);
389 /* We take down all of the non-boot CPUs in one shot to avoid races
390 * with the userspace trying to use the CPU hotplug at the same time
391 */
392 cpumask_clear(frozen_cpus);
393 printk("Disabling non-boot CPUs ...\n");
394 for_each_online_cpu(cpu) {
395 if (cpu == first_cpu)
396 continue;
397 error = _cpu_down(cpu, 1);
398 if (!error) {
399 cpumask_set_cpu(cpu, frozen_cpus);
400 printk("CPU%d is down\n", cpu);
401 } else {
402 printk(KERN_ERR "Error taking CPU%d down: %d\n",
403 cpu, error);
404 break;
405 }
406 }
407 if (!error) {
408 BUG_ON(num_online_cpus() > 1);
409 /* Make sure the CPUs won't be enabled by someone else */
410 cpu_hotplug_disabled = 1;
411 } else {
412 printk(KERN_ERR "Non-boot CPUs are not disabled\n");
413 }
414 cpu_maps_update_done();
415 stop_machine_destroy();
416 return error;
417}
418
419void __ref enable_nonboot_cpus(void)
420{
421 int cpu, error;
422
423 /* Allow everyone to use the CPU hotplug again */
424 cpu_maps_update_begin();
425 cpu_hotplug_disabled = 0;
426 if (cpumask_empty(frozen_cpus))
427 goto out;
428
429 printk("Enabling non-boot CPUs ...\n");
430 for_each_cpu(cpu, frozen_cpus) {
431 error = _cpu_up(cpu, 1);
432 if (!error) {
433 printk("CPU%d is up\n", cpu);
434 continue;
435 }
436 printk(KERN_WARNING "Error taking CPU%d up: %d\n", cpu, error);
437 }
438 cpumask_clear(frozen_cpus);
439out:
440 cpu_maps_update_done();
441}
442
443static int alloc_frozen_cpus(void)
444{
445 if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
446 return -ENOMEM;
447 return 0;
448}
449core_initcall(alloc_frozen_cpus);
450#endif /* CONFIG_PM_SLEEP_SMP */
451
452/**
453 * notify_cpu_starting(cpu) - call the CPU_STARTING notifiers
454 * @cpu: cpu that just started
455 *
456 * This function calls the cpu_chain notifiers with CPU_STARTING.
457 * It must be called by the arch code on the new cpu, before the new cpu
458 * enables interrupts and before the "boot" cpu returns from __cpu_up().
459 */
460void __cpuinit notify_cpu_starting(unsigned int cpu)
461{
462 unsigned long val = CPU_STARTING;
463
464#ifdef CONFIG_PM_SLEEP_SMP
465 if (frozen_cpus != NULL && cpumask_test_cpu(cpu, frozen_cpus))
466 val = CPU_STARTING_FROZEN;
467#endif /* CONFIG_PM_SLEEP_SMP */
468 raw_notifier_call_chain(&cpu_chain, val, (void *)(long)cpu);
469}
470
471#endif /* CONFIG_SMP */
472
473/*
474 * cpu_bit_bitmap[] is a special, "compressed" data structure that
475 * represents all NR_CPUS bits binary values of 1<<nr.
476 *
477 * It is used by cpumask_of() to get a constant address to a CPU
478 * mask value that has a single bit set only.
479 */
480
481/* cpu_bit_bitmap[0] is empty - so we can back into it */
482#define MASK_DECLARE_1(x) [x+1][0] = 1UL << (x)
483#define MASK_DECLARE_2(x) MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
484#define MASK_DECLARE_4(x) MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
485#define MASK_DECLARE_8(x) MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
486
487const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
488
489 MASK_DECLARE_8(0), MASK_DECLARE_8(8),
490 MASK_DECLARE_8(16), MASK_DECLARE_8(24),
491#if BITS_PER_LONG > 32
492 MASK_DECLARE_8(32), MASK_DECLARE_8(40),
493 MASK_DECLARE_8(48), MASK_DECLARE_8(56),
494#endif
495};
496EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
497
498const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
499EXPORT_SYMBOL(cpu_all_bits);
500
501#ifdef CONFIG_INIT_ALL_POSSIBLE
502static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly
503 = CPU_BITS_ALL;
504#else
505static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly;
506#endif
507const struct cpumask *const cpu_possible_mask = to_cpumask(cpu_possible_bits);
508EXPORT_SYMBOL(cpu_possible_mask);
509
510static DECLARE_BITMAP(cpu_online_bits, CONFIG_NR_CPUS) __read_mostly;
511const struct cpumask *const cpu_online_mask = to_cpumask(cpu_online_bits);
512EXPORT_SYMBOL(cpu_online_mask);
513
514static DECLARE_BITMAP(cpu_present_bits, CONFIG_NR_CPUS) __read_mostly;
515const struct cpumask *const cpu_present_mask = to_cpumask(cpu_present_bits);
516EXPORT_SYMBOL(cpu_present_mask);
517
518static DECLARE_BITMAP(cpu_active_bits, CONFIG_NR_CPUS) __read_mostly;
519const struct cpumask *const cpu_active_mask = to_cpumask(cpu_active_bits);
520EXPORT_SYMBOL(cpu_active_mask);
521
522void set_cpu_possible(unsigned int cpu, bool possible)
523{
524 if (possible)
525 cpumask_set_cpu(cpu, to_cpumask(cpu_possible_bits));
526 else
527 cpumask_clear_cpu(cpu, to_cpumask(cpu_possible_bits));
528}
529
530void set_cpu_present(unsigned int cpu, bool present)
531{
532 if (present)
533 cpumask_set_cpu(cpu, to_cpumask(cpu_present_bits));
534 else
535 cpumask_clear_cpu(cpu, to_cpumask(cpu_present_bits));
536}
537
538void set_cpu_online(unsigned int cpu, bool online)
539{
540 if (online)
541 cpumask_set_cpu(cpu, to_cpumask(cpu_online_bits));
542 else
543 cpumask_clear_cpu(cpu, to_cpumask(cpu_online_bits));
544}
545
546void set_cpu_active(unsigned int cpu, bool active)
547{
548 if (active)
549 cpumask_set_cpu(cpu, to_cpumask(cpu_active_bits));
550 else
551 cpumask_clear_cpu(cpu, to_cpumask(cpu_active_bits));
552}
553
554void init_cpu_present(const struct cpumask *src)
555{
556 cpumask_copy(to_cpumask(cpu_present_bits), src);
557}
558
559void init_cpu_possible(const struct cpumask *src)
560{
561 cpumask_copy(to_cpumask(cpu_possible_bits), src);
562}
563
564void init_cpu_online(const struct cpumask *src)
565{
566 cpumask_copy(to_cpumask(cpu_online_bits), src);
567}