projects/linux·blob v2.6.34-rc6 · refs

569 lines · 13.5 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#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
23static __cpuinitdata RAW_NOTIFIER_HEAD(cpu_chain);
24
25/* If set, cpu_up and cpu_down will return -EBUSY and do nothing.
26 * Should always be manipulated under cpu_add_remove_lock
27 */
28static int cpu_hotplug_disabled;
29
30static struct {
31 struct task_struct *active_writer;
32 struct mutex lock; /* Synchronizes accesses to refcount, */
33 /*
34 * Also blocks the new readers during
35 * an ongoing cpu hotplug operation.
36 */
37 int refcount;
38} cpu_hotplug = {
39 .active_writer = NULL,
40 .lock = __MUTEX_INITIALIZER(cpu_hotplug.lock),
41 .refcount = 0,
42};
43
44#ifdef CONFIG_HOTPLUG_CPU
45
46void get_online_cpus(void)
47{
48 might_sleep();
49 if (cpu_hotplug.active_writer == current)
50 return;
51 mutex_lock(&cpu_hotplug.lock);
52 cpu_hotplug.refcount++;
53 mutex_unlock(&cpu_hotplug.lock);
54
55}
56EXPORT_SYMBOL_GPL(get_online_cpus);
57
58void put_online_cpus(void)
59{
60 if (cpu_hotplug.active_writer == current)
61 return;
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);
66
67}
68EXPORT_SYMBOL_GPL(put_online_cpus);
69
70#endif /* CONFIG_HOTPLUG_CPU */
71
72/*
73 * The following two API's must be used when attempting
74 * to serialize the updates to cpu_online_mask, cpu_present_mask.
75 */
76void cpu_maps_update_begin(void)
77{
78 mutex_lock(&cpu_add_remove_lock);
79}
80
81void cpu_maps_update_done(void)
82{
83 mutex_unlock(&cpu_add_remove_lock);
84}
85
86/*
87 * This ensures that the hotplug operation can begin only when the
88 * refcount goes to zero.
89 *
90 * Note that during a cpu-hotplug operation, the new readers, if any,
91 * will be blocked by the cpu_hotplug.lock
92 *
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.
95 *
96 * Note that theoretically, there is a possibility of a livelock:
97 * - Refcount goes to zero, last reader wakes up the sleeping
98 * writer.
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.
103 *
104 * However, this is very difficult to achieve in practice since
105 * get_online_cpus() not an api which is called all that often.
106 *
107 */
108static void cpu_hotplug_begin(void)
109{
110 cpu_hotplug.active_writer = current;
111
112 for (;;) {
113 mutex_lock(&cpu_hotplug.lock);
114 if (likely(!cpu_hotplug.refcount))
115 break;
116 __set_current_state(TASK_UNINTERRUPTIBLE);
117 mutex_unlock(&cpu_hotplug.lock);
118 schedule();
119 }
120}
121
122static void cpu_hotplug_done(void)
123{
124 cpu_hotplug.active_writer = NULL;
125 mutex_unlock(&cpu_hotplug.lock);
126}
127/* Need to know about CPUs going up/down? */
128int __ref register_cpu_notifier(struct notifier_block *nb)
129{
130 int ret;
131 cpu_maps_update_begin();
132 ret = raw_notifier_chain_register(&cpu_chain, nb);
133 cpu_maps_update_done();
134 return ret;
135}
136
137#ifdef CONFIG_HOTPLUG_CPU
138
139EXPORT_SYMBOL(register_cpu_notifier);
140
141void __ref unregister_cpu_notifier(struct notifier_block *nb)
142{
143 cpu_maps_update_begin();
144 raw_notifier_chain_unregister(&cpu_chain, nb);
145 cpu_maps_update_done();
146}
147EXPORT_SYMBOL(unregister_cpu_notifier);
148
149static inline void check_for_tasks(int cpu)
150{
151 struct task_struct *p;
152
153 write_lock_irq(&tasklist_lock);
154 for_each_process(p) {
155 if (task_cpu(p) == cpu && p->state == TASK_RUNNING &&
156 (!cputime_eq(p->utime, cputime_zero) ||
157 !cputime_eq(p->stime, cputime_zero)))
158 printk(KERN_WARNING "Task %s (pid = %d) is on cpu %d "
159 "(state = %ld, flags = %x)\n",
160 p->comm, task_pid_nr(p), cpu,
161 p->state, p->flags);
162 }
163 write_unlock_irq(&tasklist_lock);
164}
165
166struct take_cpu_down_param {
167 unsigned long mod;
168 void *hcpu;
169};
170
171/* Take this CPU down. */
172static int __ref take_cpu_down(void *_param)
173{
174 struct take_cpu_down_param *param = _param;
175 int err;
176
177 /* Ensure this CPU doesn't handle any more interrupts. */
178 err = __cpu_disable();
179 if (err < 0)
180 return err;
181
182 raw_notifier_call_chain(&cpu_chain, CPU_DYING | param->mod,
183 param->hcpu);
184
185 /* Force idle task to run as soon as we yield: it should
186 immediately notice cpu is offline and die quickly. */
187 sched_idle_next();
188 return 0;
189}
190
191/* Requires cpu_add_remove_lock to be held */
192static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
193{
194 int err, nr_calls = 0;
195 cpumask_var_t old_allowed;
196 void *hcpu = (void *)(long)cpu;
197 unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
198 struct take_cpu_down_param tcd_param = {
199 .mod = mod,
200 .hcpu = hcpu,
201 };
202
203 if (num_online_cpus() == 1)
204 return -EBUSY;
205
206 if (!cpu_online(cpu))
207 return -EINVAL;
208
209 if (!alloc_cpumask_var(&old_allowed, GFP_KERNEL))
210 return -ENOMEM;
211
212 cpu_hotplug_begin();
213 set_cpu_active(cpu, false);
214 err = __raw_notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE | mod,
215 hcpu, -1, &nr_calls);
216 if (err == NOTIFY_BAD) {
217 set_cpu_active(cpu, true);
218
219 nr_calls--;
220 __raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED | mod,
221 hcpu, nr_calls, NULL);
222 printk("%s: attempt to take down CPU %u failed\n",
223 __func__, cpu);
224 err = -EINVAL;
225 goto out_release;
226 }
227
228 /* Ensure that we are not runnable on dying cpu */
229 cpumask_copy(old_allowed, &current->cpus_allowed);
230 set_cpus_allowed_ptr(current, cpu_active_mask);
231
232 err = __stop_machine(take_cpu_down, &tcd_param, cpumask_of(cpu));
233 if (err) {
234 set_cpu_active(cpu, true);
235 /* CPU didn't die: tell everyone. Can't complain. */
236 if (raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED | mod,
237 hcpu) == NOTIFY_BAD)
238 BUG();
239
240 goto out_allowed;
241 }
242 BUG_ON(cpu_online(cpu));
243
244 /* Wait for it to sleep (leaving idle task). */
245 while (!idle_cpu(cpu))
246 yield();
247
248 /* This actually kills the CPU. */
249 __cpu_die(cpu);
250
251 /* CPU is completely dead: tell everyone. Too late to complain. */
252 if (raw_notifier_call_chain(&cpu_chain, CPU_DEAD | mod,
253 hcpu) == NOTIFY_BAD)
254 BUG();
255
256 check_for_tasks(cpu);
257
258out_allowed:
259 set_cpus_allowed_ptr(current, old_allowed);
260out_release:
261 cpu_hotplug_done();
262 if (!err) {
263 if (raw_notifier_call_chain(&cpu_chain, CPU_POST_DEAD | mod,
264 hcpu) == NOTIFY_BAD)
265 BUG();
266 }
267 free_cpumask_var(old_allowed);
268 return err;
269}
270
271int __ref cpu_down(unsigned int cpu)
272{
273 int err;
274
275 err = stop_machine_create();
276 if (err)
277 return err;
278 cpu_maps_update_begin();
279
280 if (cpu_hotplug_disabled) {
281 err = -EBUSY;
282 goto out;
283 }
284
285 err = _cpu_down(cpu, 0);
286
287out:
288 cpu_maps_update_done();
289 stop_machine_destroy();
290 return err;
291}
292EXPORT_SYMBOL(cpu_down);
293#endif /*CONFIG_HOTPLUG_CPU*/
294
295/* Requires cpu_add_remove_lock to be held */
296static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen)
297{
298 int ret, nr_calls = 0;
299 void *hcpu = (void *)(long)cpu;
300 unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
301
302 if (cpu_online(cpu) || !cpu_present(cpu))
303 return -EINVAL;
304
305 cpu_hotplug_begin();
306 ret = __raw_notifier_call_chain(&cpu_chain, CPU_UP_PREPARE | mod, hcpu,
307 -1, &nr_calls);
308 if (ret == NOTIFY_BAD) {
309 nr_calls--;
310 printk("%s: attempt to bring up CPU %u failed\n",
311 __func__, cpu);
312 ret = -EINVAL;
313 goto out_notify;
314 }
315
316 /* Arch-specific enabling code. */
317 ret = __cpu_up(cpu);
318 if (ret != 0)
319 goto out_notify;
320 BUG_ON(!cpu_online(cpu));
321
322 set_cpu_active(cpu, true);
323
324 /* Now call notifier in preparation. */
325 raw_notifier_call_chain(&cpu_chain, CPU_ONLINE | mod, hcpu);
326
327out_notify:
328 if (ret != 0)
329 __raw_notifier_call_chain(&cpu_chain,
330 CPU_UP_CANCELED | mod, hcpu, nr_calls, NULL);
331 cpu_hotplug_done();
332
333 return ret;
334}
335
336int __cpuinit cpu_up(unsigned int cpu)
337{
338 int err = 0;
339 if (!cpu_possible(cpu)) {
340 printk(KERN_ERR "can't online cpu %d because it is not "
341 "configured as may-hotadd at boot time\n", cpu);
342#if defined(CONFIG_IA64)
343 printk(KERN_ERR "please check additional_cpus= boot "
344 "parameter\n");
345#endif
346 return -EINVAL;
347 }
348
349 cpu_maps_update_begin();
350
351 if (cpu_hotplug_disabled) {
352 err = -EBUSY;
353 goto out;
354 }
355
356 err = _cpu_up(cpu, 0);
357
358out:
359 cpu_maps_update_done();
360 return err;
361}
362
363#ifdef CONFIG_PM_SLEEP_SMP
364static cpumask_var_t frozen_cpus;
365
366int disable_nonboot_cpus(void)
367{
368 int cpu, first_cpu, error;
369
370 error = stop_machine_create();
371 if (error)
372 return error;
373 cpu_maps_update_begin();
374 first_cpu = cpumask_first(cpu_online_mask);
375 /*
376 * We take down all of the non-boot CPUs in one shot to avoid races
377 * with the userspace trying to use the CPU hotplug at the same time
378 */
379 cpumask_clear(frozen_cpus);
380
381 printk("Disabling non-boot CPUs ...\n");
382 for_each_online_cpu(cpu) {
383 if (cpu == first_cpu)
384 continue;
385 error = _cpu_down(cpu, 1);
386 if (!error)
387 cpumask_set_cpu(cpu, frozen_cpus);
388 else {
389 printk(KERN_ERR "Error taking CPU%d down: %d\n",
390 cpu, error);
391 break;
392 }
393 }
394
395 if (!error) {
396 BUG_ON(num_online_cpus() > 1);
397 /* Make sure the CPUs won't be enabled by someone else */
398 cpu_hotplug_disabled = 1;
399 } else {
400 printk(KERN_ERR "Non-boot CPUs are not disabled\n");
401 }
402 cpu_maps_update_done();
403 stop_machine_destroy();
404 return error;
405}
406
407void __weak arch_enable_nonboot_cpus_begin(void)
408{
409}
410
411void __weak arch_enable_nonboot_cpus_end(void)
412{
413}
414
415void __ref enable_nonboot_cpus(void)
416{
417 int cpu, error;
418
419 /* Allow everyone to use the CPU hotplug again */
420 cpu_maps_update_begin();
421 cpu_hotplug_disabled = 0;
422 if (cpumask_empty(frozen_cpus))
423 goto out;
424
425 printk("Enabling non-boot CPUs ...\n");
426
427 arch_enable_nonboot_cpus_begin();
428
429 for_each_cpu(cpu, frozen_cpus) {
430 error = _cpu_up(cpu, 1);
431 if (!error) {
432 printk("CPU%d is up\n", cpu);
433 continue;
434 }
435 printk(KERN_WARNING "Error taking CPU%d up: %d\n", cpu, error);
436 }
437
438 arch_enable_nonboot_cpus_end();
439
440 cpumask_clear(frozen_cpus);
441out:
442 cpu_maps_update_done();
443}
444
445static int alloc_frozen_cpus(void)
446{
447 if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
448 return -ENOMEM;
449 return 0;
450}
451core_initcall(alloc_frozen_cpus);
452#endif /* CONFIG_PM_SLEEP_SMP */
453
454/**
455 * notify_cpu_starting(cpu) - call the CPU_STARTING notifiers
456 * @cpu: cpu that just started
457 *
458 * This function calls the cpu_chain notifiers with CPU_STARTING.
459 * It must be called by the arch code on the new cpu, before the new cpu
460 * enables interrupts and before the "boot" cpu returns from __cpu_up().
461 */
462void __cpuinit notify_cpu_starting(unsigned int cpu)
463{
464 unsigned long val = CPU_STARTING;
465
466#ifdef CONFIG_PM_SLEEP_SMP
467 if (frozen_cpus != NULL && cpumask_test_cpu(cpu, frozen_cpus))
468 val = CPU_STARTING_FROZEN;
469#endif /* CONFIG_PM_SLEEP_SMP */
470 raw_notifier_call_chain(&cpu_chain, val, (void *)(long)cpu);
471}
472
473#endif /* CONFIG_SMP */
474
475/*
476 * cpu_bit_bitmap[] is a special, "compressed" data structure that
477 * represents all NR_CPUS bits binary values of 1<<nr.
478 *
479 * It is used by cpumask_of() to get a constant address to a CPU
480 * mask value that has a single bit set only.
481 */
482
483/* cpu_bit_bitmap[0] is empty - so we can back into it */
484#define MASK_DECLARE_1(x) [x+1][0] = 1UL << (x)
485#define MASK_DECLARE_2(x) MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
486#define MASK_DECLARE_4(x) MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
487#define MASK_DECLARE_8(x) MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
488
489const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
490
491 MASK_DECLARE_8(0), MASK_DECLARE_8(8),
492 MASK_DECLARE_8(16), MASK_DECLARE_8(24),
493#if BITS_PER_LONG > 32
494 MASK_DECLARE_8(32), MASK_DECLARE_8(40),
495 MASK_DECLARE_8(48), MASK_DECLARE_8(56),
496#endif
497};
498EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
499
500const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
501EXPORT_SYMBOL(cpu_all_bits);
502
503#ifdef CONFIG_INIT_ALL_POSSIBLE
504static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly
505 = CPU_BITS_ALL;
506#else
507static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly;
508#endif
509const struct cpumask *const cpu_possible_mask = to_cpumask(cpu_possible_bits);
510EXPORT_SYMBOL(cpu_possible_mask);
511
512static DECLARE_BITMAP(cpu_online_bits, CONFIG_NR_CPUS) __read_mostly;
513const struct cpumask *const cpu_online_mask = to_cpumask(cpu_online_bits);
514EXPORT_SYMBOL(cpu_online_mask);
515
516static DECLARE_BITMAP(cpu_present_bits, CONFIG_NR_CPUS) __read_mostly;
517const struct cpumask *const cpu_present_mask = to_cpumask(cpu_present_bits);
518EXPORT_SYMBOL(cpu_present_mask);
519
520static DECLARE_BITMAP(cpu_active_bits, CONFIG_NR_CPUS) __read_mostly;
521const struct cpumask *const cpu_active_mask = to_cpumask(cpu_active_bits);
522EXPORT_SYMBOL(cpu_active_mask);
523
524void set_cpu_possible(unsigned int cpu, bool possible)
525{
526 if (possible)
527 cpumask_set_cpu(cpu, to_cpumask(cpu_possible_bits));
528 else
529 cpumask_clear_cpu(cpu, to_cpumask(cpu_possible_bits));
530}
531
532void set_cpu_present(unsigned int cpu, bool present)
533{
534 if (present)
535 cpumask_set_cpu(cpu, to_cpumask(cpu_present_bits));
536 else
537 cpumask_clear_cpu(cpu, to_cpumask(cpu_present_bits));
538}
539
540void set_cpu_online(unsigned int cpu, bool online)
541{
542 if (online)
543 cpumask_set_cpu(cpu, to_cpumask(cpu_online_bits));
544 else
545 cpumask_clear_cpu(cpu, to_cpumask(cpu_online_bits));
546}
547
548void set_cpu_active(unsigned int cpu, bool active)
549{
550 if (active)
551 cpumask_set_cpu(cpu, to_cpumask(cpu_active_bits));
552 else
553 cpumask_clear_cpu(cpu, to_cpumask(cpu_active_bits));
554}
555
556void init_cpu_present(const struct cpumask *src)
557{
558 cpumask_copy(to_cpumask(cpu_present_bits), src);
559}
560
561void init_cpu_possible(const struct cpumask *src)
562{
563 cpumask_copy(to_cpumask(cpu_possible_bits), src);
564}
565
566void init_cpu_online(const struct cpumask *src)
567{
568 cpumask_copy(to_cpumask(cpu_online_bits), src);
569}