projects/linux·blob v2.6.28-rc2 · refs

501 lines · 12.0 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/*
19 * Represents all cpu's present in the system
20 * In systems capable of hotplug, this map could dynamically grow
21 * as new cpu's are detected in the system via any platform specific
22 * method, such as ACPI for e.g.
23 */
24cpumask_t cpu_present_map __read_mostly;
25EXPORT_SYMBOL(cpu_present_map);
26
27#ifndef CONFIG_SMP
28
29/*
30 * Represents all cpu's that are currently online.
31 */
32cpumask_t cpu_online_map __read_mostly = CPU_MASK_ALL;
33EXPORT_SYMBOL(cpu_online_map);
34
35cpumask_t cpu_possible_map __read_mostly = CPU_MASK_ALL;
36EXPORT_SYMBOL(cpu_possible_map);
37
38#else /* CONFIG_SMP */
39
40/* Serializes the updates to cpu_online_map, cpu_present_map */
41static DEFINE_MUTEX(cpu_add_remove_lock);
42
43static __cpuinitdata 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
50static struct {
51 struct task_struct *active_writer;
52 struct mutex lock; /* Synchronizes accesses to refcount, */
53 /*
54 * Also blocks the new readers during
55 * an ongoing cpu hotplug operation.
56 */
57 int refcount;
58} cpu_hotplug;
59
60void __init cpu_hotplug_init(void)
61{
62 cpu_hotplug.active_writer = NULL;
63 mutex_init(&cpu_hotplug.lock);
64 cpu_hotplug.refcount = 0;
65}
66
67cpumask_t cpu_active_map;
68
69#ifdef CONFIG_HOTPLUG_CPU
70
71void get_online_cpus(void)
72{
73 might_sleep();
74 if (cpu_hotplug.active_writer == current)
75 return;
76 mutex_lock(&cpu_hotplug.lock);
77 cpu_hotplug.refcount++;
78 mutex_unlock(&cpu_hotplug.lock);
79
80}
81EXPORT_SYMBOL_GPL(get_online_cpus);
82
83void put_online_cpus(void)
84{
85 if (cpu_hotplug.active_writer == current)
86 return;
87 mutex_lock(&cpu_hotplug.lock);
88 if (!--cpu_hotplug.refcount && unlikely(cpu_hotplug.active_writer))
89 wake_up_process(cpu_hotplug.active_writer);
90 mutex_unlock(&cpu_hotplug.lock);
91
92}
93EXPORT_SYMBOL_GPL(put_online_cpus);
94
95#endif /* CONFIG_HOTPLUG_CPU */
96
97/*
98 * The following two API's must be used when attempting
99 * to serialize the updates to cpu_online_map, cpu_present_map.
100 */
101void cpu_maps_update_begin(void)
102{
103 mutex_lock(&cpu_add_remove_lock);
104}
105
106void cpu_maps_update_done(void)
107{
108 mutex_unlock(&cpu_add_remove_lock);
109}
110
111/*
112 * This ensures that the hotplug operation can begin only when the
113 * refcount goes to zero.
114 *
115 * Note that during a cpu-hotplug operation, the new readers, if any,
116 * will be blocked by the cpu_hotplug.lock
117 *
118 * Since cpu_hotplug_begin() is always called after invoking
119 * cpu_maps_update_begin(), we can be sure that only one writer is active.
120 *
121 * Note that theoretically, there is a possibility of a livelock:
122 * - Refcount goes to zero, last reader wakes up the sleeping
123 * writer.
124 * - Last reader unlocks the cpu_hotplug.lock.
125 * - A new reader arrives at this moment, bumps up the refcount.
126 * - The writer acquires the cpu_hotplug.lock finds the refcount
127 * non zero and goes to sleep again.
128 *
129 * However, this is very difficult to achieve in practice since
130 * get_online_cpus() not an api which is called all that often.
131 *
132 */
133static void cpu_hotplug_begin(void)
134{
135 cpu_hotplug.active_writer = current;
136
137 for (;;) {
138 mutex_lock(&cpu_hotplug.lock);
139 if (likely(!cpu_hotplug.refcount))
140 break;
141 __set_current_state(TASK_UNINTERRUPTIBLE);
142 mutex_unlock(&cpu_hotplug.lock);
143 schedule();
144 }
145}
146
147static void cpu_hotplug_done(void)
148{
149 cpu_hotplug.active_writer = NULL;
150 mutex_unlock(&cpu_hotplug.lock);
151}
152/* Need to know about CPUs going up/down? */
153int __ref register_cpu_notifier(struct notifier_block *nb)
154{
155 int ret;
156 cpu_maps_update_begin();
157 ret = raw_notifier_chain_register(&cpu_chain, nb);
158 cpu_maps_update_done();
159 return ret;
160}
161
162#ifdef CONFIG_HOTPLUG_CPU
163
164EXPORT_SYMBOL(register_cpu_notifier);
165
166void __ref unregister_cpu_notifier(struct notifier_block *nb)
167{
168 cpu_maps_update_begin();
169 raw_notifier_chain_unregister(&cpu_chain, nb);
170 cpu_maps_update_done();
171}
172EXPORT_SYMBOL(unregister_cpu_notifier);
173
174static inline void check_for_tasks(int cpu)
175{
176 struct task_struct *p;
177
178 write_lock_irq(&tasklist_lock);
179 for_each_process(p) {
180 if (task_cpu(p) == cpu &&
181 (!cputime_eq(p->utime, cputime_zero) ||
182 !cputime_eq(p->stime, cputime_zero)))
183 printk(KERN_WARNING "Task %s (pid = %d) is on cpu %d\
184 (state = %ld, flags = %x) \n",
185 p->comm, task_pid_nr(p), cpu,
186 p->state, p->flags);
187 }
188 write_unlock_irq(&tasklist_lock);
189}
190
191struct take_cpu_down_param {
192 unsigned long mod;
193 void *hcpu;
194};
195
196/* Take this CPU down. */
197static int __ref take_cpu_down(void *_param)
198{
199 struct take_cpu_down_param *param = _param;
200 int err;
201
202 /* Ensure this CPU doesn't handle any more interrupts. */
203 err = __cpu_disable();
204 if (err < 0)
205 return err;
206
207 raw_notifier_call_chain(&cpu_chain, CPU_DYING | param->mod,
208 param->hcpu);
209
210 /* Force idle task to run as soon as we yield: it should
211 immediately notice cpu is offline and die quickly. */
212 sched_idle_next();
213 return 0;
214}
215
216/* Requires cpu_add_remove_lock to be held */
217static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
218{
219 int err, nr_calls = 0;
220 cpumask_t old_allowed, tmp;
221 void *hcpu = (void *)(long)cpu;
222 unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
223 struct take_cpu_down_param tcd_param = {
224 .mod = mod,
225 .hcpu = hcpu,
226 };
227
228 if (num_online_cpus() == 1)
229 return -EBUSY;
230
231 if (!cpu_online(cpu))
232 return -EINVAL;
233
234 cpu_hotplug_begin();
235 err = __raw_notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE | mod,
236 hcpu, -1, &nr_calls);
237 if (err == NOTIFY_BAD) {
238 nr_calls--;
239 __raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED | mod,
240 hcpu, nr_calls, NULL);
241 printk("%s: attempt to take down CPU %u failed\n",
242 __func__, cpu);
243 err = -EINVAL;
244 goto out_release;
245 }
246
247 /* Ensure that we are not runnable on dying cpu */
248 old_allowed = current->cpus_allowed;
249 cpus_setall(tmp);
250 cpu_clear(cpu, tmp);
251 set_cpus_allowed_ptr(current, &tmp);
252 tmp = cpumask_of_cpu(cpu);
253
254 err = __stop_machine(take_cpu_down, &tcd_param, &tmp);
255 if (err) {
256 /* CPU didn't die: tell everyone. Can't complain. */
257 if (raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED | mod,
258 hcpu) == NOTIFY_BAD)
259 BUG();
260
261 goto out_allowed;
262 }
263 BUG_ON(cpu_online(cpu));
264
265 /* Wait for it to sleep (leaving idle task). */
266 while (!idle_cpu(cpu))
267 yield();
268
269 /* This actually kills the CPU. */
270 __cpu_die(cpu);
271
272 /* CPU is completely dead: tell everyone. Too late to complain. */
273 if (raw_notifier_call_chain(&cpu_chain, CPU_DEAD | mod,
274 hcpu) == NOTIFY_BAD)
275 BUG();
276
277 check_for_tasks(cpu);
278
279out_allowed:
280 set_cpus_allowed_ptr(current, &old_allowed);
281out_release:
282 cpu_hotplug_done();
283 if (!err) {
284 if (raw_notifier_call_chain(&cpu_chain, CPU_POST_DEAD | mod,
285 hcpu) == NOTIFY_BAD)
286 BUG();
287 }
288 return err;
289}
290
291int __ref cpu_down(unsigned int cpu)
292{
293 int err = 0;
294
295 cpu_maps_update_begin();
296
297 if (cpu_hotplug_disabled) {
298 err = -EBUSY;
299 goto out;
300 }
301
302 cpu_clear(cpu, cpu_active_map);
303
304 /*
305 * Make sure the all cpus did the reschedule and are not
306 * using stale version of the cpu_active_map.
307 * This is not strictly necessary becuase stop_machine()
308 * that we run down the line already provides the required
309 * synchronization. But it's really a side effect and we do not
310 * want to depend on the innards of the stop_machine here.
311 */
312 synchronize_sched();
313
314 err = _cpu_down(cpu, 0);
315
316 if (cpu_online(cpu))
317 cpu_set(cpu, cpu_active_map);
318
319out:
320 cpu_maps_update_done();
321 return err;
322}
323EXPORT_SYMBOL(cpu_down);
324#endif /*CONFIG_HOTPLUG_CPU*/
325
326/* Requires cpu_add_remove_lock to be held */
327static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen)
328{
329 int ret, nr_calls = 0;
330 void *hcpu = (void *)(long)cpu;
331 unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
332
333 if (cpu_online(cpu) || !cpu_present(cpu))
334 return -EINVAL;
335
336 cpu_hotplug_begin();
337 ret = __raw_notifier_call_chain(&cpu_chain, CPU_UP_PREPARE | mod, hcpu,
338 -1, &nr_calls);
339 if (ret == NOTIFY_BAD) {
340 nr_calls--;
341 printk("%s: attempt to bring up CPU %u failed\n",
342 __func__, cpu);
343 ret = -EINVAL;
344 goto out_notify;
345 }
346
347 /* Arch-specific enabling code. */
348 ret = __cpu_up(cpu);
349 if (ret != 0)
350 goto out_notify;
351 BUG_ON(!cpu_online(cpu));
352
353 cpu_set(cpu, cpu_active_map);
354
355 /* Now call notifier in preparation. */
356 raw_notifier_call_chain(&cpu_chain, CPU_ONLINE | mod, hcpu);
357
358out_notify:
359 if (ret != 0)
360 __raw_notifier_call_chain(&cpu_chain,
361 CPU_UP_CANCELED | mod, hcpu, nr_calls, NULL);
362 cpu_hotplug_done();
363
364 return ret;
365}
366
367int __cpuinit cpu_up(unsigned int cpu)
368{
369 int err = 0;
370 if (!cpu_isset(cpu, cpu_possible_map)) {
371 printk(KERN_ERR "can't online cpu %d because it is not "
372 "configured as may-hotadd at boot time\n", cpu);
373#if defined(CONFIG_IA64) || defined(CONFIG_X86_64)
374 printk(KERN_ERR "please check additional_cpus= boot "
375 "parameter\n");
376#endif
377 return -EINVAL;
378 }
379
380 cpu_maps_update_begin();
381
382 if (cpu_hotplug_disabled) {
383 err = -EBUSY;
384 goto out;
385 }
386
387 err = _cpu_up(cpu, 0);
388
389out:
390 cpu_maps_update_done();
391 return err;
392}
393
394#ifdef CONFIG_PM_SLEEP_SMP
395static cpumask_t frozen_cpus;
396
397int disable_nonboot_cpus(void)
398{
399 int cpu, first_cpu, error = 0;
400
401 cpu_maps_update_begin();
402 first_cpu = first_cpu(cpu_online_map);
403 /* We take down all of the non-boot CPUs in one shot to avoid races
404 * with the userspace trying to use the CPU hotplug at the same time
405 */
406 cpus_clear(frozen_cpus);
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 cpu_set(cpu, frozen_cpus);
414 printk("CPU%d is down\n", cpu);
415 } else {
416 printk(KERN_ERR "Error taking CPU%d down: %d\n",
417 cpu, error);
418 break;
419 }
420 }
421 if (!error) {
422 BUG_ON(num_online_cpus() > 1);
423 /* Make sure the CPUs won't be enabled by someone else */
424 cpu_hotplug_disabled = 1;
425 } else {
426 printk(KERN_ERR "Non-boot CPUs are not disabled\n");
427 }
428 cpu_maps_update_done();
429 return error;
430}
431
432void __ref enable_nonboot_cpus(void)
433{
434 int cpu, error;
435
436 /* Allow everyone to use the CPU hotplug again */
437 cpu_maps_update_begin();
438 cpu_hotplug_disabled = 0;
439 if (cpus_empty(frozen_cpus))
440 goto out;
441
442 printk("Enabling non-boot CPUs ...\n");
443 for_each_cpu_mask_nr(cpu, frozen_cpus) {
444 error = _cpu_up(cpu, 1);
445 if (!error) {
446 printk("CPU%d is up\n", cpu);
447 continue;
448 }
449 printk(KERN_WARNING "Error taking CPU%d up: %d\n", cpu, error);
450 }
451 cpus_clear(frozen_cpus);
452out:
453 cpu_maps_update_done();
454}
455#endif /* CONFIG_PM_SLEEP_SMP */
456
457/**
458 * notify_cpu_starting(cpu) - call the CPU_STARTING notifiers
459 * @cpu: cpu that just started
460 *
461 * This function calls the cpu_chain notifiers with CPU_STARTING.
462 * It must be called by the arch code on the new cpu, before the new cpu
463 * enables interrupts and before the "boot" cpu returns from __cpu_up().
464 */
465void notify_cpu_starting(unsigned int cpu)
466{
467 unsigned long val = CPU_STARTING;
468
469#ifdef CONFIG_PM_SLEEP_SMP
470 if (cpu_isset(cpu, frozen_cpus))
471 val = CPU_STARTING_FROZEN;
472#endif /* CONFIG_PM_SLEEP_SMP */
473 raw_notifier_call_chain(&cpu_chain, val, (void *)(long)cpu);
474}
475
476#endif /* CONFIG_SMP */
477
478/*
479 * cpu_bit_bitmap[] is a special, "compressed" data structure that
480 * represents all NR_CPUS bits binary values of 1<<nr.
481 *
482 * It is used by cpumask_of_cpu() to get a constant address to a CPU
483 * mask value that has a single bit set only.
484 */
485
486/* cpu_bit_bitmap[0] is empty - so we can back into it */
487#define MASK_DECLARE_1(x) [x+1][0] = 1UL << (x)
488#define MASK_DECLARE_2(x) MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
489#define MASK_DECLARE_4(x) MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
490#define MASK_DECLARE_8(x) MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
491
492const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
493
494 MASK_DECLARE_8(0), MASK_DECLARE_8(8),
495 MASK_DECLARE_8(16), MASK_DECLARE_8(24),
496#if BITS_PER_LONG > 32
497 MASK_DECLARE_8(32), MASK_DECLARE_8(40),
498 MASK_DECLARE_8(48), MASK_DECLARE_8(56),
499#endif
500};
501EXPORT_SYMBOL_GPL(cpu_bit_bitmap);