Merge git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6
[linux-2.6.git] / kernel / cpu.c
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 */
20 static DEFINE_MUTEX(cpu_add_remove_lock);
21
22 static __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  */
27 static int cpu_hotplug_disabled;
28
29 static 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         .active_writer = NULL,
39         .lock = __MUTEX_INITIALIZER(cpu_hotplug.lock),
40         .refcount = 0,
41 };
42
43 #ifdef CONFIG_HOTPLUG_CPU
44
45 void get_online_cpus(void)
46 {
47         might_sleep();
48         if (cpu_hotplug.active_writer == current)
49                 return;
50         mutex_lock(&cpu_hotplug.lock);
51         cpu_hotplug.refcount++;
52         mutex_unlock(&cpu_hotplug.lock);
53
54 }
55 EXPORT_SYMBOL_GPL(get_online_cpus);
56
57 void put_online_cpus(void)
58 {
59         if (cpu_hotplug.active_writer == current)
60                 return;
61         mutex_lock(&cpu_hotplug.lock);
62         if (!--cpu_hotplug.refcount && unlikely(cpu_hotplug.active_writer))
63                 wake_up_process(cpu_hotplug.active_writer);
64         mutex_unlock(&cpu_hotplug.lock);
65
66 }
67 EXPORT_SYMBOL_GPL(put_online_cpus);
68
69 #endif  /* CONFIG_HOTPLUG_CPU */
70
71 /*
72  * The following two API's must be used when attempting
73  * to serialize the updates to cpu_online_mask, cpu_present_mask.
74  */
75 void cpu_maps_update_begin(void)
76 {
77         mutex_lock(&cpu_add_remove_lock);
78 }
79
80 void cpu_maps_update_done(void)
81 {
82         mutex_unlock(&cpu_add_remove_lock);
83 }
84
85 /*
86  * This ensures that the hotplug operation can begin only when the
87  * refcount goes to zero.
88  *
89  * Note that during a cpu-hotplug operation, the new readers, if any,
90  * will be blocked by the cpu_hotplug.lock
91  *
92  * Since cpu_hotplug_begin() is always called after invoking
93  * cpu_maps_update_begin(), we can be sure that only one writer is active.
94  *
95  * Note that theoretically, there is a possibility of a livelock:
96  * - Refcount goes to zero, last reader wakes up the sleeping
97  *   writer.
98  * - Last reader unlocks the cpu_hotplug.lock.
99  * - A new reader arrives at this moment, bumps up the refcount.
100  * - The writer acquires the cpu_hotplug.lock finds the refcount
101  *   non zero and goes to sleep again.
102  *
103  * However, this is very difficult to achieve in practice since
104  * get_online_cpus() not an api which is called all that often.
105  *
106  */
107 static void cpu_hotplug_begin(void)
108 {
109         cpu_hotplug.active_writer = current;
110
111         for (;;) {
112                 mutex_lock(&cpu_hotplug.lock);
113                 if (likely(!cpu_hotplug.refcount))
114                         break;
115                 __set_current_state(TASK_UNINTERRUPTIBLE);
116                 mutex_unlock(&cpu_hotplug.lock);
117                 schedule();
118         }
119 }
120
121 static void cpu_hotplug_done(void)
122 {
123         cpu_hotplug.active_writer = NULL;
124         mutex_unlock(&cpu_hotplug.lock);
125 }
126 /* Need to know about CPUs going up/down? */
127 int __ref register_cpu_notifier(struct notifier_block *nb)
128 {
129         int ret;
130         cpu_maps_update_begin();
131         ret = raw_notifier_chain_register(&cpu_chain, nb);
132         cpu_maps_update_done();
133         return ret;
134 }
135
136 #ifdef CONFIG_HOTPLUG_CPU
137
138 EXPORT_SYMBOL(register_cpu_notifier);
139
140 void __ref unregister_cpu_notifier(struct notifier_block *nb)
141 {
142         cpu_maps_update_begin();
143         raw_notifier_chain_unregister(&cpu_chain, nb);
144         cpu_maps_update_done();
145 }
146 EXPORT_SYMBOL(unregister_cpu_notifier);
147
148 static inline void check_for_tasks(int cpu)
149 {
150         struct task_struct *p;
151
152         write_lock_irq(&tasklist_lock);
153         for_each_process(p) {
154                 if (task_cpu(p) == cpu && p->state == TASK_RUNNING &&
155                     (!cputime_eq(p->utime, cputime_zero) ||
156                      !cputime_eq(p->stime, cputime_zero)))
157                         printk(KERN_WARNING "Task %s (pid = %d) is on cpu %d "
158                                 "(state = %ld, flags = %x)\n",
159                                 p->comm, task_pid_nr(p), cpu,
160                                 p->state, p->flags);
161         }
162         write_unlock_irq(&tasklist_lock);
163 }
164
165 struct take_cpu_down_param {
166         unsigned long mod;
167         void *hcpu;
168 };
169
170 /* Take this CPU down. */
171 static int __ref take_cpu_down(void *_param)
172 {
173         struct take_cpu_down_param *param = _param;
174         int err;
175
176         /* Ensure this CPU doesn't handle any more interrupts. */
177         err = __cpu_disable();
178         if (err < 0)
179                 return err;
180
181         raw_notifier_call_chain(&cpu_chain, CPU_DYING | param->mod,
182                                 param->hcpu);
183
184         /* Force idle task to run as soon as we yield: it should
185            immediately notice cpu is offline and die quickly. */
186         sched_idle_next();
187         return 0;
188 }
189
190 /* Requires cpu_add_remove_lock to be held */
191 static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
192 {
193         int err, nr_calls = 0;
194         cpumask_var_t old_allowed;
195         void *hcpu = (void *)(long)cpu;
196         unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
197         struct take_cpu_down_param tcd_param = {
198                 .mod = mod,
199                 .hcpu = hcpu,
200         };
201
202         if (num_online_cpus() == 1)
203                 return -EBUSY;
204
205         if (!cpu_online(cpu))
206                 return -EINVAL;
207
208         if (!alloc_cpumask_var(&old_allowed, GFP_KERNEL))
209                 return -ENOMEM;
210
211         cpu_hotplug_begin();
212         set_cpu_active(cpu, false);
213         err = __raw_notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE | mod,
214                                         hcpu, -1, &nr_calls);
215         if (err == NOTIFY_BAD) {
216                 set_cpu_active(cpu, true);
217
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, cpu_active_mask);
230
231         err = __stop_machine(take_cpu_down, &tcd_param, cpumask_of(cpu));
232         if (err) {
233                 set_cpu_active(cpu, true);
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
257 out_allowed:
258         set_cpus_allowed_ptr(current, old_allowed);
259 out_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
270 int __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         err = _cpu_down(cpu, 0);
285
286 out:
287         cpu_maps_update_done();
288         stop_machine_destroy();
289         return err;
290 }
291 EXPORT_SYMBOL(cpu_down);
292 #endif /*CONFIG_HOTPLUG_CPU*/
293
294 /* Requires cpu_add_remove_lock to be held */
295 static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen)
296 {
297         int ret, nr_calls = 0;
298         void *hcpu = (void *)(long)cpu;
299         unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
300
301         if (cpu_online(cpu) || !cpu_present(cpu))
302                 return -EINVAL;
303
304         cpu_hotplug_begin();
305         ret = __raw_notifier_call_chain(&cpu_chain, CPU_UP_PREPARE | mod, hcpu,
306                                                         -1, &nr_calls);
307         if (ret == NOTIFY_BAD) {
308                 nr_calls--;
309                 printk("%s: attempt to bring up CPU %u failed\n",
310                                 __func__, cpu);
311                 ret = -EINVAL;
312                 goto out_notify;
313         }
314
315         /* Arch-specific enabling code. */
316         ret = __cpu_up(cpu);
317         if (ret != 0)
318                 goto out_notify;
319         BUG_ON(!cpu_online(cpu));
320
321         set_cpu_active(cpu, true);
322
323         /* Now call notifier in preparation. */
324         raw_notifier_call_chain(&cpu_chain, CPU_ONLINE | mod, hcpu);
325
326 out_notify:
327         if (ret != 0)
328                 __raw_notifier_call_chain(&cpu_chain,
329                                 CPU_UP_CANCELED | mod, hcpu, nr_calls, NULL);
330         cpu_hotplug_done();
331
332         return ret;
333 }
334
335 int __cpuinit cpu_up(unsigned int cpu)
336 {
337         int err = 0;
338         if (!cpu_possible(cpu)) {
339                 printk(KERN_ERR "can't online cpu %d because it is not "
340                         "configured as may-hotadd at boot time\n", cpu);
341 #if defined(CONFIG_IA64) || defined(CONFIG_X86_64)
342                 printk(KERN_ERR "please check additional_cpus= boot "
343                                 "parameter\n");
344 #endif
345                 return -EINVAL;
346         }
347
348         cpu_maps_update_begin();
349
350         if (cpu_hotplug_disabled) {
351                 err = -EBUSY;
352                 goto out;
353         }
354
355         err = _cpu_up(cpu, 0);
356
357 out:
358         cpu_maps_update_done();
359         return err;
360 }
361
362 #ifdef CONFIG_PM_SLEEP_SMP
363 static cpumask_var_t frozen_cpus;
364
365 int disable_nonboot_cpus(void)
366 {
367         int cpu, first_cpu, error;
368
369         error = stop_machine_create();
370         if (error)
371                 return error;
372         cpu_maps_update_begin();
373         first_cpu = cpumask_first(cpu_online_mask);
374         /*
375          * We take down all of the non-boot CPUs in one shot to avoid races
376          * with the userspace trying to use the CPU hotplug at the same time
377          */
378         cpumask_clear(frozen_cpus);
379
380         printk("Disabling non-boot CPUs ...\n");
381         for_each_online_cpu(cpu) {
382                 if (cpu == first_cpu)
383                         continue;
384                 error = _cpu_down(cpu, 1);
385                 if (!error)
386                         cpumask_set_cpu(cpu, frozen_cpus);
387                 else {
388                         printk(KERN_ERR "Error taking CPU%d down: %d\n",
389                                 cpu, error);
390                         break;
391                 }
392         }
393
394         if (!error) {
395                 BUG_ON(num_online_cpus() > 1);
396                 /* Make sure the CPUs won't be enabled by someone else */
397                 cpu_hotplug_disabled = 1;
398         } else {
399                 printk(KERN_ERR "Non-boot CPUs are not disabled\n");
400         }
401         cpu_maps_update_done();
402         stop_machine_destroy();
403         return error;
404 }
405
406 void __weak arch_enable_nonboot_cpus_begin(void)
407 {
408 }
409
410 void __weak arch_enable_nonboot_cpus_end(void)
411 {
412 }
413
414 void __ref enable_nonboot_cpus(void)
415 {
416         int cpu, error;
417
418         /* Allow everyone to use the CPU hotplug again */
419         cpu_maps_update_begin();
420         cpu_hotplug_disabled = 0;
421         if (cpumask_empty(frozen_cpus))
422                 goto out;
423
424         printk("Enabling non-boot CPUs ...\n");
425
426         arch_enable_nonboot_cpus_begin();
427
428         for_each_cpu(cpu, frozen_cpus) {
429                 error = _cpu_up(cpu, 1);
430                 if (!error) {
431                         printk("CPU%d is up\n", cpu);
432                         continue;
433                 }
434                 printk(KERN_WARNING "Error taking CPU%d up: %d\n", cpu, error);
435         }
436
437         arch_enable_nonboot_cpus_end();
438
439         cpumask_clear(frozen_cpus);
440 out:
441         cpu_maps_update_done();
442 }
443
444 static int alloc_frozen_cpus(void)
445 {
446         if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
447                 return -ENOMEM;
448         return 0;
449 }
450 core_initcall(alloc_frozen_cpus);
451 #endif /* CONFIG_PM_SLEEP_SMP */
452
453 /**
454  * notify_cpu_starting(cpu) - call the CPU_STARTING notifiers
455  * @cpu: cpu that just started
456  *
457  * This function calls the cpu_chain notifiers with CPU_STARTING.
458  * It must be called by the arch code on the new cpu, before the new cpu
459  * enables interrupts and before the "boot" cpu returns from __cpu_up().
460  */
461 void __cpuinit notify_cpu_starting(unsigned int cpu)
462 {
463         unsigned long val = CPU_STARTING;
464
465 #ifdef CONFIG_PM_SLEEP_SMP
466         if (frozen_cpus != NULL && cpumask_test_cpu(cpu, frozen_cpus))
467                 val = CPU_STARTING_FROZEN;
468 #endif /* CONFIG_PM_SLEEP_SMP */
469         raw_notifier_call_chain(&cpu_chain, val, (void *)(long)cpu);
470 }
471
472 #endif /* CONFIG_SMP */
473
474 /*
475  * cpu_bit_bitmap[] is a special, "compressed" data structure that
476  * represents all NR_CPUS bits binary values of 1<<nr.
477  *
478  * It is used by cpumask_of() to get a constant address to a CPU
479  * mask value that has a single bit set only.
480  */
481
482 /* cpu_bit_bitmap[0] is empty - so we can back into it */
483 #define MASK_DECLARE_1(x)       [x+1][0] = 1UL << (x)
484 #define MASK_DECLARE_2(x)       MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
485 #define MASK_DECLARE_4(x)       MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
486 #define MASK_DECLARE_8(x)       MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
487
488 const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
489
490         MASK_DECLARE_8(0),      MASK_DECLARE_8(8),
491         MASK_DECLARE_8(16),     MASK_DECLARE_8(24),
492 #if BITS_PER_LONG > 32
493         MASK_DECLARE_8(32),     MASK_DECLARE_8(40),
494         MASK_DECLARE_8(48),     MASK_DECLARE_8(56),
495 #endif
496 };
497 EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
498
499 const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
500 EXPORT_SYMBOL(cpu_all_bits);
501
502 #ifdef CONFIG_INIT_ALL_POSSIBLE
503 static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly
504         = CPU_BITS_ALL;
505 #else
506 static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly;
507 #endif
508 const struct cpumask *const cpu_possible_mask = to_cpumask(cpu_possible_bits);
509 EXPORT_SYMBOL(cpu_possible_mask);
510
511 static DECLARE_BITMAP(cpu_online_bits, CONFIG_NR_CPUS) __read_mostly;
512 const struct cpumask *const cpu_online_mask = to_cpumask(cpu_online_bits);
513 EXPORT_SYMBOL(cpu_online_mask);
514
515 static DECLARE_BITMAP(cpu_present_bits, CONFIG_NR_CPUS) __read_mostly;
516 const struct cpumask *const cpu_present_mask = to_cpumask(cpu_present_bits);
517 EXPORT_SYMBOL(cpu_present_mask);
518
519 static DECLARE_BITMAP(cpu_active_bits, CONFIG_NR_CPUS) __read_mostly;
520 const struct cpumask *const cpu_active_mask = to_cpumask(cpu_active_bits);
521 EXPORT_SYMBOL(cpu_active_mask);
522
523 void set_cpu_possible(unsigned int cpu, bool possible)
524 {
525         if (possible)
526                 cpumask_set_cpu(cpu, to_cpumask(cpu_possible_bits));
527         else
528                 cpumask_clear_cpu(cpu, to_cpumask(cpu_possible_bits));
529 }
530
531 void set_cpu_present(unsigned int cpu, bool present)
532 {
533         if (present)
534                 cpumask_set_cpu(cpu, to_cpumask(cpu_present_bits));
535         else
536                 cpumask_clear_cpu(cpu, to_cpumask(cpu_present_bits));
537 }
538
539 void set_cpu_online(unsigned int cpu, bool online)
540 {
541         if (online)
542                 cpumask_set_cpu(cpu, to_cpumask(cpu_online_bits));
543         else
544                 cpumask_clear_cpu(cpu, to_cpumask(cpu_online_bits));
545 }
546
547 void set_cpu_active(unsigned int cpu, bool active)
548 {
549         if (active)
550                 cpumask_set_cpu(cpu, to_cpumask(cpu_active_bits));
551         else
552                 cpumask_clear_cpu(cpu, to_cpumask(cpu_active_bits));
553 }
554
555 void init_cpu_present(const struct cpumask *src)
556 {
557         cpumask_copy(to_cpumask(cpu_present_bits), src);
558 }
559
560 void init_cpu_possible(const struct cpumask *src)
561 {
562         cpumask_copy(to_cpumask(cpu_possible_bits), src);
563 }
564
565 void init_cpu_online(const struct cpumask *src)
566 {
567         cpumask_copy(to_cpumask(cpu_online_bits), src);
568 }