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Merge branch 'linux-next' of git://git.infradead.org/ubifs-2.6
[linux-2.6-omap-h63xx.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
39 void __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
48 void 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 }
58 EXPORT_SYMBOL_GPL(get_online_cpus);
59
60 void 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 }
70 EXPORT_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  */
78 void cpu_maps_update_begin(void)
79 {
80         mutex_lock(&cpu_add_remove_lock);
81 }
82
83 void 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  */
110 static 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
124 static 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? */
130 int __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
141 EXPORT_SYMBOL(register_cpu_notifier);
142
143 void __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 }
149 EXPORT_SYMBOL(unregister_cpu_notifier);
150
151 static 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
168 struct take_cpu_down_param {
169         unsigned long mod;
170         void *hcpu;
171 };
172
173 /* Take this CPU down. */
174 static 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 */
194 static 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
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         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
301 out:
302         cpu_maps_update_done();
303         stop_machine_destroy();
304         return err;
305 }
306 EXPORT_SYMBOL(cpu_down);
307 #endif /*CONFIG_HOTPLUG_CPU*/
308
309 /* Requires cpu_add_remove_lock to be held */
310 static 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
341 out_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
350 int __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
372 out:
373         cpu_maps_update_done();
374         return err;
375 }
376
377 #ifdef CONFIG_PM_SLEEP_SMP
378 static cpumask_var_t frozen_cpus;
379
380 int 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
419 void __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);
439 out:
440         cpu_maps_update_done();
441 }
442
443 static int alloc_frozen_cpus(void)
444 {
445         if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
446                 return -ENOMEM;
447         return 0;
448 }
449 core_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  */
460 void __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
487 const 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 };
496 EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
497
498 const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
499 EXPORT_SYMBOL(cpu_all_bits);
500
501 #ifdef CONFIG_INIT_ALL_POSSIBLE
502 static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly
503         = CPU_BITS_ALL;
504 #else
505 static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly;
506 #endif
507 const struct cpumask *const cpu_possible_mask = to_cpumask(cpu_possible_bits);
508 EXPORT_SYMBOL(cpu_possible_mask);
509
510 static DECLARE_BITMAP(cpu_online_bits, CONFIG_NR_CPUS) __read_mostly;
511 const struct cpumask *const cpu_online_mask = to_cpumask(cpu_online_bits);
512 EXPORT_SYMBOL(cpu_online_mask);
513
514 static DECLARE_BITMAP(cpu_present_bits, CONFIG_NR_CPUS) __read_mostly;
515 const struct cpumask *const cpu_present_mask = to_cpumask(cpu_present_bits);
516 EXPORT_SYMBOL(cpu_present_mask);
517
518 static DECLARE_BITMAP(cpu_active_bits, CONFIG_NR_CPUS) __read_mostly;
519 const struct cpumask *const cpu_active_mask = to_cpumask(cpu_active_bits);
520 EXPORT_SYMBOL(cpu_active_mask);
521
522 void 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
530 void 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
538 void 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
546 void 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
554 void init_cpu_present(const struct cpumask *src)
555 {
556         cpumask_copy(to_cpumask(cpu_present_bits), src);
557 }
558
559 void init_cpu_possible(const struct cpumask *src)
560 {
561         cpumask_copy(to_cpumask(cpu_possible_bits), src);
562 }
563
564 void init_cpu_online(const struct cpumask *src)
565 {
566         cpumask_copy(to_cpumask(cpu_online_bits), src);
567 }