Merge branch 'linus' into sched/core
[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 #include <linux/gfp.h>
18
19 #ifdef CONFIG_SMP
20 /* Serializes the updates to cpu_online_mask, cpu_present_mask */
21 static DEFINE_MUTEX(cpu_add_remove_lock);
22
23 static __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  */
28 static int cpu_hotplug_disabled;
29
30 static 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
46 void 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 }
56 EXPORT_SYMBOL_GPL(get_online_cpus);
57
58 void 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 }
68 EXPORT_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  */
76 void cpu_maps_update_begin(void)
77 {
78         mutex_lock(&cpu_add_remove_lock);
79 }
80
81 void 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  */
108 static 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
122 static 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? */
128 int __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
139 EXPORT_SYMBOL(register_cpu_notifier);
140
141 void __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 }
147 EXPORT_SYMBOL(unregister_cpu_notifier);
148
149 static 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
166 struct take_cpu_down_param {
167         struct task_struct *caller;
168         unsigned long mod;
169         void *hcpu;
170 };
171
172 /* Take this CPU down. */
173 static int __ref take_cpu_down(void *_param)
174 {
175         struct take_cpu_down_param *param = _param;
176         unsigned int cpu = (unsigned long)param->hcpu;
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         if (task_cpu(param->caller) == cpu)
188                 move_task_off_dead_cpu(cpu, param->caller);
189         /* Force idle task to run as soon as we yield: it should
190            immediately notice cpu is offline and die quickly. */
191         sched_idle_next();
192         return 0;
193 }
194
195 /* Requires cpu_add_remove_lock to be held */
196 static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
197 {
198         int err, nr_calls = 0;
199         void *hcpu = (void *)(long)cpu;
200         unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
201         struct take_cpu_down_param tcd_param = {
202                 .caller = current,
203                 .mod = mod,
204                 .hcpu = hcpu,
205         };
206
207         if (num_online_cpus() == 1)
208                 return -EBUSY;
209
210         if (!cpu_online(cpu))
211                 return -EINVAL;
212
213         cpu_hotplug_begin();
214         set_cpu_active(cpu, false);
215         err = __raw_notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE | mod,
216                                         hcpu, -1, &nr_calls);
217         if (err == NOTIFY_BAD) {
218                 set_cpu_active(cpu, true);
219
220                 nr_calls--;
221                 __raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED | mod,
222                                           hcpu, nr_calls, NULL);
223                 printk("%s: attempt to take down CPU %u failed\n",
224                                 __func__, cpu);
225                 err = -EINVAL;
226                 goto out_release;
227         }
228
229         err = __stop_machine(take_cpu_down, &tcd_param, cpumask_of(cpu));
230         if (err) {
231                 set_cpu_active(cpu, true);
232                 /* CPU didn't die: tell everyone.  Can't complain. */
233                 if (raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED | mod,
234                                             hcpu) == NOTIFY_BAD)
235                         BUG();
236
237                 goto out_release;
238         }
239         BUG_ON(cpu_online(cpu));
240
241         /* Wait for it to sleep (leaving idle task). */
242         while (!idle_cpu(cpu))
243                 yield();
244
245         /* This actually kills the CPU. */
246         __cpu_die(cpu);
247
248         /* CPU is completely dead: tell everyone.  Too late to complain. */
249         if (raw_notifier_call_chain(&cpu_chain, CPU_DEAD | mod,
250                                     hcpu) == NOTIFY_BAD)
251                 BUG();
252
253         check_for_tasks(cpu);
254
255 out_release:
256         cpu_hotplug_done();
257         if (!err) {
258                 if (raw_notifier_call_chain(&cpu_chain, CPU_POST_DEAD | mod,
259                                             hcpu) == NOTIFY_BAD)
260                         BUG();
261         }
262         return err;
263 }
264
265 int __ref cpu_down(unsigned int cpu)
266 {
267         int err;
268
269         err = stop_machine_create();
270         if (err)
271                 return err;
272         cpu_maps_update_begin();
273
274         if (cpu_hotplug_disabled) {
275                 err = -EBUSY;
276                 goto out;
277         }
278
279         err = _cpu_down(cpu, 0);
280
281 out:
282         cpu_maps_update_done();
283         stop_machine_destroy();
284         return err;
285 }
286 EXPORT_SYMBOL(cpu_down);
287 #endif /*CONFIG_HOTPLUG_CPU*/
288
289 /* Requires cpu_add_remove_lock to be held */
290 static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen)
291 {
292         int ret, nr_calls = 0;
293         void *hcpu = (void *)(long)cpu;
294         unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
295
296         if (cpu_online(cpu) || !cpu_present(cpu))
297                 return -EINVAL;
298
299         cpu_hotplug_begin();
300         ret = __raw_notifier_call_chain(&cpu_chain, CPU_UP_PREPARE | mod, hcpu,
301                                                         -1, &nr_calls);
302         if (ret == NOTIFY_BAD) {
303                 nr_calls--;
304                 printk("%s: attempt to bring up CPU %u failed\n",
305                                 __func__, cpu);
306                 ret = -EINVAL;
307                 goto out_notify;
308         }
309
310         /* Arch-specific enabling code. */
311         ret = __cpu_up(cpu);
312         if (ret != 0)
313                 goto out_notify;
314         BUG_ON(!cpu_online(cpu));
315
316         set_cpu_active(cpu, true);
317
318         /* Now call notifier in preparation. */
319         raw_notifier_call_chain(&cpu_chain, CPU_ONLINE | mod, hcpu);
320
321 out_notify:
322         if (ret != 0)
323                 __raw_notifier_call_chain(&cpu_chain,
324                                 CPU_UP_CANCELED | mod, hcpu, nr_calls, NULL);
325         cpu_hotplug_done();
326
327         return ret;
328 }
329
330 int __cpuinit cpu_up(unsigned int cpu)
331 {
332         int err = 0;
333         if (!cpu_possible(cpu)) {
334                 printk(KERN_ERR "can't online cpu %d because it is not "
335                         "configured as may-hotadd at boot time\n", cpu);
336 #if defined(CONFIG_IA64)
337                 printk(KERN_ERR "please check additional_cpus= boot "
338                                 "parameter\n");
339 #endif
340                 return -EINVAL;
341         }
342
343         cpu_maps_update_begin();
344
345         if (cpu_hotplug_disabled) {
346                 err = -EBUSY;
347                 goto out;
348         }
349
350         err = _cpu_up(cpu, 0);
351
352 out:
353         cpu_maps_update_done();
354         return err;
355 }
356
357 #ifdef CONFIG_PM_SLEEP_SMP
358 static cpumask_var_t frozen_cpus;
359
360 int disable_nonboot_cpus(void)
361 {
362         int cpu, first_cpu, error;
363
364         error = stop_machine_create();
365         if (error)
366                 return error;
367         cpu_maps_update_begin();
368         first_cpu = cpumask_first(cpu_online_mask);
369         /*
370          * We take down all of the non-boot CPUs in one shot to avoid races
371          * with the userspace trying to use the CPU hotplug at the same time
372          */
373         cpumask_clear(frozen_cpus);
374
375         printk("Disabling non-boot CPUs ...\n");
376         for_each_online_cpu(cpu) {
377                 if (cpu == first_cpu)
378                         continue;
379                 error = _cpu_down(cpu, 1);
380                 if (!error)
381                         cpumask_set_cpu(cpu, frozen_cpus);
382                 else {
383                         printk(KERN_ERR "Error taking CPU%d down: %d\n",
384                                 cpu, error);
385                         break;
386                 }
387         }
388
389         if (!error) {
390                 BUG_ON(num_online_cpus() > 1);
391                 /* Make sure the CPUs won't be enabled by someone else */
392                 cpu_hotplug_disabled = 1;
393         } else {
394                 printk(KERN_ERR "Non-boot CPUs are not disabled\n");
395         }
396         cpu_maps_update_done();
397         stop_machine_destroy();
398         return error;
399 }
400
401 void __weak arch_enable_nonboot_cpus_begin(void)
402 {
403 }
404
405 void __weak arch_enable_nonboot_cpus_end(void)
406 {
407 }
408
409 void __ref enable_nonboot_cpus(void)
410 {
411         int cpu, error;
412
413         /* Allow everyone to use the CPU hotplug again */
414         cpu_maps_update_begin();
415         cpu_hotplug_disabled = 0;
416         if (cpumask_empty(frozen_cpus))
417                 goto out;
418
419         printk("Enabling non-boot CPUs ...\n");
420
421         arch_enable_nonboot_cpus_begin();
422
423         for_each_cpu(cpu, frozen_cpus) {
424                 error = _cpu_up(cpu, 1);
425                 if (!error) {
426                         printk("CPU%d is up\n", cpu);
427                         continue;
428                 }
429                 printk(KERN_WARNING "Error taking CPU%d up: %d\n", cpu, error);
430         }
431
432         arch_enable_nonboot_cpus_end();
433
434         cpumask_clear(frozen_cpus);
435 out:
436         cpu_maps_update_done();
437 }
438
439 static int alloc_frozen_cpus(void)
440 {
441         if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
442                 return -ENOMEM;
443         return 0;
444 }
445 core_initcall(alloc_frozen_cpus);
446 #endif /* CONFIG_PM_SLEEP_SMP */
447
448 /**
449  * notify_cpu_starting(cpu) - call the CPU_STARTING notifiers
450  * @cpu: cpu that just started
451  *
452  * This function calls the cpu_chain notifiers with CPU_STARTING.
453  * It must be called by the arch code on the new cpu, before the new cpu
454  * enables interrupts and before the "boot" cpu returns from __cpu_up().
455  */
456 void __cpuinit notify_cpu_starting(unsigned int cpu)
457 {
458         unsigned long val = CPU_STARTING;
459
460 #ifdef CONFIG_PM_SLEEP_SMP
461         if (frozen_cpus != NULL && cpumask_test_cpu(cpu, frozen_cpus))
462                 val = CPU_STARTING_FROZEN;
463 #endif /* CONFIG_PM_SLEEP_SMP */
464         raw_notifier_call_chain(&cpu_chain, val, (void *)(long)cpu);
465 }
466
467 #endif /* CONFIG_SMP */
468
469 /*
470  * cpu_bit_bitmap[] is a special, "compressed" data structure that
471  * represents all NR_CPUS bits binary values of 1<<nr.
472  *
473  * It is used by cpumask_of() to get a constant address to a CPU
474  * mask value that has a single bit set only.
475  */
476
477 /* cpu_bit_bitmap[0] is empty - so we can back into it */
478 #define MASK_DECLARE_1(x)       [x+1][0] = 1UL << (x)
479 #define MASK_DECLARE_2(x)       MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
480 #define MASK_DECLARE_4(x)       MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
481 #define MASK_DECLARE_8(x)       MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
482
483 const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
484
485         MASK_DECLARE_8(0),      MASK_DECLARE_8(8),
486         MASK_DECLARE_8(16),     MASK_DECLARE_8(24),
487 #if BITS_PER_LONG > 32
488         MASK_DECLARE_8(32),     MASK_DECLARE_8(40),
489         MASK_DECLARE_8(48),     MASK_DECLARE_8(56),
490 #endif
491 };
492 EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
493
494 const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
495 EXPORT_SYMBOL(cpu_all_bits);
496
497 #ifdef CONFIG_INIT_ALL_POSSIBLE
498 static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly
499         = CPU_BITS_ALL;
500 #else
501 static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly;
502 #endif
503 const struct cpumask *const cpu_possible_mask = to_cpumask(cpu_possible_bits);
504 EXPORT_SYMBOL(cpu_possible_mask);
505
506 static DECLARE_BITMAP(cpu_online_bits, CONFIG_NR_CPUS) __read_mostly;
507 const struct cpumask *const cpu_online_mask = to_cpumask(cpu_online_bits);
508 EXPORT_SYMBOL(cpu_online_mask);
509
510 static DECLARE_BITMAP(cpu_present_bits, CONFIG_NR_CPUS) __read_mostly;
511 const struct cpumask *const cpu_present_mask = to_cpumask(cpu_present_bits);
512 EXPORT_SYMBOL(cpu_present_mask);
513
514 static DECLARE_BITMAP(cpu_active_bits, CONFIG_NR_CPUS) __read_mostly;
515 const struct cpumask *const cpu_active_mask = to_cpumask(cpu_active_bits);
516 EXPORT_SYMBOL(cpu_active_mask);
517
518 void set_cpu_possible(unsigned int cpu, bool possible)
519 {
520         if (possible)
521                 cpumask_set_cpu(cpu, to_cpumask(cpu_possible_bits));
522         else
523                 cpumask_clear_cpu(cpu, to_cpumask(cpu_possible_bits));
524 }
525
526 void set_cpu_present(unsigned int cpu, bool present)
527 {
528         if (present)
529                 cpumask_set_cpu(cpu, to_cpumask(cpu_present_bits));
530         else
531                 cpumask_clear_cpu(cpu, to_cpumask(cpu_present_bits));
532 }
533
534 void set_cpu_online(unsigned int cpu, bool online)
535 {
536         if (online)
537                 cpumask_set_cpu(cpu, to_cpumask(cpu_online_bits));
538         else
539                 cpumask_clear_cpu(cpu, to_cpumask(cpu_online_bits));
540 }
541
542 void set_cpu_active(unsigned int cpu, bool active)
543 {
544         if (active)
545                 cpumask_set_cpu(cpu, to_cpumask(cpu_active_bits));
546         else
547                 cpumask_clear_cpu(cpu, to_cpumask(cpu_active_bits));
548 }
549
550 void init_cpu_present(const struct cpumask *src)
551 {
552         cpumask_copy(to_cpumask(cpu_present_bits), src);
553 }
554
555 void init_cpu_possible(const struct cpumask *src)
556 {
557         cpumask_copy(to_cpumask(cpu_possible_bits), src);
558 }
559
560 void init_cpu_online(const struct cpumask *src)
561 {
562         cpumask_copy(to_cpumask(cpu_online_bits), src);
563 }