ff071e022a854b2ebea9f887174d09fde1522eb1
[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 <asm/tboot.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 &&
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         unsigned long mod;
168         void *hcpu;
169 };
170
171 /* Take this CPU down. */
172 static 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 */
192 static 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         err = __raw_notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE | mod,
214                                         hcpu, -1, &nr_calls);
215         if (err == NOTIFY_BAD) {
216                 nr_calls--;
217                 __raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED | mod,
218                                           hcpu, nr_calls, NULL);
219                 printk("%s: attempt to take down CPU %u failed\n",
220                                 __func__, cpu);
221                 err = -EINVAL;
222                 goto out_release;
223         }
224
225         /* Ensure that we are not runnable on dying cpu */
226         cpumask_copy(old_allowed, &current->cpus_allowed);
227         set_cpus_allowed_ptr(current,
228                              cpumask_of(cpumask_any_but(cpu_online_mask, cpu)));
229
230         err = __stop_machine(take_cpu_down, &tcd_param, cpumask_of(cpu));
231         if (err) {
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_allowed;
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_allowed:
256         set_cpus_allowed_ptr(current, old_allowed);
257 out_release:
258         cpu_hotplug_done();
259         if (!err) {
260                 if (raw_notifier_call_chain(&cpu_chain, CPU_POST_DEAD | mod,
261                                             hcpu) == NOTIFY_BAD)
262                         BUG();
263         }
264         free_cpumask_var(old_allowed);
265         return err;
266 }
267
268 int __ref cpu_down(unsigned int cpu)
269 {
270         int err;
271
272         err = stop_machine_create();
273         if (err)
274                 return err;
275         cpu_maps_update_begin();
276
277         if (cpu_hotplug_disabled) {
278                 err = -EBUSY;
279                 goto out;
280         }
281
282         set_cpu_active(cpu, false);
283
284         /*
285          * Make sure the all cpus did the reschedule and are not
286          * using stale version of the cpu_active_mask.
287          * This is not strictly necessary becuase stop_machine()
288          * that we run down the line already provides the required
289          * synchronization. But it's really a side effect and we do not
290          * want to depend on the innards of the stop_machine here.
291          */
292         synchronize_sched();
293
294         err = _cpu_down(cpu, 0);
295
296         if (cpu_online(cpu))
297                 set_cpu_active(cpu, true);
298
299 out:
300         cpu_maps_update_done();
301         stop_machine_destroy();
302         return err;
303 }
304 EXPORT_SYMBOL(cpu_down);
305 #endif /*CONFIG_HOTPLUG_CPU*/
306
307 /* Requires cpu_add_remove_lock to be held */
308 static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen)
309 {
310         int ret, nr_calls = 0;
311         void *hcpu = (void *)(long)cpu;
312         unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
313
314         if (cpu_online(cpu) || !cpu_present(cpu))
315                 return -EINVAL;
316
317         cpu_hotplug_begin();
318         ret = __raw_notifier_call_chain(&cpu_chain, CPU_UP_PREPARE | mod, hcpu,
319                                                         -1, &nr_calls);
320         if (ret == NOTIFY_BAD) {
321                 nr_calls--;
322                 printk("%s: attempt to bring up CPU %u failed\n",
323                                 __func__, cpu);
324                 ret = -EINVAL;
325                 goto out_notify;
326         }
327
328         /* Arch-specific enabling code. */
329         ret = __cpu_up(cpu);
330         if (ret != 0)
331                 goto out_notify;
332         BUG_ON(!cpu_online(cpu));
333
334         set_cpu_active(cpu, true);
335
336         /* Now call notifier in preparation. */
337         raw_notifier_call_chain(&cpu_chain, CPU_ONLINE | mod, hcpu);
338
339 out_notify:
340         if (ret != 0)
341                 __raw_notifier_call_chain(&cpu_chain,
342                                 CPU_UP_CANCELED | mod, hcpu, nr_calls, NULL);
343         cpu_hotplug_done();
344
345         return ret;
346 }
347
348 int __cpuinit cpu_up(unsigned int cpu)
349 {
350         int err = 0;
351         if (!cpu_possible(cpu)) {
352                 printk(KERN_ERR "can't online cpu %d because it is not "
353                         "configured as may-hotadd at boot time\n", cpu);
354 #if defined(CONFIG_IA64) || defined(CONFIG_X86_64)
355                 printk(KERN_ERR "please check additional_cpus= boot "
356                                 "parameter\n");
357 #endif
358                 return -EINVAL;
359         }
360
361         cpu_maps_update_begin();
362
363         if (cpu_hotplug_disabled) {
364                 err = -EBUSY;
365                 goto out;
366         }
367
368         err = _cpu_up(cpu, 0);
369
370 out:
371         cpu_maps_update_done();
372         return err;
373 }
374
375 #ifdef CONFIG_PM_SLEEP_SMP
376 static cpumask_var_t frozen_cpus;
377
378 int disable_nonboot_cpus(void)
379 {
380         int cpu, first_cpu, error, num_cpus = 0;
381
382         error = stop_machine_create();
383         if (error)
384                 return error;
385         cpu_maps_update_begin();
386         first_cpu = cpumask_first(cpu_online_mask);
387         /* We take down all of the non-boot CPUs in one shot to avoid races
388          * with the userspace trying to use the CPU hotplug at the same time
389          */
390         cpumask_clear(frozen_cpus);
391         printk("Disabling non-boot CPUs ...\n");
392         for_each_online_cpu(cpu) {
393                 if (cpu == first_cpu)
394                         continue;
395                 num_cpus++;
396                 error = _cpu_down(cpu, 1);
397                 if (!error) {
398                         cpumask_set_cpu(cpu, frozen_cpus);
399                         printk("CPU%d is down\n", cpu);
400                 } else {
401                         printk(KERN_ERR "Error taking CPU%d down: %d\n",
402                                 cpu, error);
403                         break;
404                 }
405         }
406         /* ensure all CPUs have gone into wait-for-SIPI */
407         error |= tboot_wait_for_aps(num_cpus);
408
409         if (!error) {
410                 BUG_ON(num_online_cpus() > 1);
411                 /* Make sure the CPUs won't be enabled by someone else */
412                 cpu_hotplug_disabled = 1;
413         } else {
414                 printk(KERN_ERR "Non-boot CPUs are not disabled\n");
415         }
416         cpu_maps_update_done();
417         stop_machine_destroy();
418         return error;
419 }
420
421 void __ref enable_nonboot_cpus(void)
422 {
423         int cpu, error;
424
425         /* Allow everyone to use the CPU hotplug again */
426         cpu_maps_update_begin();
427         cpu_hotplug_disabled = 0;
428         if (cpumask_empty(frozen_cpus))
429                 goto out;
430
431         printk("Enabling non-boot CPUs ...\n");
432         for_each_cpu(cpu, frozen_cpus) {
433                 error = _cpu_up(cpu, 1);
434                 if (!error) {
435                         printk("CPU%d is up\n", cpu);
436                         continue;
437                 }
438                 printk(KERN_WARNING "Error taking CPU%d up: %d\n", cpu, error);
439         }
440         cpumask_clear(frozen_cpus);
441 out:
442         cpu_maps_update_done();
443 }
444
445 static int alloc_frozen_cpus(void)
446 {
447         if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
448                 return -ENOMEM;
449         return 0;
450 }
451 core_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  */
462 void __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
489 const 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 };
498 EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
499
500 const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
501 EXPORT_SYMBOL(cpu_all_bits);
502
503 #ifdef CONFIG_INIT_ALL_POSSIBLE
504 static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly
505         = CPU_BITS_ALL;
506 #else
507 static DECLARE_BITMAP(cpu_possible_bits, CONFIG_NR_CPUS) __read_mostly;
508 #endif
509 const struct cpumask *const cpu_possible_mask = to_cpumask(cpu_possible_bits);
510 EXPORT_SYMBOL(cpu_possible_mask);
511
512 static DECLARE_BITMAP(cpu_online_bits, CONFIG_NR_CPUS) __read_mostly;
513 const struct cpumask *const cpu_online_mask = to_cpumask(cpu_online_bits);
514 EXPORT_SYMBOL(cpu_online_mask);
515
516 static DECLARE_BITMAP(cpu_present_bits, CONFIG_NR_CPUS) __read_mostly;
517 const struct cpumask *const cpu_present_mask = to_cpumask(cpu_present_bits);
518 EXPORT_SYMBOL(cpu_present_mask);
519
520 static DECLARE_BITMAP(cpu_active_bits, CONFIG_NR_CPUS) __read_mostly;
521 const struct cpumask *const cpu_active_mask = to_cpumask(cpu_active_bits);
522 EXPORT_SYMBOL(cpu_active_mask);
523
524 void 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
532 void 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
540 void 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
548 void 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
556 void init_cpu_present(const struct cpumask *src)
557 {
558         cpumask_copy(to_cpumask(cpu_present_bits), src);
559 }
560
561 void init_cpu_possible(const struct cpumask *src)
562 {
563         cpumask_copy(to_cpumask(cpu_possible_bits), src);
564 }
565
566 void init_cpu_online(const struct cpumask *src)
567 {
568         cpumask_copy(to_cpumask(cpu_online_bits), src);
569 }