2 * (C) 2001, 2002, 2003, 2004 Rusty Russell
4 * This code is licenced under the GPL.
6 #include <linux/proc_fs.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>
20 /* Serializes the updates to cpu_online_mask, cpu_present_mask */
21 static DEFINE_MUTEX(cpu_add_remove_lock
);
24 * The following two API's must be used when attempting
25 * to serialize the updates to cpu_online_mask, cpu_present_mask.
27 void cpu_maps_update_begin(void)
29 mutex_lock(&cpu_add_remove_lock
);
32 void cpu_maps_update_done(void)
34 mutex_unlock(&cpu_add_remove_lock
);
37 static RAW_NOTIFIER_HEAD(cpu_chain
);
39 /* If set, cpu_up and cpu_down will return -EBUSY and do nothing.
40 * Should always be manipulated under cpu_add_remove_lock
42 static int cpu_hotplug_disabled
;
44 #ifdef CONFIG_HOTPLUG_CPU
47 struct task_struct
*active_writer
;
48 struct mutex lock
; /* Synchronizes accesses to refcount, */
50 * Also blocks the new readers during
51 * an ongoing cpu hotplug operation.
55 .active_writer
= NULL
,
56 .lock
= __MUTEX_INITIALIZER(cpu_hotplug
.lock
),
60 void get_online_cpus(void)
63 if (cpu_hotplug
.active_writer
== current
)
65 mutex_lock(&cpu_hotplug
.lock
);
66 cpu_hotplug
.refcount
++;
67 mutex_unlock(&cpu_hotplug
.lock
);
70 EXPORT_SYMBOL_GPL(get_online_cpus
);
72 void put_online_cpus(void)
74 if (cpu_hotplug
.active_writer
== current
)
76 mutex_lock(&cpu_hotplug
.lock
);
77 if (!--cpu_hotplug
.refcount
&& unlikely(cpu_hotplug
.active_writer
))
78 wake_up_process(cpu_hotplug
.active_writer
);
79 mutex_unlock(&cpu_hotplug
.lock
);
82 EXPORT_SYMBOL_GPL(put_online_cpus
);
85 * This ensures that the hotplug operation can begin only when the
86 * refcount goes to zero.
88 * Note that during a cpu-hotplug operation, the new readers, if any,
89 * will be blocked by the cpu_hotplug.lock
91 * Since cpu_hotplug_begin() is always called after invoking
92 * cpu_maps_update_begin(), we can be sure that only one writer is active.
94 * Note that theoretically, there is a possibility of a livelock:
95 * - Refcount goes to zero, last reader wakes up the sleeping
97 * - Last reader unlocks the cpu_hotplug.lock.
98 * - A new reader arrives at this moment, bumps up the refcount.
99 * - The writer acquires the cpu_hotplug.lock finds the refcount
100 * non zero and goes to sleep again.
102 * However, this is very difficult to achieve in practice since
103 * get_online_cpus() not an api which is called all that often.
106 static void cpu_hotplug_begin(void)
108 cpu_hotplug
.active_writer
= current
;
111 mutex_lock(&cpu_hotplug
.lock
);
112 if (likely(!cpu_hotplug
.refcount
))
114 __set_current_state(TASK_UNINTERRUPTIBLE
);
115 mutex_unlock(&cpu_hotplug
.lock
);
120 static void cpu_hotplug_done(void)
122 cpu_hotplug
.active_writer
= NULL
;
123 mutex_unlock(&cpu_hotplug
.lock
);
126 #else /* #if CONFIG_HOTPLUG_CPU */
127 static void cpu_hotplug_begin(void) {}
128 static void cpu_hotplug_done(void) {}
129 #endif /* #esle #if CONFIG_HOTPLUG_CPU */
131 /* Need to know about CPUs going up/down? */
132 int __ref
register_cpu_notifier(struct notifier_block
*nb
)
135 cpu_maps_update_begin();
136 ret
= raw_notifier_chain_register(&cpu_chain
, nb
);
137 cpu_maps_update_done();
141 static int __cpu_notify(unsigned long val
, void *v
, int nr_to_call
,
146 ret
= __raw_notifier_call_chain(&cpu_chain
, val
, v
, nr_to_call
,
149 return notifier_to_errno(ret
);
152 static int cpu_notify(unsigned long val
, void *v
)
154 return __cpu_notify(val
, v
, -1, NULL
);
157 #ifdef CONFIG_HOTPLUG_CPU
159 static void cpu_notify_nofail(unsigned long val
, void *v
)
161 BUG_ON(cpu_notify(val
, v
));
164 EXPORT_SYMBOL(register_cpu_notifier
);
166 void __ref
unregister_cpu_notifier(struct notifier_block
*nb
)
168 cpu_maps_update_begin();
169 raw_notifier_chain_unregister(&cpu_chain
, nb
);
170 cpu_maps_update_done();
172 EXPORT_SYMBOL(unregister_cpu_notifier
);
174 static inline void check_for_tasks(int cpu
)
176 struct task_struct
*p
;
178 write_lock_irq(&tasklist_lock
);
179 for_each_process(p
) {
180 if (task_cpu(p
) == cpu
&& p
->state
== TASK_RUNNING
&&
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
,
188 write_unlock_irq(&tasklist_lock
);
191 struct take_cpu_down_param
{
196 /* Take this CPU down. */
197 static int __ref
take_cpu_down(void *_param
)
199 struct take_cpu_down_param
*param
= _param
;
202 /* Ensure this CPU doesn't handle any more interrupts. */
203 err
= __cpu_disable();
207 cpu_notify(CPU_DYING
| param
->mod
, param
->hcpu
);
212 /* Requires cpu_add_remove_lock to be held */
213 static int __ref
_cpu_down(unsigned int cpu
, int tasks_frozen
)
215 int err
, nr_calls
= 0;
216 void *hcpu
= (void *)(long)cpu
;
217 unsigned long mod
= tasks_frozen
? CPU_TASKS_FROZEN
: 0;
218 struct take_cpu_down_param tcd_param
= {
223 if (num_online_cpus() == 1)
226 if (!cpu_online(cpu
))
230 err
= __cpu_notify(CPU_DOWN_PREPARE
| mod
, hcpu
, -1, &nr_calls
);
233 __cpu_notify(CPU_DOWN_FAILED
| mod
, hcpu
, nr_calls
, NULL
);
234 printk("%s: attempt to take down CPU %u failed\n",
239 err
= __stop_machine(take_cpu_down
, &tcd_param
, cpumask_of(cpu
));
241 /* CPU didn't die: tell everyone. Can't complain. */
242 cpu_notify_nofail(CPU_DOWN_FAILED
| mod
, hcpu
);
246 BUG_ON(cpu_online(cpu
));
249 * The migration_call() CPU_DYING callback will have removed all
250 * runnable tasks from the cpu, there's only the idle task left now
251 * that the migration thread is done doing the stop_machine thing.
253 BUG_ON(!idle_cpu(cpu
));
255 /* This actually kills the CPU. */
258 /* CPU is completely dead: tell everyone. Too late to complain. */
259 cpu_notify_nofail(CPU_DEAD
| mod
, hcpu
);
261 check_for_tasks(cpu
);
266 cpu_notify_nofail(CPU_POST_DEAD
| mod
, hcpu
);
270 int __ref
cpu_down(unsigned int cpu
)
274 cpu_maps_update_begin();
276 if (cpu_hotplug_disabled
) {
281 err
= _cpu_down(cpu
, 0);
284 cpu_maps_update_done();
287 EXPORT_SYMBOL(cpu_down
);
288 #endif /*CONFIG_HOTPLUG_CPU*/
290 /* Requires cpu_add_remove_lock to be held */
291 static int __cpuinit
_cpu_up(unsigned int cpu
, int tasks_frozen
)
293 int ret
, nr_calls
= 0;
294 void *hcpu
= (void *)(long)cpu
;
295 unsigned long mod
= tasks_frozen
? CPU_TASKS_FROZEN
: 0;
297 if (cpu_online(cpu
) || !cpu_present(cpu
))
301 ret
= __cpu_notify(CPU_UP_PREPARE
| mod
, hcpu
, -1, &nr_calls
);
304 printk("%s: attempt to bring up CPU %u failed\n",
309 /* Arch-specific enabling code. */
313 BUG_ON(!cpu_online(cpu
));
315 /* Now call notifier in preparation. */
316 cpu_notify(CPU_ONLINE
| mod
, hcpu
);
320 __cpu_notify(CPU_UP_CANCELED
| mod
, hcpu
, nr_calls
, NULL
);
326 int __cpuinit
cpu_up(unsigned int cpu
)
330 #ifdef CONFIG_MEMORY_HOTPLUG
335 if (!cpu_possible(cpu
)) {
336 printk(KERN_ERR
"can't online cpu %d because it is not "
337 "configured as may-hotadd at boot time\n", cpu
);
338 #if defined(CONFIG_IA64)
339 printk(KERN_ERR
"please check additional_cpus= boot "
345 #ifdef CONFIG_MEMORY_HOTPLUG
346 nid
= cpu_to_node(cpu
);
347 if (!node_online(nid
)) {
348 err
= mem_online_node(nid
);
353 pgdat
= NODE_DATA(nid
);
356 "Can't online cpu %d due to NULL pgdat\n", cpu
);
360 if (pgdat
->node_zonelists
->_zonerefs
->zone
== NULL
) {
361 mutex_lock(&zonelists_mutex
);
362 build_all_zonelists(NULL
);
363 mutex_unlock(&zonelists_mutex
);
367 cpu_maps_update_begin();
369 if (cpu_hotplug_disabled
) {
374 err
= _cpu_up(cpu
, 0);
377 cpu_maps_update_done();
381 #ifdef CONFIG_PM_SLEEP_SMP
382 static cpumask_var_t frozen_cpus
;
384 int disable_nonboot_cpus(void)
386 int cpu
, first_cpu
, error
= 0;
388 cpu_maps_update_begin();
389 first_cpu
= cpumask_first(cpu_online_mask
);
391 * We take down all of the non-boot CPUs in one shot to avoid races
392 * with the userspace trying to use the CPU hotplug at the same time
394 cpumask_clear(frozen_cpus
);
396 printk("Disabling non-boot CPUs ...\n");
397 for_each_online_cpu(cpu
) {
398 if (cpu
== first_cpu
)
400 error
= _cpu_down(cpu
, 1);
402 cpumask_set_cpu(cpu
, frozen_cpus
);
404 printk(KERN_ERR
"Error taking CPU%d down: %d\n",
411 BUG_ON(num_online_cpus() > 1);
412 /* Make sure the CPUs won't be enabled by someone else */
413 cpu_hotplug_disabled
= 1;
415 printk(KERN_ERR
"Non-boot CPUs are not disabled\n");
417 cpu_maps_update_done();
421 void __weak
arch_enable_nonboot_cpus_begin(void)
425 void __weak
arch_enable_nonboot_cpus_end(void)
429 void __ref
enable_nonboot_cpus(void)
433 /* Allow everyone to use the CPU hotplug again */
434 cpu_maps_update_begin();
435 cpu_hotplug_disabled
= 0;
436 if (cpumask_empty(frozen_cpus
))
439 printk("Enabling non-boot CPUs ...\n");
441 arch_enable_nonboot_cpus_begin();
443 for_each_cpu(cpu
, frozen_cpus
) {
444 error
= _cpu_up(cpu
, 1);
446 printk("CPU%d is up\n", cpu
);
449 printk(KERN_WARNING
"Error taking CPU%d up: %d\n", cpu
, error
);
452 arch_enable_nonboot_cpus_end();
454 cpumask_clear(frozen_cpus
);
456 cpu_maps_update_done();
459 static int alloc_frozen_cpus(void)
461 if (!alloc_cpumask_var(&frozen_cpus
, GFP_KERNEL
|__GFP_ZERO
))
465 core_initcall(alloc_frozen_cpus
);
466 #endif /* CONFIG_PM_SLEEP_SMP */
469 * notify_cpu_starting(cpu) - call the CPU_STARTING notifiers
470 * @cpu: cpu that just started
472 * This function calls the cpu_chain notifiers with CPU_STARTING.
473 * It must be called by the arch code on the new cpu, before the new cpu
474 * enables interrupts and before the "boot" cpu returns from __cpu_up().
476 void __cpuinit
notify_cpu_starting(unsigned int cpu
)
478 unsigned long val
= CPU_STARTING
;
480 #ifdef CONFIG_PM_SLEEP_SMP
481 if (frozen_cpus
!= NULL
&& cpumask_test_cpu(cpu
, frozen_cpus
))
482 val
= CPU_STARTING_FROZEN
;
483 #endif /* CONFIG_PM_SLEEP_SMP */
484 cpu_notify(val
, (void *)(long)cpu
);
487 #endif /* CONFIG_SMP */
490 * cpu_bit_bitmap[] is a special, "compressed" data structure that
491 * represents all NR_CPUS bits binary values of 1<<nr.
493 * It is used by cpumask_of() to get a constant address to a CPU
494 * mask value that has a single bit set only.
497 /* cpu_bit_bitmap[0] is empty - so we can back into it */
498 #define MASK_DECLARE_1(x) [x+1][0] = 1UL << (x)
499 #define MASK_DECLARE_2(x) MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
500 #define MASK_DECLARE_4(x) MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
501 #define MASK_DECLARE_8(x) MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
503 const unsigned long cpu_bit_bitmap
[BITS_PER_LONG
+1][BITS_TO_LONGS(NR_CPUS
)] = {
505 MASK_DECLARE_8(0), MASK_DECLARE_8(8),
506 MASK_DECLARE_8(16), MASK_DECLARE_8(24),
507 #if BITS_PER_LONG > 32
508 MASK_DECLARE_8(32), MASK_DECLARE_8(40),
509 MASK_DECLARE_8(48), MASK_DECLARE_8(56),
512 EXPORT_SYMBOL_GPL(cpu_bit_bitmap
);
514 const DECLARE_BITMAP(cpu_all_bits
, NR_CPUS
) = CPU_BITS_ALL
;
515 EXPORT_SYMBOL(cpu_all_bits
);
517 #ifdef CONFIG_INIT_ALL_POSSIBLE
518 static DECLARE_BITMAP(cpu_possible_bits
, CONFIG_NR_CPUS
) __read_mostly
521 static DECLARE_BITMAP(cpu_possible_bits
, CONFIG_NR_CPUS
) __read_mostly
;
523 const struct cpumask
*const cpu_possible_mask
= to_cpumask(cpu_possible_bits
);
524 EXPORT_SYMBOL(cpu_possible_mask
);
526 static DECLARE_BITMAP(cpu_online_bits
, CONFIG_NR_CPUS
) __read_mostly
;
527 const struct cpumask
*const cpu_online_mask
= to_cpumask(cpu_online_bits
);
528 EXPORT_SYMBOL(cpu_online_mask
);
530 static DECLARE_BITMAP(cpu_present_bits
, CONFIG_NR_CPUS
) __read_mostly
;
531 const struct cpumask
*const cpu_present_mask
= to_cpumask(cpu_present_bits
);
532 EXPORT_SYMBOL(cpu_present_mask
);
534 static DECLARE_BITMAP(cpu_active_bits
, CONFIG_NR_CPUS
) __read_mostly
;
535 const struct cpumask
*const cpu_active_mask
= to_cpumask(cpu_active_bits
);
536 EXPORT_SYMBOL(cpu_active_mask
);
538 void set_cpu_possible(unsigned int cpu
, bool possible
)
541 cpumask_set_cpu(cpu
, to_cpumask(cpu_possible_bits
));
543 cpumask_clear_cpu(cpu
, to_cpumask(cpu_possible_bits
));
546 void set_cpu_present(unsigned int cpu
, bool present
)
549 cpumask_set_cpu(cpu
, to_cpumask(cpu_present_bits
));
551 cpumask_clear_cpu(cpu
, to_cpumask(cpu_present_bits
));
554 void set_cpu_online(unsigned int cpu
, bool online
)
557 cpumask_set_cpu(cpu
, to_cpumask(cpu_online_bits
));
559 cpumask_clear_cpu(cpu
, to_cpumask(cpu_online_bits
));
562 void set_cpu_active(unsigned int cpu
, bool active
)
565 cpumask_set_cpu(cpu
, to_cpumask(cpu_active_bits
));
567 cpumask_clear_cpu(cpu
, to_cpumask(cpu_active_bits
));
570 void init_cpu_present(const struct cpumask
*src
)
572 cpumask_copy(to_cpumask(cpu_present_bits
), src
);
575 void init_cpu_possible(const struct cpumask
*src
)
577 cpumask_copy(to_cpumask(cpu_possible_bits
), src
);
580 void init_cpu_online(const struct cpumask
*src
)
582 cpumask_copy(to_cpumask(cpu_online_bits
), src
);