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
);
23 static __cpuinitdata
RAW_NOTIFIER_HEAD(cpu_chain
);
25 /* If set, cpu_up and cpu_down will return -EBUSY and do nothing.
26 * Should always be manipulated under cpu_add_remove_lock
28 static int cpu_hotplug_disabled
;
31 struct task_struct
*active_writer
;
32 struct mutex lock
; /* Synchronizes accesses to refcount, */
34 * Also blocks the new readers during
35 * an ongoing cpu hotplug operation.
39 .active_writer
= NULL
,
40 .lock
= __MUTEX_INITIALIZER(cpu_hotplug
.lock
),
44 #ifdef CONFIG_HOTPLUG_CPU
46 void get_online_cpus(void)
49 if (cpu_hotplug
.active_writer
== current
)
51 mutex_lock(&cpu_hotplug
.lock
);
52 cpu_hotplug
.refcount
++;
53 mutex_unlock(&cpu_hotplug
.lock
);
56 EXPORT_SYMBOL_GPL(get_online_cpus
);
58 void put_online_cpus(void)
60 if (cpu_hotplug
.active_writer
== current
)
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
);
68 EXPORT_SYMBOL_GPL(put_online_cpus
);
70 #endif /* CONFIG_HOTPLUG_CPU */
73 * The following two API's must be used when attempting
74 * to serialize the updates to cpu_online_mask, cpu_present_mask.
76 void cpu_maps_update_begin(void)
78 mutex_lock(&cpu_add_remove_lock
);
81 void cpu_maps_update_done(void)
83 mutex_unlock(&cpu_add_remove_lock
);
87 * This ensures that the hotplug operation can begin only when the
88 * refcount goes to zero.
90 * Note that during a cpu-hotplug operation, the new readers, if any,
91 * will be blocked by the cpu_hotplug.lock
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.
96 * Note that theoretically, there is a possibility of a livelock:
97 * - Refcount goes to zero, last reader wakes up the sleeping
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.
104 * However, this is very difficult to achieve in practice since
105 * get_online_cpus() not an api which is called all that often.
108 static void cpu_hotplug_begin(void)
110 cpu_hotplug
.active_writer
= current
;
113 mutex_lock(&cpu_hotplug
.lock
);
114 if (likely(!cpu_hotplug
.refcount
))
116 __set_current_state(TASK_UNINTERRUPTIBLE
);
117 mutex_unlock(&cpu_hotplug
.lock
);
122 static void cpu_hotplug_done(void)
124 cpu_hotplug
.active_writer
= NULL
;
125 mutex_unlock(&cpu_hotplug
.lock
);
127 /* Need to know about CPUs going up/down? */
128 int __ref
register_cpu_notifier(struct notifier_block
*nb
)
131 cpu_maps_update_begin();
132 ret
= raw_notifier_chain_register(&cpu_chain
, nb
);
133 cpu_maps_update_done();
137 #ifdef CONFIG_HOTPLUG_CPU
139 EXPORT_SYMBOL(register_cpu_notifier
);
141 void __ref
unregister_cpu_notifier(struct notifier_block
*nb
)
143 cpu_maps_update_begin();
144 raw_notifier_chain_unregister(&cpu_chain
, nb
);
145 cpu_maps_update_done();
147 EXPORT_SYMBOL(unregister_cpu_notifier
);
149 static inline void check_for_tasks(int cpu
)
151 struct task_struct
*p
;
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
,
163 write_unlock_irq(&tasklist_lock
);
166 struct take_cpu_down_param
{
167 struct task_struct
*caller
;
172 /* Take this CPU down. */
173 static int __ref
take_cpu_down(void *_param
)
175 struct take_cpu_down_param
*param
= _param
;
176 unsigned int cpu
= (unsigned long)param
->hcpu
;
179 /* Ensure this CPU doesn't handle any more interrupts. */
180 err
= __cpu_disable();
184 raw_notifier_call_chain(&cpu_chain
, CPU_DYING
| param
->mod
,
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. */
195 /* Requires cpu_add_remove_lock to be held */
196 static int __ref
_cpu_down(unsigned int cpu
, int tasks_frozen
)
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
= {
207 if (num_online_cpus() == 1)
210 if (!cpu_online(cpu
))
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);
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",
229 err
= __stop_machine(take_cpu_down
, &tcd_param
, cpumask_of(cpu
));
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
,
239 BUG_ON(cpu_online(cpu
));
241 /* Wait for it to sleep (leaving idle task). */
242 while (!idle_cpu(cpu
))
245 /* This actually kills the CPU. */
248 /* CPU is completely dead: tell everyone. Too late to complain. */
249 if (raw_notifier_call_chain(&cpu_chain
, CPU_DEAD
| mod
,
253 check_for_tasks(cpu
);
258 if (raw_notifier_call_chain(&cpu_chain
, CPU_POST_DEAD
| mod
,
265 int __ref
cpu_down(unsigned int cpu
)
269 cpu_maps_update_begin();
271 if (cpu_hotplug_disabled
) {
276 err
= _cpu_down(cpu
, 0);
279 cpu_maps_update_done();
282 EXPORT_SYMBOL(cpu_down
);
283 #endif /*CONFIG_HOTPLUG_CPU*/
285 /* Requires cpu_add_remove_lock to be held */
286 static int __cpuinit
_cpu_up(unsigned int cpu
, int tasks_frozen
)
288 int ret
, nr_calls
= 0;
289 void *hcpu
= (void *)(long)cpu
;
290 unsigned long mod
= tasks_frozen
? CPU_TASKS_FROZEN
: 0;
292 if (cpu_online(cpu
) || !cpu_present(cpu
))
296 ret
= __raw_notifier_call_chain(&cpu_chain
, CPU_UP_PREPARE
| mod
, hcpu
,
298 if (ret
== NOTIFY_BAD
) {
300 printk("%s: attempt to bring up CPU %u failed\n",
306 /* Arch-specific enabling code. */
310 BUG_ON(!cpu_online(cpu
));
312 set_cpu_active(cpu
, true);
314 /* Now call notifier in preparation. */
315 raw_notifier_call_chain(&cpu_chain
, CPU_ONLINE
| mod
, hcpu
);
319 __raw_notifier_call_chain(&cpu_chain
,
320 CPU_UP_CANCELED
| mod
, hcpu
, nr_calls
, NULL
);
326 int __cpuinit
cpu_up(unsigned int cpu
)
329 if (!cpu_possible(cpu
)) {
330 printk(KERN_ERR
"can't online cpu %d because it is not "
331 "configured as may-hotadd at boot time\n", cpu
);
332 #if defined(CONFIG_IA64)
333 printk(KERN_ERR
"please check additional_cpus= boot "
339 cpu_maps_update_begin();
341 if (cpu_hotplug_disabled
) {
346 err
= _cpu_up(cpu
, 0);
349 cpu_maps_update_done();
353 #ifdef CONFIG_PM_SLEEP_SMP
354 static cpumask_var_t frozen_cpus
;
356 int disable_nonboot_cpus(void)
358 int cpu
, first_cpu
, error
;
360 cpu_maps_update_begin();
361 first_cpu
= cpumask_first(cpu_online_mask
);
363 * We take down all of the non-boot CPUs in one shot to avoid races
364 * with the userspace trying to use the CPU hotplug at the same time
366 cpumask_clear(frozen_cpus
);
368 printk("Disabling non-boot CPUs ...\n");
369 for_each_online_cpu(cpu
) {
370 if (cpu
== first_cpu
)
372 error
= _cpu_down(cpu
, 1);
374 cpumask_set_cpu(cpu
, frozen_cpus
);
376 printk(KERN_ERR
"Error taking CPU%d down: %d\n",
383 BUG_ON(num_online_cpus() > 1);
384 /* Make sure the CPUs won't be enabled by someone else */
385 cpu_hotplug_disabled
= 1;
387 printk(KERN_ERR
"Non-boot CPUs are not disabled\n");
389 cpu_maps_update_done();
393 void __weak
arch_enable_nonboot_cpus_begin(void)
397 void __weak
arch_enable_nonboot_cpus_end(void)
401 void __ref
enable_nonboot_cpus(void)
405 /* Allow everyone to use the CPU hotplug again */
406 cpu_maps_update_begin();
407 cpu_hotplug_disabled
= 0;
408 if (cpumask_empty(frozen_cpus
))
411 printk("Enabling non-boot CPUs ...\n");
413 arch_enable_nonboot_cpus_begin();
415 for_each_cpu(cpu
, frozen_cpus
) {
416 error
= _cpu_up(cpu
, 1);
418 printk("CPU%d is up\n", cpu
);
421 printk(KERN_WARNING
"Error taking CPU%d up: %d\n", cpu
, error
);
424 arch_enable_nonboot_cpus_end();
426 cpumask_clear(frozen_cpus
);
428 cpu_maps_update_done();
431 static int alloc_frozen_cpus(void)
433 if (!alloc_cpumask_var(&frozen_cpus
, GFP_KERNEL
|__GFP_ZERO
))
437 core_initcall(alloc_frozen_cpus
);
438 #endif /* CONFIG_PM_SLEEP_SMP */
441 * notify_cpu_starting(cpu) - call the CPU_STARTING notifiers
442 * @cpu: cpu that just started
444 * This function calls the cpu_chain notifiers with CPU_STARTING.
445 * It must be called by the arch code on the new cpu, before the new cpu
446 * enables interrupts and before the "boot" cpu returns from __cpu_up().
448 void __cpuinit
notify_cpu_starting(unsigned int cpu
)
450 unsigned long val
= CPU_STARTING
;
452 #ifdef CONFIG_PM_SLEEP_SMP
453 if (frozen_cpus
!= NULL
&& cpumask_test_cpu(cpu
, frozen_cpus
))
454 val
= CPU_STARTING_FROZEN
;
455 #endif /* CONFIG_PM_SLEEP_SMP */
456 raw_notifier_call_chain(&cpu_chain
, val
, (void *)(long)cpu
);
459 #endif /* CONFIG_SMP */
462 * cpu_bit_bitmap[] is a special, "compressed" data structure that
463 * represents all NR_CPUS bits binary values of 1<<nr.
465 * It is used by cpumask_of() to get a constant address to a CPU
466 * mask value that has a single bit set only.
469 /* cpu_bit_bitmap[0] is empty - so we can back into it */
470 #define MASK_DECLARE_1(x) [x+1][0] = 1UL << (x)
471 #define MASK_DECLARE_2(x) MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
472 #define MASK_DECLARE_4(x) MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
473 #define MASK_DECLARE_8(x) MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
475 const unsigned long cpu_bit_bitmap
[BITS_PER_LONG
+1][BITS_TO_LONGS(NR_CPUS
)] = {
477 MASK_DECLARE_8(0), MASK_DECLARE_8(8),
478 MASK_DECLARE_8(16), MASK_DECLARE_8(24),
479 #if BITS_PER_LONG > 32
480 MASK_DECLARE_8(32), MASK_DECLARE_8(40),
481 MASK_DECLARE_8(48), MASK_DECLARE_8(56),
484 EXPORT_SYMBOL_GPL(cpu_bit_bitmap
);
486 const DECLARE_BITMAP(cpu_all_bits
, NR_CPUS
) = CPU_BITS_ALL
;
487 EXPORT_SYMBOL(cpu_all_bits
);
489 #ifdef CONFIG_INIT_ALL_POSSIBLE
490 static DECLARE_BITMAP(cpu_possible_bits
, CONFIG_NR_CPUS
) __read_mostly
493 static DECLARE_BITMAP(cpu_possible_bits
, CONFIG_NR_CPUS
) __read_mostly
;
495 const struct cpumask
*const cpu_possible_mask
= to_cpumask(cpu_possible_bits
);
496 EXPORT_SYMBOL(cpu_possible_mask
);
498 static DECLARE_BITMAP(cpu_online_bits
, CONFIG_NR_CPUS
) __read_mostly
;
499 const struct cpumask
*const cpu_online_mask
= to_cpumask(cpu_online_bits
);
500 EXPORT_SYMBOL(cpu_online_mask
);
502 static DECLARE_BITMAP(cpu_present_bits
, CONFIG_NR_CPUS
) __read_mostly
;
503 const struct cpumask
*const cpu_present_mask
= to_cpumask(cpu_present_bits
);
504 EXPORT_SYMBOL(cpu_present_mask
);
506 static DECLARE_BITMAP(cpu_active_bits
, CONFIG_NR_CPUS
) __read_mostly
;
507 const struct cpumask
*const cpu_active_mask
= to_cpumask(cpu_active_bits
);
508 EXPORT_SYMBOL(cpu_active_mask
);
510 void set_cpu_possible(unsigned int cpu
, bool possible
)
513 cpumask_set_cpu(cpu
, to_cpumask(cpu_possible_bits
));
515 cpumask_clear_cpu(cpu
, to_cpumask(cpu_possible_bits
));
518 void set_cpu_present(unsigned int cpu
, bool present
)
521 cpumask_set_cpu(cpu
, to_cpumask(cpu_present_bits
));
523 cpumask_clear_cpu(cpu
, to_cpumask(cpu_present_bits
));
526 void set_cpu_online(unsigned int cpu
, bool online
)
529 cpumask_set_cpu(cpu
, to_cpumask(cpu_online_bits
));
531 cpumask_clear_cpu(cpu
, to_cpumask(cpu_online_bits
));
534 void set_cpu_active(unsigned int cpu
, bool active
)
537 cpumask_set_cpu(cpu
, to_cpumask(cpu_active_bits
));
539 cpumask_clear_cpu(cpu
, to_cpumask(cpu_active_bits
));
542 void init_cpu_present(const struct cpumask
*src
)
544 cpumask_copy(to_cpumask(cpu_present_bits
), src
);
547 void init_cpu_possible(const struct cpumask
*src
)
549 cpumask_copy(to_cpumask(cpu_possible_bits
), src
);
552 void init_cpu_online(const struct cpumask
*src
)
554 cpumask_copy(to_cpumask(cpu_online_bits
), src
);