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>
19 * Represents all cpu's present in the system
20 * In systems capable of hotplug, this map could dynamically grow
21 * as new cpu's are detected in the system via any platform specific
22 * method, such as ACPI for e.g.
24 cpumask_t cpu_present_map __read_mostly;
25 EXPORT_SYMBOL(cpu_present_map);
30 * Represents all cpu's that are currently online.
32 cpumask_t cpu_online_map __read_mostly = CPU_MASK_ALL;
33 EXPORT_SYMBOL(cpu_online_map);
35 cpumask_t cpu_possible_map __read_mostly = CPU_MASK_ALL;
36 EXPORT_SYMBOL(cpu_possible_map);
38 #else /* CONFIG_SMP */
40 /* Serializes the updates to cpu_online_map, cpu_present_map */
41 static DEFINE_MUTEX(cpu_add_remove_lock);
43 static __cpuinitdata RAW_NOTIFIER_HEAD(cpu_chain);
45 /* If set, cpu_up and cpu_down will return -EBUSY and do nothing.
46 * Should always be manipulated under cpu_add_remove_lock
48 static int cpu_hotplug_disabled;
51 struct task_struct *active_writer;
52 struct mutex lock; /* Synchronizes accesses to refcount, */
54 * Also blocks the new readers during
55 * an ongoing cpu hotplug operation.
60 void __init cpu_hotplug_init(void)
62 cpu_hotplug.active_writer = NULL;
63 mutex_init(&cpu_hotplug.lock);
64 cpu_hotplug.refcount = 0;
67 cpumask_t cpu_active_map;
69 #ifdef CONFIG_HOTPLUG_CPU
71 void get_online_cpus(void)
74 if (cpu_hotplug.active_writer == current)
76 mutex_lock(&cpu_hotplug.lock);
77 cpu_hotplug.refcount++;
78 mutex_unlock(&cpu_hotplug.lock);
81 EXPORT_SYMBOL_GPL(get_online_cpus);
83 void put_online_cpus(void)
85 if (cpu_hotplug.active_writer == current)
87 mutex_lock(&cpu_hotplug.lock);
88 if (!--cpu_hotplug.refcount && unlikely(cpu_hotplug.active_writer))
89 wake_up_process(cpu_hotplug.active_writer);
90 mutex_unlock(&cpu_hotplug.lock);
93 EXPORT_SYMBOL_GPL(put_online_cpus);
95 #endif /* CONFIG_HOTPLUG_CPU */
98 * The following two API's must be used when attempting
99 * to serialize the updates to cpu_online_map, cpu_present_map.
101 void cpu_maps_update_begin(void)
103 mutex_lock(&cpu_add_remove_lock);
106 void cpu_maps_update_done(void)
108 mutex_unlock(&cpu_add_remove_lock);
112 * This ensures that the hotplug operation can begin only when the
113 * refcount goes to zero.
115 * Note that during a cpu-hotplug operation, the new readers, if any,
116 * will be blocked by the cpu_hotplug.lock
118 * Since cpu_hotplug_begin() is always called after invoking
119 * cpu_maps_update_begin(), we can be sure that only one writer is active.
121 * Note that theoretically, there is a possibility of a livelock:
122 * - Refcount goes to zero, last reader wakes up the sleeping
124 * - Last reader unlocks the cpu_hotplug.lock.
125 * - A new reader arrives at this moment, bumps up the refcount.
126 * - The writer acquires the cpu_hotplug.lock finds the refcount
127 * non zero and goes to sleep again.
129 * However, this is very difficult to achieve in practice since
130 * get_online_cpus() not an api which is called all that often.
133 static void cpu_hotplug_begin(void)
135 cpu_hotplug.active_writer = current;
138 mutex_lock(&cpu_hotplug.lock);
139 if (likely(!cpu_hotplug.refcount))
141 __set_current_state(TASK_UNINTERRUPTIBLE);
142 mutex_unlock(&cpu_hotplug.lock);
147 static void cpu_hotplug_done(void)
149 cpu_hotplug.active_writer = NULL;
150 mutex_unlock(&cpu_hotplug.lock);
152 /* Need to know about CPUs going up/down? */
153 int __ref register_cpu_notifier(struct notifier_block *nb)
156 cpu_maps_update_begin();
157 ret = raw_notifier_chain_register(&cpu_chain, nb);
158 cpu_maps_update_done();
162 #ifdef CONFIG_HOTPLUG_CPU
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 &&
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 raw_notifier_call_chain(&cpu_chain, CPU_DYING | param->mod,
210 /* Force idle task to run as soon as we yield: it should
211 immediately notice cpu is offline and die quickly. */
216 /* Requires cpu_add_remove_lock to be held */
217 static int __ref _cpu_down(unsigned int cpu, int tasks_frozen)
219 int err, nr_calls = 0;
220 cpumask_t old_allowed, tmp;
221 void *hcpu = (void *)(long)cpu;
222 unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
223 struct take_cpu_down_param tcd_param = {
228 if (num_online_cpus() == 1)
231 if (!cpu_online(cpu))
235 err = __raw_notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE | mod,
236 hcpu, -1, &nr_calls);
237 if (err == NOTIFY_BAD) {
239 __raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED | mod,
240 hcpu, nr_calls, NULL);
241 printk("%s: attempt to take down CPU %u failed\n",
247 /* Ensure that we are not runnable on dying cpu */
248 old_allowed = current->cpus_allowed;
251 set_cpus_allowed_ptr(current, &tmp);
252 tmp = cpumask_of_cpu(cpu);
254 err = __stop_machine(take_cpu_down, &tcd_param, &tmp);
256 /* CPU didn't die: tell everyone. Can't complain. */
257 if (raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED | mod,
263 BUG_ON(cpu_online(cpu));
265 /* Wait for it to sleep (leaving idle task). */
266 while (!idle_cpu(cpu))
269 /* This actually kills the CPU. */
272 /* CPU is completely dead: tell everyone. Too late to complain. */
273 if (raw_notifier_call_chain(&cpu_chain, CPU_DEAD | mod,
277 check_for_tasks(cpu);
280 set_cpus_allowed_ptr(current, &old_allowed);
284 if (raw_notifier_call_chain(&cpu_chain, CPU_POST_DEAD | mod,
291 int __ref cpu_down(unsigned int cpu)
295 cpu_maps_update_begin();
297 if (cpu_hotplug_disabled) {
302 cpu_clear(cpu, cpu_active_map);
305 * Make sure the all cpus did the reschedule and are not
306 * using stale version of the cpu_active_map.
307 * This is not strictly necessary becuase stop_machine()
308 * that we run down the line already provides the required
309 * synchronization. But it's really a side effect and we do not
310 * want to depend on the innards of the stop_machine here.
314 err = _cpu_down(cpu, 0);
317 cpu_set(cpu, cpu_active_map);
320 cpu_maps_update_done();
323 EXPORT_SYMBOL(cpu_down);
324 #endif /*CONFIG_HOTPLUG_CPU*/
326 /* Requires cpu_add_remove_lock to be held */
327 static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen)
329 int ret, nr_calls = 0;
330 void *hcpu = (void *)(long)cpu;
331 unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
333 if (cpu_online(cpu) || !cpu_present(cpu))
337 ret = __raw_notifier_call_chain(&cpu_chain, CPU_UP_PREPARE | mod, hcpu,
339 if (ret == NOTIFY_BAD) {
341 printk("%s: attempt to bring up CPU %u failed\n",
347 /* Arch-specific enabling code. */
351 BUG_ON(!cpu_online(cpu));
353 cpu_set(cpu, cpu_active_map);
355 /* Now call notifier in preparation. */
356 raw_notifier_call_chain(&cpu_chain, CPU_ONLINE | mod, hcpu);
360 __raw_notifier_call_chain(&cpu_chain,
361 CPU_UP_CANCELED | mod, hcpu, nr_calls, NULL);
367 int __cpuinit cpu_up(unsigned int cpu)
370 if (!cpu_isset(cpu, cpu_possible_map)) {
371 printk(KERN_ERR "can't online cpu %d because it is not "
372 "configured as may-hotadd at boot time\n", cpu);
373 #if defined(CONFIG_IA64) || defined(CONFIG_X86_64)
374 printk(KERN_ERR "please check additional_cpus= boot "
380 cpu_maps_update_begin();
382 if (cpu_hotplug_disabled) {
387 err = _cpu_up(cpu, 0);
390 cpu_maps_update_done();
394 #ifdef CONFIG_PM_SLEEP_SMP
395 static cpumask_t frozen_cpus;
397 int disable_nonboot_cpus(void)
399 int cpu, first_cpu, error = 0;
401 cpu_maps_update_begin();
402 first_cpu = first_cpu(cpu_online_map);
403 /* We take down all of the non-boot CPUs in one shot to avoid races
404 * with the userspace trying to use the CPU hotplug at the same time
406 cpus_clear(frozen_cpus);
407 printk("Disabling non-boot CPUs ...\n");
408 for_each_online_cpu(cpu) {
409 if (cpu == first_cpu)
411 error = _cpu_down(cpu, 1);
413 cpu_set(cpu, frozen_cpus);
414 printk("CPU%d is down\n", cpu);
416 printk(KERN_ERR "Error taking CPU%d down: %d\n",
422 BUG_ON(num_online_cpus() > 1);
423 /* Make sure the CPUs won't be enabled by someone else */
424 cpu_hotplug_disabled = 1;
426 printk(KERN_ERR "Non-boot CPUs are not disabled\n");
428 cpu_maps_update_done();
432 void __ref enable_nonboot_cpus(void)
436 /* Allow everyone to use the CPU hotplug again */
437 cpu_maps_update_begin();
438 cpu_hotplug_disabled = 0;
439 if (cpus_empty(frozen_cpus))
442 printk("Enabling non-boot CPUs ...\n");
443 for_each_cpu_mask_nr(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);
451 cpus_clear(frozen_cpus);
453 cpu_maps_update_done();
455 #endif /* CONFIG_PM_SLEEP_SMP */
458 * notify_cpu_starting(cpu) - call the CPU_STARTING notifiers
459 * @cpu: cpu that just started
461 * This function calls the cpu_chain notifiers with CPU_STARTING.
462 * It must be called by the arch code on the new cpu, before the new cpu
463 * enables interrupts and before the "boot" cpu returns from __cpu_up().
465 void notify_cpu_starting(unsigned int cpu)
467 unsigned long val = CPU_STARTING;
469 #ifdef CONFIG_PM_SLEEP_SMP
470 if (cpu_isset(cpu, frozen_cpus))
471 val = CPU_STARTING_FROZEN;
472 #endif /* CONFIG_PM_SLEEP_SMP */
473 raw_notifier_call_chain(&cpu_chain, val, (void *)(long)cpu);
476 #endif /* CONFIG_SMP */
479 * cpu_bit_bitmap[] is a special, "compressed" data structure that
480 * represents all NR_CPUS bits binary values of 1<<nr.
482 * It is used by cpumask_of_cpu() to get a constant address to a CPU
483 * mask value that has a single bit set only.
486 /* cpu_bit_bitmap[0] is empty - so we can back into it */
487 #define MASK_DECLARE_1(x) [x+1][0] = 1UL << (x)
488 #define MASK_DECLARE_2(x) MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
489 #define MASK_DECLARE_4(x) MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
490 #define MASK_DECLARE_8(x) MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
492 const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
494 MASK_DECLARE_8(0), MASK_DECLARE_8(8),
495 MASK_DECLARE_8(16), MASK_DECLARE_8(24),
496 #if BITS_PER_LONG > 32
497 MASK_DECLARE_8(32), MASK_DECLARE_8(40),
498 MASK_DECLARE_8(48), MASK_DECLARE_8(56),
501 EXPORT_SYMBOL_GPL(cpu_bit_bitmap);