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>
18 /* This protects CPUs going up and down... */
19 static DEFINE_MUTEX(cpu_add_remove_lock);
20 static DEFINE_MUTEX(cpu_bitmask_lock);
22 static __cpuinitdata RAW_NOTIFIER_HEAD(cpu_chain);
24 /* If set, cpu_up and cpu_down will return -EBUSY and do nothing.
25 * Should always be manipulated under cpu_add_remove_lock
27 static int cpu_hotplug_disabled;
29 #ifdef CONFIG_HOTPLUG_CPU
31 /* Crappy recursive lock-takers in cpufreq! Complain loudly about idiots */
32 static struct task_struct *recursive;
33 static int recursive_depth;
35 void lock_cpu_hotplug(void)
37 struct task_struct *tsk = current;
39 if (tsk == recursive) {
40 static int warnings = 10;
42 printk(KERN_ERR "Lukewarm IQ detected in hotplug locking\n");
49 mutex_lock(&cpu_bitmask_lock);
52 EXPORT_SYMBOL_GPL(lock_cpu_hotplug);
54 void unlock_cpu_hotplug(void)
56 WARN_ON(recursive != current);
57 if (recursive_depth) {
62 mutex_unlock(&cpu_bitmask_lock);
64 EXPORT_SYMBOL_GPL(unlock_cpu_hotplug);
66 #endif /* CONFIG_HOTPLUG_CPU */
68 /* Need to know about CPUs going up/down? */
69 int __cpuinit register_cpu_notifier(struct notifier_block *nb)
72 mutex_lock(&cpu_add_remove_lock);
73 ret = raw_notifier_chain_register(&cpu_chain, nb);
74 mutex_unlock(&cpu_add_remove_lock);
78 #ifdef CONFIG_HOTPLUG_CPU
80 EXPORT_SYMBOL(register_cpu_notifier);
82 void unregister_cpu_notifier(struct notifier_block *nb)
84 mutex_lock(&cpu_add_remove_lock);
85 raw_notifier_chain_unregister(&cpu_chain, nb);
86 mutex_unlock(&cpu_add_remove_lock);
88 EXPORT_SYMBOL(unregister_cpu_notifier);
90 static inline void check_for_tasks(int cpu)
92 struct task_struct *p;
94 write_lock_irq(&tasklist_lock);
96 if (task_cpu(p) == cpu &&
97 (!cputime_eq(p->utime, cputime_zero) ||
98 !cputime_eq(p->stime, cputime_zero)))
99 printk(KERN_WARNING "Task %s (pid = %d) is on cpu %d\
100 (state = %ld, flags = %x) \n",
101 p->comm, p->pid, cpu, p->state, p->flags);
103 write_unlock_irq(&tasklist_lock);
106 /* Take this CPU down. */
107 static int take_cpu_down(void *unused)
111 /* Ensure this CPU doesn't handle any more interrupts. */
112 err = __cpu_disable();
116 /* Force idle task to run as soon as we yield: it should
117 immediately notice cpu is offline and die quickly. */
122 /* Requires cpu_add_remove_lock to be held */
123 static int _cpu_down(unsigned int cpu, int tasks_frozen)
125 int err, nr_calls = 0;
126 struct task_struct *p;
127 cpumask_t old_allowed, tmp;
128 void *hcpu = (void *)(long)cpu;
129 unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
131 if (num_online_cpus() == 1)
134 if (!cpu_online(cpu))
137 raw_notifier_call_chain(&cpu_chain, CPU_LOCK_ACQUIRE, hcpu);
138 err = __raw_notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE | mod,
139 hcpu, -1, &nr_calls);
140 if (err == NOTIFY_BAD) {
141 __raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED | mod,
142 hcpu, nr_calls, NULL);
143 printk("%s: attempt to take down CPU %u failed\n",
149 /* Ensure that we are not runnable on dying cpu */
150 old_allowed = current->cpus_allowed;
153 set_cpus_allowed(current, tmp);
155 mutex_lock(&cpu_bitmask_lock);
156 p = __stop_machine_run(take_cpu_down, NULL, cpu);
157 mutex_unlock(&cpu_bitmask_lock);
159 if (IS_ERR(p) || cpu_online(cpu)) {
160 /* CPU didn't die: tell everyone. Can't complain. */
161 if (raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED | mod,
172 /* Wait for it to sleep (leaving idle task). */
173 while (!idle_cpu(cpu))
176 /* This actually kills the CPU. */
179 /* CPU is completely dead: tell everyone. Too late to complain. */
180 if (raw_notifier_call_chain(&cpu_chain, CPU_DEAD | mod,
184 check_for_tasks(cpu);
187 err = kthread_stop(p);
189 set_cpus_allowed(current, old_allowed);
191 raw_notifier_call_chain(&cpu_chain, CPU_LOCK_RELEASE, hcpu);
195 int cpu_down(unsigned int cpu)
199 mutex_lock(&cpu_add_remove_lock);
200 if (cpu_hotplug_disabled)
203 err = _cpu_down(cpu, 0);
205 mutex_unlock(&cpu_add_remove_lock);
208 #endif /*CONFIG_HOTPLUG_CPU*/
210 /* Requires cpu_add_remove_lock to be held */
211 static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen)
213 int ret, nr_calls = 0;
214 void *hcpu = (void *)(long)cpu;
215 unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
217 if (cpu_online(cpu) || !cpu_present(cpu))
220 raw_notifier_call_chain(&cpu_chain, CPU_LOCK_ACQUIRE, hcpu);
221 ret = __raw_notifier_call_chain(&cpu_chain, CPU_UP_PREPARE | mod, hcpu,
223 if (ret == NOTIFY_BAD) {
224 printk("%s: attempt to bring up CPU %u failed\n",
230 /* Arch-specific enabling code. */
231 mutex_lock(&cpu_bitmask_lock);
233 mutex_unlock(&cpu_bitmask_lock);
236 BUG_ON(!cpu_online(cpu));
238 /* Now call notifier in preparation. */
239 raw_notifier_call_chain(&cpu_chain, CPU_ONLINE | mod, hcpu);
243 __raw_notifier_call_chain(&cpu_chain,
244 CPU_UP_CANCELED | mod, hcpu, nr_calls, NULL);
245 raw_notifier_call_chain(&cpu_chain, CPU_LOCK_RELEASE, hcpu);
250 int __cpuinit cpu_up(unsigned int cpu)
254 mutex_lock(&cpu_add_remove_lock);
255 if (cpu_hotplug_disabled)
258 err = _cpu_up(cpu, 0);
260 mutex_unlock(&cpu_add_remove_lock);
264 #ifdef CONFIG_SUSPEND_SMP
265 /* Needed to prevent the microcode driver from requesting firmware in its CPU
266 * hotplug notifier during the suspend/resume.
268 int suspend_cpu_hotplug;
269 EXPORT_SYMBOL(suspend_cpu_hotplug);
271 static cpumask_t frozen_cpus;
273 int disable_nonboot_cpus(void)
275 int cpu, first_cpu, error = 0;
277 mutex_lock(&cpu_add_remove_lock);
278 suspend_cpu_hotplug = 1;
279 first_cpu = first_cpu(cpu_online_map);
280 /* We take down all of the non-boot CPUs in one shot to avoid races
281 * with the userspace trying to use the CPU hotplug at the same time
283 cpus_clear(frozen_cpus);
284 printk("Disabling non-boot CPUs ...\n");
285 for_each_online_cpu(cpu) {
286 if (cpu == first_cpu)
288 error = _cpu_down(cpu, 1);
290 cpu_set(cpu, frozen_cpus);
291 printk("CPU%d is down\n", cpu);
293 printk(KERN_ERR "Error taking CPU%d down: %d\n",
299 BUG_ON(num_online_cpus() > 1);
300 /* Make sure the CPUs won't be enabled by someone else */
301 cpu_hotplug_disabled = 1;
303 printk(KERN_ERR "Non-boot CPUs are not disabled\n");
305 suspend_cpu_hotplug = 0;
306 mutex_unlock(&cpu_add_remove_lock);
310 void enable_nonboot_cpus(void)
314 /* Allow everyone to use the CPU hotplug again */
315 mutex_lock(&cpu_add_remove_lock);
316 cpu_hotplug_disabled = 0;
317 if (cpus_empty(frozen_cpus))
320 suspend_cpu_hotplug = 1;
321 printk("Enabling non-boot CPUs ...\n");
322 for_each_cpu_mask(cpu, frozen_cpus) {
323 error = _cpu_up(cpu, 1);
325 printk("CPU%d is up\n", cpu);
328 printk(KERN_WARNING "Error taking CPU%d up: %d\n", cpu, error);
330 cpus_clear(frozen_cpus);
331 suspend_cpu_hotplug = 0;
333 mutex_unlock(&cpu_add_remove_lock);