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)
125 int err, nr_calls = 0;
126 struct task_struct *p;
127 cpumask_t old_allowed, tmp;
128 void *hcpu = (void *)(long)cpu;
130 if (num_online_cpus() == 1)
133 if (!cpu_online(cpu))
136 raw_notifier_call_chain(&cpu_chain, CPU_LOCK_ACQUIRE, hcpu);
137 err = __raw_notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE,
138 hcpu, -1, &nr_calls);
139 if (err == NOTIFY_BAD) {
140 __raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED, hcpu,
142 printk("%s: attempt to take down CPU %u failed\n",
148 /* Ensure that we are not runnable on dying cpu */
149 old_allowed = current->cpus_allowed;
152 set_cpus_allowed(current, tmp);
154 mutex_lock(&cpu_bitmask_lock);
155 p = __stop_machine_run(take_cpu_down, NULL, cpu);
156 mutex_unlock(&cpu_bitmask_lock);
158 if (IS_ERR(p) || cpu_online(cpu)) {
159 /* CPU didn't die: tell everyone. Can't complain. */
160 if (raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED,
171 /* Wait for it to sleep (leaving idle task). */
172 while (!idle_cpu(cpu))
175 /* This actually kills the CPU. */
178 /* CPU is completely dead: tell everyone. Too late to complain. */
179 if (raw_notifier_call_chain(&cpu_chain, CPU_DEAD, hcpu) == NOTIFY_BAD)
182 check_for_tasks(cpu);
185 err = kthread_stop(p);
187 set_cpus_allowed(current, old_allowed);
189 raw_notifier_call_chain(&cpu_chain, CPU_LOCK_RELEASE,
194 int cpu_down(unsigned int cpu)
198 mutex_lock(&cpu_add_remove_lock);
199 if (cpu_hotplug_disabled)
202 err = _cpu_down(cpu);
204 mutex_unlock(&cpu_add_remove_lock);
207 #endif /*CONFIG_HOTPLUG_CPU*/
209 /* Requires cpu_add_remove_lock to be held */
210 static int __cpuinit _cpu_up(unsigned int cpu)
212 int ret, nr_calls = 0;
213 void *hcpu = (void *)(long)cpu;
215 if (cpu_online(cpu) || !cpu_present(cpu))
218 raw_notifier_call_chain(&cpu_chain, CPU_LOCK_ACQUIRE, hcpu);
219 ret = __raw_notifier_call_chain(&cpu_chain, CPU_UP_PREPARE, hcpu,
221 if (ret == NOTIFY_BAD) {
222 printk("%s: attempt to bring up CPU %u failed\n",
228 /* Arch-specific enabling code. */
229 mutex_lock(&cpu_bitmask_lock);
231 mutex_unlock(&cpu_bitmask_lock);
234 BUG_ON(!cpu_online(cpu));
236 /* Now call notifier in preparation. */
237 raw_notifier_call_chain(&cpu_chain, CPU_ONLINE, hcpu);
241 __raw_notifier_call_chain(&cpu_chain,
242 CPU_UP_CANCELED, hcpu, nr_calls, NULL);
243 raw_notifier_call_chain(&cpu_chain, CPU_LOCK_RELEASE, hcpu);
248 int __cpuinit cpu_up(unsigned int cpu)
252 mutex_lock(&cpu_add_remove_lock);
253 if (cpu_hotplug_disabled)
258 mutex_unlock(&cpu_add_remove_lock);
262 #ifdef CONFIG_SUSPEND_SMP
263 /* Needed to prevent the microcode driver from requesting firmware in its CPU
264 * hotplug notifier during the suspend/resume.
266 int suspend_cpu_hotplug;
267 EXPORT_SYMBOL(suspend_cpu_hotplug);
269 static cpumask_t frozen_cpus;
271 int disable_nonboot_cpus(void)
273 int cpu, first_cpu, error = 0;
275 mutex_lock(&cpu_add_remove_lock);
276 suspend_cpu_hotplug = 1;
277 first_cpu = first_cpu(cpu_online_map);
278 /* We take down all of the non-boot CPUs in one shot to avoid races
279 * with the userspace trying to use the CPU hotplug at the same time
281 cpus_clear(frozen_cpus);
282 printk("Disabling non-boot CPUs ...\n");
283 for_each_online_cpu(cpu) {
284 if (cpu == first_cpu)
286 error = _cpu_down(cpu);
288 cpu_set(cpu, frozen_cpus);
289 printk("CPU%d is down\n", cpu);
291 printk(KERN_ERR "Error taking CPU%d down: %d\n",
297 BUG_ON(num_online_cpus() > 1);
298 /* Make sure the CPUs won't be enabled by someone else */
299 cpu_hotplug_disabled = 1;
301 printk(KERN_ERR "Non-boot CPUs are not disabled\n");
303 suspend_cpu_hotplug = 0;
304 mutex_unlock(&cpu_add_remove_lock);
308 void enable_nonboot_cpus(void)
312 /* Allow everyone to use the CPU hotplug again */
313 mutex_lock(&cpu_add_remove_lock);
314 cpu_hotplug_disabled = 0;
315 if (cpus_empty(frozen_cpus))
318 suspend_cpu_hotplug = 1;
319 printk("Enabling non-boot CPUs ...\n");
320 for_each_cpu_mask(cpu, frozen_cpus) {
321 error = _cpu_up(cpu);
323 printk("CPU%d is up\n", cpu);
326 printk(KERN_WARNING "Error taking CPU%d up: %d\n", cpu, error);
328 cpus_clear(frozen_cpus);
329 suspend_cpu_hotplug = 0;
331 mutex_unlock(&cpu_add_remove_lock);