[linux.git] / kernel / cpu.c

/* CPU control.
 * (C) 2001, 2002, 2003, 2004 Rusty Russell
 *
 * This code is licenced under the GPL.
 */
#include <linux/proc_fs.h>
#include <linux/smp.h>
#include <linux/init.h>
#include <linux/notifier.h>
#include <linux/sched.h>
#include <linux/unistd.h>
#include <linux/cpu.h>
#include <linux/module.h>
#include <linux/kthread.h>
#include <linux/stop_machine.h>
#include <linux/mutex.h>

/* This protects CPUs going up and down... */
static DEFINE_MUTEX(cpu_add_remove_lock);
static DEFINE_MUTEX(cpu_bitmask_lock);

static __cpuinitdata BLOCKING_NOTIFIER_HEAD(cpu_chain);

#ifdef CONFIG_HOTPLUG_CPU

/* Crappy recursive lock-takers in cpufreq! Complain loudly about idiots */
static struct task_struct *recursive;
static int recursive_depth;

void lock_cpu_hotplug(void)
{
	struct task_struct *tsk = current;

	if (tsk == recursive) {
		static int warnings = 10;
		if (warnings) {
			printk(KERN_ERR "Lukewarm IQ detected in hotplug locking\n");
			WARN_ON(1);
			warnings--;
		}
		recursive_depth++;
		return;
	}
	mutex_lock(&cpu_bitmask_lock);
	recursive = tsk;
}
EXPORT_SYMBOL_GPL(lock_cpu_hotplug);

void unlock_cpu_hotplug(void)
{
	WARN_ON(recursive != current);
	if (recursive_depth) {
		recursive_depth--;
		return;
	}
	mutex_unlock(&cpu_bitmask_lock);
	recursive = NULL;
}
EXPORT_SYMBOL_GPL(unlock_cpu_hotplug);

#endif	/* CONFIG_HOTPLUG_CPU */

/* Need to know about CPUs going up/down? */
int __cpuinit register_cpu_notifier(struct notifier_block *nb)
{
	return blocking_notifier_chain_register(&cpu_chain, nb);
}

#ifdef CONFIG_HOTPLUG_CPU

EXPORT_SYMBOL(register_cpu_notifier);

void unregister_cpu_notifier(struct notifier_block *nb)
{
	blocking_notifier_chain_unregister(&cpu_chain, nb);
}
EXPORT_SYMBOL(unregister_cpu_notifier);

static inline void check_for_tasks(int cpu)
{
	struct task_struct *p;

	write_lock_irq(&tasklist_lock);
	for_each_process(p) {
		if (task_cpu(p) == cpu &&
		    (!cputime_eq(p->utime, cputime_zero) ||
		     !cputime_eq(p->stime, cputime_zero)))
			printk(KERN_WARNING "Task %s (pid = %d) is on cpu %d\
				(state = %ld, flags = %lx) \n",
				 p->comm, p->pid, cpu, p->state, p->flags);
	}
	write_unlock_irq(&tasklist_lock);
}

/* Take this CPU down. */
static int take_cpu_down(void *unused)
{
	int err;

	/* Ensure this CPU doesn't handle any more interrupts. */
	err = __cpu_disable();
	if (err < 0)
		return err;

	/* Force idle task to run as soon as we yield: it should
	   immediately notice cpu is offline and die quickly. */
	sched_idle_next();
	return 0;
}

int cpu_down(unsigned int cpu)
{
	int err;
	struct task_struct *p;
	cpumask_t old_allowed, tmp;

	mutex_lock(&cpu_add_remove_lock);
	if (num_online_cpus() == 1) {
		err = -EBUSY;
		goto out;
	}

	if (!cpu_online(cpu)) {
		err = -EINVAL;
		goto out;
	}

	err = blocking_notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE,
						(void *)(long)cpu);
	if (err == NOTIFY_BAD) {
		printk("%s: attempt to take down CPU %u failed\n",
				__FUNCTION__, cpu);
		err = -EINVAL;
		goto out;
	}

	/* Ensure that we are not runnable on dying cpu */
	old_allowed = current->cpus_allowed;
	tmp = CPU_MASK_ALL;
	cpu_clear(cpu, tmp);
	set_cpus_allowed(current, tmp);

	mutex_lock(&cpu_bitmask_lock);
	p = __stop_machine_run(take_cpu_down, NULL, cpu);
	mutex_unlock(&cpu_bitmask_lock);

	if (IS_ERR(p)) {
		/* CPU didn't die: tell everyone.  Can't complain. */
		if (blocking_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED,
				(void *)(long)cpu) == NOTIFY_BAD)
			BUG();

		err = PTR_ERR(p);
		goto out_allowed;
	}

	if (cpu_online(cpu))
		goto out_thread;

	/* Wait for it to sleep (leaving idle task). */
	while (!idle_cpu(cpu))
		yield();

	/* This actually kills the CPU. */
	__cpu_die(cpu);

	/* Move it here so it can run. */
	kthread_bind(p, get_cpu());
	put_cpu();

	/* CPU is completely dead: tell everyone.  Too late to complain. */
	if (blocking_notifier_call_chain(&cpu_chain, CPU_DEAD,
			(void *)(long)cpu) == NOTIFY_BAD)
		BUG();

	check_for_tasks(cpu);

out_thread:
	err = kthread_stop(p);
out_allowed:
	set_cpus_allowed(current, old_allowed);
out:
	mutex_unlock(&cpu_add_remove_lock);
	return err;
}
#endif /*CONFIG_HOTPLUG_CPU*/

int __devinit cpu_up(unsigned int cpu)
{
	int ret;
	void *hcpu = (void *)(long)cpu;

	mutex_lock(&cpu_add_remove_lock);
	if (cpu_online(cpu) || !cpu_present(cpu)) {
		ret = -EINVAL;
		goto out;
	}

	ret = blocking_notifier_call_chain(&cpu_chain, CPU_UP_PREPARE, hcpu);
	if (ret == NOTIFY_BAD) {
		printk("%s: attempt to bring up CPU %u failed\n",
				__FUNCTION__, cpu);
		ret = -EINVAL;
		goto out_notify;
	}

	/* Arch-specific enabling code. */
	mutex_lock(&cpu_bitmask_lock);
	ret = __cpu_up(cpu);
	mutex_unlock(&cpu_bitmask_lock);
	if (ret != 0)
		goto out_notify;
	BUG_ON(!cpu_online(cpu));

	/* Now call notifier in preparation. */
	blocking_notifier_call_chain(&cpu_chain, CPU_ONLINE, hcpu);

out_notify:
	if (ret != 0)
		blocking_notifier_call_chain(&cpu_chain,
				CPU_UP_CANCELED, hcpu);
out:
	mutex_unlock(&cpu_add_remove_lock);
	return ret;
}
Commit	Line	Data
1da177e4 LT	1	/* CPU control.
	2	* (C) 2001, 2002, 2003, 2004 Rusty Russell
	3	*
	4	* This code is licenced under the GPL.
	5	*/
	6	#include <linux/proc_fs.h>
	7	#include <linux/smp.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>
81615b62	16	#include <linux/mutex.h>
1da177e4 LT	17
1da177e4 LT	18	/* This protects CPUs going up and down... */
aa953877 LT	19	static DEFINE_MUTEX(cpu_add_remove_lock);
aa953877 LT	20	static DEFINE_MUTEX(cpu_bitmask_lock);
1da177e4	21
65edc68c	22	static __cpuinitdata BLOCKING_NOTIFIER_HEAD(cpu_chain);
1da177e4	23
a9d9baa1	24	#ifdef CONFIG_HOTPLUG_CPU
90d45d17	25
aa953877 LT	26	/* Crappy recursive lock-takers in cpufreq! Complain loudly about idiots */
	27	static struct task_struct *recursive;
	28	static int recursive_depth;
90d45d17	29
a9d9baa1 AR	30	void lock_cpu_hotplug(void)
a9d9baa1 AR	31	{
aa953877 LT	32	struct task_struct *tsk = current;
	33
	34	if (tsk == recursive) {
	35	static int warnings = 10;
	36	if (warnings) {
	37	printk(KERN_ERR "Lukewarm IQ detected in hotplug locking\n");
	38	WARN_ON(1);
	39	warnings--;
	40	}
	41	recursive_depth++;
	42	return;
	43	}
	44	mutex_lock(&cpu_bitmask_lock);
	45	recursive = tsk;
a9d9baa1 AR	46	}
a9d9baa1 AR	47	EXPORT_SYMBOL_GPL(lock_cpu_hotplug);
90d45d17	48
a9d9baa1 AR	49	void unlock_cpu_hotplug(void)
a9d9baa1 AR	50	{
aa953877 LT	51	WARN_ON(recursive != current);
	52	if (recursive_depth) {
	53	recursive_depth--;
	54	return;
a9d9baa1	55	}
aa953877 LT	56	mutex_unlock(&cpu_bitmask_lock);
aa953877 LT	57	recursive = NULL;
a9d9baa1 AR	58	}
	59	EXPORT_SYMBOL_GPL(unlock_cpu_hotplug);
	60
a9d9baa1	61	#endif /* CONFIG_HOTPLUG_CPU */
90d45d17	62
1da177e4	63	/* Need to know about CPUs going up/down? */
65edc68c	64	int __cpuinit register_cpu_notifier(struct notifier_block *nb)
1da177e4	65	{
e041c683	66	return blocking_notifier_chain_register(&cpu_chain, nb);
1da177e4	67	}
65edc68c CS	68
	69	#ifdef CONFIG_HOTPLUG_CPU
	70
1da177e4 LT	71	EXPORT_SYMBOL(register_cpu_notifier);
	72
	73	void unregister_cpu_notifier(struct notifier_block *nb)
	74	{
e041c683	75	blocking_notifier_chain_unregister(&cpu_chain, nb);
1da177e4 LT	76	}
	77	EXPORT_SYMBOL(unregister_cpu_notifier);
	78
1da177e4 LT	79	static inline void check_for_tasks(int cpu)
	80	{
	81	struct task_struct *p;
	82
	83	write_lock_irq(&tasklist_lock);
	84	for_each_process(p) {
	85	if (task_cpu(p) == cpu &&
	86	(!cputime_eq(p->utime, cputime_zero) \|\|
	87	!cputime_eq(p->stime, cputime_zero)))
	88	printk(KERN_WARNING "Task %s (pid = %d) is on cpu %d\
	89	(state = %ld, flags = %lx) \n",
	90	p->comm, p->pid, cpu, p->state, p->flags);
	91	}
	92	write_unlock_irq(&tasklist_lock);
	93	}
	94
	95	/* Take this CPU down. */
	96	static int take_cpu_down(void *unused)
	97	{
	98	int err;
	99
1da177e4 LT	100	/* Ensure this CPU doesn't handle any more interrupts. */
	101	err = __cpu_disable();
	102	if (err < 0)
f3705136	103	return err;
1da177e4	104
f3705136 ZM	105	/* Force idle task to run as soon as we yield: it should
	106	immediately notice cpu is offline and die quickly. */
	107	sched_idle_next();
	108	return 0;
1da177e4 LT	109	}
	110
	111	int cpu_down(unsigned int cpu)
	112	{
	113	int err;
	114	struct task_struct *p;
	115	cpumask_t old_allowed, tmp;
	116
aa953877	117	mutex_lock(&cpu_add_remove_lock);
1da177e4 LT	118	if (num_online_cpus() == 1) {
	119	err = -EBUSY;
	120	goto out;
	121	}
	122
	123	if (!cpu_online(cpu)) {
	124	err = -EINVAL;
	125	goto out;
	126	}
	127
e041c683	128	err = blocking_notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE,
1da177e4 LT	129	(void *)(long)cpu);
	130	if (err == NOTIFY_BAD) {
	131	printk("%s: attempt to take down CPU %u failed\n",
	132	__FUNCTION__, cpu);
	133	err = -EINVAL;
	134	goto out;
	135	}
	136
	137	/* Ensure that we are not runnable on dying cpu */
	138	old_allowed = current->cpus_allowed;
	139	tmp = CPU_MASK_ALL;
	140	cpu_clear(cpu, tmp);
	141	set_cpus_allowed(current, tmp);
	142
aa953877	143	mutex_lock(&cpu_bitmask_lock);
1da177e4	144	p = __stop_machine_run(take_cpu_down, NULL, cpu);
aa953877 LT	145	mutex_unlock(&cpu_bitmask_lock);
aa953877 LT	146
1da177e4 LT	147	if (IS_ERR(p)) {
1da177e4 LT	148	/* CPU didn't die: tell everyone. Can't complain. */
e041c683	149	if (blocking_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED,
1da177e4 LT	150	(void *)(long)cpu) == NOTIFY_BAD)
	151	BUG();
	152
	153	err = PTR_ERR(p);
	154	goto out_allowed;
	155	}
	156
	157	if (cpu_online(cpu))
	158	goto out_thread;
	159
	160	/* Wait for it to sleep (leaving idle task). */
	161	while (!idle_cpu(cpu))
	162	yield();
	163
	164	/* This actually kills the CPU. */
	165	__cpu_die(cpu);
	166
	167	/* Move it here so it can run. */
	168	kthread_bind(p, get_cpu());
	169	put_cpu();
	170
	171	/* CPU is completely dead: tell everyone. Too late to complain. */
e041c683 AS	172	if (blocking_notifier_call_chain(&cpu_chain, CPU_DEAD,
e041c683 AS	173	(void *)(long)cpu) == NOTIFY_BAD)
1da177e4 LT	174	BUG();
	175
	176	check_for_tasks(cpu);
	177
	178	out_thread:
	179	err = kthread_stop(p);
	180	out_allowed:
	181	set_cpus_allowed(current, old_allowed);
	182	out:
aa953877	183	mutex_unlock(&cpu_add_remove_lock);
1da177e4 LT	184	return err;
	185	}
	186	#endif /CONFIG_HOTPLUG_CPU/
	187
	188	int __devinit cpu_up(unsigned int cpu)
	189	{
	190	int ret;
	191	void hcpu = (void )(long)cpu;
	192
aa953877	193	mutex_lock(&cpu_add_remove_lock);
1da177e4 LT	194	if (cpu_online(cpu) \|\| !cpu_present(cpu)) {
	195	ret = -EINVAL;
	196	goto out;
	197	}
90d45d17	198
e041c683	199	ret = blocking_notifier_call_chain(&cpu_chain, CPU_UP_PREPARE, hcpu);
1da177e4 LT	200	if (ret == NOTIFY_BAD) {
	201	printk("%s: attempt to bring up CPU %u failed\n",
	202	__FUNCTION__, cpu);
	203	ret = -EINVAL;
	204	goto out_notify;
	205	}
	206
	207	/* Arch-specific enabling code. */
aa953877	208	mutex_lock(&cpu_bitmask_lock);
1da177e4	209	ret = __cpu_up(cpu);
aa953877	210	mutex_unlock(&cpu_bitmask_lock);
1da177e4 LT	211	if (ret != 0)
1da177e4 LT	212	goto out_notify;
6978c705	213	BUG_ON(!cpu_online(cpu));
1da177e4 LT	214
1da177e4 LT	215	/* Now call notifier in preparation. */
e041c683	216	blocking_notifier_call_chain(&cpu_chain, CPU_ONLINE, hcpu);
1da177e4 LT	217
	218	out_notify:
	219	if (ret != 0)
e041c683 AS	220	blocking_notifier_call_chain(&cpu_chain,
e041c683 AS	221	CPU_UP_CANCELED, hcpu);
1da177e4	222	out:
aa953877	223	mutex_unlock(&cpu_add_remove_lock);
1da177e4 LT	224	return ret;
1da177e4 LT	225	}