[linux.git] / kernel / freezer.c

/*
 * kernel/freezer.c - Function to freeze a process
 *
 * Originally from kernel/power/process.c
 */

#include <linux/interrupt.h>
#include <linux/suspend.h>
#include <linux/module.h>
#include <linux/syscalls.h>
#include <linux/freezer.h>

/*
 * freezing is complete, mark current process as frozen
 */
static inline void frozen_process(void)
{
	if (!unlikely(current->flags & PF_NOFREEZE)) {
		current->flags |= PF_FROZEN;
		wmb();
	}
	clear_freeze_flag(current);
}

/* Refrigerator is place where frozen processes are stored :-). */
void refrigerator(void)
{
	/* Hmm, should we be allowed to suspend when there are realtime
	   processes around? */
	long save;

	task_lock(current);
	if (freezing(current)) {
		frozen_process();
		task_unlock(current);
	} else {
		task_unlock(current);
		return;
	}
	save = current->state;
	pr_debug("%s entered refrigerator\n", current->comm);

	spin_lock_irq(&current->sighand->siglock);
	recalc_sigpending(); /* We sent fake signal, clean it up */
	spin_unlock_irq(&current->sighand->siglock);

	for (;;) {
		set_current_state(TASK_UNINTERRUPTIBLE);
		if (!frozen(current))
			break;
		schedule();
	}
	pr_debug("%s left refrigerator\n", current->comm);
	__set_current_state(save);
}
EXPORT_SYMBOL(refrigerator);

static void fake_signal_wake_up(struct task_struct *p)
{
	unsigned long flags;

	spin_lock_irqsave(&p->sighand->siglock, flags);
	signal_wake_up(p, 0);
	spin_unlock_irqrestore(&p->sighand->siglock, flags);
}

/**
 *	freeze_task - send a freeze request to given task
 *	@p: task to send the request to
 *	@sig_only: if set, the request will only be sent if the task has the
 *		PF_FREEZER_NOSIG flag unset
 *	Return value: 'false', if @sig_only is set and the task has
 *		PF_FREEZER_NOSIG set or the task is frozen, 'true', otherwise
 *
 *	The freeze request is sent by setting the tasks's TIF_FREEZE flag and
 *	either sending a fake signal to it or waking it up, depending on whether
 *	or not it has PF_FREEZER_NOSIG set.  If @sig_only is set and the task
 *	has PF_FREEZER_NOSIG set (ie. it is a typical kernel thread), its
 *	TIF_FREEZE flag will not be set.
 */
bool freeze_task(struct task_struct *p, bool sig_only)
{
	/*
	 * We first check if the task is freezing and next if it has already
	 * been frozen to avoid the race with frozen_process() which first marks
	 * the task as frozen and next clears its TIF_FREEZE.
	 */
	if (!freezing(p)) {
		rmb();
		if (frozen(p))
			return false;

		if (!sig_only || should_send_signal(p))
			set_freeze_flag(p);
		else
			return false;
	}

	if (should_send_signal(p)) {
		if (!signal_pending(p))
			fake_signal_wake_up(p);
	} else if (sig_only) {
		return false;
	} else {
		wake_up_state(p, TASK_INTERRUPTIBLE);
	}

	return true;
}

void cancel_freezing(struct task_struct *p)
{
	unsigned long flags;

	if (freezing(p)) {
		pr_debug("  clean up: %s\n", p->comm);
		clear_freeze_flag(p);
		spin_lock_irqsave(&p->sighand->siglock, flags);
		recalc_sigpending_and_wake(p);
		spin_unlock_irqrestore(&p->sighand->siglock, flags);
	}
}

static int __thaw_process(struct task_struct *p)
{
	if (frozen(p)) {
		p->flags &= ~PF_FROZEN;
		return 1;
	}
	clear_freeze_flag(p);
	return 0;
}

/*
 * Wake up a frozen process
 *
 * task_lock() is needed to prevent the race with refrigerator() which may
 * occur if the freezing of tasks fails.  Namely, without the lock, if the
 * freezing of tasks failed, thaw_tasks() might have run before a task in
 * refrigerator() could call frozen_process(), in which case the task would be
 * frozen and no one would thaw it.
 */
int thaw_process(struct task_struct *p)
{
	task_lock(p);
	if (__thaw_process(p) == 1) {
		task_unlock(p);
		wake_up_process(p);
		return 1;
	}
	task_unlock(p);
	return 0;
}
EXPORT_SYMBOL(thaw_process);
Commit	Line	Data
8174f150 MH	1	/*
	2	* kernel/freezer.c - Function to freeze a process
	3	*
	4	* Originally from kernel/power/process.c
	5	*/
	6
	7	#include <linux/interrupt.h>
	8	#include <linux/suspend.h>
	9	#include <linux/module.h>
	10	#include <linux/syscalls.h>
	11	#include <linux/freezer.h>
	12
	13	/*
	14	* freezing is complete, mark current process as frozen
	15	*/
	16	static inline void frozen_process(void)
	17	{
	18	if (!unlikely(current->flags & PF_NOFREEZE)) {
	19	current->flags \|= PF_FROZEN;
	20	wmb();
	21	}
	22	clear_freeze_flag(current);
	23	}
	24
	25	/* Refrigerator is place where frozen processes are stored :-). */
	26	void refrigerator(void)
	27	{
	28	/* Hmm, should we be allowed to suspend when there are realtime
	29	processes around? */
	30	long save;
	31
	32	task_lock(current);
	33	if (freezing(current)) {
	34	frozen_process();
	35	task_unlock(current);
	36	} else {
	37	task_unlock(current);
	38	return;
	39	}
	40	save = current->state;
	41	pr_debug("%s entered refrigerator\n", current->comm);
	42
	43	spin_lock_irq(&current->sighand->siglock);
	44	recalc_sigpending(); /* We sent fake signal, clean it up */
	45	spin_unlock_irq(&current->sighand->siglock);
	46
	47	for (;;) {
	48	set_current_state(TASK_UNINTERRUPTIBLE);
	49	if (!frozen(current))
	50	break;
	51	schedule();
	52	}
	53	pr_debug("%s left refrigerator\n", current->comm);
	54	__set_current_state(save);
	55	}
	56	EXPORT_SYMBOL(refrigerator);
	57
	58	static void fake_signal_wake_up(struct task_struct *p)
	59	{
	60	unsigned long flags;
	61
	62	spin_lock_irqsave(&p->sighand->siglock, flags);
	63	signal_wake_up(p, 0);
	64	spin_unlock_irqrestore(&p->sighand->siglock, flags);
65	}
66
67	/**
68	* freeze_task - send a freeze request to given task
69	* @p: task to send the request to
70	* @sig_only: if set, the request will only be sent if the task has the
71	* PF_FREEZER_NOSIG flag unset
72	* Return value: 'false', if @sig_only is set and the task has
73	* PF_FREEZER_NOSIG set or the task is frozen, 'true', otherwise
74	*
75	* The freeze request is sent by setting the tasks's TIF_FREEZE flag and
76	* either sending a fake signal to it or waking it up, depending on whether
77	* or not it has PF_FREEZER_NOSIG set. If @sig_only is set and the task
78	* has PF_FREEZER_NOSIG set (ie. it is a typical kernel thread), its
79	* TIF_FREEZE flag will not be set.
80	*/
81	bool freeze_task(struct task_struct *p, bool sig_only)
82	{
83	/*
84	* We first check if the task is freezing and next if it has already
85	* been frozen to avoid the race with frozen_process() which first marks
86	* the task as frozen and next clears its TIF_FREEZE.
87	*/
88	if (!freezing(p)) {
89	rmb();
90	if (frozen(p))
91	return false;
92
93	if (!sig_only \|\| should_send_signal(p))
94	set_freeze_flag(p);
95	else
96	return false;
97	}
98
99	if (should_send_signal(p)) {
100	if (!signal_pending(p))
101	fake_signal_wake_up(p);
102	} else if (sig_only) {
103	return false;
104	} else {
105	wake_up_state(p, TASK_INTERRUPTIBLE);
106	}
107
108	return true;
109	}
110
111	void cancel_freezing(struct task_struct *p)
112	{
113	unsigned long flags;
114
115	if (freezing(p)) {
116	pr_debug(" clean up: %s\n", p->comm);
117	clear_freeze_flag(p);
118	spin_lock_irqsave(&p->sighand->siglock, flags);
119	recalc_sigpending_and_wake(p);
120	spin_unlock_irqrestore(&p->sighand->siglock, flags);
121	}
122	}
dc52ddc0	123
00c2e63c	124	static int __thaw_process(struct task_struct *p)
dc52ddc0 MH	125	{
	126	if (frozen(p)) {
	127	p->flags &= ~PF_FROZEN;
	128	return 1;
	129	}
	130	clear_freeze_flag(p);
	131	return 0;
	132	}
	133
00c2e63c LZ	134	/*
	135	* Wake up a frozen process
	136	*
	137	* task_lock() is needed to prevent the race with refrigerator() which may
	138	* occur if the freezing of tasks fails. Namely, without the lock, if the
	139	* freezing of tasks failed, thaw_tasks() might have run before a task in
	140	* refrigerator() could call frozen_process(), in which case the task would be
	141	* frozen and no one would thaw it.
	142	*/
dc52ddc0 MH	143	int thaw_process(struct task_struct *p)
	144	{
	145	task_lock(p);
	146	if (__thaw_process(p) == 1) {
	147	task_unlock(p);
	148	wake_up_process(p);
	149	return 1;
	150	}
	151	task_unlock(p);
	152	return 0;
	153	}
	154	EXPORT_SYMBOL(thaw_process);