[GitHub/mt8127/android_kernel_alcatel_ttab.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/export.h>
#include <linux/syscalls.h>
#include <linux/freezer.h>
#include <linux/kthread.h>

/* total number of freezing conditions in effect */
atomic_t system_freezing_cnt = ATOMIC_INIT(0);
EXPORT_SYMBOL(system_freezing_cnt);

/* indicate whether PM freezing is in effect, protected by pm_mutex */
bool pm_freezing;
bool pm_nosig_freezing;

/*
 * Temporary export for the deadlock workaround in ata_scsi_hotplug().
 * Remove once the hack becomes unnecessary.
 */
EXPORT_SYMBOL_GPL(pm_freezing);

/* protects freezing and frozen transitions */
static DEFINE_SPINLOCK(freezer_lock);

/**
 * freezing_slow_path - slow path for testing whether a task needs to be frozen
 * @p: task to be tested
 *
 * This function is called by freezing() if system_freezing_cnt isn't zero
 * and tests whether @p needs to enter and stay in frozen state.  Can be
 * called under any context.  The freezers are responsible for ensuring the
 * target tasks see the updated state.
 */
bool freezing_slow_path(struct task_struct *p)
{
	if (p->flags & PF_NOFREEZE)
		return false;

	if (test_thread_flag(TIF_MEMDIE))
		return false;

	if (pm_nosig_freezing || cgroup_freezing(p))
		return true;

	if (pm_freezing && !(p->flags & PF_KTHREAD))
		return true;

	return false;
}
EXPORT_SYMBOL(freezing_slow_path);

/* Refrigerator is place where frozen processes are stored :-). */
bool __refrigerator(bool check_kthr_stop)
{
	/* Hmm, should we be allowed to suspend when there are realtime
	   processes around? */
	bool was_frozen = false;
	long save = current->state;

	pr_debug("%s entered refrigerator\n", current->comm);

	for (;;) {
		set_current_state(TASK_UNINTERRUPTIBLE);

		spin_lock_irq(&freezer_lock);
		current->flags |= PF_FROZEN;
		if (!freezing(current) ||
		    (check_kthr_stop && kthread_should_stop()))
			current->flags &= ~PF_FROZEN;
		spin_unlock_irq(&freezer_lock);

		if (!(current->flags & PF_FROZEN))
			break;
		was_frozen = true;
		schedule();
	}

	pr_debug("%s left refrigerator\n", current->comm);

	/*
	 * Restore saved task state before returning.  The mb'd version
	 * needs to be used; otherwise, it might silently break
	 * synchronization which depends on ordered task state change.
	 */
	set_current_state(save);

	return was_frozen;
}
EXPORT_SYMBOL(__refrigerator);

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

	if (lock_task_sighand(p, &flags)) {
		signal_wake_up(p, 0);
		unlock_task_sighand(p, &flags);
	}
}

/**
 * freeze_task - send a freeze request to given task
 * @p: task to send the request to
 *
 * If @p is freezing, the freeze request is sent either by sending a fake
 * signal (if it's not a kernel thread) or waking it up (if it's a kernel
 * thread).
 *
 * RETURNS:
 * %false, if @p is not freezing or already frozen; %true, otherwise
 */
bool freeze_task(struct task_struct *p)
{
	unsigned long flags;

	/*
	 * This check can race with freezer_do_not_count, but worst case that
	 * will result in an extra wakeup being sent to the task.  It does not
	 * race with freezer_count(), the barriers in freezer_count() and
	 * freezer_should_skip() ensure that either freezer_count() sees
	 * freezing == true in try_to_freeze() and freezes, or
	 * freezer_should_skip() sees !PF_FREEZE_SKIP and freezes the task
	 * normally.
	 */
	if (freezer_should_skip(p))
		return false;

	spin_lock_irqsave(&freezer_lock, flags);
	if (!freezing(p) || frozen(p)) {
		spin_unlock_irqrestore(&freezer_lock, flags);
		return false;
	}

	if (!(p->flags & PF_KTHREAD))
		fake_signal_wake_up(p);
	else
		wake_up_state(p, TASK_INTERRUPTIBLE);

	spin_unlock_irqrestore(&freezer_lock, flags);
	return true;
}

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

	/*
	 * Clear freezing and kick @p if FROZEN.  Clearing is guaranteed to
	 * be visible to @p as waking up implies wmb.  Waking up inside
	 * freezer_lock also prevents wakeups from leaking outside
	 * refrigerator.
	 */
	spin_lock_irqsave(&freezer_lock, flags);
	if (frozen(p))
		wake_up_process(p);
	spin_unlock_irqrestore(&freezer_lock, flags);
}

/**
 * set_freezable - make %current freezable
 *
 * Mark %current freezable and enter refrigerator if necessary.
 */
bool set_freezable(void)
{
	might_sleep();

	/*
	 * Modify flags while holding freezer_lock.  This ensures the
	 * freezer notices that we aren't frozen yet or the freezing
	 * condition is visible to try_to_freeze() below.
	 */
	spin_lock_irq(&freezer_lock);
	current->flags &= ~PF_NOFREEZE;
	spin_unlock_irq(&freezer_lock);

	return try_to_freeze();
}
EXPORT_SYMBOL(set_freezable);
Commit	Line	Data
	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/export.h>
	10	#include <linux/syscalls.h>
	11	#include <linux/freezer.h>
	12	#include <linux/kthread.h>
	13
	14	/* total number of freezing conditions in effect */
	15	atomic_t system_freezing_cnt = ATOMIC_INIT(0);
	16	EXPORT_SYMBOL(system_freezing_cnt);
	17
	18	/* indicate whether PM freezing is in effect, protected by pm_mutex */
	19	bool pm_freezing;
	20	bool pm_nosig_freezing;
	21
	22	/*
	23	* Temporary export for the deadlock workaround in ata_scsi_hotplug().
	24	* Remove once the hack becomes unnecessary.
	25	*/
	26	EXPORT_SYMBOL_GPL(pm_freezing);
	27
	28	/* protects freezing and frozen transitions */
	29	static DEFINE_SPINLOCK(freezer_lock);
	30
	31	/**
	32	* freezing_slow_path - slow path for testing whether a task needs to be frozen
	33	* @p: task to be tested
	34	*
	35	* This function is called by freezing() if system_freezing_cnt isn't zero
	36	* and tests whether @p needs to enter and stay in frozen state. Can be
	37	* called under any context. The freezers are responsible for ensuring the
	38	* target tasks see the updated state.
	39	*/
	40	bool freezing_slow_path(struct task_struct *p)
	41	{
	42	if (p->flags & PF_NOFREEZE)
	43	return false;
	44
	45	if (test_thread_flag(TIF_MEMDIE))
	46	return false;
	47
	48	if (pm_nosig_freezing \|\| cgroup_freezing(p))
	49	return true;
	50
	51	if (pm_freezing && !(p->flags & PF_KTHREAD))
	52	return true;
	53
	54	return false;
	55	}
	56	EXPORT_SYMBOL(freezing_slow_path);
	57
	58	/* Refrigerator is place where frozen processes are stored :-). */
	59	bool __refrigerator(bool check_kthr_stop)
	60	{
	61	/* Hmm, should we be allowed to suspend when there are realtime
	62	processes around? */
	63	bool was_frozen = false;
	64	long save = current->state;
	65
	66	pr_debug("%s entered refrigerator\n", current->comm);
	67
	68	for (;;) {
	69	set_current_state(TASK_UNINTERRUPTIBLE);
	70
	71	spin_lock_irq(&freezer_lock);
	72	current->flags \|= PF_FROZEN;
	73	if (!freezing(current) \|\|
	74	(check_kthr_stop && kthread_should_stop()))
	75	current->flags &= ~PF_FROZEN;
	76	spin_unlock_irq(&freezer_lock);
	77
	78	if (!(current->flags & PF_FROZEN))
	79	break;
	80	was_frozen = true;
	81	schedule();
	82	}
	83
	84	pr_debug("%s left refrigerator\n", current->comm);
	85
	86	/*
	87	* Restore saved task state before returning. The mb'd version
	88	* needs to be used; otherwise, it might silently break
	89	* synchronization which depends on ordered task state change.
	90	*/
	91	set_current_state(save);
	92
	93	return was_frozen;
	94	}
	95	EXPORT_SYMBOL(__refrigerator);
	96
	97	static void fake_signal_wake_up(struct task_struct *p)
	98	{
	99	unsigned long flags;
	100
	101	if (lock_task_sighand(p, &flags)) {
	102	signal_wake_up(p, 0);
	103	unlock_task_sighand(p, &flags);
	104	}
	105	}
	106
	107	/**
	108	* freeze_task - send a freeze request to given task
	109	* @p: task to send the request to
	110	*
	111	* If @p is freezing, the freeze request is sent either by sending a fake
	112	* signal (if it's not a kernel thread) or waking it up (if it's a kernel
	113	* thread).
	114	*
	115	* RETURNS:
	116	* %false, if @p is not freezing or already frozen; %true, otherwise
	117	*/
	118	bool freeze_task(struct task_struct *p)
	119	{
	120	unsigned long flags;
	121
	122	/*
	123	* This check can race with freezer_do_not_count, but worst case that
	124	* will result in an extra wakeup being sent to the task. It does not
	125	* race with freezer_count(), the barriers in freezer_count() and
	126	* freezer_should_skip() ensure that either freezer_count() sees
	127	* freezing == true in try_to_freeze() and freezes, or
	128	* freezer_should_skip() sees !PF_FREEZE_SKIP and freezes the task
	129	* normally.
	130	*/
	131	if (freezer_should_skip(p))
	132	return false;
	133
	134	spin_lock_irqsave(&freezer_lock, flags);
	135	if (!freezing(p) \|\| frozen(p)) {
	136	spin_unlock_irqrestore(&freezer_lock, flags);
	137	return false;
	138	}
	139
	140	if (!(p->flags & PF_KTHREAD))
	141	fake_signal_wake_up(p);
	142	else
	143	wake_up_state(p, TASK_INTERRUPTIBLE);
	144
	145	spin_unlock_irqrestore(&freezer_lock, flags);
	146	return true;
	147	}
	148
	149	void __thaw_task(struct task_struct *p)
	150	{
	151	unsigned long flags;
	152
	153	/*
	154	* Clear freezing and kick @p if FROZEN. Clearing is guaranteed to
	155	* be visible to @p as waking up implies wmb. Waking up inside
	156	* freezer_lock also prevents wakeups from leaking outside
	157	* refrigerator.
	158	*/
	159	spin_lock_irqsave(&freezer_lock, flags);
	160	if (frozen(p))
	161	wake_up_process(p);
	162	spin_unlock_irqrestore(&freezer_lock, flags);
	163	}
	164
	165	/**
	166	* set_freezable - make %current freezable
	167	*
	168	* Mark %current freezable and enter refrigerator if necessary.
	169	*/
	170	bool set_freezable(void)
	171	{
	172	might_sleep();
	173
	174	/*
	175	* Modify flags while holding freezer_lock. This ensures the
	176	* freezer notices that we aren't frozen yet or the freezing
	177	* condition is visible to try_to_freeze() below.
	178	*/
	179	spin_lock_irq(&freezer_lock);
	180	current->flags &= ~PF_NOFREEZE;
	181	spin_unlock_irq(&freezer_lock);
	182
	183	return try_to_freeze();
	184	}
	185	EXPORT_SYMBOL(set_freezable);