[linux-2.6-block.git] / kernel / freezer.c

// SPDX-License-Identifier: GPL-2.0-only
/*
 * 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
 * system_transition_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 | PF_SUSPEND_TASK))
		return false;

	if (test_tsk_thread_flag(p, 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;

	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	// SPDX-License-Identifier: GPL-2.0-only
	2	/*
	3	* kernel/freezer.c - Function to freeze a process
	4	*
	5	* Originally from kernel/power/process.c
	6	*/
	7
	8	#include <linux/interrupt.h>
	9	#include <linux/suspend.h>
	10	#include <linux/export.h>
	11	#include <linux/syscalls.h>
	12	#include <linux/freezer.h>
	13	#include <linux/kthread.h>
	14
	15	/* total number of freezing conditions in effect */
	16	atomic_t system_freezing_cnt = ATOMIC_INIT(0);
	17	EXPORT_SYMBOL(system_freezing_cnt);
	18
	19	/* indicate whether PM freezing is in effect, protected by
	20	* system_transition_mutex
	21	*/
	22	bool pm_freezing;
	23	bool pm_nosig_freezing;
	24
	25	/*
	26	* Temporary export for the deadlock workaround in ata_scsi_hotplug().
	27	* Remove once the hack becomes unnecessary.
	28	*/
	29	EXPORT_SYMBOL_GPL(pm_freezing);
	30
	31	/* protects freezing and frozen transitions */
	32	static DEFINE_SPINLOCK(freezer_lock);
	33
	34	/**
	35	* freezing_slow_path - slow path for testing whether a task needs to be frozen
	36	* @p: task to be tested
	37	*
	38	* This function is called by freezing() if system_freezing_cnt isn't zero
	39	* and tests whether @p needs to enter and stay in frozen state. Can be
	40	* called under any context. The freezers are responsible for ensuring the
	41	* target tasks see the updated state.
	42	*/
	43	bool freezing_slow_path(struct task_struct *p)
	44	{
	45	if (p->flags & (PF_NOFREEZE \| PF_SUSPEND_TASK))
	46	return false;
	47
	48	if (test_tsk_thread_flag(p, TIF_MEMDIE))
	49	return false;
	50
	51	if (pm_nosig_freezing \|\| cgroup_freezing(p))
	52	return true;
	53
	54	if (pm_freezing && !(p->flags & PF_KTHREAD))
	55	return true;
	56
	57	return false;
	58	}
	59	EXPORT_SYMBOL(freezing_slow_path);
	60
	61	/* Refrigerator is place where frozen processes are stored :-). */
	62	bool __refrigerator(bool check_kthr_stop)
	63	{
	64	/* Hmm, should we be allowed to suspend when there are realtime
	65	processes around? */
	66	bool was_frozen = false;
	67	long save = current->state;
	68
	69	pr_debug("%s entered refrigerator\n", current->comm);
	70
	71	for (;;) {
	72	set_current_state(TASK_UNINTERRUPTIBLE);
	73
	74	spin_lock_irq(&freezer_lock);
	75	current->flags \|= PF_FROZEN;
	76	if (!freezing(current) \|\|
	77	(check_kthr_stop && kthread_should_stop()))
	78	current->flags &= ~PF_FROZEN;
	79	spin_unlock_irq(&freezer_lock);
	80
	81	if (!(current->flags & PF_FROZEN))
	82	break;
	83	was_frozen = true;
	84	schedule();
	85	}
	86
	87	pr_debug("%s left refrigerator\n", current->comm);
	88
	89	/*
	90	* Restore saved task state before returning. The mb'd version
	91	* needs to be used; otherwise, it might silently break
	92	* synchronization which depends on ordered task state change.
	93	*/
	94	set_current_state(save);
	95
	96	return was_frozen;
	97	}
	98	EXPORT_SYMBOL(__refrigerator);
	99
	100	static void fake_signal_wake_up(struct task_struct *p)
	101	{
	102	unsigned long flags;
	103
	104	if (lock_task_sighand(p, &flags)) {
	105	signal_wake_up(p, 0);
	106	unlock_task_sighand(p, &flags);
	107	}
	108	}
	109
	110	/**
	111	* freeze_task - send a freeze request to given task
	112	* @p: task to send the request to
	113	*
	114	* If @p is freezing, the freeze request is sent either by sending a fake
	115	* signal (if it's not a kernel thread) or waking it up (if it's a kernel
	116	* thread).
	117	*
	118	* RETURNS:
	119	* %false, if @p is not freezing or already frozen; %true, otherwise
	120	*/
	121	bool freeze_task(struct task_struct *p)
	122	{
	123	unsigned long flags;
	124
	125	/*
	126	* This check can race with freezer_do_not_count, but worst case that
	127	* will result in an extra wakeup being sent to the task. It does not
	128	* race with freezer_count(), the barriers in freezer_count() and
	129	* freezer_should_skip() ensure that either freezer_count() sees
	130	* freezing == true in try_to_freeze() and freezes, or
	131	* freezer_should_skip() sees !PF_FREEZE_SKIP and freezes the task
	132	* normally.
	133	*/
	134	if (freezer_should_skip(p))
	135	return false;
	136
	137	spin_lock_irqsave(&freezer_lock, flags);
	138	if (!freezing(p) \|\| frozen(p)) {
	139	spin_unlock_irqrestore(&freezer_lock, flags);
	140	return false;
	141	}
	142
	143	if (!(p->flags & PF_KTHREAD))
	144	fake_signal_wake_up(p);
	145	else
	146	wake_up_state(p, TASK_INTERRUPTIBLE);
	147
	148	spin_unlock_irqrestore(&freezer_lock, flags);
	149	return true;
	150	}
	151
	152	void __thaw_task(struct task_struct *p)
	153	{
	154	unsigned long flags;
	155
	156	spin_lock_irqsave(&freezer_lock, flags);
	157	if (frozen(p))
	158	wake_up_process(p);
	159	spin_unlock_irqrestore(&freezer_lock, flags);
	160	}
	161
	162	/**
	163	* set_freezable - make %current freezable
	164	*
	165	* Mark %current freezable and enter refrigerator if necessary.
	166	*/
	167	bool set_freezable(void)
	168	{
	169	might_sleep();
	170
	171	/*
	172	* Modify flags while holding freezer_lock. This ensures the
	173	* freezer notices that we aren't frozen yet or the freezing
	174	* condition is visible to try_to_freeze() below.
	175	*/
	176	spin_lock_irq(&freezer_lock);
	177	current->flags &= ~PF_NOFREEZE;
	178	spin_unlock_irq(&freezer_lock);
	179
	180	return try_to_freeze();
	181	}
	182	EXPORT_SYMBOL(set_freezable);