2 * kernel/freezer.c - Function to freeze a process
4 * Originally from kernel/power/process.c
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>
14 /* total number of freezing conditions in effect */
15 atomic_t system_freezing_cnt = ATOMIC_INIT(0);
16 EXPORT_SYMBOL(system_freezing_cnt);
18 /* indicate whether PM freezing is in effect, protected by pm_mutex */
20 bool pm_nosig_freezing;
22 /* protects freezing and frozen transitions */
23 static DEFINE_SPINLOCK(freezer_lock);
26 * freezing_slow_path - slow path for testing whether a task needs to be frozen
27 * @p: task to be tested
29 * This function is called by freezing() if system_freezing_cnt isn't zero
30 * and tests whether @p needs to enter and stay in frozen state. Can be
31 * called under any context. The freezers are responsible for ensuring the
32 * target tasks see the updated state.
34 bool freezing_slow_path(struct task_struct *p)
36 if (p->flags & PF_NOFREEZE)
39 if (pm_nosig_freezing || cgroup_freezing(p))
42 if (pm_freezing && !(p->flags & PF_FREEZER_NOSIG))
47 EXPORT_SYMBOL(freezing_slow_path);
49 /* Refrigerator is place where frozen processes are stored :-). */
50 bool __refrigerator(bool check_kthr_stop)
52 /* Hmm, should we be allowed to suspend when there are realtime
54 bool was_frozen = false;
58 * No point in checking freezing() again - the caller already did.
59 * Proceed to enter FROZEN.
61 spin_lock_irq(&freezer_lock);
63 current->flags |= PF_FROZEN;
64 spin_unlock_irq(&freezer_lock);
66 save = current->state;
67 pr_debug("%s entered refrigerator\n", current->comm);
69 spin_lock_irq(¤t->sighand->siglock);
70 recalc_sigpending(); /* We sent fake signal, clean it up */
71 spin_unlock_irq(¤t->sighand->siglock);
74 set_current_state(TASK_UNINTERRUPTIBLE);
75 if (!freezing(current) ||
76 (check_kthr_stop && kthread_should_stop()))
83 spin_lock_irq(&freezer_lock);
84 if (freezing(current))
86 current->flags &= ~PF_FROZEN;
87 spin_unlock_irq(&freezer_lock);
89 pr_debug("%s left refrigerator\n", current->comm);
92 * Restore saved task state before returning. The mb'd version
93 * needs to be used; otherwise, it might silently break
94 * synchronization which depends on ordered task state change.
96 set_current_state(save);
100 EXPORT_SYMBOL(__refrigerator);
102 static void fake_signal_wake_up(struct task_struct *p)
106 spin_lock_irqsave(&p->sighand->siglock, flags);
107 signal_wake_up(p, 0);
108 spin_unlock_irqrestore(&p->sighand->siglock, flags);
112 * freeze_task - send a freeze request to given task
113 * @p: task to send the request to
114 * @sig_only: if set, the request will only be sent if the task has the
115 * PF_FREEZER_NOSIG flag unset
116 * Return value: 'false', if @sig_only is set and the task has
117 * PF_FREEZER_NOSIG set or the task is frozen, 'true', otherwise
119 * The freeze request is sent by setting the tasks's TIF_FREEZE flag and
120 * either sending a fake signal to it or waking it up, depending on whether
121 * or not it has PF_FREEZER_NOSIG set. If @sig_only is set and the task
122 * has PF_FREEZER_NOSIG set (ie. it is a typical kernel thread), its
123 * TIF_FREEZE flag will not be set.
125 bool freeze_task(struct task_struct *p, bool sig_only)
129 spin_lock_irqsave(&freezer_lock, flags);
130 if (!freezing(p) || frozen(p)) {
131 spin_unlock_irqrestore(&freezer_lock, flags);
135 if (!(p->flags & PF_FREEZER_NOSIG)) {
136 fake_signal_wake_up(p);
138 * fake_signal_wake_up() goes through p's scheduler
139 * lock and guarantees that TASK_STOPPED/TRACED ->
140 * TASK_RUNNING transition can't race with task state
141 * testing in try_to_freeze_tasks().
144 wake_up_state(p, TASK_INTERRUPTIBLE);
147 spin_unlock_irqrestore(&freezer_lock, flags);
151 void __thaw_task(struct task_struct *p)
156 * Clear freezing and kick @p if FROZEN. Clearing is guaranteed to
157 * be visible to @p as waking up implies wmb. Waking up inside
158 * freezer_lock also prevents wakeups from leaking outside
161 * If !FROZEN, @p hasn't reached refrigerator, recalc sigpending to
162 * avoid leaving dangling TIF_SIGPENDING behind.
164 spin_lock_irqsave(&freezer_lock, flags);
168 spin_lock(&p->sighand->siglock);
169 recalc_sigpending_and_wake(p);
170 spin_unlock(&p->sighand->siglock);
172 spin_unlock_irqrestore(&freezer_lock, flags);