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;
55 long save = current->state;
57 pr_debug("%s entered refrigerator\n", current->comm);
60 set_current_state(TASK_UNINTERRUPTIBLE);
62 spin_lock_irq(&freezer_lock);
63 current->flags |= PF_FROZEN;
64 if (!freezing(current) ||
65 (check_kthr_stop && kthread_should_stop()))
66 current->flags &= ~PF_FROZEN;
67 spin_unlock_irq(&freezer_lock);
69 if (!(current->flags & PF_FROZEN))
75 spin_lock_irq(¤t->sighand->siglock);
76 recalc_sigpending(); /* We sent fake signal, clean it up */
77 spin_unlock_irq(¤t->sighand->siglock);
79 pr_debug("%s left refrigerator\n", current->comm);
82 * Restore saved task state before returning. The mb'd version
83 * needs to be used; otherwise, it might silently break
84 * synchronization which depends on ordered task state change.
86 set_current_state(save);
90 EXPORT_SYMBOL(__refrigerator);
92 static void fake_signal_wake_up(struct task_struct *p)
96 if (lock_task_sighand(p, &flags)) {
98 unlock_task_sighand(p, &flags);
103 * freeze_task - send a freeze request to given task
104 * @p: task to send the request to
105 * @sig_only: if set, the request will only be sent if the task has the
106 * PF_FREEZER_NOSIG flag unset
107 * Return value: 'false', if @sig_only is set and the task has
108 * PF_FREEZER_NOSIG set or the task is frozen, 'true', otherwise
110 * The freeze request is sent by setting the tasks's TIF_FREEZE flag and
111 * either sending a fake signal to it or waking it up, depending on whether
112 * or not it has PF_FREEZER_NOSIG set. If @sig_only is set and the task
113 * has PF_FREEZER_NOSIG set (ie. it is a typical kernel thread), its
114 * TIF_FREEZE flag will not be set.
116 bool freeze_task(struct task_struct *p, bool sig_only)
120 spin_lock_irqsave(&freezer_lock, flags);
121 if (!freezing(p) || frozen(p)) {
122 spin_unlock_irqrestore(&freezer_lock, flags);
126 if (!(p->flags & PF_FREEZER_NOSIG)) {
127 fake_signal_wake_up(p);
129 * fake_signal_wake_up() goes through p's scheduler
130 * lock and guarantees that TASK_STOPPED/TRACED ->
131 * TASK_RUNNING transition can't race with task state
132 * testing in try_to_freeze_tasks().
135 wake_up_state(p, TASK_INTERRUPTIBLE);
138 spin_unlock_irqrestore(&freezer_lock, flags);
142 void __thaw_task(struct task_struct *p)
147 * Clear freezing and kick @p if FROZEN. Clearing is guaranteed to
148 * be visible to @p as waking up implies wmb. Waking up inside
149 * freezer_lock also prevents wakeups from leaking outside
152 * If !FROZEN, @p hasn't reached refrigerator, recalc sigpending to
153 * avoid leaving dangling TIF_SIGPENDING behind.
155 spin_lock_irqsave(&freezer_lock, flags);
159 spin_lock(&p->sighand->siglock);
160 recalc_sigpending_and_wake(p);
161 spin_unlock(&p->sighand->siglock);
163 spin_unlock_irqrestore(&freezer_lock, flags);
167 * __set_freezable - make %current freezable
168 * @with_signal: do we want %TIF_SIGPENDING for notification too?
170 * Mark %current freezable and enter refrigerator if necessary.
172 bool __set_freezable(bool with_signal)
177 * Modify flags while holding freezer_lock. This ensures the
178 * freezer notices that we aren't frozen yet or the freezing
179 * condition is visible to try_to_freeze() below.
181 spin_lock_irq(&freezer_lock);
182 current->flags &= ~PF_NOFREEZE;
184 current->flags &= ~PF_FREEZER_NOSIG;
185 spin_unlock_irq(&freezer_lock);
187 return try_to_freeze();
189 EXPORT_SYMBOL(__set_freezable);