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/module.h>
10 #include <linux/syscalls.h>
11 #include <linux/freezer.h>
14 * freezing is complete, mark current process as frozen
16 static inline void frozen_process(void)
18 if (!unlikely(current->flags & PF_NOFREEZE)) {
19 current->flags |= PF_FROZEN;
22 clear_freeze_flag(current);
25 /* Refrigerator is place where frozen processes are stored :-). */
26 void refrigerator(void)
28 /* Hmm, should we be allowed to suspend when there are realtime
33 if (freezing(current)) {
40 save = current->state;
41 pr_debug("%s entered refrigerator\n", current->comm);
43 spin_lock_irq(¤t->sighand->siglock);
44 recalc_sigpending(); /* We sent fake signal, clean it up */
45 spin_unlock_irq(¤t->sighand->siglock);
48 set_current_state(TASK_UNINTERRUPTIBLE);
53 pr_debug("%s left refrigerator\n", current->comm);
54 __set_current_state(save);
56 EXPORT_SYMBOL(refrigerator);
58 static void fake_signal_wake_up(struct task_struct *p)
62 spin_lock_irqsave(&p->sighand->siglock, flags);
64 spin_unlock_irqrestore(&p->sighand->siglock, flags);
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
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.
81 bool freeze_task(struct task_struct *p, bool sig_only)
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.
93 if (!sig_only || should_send_signal(p))
99 if (should_send_signal(p)) {
100 if (!signal_pending(p))
101 fake_signal_wake_up(p);
102 } else if (sig_only) {
105 wake_up_state(p, TASK_INTERRUPTIBLE);
111 void cancel_freezing(struct task_struct *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);
124 static int __thaw_process(struct task_struct *p)
127 p->flags &= ~PF_FROZEN;
130 clear_freeze_flag(p);
135 * Wake up a frozen process
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.
143 int thaw_process(struct task_struct *p)
146 if (__thaw_process(p) == 1) {
154 EXPORT_SYMBOL(thaw_process);