Merge branch 'x86-uv-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git...
[linux-2.6.git] / kernel / freezer.c
blobc38893b0efbaa39d770b11546dba9e97ec53ff51
1 /*
2 * kernel/freezer.c - Function to freeze a process
4 * Originally from kernel/power/process.c
5 */
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 */
19 bool pm_freezing;
20 bool pm_nosig_freezing;
22 /* protects freezing and frozen transitions */
23 static DEFINE_SPINLOCK(freezer_lock);
25 /**
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)
37 return false;
39 if (pm_nosig_freezing || cgroup_freezing(p))
40 return true;
42 if (pm_freezing && !(p->flags & PF_KTHREAD))
43 return true;
45 return false;
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
53 processes around? */
54 bool was_frozen = false;
55 long save = current->state;
57 pr_debug("%s entered refrigerator\n", current->comm);
59 for (;;) {
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))
70 break;
71 was_frozen = true;
72 schedule();
75 pr_debug("%s left refrigerator\n", current->comm);
78 * Restore saved task state before returning. The mb'd version
79 * needs to be used; otherwise, it might silently break
80 * synchronization which depends on ordered task state change.
82 set_current_state(save);
84 return was_frozen;
86 EXPORT_SYMBOL(__refrigerator);
88 static void fake_signal_wake_up(struct task_struct *p)
90 unsigned long flags;
92 if (lock_task_sighand(p, &flags)) {
93 signal_wake_up(p, 0);
94 unlock_task_sighand(p, &flags);
98 /**
99 * freeze_task - send a freeze request to given task
100 * @p: task to send the request to
102 * If @p is freezing, the freeze request is sent either by sending a fake
103 * signal (if it's not a kernel thread) or waking it up (if it's a kernel
104 * thread).
106 * RETURNS:
107 * %false, if @p is not freezing or already frozen; %true, otherwise
109 bool freeze_task(struct task_struct *p)
111 unsigned long flags;
113 spin_lock_irqsave(&freezer_lock, flags);
114 if (!freezing(p) || frozen(p)) {
115 spin_unlock_irqrestore(&freezer_lock, flags);
116 return false;
119 if (!(p->flags & PF_KTHREAD))
120 fake_signal_wake_up(p);
121 else
122 wake_up_state(p, TASK_INTERRUPTIBLE);
124 spin_unlock_irqrestore(&freezer_lock, flags);
125 return true;
128 void __thaw_task(struct task_struct *p)
130 unsigned long flags;
133 * Clear freezing and kick @p if FROZEN. Clearing is guaranteed to
134 * be visible to @p as waking up implies wmb. Waking up inside
135 * freezer_lock also prevents wakeups from leaking outside
136 * refrigerator.
138 spin_lock_irqsave(&freezer_lock, flags);
139 if (frozen(p))
140 wake_up_process(p);
141 spin_unlock_irqrestore(&freezer_lock, flags);
145 * set_freezable - make %current freezable
147 * Mark %current freezable and enter refrigerator if necessary.
149 bool set_freezable(void)
151 might_sleep();
154 * Modify flags while holding freezer_lock. This ensures the
155 * freezer notices that we aren't frozen yet or the freezing
156 * condition is visible to try_to_freeze() below.
158 spin_lock_irq(&freezer_lock);
159 current->flags &= ~PF_NOFREEZE;
160 spin_unlock_irq(&freezer_lock);
162 return try_to_freeze();
164 EXPORT_SYMBOL(set_freezable);