Merge tag 'ntb-3.15' of git://github.com/jonmason/ntb
[linux-2.6-block.git] / kernel / freezer.c
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1/*
2 * kernel/freezer.c - Function to freeze a process
3 *
4 * Originally from kernel/power/process.c
5 */
6
7#include <linux/interrupt.h>
8#include <linux/suspend.h>
9984de1a 9#include <linux/export.h>
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10#include <linux/syscalls.h>
11#include <linux/freezer.h>
8a32c441 12#include <linux/kthread.h>
8174f150 13
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14/* total number of freezing conditions in effect */
15atomic_t system_freezing_cnt = ATOMIC_INIT(0);
16EXPORT_SYMBOL(system_freezing_cnt);
17
18/* indicate whether PM freezing is in effect, protected by pm_mutex */
19bool pm_freezing;
20bool pm_nosig_freezing;
21
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22/*
23 * Temporary export for the deadlock workaround in ata_scsi_hotplug().
24 * Remove once the hack becomes unnecessary.
25 */
26EXPORT_SYMBOL_GPL(pm_freezing);
27
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28/* protects freezing and frozen transitions */
29static DEFINE_SPINLOCK(freezer_lock);
8174f150 30
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31/**
32 * freezing_slow_path - slow path for testing whether a task needs to be frozen
33 * @p: task to be tested
34 *
35 * This function is called by freezing() if system_freezing_cnt isn't zero
36 * and tests whether @p needs to enter and stay in frozen state. Can be
37 * called under any context. The freezers are responsible for ensuring the
38 * target tasks see the updated state.
39 */
40bool freezing_slow_path(struct task_struct *p)
41{
2b44c4db 42 if (p->flags & (PF_NOFREEZE | PF_SUSPEND_TASK))
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43 return false;
44
45 if (pm_nosig_freezing || cgroup_freezing(p))
46 return true;
47
34b087e4 48 if (pm_freezing && !(p->flags & PF_KTHREAD))
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49 return true;
50
51 return false;
52}
53EXPORT_SYMBOL(freezing_slow_path);
54
8174f150 55/* Refrigerator is place where frozen processes are stored :-). */
8a32c441 56bool __refrigerator(bool check_kthr_stop)
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57{
58 /* Hmm, should we be allowed to suspend when there are realtime
59 processes around? */
a0acae0e 60 bool was_frozen = false;
5ece3eae 61 long save = current->state;
8174f150 62
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63 pr_debug("%s entered refrigerator\n", current->comm);
64
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65 for (;;) {
66 set_current_state(TASK_UNINTERRUPTIBLE);
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67
68 spin_lock_irq(&freezer_lock);
69 current->flags |= PF_FROZEN;
6907483b 70 if (!freezing(current) ||
8a32c441 71 (check_kthr_stop && kthread_should_stop()))
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72 current->flags &= ~PF_FROZEN;
73 spin_unlock_irq(&freezer_lock);
74
75 if (!(current->flags & PF_FROZEN))
8174f150 76 break;
a0acae0e 77 was_frozen = true;
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78 schedule();
79 }
6301cb95 80
8174f150 81 pr_debug("%s left refrigerator\n", current->comm);
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82
83 /*
84 * Restore saved task state before returning. The mb'd version
85 * needs to be used; otherwise, it might silently break
86 * synchronization which depends on ordered task state change.
87 */
88 set_current_state(save);
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89
90 return was_frozen;
8174f150 91}
a0acae0e 92EXPORT_SYMBOL(__refrigerator);
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93
94static void fake_signal_wake_up(struct task_struct *p)
95{
96 unsigned long flags;
97
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98 if (lock_task_sighand(p, &flags)) {
99 signal_wake_up(p, 0);
100 unlock_task_sighand(p, &flags);
101 }
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102}
103
104/**
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105 * freeze_task - send a freeze request to given task
106 * @p: task to send the request to
8174f150 107 *
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108 * If @p is freezing, the freeze request is sent either by sending a fake
109 * signal (if it's not a kernel thread) or waking it up (if it's a kernel
110 * thread).
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111 *
112 * RETURNS:
113 * %false, if @p is not freezing or already frozen; %true, otherwise
8174f150 114 */
839e3407 115bool freeze_task(struct task_struct *p)
8174f150 116{
0c9af092 117 unsigned long flags;
0c9af092 118
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119 /*
120 * This check can race with freezer_do_not_count, but worst case that
121 * will result in an extra wakeup being sent to the task. It does not
122 * race with freezer_count(), the barriers in freezer_count() and
123 * freezer_should_skip() ensure that either freezer_count() sees
124 * freezing == true in try_to_freeze() and freezes, or
125 * freezer_should_skip() sees !PF_FREEZE_SKIP and freezes the task
126 * normally.
127 */
128 if (freezer_should_skip(p))
129 return false;
130
0c9af092 131 spin_lock_irqsave(&freezer_lock, flags);
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132 if (!freezing(p) || frozen(p)) {
133 spin_unlock_irqrestore(&freezer_lock, flags);
134 return false;
135 }
8174f150 136
5d8f72b5 137 if (!(p->flags & PF_KTHREAD))
8cfe400c 138 fake_signal_wake_up(p);
5d8f72b5 139 else
8174f150 140 wake_up_state(p, TASK_INTERRUPTIBLE);
a3201227 141
0c9af092 142 spin_unlock_irqrestore(&freezer_lock, flags);
a3201227 143 return true;
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144}
145
a5be2d0d 146void __thaw_task(struct task_struct *p)
dc52ddc0 147{
0c9af092 148 unsigned long flags;
a5be2d0d 149
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150 /*
151 * Clear freezing and kick @p if FROZEN. Clearing is guaranteed to
152 * be visible to @p as waking up implies wmb. Waking up inside
153 * freezer_lock also prevents wakeups from leaking outside
154 * refrigerator.
155 */
0c9af092 156 spin_lock_irqsave(&freezer_lock, flags);
34b087e4 157 if (frozen(p))
a5be2d0d 158 wake_up_process(p);
0c9af092 159 spin_unlock_irqrestore(&freezer_lock, flags);
dc52ddc0 160}
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161
162/**
34b087e4 163 * set_freezable - make %current freezable
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164 *
165 * Mark %current freezable and enter refrigerator if necessary.
166 */
34b087e4 167bool set_freezable(void)
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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;
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178 spin_unlock_irq(&freezer_lock);
179
180 return try_to_freeze();
181}
34b087e4 182EXPORT_SYMBOL(set_freezable);