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Matt Helsley8174f152008-10-18 20:27:19 -07001/*
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>
Paul Gortmaker9984de12011-05-23 14:51:41 -04009#include <linux/export.h>
Matt Helsley8174f152008-10-18 20:27:19 -070010#include <linux/syscalls.h>
11#include <linux/freezer.h>
Tejun Heo8a32c442011-11-21 12:32:23 -080012#include <linux/kthread.h>
Matt Helsley8174f152008-10-18 20:27:19 -070013
Tejun Heoa3201222011-11-21 12:32:25 -080014/* 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
Tejun Heo85fbd722013-12-18 07:07:32 -050022/*
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
Tejun Heo0c9af092011-11-21 12:32:24 -080028/* protects freezing and frozen transitions */
29static DEFINE_SPINLOCK(freezer_lock);
Matt Helsley8174f152008-10-18 20:27:19 -070030
Tejun Heoa3201222011-11-21 12:32:25 -080031/**
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{
Colin Cross2b44c4d2013-07-24 17:41:33 -070042 if (p->flags & (PF_NOFREEZE | PF_SUSPEND_TASK))
Tejun Heoa3201222011-11-21 12:32:25 -080043 return false;
44
Cong Wang51fae6da2014-10-21 09:27:12 +020045 if (test_thread_flag(TIF_MEMDIE))
46 return false;
47
Tejun Heoa3201222011-11-21 12:32:25 -080048 if (pm_nosig_freezing || cgroup_freezing(p))
49 return true;
50
Tejun Heo34b087e2011-11-23 09:28:17 -080051 if (pm_freezing && !(p->flags & PF_KTHREAD))
Tejun Heoa3201222011-11-21 12:32:25 -080052 return true;
53
54 return false;
55}
56EXPORT_SYMBOL(freezing_slow_path);
57
Matt Helsley8174f152008-10-18 20:27:19 -070058/* Refrigerator is place where frozen processes are stored :-). */
Tejun Heo8a32c442011-11-21 12:32:23 -080059bool __refrigerator(bool check_kthr_stop)
Matt Helsley8174f152008-10-18 20:27:19 -070060{
61 /* Hmm, should we be allowed to suspend when there are realtime
62 processes around? */
Tejun Heoa0acae02011-11-21 12:32:22 -080063 bool was_frozen = false;
Tejun Heo5ece3ea2011-11-21 12:32:26 -080064 long save = current->state;
Matt Helsley8174f152008-10-18 20:27:19 -070065
Matt Helsley8174f152008-10-18 20:27:19 -070066 pr_debug("%s entered refrigerator\n", current->comm);
67
Matt Helsley8174f152008-10-18 20:27:19 -070068 for (;;) {
69 set_current_state(TASK_UNINTERRUPTIBLE);
Tejun Heo5ece3ea2011-11-21 12:32:26 -080070
71 spin_lock_irq(&freezer_lock);
72 current->flags |= PF_FROZEN;
Tejun Heo69074832011-11-21 12:32:24 -080073 if (!freezing(current) ||
Tejun Heo8a32c442011-11-21 12:32:23 -080074 (check_kthr_stop && kthread_should_stop()))
Tejun Heo5ece3ea2011-11-21 12:32:26 -080075 current->flags &= ~PF_FROZEN;
76 spin_unlock_irq(&freezer_lock);
77
78 if (!(current->flags & PF_FROZEN))
Matt Helsley8174f152008-10-18 20:27:19 -070079 break;
Tejun Heoa0acae02011-11-21 12:32:22 -080080 was_frozen = true;
Matt Helsley8174f152008-10-18 20:27:19 -070081 schedule();
82 }
Thomas Gleixner6301cb92009-07-17 14:15:47 +020083
Matt Helsley8174f152008-10-18 20:27:19 -070084 pr_debug("%s left refrigerator\n", current->comm);
Tejun Heo50fb4f7f2011-11-21 12:32:22 -080085
86 /*
87 * Restore saved task state before returning. The mb'd version
88 * needs to be used; otherwise, it might silently break
89 * synchronization which depends on ordered task state change.
90 */
91 set_current_state(save);
Tejun Heoa0acae02011-11-21 12:32:22 -080092
93 return was_frozen;
Matt Helsley8174f152008-10-18 20:27:19 -070094}
Tejun Heoa0acae02011-11-21 12:32:22 -080095EXPORT_SYMBOL(__refrigerator);
Matt Helsley8174f152008-10-18 20:27:19 -070096
97static void fake_signal_wake_up(struct task_struct *p)
98{
99 unsigned long flags;
100
Tejun Heo37ad8ac2011-11-21 12:32:26 -0800101 if (lock_task_sighand(p, &flags)) {
102 signal_wake_up(p, 0);
103 unlock_task_sighand(p, &flags);
104 }
Matt Helsley8174f152008-10-18 20:27:19 -0700105}
106
107/**
Tejun Heo839e3402011-11-21 12:32:26 -0800108 * freeze_task - send a freeze request to given task
109 * @p: task to send the request to
Matt Helsley8174f152008-10-18 20:27:19 -0700110 *
Marcos Paulo de Souza37f08be2012-02-21 23:57:47 +0100111 * If @p is freezing, the freeze request is sent either by sending a fake
112 * signal (if it's not a kernel thread) or waking it up (if it's a kernel
113 * thread).
Tejun Heo839e3402011-11-21 12:32:26 -0800114 *
115 * RETURNS:
116 * %false, if @p is not freezing or already frozen; %true, otherwise
Matt Helsley8174f152008-10-18 20:27:19 -0700117 */
Tejun Heo839e3402011-11-21 12:32:26 -0800118bool freeze_task(struct task_struct *p)
Matt Helsley8174f152008-10-18 20:27:19 -0700119{
Tejun Heo0c9af092011-11-21 12:32:24 -0800120 unsigned long flags;
Matt Helsley8174f152008-10-18 20:27:19 -0700121
Colin Cross613f5d12013-05-06 23:50:11 +0000122 /*
123 * This check can race with freezer_do_not_count, but worst case that
124 * will result in an extra wakeup being sent to the task. It does not
125 * race with freezer_count(), the barriers in freezer_count() and
126 * freezer_should_skip() ensure that either freezer_count() sees
127 * freezing == true in try_to_freeze() and freezes, or
128 * freezer_should_skip() sees !PF_FREEZE_SKIP and freezes the task
129 * normally.
130 */
131 if (freezer_should_skip(p))
132 return false;
133
Tejun Heo0c9af092011-11-21 12:32:24 -0800134 spin_lock_irqsave(&freezer_lock, flags);
Tejun Heoa3201222011-11-21 12:32:25 -0800135 if (!freezing(p) || frozen(p)) {
136 spin_unlock_irqrestore(&freezer_lock, flags);
137 return false;
138 }
Matt Helsley8174f152008-10-18 20:27:19 -0700139
Oleg Nesterov5d8f72b2012-10-26 19:46:06 +0200140 if (!(p->flags & PF_KTHREAD))
Tejun Heo8cfe4002010-11-26 23:07:27 +0100141 fake_signal_wake_up(p);
Oleg Nesterov5d8f72b2012-10-26 19:46:06 +0200142 else
Matt Helsley8174f152008-10-18 20:27:19 -0700143 wake_up_state(p, TASK_INTERRUPTIBLE);
Tejun Heoa3201222011-11-21 12:32:25 -0800144
Tejun Heo0c9af092011-11-21 12:32:24 -0800145 spin_unlock_irqrestore(&freezer_lock, flags);
Tejun Heoa3201222011-11-21 12:32:25 -0800146 return true;
Matt Helsley8174f152008-10-18 20:27:19 -0700147}
148
Tejun Heoa5be2d02011-11-21 12:32:23 -0800149void __thaw_task(struct task_struct *p)
Matt Helsleydc52ddc2008-10-18 20:27:21 -0700150{
Tejun Heo0c9af092011-11-21 12:32:24 -0800151 unsigned long flags;
Tejun Heoa5be2d02011-11-21 12:32:23 -0800152
Tejun Heo0c9af092011-11-21 12:32:24 -0800153 spin_lock_irqsave(&freezer_lock, flags);
Tejun Heo34b087e2011-11-23 09:28:17 -0800154 if (frozen(p))
Tejun Heoa5be2d02011-11-21 12:32:23 -0800155 wake_up_process(p);
Tejun Heo0c9af092011-11-21 12:32:24 -0800156 spin_unlock_irqrestore(&freezer_lock, flags);
Matt Helsleydc52ddc2008-10-18 20:27:21 -0700157}
Tejun Heo96ee6d82011-11-21 12:32:25 -0800158
159/**
Tejun Heo34b087e2011-11-23 09:28:17 -0800160 * set_freezable - make %current freezable
Tejun Heo96ee6d82011-11-21 12:32:25 -0800161 *
162 * Mark %current freezable and enter refrigerator if necessary.
163 */
Tejun Heo34b087e2011-11-23 09:28:17 -0800164bool set_freezable(void)
Tejun Heo96ee6d82011-11-21 12:32:25 -0800165{
166 might_sleep();
167
168 /*
169 * Modify flags while holding freezer_lock. This ensures the
170 * freezer notices that we aren't frozen yet or the freezing
171 * condition is visible to try_to_freeze() below.
172 */
173 spin_lock_irq(&freezer_lock);
174 current->flags &= ~PF_NOFREEZE;
Tejun Heo96ee6d82011-11-21 12:32:25 -0800175 spin_unlock_irq(&freezer_lock);
176
177 return try_to_freeze();
178}
Tejun Heo34b087e2011-11-23 09:28:17 -0800179EXPORT_SYMBOL(set_freezable);