blob: 6f56a9e219facf003d802bd1e9c0cd2dea9824d3
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> |
9 | #include <linux/export.h> |
10 | #include <linux/syscalls.h> |
11 | #include <linux/freezer.h> |
12 | #include <linux/kthread.h> |
13 | |
14 | /* total number of freezing conditions in effect */ |
15 | atomic_t system_freezing_cnt = ATOMIC_INIT(0); |
16 | EXPORT_SYMBOL(system_freezing_cnt); |
17 | |
18 | /* indicate whether PM freezing is in effect, protected by pm_mutex */ |
19 | bool pm_freezing; |
20 | bool pm_nosig_freezing; |
21 | |
22 | /* |
23 | * Temporary export for the deadlock workaround in ata_scsi_hotplug(). |
24 | * Remove once the hack becomes unnecessary. |
25 | */ |
26 | EXPORT_SYMBOL_GPL(pm_freezing); |
27 | |
28 | /* protects freezing and frozen transitions */ |
29 | static DEFINE_SPINLOCK(freezer_lock); |
30 | |
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 | */ |
40 | bool freezing_slow_path(struct task_struct *p) |
41 | { |
42 | if (p->flags & (PF_NOFREEZE | PF_SUSPEND_TASK)) |
43 | return false; |
44 | |
45 | if (test_tsk_thread_flag(p, TIF_MEMDIE)) |
46 | return false; |
47 | |
48 | if (pm_nosig_freezing || cgroup_freezing(p)) |
49 | return true; |
50 | |
51 | if (pm_freezing && !(p->flags & PF_KTHREAD)) |
52 | return true; |
53 | |
54 | return false; |
55 | } |
56 | EXPORT_SYMBOL(freezing_slow_path); |
57 | |
58 | /* Refrigerator is place where frozen processes are stored :-). */ |
59 | bool __refrigerator(bool check_kthr_stop) |
60 | { |
61 | /* Hmm, should we be allowed to suspend when there are realtime |
62 | processes around? */ |
63 | bool was_frozen = false; |
64 | long save = current->state; |
65 | |
66 | pr_debug("%s entered refrigerator\n", current->comm); |
67 | |
68 | for (;;) { |
69 | set_current_state(TASK_UNINTERRUPTIBLE); |
70 | |
71 | spin_lock_irq(&freezer_lock); |
72 | current->flags |= PF_FROZEN; |
73 | if (!freezing(current) || |
74 | (check_kthr_stop && kthread_should_stop())) |
75 | current->flags &= ~PF_FROZEN; |
76 | spin_unlock_irq(&freezer_lock); |
77 | |
78 | if (!(current->flags & PF_FROZEN)) |
79 | break; |
80 | was_frozen = true; |
81 | schedule(); |
82 | } |
83 | |
84 | pr_debug("%s left refrigerator\n", current->comm); |
85 | |
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); |
92 | |
93 | return was_frozen; |
94 | } |
95 | EXPORT_SYMBOL(__refrigerator); |
96 | |
97 | static void fake_signal_wake_up(struct task_struct *p) |
98 | { |
99 | unsigned long flags; |
100 | |
101 | if (lock_task_sighand(p, &flags)) { |
102 | signal_wake_up(p, 0); |
103 | unlock_task_sighand(p, &flags); |
104 | } |
105 | } |
106 | |
107 | /** |
108 | * freeze_task - send a freeze request to given task |
109 | * @p: task to send the request to |
110 | * |
111 | * 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). |
114 | * |
115 | * RETURNS: |
116 | * %false, if @p is not freezing or already frozen; %true, otherwise |
117 | */ |
118 | bool freeze_task(struct task_struct *p) |
119 | { |
120 | unsigned long flags; |
121 | |
122 | /* |
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 | |
134 | spin_lock_irqsave(&freezer_lock, flags); |
135 | if (!freezing(p) || frozen(p)) { |
136 | spin_unlock_irqrestore(&freezer_lock, flags); |
137 | return false; |
138 | } |
139 | |
140 | if (!(p->flags & PF_KTHREAD)) |
141 | fake_signal_wake_up(p); |
142 | else |
143 | wake_up_state(p, TASK_INTERRUPTIBLE); |
144 | |
145 | spin_unlock_irqrestore(&freezer_lock, flags); |
146 | return true; |
147 | } |
148 | |
149 | void __thaw_task(struct task_struct *p) |
150 | { |
151 | unsigned long flags; |
152 | |
153 | spin_lock_irqsave(&freezer_lock, flags); |
154 | if (frozen(p)) |
155 | wake_up_process(p); |
156 | spin_unlock_irqrestore(&freezer_lock, flags); |
157 | } |
158 | |
159 | /** |
160 | * set_freezable - make %current freezable |
161 | * |
162 | * Mark %current freezable and enter refrigerator if necessary. |
163 | */ |
164 | bool set_freezable(void) |
165 | { |
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; |
175 | spin_unlock_irq(&freezer_lock); |
176 | |
177 | return try_to_freeze(); |
178 | } |
179 | EXPORT_SYMBOL(set_freezable); |
180 |