]>
Commit | Line | Data |
---|---|---|
8174f150 MH |
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> |
8174f150 MH |
10 | #include <linux/syscalls.h> |
11 | #include <linux/freezer.h> | |
8a32c441 | 12 | #include <linux/kthread.h> |
8174f150 MH |
13 | |
14 | /* | |
15 | * freezing is complete, mark current process as frozen | |
16 | */ | |
17 | static inline void frozen_process(void) | |
18 | { | |
19 | if (!unlikely(current->flags & PF_NOFREEZE)) { | |
20 | current->flags |= PF_FROZEN; | |
ee940d8d | 21 | smp_wmb(); |
8174f150 MH |
22 | } |
23 | clear_freeze_flag(current); | |
24 | } | |
25 | ||
26 | /* Refrigerator is place where frozen processes are stored :-). */ | |
8a32c441 | 27 | bool __refrigerator(bool check_kthr_stop) |
8174f150 MH |
28 | { |
29 | /* Hmm, should we be allowed to suspend when there are realtime | |
30 | processes around? */ | |
a0acae0e | 31 | bool was_frozen = false; |
8174f150 MH |
32 | long save; |
33 | ||
34 | task_lock(current); | |
35 | if (freezing(current)) { | |
36 | frozen_process(); | |
37 | task_unlock(current); | |
38 | } else { | |
39 | task_unlock(current); | |
a0acae0e | 40 | return was_frozen; |
8174f150 MH |
41 | } |
42 | save = current->state; | |
43 | pr_debug("%s entered refrigerator\n", current->comm); | |
44 | ||
45 | spin_lock_irq(¤t->sighand->siglock); | |
46 | recalc_sigpending(); /* We sent fake signal, clean it up */ | |
47 | spin_unlock_irq(¤t->sighand->siglock); | |
48 | ||
6301cb95 TG |
49 | /* prevent accounting of that task to load */ |
50 | current->flags |= PF_FREEZING; | |
51 | ||
8174f150 MH |
52 | for (;;) { |
53 | set_current_state(TASK_UNINTERRUPTIBLE); | |
8a32c441 TH |
54 | if (!frozen(current) || |
55 | (check_kthr_stop && kthread_should_stop())) | |
8174f150 | 56 | break; |
a0acae0e | 57 | was_frozen = true; |
8174f150 MH |
58 | schedule(); |
59 | } | |
6301cb95 TG |
60 | |
61 | /* Remove the accounting blocker */ | |
62 | current->flags &= ~PF_FREEZING; | |
63 | ||
8174f150 | 64 | pr_debug("%s left refrigerator\n", current->comm); |
50fb4f7f TH |
65 | |
66 | /* | |
67 | * Restore saved task state before returning. The mb'd version | |
68 | * needs to be used; otherwise, it might silently break | |
69 | * synchronization which depends on ordered task state change. | |
70 | */ | |
71 | set_current_state(save); | |
a0acae0e TH |
72 | |
73 | return was_frozen; | |
8174f150 | 74 | } |
a0acae0e | 75 | EXPORT_SYMBOL(__refrigerator); |
8174f150 MH |
76 | |
77 | static void fake_signal_wake_up(struct task_struct *p) | |
78 | { | |
79 | unsigned long flags; | |
80 | ||
81 | spin_lock_irqsave(&p->sighand->siglock, flags); | |
d6cc7685 | 82 | signal_wake_up(p, 0); |
8174f150 MH |
83 | spin_unlock_irqrestore(&p->sighand->siglock, flags); |
84 | } | |
85 | ||
86 | /** | |
87 | * freeze_task - send a freeze request to given task | |
88 | * @p: task to send the request to | |
89 | * @sig_only: if set, the request will only be sent if the task has the | |
90 | * PF_FREEZER_NOSIG flag unset | |
91 | * Return value: 'false', if @sig_only is set and the task has | |
92 | * PF_FREEZER_NOSIG set or the task is frozen, 'true', otherwise | |
93 | * | |
94 | * The freeze request is sent by setting the tasks's TIF_FREEZE flag and | |
95 | * either sending a fake signal to it or waking it up, depending on whether | |
96 | * or not it has PF_FREEZER_NOSIG set. If @sig_only is set and the task | |
97 | * has PF_FREEZER_NOSIG set (ie. it is a typical kernel thread), its | |
98 | * TIF_FREEZE flag will not be set. | |
99 | */ | |
100 | bool freeze_task(struct task_struct *p, bool sig_only) | |
101 | { | |
102 | /* | |
103 | * We first check if the task is freezing and next if it has already | |
104 | * been frozen to avoid the race with frozen_process() which first marks | |
105 | * the task as frozen and next clears its TIF_FREEZE. | |
106 | */ | |
107 | if (!freezing(p)) { | |
ee940d8d | 108 | smp_rmb(); |
8174f150 MH |
109 | if (frozen(p)) |
110 | return false; | |
111 | ||
112 | if (!sig_only || should_send_signal(p)) | |
113 | set_freeze_flag(p); | |
114 | else | |
115 | return false; | |
116 | } | |
117 | ||
118 | if (should_send_signal(p)) { | |
8cfe400c TH |
119 | fake_signal_wake_up(p); |
120 | /* | |
121 | * fake_signal_wake_up() goes through p's scheduler | |
122 | * lock and guarantees that TASK_STOPPED/TRACED -> | |
123 | * TASK_RUNNING transition can't race with task state | |
124 | * testing in try_to_freeze_tasks(). | |
125 | */ | |
8174f150 MH |
126 | } else if (sig_only) { |
127 | return false; | |
128 | } else { | |
129 | wake_up_state(p, TASK_INTERRUPTIBLE); | |
130 | } | |
131 | ||
132 | return true; | |
133 | } | |
134 | ||
135 | void cancel_freezing(struct task_struct *p) | |
136 | { | |
137 | unsigned long flags; | |
138 | ||
139 | if (freezing(p)) { | |
140 | pr_debug(" clean up: %s\n", p->comm); | |
141 | clear_freeze_flag(p); | |
142 | spin_lock_irqsave(&p->sighand->siglock, flags); | |
143 | recalc_sigpending_and_wake(p); | |
144 | spin_unlock_irqrestore(&p->sighand->siglock, flags); | |
145 | } | |
146 | } | |
dc52ddc0 | 147 | |
00c2e63c | 148 | static int __thaw_process(struct task_struct *p) |
dc52ddc0 MH |
149 | { |
150 | if (frozen(p)) { | |
151 | p->flags &= ~PF_FROZEN; | |
152 | return 1; | |
153 | } | |
154 | clear_freeze_flag(p); | |
155 | return 0; | |
156 | } | |
157 | ||
00c2e63c LZ |
158 | /* |
159 | * Wake up a frozen process | |
160 | * | |
161 | * task_lock() is needed to prevent the race with refrigerator() which may | |
162 | * occur if the freezing of tasks fails. Namely, without the lock, if the | |
163 | * freezing of tasks failed, thaw_tasks() might have run before a task in | |
164 | * refrigerator() could call frozen_process(), in which case the task would be | |
165 | * frozen and no one would thaw it. | |
166 | */ | |
dc52ddc0 MH |
167 | int thaw_process(struct task_struct *p) |
168 | { | |
169 | task_lock(p); | |
170 | if (__thaw_process(p) == 1) { | |
171 | task_unlock(p); | |
172 | wake_up_process(p); | |
173 | return 1; | |
174 | } | |
175 | task_unlock(p); | |
176 | return 0; | |
177 | } | |
178 | EXPORT_SYMBOL(thaw_process); |