thinkpad-acpi: avoid keymap pitfall
[linux-2.6/linux-acpi-2.6/ibm-acpi-2.6.git] / kernel / freezer.c
blobbd1d42b17cb2f52f5156506ba25d75376102af7f
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/module.h>
10 #include <linux/syscalls.h>
11 #include <linux/freezer.h>
14 * freezing is complete, mark current process as frozen
16 static inline void frozen_process(void)
18 if (!unlikely(current->flags & PF_NOFREEZE)) {
19 current->flags |= PF_FROZEN;
20 wmb();
22 clear_freeze_flag(current);
25 /* Refrigerator is place where frozen processes are stored :-). */
26 void refrigerator(void)
28 /* Hmm, should we be allowed to suspend when there are realtime
29 processes around? */
30 long save;
32 task_lock(current);
33 if (freezing(current)) {
34 frozen_process();
35 task_unlock(current);
36 } else {
37 task_unlock(current);
38 return;
40 save = current->state;
41 pr_debug("%s entered refrigerator\n", current->comm);
43 spin_lock_irq(&current->sighand->siglock);
44 recalc_sigpending(); /* We sent fake signal, clean it up */
45 spin_unlock_irq(&current->sighand->siglock);
47 /* prevent accounting of that task to load */
48 current->flags |= PF_FREEZING;
50 for (;;) {
51 set_current_state(TASK_UNINTERRUPTIBLE);
52 if (!frozen(current))
53 break;
54 schedule();
57 /* Remove the accounting blocker */
58 current->flags &= ~PF_FREEZING;
60 pr_debug("%s left refrigerator\n", current->comm);
61 __set_current_state(save);
63 EXPORT_SYMBOL(refrigerator);
65 static void fake_signal_wake_up(struct task_struct *p)
67 unsigned long flags;
69 spin_lock_irqsave(&p->sighand->siglock, flags);
70 signal_wake_up(p, 0);
71 spin_unlock_irqrestore(&p->sighand->siglock, flags);
74 /**
75 * freeze_task - send a freeze request to given task
76 * @p: task to send the request to
77 * @sig_only: if set, the request will only be sent if the task has the
78 * PF_FREEZER_NOSIG flag unset
79 * Return value: 'false', if @sig_only is set and the task has
80 * PF_FREEZER_NOSIG set or the task is frozen, 'true', otherwise
82 * The freeze request is sent by setting the tasks's TIF_FREEZE flag and
83 * either sending a fake signal to it or waking it up, depending on whether
84 * or not it has PF_FREEZER_NOSIG set. If @sig_only is set and the task
85 * has PF_FREEZER_NOSIG set (ie. it is a typical kernel thread), its
86 * TIF_FREEZE flag will not be set.
88 bool freeze_task(struct task_struct *p, bool sig_only)
91 * We first check if the task is freezing and next if it has already
92 * been frozen to avoid the race with frozen_process() which first marks
93 * the task as frozen and next clears its TIF_FREEZE.
95 if (!freezing(p)) {
96 rmb();
97 if (frozen(p))
98 return false;
100 if (!sig_only || should_send_signal(p))
101 set_freeze_flag(p);
102 else
103 return false;
106 if (should_send_signal(p)) {
107 if (!signal_pending(p))
108 fake_signal_wake_up(p);
109 } else if (sig_only) {
110 return false;
111 } else {
112 wake_up_state(p, TASK_INTERRUPTIBLE);
115 return true;
118 void cancel_freezing(struct task_struct *p)
120 unsigned long flags;
122 if (freezing(p)) {
123 pr_debug(" clean up: %s\n", p->comm);
124 clear_freeze_flag(p);
125 spin_lock_irqsave(&p->sighand->siglock, flags);
126 recalc_sigpending_and_wake(p);
127 spin_unlock_irqrestore(&p->sighand->siglock, flags);
131 static int __thaw_process(struct task_struct *p)
133 if (frozen(p)) {
134 p->flags &= ~PF_FROZEN;
135 return 1;
137 clear_freeze_flag(p);
138 return 0;
142 * Wake up a frozen process
144 * task_lock() is needed to prevent the race with refrigerator() which may
145 * occur if the freezing of tasks fails. Namely, without the lock, if the
146 * freezing of tasks failed, thaw_tasks() might have run before a task in
147 * refrigerator() could call frozen_process(), in which case the task would be
148 * frozen and no one would thaw it.
150 int thaw_process(struct task_struct *p)
152 task_lock(p);
153 if (__thaw_process(p) == 1) {
154 task_unlock(p);
155 wake_up_process(p);
156 return 1;
158 task_unlock(p);
159 return 0;
161 EXPORT_SYMBOL(thaw_process);