155 lines
3.7 KiB
C
155 lines
3.7 KiB
C
/*
|
|
* kernel/freezer.c - Function to freeze a process
|
|
*
|
|
* Originally from kernel/power/process.c
|
|
*/
|
|
|
|
#include <linux/interrupt.h>
|
|
#include <linux/suspend.h>
|
|
#include <linux/module.h>
|
|
#include <linux/syscalls.h>
|
|
#include <linux/freezer.h>
|
|
|
|
/*
|
|
* freezing is complete, mark current process as frozen
|
|
*/
|
|
static inline void frozen_process(void)
|
|
{
|
|
if (!unlikely(current->flags & PF_NOFREEZE)) {
|
|
current->flags |= PF_FROZEN;
|
|
wmb();
|
|
}
|
|
clear_freeze_flag(current);
|
|
}
|
|
|
|
/* Refrigerator is place where frozen processes are stored :-). */
|
|
void refrigerator(void)
|
|
{
|
|
/* Hmm, should we be allowed to suspend when there are realtime
|
|
processes around? */
|
|
long save;
|
|
|
|
task_lock(current);
|
|
if (freezing(current)) {
|
|
frozen_process();
|
|
task_unlock(current);
|
|
} else {
|
|
task_unlock(current);
|
|
return;
|
|
}
|
|
save = current->state;
|
|
pr_debug("%s entered refrigerator\n", current->comm);
|
|
|
|
spin_lock_irq(¤t->sighand->siglock);
|
|
recalc_sigpending(); /* We sent fake signal, clean it up */
|
|
spin_unlock_irq(¤t->sighand->siglock);
|
|
|
|
for (;;) {
|
|
set_current_state(TASK_UNINTERRUPTIBLE);
|
|
if (!frozen(current))
|
|
break;
|
|
schedule();
|
|
}
|
|
pr_debug("%s left refrigerator\n", current->comm);
|
|
__set_current_state(save);
|
|
}
|
|
EXPORT_SYMBOL(refrigerator);
|
|
|
|
static void fake_signal_wake_up(struct task_struct *p)
|
|
{
|
|
unsigned long flags;
|
|
|
|
spin_lock_irqsave(&p->sighand->siglock, flags);
|
|
signal_wake_up(p, 0);
|
|
spin_unlock_irqrestore(&p->sighand->siglock, flags);
|
|
}
|
|
|
|
/**
|
|
* freeze_task - send a freeze request to given task
|
|
* @p: task to send the request to
|
|
* @sig_only: if set, the request will only be sent if the task has the
|
|
* PF_FREEZER_NOSIG flag unset
|
|
* Return value: 'false', if @sig_only is set and the task has
|
|
* PF_FREEZER_NOSIG set or the task is frozen, 'true', otherwise
|
|
*
|
|
* The freeze request is sent by setting the tasks's TIF_FREEZE flag and
|
|
* either sending a fake signal to it or waking it up, depending on whether
|
|
* or not it has PF_FREEZER_NOSIG set. If @sig_only is set and the task
|
|
* has PF_FREEZER_NOSIG set (ie. it is a typical kernel thread), its
|
|
* TIF_FREEZE flag will not be set.
|
|
*/
|
|
bool freeze_task(struct task_struct *p, bool sig_only)
|
|
{
|
|
/*
|
|
* We first check if the task is freezing and next if it has already
|
|
* been frozen to avoid the race with frozen_process() which first marks
|
|
* the task as frozen and next clears its TIF_FREEZE.
|
|
*/
|
|
if (!freezing(p)) {
|
|
rmb();
|
|
if (frozen(p))
|
|
return false;
|
|
|
|
if (!sig_only || should_send_signal(p))
|
|
set_freeze_flag(p);
|
|
else
|
|
return false;
|
|
}
|
|
|
|
if (should_send_signal(p)) {
|
|
if (!signal_pending(p))
|
|
fake_signal_wake_up(p);
|
|
} else if (sig_only) {
|
|
return false;
|
|
} else {
|
|
wake_up_state(p, TASK_INTERRUPTIBLE);
|
|
}
|
|
|
|
return true;
|
|
}
|
|
|
|
void cancel_freezing(struct task_struct *p)
|
|
{
|
|
unsigned long flags;
|
|
|
|
if (freezing(p)) {
|
|
pr_debug(" clean up: %s\n", p->comm);
|
|
clear_freeze_flag(p);
|
|
spin_lock_irqsave(&p->sighand->siglock, flags);
|
|
recalc_sigpending_and_wake(p);
|
|
spin_unlock_irqrestore(&p->sighand->siglock, flags);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Wake up a frozen process
|
|
*
|
|
* task_lock() is needed to prevent the race with refrigerator() which may
|
|
* occur if the freezing of tasks fails. Namely, without the lock, if the
|
|
* freezing of tasks failed, thaw_tasks() might have run before a task in
|
|
* refrigerator() could call frozen_process(), in which case the task would be
|
|
* frozen and no one would thaw it.
|
|
*/
|
|
int __thaw_process(struct task_struct *p)
|
|
{
|
|
if (frozen(p)) {
|
|
p->flags &= ~PF_FROZEN;
|
|
return 1;
|
|
}
|
|
clear_freeze_flag(p);
|
|
return 0;
|
|
}
|
|
|
|
int thaw_process(struct task_struct *p)
|
|
{
|
|
task_lock(p);
|
|
if (__thaw_process(p) == 1) {
|
|
task_unlock(p);
|
|
wake_up_process(p);
|
|
return 1;
|
|
}
|
|
task_unlock(p);
|
|
return 0;
|
|
}
|
|
EXPORT_SYMBOL(thaw_process);
|