summaryrefslogtreecommitdiffstats
path: root/kernel
diff options
context:
space:
mode:
authorRafael J. Wysocki <rjw@sisk.pl>2006-12-13 00:34:28 -0800
committerLinus Torvalds <torvalds@woody.osdl.org>2006-12-13 09:05:49 -0800
commit3df494a32b936aef76d893f5065f962ebd9b9437 (patch)
tree825a96b219eeb87ef7a627a2494cf4fa7cd4d03e /kernel
parent6a2d7a955d8de6cb19ed9cd194b3c83008a22c32 (diff)
downloadop-kernel-dev-3df494a32b936aef76d893f5065f962ebd9b9437.zip
op-kernel-dev-3df494a32b936aef76d893f5065f962ebd9b9437.tar.gz
[PATCH] PM: Fix freezing of stopped tasks
Currently, if a task is stopped (ie. it's in the TASK_STOPPED state), it is considered by the freezer as unfreezeable. However, there may be a race between the freezer and the delivery of the continuation signal to the task resulting in the task running after we have finished freezing the other tasks. This, in turn, may lead to undesirable effects up to and including data corruption. To prevent this from happening we first need to make the freezer consider stopped tasks as freezeable. For this purpose we need to make freezeable() stop returning 0 for these tasks and we need to force them to enter the refrigerator. However, if there's no continuation signal in the meantime, the stopped tasks should remain stopped after all processes have been thawed, so we need to send an additional SIGSTOP to each of them before waking it up. Also, a stopped task that has just been woken up should first check if there's a freezing request for it and go to the refrigerator if that's the case. Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl> Acked-by: Pavel Machek <pavel@ucw.cz> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/power/process.c12
-rw-r--r--kernel/signal.c4
2 files changed, 9 insertions, 7 deletions
diff --git a/kernel/power/process.c b/kernel/power/process.c
index 99eeb11..b9a3286 100644
--- a/kernel/power/process.c
+++ b/kernel/power/process.c
@@ -28,8 +28,7 @@ static inline int freezeable(struct task_struct * p)
if ((p == current) ||
(p->flags & PF_NOFREEZE) ||
(p->exit_state == EXIT_ZOMBIE) ||
- (p->exit_state == EXIT_DEAD) ||
- (p->state == TASK_STOPPED))
+ (p->exit_state == EXIT_DEAD))
return 0;
return 1;
}
@@ -61,9 +60,12 @@ static inline void freeze_process(struct task_struct *p)
unsigned long flags;
if (!freezing(p)) {
+ if (p->state == TASK_STOPPED)
+ force_sig_specific(SIGSTOP, p);
+
freeze(p);
spin_lock_irqsave(&p->sighand->siglock, flags);
- signal_wake_up(p, 0);
+ signal_wake_up(p, p->state == TASK_STOPPED);
spin_unlock_irqrestore(&p->sighand->siglock, flags);
}
}
@@ -103,9 +105,7 @@ static unsigned int try_to_freeze_tasks(int freeze_user_space)
if (frozen(p))
continue;
- if (p->state == TASK_TRACED &&
- (frozen(p->parent) ||
- p->parent->state == TASK_STOPPED)) {
+ if (p->state == TASK_TRACED && frozen(p->parent)) {
cancel_freezing(p);
continue;
}
diff --git a/kernel/signal.c b/kernel/signal.c
index 1921ffd..5630255 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1705,7 +1705,9 @@ finish_stop(int stop_count)
read_unlock(&tasklist_lock);
}
- schedule();
+ do {
+ schedule();
+ } while (try_to_freeze());
/*
* Now we don't run again until continued.
*/
OpenPOWER on IntegriCloud