Gitweb:
http://git.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=3df494a32b936aef76d893f5065f962ebd9b9437
Commit: 3df494a32b936aef76d893f5065f962ebd9b9437
Parent: 6a2d7a955d8de6cb19ed9cd194b3c83008a22c32
Author: Rafael J. Wysocki <[EMAIL PROTECTED]>
AuthorDate: Wed Dec 13 00:34:28 2006 -0800
Committer: Linus Torvalds <[EMAIL PROTECTED]>
CommitDate: Wed Dec 13 09:05:49 2006 -0800
[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 <[EMAIL PROTECTED]>
Acked-by: Pavel Machek <[EMAIL PROTECTED]>
Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
---
kernel/power/process.c | 12 ++++++------
kernel/signal.c | 4 +++-
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.
*/
-
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