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authorTejun Heo <tj@kernel.org>2011-11-21 12:32:26 -0800
committerTejun Heo <tj@kernel.org>2011-11-21 12:32:26 -0800
commit5ece3eae4cdb968c269e0bc7e2c0e2b223552025 (patch)
tree8e38ac6fc88864eff7fbbe3fa3671a4b76cfd8e9
parent96ee6d8539c9fc6742908d85eb9723abb5c91854 (diff)
downloadvexpress-lsk-5ece3eae4cdb968c269e0bc7e2c0e2b223552025.tar.gz
freezer: restructure __refrigerator()
If another freeze happens before all tasks leave FROZEN state after being thawed, the freezer can see the existing FROZEN and consider the tasks to be frozen but they can clear FROZEN without checking the new freezing(). Oleg suggested restructuring __refrigerator() such that there's single condition check section inside freezer_lock and sigpending is cleared afterwards, which fixes the problem and simplifies the code. Restructure accordingly. -v2: Frozen loop exited without releasing freezer_lock. Fixed. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Oleg Nesterov <oleg@redhat.com> Acked-by: Oleg Nesterov <oleg@redhat.com> Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
-rw-r--r--kernel/freezer.c32
1 files changed, 11 insertions, 21 deletions
diff --git a/kernel/freezer.c b/kernel/freezer.c
index b1e7a7b3d2c..c3496c6a91b 100644
--- a/kernel/freezer.c
+++ b/kernel/freezer.c
@@ -52,39 +52,29 @@ bool __refrigerator(bool check_kthr_stop)
/* Hmm, should we be allowed to suspend when there are realtime
processes around? */
bool was_frozen = false;
- long save;
+ long save = current->state;
- /*
- * No point in checking freezing() again - the caller already did.
- * Proceed to enter FROZEN.
- */
- spin_lock_irq(&freezer_lock);
-repeat:
- current->flags |= PF_FROZEN;
- spin_unlock_irq(&freezer_lock);
-
- save = current->state;
pr_debug("%s entered refrigerator\n", current->comm);
- spin_lock_irq(&current->sighand->siglock);
- recalc_sigpending(); /* We sent fake signal, clean it up */
- spin_unlock_irq(&current->sighand->siglock);
-
for (;;) {
set_current_state(TASK_UNINTERRUPTIBLE);
+
+ spin_lock_irq(&freezer_lock);
+ current->flags |= PF_FROZEN;
if (!freezing(current) ||
(check_kthr_stop && kthread_should_stop()))
+ current->flags &= ~PF_FROZEN;
+ spin_unlock_irq(&freezer_lock);
+
+ if (!(current->flags & PF_FROZEN))
break;
was_frozen = true;
schedule();
}
- /* leave FROZEN */
- spin_lock_irq(&freezer_lock);
- if (freezing(current))
- goto repeat;
- current->flags &= ~PF_FROZEN;
- spin_unlock_irq(&freezer_lock);
+ spin_lock_irq(&current->sighand->siglock);
+ recalc_sigpending(); /* We sent fake signal, clean it up */
+ spin_unlock_irq(&current->sighand->siglock);
pr_debug("%s left refrigerator\n", current->comm);