From 5ece3eae4cdb968c269e0bc7e2c0e2b223552025 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Mon, 21 Nov 2011 12:32:26 -0800 Subject: [PATCH] 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 Reported-by: Oleg Nesterov Acked-by: Oleg Nesterov Cc: "Rafael J. Wysocki" --- kernel/freezer.c | 32 +++++++++++--------------------- 1 file changed, 11 insertions(+), 21 deletions(-) diff --git a/kernel/freezer.c b/kernel/freezer.c index b1e7a7b3d2cd..c3496c6a91b2 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(¤t->sighand->siglock); - recalc_sigpending(); /* We sent fake signal, clean it up */ - spin_unlock_irq(¤t->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(¤t->sighand->siglock); + recalc_sigpending(); /* We sent fake signal, clean it up */ + spin_unlock_irq(¤t->sighand->siglock); pr_debug("%s left refrigerator\n", current->comm); -- 2.39.2