Commit 5ece3eae authored by Tejun Heo's avatar Tejun Heo
Browse files

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: default avatarTejun Heo <tj@kernel.org>
Reported-by: default avatarOleg Nesterov <oleg@redhat.com>
Acked-by: default avatarOleg Nesterov <oleg@redhat.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>
parent 96ee6d85

kernel/freezer.c

+11 −21
Original line number Diff line number Diff line
@@ -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);

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