Commit 6f942a1f authored Sep 24, 2014 by Peter Zijlstra Committed by Ingo Molnar Oct 28, 2014

locking/mutex: Don't assume TASK_RUNNING



We're going to make might_sleep() test for TASK_RUNNING, because
blocking without TASK_RUNNING will destroy the task state by setting
it to TASK_RUNNING.

There are a few occasions where its 'valid' to call blocking
primitives (and mutex_lock in particular) and not have TASK_RUNNING,
typically such cases are right before we set TASK_RUNNING anyhow.

Robustify the code by not assuming this; this has the beneficial side
effect of allowing optional code emission for fixing the above
might_sleep() false positives.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: tglx@linutronix.de
Cc: ilya.dryomov@inktank.com
Cc: umgwanakikbuti@gmail.com
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20140924082241.988560063@infradead.org


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent f4e9d94a

kernel/locking/mutex.c

+7 −1

Original line number	Diff line number	Diff line
		@@ -378,8 +378,14 @@ static bool mutex_optimistic_spin(struct mutex *lock,
		* reschedule now, before we try-lock the mutex. This avoids getting
		* scheduled out right after we obtained the mutex.
		*/
		if (need_resched())
		if (need_resched()) {
		/*
		* We _should_ have TASK_RUNNING here, but just in case
		* we do not, make it so, otherwise we might get stuck.
		*/
		__set_current_state(TASK_RUNNING);
		schedule_preempt_disabled();
		}

		return false;
		}