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>

diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
index dadbf88c22c48cea044aac4e34fda9deec78636a..454195194d4a133f2d600d0d3659b2ee5306b7ad 100644 (file)
--- a/kernel/locking/mutex.c
+++ b/kernel/locking/mutex.c
@@ -378,8 +378,14 @@ done:
         * 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;
 }