[PATCH v4 3/5] locking/rwsem: Don't wake up one's own task

From: Waiman Long <Waiman.Long@hpe.com>
To: Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@redhat.com>
Cc: linux-kernel@vger.kernel.org, Davidlohr Bueso <dave@stgolabs.net>,
	Jason Low <jason.low2@hp.com>, Dave Chinner <david@fromorbit.com>,
	Peter Hurley <peter@hurleysoftware.com>,
	"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
	Scott J Norton <scott.norton@hpe.com>,
	Douglas Hatch <doug.hatch@hpe.com>,
	Waiman Long <Waiman.Long@hpe.com>
Subject: [PATCH v4 3/5] locking/rwsem: Don't wake up one's own task
Date: Tue, 17 May 2016 21:26:21 -0400	[thread overview]
Message-ID: <1463534783-38814-4-git-send-email-Waiman.Long@hpe.com> (raw)
In-Reply-To: <1463534783-38814-1-git-send-email-Waiman.Long@hpe.com>

As rwsem_down_read_failed() will queue itself and potentially call
__rwsem_do_wake(sem, RWSEM_WAKE_ANY), it is possible that a reader
will try to wake up its own task. This patch adds a check to make
sure that this won't happen.

Signed-off-by: Waiman Long <Waiman.Long@hpe.com>
Reviewed-by: Peter Hurley <peter@hurleysoftware.com>
---
 kernel/locking/rwsem-xadd.c |    3 ++-
 1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/kernel/locking/rwsem-xadd.c b/kernel/locking/rwsem-xadd.c
index c278f5a..007814f 100644
--- a/kernel/locking/rwsem-xadd.c
+++ b/kernel/locking/rwsem-xadd.c
@@ -202,7 +202,8 @@ __rwsem_do_wake(struct rw_semaphore *sem, enum rwsem_wake_type wake_type)
 		 */
 		smp_mb();
 		waiter->task = NULL;
-		wake_up_process(tsk);
+		if (tsk != current)
+			wake_up_process(tsk);
 		put_task_struct(tsk);
 	} while (--loop);
 
-- 
1.7.1
