From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751154AbcEIFAB (ORCPT ); Mon, 9 May 2016 01:00:01 -0400 Received: from smtp2.provo.novell.com ([137.65.250.81]:46359 "EHLO smtp2.provo.novell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751120AbcEIFAA (ORCPT ); Mon, 9 May 2016 01:00:00 -0400 From: Davidlohr Bueso To: mingo@kernel.org, peterz@infradead.org, tglx@linutronix.de Cc: Waiman.Long@hpe.com, jason.low2@hp.com, dave@stgolabs.net, linux-kernel@vger.kernel.org, Davidlohr Bueso Subject: [PATCH 1/4] locking/rwsem: Avoid stale ->count for rwsem_down_write_failed() Date: Sun, 8 May 2016 21:56:07 -0700 Message-Id: <1462769770-29363-2-git-send-email-dave@stgolabs.net> X-Mailer: git-send-email 2.8.1 In-Reply-To: <1462769770-29363-1-git-send-email-dave@stgolabs.net> References: <1462769770-29363-1-git-send-email-dave@stgolabs.net> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The field is obviously updated w.o the lock and needs a READ_ONCE while waiting for lock holder(s) to go away, just like we do with all other ->count accesses. Signed-off-by: Davidlohr Bueso --- kernel/locking/rwsem-xadd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/locking/rwsem-xadd.c b/kernel/locking/rwsem-xadd.c index df4dcb883b50..7d62772600cf 100644 --- a/kernel/locking/rwsem-xadd.c +++ b/kernel/locking/rwsem-xadd.c @@ -494,7 +494,7 @@ __rwsem_down_write_failed_common(struct rw_semaphore *sem, int state) } schedule(); set_current_state(state); - } while ((count = sem->count) & RWSEM_ACTIVE_MASK); + } while ((count = READ_ONCE(sem->count)) & RWSEM_ACTIVE_MASK); raw_spin_lock_irq(&sem->wait_lock); } -- 2.8.1