Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932220Ab3CFXXP (ORCPT ); Wed, 6 Mar 2013 18:23:15 -0500 Received: from mail-pb0-f46.google.com ([209.85.160.46]:49765 "EHLO mail-pb0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757569Ab3CFXWL (ORCPT ); Wed, 6 Mar 2013 18:22:11 -0500 From: Michel Lespinasse To: Alex Shi , Ingo Molnar , David Howells , Peter Zijlstra , Thomas Gleixner , Yuanhan Liu , Rik van Riel Cc: Andrew Morton , linux-kernel@vger.kernel.org Subject: [PATCH 08/12] rwsem: avoid taking wait_lock in rwsem_down_write_failed Date: Wed, 6 Mar 2013 15:21:47 -0800 Message-Id: <1362612111-28673-9-git-send-email-walken@google.com> X-Mailer: git-send-email 1.8.1.3 In-Reply-To: <1362612111-28673-1-git-send-email-walken@google.com> References: <1362612111-28673-1-git-send-email-walken@google.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1455 Lines: 46 In rwsem_down_write_failed(), if there are active locks after we wake up (i.e. the lock got stolen from us), skip taking the wait_lock and go back to sleep immediately. Signed-off-by: Michel Lespinasse --- lib/rwsem.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/lib/rwsem.c b/lib/rwsem.c index 64c2dc007be2..edf3d9ca670e 100644 --- a/lib/rwsem.c +++ b/lib/rwsem.c @@ -214,8 +214,8 @@ struct rw_semaphore __sched *rwsem_down_write_failed(struct rw_semaphore *sem) sem = __rwsem_do_wake(sem, RWSEM_WAKE_READ_OWNED); /* wait until we successfully acquire the lock */ + set_task_state(tsk, TASK_UNINTERRUPTIBLE); while (true) { - set_task_state(tsk, TASK_UNINTERRUPTIBLE); /* Try acquiring the write lock. */ count = RWSEM_ACTIVE_WRITE_BIAS; @@ -226,7 +226,13 @@ struct rw_semaphore __sched *rwsem_down_write_failed(struct rw_semaphore *sem) break; raw_spin_unlock_irq(&sem->wait_lock); - schedule(); + + /* Block until there are no active lockers. */ + do { + schedule(); + set_task_state(tsk, TASK_UNINTERRUPTIBLE); + } while (sem->count & RWSEM_ACTIVE_MASK); + raw_spin_lock_irq(&sem->wait_lock); } -- 1.8.1.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/