Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933601Ab3EGNsb (ORCPT ); Tue, 7 May 2013 09:48:31 -0400 Received: from mail-da0-f42.google.com ([209.85.210.42]:54829 "EHLO mail-da0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933558Ab3EGNq2 (ORCPT ); Tue, 7 May 2013 09:46:28 -0400 From: Michel Lespinasse To: Linus Torvalds , David Howells , Peter Zijlstra , Ingo Molnar , Rik van Riel , Davidlohr Bueso , Peter Hurley Cc: Alex Shi , Yuanhan Liu , Andrew Morton , linux-kernel@vger.kernel.org Subject: [PATCH v3 08/14] rwsem: avoid taking wait_lock in rwsem_down_write_failed Date: Tue, 7 May 2013 06:45:56 -0700 Message-Id: <1367934362-10433-9-git-send-email-walken@google.com> X-Mailer: git-send-email 1.8.2.1 In-Reply-To: <1367934362-10433-1-git-send-email-walken@google.com> References: <1367934362-10433-1-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: 1600 Lines: 49 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 Reviewed-by: Peter Hurley Acked-by: Davidlohr Bueso Acked-by: Rik van Riel --- 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); } -- 1.8.2.1 -- 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/