Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932097Ab3CFXWE (ORCPT ); Wed, 6 Mar 2013 18:22:04 -0500 Received: from mail-pb0-f51.google.com ([209.85.160.51]:56362 "EHLO mail-pb0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757206Ab3CFXV7 (ORCPT ); Wed, 6 Mar 2013 18:21:59 -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 02/12] rwsem: shorter spinlocked section in rwsem_down_failed_common() Date: Wed, 6 Mar 2013 15:21:41 -0800 Message-Id: <1362612111-28673-3-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: 1882 Lines: 61 This change reduces the size of the spinlocked and TASK_UNINTERRUPTIBLE sections in rwsem_down_failed_common(): - We only need the sem->wait_lock to insert ourselves on the wait_list; the waiter node can be prepared outside of the wait_lock. - The task state only needs to be set to TASK_UNINTERRUPTIBLE immediately before checking if we actually need to sleep; it doesn't need to protect the entire function. Signed-off-by: Michel Lespinasse --- lib/rwsem.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) diff --git a/lib/rwsem.c b/lib/rwsem.c index 672eb33218ac..40636454cf3c 100644 --- a/lib/rwsem.c +++ b/lib/rwsem.c @@ -188,14 +188,12 @@ rwsem_down_failed_common(struct rw_semaphore *sem, struct task_struct *tsk = current; signed long count; - set_task_state(tsk, TASK_UNINTERRUPTIBLE); - /* set up my own style of waitqueue */ - raw_spin_lock_irq(&sem->wait_lock); waiter.task = tsk; waiter.type = type; get_task_struct(tsk); + raw_spin_lock_irq(&sem->wait_lock); if (list_empty(&sem->wait_list)) adjustment += RWSEM_WAITING_BIAS; list_add_tail(&waiter.list, &sem->wait_list); @@ -218,7 +216,8 @@ rwsem_down_failed_common(struct rw_semaphore *sem, raw_spin_unlock_irq(&sem->wait_lock); /* wait to be given the lock */ - for (;;) { + while (true) { + set_task_state(tsk, TASK_UNINTERRUPTIBLE); if (!waiter.task) break; @@ -231,7 +230,6 @@ rwsem_down_failed_common(struct rw_semaphore *sem, } raw_spin_unlock_irq(&sem->wait_lock); schedule(); - set_task_state(tsk, TASK_UNINTERRUPTIBLE); } tsk->state = TASK_RUNNING; -- 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/