Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933461Ab3EGNqP (ORCPT ); Tue, 7 May 2013 09:46:15 -0400 Received: from mail-da0-f53.google.com ([209.85.210.53]:55035 "EHLO mail-da0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933350Ab3EGNqK (ORCPT ); Tue, 7 May 2013 09:46:10 -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 02/14] rwsem: shorter spinlocked section in rwsem_down_failed_common() Date: Tue, 7 May 2013 06:45:50 -0700 Message-Id: <1367934362-10433-3-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: 2030 Lines: 64 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 Reviewed-by: Rik van Riel Reviewed-by: Peter Hurley Acked-by: Davidlohr Bueso --- 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; -- 1.8.2.1 -- 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/