From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753272AbbF1X6j (ORCPT ); Sun, 28 Jun 2015 19:58:39 -0400 Received: from mx1.redhat.com ([209.132.183.28]:37611 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752907AbbF1X6E (ORCPT ); Sun, 28 Jun 2015 19:58:04 -0400 Date: Mon, 29 Jun 2015 01:56:42 +0200 From: Oleg Nesterov To: Peter Zijlstra Cc: paulmck@linux.vnet.ibm.com, tj@kernel.org, mingo@redhat.com, der.herr@hofr.at, dave@stgolabs.net, riel@redhat.com, viro@ZenIV.linux.org.uk, torvalds@linux-foundation.org, linux-kernel@vger.kernel.org Subject: [PATCH 2/3] percpu-rwsem: don't use percpu_rw_semaphore->rw_sem to exclude writers Message-ID: <20150628235642.GA25177@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20150628235614.GA24454@redhat.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org percpu_down_write() does down_write() to exclude both the readers and other writers. We can rely on rcu_sync_enter() in exclusive mode and take ->rw_sem right before wait_event(). Signed-off-by: Oleg Nesterov --- kernel/locking/percpu-rwsem.c | 3 +-- 1 files changed, 1 insertions(+), 2 deletions(-) diff --git a/kernel/locking/percpu-rwsem.c b/kernel/locking/percpu-rwsem.c index 014d2f4..609c13b 100644 --- a/kernel/locking/percpu-rwsem.c +++ b/kernel/locking/percpu-rwsem.c @@ -139,8 +139,6 @@ static bool readers_active_check(struct percpu_rw_semaphore *sem) void percpu_down_write(struct percpu_rw_semaphore *sem) { - down_write(&sem->rw_sem); - /* Notify readers to take the slow path. */ rcu_sync_enter(&sem->rss); @@ -158,6 +156,7 @@ void percpu_down_write(struct percpu_rw_semaphore *sem) * therefore will wait for them. */ + down_write(&sem->rw_sem); /* Wait for all now active readers to complete. */ wait_event(sem->writer, readers_active_check(sem)); } -- 1.5.5.1