From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756509AbaIQQoG (ORCPT ); Wed, 17 Sep 2014 12:44:06 -0400 Received: from verein.lst.de ([213.95.11.211]:39884 "EHLO newverein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756334AbaIQQoE (ORCPT ); Wed, 17 Sep 2014 12:44:04 -0400 Date: Wed, 17 Sep 2014 18:44:00 +0200 From: Christoph Hellwig To: Ming Lei Cc: Jens Axboe , linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] blk-mq: fix race between timeout and queue_rq Message-ID: <20140917164400.GA18472@lst.de> References: <1410947278-15733-1-git-send-email-ming.lei@canonical.com> <1410947278-15733-2-git-send-email-ming.lei@canonical.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1410947278-15733-2-git-send-email-ming.lei@canonical.com> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 17, 2014 at 05:47:57PM +0800, Ming Lei wrote: > Either the request is from requeue or just being allocated from > tag pool, its REQ_ATOM_STARTED flag has been cleared already, so > don't test it in blk_mq_start_request(). > > One memory barrier is needed between writing rq->deadline and > setting REQ_ATOM_STARTED so that timeout can't happen too early > if timeout handler reads obsolete rq->deadline caused by out > of order of the two writes. Looks reasonable to me, Reviewed-by: Christoph Hellwig