From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753230AbbIZRdB (ORCPT ); Sat, 26 Sep 2015 13:33:01 -0400 Received: from mail-yk0-f177.google.com ([209.85.160.177]:35459 "EHLO mail-yk0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752957AbbIZRdA (ORCPT ); Sat, 26 Sep 2015 13:33:00 -0400 Date: Sat, 26 Sep 2015 13:32:56 -0400 From: Tejun Heo To: Akinobu Mita Cc: linux-kernel@vger.kernel.org, Jens Axboe , Ming Lei , Christoph Hellwig Subject: Re: [PATCH v4 6/7] blk-mq: fix freeze queue race Message-ID: <20150926173256.GA3572@htj.duckdns.org> References: <1443287365-4244-1-git-send-email-akinobu.mita@gmail.com> <1443287365-4244-7-git-send-email-akinobu.mita@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1443287365-4244-7-git-send-email-akinobu.mita@gmail.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, On Sun, Sep 27, 2015 at 02:09:24AM +0900, Akinobu Mita wrote: > @@ -420,7 +420,9 @@ static void blk_mq_sysfs_init(struct request_queue *q) > /* see blk_register_queue() */ > void blk_mq_finish_init(struct request_queue *q) > { > + mutex_lock(&q->mq_freeze_lock); > percpu_ref_switch_to_percpu(&q->mq_usage_counter); > + mutex_unlock(&q->mq_freeze_lock); This looks weird to me. What can it race against at this point? > @@ -115,11 +115,15 @@ void blk_mq_freeze_queue_start(struct request_queue *q) > { > int freeze_depth; > > + mutex_lock(&q->mq_freeze_lock); > + > freeze_depth = atomic_inc_return(&q->mq_freeze_depth); It doesn't have to be an atomic anymore, right? Thanks. -- tejun