From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757444AbaEPOx1 (ORCPT ); Fri, 16 May 2014 10:53:27 -0400 Received: from mail-ig0-f181.google.com ([209.85.213.181]:41497 "EHLO mail-ig0-f181.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757324AbaEPOxZ (ORCPT ); Fri, 16 May 2014 10:53:25 -0400 Message-ID: <53762662.2050702@kernel.dk> Date: Fri, 16 May 2014 08:53:22 -0600 From: Jens Axboe User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.4.0 MIME-Version: 1.0 To: Ming Lei , linux-kernel@vger.kernel.org CC: Rusty Russell Subject: Re: [PATCH] virtio_blk: fix race between start and stop queue References: <1400157181-17800-1-git-send-email-tom.leiming@gmail.com> In-Reply-To: <1400157181-17800-1-git-send-email-tom.leiming@gmail.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2014-05-15 06:33, Ming Lei wrote: > When there isn't enough vring descriptor for adding to vq, > blk-mq will be put as stopped state until some of pending > descriptors are completed & freed. > > Unfortunately, the vq's interrupt may come just before > blk-mq's BLK_MQ_S_STOPPED flag is set, so the blk-mq will > still be kept as stopped even though lots of descriptors > are completed and freed in the interrupt handler. The worst > case is that all pending descriptors are freed in the > interrupt handler, and the queue is kept as stopped forever. > > This patch fixes the problem by starting/stopping blk-mq > with holding vq_lock. Why not just use blk_mq_start_hw_queues()? -- Jens Axboe