From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932891AbaEPPc6 (ORCPT ); Fri, 16 May 2014 11:32:58 -0400 Received: from mail-ie0-f177.google.com ([209.85.223.177]:38708 "EHLO mail-ie0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932695AbaEPPc4 (ORCPT ); Fri, 16 May 2014 11:32:56 -0400 Message-ID: <53762FA5.6040203@kernel.dk> Date: Fri, 16 May 2014 09:32:53 -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 v1] virtio_blk: fix race between start and stop queue References: <1400254281-11294-1-git-send-email-tom.leiming@gmail.com> In-Reply-To: <1400254281-11294-1-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 2014-05-16 09:31, 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. Thanks, this looks good, I'll apply it for 3.16 (with a stable marker, even if it is an unlikely event). -- Jens Axboe