From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3182EC43381 for ; Tue, 19 Mar 2019 01:06:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 03A132147C for ; Tue, 19 Mar 2019 01:06:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726616AbfCSBGN (ORCPT ); Mon, 18 Mar 2019 21:06:13 -0400 Received: from mx1.redhat.com ([209.132.183.28]:54960 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726579AbfCSBGN (ORCPT ); Mon, 18 Mar 2019 21:06:13 -0400 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id E883936899; Tue, 19 Mar 2019 01:06:12 +0000 (UTC) Received: from ming.t460p (ovpn-8-18.pek2.redhat.com [10.72.8.18]) by smtp.corp.redhat.com (Postfix) with ESMTPS id C071760C1D; Tue, 19 Mar 2019 01:06:07 +0000 (UTC) Date: Tue, 19 Mar 2019 09:06:02 +0800 From: Ming Lei To: James Smart Cc: Jens Axboe , linux-block@vger.kernel.org, Christoph Hellwig , linux-nvme@lists.infradead.org Subject: Re: [PATCH 1/2] blk-mq: introduce blk_mq_complete_request_sync() Message-ID: <20190319010601.GA22459@ming.t460p> References: <20190318032950.17770-1-ming.lei@redhat.com> <20190318032950.17770-2-ming.lei@redhat.com> <4563485a-02c6-0bfe-d9ec-49adbd44671c@broadcom.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4563485a-02c6-0bfe-d9ec-49adbd44671c@broadcom.com> User-Agent: Mutt/1.9.1 (2017-09-22) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.30]); Tue, 19 Mar 2019 01:06:13 +0000 (UTC) Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Mon, Mar 18, 2019 at 10:37:08AM -0700, James Smart wrote: > > > On 3/17/2019 8:29 PM, Ming Lei wrote: > > In NVMe's error handler, follows the typical steps for tearing down > > hardware: > > > > 1) stop blk_mq hw queues > > 2) stop the real hw queues > > 3) cancel in-flight requests via > > blk_mq_tagset_busy_iter(tags, cancel_request, ...) > > cancel_request(): > > mark the request as abort > > blk_mq_complete_request(req); > > 4) destroy real hw queues > > > > However, there may be race between #3 and #4, because blk_mq_complete_request() > > actually completes the request asynchronously. > > > > This patch introduces blk_mq_complete_request_sync() for fixing the > > above race. > > > > This won't help FC at all. Inherently, the "completion" has to be > asynchronous as line traffic may be required. > > e.g. FC doesn't use nvme_complete_request() in the iterator routine. Yeah, I saw the FC code, it is supposed to address the asynchronous completion of blk_mq_complete_request() in error handler. Also I think it is always the correct thing to abort requests synchronously in error handler, isn't it? thanks, Ming