From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754487AbeDBV4r (ORCPT ); Mon, 2 Apr 2018 17:56:47 -0400 Received: from esa1.hgst.iphmx.com ([68.232.141.245]:37604 "EHLO esa1.hgst.iphmx.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753256AbeDBV4p (ORCPT ); Mon, 2 Apr 2018 17:56:45 -0400 X-IronPort-AV: E=Sophos;i="5.48,397,1517846400"; d="scan'208";a="178122998" From: Bart Van Assche To: "tj@kernel.org" CC: "kernel-team@fb.com" , "linux-kernel@vger.kernel.org" , "linux-block@vger.kernel.org" , "axboe@kernel.dk" Subject: Re: [PATCH 2/2] blk-mq: Fix request handover from timeout path to normal execution Thread-Topic: [PATCH 2/2] blk-mq: Fix request handover from timeout path to normal execution Thread-Index: AQHTyrUNkNkjnUv7yk+FmjLOLTu6JKPt+B6AgAAAm4CAAAzSAA== Date: Mon, 2 Apr 2018 21:56:41 +0000 Message-ID: References: <20180402190053.GC388343@devbig577.frc2.facebook.com> <20180402190120.GD388343@devbig577.frc2.facebook.com> <20180402211047.GF388343@devbig577.frc2.facebook.com> In-Reply-To: <20180402211047.GF388343@devbig577.frc2.facebook.com> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: spf=none (sender IP is ) smtp.mailfrom=Bart.VanAssche@wdc.com; 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x-microsoft-antispam-message-info: 8Ocnzt/TE9G/FS10MXoYgBJIIwPHHpSNBS7TepYDAIresIxjPjNdsNL62UOVsghlJNnd0ky+XusAqWbvMoqerxF1+nJs8pkoZt28u7CxlCRuPPmTH6Kt372HXfTmfF5FInZ29jZxHfc/TmfCgJfvyfQhF009kG2xVL6nBtawACYKfSdDPtb+C+9pn165DczUeVAgU0vrMOO2keC/v8RQA/O1SP6FRo6HY9qDp+85C9sVqmb+w97/A+lmDmLLFVjmagECOg56tNhO539rp4OUb+F89AI/HvVMCArTh3qynluenZnt0ZQxLIZxt4WIvFirlFQC1WMPM4TVFv9drmvUNIsLFVs54rNuVFw+Xdf73GqpDtQs4cAMAOB4t3fEr4oRhGACnYDBJLpIxqG6RmF4nHQ5HqUx6fagcRM+wbHjOpE= spamdiagnosticoutput: 1:99 spamdiagnosticmetadata: NSPM Content-Type: text/plain; charset="utf-8" Content-ID: MIME-Version: 1.0 X-OriginatorOrg: wdc.com X-MS-Exchange-CrossTenant-Network-Message-Id: 8a4c2ac6-367f-4f33-9a5c-08d598e49e1e X-MS-Exchange-CrossTenant-originalarrivaltime: 02 Apr 2018 21:56:41.3533 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: b61c8803-16f3-4c35-9b17-6f65f441df86 X-MS-Exchange-Transport-CrossTenantHeadersStamped: MWHPR04MB0734 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from base64 to 8bit by mail.home.local id w32Lurpq021715 On Mon, 2018-04-02 at 14:10 -0700, Tejun Heo wrote: > On Mon, Apr 02, 2018 at 02:08:37PM -0700, Bart Van Assche wrote: > > On 04/02/18 12:01, Tejun Heo wrote: > > > + * As nothing prevents from completion happening while > > > + * ->aborted_gstate is set, this may lead to ignored completions > > > + * and further spurious timeouts. > > > + */ > > > + if (rq->rq_flags & RQF_MQ_TIMEOUT_RESET) > > > + blk_mq_rq_update_aborted_gstate(rq, 0); > > > > Hello Tejun, > > > > Since this patch fixes one race but introduces another race, is this > > patch really an improvement? > > Oh, that's not a new race. That's the same non-critical race which > always existed. It's just being documented. This patch increases the time during which .aborted_gstate == .gstate if the timeout is reset. Does that increase the chance that a completion will be missed if the request timeout is reset? Thanks, Bart.