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_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 24B99C433E1 for ; Tue, 30 Jun 2020 19:38:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F211B2067D for ; Tue, 30 Jun 2020 19:38:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728191AbgF3TiE (ORCPT ); Tue, 30 Jun 2020 15:38:04 -0400 Received: from netrider.rowland.org ([192.131.102.5]:33883 "HELO netrider.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1728166AbgF3TiE (ORCPT ); Tue, 30 Jun 2020 15:38:04 -0400 Received: (qmail 464162 invoked by uid 1000); 30 Jun 2020 15:38:02 -0400 Date: Tue, 30 Jun 2020 15:38:02 -0400 From: Alan Stern To: Bart Van Assche Cc: Martin Kepplinger , jejb@linux.ibm.com, Can Guo , martin.petersen@oracle.com, linux-scsi@vger.kernel.org, linux-kernel@vger.kernel.org, kernel@puri.sm Subject: Re: [PATCH] scsi: sd: add runtime pm to open / release Message-ID: <20200630193802.GA463609@rowland.harvard.edu> References: <20200623111018.31954-1-martin.kepplinger@puri.sm> <1379e21d-c51a-3710-e185-c2d7a9681fb7@acm.org> <20200626154441.GA296771@rowland.harvard.edu> <20200629161536.GA405175@rowland.harvard.edu> <5231c57d-3f4e-1853-d4d5-cf7f04a32246@acm.org> <20200630180255.GA459638@rowland.harvard.edu> <1804723c-4aaf-a820-d3ef-e70125017cad@acm.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1804723c-4aaf-a820-d3ef-e70125017cad@acm.org> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-scsi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org On Tue, Jun 30, 2020 at 12:23:12PM -0700, Bart Van Assche wrote: > On 2020-06-30 11:02, Alan Stern wrote: > > Right now there doesn't seem to be any mechanism for resuming the queue > > if an REQ_PREEMPT request is added while the queue is suspended. > > I do not agree with the above statement. My understanding is that resuming > happens as follows if a request is submitted against a runtime suspended > queue owned by a SCSI LLD: > > blk_queue_enter() > -> blk_pm_request_resume() Assume that BLK_MQ_REQ_PREEMPT is set in flags. Then where exactly does blk_queue_enter(q, flags) call blk_pm_request_resume(q)? Nowhere, as far as I can see. Alan Stern > -> pm_request_resume(dev) > -> __pm_runtime_resume(dev, RPM_ASYNC) > -> rpm_resume(dev, RPM_ASYNC) > -> dev->power.request = RPM_REQ_RESUME; > -> queue_work(pm_wq, &dev->power.work) > -> pm_runtime_work() > -> rpm_resume(dev, RPM_NOWAIT) > -> callback = scsi_runtime_resume; > -> rpm_callback(callback, dev); > -> scsi_runtime_resume(dev); > -> sdev_runtime_resume(dev); > -> blk_pre_runtime_resume(sdev->request_queue); > -> q->rpm_status = RPM_RESUMING; > -> sd_resume(dev); > -> sd_start_stop_device(sdkp); > -> sd_pm_ops.runtime_resume == scsi_execute(sdp, START); > -> blk_get_request(..., ..., BLK_MQ_REQ_PREEMPT) > -> blk_mq_alloc_request() > -> blk_queue_enter() > -> __blk_mq_alloc_request() > -> blk_execute_rq() > -> blk_put_request() > -> blk_post_runtime_resume(sdev->request_queue); > -> q->rpm_status = RPM_ACTIVE; > -> pm_runtime_mark_last_busy(q->dev); > -> pm_request_autosuspend(q->dev); > > Bart.