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=-5.5 required=3.0 tests=BAYES_00, 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 B5970C433E0 for ; Thu, 30 Jul 2020 15:14:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9B5D820838 for ; Thu, 30 Jul 2020 15:14:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729717AbgG3POH (ORCPT ); Thu, 30 Jul 2020 11:14:07 -0400 Received: from netrider.rowland.org ([192.131.102.5]:54123 "HELO netrider.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1728286AbgG3POG (ORCPT ); Thu, 30 Jul 2020 11:14:06 -0400 Received: (qmail 6915 invoked by uid 1000); 30 Jul 2020 11:14:05 -0400 Date: Thu, 30 Jul 2020 11:14:05 -0400 From: Alan Stern To: Martin Kepplinger Cc: Bart Van Assche , 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: <20200730151405.GC6332@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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jul 30, 2020 at 10:05:50AM +0200, Martin Kepplinger wrote: > On 29.06.20 18:15, Alan Stern wrote: > > On Mon, Jun 29, 2020 at 11:42:59AM +0200, Martin Kepplinger wrote: > >> > >> > >> On 26.06.20 17:44, Alan Stern wrote: > >>> Martin's best approach would be to add some debugging code to find out why > >>> blk_queue_enter() isn't calling bkl_pm_request_resume(), or why that call > >>> doesn't lead to pm_request_resume(). > >>> > >>> Alan Stern > >>> > >> > >> Hi Alan, > >> > >> blk_queue_enter() always - especially when sd is runtime suspended and I > >> try to mount as above - sets success to be true for me, so never > >> continues down to bkl_pm_request_resume(). All I see is "PM: Removing > >> info for No Bus:sda1". > > > > Aha. Looking at this more closely, it's apparent that the code in > > blk-core.c contains a logic bug: It assumes that if the BLK_MQ_REQ_PREEMPT > > flag is set then the request can be issued regardless of the queue's > > runtime status. That is not correct when the queue is suspended. > > > > Below is my attempt to fix this up. I'm not sure that the patch is > > entirely correct, but it should fix this logic bug. I would appreciate a > > critical review. > > > > Martin, does this fix the problem? > > > > Alan Stern > > Hi Alan, > > So in the block layer your change below indeed fixes the problem and if > you want to submit that 1:1 feel free to add > > Tested-by: Martin Kepplinger > > thanks for your help in this! Thank you for _your_ help! The next merge window is coming up soon. I think I'll wait until it is over before submitting the patch (maintainers tend to be too busy to consider new patches during a merge window). But I am still open to comments or criticism of the patch in the meantime. There hasn't been any feedback since Bart's initial set of questions. Alan Stern