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=-6.1 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,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 1B29DC433E7 for ; Sat, 29 Aug 2020 02:57:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 03BF7208CA for ; Sat, 29 Aug 2020 02:57:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726584AbgH2C54 (ORCPT ); Fri, 28 Aug 2020 22:57:56 -0400 Received: from mail-pj1-f67.google.com ([209.85.216.67]:34335 "EHLO mail-pj1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726462AbgH2C5y (ORCPT ); Fri, 28 Aug 2020 22:57:54 -0400 Received: by mail-pj1-f67.google.com with SMTP id n3so464331pjq.1; Fri, 28 Aug 2020 19:57:53 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:autocrypt :message-id:date:user-agent:mime-version:in-reply-to :content-language:content-transfer-encoding; bh=OqUGPUYdN7PULuDA/9YzFTy96hztr5ZfPQ1srP/K7ws=; b=q2AGikpOu3FvfRKzSk4kT5gdTtd8qZCQ1OWModG9GveA1N+e3eLiD8C/zz6+GyGA6H izc8q/n+v1F6XpF4BZDmF0vzbHWAAVLoE6p4T9EKtDnDK0rFiOECSFuM5je/0QLRegN4 Ek1/EyJQLKThZxcovCRpQJxJVklIeMYL/4ShB10dOEyGntaRBr1I5A49rAmKa+sgFHC9 0PNXw9j1wn0d0D0D5EpNlK6BjoSMyHg6Dqg8eTOaAi+8EYH43nrzE1PYHXDHcOSbNvTl GbqSZTO/BHl/Ck+5l/2Vxeapsv59TKXhcgGc0LdBP1x08YnUIIK7CEI3JaAumtkE0La8 Fh5g== X-Gm-Message-State: AOAM530z5yQ3NbWg2r1taE6KqmnHda0IRlDXfOZCFaG2iBwrEe66Nz5P 61wTUjpBCpT3rUnXT3sZyOBDruqXZ3g= X-Google-Smtp-Source: ABdhPJzc12rnL+4Y6fTQZ0ErNqLeLKKxhhDYfDr+ujFhlxMtSuQkGAJ9tNTp/t8eMx7hIAWTn/Kg+w== X-Received: by 2002:a17:90a:bc48:: with SMTP id t8mr1643027pjv.224.1598669873065; Fri, 28 Aug 2020 19:57:53 -0700 (PDT) Received: from [192.168.3.217] (c-73-241-217-19.hsd1.ca.comcast.net. [73.241.217.19]) by smtp.gmail.com with ESMTPSA id gv21sm584500pjb.39.2020.08.28.19.57.51 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 28 Aug 2020 19:57:52 -0700 (PDT) Subject: Re: [PATCH] block: Fix a race in the runtime power management code To: Alan Stern Cc: Stanley Chu , Jens Axboe , linux-block@vger.kernel.org, Christoph Hellwig , Ming Lei , stable , Can Guo , "Martin K. Petersen" , SCSI development list References: <20200824030607.19357-1-bvanassche@acm.org> <1598346681.10649.8.camel@mtkswgap22> <20200825182423.GB375466@rowland.harvard.edu> <1f798c21-241f-59f8-5298-a32fffe2ff01@acm.org> <20200826015159.GA387575@rowland.harvard.edu> <20200827203321.GB449067@rowland.harvard.edu> <5da883fe-b5ec-b98d-ae0c-bc053b6e22cb@acm.org> <20200828153745.GB470612@rowland.harvard.edu> <31d6f204-21ae-88da-dbfc-3d7132f8bc03@acm.org> <20200829011203.GA486691@rowland.harvard.edu> From: Bart Van Assche Autocrypt: addr=bvanassche@acm.org; prefer-encrypt=mutual; keydata= mQENBFSOu4oBCADcRWxVUvkkvRmmwTwIjIJvZOu6wNm+dz5AF4z0FHW2KNZL3oheO3P8UZWr LQOrCfRcK8e/sIs2Y2D3Lg/SL7qqbMehGEYcJptu6mKkywBfoYbtBkVoJ/jQsi2H0vBiiCOy fmxMHIPcYxaJdXxrOG2UO4B60Y/BzE6OrPDT44w4cZA9DH5xialliWU447Bts8TJNa3lZKS1 AvW1ZklbvJfAJJAwzDih35LxU2fcWbmhPa7EO2DCv/LM1B10GBB/oQB5kvlq4aA2PSIWkqz4 3SI5kCPSsygD6wKnbRsvNn2mIACva6VHdm62A7xel5dJRfpQjXj2snd1F/YNoNc66UUTABEB AAG0JEJhcnQgVmFuIEFzc2NoZSA8YnZhbmFzc2NoZUBhY20ub3JnPokBOQQTAQIAIwUCVI67 igIbAwcLCQgHAwIBBhUIAgkKCwQWAgMBAh4BAheAAAoJEHFcPTXFzhAJ8QkH/1AdXblKL65M Y1Zk1bYKnkAb4a98LxCPm/pJBilvci6boefwlBDZ2NZuuYWYgyrehMB5H+q+Kq4P0IBbTqTa jTPAANn62A6jwJ0FnCn6YaM9TZQjM1F7LoDX3v+oAkaoXuq0dQ4hnxQNu792bi6QyVdZUvKc macVFVgfK9n04mL7RzjO3f+X4midKt/s+G+IPr4DGlrq+WH27eDbpUR3aYRk8EgbgGKvQFdD CEBFJi+5ZKOArmJVBSk21RHDpqyz6Vit3rjep7c1SN8s7NhVi9cjkKmMDM7KYhXkWc10lKx2 RTkFI30rkDm4U+JpdAd2+tP3tjGf9AyGGinpzE2XY1K5AQ0EVI67igEIAKiSyd0nECrgz+H5 PcFDGYQpGDMTl8MOPCKw/F3diXPuj2eql4xSbAdbUCJzk2ETif5s3twT2ER8cUTEVOaCEUY3 eOiaFgQ+nGLx4BXqqGewikPJCe+UBjFnH1m2/IFn4T9jPZkV8xlkKmDUqMK5EV9n3eQLkn5g lco+FepTtmbkSCCjd91EfThVbNYpVQ5ZjdBCXN66CKyJDMJ85HVr5rmXG/nqriTh6cv1l1Js T7AFvvPjUPknS6d+BETMhTkbGzoyS+sywEsQAgA+BMCxBH4LvUmHYhpS+W6CiZ3ZMxjO8Hgc ++w1mLeRUvda3i4/U8wDT3SWuHcB3DWlcppECLkAEQEAAYkBHwQYAQIACQUCVI67igIbDAAK CRBxXD01xc4QCZ4dB/0QrnEasxjM0PGeXK5hcZMT9Eo998alUfn5XU0RQDYdwp6/kMEXMdmT oH0F0xB3SQ8WVSXA9rrc4EBvZruWQ+5/zjVrhhfUAx12CzL4oQ9Ro2k45daYaonKTANYG22y //x8dLe2Fv1By4SKGhmzwH87uXxbTJAUxiWIi1np0z3/RDnoVyfmfbbL1DY7zf2hYXLLzsJR mSsED/1nlJ9Oq5fALdNEPgDyPUerqHxcmIub+pF0AzJoYHK5punqpqfGmqPbjxrJLPJfHVKy goMj5DlBMoYqEgpbwdUYkH6QdizJJCur4icy8GUNbisFYABeoJ91pnD4IGei3MTdvINSZI5e Message-ID: <874cc075-5990-bd37-10e5-6456c1c324ac@acm.org> Date: Fri, 28 Aug 2020 19:57:50 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: <20200829011203.GA486691@rowland.harvard.edu> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On 2020-08-28 18:12, Alan Stern wrote: > On Fri, Aug 28, 2020 at 05:51:03PM -0700, Bart Van Assche wrote: >> On 2020-08-28 08:37, Alan Stern wrote: >>> There may be an even simpler solution: Ensure that SCSI domain >>> validation is mutually exclusive with runtime PM. It's already mutually >>> exclusive with system PM, so this makes sense. >>> >>> What do you think of the patch below? >>> >>> Alan Stern >>> >>> >>> Index: usb-devel/drivers/scsi/scsi_transport_spi.c >>> =================================================================== >>> --- usb-devel.orig/drivers/scsi/scsi_transport_spi.c >>> +++ usb-devel/drivers/scsi/scsi_transport_spi.c >>> @@ -1001,7 +1001,7 @@ spi_dv_device(struct scsi_device *sdev) >>> * Because this function and the power management code both call >>> * scsi_device_quiesce(), it is not safe to perform domain validation >>> * while suspend or resume is in progress. Hence the >>> - * lock/unlock_system_sleep() calls. >>> + * lock/unlock_system_sleep() and scsi_autopm_get/put_device() calls. >>> */ >>> lock_system_sleep(); >>> >>> @@ -1018,10 +1018,13 @@ spi_dv_device(struct scsi_device *sdev) >>> if (unlikely(!buffer)) >>> goto out_put; >>> >>> + if (scsi_autopm_get_device(sdev)) >>> + goto out_free; >>> + >>> /* We need to verify that the actual device will quiesce; the >>> * later target quiesce is just a nice to have */ >>> if (unlikely(scsi_device_quiesce(sdev))) >>> - goto out_free; >>> + goto out_autopm_put; >>> >>> scsi_target_quiesce(starget); >>> >>> @@ -1041,6 +1044,8 @@ spi_dv_device(struct scsi_device *sdev) >>> >>> spi_initial_dv(starget) = 1; >>> >>> + out_autopm_put: >>> + scsi_autopm_put_device(sdev); >>> out_free: >>> kfree(buffer); >>> out_put: >> >> Hi Alan, >> >> I think this is only a part of the solution. scsi_target_quiesce() invokes >> scsi_device_quiesce() and that function in turn calls blk_set_pm_only(). So >> I think that the above is not sufficient to fix the deadlock mentioned in >> my previous email. > > Sorry, it sounds like you misinterpreted my preceding email. I meant to > suggest that the patch above should be considered _instead of_ the patch > that introduced BLK_MQ_REQ_PM. So blk_queue_enter() would remain > unchanged, using the BLK_MQ_REQ_PREEMPT flag to decide whether or not to > postpone new requests. Thus the deadlock you're concerned about would > not arise. Hi Alan, Thanks for the clarification. I agree that the above patch should serialize SCSI DV and runtime PM. I'm fine with the above patch. Thanks, Bart.