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=-7.0 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 88879C433E2 for ; Fri, 28 Aug 2020 03:27:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6E811208E4 for ; Fri, 28 Aug 2020 03:27:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727892AbgH1D1x (ORCPT ); Thu, 27 Aug 2020 23:27:53 -0400 Received: from mail-pj1-f68.google.com ([209.85.216.68]:39642 "EHLO mail-pj1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726803AbgH1D1x (ORCPT ); Thu, 27 Aug 2020 23:27:53 -0400 Received: by mail-pj1-f68.google.com with SMTP id s2so3047031pjr.4; Thu, 27 Aug 2020 20:27:52 -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=ZNfdUVEKwoE3V2VlwICXVLqoeLGJj5IiBXaUyBDGtyM=; b=QmDPv0aXpcqwghy/xmncoqEbREjNKe1BV3JXPo58sCOQ+SIIeSp+7SBuZtTRUT/mmR ZlD4mXX/XukP7EbQRqUElg1T24ketOIQaHNSjwxsO7d9AySfePGj94/g50FA43w61EtU oWMmu6eTxWqmOy5oe+grxDuFsDlyrzmiFwcG6K64IdgnKDwTmMKxe1nFbsyXAlsIuSUw acM8SRbISLvL0EJCu/jw5WR74la7o05kNKwChaYCP6zst76p1VEnRcImqAT9ko6roZ+U RPx1HXJagKZctYhDD44/nK6d5MscnG2fQMZ5g+GBTQ17nS0UO3FVwrdQoP9UTOXSF4gS 8/fQ== X-Gm-Message-State: AOAM532KCo1YkPIAU7Hy5EftwIV6BI5giab8hfMe3aeDUzXoEyhl28eo k+UmVwyYydIqUhbyLbYuV0S0BhIcx2M= X-Google-Smtp-Source: ABdhPJwQcAdgU/gF60fp0y/dwv4ha89SyKaP823HuRtEjDju89cVtMsLjgVwAqUPK2t11hedEj7Whg== X-Received: by 2002:a17:90a:fe83:: with SMTP id co3mr670556pjb.157.1598585272180; Thu, 27 Aug 2020 20:27:52 -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 w3sm4570478pff.56.2020.08.27.20.27.50 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 27 Aug 2020 20:27:51 -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" 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> 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: <5da883fe-b5ec-b98d-ae0c-bc053b6e22cb@acm.org> Date: Thu, 27 Aug 2020 20:27:49 -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: <20200827203321.GB449067@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 2020-08-27 13:33, Alan Stern wrote: > It may not need to be that complicated. what about something like this? > > Index: usb-devel/block/blk-core.c > =================================================================== > --- usb-devel.orig/block/blk-core.c > +++ usb-devel/block/blk-core.c > @@ -420,11 +420,11 @@ EXPORT_SYMBOL(blk_cleanup_queue); > /** > * blk_queue_enter() - try to increase q->q_usage_counter > * @q: request queue pointer > - * @flags: BLK_MQ_REQ_NOWAIT and/or BLK_MQ_REQ_PREEMPT > + * @flags: BLK_MQ_REQ_NOWAIT and/or BLK_MQ_REQ_PM > */ > int blk_queue_enter(struct request_queue *q, blk_mq_req_flags_t flags) > { > - const bool pm = flags & BLK_MQ_REQ_PREEMPT; > + const bool pm = flags & BLK_MQ_REQ_PM; > > while (true) { > bool success = false; > @@ -626,7 +626,8 @@ struct request *blk_get_request(struct r > struct request *req; > > WARN_ON_ONCE(op & REQ_NOWAIT); > - WARN_ON_ONCE(flags & ~(BLK_MQ_REQ_NOWAIT | BLK_MQ_REQ_PREEMPT)); > + WARN_ON_ONCE(flags & ~(BLK_MQ_REQ_NOWAIT | BLK_MQ_REQ_PREEMPT | > + BLK_MQ_REQ_PM)); > > req = blk_mq_alloc_request(q, op, flags); > if (!IS_ERR(req) && q->mq_ops->initialize_rq_fn) > Index: usb-devel/drivers/scsi/scsi_lib.c > =================================================================== > --- usb-devel.orig/drivers/scsi/scsi_lib.c > +++ usb-devel/drivers/scsi/scsi_lib.c > @@ -245,11 +245,15 @@ int __scsi_execute(struct scsi_device *s > { > struct request *req; > struct scsi_request *rq; > + blk_mq_req_flags_t mq_req_flags; > int ret = DRIVER_ERROR << 24; > > + mq_req_flags = BLK_MQ_REQ_PREEMPT; > + if (rq_flags & RQF_PM) > + mq_req_flags |= BLK_MQ_REQ_PM; > req = blk_get_request(sdev->request_queue, > data_direction == DMA_TO_DEVICE ? > - REQ_OP_SCSI_OUT : REQ_OP_SCSI_IN, BLK_MQ_REQ_PREEMPT); > + REQ_OP_SCSI_OUT : REQ_OP_SCSI_IN, mq_req_flags); > if (IS_ERR(req)) > return ret; > rq = scsi_req(req); > Index: usb-devel/include/linux/blk-mq.h > =================================================================== > --- usb-devel.orig/include/linux/blk-mq.h > +++ usb-devel/include/linux/blk-mq.h > @@ -435,6 +435,8 @@ enum { > BLK_MQ_REQ_RESERVED = (__force blk_mq_req_flags_t)(1 << 1), > /* set RQF_PREEMPT */ > BLK_MQ_REQ_PREEMPT = (__force blk_mq_req_flags_t)(1 << 3), > + /* used for power management */ > + BLK_MQ_REQ_PM = (__force blk_mq_req_flags_t)(1 << 4), > }; > > struct request *blk_mq_alloc_request(struct request_queue *q, unsigned int op, I think this patch will break SCSI domain validation. The SCSI domain validation code calls scsi_device_quiesce() and that function in turn calls blk_set_pm_only(). The SCSI domain validation code submits SCSI commands with the BLK_MQ_REQ_PREEMPT flag. Since the above code postpones such requests while blk_set_pm_only() is in effect, I think the above patch will cause the SCSI domain validation code to deadlock. Bart.