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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 33F86C35240 for ; Sun, 26 Jan 2020 03:30:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EE27C2071E for ; Sun, 26 Jan 2020 03:30:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729122AbgAZDaA (ORCPT ); Sat, 25 Jan 2020 22:30:00 -0500 Received: from mail-pf1-f194.google.com ([209.85.210.194]:39841 "EHLO mail-pf1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728842AbgAZD37 (ORCPT ); Sat, 25 Jan 2020 22:29:59 -0500 Received: by mail-pf1-f194.google.com with SMTP id q10so3195411pfs.6; Sat, 25 Jan 2020 19:29:58 -0800 (PST) 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=N+COkGkdfHeb1HY7LPYrfTxzXMweLGHf0JX8QC6GcnE=; b=l/4WbgkerBcuHFxWDnUNtCGnrGS9nKPTQVgnppUhw2/jg5zWfZy1uCma+Y4Wjf1oq9 S3oU8fs5He6w7Isp3CTDq78laLeqh0m5n64YCzeYTa9K7At0UINa0cK4P0hzWy7QoNbM 421RRImHSCZYUSp+bZ0K1FwMifQkx8KzlDw3INjoduaI6CT126WvJ7EN9YBCe1WFErOo 1duK6bmS4oVELCMsRuCKXs0X1M/qzR0lYyUykRjNwg1xic9T/I16oqU7V7c6v0Q+UT2G EbMGnkLdSmKVTbDoVnBKj8U6HBZZfVUpgaaQZzUu+o8xQ5cFrE1buYf6dFrqn31SI5al qPBw== X-Gm-Message-State: APjAAAWhe2KwlGI9gnpEXCVzTvv679aX4ryGSNTvnPw6WdPn0H501FFo 2xfnaKmhsWFV9KWWo0BmtjNVVWFJoeM= X-Google-Smtp-Source: APXvYqwQ5vnYMPjXlEC23TI50IHXd8maikfNyaFxlIbAfHWWbi7aeaUZ/eMahXpiCU1ZobApoKYcgQ== X-Received: by 2002:a63:7c2:: with SMTP id 185mr12219013pgh.446.1580009398138; Sat, 25 Jan 2020 19:29:58 -0800 (PST) Received: from ?IPv6:2601:647:4000:d7:a876:9802:4659:f0bd? ([2601:647:4000:d7:a876:9802:4659:f0bd]) by smtp.gmail.com with ESMTPSA id z30sm11605612pfq.154.2020.01.25.19.29.56 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 25 Jan 2020 19:29:57 -0800 (PST) Subject: Re: [PATCH v4 1/8] scsi: ufs: Flush exception event before suspend To: Can Guo , asutoshd@codeaurora.org, nguyenb@codeaurora.org, hongwus@codeaurora.org, rnayak@codeaurora.org, linux-scsi@vger.kernel.org, kernel-team@android.com, saravanak@google.com, salyzyn@google.com Cc: Sayali Lokhande , Alim Akhtar , Avri Altman , Pedro Sousa , "James E.J. Bottomley" , "Martin K. Petersen" , Stanley Chu , Bean Huo , Venkat Gopalakrishnan , Tomas Winkler , open list References: <1579764349-15578-1-git-send-email-cang@codeaurora.org> <1579764349-15578-2-git-send-email-cang@codeaurora.org> 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: <525e4f67-f471-54a6-aaea-b3772a550af1@acm.org> Date: Sat, 25 Jan 2020 19:29:55 -0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: <1579764349-15578-2-git-send-email-cang@codeaurora.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020-01-22 23:25, Can Guo wrote: > diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c > index 1201578..c2de29f 100644 > --- a/drivers/scsi/ufs/ufshcd.c > +++ b/drivers/scsi/ufs/ufshcd.c > @@ -4760,8 +4760,15 @@ static void ufshcd_slave_destroy(struct scsi_device *sdev) > * UFS device needs urgent BKOPs. > */ > if (!hba->pm_op_in_progress && > - ufshcd_is_exception_event(lrbp->ucd_rsp_ptr)) > - schedule_work(&hba->eeh_work); > + ufshcd_is_exception_event(lrbp->ucd_rsp_ptr)) { > + /* > + * Prevent suspend once eeh_work is scheduled > + * to avoid deadlock between ufshcd_suspend > + * and exception event handler. > + */ > + if (schedule_work(&hba->eeh_work)) > + pm_runtime_get_noresume(hba->dev); > + } Please combine the two logical tests with "&&" instead of nesting two if-statements inside each other. > break; > case UPIU_TRANSACTION_REJECT_UPIU: > /* TODO: handle Reject UPIU Response */ > @@ -5215,7 +5222,14 @@ static void ufshcd_exception_event_handler(struct work_struct *work) > > out: > scsi_unblock_requests(hba->host); > - pm_runtime_put_sync(hba->dev); > + /* > + * pm_runtime_get_noresume is called while scheduling > + * eeh_work to avoid suspend racing with exception work. > + * Hence decrement usage counter using pm_runtime_put_noidle > + * to allow suspend on completion of exception event handler. > + */ > + pm_runtime_put_noidle(hba->dev); > + pm_runtime_put(hba->dev); > return; > } > > @@ -7901,6 +7915,7 @@ static int ufshcd_suspend(struct ufs_hba *hba, enum ufs_pm_op pm_op) > goto enable_gating; > } > > + flush_work(&hba->eeh_work); > ret = ufshcd_link_state_transition(hba, req_link_state, 1); > if (ret) > goto set_dev_active; I think this patch introduces a new race condition, namely the following: - ufshcd_slave_destroy() tests pm_op_in_progress and reads the value zero from that variable. - ufshcd_suspend() sets hba->pm_op_in_progress to one. - ufshcd_slave_destroy() calls schedule_work(). How about fixing this race condition by calling pm_runtime_get_noresume() before checking pm_op_in_progress and by reallowing resume if no work is scheduled? Thanks, Bart.