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=-2.3 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 74228C3524A for ; Tue, 4 Feb 2020 03:13:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 46D2C20732 for ; Tue, 4 Feb 2020 03:13:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727201AbgBDDM7 (ORCPT ); Mon, 3 Feb 2020 22:12:59 -0500 Received: from mail-pf1-f194.google.com ([209.85.210.194]:38850 "EHLO mail-pf1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726984AbgBDDM7 (ORCPT ); Mon, 3 Feb 2020 22:12:59 -0500 Received: by mail-pf1-f194.google.com with SMTP id x185so8688206pfc.5; Mon, 03 Feb 2020 19:12:58 -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=M+auj8u/G0hOUSjRgclLo4TJfIPU+Iqke+O3mqmT0Qg=; b=h/JrE5AKgR3ENXpzdpExp8wBQgLkJ4WYPh7xwn77Gc1AU39JugJcRaN8RpyASAEzsT BpvVqEIvkiYbKuC0exEpFBov46JYVwBlJs4TjxcUUj/9x7teRdyHCGNCg5ZHx9nlkpkY ScWmTCKvzg47Ky6V0sK2J7FZ0bbqczCqkidQ6Q4fjWCU28gTuab1rhyF6Ff8Eeu2sIft cvc/7pwTgFAu+f8zpoOfYCFEdX3Lu5lWgAwO1/6GpMSI+zOxJivVYQh5NbEwLIb5KouG WqWYRtLtFlZl6b5T4qb6Tb6NJeo7+sYSRlpYpoE1q5lv2wcxmZXJtt2eiaGqpF2cbogw sKEw== X-Gm-Message-State: APjAAAXB608Qhtk2mFPxjDtK0zKOyJ2sP89qXHK9GRzC1/Z877T8wfMF eukqaO6AhKG0aGnoBch8gDVNbGSl X-Google-Smtp-Source: APXvYqxOmjEmEQQTHoXRq/1SojYDnyCpu0Vw8WNDCoHImQKkLHAzJTjo6LFTEDdxELBpKTkQeHOtug== X-Received: by 2002:a63:646:: with SMTP id 67mr11747056pgg.376.1580785977499; Mon, 03 Feb 2020 19:12:57 -0800 (PST) Received: from ?IPv6:2601:647:4000:d7:39ff:b3e1:a9e7:4382? ([2601:647:4000:d7:39ff:b3e1:a9e7:4382]) by smtp.gmail.com with ESMTPSA id d69sm19765959pfd.72.2020.02.03.19.12.55 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 03 Feb 2020 19:12:56 -0800 (PST) Subject: Re: [PATCH v4 1/8] scsi: ufs: Flush exception event before suspend To: Can Guo Cc: 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, 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> <525e4f67-f471-54a6-aaea-b3772a550af1@acm.org> <82723efc44714e8677505cb7999d3fd5@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: <12716695-d9a3-a40c-e563-fa0365183b0e@acm.org> Date: Mon, 3 Feb 2020 19:12:55 -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: <82723efc44714e8677505cb7999d3fd5@codeaurora.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020-02-02 22:23, Can Guo wrote: > On 2020-01-26 11:29, Bart Van Assche wrote: >> On 2020-01-22 23:25, Can Guo wrote: >>>              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? > > If you apply this patch, you will find the change is not in > ufshcd_slave_destroy(), but in ufshcd_transfer_rsp_status(). > So the racing you mentioned above does not exist. Hi Can, Apparently I got a function name wrong. Can the following race condition happen: - ufshcd_transfer_rsp_status() tests pm_op_in_progress and reads the value zero from that variable. - ufshcd_suspend() sets hba->pm_op_in_progress to one. - ufshcd_suspend() calls flush_work(&hba->eeh_work). - ufshcd_transfer_rsp_status() calls schedule_work(&hba->eeh_work). Thanks, Bart.