Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Subject: Re: [PATCH v1 2/3] scsi: ufs: Optimize host lock on transfer requests
 send/compl paths
To:     Can Guo <cang@codeaurora.org>, asutoshd@codeaurora.org,
        nguyenb@codeaurora.org, hongwus@codeaurora.org,
        linux-scsi@vger.kernel.org, kernel-team@android.com
Cc:     Stanley Chu <stanley.chu@mediatek.com>,
        Alim Akhtar <alim.akhtar@samsung.com>,
        Avri Altman <avri.altman@wdc.com>,
        "James E.J. Bottomley" <jejb@linux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@oracle.com>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        Bean Huo <beanhuo@micron.com>,
        Jaegeuk Kim <jaegeuk@kernel.org>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Kiwoong Kim <kwmad.kim@samsung.com>,
        Satya Tangirala <satyat@google.com>,
        open list <linux-kernel@vger.kernel.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-arm-kernel@lists.infradead.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@lists.infradead.org>
References: <1621845419-14194-1-git-send-email-cang@codeaurora.org>
 <1621845419-14194-3-git-send-email-cang@codeaurora.org>
From:   Bart Van Assche <bvanassche@acm.org>
Message-ID: <c31185f5-e816-937d-25ac-1657b6111ff8@acm.org>
Date:   Mon, 28 Jun 2021 15:58:15 -0700
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101
 Thunderbird/78.11.0
MIME-Version: 1.0
In-Reply-To: <1621845419-14194-3-git-send-email-cang@codeaurora.org>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 5/24/21 1:36 AM, Can Guo wrote:
> Current UFS IRQ handler is completely wrapped by host lock, and because
> ufshcd_send_command() is also protected by host lock, when IRQ handler
> fires, not only the CPU running the IRQ handler cannot send new requests,
> the rest CPUs can neither. Move the host lock wrapping the IRQ handler into
> specific branches, i.e., ufshcd_uic_cmd_compl(), ufshcd_check_errors(),
> ufshcd_tmc_handler() and ufshcd_transfer_req_compl(). Meanwhile, to further
> reduce occpuation of host lock in ufshcd_transfer_req_compl(), host lock is
> no longer required to call __ufshcd_transfer_req_compl(). As per test, the
> optimization can bring considerable gain to random read/write performance.

Hi Can,

Since this patch has been applied on the AOSP kernel we see 100%
reproducible lockups appearing on multiple test setups. Examples of call
traces:

blk_execute_rq()
__scsi_execute()
sd_sync_cache()
sd_suspend_common()
sd_suspend_system()
scsi_bus_suspend()
__device_suspend()

blk_execute_rq()
__scsi_execute()
ufshcd_clear_ua_wlun()
ufshcd_err_handling_unprepare()
ufshcd_err_handler()
process_one_work()

Reverting this patch and the next patch from this series solved the
lockups. Do you prefer to revert this patch or do you perhaps want us to
test a potential fix?

Thanks,

Bart.