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Fri, 31 Jul 2020 23:17:10 GMT Received: by smtp.codeaurora.org (Postfix, from userid 1001) id 17040C43395; Fri, 31 Jul 2020 23:17:09 +0000 (UTC) Received: from mail.codeaurora.org (localhost.localdomain [127.0.0.1]) (using TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) (Authenticated sender: cang) by smtp.codeaurora.org (Postfix) with ESMTPSA id BF5A5C433CA; Fri, 31 Jul 2020 23:17:08 +0000 (UTC) MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="=_5c3e63ea4c7ecc7e8e595b7c9d9d7f3e" Date: Sat, 01 Aug 2020 07:17:08 +0800 From: Can Guo To: Bart Van Assche Subject: Re: [PATCH v4] scsi: ufs: Cleanup completed request without interrupt notification In-Reply-To: References: <20200724140246.19434-1-stanley.chu@mediatek.com> <1596159018.17247.53.camel@mtkswgap22> <97f1dfb0-41b6-0249-3e82-cae480b0efb6@acm.org> <8b0a158a7c3ee2165e09290996521ffc@codeaurora.org> Message-ID: <548b602daa1e15415625cb8d1f81a208@codeaurora.org> X-Sender: cang@codeaurora.org User-Agent: Roundcube Webmail/1.3.9 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200731_191740_921532_C1893E47 X-CRM114-Status: GOOD ( 22.42 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-scsi@vger.kernel.org, martin.petersen@oracle.com, andy.teng@mediatek.com, jejb@linux.ibm.com, chun-hung.wu@mediatek.com, kuohong.wang@mediatek.com, linux-kernel@vger.kernel.org, asutoshd@codeaurora.org, Avri Altman , linux-mediatek@lists.infradead.org, peter.wang@mediatek.com, alim.akhtar@samsung.com, matthias.bgg@gmail.com, Stanley Chu , chaotian.jing@mediatek.com, cc.chou@mediatek.com, linux-arm-kernel@lists.infradead.org, beanhuo@micron.com Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org --=_5c3e63ea4c7ecc7e8e595b7c9d9d7f3e Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8; format=flowed Hi Bart, On 2020-08-01 00:51, Bart Van Assche wrote: > On 2020-07-31 01:00, Can Guo wrote: >> AFAIK, sychronization of scsi_done is not a problem here, because scsi >> layer >> use the atomic state, namely SCMD_STATE_COMPLETE, of a scsi cmd to >> prevent >> the concurrency of abort and real completion of it. >> >> Check func scsi_times_out(), hope it helps. >> >> enum blk_eh_timer_return scsi_times_out(struct request *req) >> { >> ... >>         if (rtn == BLK_EH_DONE) { >>                 /* >>                  * Set the command to complete first in order to >> prevent >> a real >>                  * completion from releasing the command while error >> handling >>                  * is using it. If the command was already completed, >> then the >>                  * lower level driver beat the timeout handler, and it >> is safe >>                  * to return without escalating error recovery. >>                  * >>                  * If timeout handling lost the race to a real >> completion, the >>                  * block layer may ignore that due to a fake timeout >> injection, >>                  * so return RESET_TIMER to allow error handling >> another >> shot >>                  * at this command. >>                  */ >>                 if (test_and_set_bit(SCMD_STATE_COMPLETE, >> &scmd->state)) >>                         return BLK_EH_RESET_TIMER; >>                 if (scsi_abort_command(scmd) != SUCCESS) { >>                         set_host_byte(scmd, DID_TIME_OUT); >>                         scsi_eh_scmd_add(scmd); >>                 } >>         } >> } > > I am familiar with this mechanism. My concern is that both the regular > completion path and the abort handler must call scsi_dma_unmap() before > calling cmd->scsi_done(cmd). I don't see how > test_and_set_bit(SCMD_STATE_COMPLETE, &scmd->state) could prevent that > the regular completion path and the abort handler call scsi_dma_unmap() > concurrently since both calls happen before the SCMD_STATE_COMPLETE bit > is set? > > Thanks, > > Bart. For scsi_dma_unmap() part, that is true - we should make it serialized with any other completion paths. I've found it during my fault injection test, so I've made a patch to fix it, but it only comes in my next error recovery enhancement patch series. Please check the attachment. 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