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=-9.8 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 06006C433EB for ; Mon, 27 Jul 2020 07:30:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CE0DE20786 for ; Mon, 27 Jul 2020 07:30:33 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=mg.codeaurora.org header.i=@mg.codeaurora.org header.b="QEiNUm5P" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727067AbgG0Had (ORCPT ); Mon, 27 Jul 2020 03:30:33 -0400 Received: from mail29.static.mailgun.info ([104.130.122.29]:34553 "EHLO mail29.static.mailgun.info" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726211AbgG0Hab (ORCPT ); Mon, 27 Jul 2020 03:30:31 -0400 DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1595835030; h=Message-ID: References: In-Reply-To: Subject: Cc: To: From: Date: Content-Transfer-Encoding: Content-Type: MIME-Version: Sender; bh=CVDJovx8o6kxZAd7Siw03nCa0NOSEKdy2eVnCp0MImQ=; b=QEiNUm5P4a9wabsb5jQNKv9wiF0iv1MDUwtBKBPxNxmsVYcLGDo2TQoi3CvfZLlNoOsWiiiA HSV2ysCpmPMKldVhMeigkiNNhlBY/3Tcrh/6C41YrywEAJC/5u7KK96v4lQssQXvFtDHXx4L KCVDuDJ2M/KWi7fA9ECpxWt+1aI= X-Mailgun-Sending-Ip: 104.130.122.29 X-Mailgun-Sid: WyJlNmU5NiIsICJsaW51eC1zY3NpQHZnZXIua2VybmVsLm9yZyIsICJiZTllNGEiXQ== Received: from smtp.codeaurora.org (ec2-35-166-182-171.us-west-2.compute.amazonaws.com [35.166.182.171]) by smtp-out-n14.prod.us-west-2.postgun.com with SMTP id 5f1e8284298a38b61655f805 (version=TLS1.2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256); Mon, 27 Jul 2020 07:30:12 GMT Received: by smtp.codeaurora.org (Postfix, from userid 1001) id 08794C43391; Mon, 27 Jul 2020 07:30:11 +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 CB45FC433C9; Mon, 27 Jul 2020 07:30:10 +0000 (UTC) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Content-Transfer-Encoding: 7bit Date: Mon, 27 Jul 2020 15:30:10 +0800 From: Can Guo To: Stanley Chu Cc: linux-scsi@vger.kernel.org, martin.petersen@oracle.com, avri.altman@wdc.com, alim.akhtar@samsung.com, jejb@linux.ibm.com, bvanassche@acm.org, beanhuo@micron.com, asutoshd@codeaurora.org, matthias.bgg@gmail.com, linux-mediatek@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kuohong.wang@mediatek.com, peter.wang@mediatek.com, chun-hung.wu@mediatek.com, andy.teng@mediatek.com, chaotian.jing@mediatek.com, cc.chou@mediatek.com Subject: Re: [PATCH v4] scsi: ufs: Quiesce all scsi devices before shutdown In-Reply-To: <20200724140140.18186-1-stanley.chu@mediatek.com> References: <20200724140140.18186-1-stanley.chu@mediatek.com> Message-ID: <84510fc12ada0de8284e6a689b7a2358@codeaurora.org> X-Sender: cang@codeaurora.org User-Agent: Roundcube Webmail/1.3.9 Sender: linux-scsi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org Hi Stanley, On 2020-07-24 22:01, Stanley Chu wrote: > Currently I/O request could be still submitted to UFS device while > UFS is working on shutdown flow. This may lead to racing as below > scenarios and finally system may crash due to unclocked register > accesses. > > To fix this kind of issues, specifically quiesce all SCSI devices > before UFS shutdown to block all I/O request sending from block > layer. > > Example of racing scenario: While UFS device is runtime-suspended > > Thread #1: Executing UFS shutdown flow, e.g., > ufshcd_suspend(UFS_SHUTDOWN_PM) > Thread #2: Executing runtime resume flow triggered by I/O request, > e.g., ufshcd_resume(UFS_RUNTIME_PM) > I don't quite get it, how can you prevent block layer PM from iniating hba runtime resume by quiescing the scsi devices? Block layer PM iniates hba async runtime resume in blk_queue_enter(). But quiescing the scsi devices can only prevent general I/O requests from passing through scsi_queue_rq() callback. Say hba is runtime suspended, if an I/O request to sda is sent from block layer (sda must be runtime suspended as well at this time), blk_queue_enter() initiates async runtime resume for sda. But since sda's parents are also runtime suspended, the RPM framework shall do runtime resume to the devices in the sequence hba->host->target->sda. In this case, ufshcd_resume() still runs concurrently, no? Thanks, Can Guo. > This breaks the assumption that UFS PM flows can not be running > concurrently and some unexpected racing behavior may happen. > > Signed-off-by: Stanley Chu > --- > drivers/scsi/ufs/ufshcd.c | 29 +++++++++++++++++++++++++++++ > 1 file changed, 29 insertions(+) > > diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c > index 9d180da77488..2e18596f3a8e 100644 > --- a/drivers/scsi/ufs/ufshcd.c > +++ b/drivers/scsi/ufs/ufshcd.c > @@ -159,6 +159,12 @@ struct ufs_pm_lvl_states ufs_pm_lvl_states[] = { > {UFS_POWERDOWN_PWR_MODE, UIC_LINK_OFF_STATE}, > }; > > +#define ufshcd_scsi_for_each_sdev(fn) \ > + list_for_each_entry(starget, &hba->host->__targets, siblings) { \ > + __starget_for_each_device(starget, NULL, \ > + fn); \ > + } > + > static inline enum ufs_dev_pwr_mode > ufs_get_pm_lvl_to_dev_pwr_mode(enum ufs_pm_level lvl) > { > @@ -8620,6 +8626,13 @@ int ufshcd_runtime_idle(struct ufs_hba *hba) > } > EXPORT_SYMBOL(ufshcd_runtime_idle); > > +static void ufshcd_quiesce_sdev(struct scsi_device *sdev, void *data) > +{ > + /* Suspended devices are already quiesced so can be skipped */ > + if (!pm_runtime_suspended(&sdev->sdev_gendev)) > + scsi_device_quiesce(sdev); > +} > + > /** > * ufshcd_shutdown - shutdown routine > * @hba: per adapter instance > @@ -8631,6 +8644,7 @@ EXPORT_SYMBOL(ufshcd_runtime_idle); > int ufshcd_shutdown(struct ufs_hba *hba) > { > int ret = 0; > + struct scsi_target *starget; > > if (!hba->is_powered) > goto out; > @@ -8644,6 +8658,21 @@ int ufshcd_shutdown(struct ufs_hba *hba) > goto out; > } > > + /* > + * Quiesce all SCSI devices to prevent any non-PM requests sending > + * from block layer during and after shutdown. > + * > + * Here we can not use blk_cleanup_queue() since PM requests > + * (with BLK_MQ_REQ_PREEMPT flag) are still required to be sent > + * through block layer. Therefore SCSI command queued after the > + * scsi_target_quiesce() call returned will block until > + * blk_cleanup_queue() is called. > + * > + * Besides, scsi_target_"un"quiesce (e.g., scsi_target_resume) can > + * be ignored since shutdown is one-way flow. > + */ > + ufshcd_scsi_for_each_sdev(ufshcd_quiesce_sdev); > + > ret = ufshcd_suspend(hba, UFS_SHUTDOWN_PM); > out: > if (ret)