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=-17.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 ACF68C4338F for ; Mon, 23 Aug 2021 13:17:56 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 918D561357 for ; Mon, 23 Aug 2021 13:17:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237304AbhHWNSg (ORCPT ); Mon, 23 Aug 2021 09:18:36 -0400 Received: from szxga08-in.huawei.com ([45.249.212.255]:15205 "EHLO szxga08-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235966AbhHWNSc (ORCPT ); Mon, 23 Aug 2021 09:18:32 -0400 Received: from dggemv711-chm.china.huawei.com (unknown [172.30.72.55]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4GtXpP3PTkz1CZrc; Mon, 23 Aug 2021 21:17:17 +0800 (CST) Received: from dggema773-chm.china.huawei.com (10.1.198.217) by dggemv711-chm.china.huawei.com (10.1.198.66) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256) id 15.1.2176.2; Mon, 23 Aug 2021 21:17:48 +0800 Received: from [10.174.179.2] (10.174.179.2) by dggema773-chm.china.huawei.com (10.1.198.217) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2176.2; Mon, 23 Aug 2021 21:17:47 +0800 From: Li Jinlin Subject: Re: [PATCH v2] scsi: core: Fix hang of freezing queue between blocking and running device To: , , , CC: , , , , References: <20210809141308.3700854-1-lijinlin3@huawei.com> <8d0583de-f818-1be7-ac08-c84cfd5988f6@huawei.com> Message-ID: <30fef732-a719-8c41-b8bf-951d6cfdf243@huawei.com> Date: Mon, 23 Aug 2021 21:17:47 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <8d0583de-f818-1be7-ac08-c84cfd5988f6@huawei.com> Content-Type: text/plain; charset="gbk" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.179.2] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To dggema773-chm.china.huawei.com (10.1.198.217) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021/8/17 16:46, Li Jinlin wrote: > On 2021/8/9 22:13, Li Jinlin wrote: >> From: Li Jinlin >> >> We found a hang issue, the test steps are as follows: >> 1. blocking device via scsi_device_set_state() >> 2. dd if=/dev/sda of=/mnt/t.log bs=1M count=10 >> 3. echo none > /sys/block/sda/queue/scheduler >> 4. echo "running" >/sys/block/sda/device/state >> >> Step 3 and 4 should finish this work after step 4, but they hangs. >> >> CPU#0 CPU#1 CPU#2 >> --------------- ---------------- ---------------- >> Step 1: blocking device >> >> Step 2: dd xxxx >> ^^^^^^ get request >> q_usage_counter++ >> >> Step 3: switching scheculer >> elv_iosched_store >> elevator_switch >> blk_mq_freeze_queue >> blk_freeze_queue >> > blk_freeze_queue_start >> ^^^^^^ mq_freeze_depth++ >> >> > blk_mq_run_hw_queues >> ^^^^^^ can't run queue when dev blocked >> >> > blk_mq_freeze_queue_wait >> ^^^^^^ Hang here!!! >> wait q_usage_counter==0 >> >> Step 4: running device >> store_state_field >> scsi_rescan_device >> scsi_attach_vpd >> scsi_vpd_inquiry >> __scsi_execute >> blk_get_request >> blk_mq_alloc_request >> blk_queue_enter >> ^^^^^^ Hang here!!! >> wait mq_freeze_depth==0 >> >> blk_mq_run_hw_queues >> ^^^^^^ dispatch IO, q_usage_counter will reduce to zero >> >> blk_mq_unfreeze_queue >> ^^^^^ mq_freeze_depth-- >> >> Step 3 and 4 wait for each other. >> >> To fix this, we need to run queue before rescanning device when the device >> state changes to SDEV_RUNNING. >> >> Fixes: f0f82e2476f6 ("scsi: core: Fix capacity set to zero after offlinining device") >> Signed-off-by: Li Jinlin >> Signed-off-by: Qiu Laibin >> --- >> changes since v1 send with Message-ID: >> 20210805143231.1713299-1-lijinlin3@huawei.com >> >> - Modify the subject to make it distinct >> - Modify the message to fix typo and make it distinct >> - Reduce the number of SOB >> >> drivers/scsi/scsi_sysfs.c | 6 +++--- >> 1 file changed, 3 insertions(+), 3 deletions(-) >> >> diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c >> index c3a710bceba0..aa701582c950 100644 >> --- a/drivers/scsi/scsi_sysfs.c >> +++ b/drivers/scsi/scsi_sysfs.c >> @@ -809,12 +809,12 @@ store_state_field(struct device *dev, struct device_attribute *attr, >> ret = scsi_device_set_state(sdev, state); >> /* >> * If the device state changes to SDEV_RUNNING, we need to >> - * rescan the device to revalidate it, and run the queue to >> - * avoid I/O hang. >> + * run the queue to avoid I/O hang, and rescan the device >> + * to revalidate it. >> */ >> if (ret == 0 && state == SDEV_RUNNING) { >> - scsi_rescan_device(dev); >> blk_mq_run_hw_queues(sdev->request_queue, true); >> + scsi_rescan_device(dev); >> } >> mutex_unlock(&sdev->state_mutex); >> >> > > Ping. > > Thanks, > Li Jinlin > Hello Guys, Ping again. Otherwise, I think that rescan device is not necessary when the device state changes from blocked to running. Run queue is not necessary either when the device state changes from offline to running. I want to add judgment of the old device state before rescanning device or running queue. I'd like to know your opinions. Thanks, Li Jinlin