From patchwork Tue Aug 24 02:59:21 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Li Jinlin X-Patchwork-Id: 502071 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=-16.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, URIBL_BLOCKED, USER_AGENT_GIT autolearn=ham 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 D3E3BC4338F for ; Tue, 24 Aug 2021 02:30:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B0D9461409 for ; Tue, 24 Aug 2021 02:30:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233748AbhHXCar (ORCPT ); Mon, 23 Aug 2021 22:30:47 -0400 Received: from szxga08-in.huawei.com ([45.249.212.255]:15207 "EHLO szxga08-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230141AbhHXCap (ORCPT ); Mon, 23 Aug 2021 22:30:45 -0400 Received: from dggemv703-chm.china.huawei.com (unknown [172.30.72.57]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4GttNR3mMhz1CZpt; Tue, 24 Aug 2021 10:29:27 +0800 (CST) Received: from dggema773-chm.china.huawei.com (10.1.198.217) by dggemv703-chm.china.huawei.com (10.3.19.46) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256) id 15.1.2176.2; Tue, 24 Aug 2021 10:29:58 +0800 Received: from localhost.huawei.com (10.175.124.27) 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; Tue, 24 Aug 2021 10:29:58 +0800 From: Li Jinlin To: , , , CC: , , , , Subject: [PATCH v3] scsi: core: Fix hang of freezing queue between blocking and running device Date: Tue, 24 Aug 2021 10:59:21 +0800 Message-ID: <20210824025921.3277629-1-lijinlin3@huawei.com> X-Mailer: git-send-email 2.27.0 MIME-Version: 1.0 X-Originating-IP: [10.175.124.27] X-ClientProxiedBy: dggems703-chm.china.huawei.com (10.3.19.180) To dggema773-chm.china.huawei.com (10.1.198.217) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org 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 Reviewed-by: Bart Van Assche --- changes since v2 send with Message-ID: 20210809141308.3700854-1-lijinlin3@huawei.com - Expanded code comment in store_state_field() as suggested by Bart drivers/scsi/scsi_sysfs.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c index ae9bfc658203..c0d31119d6d7 100644 --- a/drivers/scsi/scsi_sysfs.c +++ b/drivers/scsi/scsi_sysfs.c @@ -808,12 +808,15 @@ 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. Running the queue first is necessary + * because another thread may be waiting inside + * blk_mq_freeze_queue_wait() and because that call may be + * waiting for pending I/O to finish. */ 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);