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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C45E3C4332F for ; Thu, 21 Oct 2021 12:39:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id ACB4C6120F for ; Thu, 21 Oct 2021 12:39:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231309AbhJUMlt (ORCPT ); Thu, 21 Oct 2021 08:41:49 -0400 Received: from szxga01-in.huawei.com ([45.249.212.187]:13966 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230365AbhJUMls (ORCPT ); Thu, 21 Oct 2021 08:41:48 -0400 Received: from dggeme754-chm.china.huawei.com (unknown [172.30.72.53]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4HZn7V1gFwzW259; Thu, 21 Oct 2021 20:37:42 +0800 (CST) Received: from huawei.com (10.175.127.227) by dggeme754-chm.china.huawei.com (10.3.19.100) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2308.15; Thu, 21 Oct 2021 20:39:29 +0800 From: Ye Bin To: , , , CC: , Ye Bin Subject: [PATCH -next v2 2/2] nbd: Fix hungtask when nbd_config_put Date: Thu, 21 Oct 2021 20:52:31 +0800 Message-ID: <20211021125231.916081-3-yebin10@huawei.com> X-Mailer: git-send-email 2.31.1 In-Reply-To: <20211021125231.916081-1-yebin10@huawei.com> References: <20211021125231.916081-1-yebin10@huawei.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7BIT Content-Type: text/plain; charset=US-ASCII X-Originating-IP: [10.175.127.227] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To dggeme754-chm.china.huawei.com (10.3.19.100) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org I got follow issue: [ 247.381177] INFO: task kworker/u10:0:47 blocked for more than 120 seconds. [ 247.382644] Not tainted 4.19.90-dirty #140 [ 247.383502] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. [ 247.385027] Call Trace: [ 247.388384] schedule+0xb8/0x3c0 [ 247.388966] schedule_timeout+0x2b4/0x380 [ 247.392815] wait_for_completion+0x367/0x510 [ 247.397713] flush_workqueue+0x32b/0x1340 [ 247.402700] drain_workqueue+0xda/0x3c0 [ 247.403442] destroy_workqueue+0x7b/0x690 [ 247.405014] nbd_config_put.cold+0x2f9/0x5b6 [ 247.405823] recv_work+0x1fd/0x2b0 [ 247.406485] process_one_work+0x70b/0x1610 [ 247.407262] worker_thread+0x5a9/0x1060 [ 247.408699] kthread+0x35e/0x430 [ 247.410918] ret_from_fork+0x1f/0x30 We can reprodeuce issue as follows: 1. Inject memory fault in nbd_start_device -1244,10 +1248,18 @@ static int nbd_start_device(struct nbd_device *nbd) nbd_dev_dbg_init(nbd); for (i = 0; i < num_connections; i++) { struct recv_thread_args *args; - - args = kzalloc(sizeof(*args), GFP_KERNEL); + + if (i == 1) { + args = NULL; + printk("%s: inject malloc error\n", __func__); + } + else + args = kzalloc(sizeof(*args), GFP_KERNEL); 2. Inject delay in recv_work -757,6 +760,8 @@ static void recv_work(struct work_struct *work) blk_mq_complete_request(blk_mq_rq_from_pdu(cmd)); } + printk("%s: comm=%s pid=%d\n", __func__, current->comm, current->pid); + mdelay(5 * 1000); nbd_config_put(nbd); atomic_dec(&config->recv_threads); wake_up(&config->recv_wq); 3. Create nbd server nbd-server 8000 /tmp/disk 4. Create nbd client nbd-client localhost 8000 /dev/nbd1 Then will trigger above issue. Reason is when add delay in recv_work, lead to relase the last reference of 'nbd->config_refs'. nbd_config_put will call flush_workqueue to make all work finish. Obviously, it will lead to deadloop. To solve this issue, according to Josef's suggestion move 'recv_work' init from start device to nbd_dev_add, then destory 'recv_work'when nbd device teardown. Signed-off-by: Ye Bin --- drivers/block/nbd.c | 30 ++++++++++++++---------------- 1 file changed, 14 insertions(+), 16 deletions(-) diff --git a/drivers/block/nbd.c b/drivers/block/nbd.c index 6b6ae08ec93b..905d9477e124 100644 --- a/drivers/block/nbd.c +++ b/drivers/block/nbd.c @@ -1319,10 +1319,6 @@ static void nbd_config_put(struct nbd_device *nbd) kfree(nbd->config); nbd->config = NULL; - if (nbd->recv_workq) - destroy_workqueue(nbd->recv_workq); - nbd->recv_workq = NULL; - nbd->tag_set.timeout = 0; nbd->disk->queue->limits.discard_granularity = 0; nbd->disk->queue->limits.discard_alignment = 0; @@ -1351,14 +1347,6 @@ static int nbd_start_device(struct nbd_device *nbd) return -EINVAL; } - nbd->recv_workq = alloc_workqueue("knbd%d-recv", - WQ_MEM_RECLAIM | WQ_HIGHPRI | - WQ_UNBOUND, 0, nbd->index); - if (!nbd->recv_workq) { - dev_err(disk_to_dev(nbd->disk), "Could not allocate knbd recv work queue.\n"); - return -ENOMEM; - } - blk_mq_update_nr_hw_queues(&nbd->tag_set, config->num_connections); nbd->task_recv = current; @@ -1790,6 +1778,15 @@ static struct nbd_device *nbd_dev_add(int index, unsigned int refs) } nbd->disk = disk; + nbd->recv_workq = alloc_workqueue("nbd%d-recv", + WQ_MEM_RECLAIM | WQ_HIGHPRI | + WQ_UNBOUND, 0, nbd->index); + if (!nbd->recv_workq) { + dev_err(disk_to_dev(nbd->disk), "Could not allocate knbd recv work queue.\n"); + err = -ENOMEM; + goto out_err_disk; + } + /* * Tell the block layer that we are not a rotational device */ @@ -1820,7 +1817,7 @@ static struct nbd_device *nbd_dev_add(int index, unsigned int refs) disk->first_minor = index << part_shift; if (disk->first_minor > 0xff) { err = -EINVAL; - goto out_err_disk; + goto out_free_work; } disk->minors = 1 << part_shift; @@ -1829,7 +1826,7 @@ static struct nbd_device *nbd_dev_add(int index, unsigned int refs) sprintf(disk->disk_name, "nbd%d", index); err = add_disk(disk); if (err) - goto out_err_disk; + goto out_free_work; /* * Now publish the device. @@ -1838,6 +1835,8 @@ static struct nbd_device *nbd_dev_add(int index, unsigned int refs) nbd_total_devices++; return nbd; +out_free_work: + destroy_workqueue(nbd->recv_workq); out_err_disk: blk_cleanup_disk(disk); out_free_idr: @@ -2098,8 +2097,7 @@ static void nbd_disconnect_and_put(struct nbd_device *nbd) * queue. And this also ensure that we can safely call nbd_clear_que() * to cancel the inflight I/Os. */ - if (nbd->recv_workq) - flush_workqueue(nbd->recv_workq); + flush_workqueue(nbd->recv_workq); nbd_clear_que(nbd); nbd->task_setup = NULL; mutex_unlock(&nbd->config_lock); -- 2.31.1