From patchwork Tue May 10 11:23:02 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Yu Kuai X-Patchwork-Id: 12844866 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id DE2DBC433F5 for ; Tue, 10 May 2022 11:09:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233018AbiEJLNI (ORCPT ); Tue, 10 May 2022 07:13:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34838 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232692AbiEJLNH (ORCPT ); Tue, 10 May 2022 07:13:07 -0400 Received: from szxga01-in.huawei.com (szxga01-in.huawei.com [45.249.212.187]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CF123106366; Tue, 10 May 2022 04:09:09 -0700 (PDT) Received: from kwepemi500020.china.huawei.com (unknown [172.30.72.55]) by szxga01-in.huawei.com (SkyGuard) with ESMTP id 4KyFd84Fk7zfbXF; Tue, 10 May 2022 19:07:56 +0800 (CST) Received: from kwepemm600009.china.huawei.com (7.193.23.164) by kwepemi500020.china.huawei.com (7.221.188.8) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Tue, 10 May 2022 19:09:07 +0800 Received: from huawei.com (10.175.127.227) by kwepemm600009.china.huawei.com (7.193.23.164) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Tue, 10 May 2022 19:09:07 +0800 From: Yu Kuai To: CC: , , , Subject: [PATCH] blk-mq: don't queue 'hctx->run_work' if the queue is dead Date: Tue, 10 May 2022 19:23:02 +0800 Message-ID: <20220510112302.1215092-1-yukuai3@huawei.com> X-Mailer: git-send-email 2.31.1 MIME-Version: 1.0 X-Originating-IP: [10.175.127.227] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To kwepemm600009.china.huawei.com (7.193.23.164) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Our test report a following crash: BUG: kernel NULL pointer dereference, address: 0000000000000018 PGD 0 P4D 0 Oops: 0000 [#1] SMP NOPTI CPU: 6 PID: 265 Comm: kworker/6:1H Kdump: loaded Tainted: G O 5.10.0-60.17.0.h43.eulerosv2r11.x86_64 #1 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.1-0-ga5cab58-20220320_160524-szxrtosci10000 04/01/2014 Workqueue: kblockd blk_mq_run_work_fn RIP: 0010:blk_mq_delay_run_hw_queues+0xb6/0xe0 RSP: 0018:ffffacc6803d3d88 EFLAGS: 00010246 RAX: 0000000000000006 RBX: ffff99e2c3d25008 RCX: 00000000ffffffff RDX: 0000000000000000 RSI: 0000000000000003 RDI: ffff99e2c911ae18 RBP: ffffacc6803d3dd8 R08: 0000000000000000 R09: ffff99e2c0901f6c R10: 0000000000000018 R11: 0000000000000018 R12: ffff99e2c911ae18 R13: 0000000000000000 R14: 0000000000000003 R15: ffff99e2c911ae18 FS: 0000000000000000(0000) GS:ffff99e6bbf00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000018 CR3: 000000007460a006 CR4: 00000000003706e0 Call Trace: __blk_mq_do_dispatch_sched+0x2a7/0x2c0 ? newidle_balance+0x23e/0x2f0 __blk_mq_sched_dispatch_requests+0x13f/0x190 blk_mq_sched_dispatch_requests+0x30/0x60 __blk_mq_run_hw_queue+0x47/0xd0 process_one_work+0x1b0/0x350 worker_thread+0x49/0x300 ? rescuer_thread+0x3a0/0x3a0 kthread+0xfe/0x140 ? kthread_park+0x90/0x90 ret_from_fork+0x22/0x30 After digging from vmcore, I found that the queue is cleaned up(blk_cleanup_queue() is done) and tag set is freed(blk_mq_free_tag_set() is done). There are two problems here: 1) blk_mq_delay_run_hw_queues() will only be called from __blk_mq_do_dispatch_sched() if e->type->ops.has_work() return true. This seems impossible because blk_cleanup_queue() is done, and there should be no io. However, bfq_has_work() can return true even if no io is queued. This is because bfq_has_work() is using busy queues, and bfq_queue can stay busy after dispatching all the requests. 2) 'hctx->run_work' still exists after blk_cleanup_queue(). blk_mq_cancel_work_sync() is called from blk_cleanup_queue() to cancel all the 'run_work'. However, there is no guarantee that new 'run_work' won't be queued after that(and before blk_mq_exit_queue() is done). The first problem is not the root cause, this patch just fix the second problem by checking the 'QUEUE_FLAG_DEAD' before queuing 'hctx->run_work', and using 'queue_lock' to synchronize queuing new work and cacelling the old work. Signed-off-by: Yu Kuai --- block/blk-core.c | 3 +++ block/blk-mq.c | 10 ++++++++-- 2 files changed, 11 insertions(+), 2 deletions(-) diff --git a/block/blk-core.c b/block/blk-core.c index c3f1e46ddd43..2609805861be 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -318,7 +318,10 @@ void blk_cleanup_queue(struct request_queue *q) /* cleanup rq qos structures for queue without disk */ rq_qos_exit(q); + /* New 'hctx->run_work' can't be queued after setting the dead flag */ + spin_lock_irq(&q->queue_lock); blk_queue_flag_set(QUEUE_FLAG_DEAD, q); + spin_unlock_irq(&q->queue_lock); blk_sync_queue(q); if (queue_is_mq(q)) { diff --git a/block/blk-mq.c b/block/blk-mq.c index 2cf011b57cf9..34b4914204dd 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -2042,6 +2042,8 @@ static int blk_mq_hctx_next_cpu(struct blk_mq_hw_ctx *hctx) static void __blk_mq_delay_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async, unsigned long msecs) { + unsigned long flag; + if (unlikely(blk_mq_hctx_stopped(hctx))) return; @@ -2056,8 +2058,12 @@ static void __blk_mq_delay_run_hw_queue(struct blk_mq_hw_ctx *hctx, bool async, put_cpu(); } - kblockd_mod_delayed_work_on(blk_mq_hctx_next_cpu(hctx), &hctx->run_work, - msecs_to_jiffies(msecs)); + spin_lock_irqsave(&hctx->queue->queue_lock, flag); + if (!blk_queue_dead(hctx->queue)) + kblockd_mod_delayed_work_on(blk_mq_hctx_next_cpu(hctx), + &hctx->run_work, + msecs_to_jiffies(msecs)); + spin_unlock_irqrestore(&hctx->queue->queue_lock, flag); } /**