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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 393F3C47082 for ; Tue, 5 Apr 2022 08:01:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235929AbiDEIAq (ORCPT ); Tue, 5 Apr 2022 04:00:46 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57156 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232289AbiDEHtj (ORCPT ); Tue, 5 Apr 2022 03:49:39 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 825449231A; Tue, 5 Apr 2022 00:46:56 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 50AE6616BF; Tue, 5 Apr 2022 07:46:54 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 559E2C340EE; Tue, 5 Apr 2022 07:46:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1649144813; bh=shC9lZfikSAMpKtryhJ0fccj+2yQUfMv3orgsp88R6A=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=kBhlihyXXSaEi6lTXXU86/+7Cua8RsLGnzO2FVSc3eNg2sp+0SYxi/h84indv7ybF GkgNFJoaI1czf22jui2+xXquv/NgBJ0VpebJE8cLkbu4XsQOxlH9HG1PdYpHkQrNhW VLIrJ7vXrC9Dh1o2HmLW2QCxj53qQxLQd3Nlek6c= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Shinichiro Kawasaki , Jens Axboe Subject: [PATCH 5.17 0142/1126] block: limit request dispatch loop duration Date: Tue, 5 Apr 2022 09:14:49 +0200 Message-Id: <20220405070411.748592937@linuxfoundation.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220405070407.513532867@linuxfoundation.org> References: <20220405070407.513532867@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Shin'ichiro Kawasaki commit 572299f03afd676dd4e20669cdaf5ed0fe1379d4 upstream. When IO requests are made continuously and the target block device handles requests faster than request arrival, the request dispatch loop keeps on repeating to dispatch the arriving requests very long time, more than a minute. Since the loop runs as a workqueue worker task, the very long loop duration triggers workqueue watchdog timeout and BUG [1]. To avoid the very long loop duration, break the loop periodically. When opportunity to dispatch requests still exists, check need_resched(). If need_resched() returns true, the dispatch loop already consumed its time slice, then reschedule the dispatch work and break the loop. With heavy IO load, need_resched() does not return true for 20~30 seconds. To cover such case, check time spent in the dispatch loop with jiffies. If more than 1 second is spent, reschedule the dispatch work and break the loop. [1] [ 609.691437] BUG: workqueue lockup - pool cpus=10 node=1 flags=0x0 nice=-20 stuck for 35s! [ 609.701820] Showing busy workqueues and worker pools: [ 609.707915] workqueue events: flags=0x0 [ 609.712615] pwq 0: cpus=0 node=0 flags=0x0 nice=0 active=1/256 refcnt=2 [ 609.712626] pending: drm_fb_helper_damage_work [drm_kms_helper] [ 609.712687] workqueue events_freezable: flags=0x4 [ 609.732943] pwq 0: cpus=0 node=0 flags=0x0 nice=0 active=1/256 refcnt=2 [ 609.732952] pending: pci_pme_list_scan [ 609.732968] workqueue events_power_efficient: flags=0x80 [ 609.751947] pwq 0: cpus=0 node=0 flags=0x0 nice=0 active=1/256 refcnt=2 [ 609.751955] pending: neigh_managed_work [ 609.752018] workqueue kblockd: flags=0x18 [ 609.769480] pwq 21: cpus=10 node=1 flags=0x0 nice=-20 active=3/256 refcnt=4 [ 609.769488] in-flight: 1020:blk_mq_run_work_fn [ 609.769498] pending: blk_mq_timeout_work, blk_mq_run_work_fn [ 609.769744] pool 21: cpus=10 node=1 flags=0x0 nice=-20 hung=35s workers=2 idle: 67 [ 639.899730] BUG: workqueue lockup - pool cpus=10 node=1 flags=0x0 nice=-20 stuck for 66s! [ 639.909513] Showing busy workqueues and worker pools: [ 639.915404] workqueue events: flags=0x0 [ 639.920197] pwq 0: cpus=0 node=0 flags=0x0 nice=0 active=1/256 refcnt=2 [ 639.920215] pending: drm_fb_helper_damage_work [drm_kms_helper] [ 639.920365] workqueue kblockd: flags=0x18 [ 639.939932] pwq 21: cpus=10 node=1 flags=0x0 nice=-20 active=3/256 refcnt=4 [ 639.939942] in-flight: 1020:blk_mq_run_work_fn [ 639.939955] pending: blk_mq_timeout_work, blk_mq_run_work_fn [ 639.940212] pool 21: cpus=10 node=1 flags=0x0 nice=-20 hung=66s workers=2 idle: 67 Fixes: 6e6fcbc27e778 ("blk-mq: support batching dispatch in case of io") Signed-off-by: Shin'ichiro Kawasaki Cc: stable@vger.kernel.org # v5.10+ Link: https://lore.kernel.org/linux-block/20220310091649.zypaem5lkyfadymg@shindev/ Link: https://lore.kernel.org/r/20220318022641.133484-1-shinichiro.kawasaki@wdc.com Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman --- block/blk-mq-sched.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) --- a/block/blk-mq-sched.c +++ b/block/blk-mq-sched.c @@ -180,11 +180,18 @@ static int __blk_mq_do_dispatch_sched(st static int blk_mq_do_dispatch_sched(struct blk_mq_hw_ctx *hctx) { + unsigned long end = jiffies + HZ; int ret; do { ret = __blk_mq_do_dispatch_sched(hctx); - } while (ret == 1); + if (ret != 1) + break; + if (need_resched() || time_is_before_jiffies(end)) { + blk_mq_delay_run_hw_queue(hctx, 0); + break; + } + } while (1); return ret; }