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 41ACEC4332F for ; Tue, 5 Apr 2022 11:47:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241775AbiDELrM (ORCPT ); Tue, 5 Apr 2022 07:47:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51960 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1355268AbiDEKSu (ORCPT ); Tue, 5 Apr 2022 06:18:50 -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 4363C10FE1; Tue, 5 Apr 2022 03:04:37 -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 CDB5F61673; Tue, 5 Apr 2022 10:04:36 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id DE4FEC385A2; Tue, 5 Apr 2022 10:04:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1649153076; bh=uos+dZQFyuLbUjPtiaSV8Nc9hZwgOh9eP9pCprv8FZs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=EMOpZ/6zfwaZ/KCCdwYhL17zUXNW2udDxGs2Zq+CTaC2r/tOsEG41czJSWiiSUD1s DF9oOqmmW0fc9iQV7MbH28XJKuRiX9luX7mx9gKZzk5UNtUjHBXq/fVik3eSUspq2W dF6xPXmOgGwIEneCrH8xpG++dT6t8oChCIGfONPI= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Shinichiro Kawasaki , Jens Axboe Subject: [PATCH 5.10 094/599] block: limit request dispatch loop duration Date: Tue, 5 Apr 2022 09:26:28 +0200 Message-Id: <20220405070301.627744791@linuxfoundation.org> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220405070258.802373272@linuxfoundation.org> References: <20220405070258.802373272@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: stable@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 @@ -194,11 +194,18 @@ 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; }