From patchwork Thu Feb 11 15:02:41 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: Greg KH X-Patchwork-Id: 381760 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=-19.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 A191CC433E0 for ; Thu, 11 Feb 2021 15:22:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 578E064E8A for ; Thu, 11 Feb 2021 15:22:15 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229746AbhBKPV5 (ORCPT ); Thu, 11 Feb 2021 10:21:57 -0500 Received: from mail.kernel.org ([198.145.29.99]:52628 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230185AbhBKPSV (ORCPT ); Thu, 11 Feb 2021 10:18:21 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 329DA64F12; Thu, 11 Feb 2021 15:05:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1613055953; bh=mBU5b8VRc4MSpIsnNB2jc88+ZShmw8rX+D3GQtW1cFE=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=G95xZDAYNuJxLeqW02FiNjtGuJtZO3x5PNTkSIk/ieIDaYFHh13kRW4VmhNtr9g5v ZoGlqYl1cQILklWVOB6fr3FUWYZSQ/v977RvzGAIyqaxOzmJiZf/7uKoT6Dv2AEvAF Pgtq2IIMp6KI3pmHYe03YFCUtMbGyRlGwFpZMeJY= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Tejun Heo , Baolin Wang , Jens Axboe , Sasha Levin Subject: [PATCH 5.4 18/24] blk-cgroup: Use cond_resched() when destroy blkgs Date: Thu, 11 Feb 2021 16:02:41 +0100 Message-Id: <20210211150149.315436519@linuxfoundation.org> X-Mailer: git-send-email 2.30.1 In-Reply-To: <20210211150148.516371325@linuxfoundation.org> References: <20210211150148.516371325@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Baolin Wang [ Upstream commit 6c635caef410aa757befbd8857c1eadde5cc22ed ] On !PREEMPT kernel, we can get below softlockup when doing stress testing with creating and destroying block cgroup repeatly. The reason is it may take a long time to acquire the queue's lock in the loop of blkcg_destroy_blkgs(), or the system can accumulate a huge number of blkgs in pathological cases. We can add a need_resched() check on each loop and release locks and do cond_resched() if true to avoid this issue, since the blkcg_destroy_blkgs() is not called from atomic contexts. [ 4757.010308] watchdog: BUG: soft lockup - CPU#11 stuck for 94s! [ 4757.010698] Call trace: [ 4757.010700]  blkcg_destroy_blkgs+0x68/0x150 [ 4757.010701]  cgwb_release_workfn+0x104/0x158 [ 4757.010702]  process_one_work+0x1bc/0x3f0 [ 4757.010704]  worker_thread+0x164/0x468 [ 4757.010705]  kthread+0x108/0x138 Suggested-by: Tejun Heo Signed-off-by: Baolin Wang Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- block/blk-cgroup.c | 18 +++++++++++++----- 1 file changed, 13 insertions(+), 5 deletions(-) diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c index 3d34ac02d76ef..cb3d44d200055 100644 --- a/block/blk-cgroup.c +++ b/block/blk-cgroup.c @@ -1089,6 +1089,8 @@ static void blkcg_css_offline(struct cgroup_subsys_state *css) */ void blkcg_destroy_blkgs(struct blkcg *blkcg) { + might_sleep(); + spin_lock_irq(&blkcg->lock); while (!hlist_empty(&blkcg->blkg_list)) { @@ -1096,14 +1098,20 @@ void blkcg_destroy_blkgs(struct blkcg *blkcg) struct blkcg_gq, blkcg_node); struct request_queue *q = blkg->q; - if (spin_trylock(&q->queue_lock)) { - blkg_destroy(blkg); - spin_unlock(&q->queue_lock); - } else { + if (need_resched() || !spin_trylock(&q->queue_lock)) { + /* + * Given that the system can accumulate a huge number + * of blkgs in pathological cases, check to see if we + * need to rescheduling to avoid softlockup. + */ spin_unlock_irq(&blkcg->lock); - cpu_relax(); + cond_resched(); spin_lock_irq(&blkcg->lock); + continue; } + + blkg_destroy(blkg); + spin_unlock(&q->queue_lock); } spin_unlock_irq(&blkcg->lock);