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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 11EDCC53210 for ; Sun, 8 Jan 2023 12:08:06 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id F11308E0002; Sun, 8 Jan 2023 07:08:05 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id E9A2F8E0001; Sun, 8 Jan 2023 07:08:05 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D61958E0002; Sun, 8 Jan 2023 07:08:05 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id C21AC8E0001 for ; Sun, 8 Jan 2023 07:08:05 -0500 (EST) Received: from smtpin29.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 946441608BF for ; Sun, 8 Jan 2023 12:08:05 +0000 (UTC) X-FDA: 80331508530.29.EDAAA42 Received: from r3-23.sinamail.sina.com.cn (r3-23.sinamail.sina.com.cn [202.108.3.23]) by imf16.hostedemail.com (Postfix) with ESMTP id 2846518000C for ; Sun, 8 Jan 2023 12:08:01 +0000 (UTC) Authentication-Results: imf16.hostedemail.com; dkim=none; spf=pass (imf16.hostedemail.com: domain of hdanton@sina.com designates 202.108.3.23 as permitted sender) smtp.mailfrom=hdanton@sina.com; dmarc=none ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1673179684; a=rsa-sha256; cv=none; b=gT15CE33asdbWW8v2ZaVSfA7VZF0M8oS13bFtGsrPmYVC534yZS1ejLRJk1nMNm491NHz4 4u/Nxdvw69p+F4T3wRSZ0UrH78iedRy+NzZytGl2HRJC58G1QZuo9JOU8USWOVLrTWI1I/ 8gETh1JiZVuWNjRIuMs/ylyb9M0S96Q= ARC-Authentication-Results: i=1; imf16.hostedemail.com; dkim=none; spf=pass (imf16.hostedemail.com: domain of hdanton@sina.com designates 202.108.3.23 as permitted sender) smtp.mailfrom=hdanton@sina.com; dmarc=none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1673179684; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=h9ZXOWsVBm1NaX1Sakzbl3xzEBUglUalwtzJEGY7JCA=; b=kHDwZLLhf5lhsUCsZTt0xAclNOx2w7K0bmcSeCy5VxjvslIM42dOm9xRzbOOlwUw/tgAka pOqqdAz4rndREJT9VcrzS18BdxupcEyisXcDheD36Y52nff16DqkJ5y6dvG2a8nnQ9ZHAl fdBLVzqAMX55bqeqjVLil/1bD8ElocY= Received: from unknown (HELO localhost.localdomain)([114.249.57.238]) by sina.com (172.16.97.23) with ESMTP id 63BAB16900031D8D; Sun, 8 Jan 2023 20:04:58 +0800 (CST) X-Sender: hdanton@sina.com X-Auth-ID: hdanton@sina.com X-SMAIL-MID: 81222554919385 From: Hillf Danton To: Tetsuo Handa Cc: Hillf Danton , Tejun Heo , agruenba@redhat.com, linux-mm@kvack.org, Waiman Long , linux-kernel@vger.kernel.org, rpeterso@redhat.com, syzkaller-bugs@googlegroups.com, syzbot Subject: Re: [syzbot] INFO: task hung in freeze_super (3) Date: Sun, 8 Jan 2023 20:07:47 +0800 Message-Id: <20230108120747.5268-1-hdanton@sina.com> In-Reply-To: <45699174-cb58-d57d-4c72-c0ae7622aeac@I-love.SAKURA.ne.jp> References: <20230104040132.4103-1-hdanton@sina.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Queue-Id: 2846518000C X-Rspamd-Server: rspam01 X-Stat-Signature: 136hxkn3fixzawhdtwa13xryk4jn49nm X-HE-Tag: 1673179681-731090 X-HE-Meta: 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 8 Jan 2023 20:11:55 +0900 Tetsuo Handa > On 2023/01/04 13:01, Hillf Danton wrote: > > > > syz-executor330/3631 kworker/0:1H/120 > > --- --- > > down_write_nested(&s->s_umount); > > glock_work_func() > > down_write(&sb->s_umount); > > flush_workqueue(glock_workqueue); > > > > > > No deadlock is reported yet. Whyyy? > > See if extending the aperture of wq->lockdep_map can catch it. > > As far as I tested, this patch did not change likeliness of hitting lockdep warning. > I feel that it was just by chance that this test request was able to hit lockdep warning. cpu0 cpu1 --- --- lock A work B runs a) lock_map_acquire(&wq->lockdep_map); __flush_workqueue lock_map_acquire(&wq->lockdep_map); lock_map_release(&wq->lockdep_map); b) lock_map_acquire(&wq->lockdep_map); lock A Currently report of deadlock escapes in mode b) because worker takes workqueue lockdep_map after flusher releases it. After this change, mode b) could be caught with no exception. cpu0 cpu1 --- --- lock A work B runs a) lock_map_acquire(&wq->lockdep_map); __flush_workqueue lock_map_acquire(&wq->lockdep_map); b) lock_map_acquire(&wq->lockdep_map); lock A