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 X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 3F161C4338F for ; Thu, 5 Aug 2021 19:45:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1EA5D60ED6 for ; Thu, 5 Aug 2021 19:45:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237055AbhHETpt (ORCPT ); Thu, 5 Aug 2021 15:45:49 -0400 Received: from outgoing-auth-1.mit.edu ([18.9.28.11]:51972 "EHLO outgoing.mit.edu" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S230107AbhHETpr (ORCPT ); Thu, 5 Aug 2021 15:45:47 -0400 Received: from cwcc.thunk.org (pool-72-74-133-215.bstnma.fios.verizon.net [72.74.133.215]) (authenticated bits=0) (User authenticated as tytso@ATHENA.MIT.EDU) by outgoing.mit.edu (8.14.7/8.12.4) with ESMTP id 175JjSBc017871 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Thu, 5 Aug 2021 15:45:29 -0400 Received: by cwcc.thunk.org (Postfix, from userid 15806) id 3A37315C3DD2; Thu, 5 Aug 2021 15:45:28 -0400 (EDT) Date: Thu, 5 Aug 2021 15:45:28 -0400 From: "Theodore Ts'o" To: Pavel Skripkin Cc: adilger.kernel@dilger.ca, johann@whamcloud.com, linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org, syzbot+c9ff4822a62eee994ea3@syzkaller.appspotmail.com Subject: Re: [PATCH] ext4: avoid huge mmp update interval value Message-ID: References: <20210805151418.30659-1-paskripkin@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210805151418.30659-1-paskripkin@gmail.com> Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org On Thu, Aug 05, 2021 at 06:14:18PM +0300, Pavel Skripkin wrote: > Syzbot reported task hung bug in ext4_fill_super(). The problem was in > too huge mmp update interval. > > Syzkaller reproducer setted s_mmp_update_interval to 39785 seconds. This > update interaval is unreasonable huge and it can cause tasks to hung on > kthread_stop() call, since it will wait until timeout timer expires. I must be missing something. kthread_stop() should wake up the kmmpd() thread, which should see kthread_should_stop(), and then it should exit. What is causing it to wait until the timeout timer expires? - Ted