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=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 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 0DF48C4363A for ; Mon, 26 Oct 2020 11:55:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D892E22263 for ; Mon, 26 Oct 2020 11:55:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1774546AbgJZLzn (ORCPT ); Mon, 26 Oct 2020 07:55:43 -0400 Received: from mx2.suse.de ([195.135.220.15]:37104 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1422402AbgJZLzn (ORCPT ); Mon, 26 Oct 2020 07:55:43 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id F1179AC8B; Mon, 26 Oct 2020 11:55:41 +0000 (UTC) Received: by quack2.suse.cz (Postfix, from userid 1000) id B3F9A1E10F5; Mon, 26 Oct 2020 12:55:41 +0100 (CET) Date: Mon, 26 Oct 2020 12:55:41 +0100 From: Jan Kara To: Peter Zijlstra Cc: Filipe Manana , LKML , Jan Kara , David Sterba Subject: Re: possible lockdep regression introduced by 4d004099a668 ("lockdep: Fix lockdep recursion") Message-ID: <20201026115541.GC28769@quack2.suse.cz> References: <20201026114009.GN2594@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201026114009.GN2594@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon 26-10-20 12:40:09, Peter Zijlstra wrote: > On Mon, Oct 26, 2020 at 11:26:49AM +0000, Filipe Manana wrote: > > Hello, > > > > I've recently started to hit a warning followed by tasks hanging after > > attempts to freeze a filesystem. A git bisection pointed to the > > following commit: > > > > commit 4d004099a668c41522242aa146a38cc4eb59cb1e > > Author: Peter Zijlstra > > Date: Fri Oct 2 11:04:21 2020 +0200 > > > > lockdep: Fix lockdep recursion > > > > This happens very reliably when running all xfstests with lockdep > > enabled, and the tested filesystem is btrfs (haven't tried other > > filesystems, but it shouldn't matter). The warning and task hangs always > > happen at either test generic/068 or test generic/390, and (oddly) > > always have to run all tests for it to trigger, running those tests > > individually on an infinite loop doesn't seem to trigger it (at least > > for a couple hours). > > > > The warning triggered is at fs/super.c:__sb_start_write() which always > > results later in several tasks hanging on a percpu rw_sem: > > > > https://pastebin.com/qnLvf94E > > > > What happens is percpu_rwsem_is_held() is apparently returning a false > > positive, > > That smells like the same issue reported here: > > https://lkml.kernel.org/r/20201022111700.GZ2651@hirez.programming.kicks-ass.net > > Make sure you have commit: > > f8e48a3dca06 ("lockdep: Fix preemption WARN for spurious IRQ-enable") > > (in Linus' tree by now) and do you have CONFIG_DEBUG_PREEMPT enabled? Hum, I am at 5.10-rc1 now and above mentioned commit doesn't appear to be there? Also googling for the title doesn't help... Honza -- Jan Kara SUSE Labs, CR