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=-7.2 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,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 9E2EFC07E95 for ; Wed, 7 Jul 2021 13:51:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7E2BF61C89 for ; Wed, 7 Jul 2021 13:51:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231827AbhGGNyL (ORCPT ); Wed, 7 Jul 2021 09:54:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:60168 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229633AbhGGNyL (ORCPT ); Wed, 7 Jul 2021 09:54:11 -0400 Received: from fieldses.org (fieldses.org [IPv6:2600:3c00:e000:2f7::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 1D4B9C061574; Wed, 7 Jul 2021 06:51:30 -0700 (PDT) Received: by fieldses.org (Postfix, from userid 2815) id B9C216830; Wed, 7 Jul 2021 09:51:29 -0400 (EDT) DKIM-Filter: OpenDKIM Filter v2.11.0 fieldses.org B9C216830 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fieldses.org; s=default; t=1625665889; bh=gPeRkpFOKLgol1iXgNjO2sQ0E29J+JaZmTVNPoXkTRg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=jod3VyGB4DhCJ+ICEBNzHaBiknO3C7zMEnZQxrc/ZyshSnI1azu8Jh3xQnRFlipuj eR+qgYiI0+vGTgH8Xb8eLUH4XMWmI/sN5jqPPlWTVKuDy5O0oOHIgQ8MD1naUe/Bes pbR2I2qCyVrFFtcEFK4qe4dIzAbxSHnGFEFhyTJw= Date: Wed, 7 Jul 2021 09:51:29 -0400 From: "J. Bruce Fields" To: Jeff Layton Cc: Greg KH , Desmond Cheong Zhi Xi , viro@zeniv.linux.org.uk, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, skhan@linuxfoundation.org, linux-kernel-mentees@lists.linuxfoundation.org, syzbot+e6d5398a02c516ce5e70@syzkaller.appspotmail.com Subject: Re: [PATCH v2 1/2] fcntl: fix potential deadlocks for &fown_struct.lock Message-ID: <20210707135129.GA9446@fieldses.org> References: <20210707023548.15872-1-desmondcheongzx@gmail.com> <20210707023548.15872-2-desmondcheongzx@gmail.com> <14633c3be87286d811263892375f2dfa9a8ed40a.camel@kernel.org> <4dda1cad6348fced5fcfcb6140186795ed07d948.camel@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4dda1cad6348fced5fcfcb6140186795ed07d948.camel@kernel.org> User-Agent: Mutt/1.5.21 (2010-09-15) Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Wed, Jul 07, 2021 at 07:40:47AM -0400, Jeff Layton wrote: > On Wed, 2021-07-07 at 12:51 +0200, Greg KH wrote: > > On Wed, Jul 07, 2021 at 06:44:42AM -0400, Jeff Layton wrote: > > > On Wed, 2021-07-07 at 08:05 +0200, Greg KH wrote: > > > > On Wed, Jul 07, 2021 at 10:35:47AM +0800, Desmond Cheong Zhi Xi wrote: > > > > > + WARN_ON_ONCE(irqs_disabled()); > > > > > > > > If this triggers, you just rebooted the box :( > > > > > > > > Please never do this, either properly handle the problem and return an > > > > error, or do not check for this. It is not any type of "fix" at all, > > > > and at most, a debugging aid while you work on the root problem. > > > > > > > > thanks, > > > > > > > > greg k-h > > > > > > Wait, what? Why would testing for irqs being disabled and throwing a > > > WARN_ON in that case crash the box? > > > > If panic-on-warn is enabled, which is a common setting for systems these > > days. > > Ok, that makes some sense. Wait, I don't get it. How are we supposed to decide when to use WARN, when to use BUG, and when to panic? Do we really want to treat them all as equivalent? And who exactly is turning on panic-on-warn? --b.