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=-3.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_RED 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 E9281C07E9B for ; Wed, 7 Jul 2021 15:06:52 +0000 (UTC) Received: from smtp3.osuosl.org (smtp3.osuosl.org [140.211.166.136]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 9D5C861CC1 for ; Wed, 7 Jul 2021 15:06:52 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9D5C861CC1 Authentication-Results: mail.kernel.org; dmarc=pass (p=none dis=none) header.from=linuxfoundation.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linux-kernel-mentees-bounces@lists.linuxfoundation.org Received: from localhost (localhost [127.0.0.1]) by smtp3.osuosl.org (Postfix) with ESMTP id 6CD9F6059B; Wed, 7 Jul 2021 15:06:52 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp3.osuosl.org ([127.0.0.1]) by localhost (smtp3.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id xkyqyWVqJzYf; Wed, 7 Jul 2021 15:06:51 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [IPv6:2605:bc80:3010:104::8cd3:938]) by smtp3.osuosl.org (Postfix) with ESMTPS id 95679606B0; Wed, 7 Jul 2021 15:06:51 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 819D3C001A; Wed, 7 Jul 2021 15:06:51 +0000 (UTC) Received: from smtp3.osuosl.org (smtp3.osuosl.org [IPv6:2605:bc80:3010::136]) by lists.linuxfoundation.org (Postfix) with ESMTP id 3C7D3C000E for ; Wed, 7 Jul 2021 15:06:50 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp3.osuosl.org (Postfix) with ESMTP id 2B530606B0 for ; Wed, 7 Jul 2021 15:06:50 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp3.osuosl.org ([127.0.0.1]) by localhost (smtp3.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id LKZApfoSsPr8 for ; Wed, 7 Jul 2021 15:06:49 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.8.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp3.osuosl.org (Postfix) with ESMTPS id 9A5E66059B for ; Wed, 7 Jul 2021 15:06:49 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id 6909F61CC0; Wed, 7 Jul 2021 15:06:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1625670409; bh=meAqswieIwvglWxHVG7o8tCUh+PaGXqIKM7610mdBRE=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ifbyG30kR+elhqc/M7He0RvljFsanuwgzukhqgOpYhpFwIv6TlI3xLqSyR8zlzOhe ikdopdgkXRGXAyM6+aoYSirbsi5uysEeK53V+65DvNbMd+Zr181AfBVyMJ8F5IbL33 oWCITkCkZT4ZbHdhBbxw7htM3HIjzS9QJ8mtY7ow= Date: Wed, 7 Jul 2021 17:06:45 +0200 From: Greg KH To: "J. Bruce Fields" Subject: Re: [PATCH v2 1/2] fcntl: fix potential deadlocks for &fown_struct.lock Message-ID: References: <20210707023548.15872-1-desmondcheongzx@gmail.com> <20210707023548.15872-2-desmondcheongzx@gmail.com> <14633c3be87286d811263892375f2dfa9a8ed40a.camel@kernel.org> <4dda1cad6348fced5fcfcb6140186795ed07d948.camel@kernel.org> <20210707135129.GA9446@fieldses.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20210707135129.GA9446@fieldses.org> Cc: syzbot+e6d5398a02c516ce5e70@syzkaller.appspotmail.com, Jeff Layton , linux-kernel@vger.kernel.org, viro@zeniv.linux.org.uk, linux-fsdevel@vger.kernel.org, Desmond Cheong Zhi Xi , linux-kernel-mentees@lists.linuxfoundation.org X-BeenThere: linux-kernel-mentees@lists.linuxfoundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-kernel-mentees-bounces@lists.linuxfoundation.org Sender: "Linux-kernel-mentees" On Wed, Jul 07, 2021 at 09:51:29AM -0400, J. Bruce Fields wrote: > 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? You never use WARN or BUG, unless the system is so messed up that you can not possibly recover from the issue. Don't be lazy, handle the error properly and report it upwards. thanks, greg k-h _______________________________________________ Linux-kernel-mentees mailing list Linux-kernel-mentees@lists.linuxfoundation.org https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees