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 E88EEC48BCD for ; Wed, 9 Jun 2021 21:56:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CD702613E1 for ; Wed, 9 Jun 2021 21:56:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230203AbhFIV6b (ORCPT ); Wed, 9 Jun 2021 17:58:31 -0400 Received: from cloud48395.mywhc.ca ([173.209.37.211]:44030 "EHLO cloud48395.mywhc.ca" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229639AbhFIV6a (ORCPT ); Wed, 9 Jun 2021 17:58:30 -0400 Received: from modemcable064.203-130-66.mc.videotron.ca ([66.130.203.64]:51958 helo=[192.168.1.179]) by cloud48395.mywhc.ca with esmtpsa (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.94.2) (envelope-from ) id 1lr6Bb-0002oY-I6; Wed, 09 Jun 2021 17:56:31 -0400 Message-ID: <8880aac1e81ac38928f58da2d29057cb69139d8c.camel@trillion01.com> Subject: Re: [RFC] coredump: Do not interrupt dump for TIF_NOTIFY_SIGNAL From: Olivier Langlois To: "Eric W. Biederman" Cc: Linus Torvalds , Linux Kernel Mailing List , linux-fsdevel , io-uring , Alexander Viro , Jens Axboe , "Pavel Begunkov>" , Oleg Nesterov Date: Wed, 09 Jun 2021 17:56:30 -0400 In-Reply-To: References: <192c9697e379bf084636a8213108be6c3b948d0b.camel@trillion01.com> <9692dbb420eef43a9775f425cb8f6f33c9ba2db9.camel@trillion01.com> <87h7i694ij.fsf_-_@disp2133> <198e912402486f66214146d4eabad8cb3f010a8e.camel@trillion01.com> <87eeda7nqe.fsf@disp2133> Organization: Trillion01 Inc Content-Type: text/plain; charset="ISO-8859-1" User-Agent: Evolution 3.40.2 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - cloud48395.mywhc.ca X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - trillion01.com X-Get-Message-Sender-Via: cloud48395.mywhc.ca: authenticated_id: olivier@trillion01.com X-Authenticated-Sender: cloud48395.mywhc.ca: olivier@trillion01.com X-Source: X-Source-Args: X-Source-Dir: Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On Wed, 2021-06-09 at 17:26 -0400, Olivier Langlois wrote: > On Wed, 2021-06-09 at 16:05 -0500, Eric W. Biederman wrote: > > > > > > So the TIF_NOTIFY_SIGNAL does get set WHILE the core dump is > > > written. > > > > Did you mean? > > > > So the TIF_NOTIFY_SIGNAL does _not_ get set WHILE the core dump is > > written. > > > > > Absolutely not. I did really mean what I have said. Bear with me > that, > I am not qualifying myself as an expert kernel dev yet so feel free > to > correct me if I say some heresy... > > io_uring is placing my task in my TCP socket wait queue because it > wants to read data from it. > > The task returns to user space and core dump with a SEGV. > > now my understanding is that the code that is waking up tasks, it is > the NIC driver interrupt handler which can occur while the core dump > is > written. > > does that make sense? > > my testing is telling me that this is exactly what happens... > > Another thing to know is that dump_interrupted() isn't only called from do_coredump(). At first, I did the mistake to think that if dump_interrupt() was returning false when called from do_coredump() all was good. It is not the case. dump_interrupted() is also called from dump_emit() which is called from several places by functions inside binfmt_elf.c So dump_interrupted() is called several times during the coredump generation.