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 02008C48BE0 for ; Wed, 9 Jun 2021 21:02:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D83B6613F1 for ; Wed, 9 Jun 2021 21:02:09 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229782AbhFIVED (ORCPT ); Wed, 9 Jun 2021 17:04:03 -0400 Received: from cloud48395.mywhc.ca ([173.209.37.211]:49874 "EHLO cloud48395.mywhc.ca" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229527AbhFIVED (ORCPT ); Wed, 9 Jun 2021 17:04:03 -0400 Received: from modemcable064.203-130-66.mc.videotron.ca ([66.130.203.64]:51954 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 1lr5Kw-0000ci-Vc; Wed, 09 Jun 2021 17:02:07 -0400 Message-ID: <198e912402486f66214146d4eabad8cb3f010a8e.camel@trillion01.com> Subject: Re: [RFC] coredump: Do not interrupt dump for TIF_NOTIFY_SIGNAL From: Olivier Langlois To: Linus Torvalds , "Eric W. Biederman" Cc: Linux Kernel Mailing List , linux-fsdevel , io-uring , Alexander Viro , Jens Axboe , "Pavel Begunkov>" , Oleg Nesterov Date: Wed, 09 Jun 2021 17:02:05 -0400 In-Reply-To: References: <192c9697e379bf084636a8213108be6c3b948d0b.camel@trillion01.com> <9692dbb420eef43a9775f425cb8f6f33c9ba2db9.camel@trillion01.com> <87h7i694ij.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 13:33 -0700, Linus Torvalds wrote: > Now, the fact that we haven't cleared TIF_NOTIFY_SIGNAL for the first > signal is clearly the immediate cause of this, but at the same time I > really get the feeling that that coredump aborting code should always > had used fatal_signal_pending(). I need clarify what does happen with the io_uring situation. If somehow, TIF_NOTIFY_SIGNAL wasn't cleared, I would get all the time a 0 byte size core dump because do_coredump() does check if the dump is interrupted before writing a single byte. io_uring is quite a strange animal. AFAIK, the common pattern to use a wait_queue is to insert a task into it and then put that task to sleep until the waited event occur. io_uring place tasks into wait queues and then let the the task return to user space to do some other stuff (like core dumping). I would guess that it is the main reason for it using the task_work feature. So the TIF_NOTIFY_SIGNAL does get set WHILE the core dump is written. Greetings, Olivier