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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 3C5E7C169D4 for ; Tue, 16 Oct 2018 14:14:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0CB3C2086E for ; Tue, 16 Oct 2018 14:14:19 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0CB3C2086E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727217AbeJPWE4 (ORCPT ); Tue, 16 Oct 2018 18:04:56 -0400 Received: from mx1.redhat.com ([209.132.183.28]:33842 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727007AbeJPWEz (ORCPT ); Tue, 16 Oct 2018 18:04:55 -0400 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id E2E3E80F6D; Tue, 16 Oct 2018 14:14:14 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.34.27.30]) by smtp.corp.redhat.com (Postfix) with SMTP id D1D675D968; Tue, 16 Oct 2018 14:14:06 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Tue, 16 Oct 2018 16:14:14 +0200 (CEST) Date: Tue, 16 Oct 2018 16:14:06 +0200 From: Oleg Nesterov To: Enke Chen Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , x86@kernel.org, Peter Zijlstra , Arnd Bergmann , "Eric W. Biederman" , Khalid Aziz , Kate Stewart , Helge Deller , Greg Kroah-Hartman , Al Viro , Andrew Morton , Christian Brauner , Catalin Marinas , Will Deacon , Dave Martin , Mauro Carvalho Chehab , Michal Hocko , Rik van Riel , "Kirill A. Shutemov" , Roman Gushchin , Marcos Paulo de Souza , Dominik Brodowski , Cyrill Gorcunov , Yang Shi , Jann Horn , Kees Cook , linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, "Victor Kamensky (kamensky)" , xe-linux-external@cisco.com, Stefan Strogin , Eugene Syromiatnikov Subject: Re: [PATCH] kernel/signal: Signal-based pre-coredump notification Message-ID: <20181016141405.GA22045@redhat.com> References: <20181015120521.GA10146@redhat.com> <20398328-4ee1-96b2-5723-4b7eed55f0a2@cisco.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20398328-4ee1-96b2-5723-4b7eed55f0a2@cisco.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.27]); Tue, 16 Oct 2018 14:14:15 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/15, Enke Chen wrote: > > > I don't understand why we need valid_predump_signal() at all. > > Most of the signals have well-defined semantics, and would not be appropriate > for this purpose. you are going to change the rules anyway. > That is why it is limited to only SIGCHLD, SIGUSR1, SIGUSR2. Which do not queue. So the parent won't get the 2nd signal if 2 children crash at the same time. > >> if (sig_kernel_coredump(signr)) { > >> + /* > >> + * Notify the parent prior to the coredump if the > >> + * parent is interested in such a notificaiton. > >> + */ > >> + int p_sig = current->real_parent->predump_signal; > >> + > >> + if (valid_predump_signal(p_sig)) { > >> + read_lock(&tasklist_lock); > >> + do_notify_parent_predump(current); > >> + read_unlock(&tasklist_lock); > >> + cond_resched(); > > > > perhaps this should be called by do_coredump() after coredump_wait() kills > > all the sub-threads? > > proc_coredump_connector(current) is located here, they should stay together. Why? Once again, other threads are still alive. So if the parent restarts the service after it recieves -predump_signal, the new process can "race" with the old thread. Oleg.