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=0.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,UNWANTED_LANGUAGE_BODY,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 9B375C6786E for ; Fri, 26 Oct 2018 08:28:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 51C292082E for ; Fri, 26 Oct 2018 08:28:25 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 51C292082E 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 S1726217AbeJZRE3 (ORCPT ); Fri, 26 Oct 2018 13:04:29 -0400 Received: from mx1.redhat.com ([209.132.183.28]:45724 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725914AbeJZRE3 (ORCPT ); Fri, 26 Oct 2018 13:04:29 -0400 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 53462308A943; Fri, 26 Oct 2018 08:28:22 +0000 (UTC) Received: from dhcp-27-174.brq.redhat.com (unknown [10.43.17.106]) by smtp.corp.redhat.com (Postfix) with SMTP id 21815100164A; Fri, 26 Oct 2018 08:28:13 +0000 (UTC) Received: by dhcp-27-174.brq.redhat.com (nbSMTP-1.00) for uid 1000 oleg@redhat.com; Fri, 26 Oct 2018 10:28:22 +0200 (CEST) Date: Fri, 26 Oct 2018 10:28:13 +0200 From: Oleg Nesterov To: Enke Chen Cc: Thomas Gleixner , Ingo Molnar , Borislav Petkov , "H. Peter Anvin" , 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 , x86@kernel.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, "Victor Kamensky (kamensky)" , xe-linux-external@cisco.com, Stefan Strogin Subject: Re: [PATCH v4] kernel/signal: Signal-based pre-coredump notification Message-ID: <20181026082812.GA10581@redhat.com> References: <458c04d8-d189-4a26-729a-bb1d1d751534@cisco.com> <7741efa7-a3f8-62a1-ba52-613883164643@cisco.com> <84460a77-a111-404e-4bad-88104a6e246e@cisco.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <84460a77-a111-404e-4bad-88104a6e246e@cisco.com> User-Agent: Mutt/1.5.24 (2015-08-30) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.41]); Fri, 26 Oct 2018 08:28:23 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 10/25, Enke Chen wrote: > > +static void do_notify_parent_predump(void) > +{ > + struct task_struct *parent; > + int sig; > + > + read_lock(&tasklist_lock); > + parent = current->parent; > + sig = parent->signal->predump_signal; > + if (sig != 0) > + do_send_sig_info(sig, SEND_SIG_NOINFO, parent, PIDTYPE_TGID); > + read_unlock(&tasklist_lock); Ah. It is strange I didn't think about this before... Please, do not take tasklist_lock, use rcu_read_lock() instead. do_send_sig_info() uses the rcu-friendly lock_task_sighand(), so rcu_dereference(parent) should work fine. Oleg.