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=-8.4 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_PASS,USER_IN_DEF_DKIM_WL 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 93D83C0044C for ; Mon, 29 Oct 2018 21:08:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4DFE12082D for ; Mon, 29 Oct 2018 21:08:40 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=cisco.com header.i=@cisco.com header.b="lQqP848S" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4DFE12082D Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=cisco.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 S1727408AbeJ3F7D (ORCPT ); Tue, 30 Oct 2018 01:59:03 -0400 Received: from rcdn-iport-8.cisco.com ([173.37.86.79]:34161 "EHLO rcdn-iport-8.cisco.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726016AbeJ3F7D (ORCPT ); Tue, 30 Oct 2018 01:59:03 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=cisco.com; i=@cisco.com; l=1386; q=dns/txt; s=iport; t=1540847318; x=1542056918; h=subject:to:cc:references:from:message-id:date: mime-version:in-reply-to:content-transfer-encoding; bh=P/xNm11nZw5q8XfeLANKDgWh2u4RRx89z45zxgwCwr0=; b=lQqP848SjkptHglgLK7E7VummqBioBpI+0zFA3YhTTL/wUHMTgej2ui8 Dqt5BRGUwoCqvrk3yGQEDQKO7Xvp0BgJ3r5ugXWFyIsQpDCdmWwGIkXYE +ZzkbTu98enAxhpXBScQLVOcKid++60YBK/NbSigHAEi7+gMxxfZTKYBp A=; X-IronPort-AV: E=Sophos;i="5.54,441,1534809600"; d="scan'208";a="471041775" Received: from rcdn-core-11.cisco.com ([173.37.93.147]) by rcdn-iport-8.cisco.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 29 Oct 2018 21:08:37 +0000 Received: from [10.154.208.144] ([10.154.208.144]) by rcdn-core-11.cisco.com (8.15.2/8.15.2) with ESMTP id w9TL8ZqX015061; Mon, 29 Oct 2018 21:08:36 GMT Subject: Re: [PATCH v4] kernel/signal: Signal-based pre-coredump notification To: Oleg Nesterov 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 , Enke Chen References: <458c04d8-d189-4a26-729a-bb1d1d751534@cisco.com> <7741efa7-a3f8-62a1-ba52-613883164643@cisco.com> <84460a77-a111-404e-4bad-88104a6e246e@cisco.com> <20181026082812.GA10581@redhat.com> <21f678a8-4001-df36-c26e-e96cf203b1b1@cisco.com> <20181029111804.GA24820@redhat.com> From: Enke Chen Message-ID: <634f9518-c742-16f0-84f4-90943af6aed2@cisco.com> Date: Mon, 29 Oct 2018 14:08:34 -0700 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.13; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20181029111804.GA24820@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Auto-Response-Suppress: DR, OOF, AutoReply X-Outbound-SMTP-Client: 10.154.208.144, [10.154.208.144] X-Outbound-Node: rcdn-core-11.cisco.com Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, Oleg: Yes, it should be the "real_parent" that is more interested in the notification. Will revert back. +static void do_notify_parent_predump(void) +{ + struct task_struct *parent; + int sig; + + rcu_read_lock(); + parent = rcu_dereference(current->real_parent); + sig = parent->signal->predump_signal; + if (sig != 0) + do_send_sig_info(sig, SEND_SIG_NOINFO, parent, PIDTYPE_TGID); + rcu_read_unlock(); +} Thanks. -- Enke On 10/29/18 4:18 AM, Oleg Nesterov wrote: > Hi, > > On 10/26, Enke Chen wrote: >> >> This is really a good idea given that "parent" is declared as RCU-protected. >> Just a bit odd, though, that the "parent" has not been accessed this way in >> the code base. > > It is acccessed when possible, > >> So just to confirm: the revised code would look like the following: >> >> static void do_notify_parent_predump(void) >> { >> struct task_struct *parent; >> int sig; >> >> rcu_read_lock(); >> parent = rcu_dereference(current->parent); >> sig = parent->signal->predump_signal; >> if (sig != 0) >> do_send_sig_info(sig, SEND_SIG_NOINFO, parent, PIDTYPE_TGID); >> rcu_read_unlock(); >> } > > Yes, this is what I meant. > > But I still think do_notify_parent_predump() should notify ->real_parent, > not ->parent. > > Oleg. >