Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754540AbYLBL5k (ORCPT ); Tue, 2 Dec 2008 06:57:40 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752077AbYLBL5c (ORCPT ); Tue, 2 Dec 2008 06:57:32 -0500 Received: from wavehammer.waldi.eu.org ([82.139.201.20]:60011 "EHLO wavehammer.waldi.eu.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751844AbYLBL5b (ORCPT ); Tue, 2 Dec 2008 06:57:31 -0500 Date: Tue, 2 Dec 2008 12:57:29 +0100 From: Bastian Blank To: Sukadev Bhattiprolu Cc: Greg Kurz , linux-kernel@vger.kernel.org, oleg@redhat.com, ebiederm@xmission.com, containers@lists.osdl.org, roland@redhat.com, xemul@openvz.org Subject: Re: [RFC][PATCH 2/5] pid: Generalize task_active_pid_ns Message-ID: <20081202115729.GB1132@wavehammer.waldi.eu.org> Mail-Followup-To: Bastian Blank , Sukadev Bhattiprolu , Greg Kurz , linux-kernel@vger.kernel.org, oleg@redhat.com, ebiederm@xmission.com, containers@lists.osdl.org, roland@redhat.com, xemul@openvz.org References: <20081126034242.GA23120@us.ibm.com> <20081126034528.GB23238@us.ibm.com> <20081127011738.GC13545@wavehammer.waldi.eu.org> <1227820765.5108.20.camel@bahia.kalilou.org> <20081201211518.GB15004@us.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20081201211518.GB15004@us.ibm.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1620 Lines: 37 On Mon, Dec 01, 2008 at 01:15:18PM -0800, Sukadev Bhattiprolu wrote: > Greg Kurz [gkurz@fr.ibm.com] wrote: > | On Thu, 2008-11-27 at 02:17 +0100, Bastian Blank wrote: > | > On Tue, Nov 25, 2008 at 07:45:28PM -0800, Sukadev Bhattiprolu wrote: > | > > Currently task_active_pid_ns is not safe to call after a > | > > task becomes a zombie and exit_task_namespaces is called, > | > > as nsproxy becomes NULL. > | > Why do you need to be able to get the pid namespace from zombie > | > processes? > After exiting namespaces, the process notifies parent. With new changes > to signals (in this patchset), the signal code may need to determine > the namespace of sender (the exiting child in this case). So the parent of a process with a new pid namespace will never get a SIGCHLD? What I read in the kernel source (kernel/signal.c:do_notify_parent, include/asm-generic/siginfo.h:CLD_EXITED) is that the exit signals (SIGCHLD) are describes as sent by the kernel. > | I agree with Eric and Sukadev that task_active_pid_ns() is unsafe. There > | isn't even a /* don't use with zombies */ in pid_namespace.h... > Hmm. Its not unsafe at present. It would become unsafe if the signals code > tries to determine the namespace of sender. Why? Even now it may be used on zombie tasks. Bastian -- Vulcans do not approve of violence. -- Spock, "Journey to Babel", stardate 3842.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/