From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758818AbXJDJAQ (ORCPT ); Thu, 4 Oct 2007 05:00:16 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754254AbXJDJAA (ORCPT ); Thu, 4 Oct 2007 05:00:00 -0400 Received: from sacred.ru ([62.205.161.221]:58852 "EHLO sacred.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753939AbXJDI77 (ORCPT ); Thu, 4 Oct 2007 04:59:59 -0400 Message-ID: <4704AAC5.2040701@openvz.org> Date: Thu, 04 Oct 2007 12:56:37 +0400 From: Pavel Emelyanov User-Agent: Thunderbird 2.0.0.6 (X11/20070728) MIME-Version: 1.0 To: Randy Dunlap CC: Andrew Morton , Sukadev Bhattiprolu , Linux Kernel Mailing List , devel@openvz.org, Matt Mackall Subject: Re: [PATCH 1/3] Introduce the dummy_pid References: <4703A44F.9020402@openvz.org> <4703A4D5.3000100@openvz.org> <20071003110610.08156d75.randy.dunlap@oracle.com> In-Reply-To: <20071003110610.08156d75.randy.dunlap@oracle.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Greylist: Sender succeeded SMTP AUTH authentication, not delayed by milter-greylist-3.0 (sacred.ru [62.205.161.221]); Thu, 04 Oct 2007 12:59:02 +0400 (MSD) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Randy Dunlap wrote: > On Wed, 03 Oct 2007 18:19:01 +0400 Pavel Emelyanov wrote: > >> This is a pid which is attached to tasks when they detach >> their pids. This is done in detach_pid() and transfer_pid(). >> The pid_alive() check is changed to reflect this fact. >> >> Signed-off-by: Pavel Emelyanov >> >> --- >> >> diff --git a/include/linux/sched.h b/include/linux/sched.h >> index 4f21af1..e17b8f8 100644 >> --- a/include/linux/sched.h >> +++ b/include/linux/sched.h >> @@ -1286,9 +1286,11 @@ static inline pid_t task_ppid_nr_ns(stru >> * If pid_alive fails, then pointers within the task structure >> * can be stale and must not be dereferenced. >> */ >> +extern struct pid dummy_pid; >> + >> static inline int pid_alive(struct task_struct *p) >> { >> - return p->pids[PIDTYPE_PID].pid != NULL; >> + return p->pids[PIDTYPE_PID].pid != &dummy_pid; >> } >> >> /** >> diff --git a/kernel/pid.c b/kernel/pid.c >> index d7388d7..b7a11cf 100644 >> --- a/kernel/pid.c >> +++ b/kernel/pid.c >> @@ -81,6 +81,17 @@ struct pid_namespace init_pid_ns = { >> }; >> EXPORT_SYMBOL_GPL(init_pid_ns); >> >> +struct pid dummy_pid = { >> + .count = ATOMIC_INIT(1), >> + .numbers = { { >> + .nr = 0, /* this is what pid_nr will return >> + * for tasks with no pids >> + */ >> + .ns = &init_pid_ns, >> + }, } >> +}; >> +EXPORT_SYMBOL(dummy_pid); > > Why is the EXPORT_SYMBOL() needed? Because pid_alive() uses it and is declared in sched.h, so some module can use it. > IOW, is some loadable module going to use this? Right now - no modules use it. You're right - I will remove this export. > --- > ~Randy >