From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757325AbXJCOWq (ORCPT ); Wed, 3 Oct 2007 10:22:46 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754826AbXJCOWg (ORCPT ); Wed, 3 Oct 2007 10:22:36 -0400 Received: from sacred.ru ([62.205.161.221]:41755 "EHLO sacred.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754811AbXJCOWg (ORCPT ); Wed, 3 Oct 2007 10:22:36 -0400 Message-ID: <4703A4D5.3000100@openvz.org> Date: Wed, 03 Oct 2007 18:19:01 +0400 From: Pavel Emelyanov User-Agent: Thunderbird 2.0.0.6 (X11/20070728) MIME-Version: 1.0 To: Andrew Morton CC: Sukadev Bhattiprolu , Linux Kernel Mailing List , devel@openvz.org, Matt Mackall Subject: [PATCH 1/3] Introduce the dummy_pid References: <4703A44F.9020402@openvz.org> In-Reply-To: <4703A44F.9020402@openvz.org> 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]); Wed, 03 Oct 2007 18:21:24 +0400 (MSD) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org 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); + int is_cgroup_init(struct task_struct *tsk) { int ret = 0; @@ -339,7 +350,7 @@ void fastcall detach_pid(struct task_str pid = link->pid; hlist_del_rcu(&link->node); - link->pid = NULL; + link->pid = &dummy_pid; for (tmp = PIDTYPE_MAX; --tmp >= 0; ) if (!hlist_empty(&pid->tasks[tmp])) @@ -354,7 +365,7 @@ void fastcall transfer_pid(struct task_s { new->pids[type].pid = old->pids[type].pid; hlist_replace_rcu(&old->pids[type].node, &new->pids[type].node); - old->pids[type].pid = NULL; + old->pids[type].pid = &dummy_pid; } struct task_struct * fastcall pid_task(struct pid *pid, enum pid_type type)