linux-kernel - Re: [PATCH 5/7] pid: rewrite task helper function is_global

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Message-ID: <20140220183958.GB23993@redhat.com>
Date:	Thu, 20 Feb 2014 19:39:58 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Richard Guy Briggs <rgb@...hat.com>
Cc:	linux-audit@...hat.com, linux-kernel@...r.kernel.org,
	eparis@...hat.com, sgrubb@...hat.com, akpm@...ux-foundation.org,
	peterz@...radead.org, "Eric W. Biederman" <ebiederm@...ssion.com>
Subject: Re: [PATCH 5/7] pid: rewrite task helper function is_global_init()
	avoiding task->pid

On 01/23, Richard Guy Briggs wrote:
>
>  static inline int is_global_init(struct task_struct *tsk)
>  {
> -	return tsk->pid == 1;
> +	return task_pid_nr(tsk) == 1;
>  }

ACK, but we need to fix it.

With or without this change is_global_init() actually means
is-the-main-thread-of-global-init.

This is not what the callers actually want. Just look at
oom_unkillable_task(). Suppose that p is the sub-thread of
/sbin/init, if we kill this thread we kill the whole process.

The same of other callers. is_global_init() should return T
if this task is the part of init's thread group.

Oleg.

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