linux-kernel - Re: [PATCH 4/4] pidns: Use task_active_pid

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Message-ID: <AANLkTikjcou-0b4NejpY66qXeZuzsC-M+oNTyHk=OE-Z@mail.gmail.com>
Date:	Mon, 31 Jan 2011 13:26:42 +0200
From:	Alexey Dobriyan <adobriyan@...il.com>
To:	Daniel Lezcano <daniel.lezcano@...e.fr>
Cc:	akpm@...ux-foundation.org, ebiederm@...ssion.com, oleg@...hat.com,
	containers@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org, clg@...ibm.com
Subject: Re: [PATCH 4/4] pidns: Use task_active_pid_ns where appropriate

On Mon, Jan 31, 2011 at 12:25 PM, Daniel Lezcano <daniel.lezcano@...e.fr> wrote:
> The expressions tsk->nsproxy->pid_ns and task_active_pid_ns
> aka ns_of_pid(task_pid(tsk)) should have the same number of
> cache line misses with the practical difference that
> ns_of_pid(task_pid(tsk)) is released later in a processes life.
>
> Furthermore by using task_active_pid_ns it becomes trivial
> to write an unshare implementation for the the pid namespace.
>
> So I have used task_active_pid_ns everywhere I can.

Yet current->nsproxy->pid_ns is way clearer.
Because live current always has pid_ns.

This task_active_pid_ns() is misnamed(?) because it does matter only
for dead tasks?

> -               current->nsproxy->pid_ns->last_pid);
> +               task_active_pid_ns(current)->last_pid);

I thought of doing exactly opposite patch :-)
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