linux-kernel - Re: [PATCH 1/1] pid_ns: move pid_ns_release_proc() from proc_flush_task() to zap_pid_ns

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Date:	Thu, 24 Jun 2010 14:59:33 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Linux Containers <containers@...ts.osdl.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	linux-kernel@...r.kernel.org, Pavel Emelyanov <xemul@...nvz.org>
Subject: Re: [PATCH 1/1] pid_ns: move pid_ns_release_proc() from
	proc_flush_task() to zap_pid_ns_processes()

On 06/23, Sukadev Bhattiprolu wrote:
>
> Oleg Nesterov [oleg@...hat.com] wrote:
> | This is mostly cleanup and optimization, but also fixes the bug.
> |
> | proc_flush_task() checks upid->nr == 1 to detect the case when
> | a sub-namespace exits. However, this doesn't work in case when
> | a multithreaded init execs and calls release_task(old_leader),
> | the old leader has the same pid 1.
> |
> | Move pid_ns_release_proc() to zap_pid_ns_processes(), it is called
> | when we know for sure that init is exiting.
>
> Hmm, I almost agreed, but have a question :-)
>
> Yes, we know that the container-init is exiting. But if its parent (in
> the parent ns) waits on it and calls release_task(), won't we call
> proc_flush_task_mnt() on this container-init ? This would happen after
> dropping the mnt in zap_pid_ns_processes() no ?

Indeed. Thanks!

Somehow I forgot that init itself has not passed proc_flush_task().

Oleg.

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