linux-kernel - Re: NFS causing oops when freeing namespace

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Message-ID: <20070117225524.GA1572@tv-sign.ru>
Date:	Thu, 18 Jan 2007 01:55:24 +0300
From:	Oleg Nesterov <oleg@...sign.ru>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Cedric Le Goater <clg@...ibm.com>,
	Daniel Hokka Zakrisson <daniel@...ac.com>,
	linux-kernel@...r.kernel.org, herbert@...hfloor.at, akpm@...l.org,
	trond.myklebust@....uio.no,
	Linux Containers <containers@...ts.osdl.org>
Subject: Re: NFS causing oops when freeing namespace

On 01/17, Eric W. Biederman wrote:
>
> Cedric Le Goater <clg@...ibm.com> writes:
> >
> > your first analysis was correct : exit_task_namespaces() should be moved 
> > above exit_notify(tsk). It will require some extra fixes for nsproxy 
> > though.
> 
> I think the only issue is the child_reaper and currently we only have one of
> those.  When we really do the pid namespace we are going to have to revisit
> this.  My gut feel says that we won't be able to exit our pid namespace until
> the process is waited on.  So we may need to break up exit_task_namespace into
> individual components.

I agree, but please note that the child_reaper is not the only issue. Think
about sub-thread which auto-reaps itself. I'd suggest to add the comment in
do_exit() after exit_notify() to remind that the task is really dead now, it
has no ->signal, it can't be seen in /proc/, we can't send a signal to it, etc.

Oleg.

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