linux-kernel - Re: [PATCH]: exec: avoid propagating PF_NO

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Message-ID: <20131128163803.GG10022@twins.programming.kicks-ass.net>
Date:	Thu, 28 Nov 2013 17:38:03 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Tejun Heo <htejun@...il.com>, zhang.yi20@....com.cn,
	lkml <linux-kernel@...r.kernel.org>,
	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
	Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH]: exec: avoid propagating PF_NO_SETAFFINITY into
 userspace child

On Thu, Nov 28, 2013 at 05:20:25PM +0100, Oleg Nesterov wrote:
> On 11/28, Peter Zijlstra wrote:
> >
> > On Thu, Nov 28, 2013 at 04:34:43PM +0100, Oleg Nesterov wrote:
> > > But note that in the longer term we might want even more. We probably
> > > want a non-daemonized thread controlled by the user-space. And even
> > > more, this thread should be per-namespace (this needs a lot more
> > > discussion).
> >
> > Which namespace? PID namespace I presume where we can have a 'new' init
> > task and everything.
> >
> > I'm not sure, are any of these things (workqueues, userspace helpers)
> > pid namespace aware? If not it doesn't seem to make sense to expose this
> > to nested PID namespaces and would be something special for the root
> > namespace.
> 
> Not sure I understand correctly. But yes, of course, it is not that
> call_usermodehelper() should be namespace-friendly "unconditionally".
> 
> We need another API (although perhaps we can simply add UMH_NAMESPACE
> flag, this doesn't matter).
> 
> Just for example, the piped core handler. Currently it is hardly useful
> in containers.

I'm afraid I'm not much familiar with the entire namespace thing other
than broad concepts.

But if there's specific per-pid-namespace functionality for
usermode-helpers, then yes it makes sense to have per-pid-namespace
parents.

So in specific, you say that piping a core file into a usermode helper
is currently busted in pid-namespaces and that fixing that would indeed
introduce such pid-namespace awareness to the usermode-helper stuff?
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