linux-kernel - Re: [PATCH v2 0/3] make vfork killable

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Message-ID: <20110815194209.GA19239@redhat.com>
Date:	Mon, 15 Aug 2011 21:42:09 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Roland McGrath <roland@...k.frob.com>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Matt Fleming <matt.fleming@...ux.intel.com>,
	linux-kernel@...r.kernel.org, Pavel Machek <pavel@....cz>
Subject: Re: [PATCH v2 0/3] make vfork killable

Hi Tejun,

On 08/13, Tejun Heo wrote:
>
> Hello, Oleg.
>
> On Fri, Aug 12, 2011 at 07:55:50PM +0200, Oleg Nesterov wrote:
> > > an alternative approach
> > > could be handling vfork waiting as a type of job control stop.
> >
> > Well, I didn't see the code, but to be honest this doesn't look
> > like a good idea to me. Firstly, personally I do not think this
> > has something to do with the job control stop.
> >
> > And, to me sys_restart_syscall() looks like the very natural
> > approach, and simple.
>
> I've been playing with this and it does a bit further than
> implementation simplicity.  Currently, we have three different modes
> of stopping a task.
>
> * Regular job control and ptrace.
> * vfork wait.
> * cgroup freeze.

I still can't understand what exactly you have in mind.

And to me vfork() is closer to nanoslep() than to cgroup_freezer.
(As for cgroup_freezer, I agree it would be nice to reimplent it
 in any case).

> The downside is that that wouldn't work with cgroup freeze at
> all - there's no syscall to restart.

Sure. Still I don't understand why restart is not suitable for vfork
and why it would be better to unify freezer/vfork.

OK. Let's discuss this later, I hope you will cc me ;)


But what do you think about this series? It is simple, it doesn't
play with restarts. In some sense it even simplifies the code because
it removes one user of ->vfork_done. I don't think these patches can
complicate the further changes you are going to do.

No?

Oleg.

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