linux-kernel - Re: [PATCH 06/16] freezer: make exiting tasks properly unfreezable

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Message-ID: <20110823194451.GH2803@mtj.dyndns.org>
Date:	Tue, 23 Aug 2011 21:44:51 +0200
From:	Tejun Heo <tj@...nel.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	rjw@...k.pl, menage@...gle.com, linux-kernel@...r.kernel.org,
	arnd@...db.de
Subject: Re: [PATCH 06/16] freezer: make exiting tasks properly unfreezable

Hello,

On Tue, Aug 23, 2011 at 05:52:21PM +0200, Oleg Nesterov wrote:
> > @@ -915,6 +913,12 @@ NORET_TYPE void do_exit(long code)
> >
> >  	ptrace_event(PTRACE_EVENT_EXIT, code);
> >
> > +	/*
> > +	 * With ptrace notification done, there's no point in freezing from
> > +	 * here on.  Disallow freezing.
> > +	 */
> > +	current->flags |= PF_NOFREEZE;
> 
> OK, but what PF_NOFREEZE actually means?
> 
> Apart from "dont try to freeze" it means "no need to freeze", yes?

Yes.

> IOW, try_to_freeze_tasks() can succeed even if we have a lot of
> exitinig task which can make some activity, say, disk i/o. Is this
> correct?

Hmmm... can it cause disk IOs after that point?  I skimmed through and
couldn't spot one (the original code made simliar assumption albeit a
bit later).

Thanks.

-- 
tejun
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