linux-kernel - Re: [RFC][PATCH -mm] Freezer: Handle uninterruptible tasks

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Message-Id: <200707070056.22560.rjw@sisk.pl>
Date:	Sat, 7 Jul 2007 00:56:21 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Oleg Nesterov <oleg@...sign.ru>
Cc:	Alan Stern <stern@...land.harvard.edu>,
	linux-kernel@...r.kernel.org,
	Nigel Cunningham <nigel@...el.suspend2.net>
Subject: Re: [RFC][PATCH -mm] Freezer: Handle uninterruptible tasks

On Friday, 6 July 2007 22:26, Oleg Nesterov wrote:
> Rafael J. Wysocki wrote:
> >
> > This patch makes the freezer skip uninterruptible user space tasks (ie. such
> > that have an mm of their own) when counting the tasks to be frozen.  As a
> > result, these tasks have the TIF_FREEZE and TIF_SIGPENDING flags set, but the
> > freezer doesn't wait for them to enter the refrigerator.  Nevertheless, they
> > will enter the refrigerator as soon as they change their state.
> 
> A small correction: they will enter the refrigerator on return to user-space.

Yes, I should have written that explicitly.

> Actually, TASK_INTERRUPTIBLE doesn't mean the task actually sleeps. It could
> be running or preempted... I am a bit worried :)

Fortunately, similar approach has been tested quite extensively by suspend2,
IIRC. :-)
 
> > +static int freezer_should_skip(struct task_struct *p)
> > +{
> > +       return (has_mm(p) && (p->state | TASK_UNINTERRUPTIBLE));
>                                         ^^^
> I guess you meant "&", not "|".

Yes, I've already spotted that, but thanks anyway.

Greetings,
Rafael


-- 
"Premature optimization is the root of all evil." - Donald Knuth
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