linux-kernel - Re: [PATCH 14/16] freezer: make freezing() test freeze conditions in effect instead of TIF

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Date:	Mon, 29 Aug 2011 18:17:50 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	rjw@...k.pl, paul@...lmenage.org, linux-kernel@...r.kernel.org,
	arnd@...db.de
Subject: Re: [PATCH 14/16] freezer: make freezing() test freeze conditions
	in effect instead of TIF_FREEZE

On 08/29, Oleg Nesterov wrote:
>
> > @@ -120,13 +120,18 @@ int freeze_processes(void)
> >  {
> >  	int error;
> >
> > +	if (!pm_freezing)
> > +		atomic_inc(&system_freezing_cnt);
> > +
> >  	printk("Freezing user space processes ... ");
> > +	pm_freezing = true;
>
> and
>
> > @@ -146,6 +151,11 @@ void thaw_processes(void)
> >  {
> >  	struct task_struct *g, *p;
> >
> > +	if (pm_freezing)
> > +		atomic_dec(&system_freezing_cnt);
> > +	pm_freezing = false;
>
> I simply can't understand this... Why freeze_processes/thaw_processes
> check pm_freezing?

Ah, wait, I seem to understand.

> IIUC, the calls to freeze/thaw should be serialized anyway

Yes, and that is why this should actually work, I think.

Sorry for noise...

Oleg.

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