linux-kernel - Re: [PATCH 1/8] Enhance process freezer interface for usage beyond software suspend

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Date:	Thu, 5 Apr 2007 15:30:55 +0400
From:	Oleg Nesterov <oleg@...sign.ru>
To:	Gautham R Shenoy <ego@...ibm.com>
Cc:	akpm@...ux-foundation.org, paulmck@...ibm.com,
	torvalds@...ux-foundation.org, linux-kernel@...r.kernel.org,
	vatsa@...ibm.com, "Rafael J. Wysocki" <rjw@...k.pl>, mingo@...e.hu,
	dipankar@...ibm.com, dino@...ibm.com,
	masami.hiramatsu.pt@...achi.com
Subject: Re: [PATCH 1/8] Enhance process freezer interface for usage beyond software suspend

On 04/05, Gautham R Shenoy wrote:
>
> On Thu, Apr 05, 2007 at 01:46:33PM +0400, Oleg Nesterov wrote:
> > 
> > > --- linux-2.6.21-rc5.orig/kernel/sched.c
> > > +++ linux-2.6.21-rc5/kernel/sched.c
> > > @@ -5057,6 +5057,7 @@ static int migration_thread(void *data)
> > >  	BUG_ON(rq->migration_thread != current);
> > >
> > >  	set_current_state(TASK_INTERRUPTIBLE);
> > > +	freezer_exempt(FE_ALL);
> > 
> > This is a real nitpick, but it was hard to me to understand this change.
> > Because it looks as if we have a subtle reason to set TASK_INTERRUPTIBLE
> > before freezer_exempt(). Unless I missed something, I'd suggest to move
> > freezer_exempt() up, before set_current_state().
> > 
> > The same for apm_mainloop().
> 
> Ok, no subtle reasons for freezer_exempt()ing after set_current_state().
> So no problems changing the order. But (just curious), is there any specific
> problem with this particular order ?

No, no, it was just a nitpick :) May be this is just me, but when I see the
code like

	set_current_state(TASK_XXX);
	something_which_doesnt_need_TASK_XXX();

, I can't read the code further, trying to understand where I was wrong
and why do we need to change task->state here.

Oleg.

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