linux-kernel - Re: [RFC PATCH(Experimental) 1/4] freezer-cpu-hotplug core

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Message-Id: <200702161029.21560.rjw@sisk.pl>
Date:	Fri, 16 Feb 2007 10:29:20 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	vatsa@...ibm.com
Cc:	Oleg Nesterov <oleg@...sign.ru>, Gautham R Shenoy <ego@...ibm.com>,
	akpm@...l.org, paulmck@...ibm.com, mingo@...e.hu,
	dipankar@...ibm.com, venkatesh.pallipadi@...el.com,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH(Experimental) 1/4] freezer-cpu-hotplug core

On Friday, 16 February 2007 09:12, Srivatsa Vaddagiri wrote:
> On Fri, Feb 16, 2007 at 12:46:17PM +0530, Srivatsa Vaddagiri wrote:
> > frozen. The only exception is cleaning up of per-cpu threads (which is
> > not possible with processes frozen - if we can find a way to make that
> > possible, then everything can be done in CPU_DEAD).
> 
> How abt a patch like below?
> 
> 
> --- process.c.org	2007-02-16 13:38:39.000000000 +0530
> +++ process.c	2007-02-16 13:38:59.000000000 +0530
> @@ -47,7 +47,7 @@ void refrigerator(void)
>  	recalc_sigpending(); /* We sent fake signal, clean it up */
>  	spin_unlock_irq(&current->sighand->siglock);
>  
> -	while (frozen(current)) {
> +	while (frozen(current) && !kthread_should_stop()) {
>  		current->state = TASK_UNINTERRUPTIBLE;
>  		schedule();
>  	}
> 
> This should let us do kthread_stop() in CPU_DEAD itself (while processes
> are frozen)? That would allow us to do everything from CPU_DEAD itself
> (and not have CPU_DEAD_KILL_THREADS).

Well, the suspend code has been developed with the assumption that frozen
threads stay frozen until _we_ let them thaw by calling thaw_processes().  I'm
a bit afraid of this change.

Greetings,
Rafael
-
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