linux-kernel - Re: [PATCH] kthread_should_stop_check_freeze (was: Re: [PATCH -mm 3/7] Freezer: Remove PF

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Message-ID: <20070313054241.GB19071@in.ibm.com>
Date:	Tue, 13 Mar 2007 11:12:41 +0530
From:	Srivatsa Vaddagiri <vatsa@...ibm.com>
To:	Gautham R Shenoy <ego@...ibm.com>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>, Oleg Nesterov <oleg@...sign.ru>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Anton Blanchard <anton@...ba.org>,
	Andrew Morton <akpm@...l.org>, Pavel Machek <pavel@....cz>,
	LKML <linux-kernel@...r.kernel.org>,
	Aneesh Kumar <aneesh.kumar@...il.com>
Subject: Re: [PATCH] kthread_should_stop_check_freeze (was: Re: [PATCH -mm 3/7] Freezer: Remove PF_NOFREEZE from rcutorture thread)

On Tue, Mar 13, 2007 at 10:57:16AM +0530, Gautham R Shenoy wrote:
> CPU_DEAD:
> thaw_process(p);
> kthread_stop(p);
> p = NULL;

This neednt guarantee that the thread will see the stop request before
it exits the kthread_should_stop_freeze() function. There will always
be races .. So the only safe way for a thread to know whether it is time
to exit is:

	while (!kthread_should_stop_freeze()) {
		 if (!cpu_online(home_cpu)) 
			goto wait_to_die;

		...

	}

wait_to_die:

	while (!kthread_should_stop()) {
		/* sleep */
	}


-- 
Regards,
vatsa
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