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Date: Tue, 13 Mar 2007 11:12:41 +0530
From: Srivatsa Vaddagiri <vatsa@in.ibm.com>
To: Gautham R Shenoy <ego@in.ibm.com>
Cc: "Rafael J. Wysocki" <rjw@sisk.pl>, Oleg Nesterov <oleg@tv-sign.ru>,
       "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
       Anton Blanchard <anton@samba.org>, Andrew Morton <akpm@osdl.org>,
       Pavel Machek <pavel@ucw.cz>, LKML <linux-kernel@vger.kernel.org>,
       Aneesh Kumar <aneesh.kumar@gmail.com>
Subject: Re: [PATCH] kthread_should_stop_check_freeze (was: Re: [PATCH -mm 3/7] Freezer: Remove PF_NOFREEZE from rcutorture thread)
Message-ID: <20070313054241.GB19071@in.ibm.com>
Reply-To: vatsa@in.ibm.com
References: <200702260800.49603.rjw@sisk.pl> <20070303005843.GG2373@linux.vnet.ibm.com> <20070303173240.GA249@tv-sign.ru> <200703111849.09966.rjw@sisk.pl> <20070313052716.GA11982@in.ibm.com>
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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