linux-kernel - Re: [patch] cpufreq: mark cpufreq_tsc() as core_initcall

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Message-ID: <20061127043323.GB5021@us.ibm.com>
Date:	Sun, 26 Nov 2006 20:33:23 -0800
From:	"Paul E. McKenney" <paulmck@...ibm.com>
To:	Oleg Nesterov <oleg@...sign.ru>
Cc:	Alan Stern <stern@...land.harvard.edu>,
	linux-kernel@...r.kernel.org
Subject: Re: [patch] cpufreq: mark cpufreq_tsc() as core_initcall_sync

On Fri, Nov 24, 2006 at 12:49:08AM +0300, Oleg Nesterov wrote:
> On 11/23, Paul E. McKenney wrote:
> >
> >                            For general use, I believe that this has
> > difficulties with the sequence of events I sent out on November 20th, see:
> >
> > http://marc.theaimsgroup.com/?l=linux-kernel&m=116397154808901&w=2
> >
> > ...
> >
> > I don't understand why an unlucky sequence of events mightn't be able
> > to hang this __wait_event().  Suppose we did the atomic_dec_and_test(),
> > then some other CPU executed xxx_read_unlock(), finding no one to awaken,
> > then we execute the __wait_event()?
> 
> Please note how ->ctr[] is initialized,
> 
> 	atomic_set(sp->ctr + 0, 1);	<---- 1, not 0
> 	atomic_set(sp->ctr + 1, 0);
> 
> atomic_read(sp->ctr + idx) == 0 means that this counter is inactive,
> nobody use it.

I definitely should have slept before commenting on the earlier version,
it would appear.  ;-)  Please accept my apologies for my confusion!

I will take a look at your later patch.

							Thanx, Paul
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