linux-kernel - Re: [PATCH] [20/28] x86: MCE: Switch x86 machine check handler to Monarch election. II

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Message-ID: <20090417135303.GP14687@one.firstfloor.org>
Date:	Fri, 17 Apr 2009 15:53:03 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Hidetoshi Seto <seto.hidetoshi@...fujitsu.com>, hpa@...or.com,
	linux-kernel@...r.kernel.org, mingo@...e.hu, tglx@...utronix.de
Subject: Re: [PATCH] [20/28] x86: MCE: Switch x86 machine check handler to Monarch election. II

On Fri, Apr 17, 2009 at 03:09:44PM +0200, Andi Kleen wrote:
> > > +
> > > +	/*
> > > +	 * Monarch starts executing now, the others wait.
> > > +	 */
> > > +	if (*order == 1) {
> > > +		atomic_set(&global_nwo, 0);
> > 
> > Monarch should clear global_nwo after all Subjects have read it.
> 
> The subjects don't care about the global nwo state, it only matters to the 
> Monarch who does the panic in mce_end(). The only exception would be timeout, 
> but in this case all the decisions are local only anyways.
> We ensure that all the subjects have written it first.

I thought some more about this and I think I was a little fast to dismiss
it due to the bank sharing heuristics. It's safer to indeed wait
for the subjects here too before clearing. I'll fix that up, thanks.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
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