linux-kernel - Re: [PATCH 09/25] xen: Account for time stolen by Xen

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Date:	Wed, 25 Apr 2007 20:15:06 +0200
From:	Andi Kleen <ak@...e.de>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	virtualization@...ts.osdl.org, lkml <linux-kernel@...r.kernel.org>,
	john stultz <johnstul@...ibm.com>,
	Keir Fraser <Keir.Fraser@...cam.ac.uk>
Subject: Re: [PATCH 09/25] xen: Account for time stolen by Xen

On Wednesday 25 April 2007 20:13:34 Jeremy Fitzhardinge wrote:
> Andi Kleen wrote:
> >> +
> >> +	do {
> >> +		state_time = state->state_entry_time;
> >> +		barrier();
> >>     
> >
> > Should be likely rmb
> 
> We discussed this, and decided that it wasn't necessary.  The state is
> always updated by the current CPU, so if it changes under our feet it
> will be because we were preempted, and so that should shoot down any
> speculated reads.

Then the barrier shouldn't be needed at all? 

Anyways needs comments

-Andi
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