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Date: Wed, 11 Dec 2013 18:48:27 +0100
From: Ingo Molnar <mingo@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>, Mike Galbraith <bitbucket@online.de>,
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        Jeremy Eder <jeder@redhat.com>, x86@kernel.org
Subject: Re: 50 Watt idle power regression bisected to Linux-3.10
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* Peter Zijlstra <peterz@infradead.org> wrote:

> On Wed, Dec 11, 2013 at 04:09:11PM +0100, Ingo Molnar wrote:
> > 
> > * Thomas Gleixner <tglx@linutronix.de> wrote:
> > 
> > > On Wed, 11 Dec 2013, Ingo Molnar wrote:
> > > > 
> > > > Another thing that is required I think is to issue a write barrier 
> > > > before CLFLUSH instruction. By my (possibly incorrect ...) reading of 
> > > > the documentation CLFLUSH does not appear to be ordered (at all), so 
> > > > it might execute before the modification to the affected memory?
> > > 
> > > We already have a write barrier in the code which modifies
> > > current_thread_info()->flags.
> > 
> > Which code is that, could you please cite it? (I tried finding it but 
> > my grep-fu failed me.)
> 
> current_set_polling_and_test().

Thx, those variants have the right barrier indeed.

Thanks,

	Ingo