linux-kernel - Re: 50 Watt idle power regression bisected to Linux-3.10

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Message-ID: <20131211174827.GB12431@gmail.com>
Date:	Wed, 11 Dec 2013 18:48:27 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Mike Galbraith <bitbucket@...ine.de>,
	Borislav Petkov <bp@...en8.de>, Len Brown <lenb@...nel.org>,
	Linux PM list <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Jeremy Eder <jeder@...hat.com>, x86@...nel.org
Subject: Re: 50 Watt idle power regression bisected to Linux-3.10


* Peter Zijlstra <peterz@...radead.org> wrote:

> On Wed, Dec 11, 2013 at 04:09:11PM +0100, Ingo Molnar wrote:
> > 
> > * Thomas Gleixner <tglx@...utronix.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
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