linux-kernel - Re: [PATCH 0/3] Add OMAP hardware spinlock misc driver

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Message-ID: <1287412383.29097.1603.camel@twins>
Date:	Mon, 18 Oct 2010 16:33:03 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Ohad Ben-Cohen <ohad@...ery.com>
Cc:	Russell King - ARM Linux <linux@....linux.org.uk>,
	Hari Kanigeri <h-kanigeri2@...com>, Suman Anna <s-anna@...com>,
	Benoit Cousson <b-cousson@...com>,
	Tony Lindgren <tony@...mide.com>, Greg KH <greg@...ah.com>,
	linux-kernel@...r.kernel.org,
	Grant Likely <grant.likely@...retlab.ca>,
	akpm@...ux-foundation.org, linux-omap@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 0/3] Add OMAP hardware spinlock misc driver

On Mon, 2010-10-18 at 16:28 +0200, Ohad Ben-Cohen wrote:
> On Mon, Oct 18, 2010 at 3:43 PM, Peter Zijlstra <peterz@...radead.org> wrote:
> > Right, so the problem is that there simply is no way to do atomic memory
> > access from these auxiliary processing units wrt the main CPU?
> 
> Yes. There are a few relevant system-wide limitations, one of them is
> that simply the system interconnect does not support those fancy
> atomic operations.

Does it support full memory coherency though? Otherwise I can see memory
based message passing becoming rather interesting.

Without coherency everybody needs to be damn sure to flush the relevant
bits before unlocking and such.


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