Date: Fri, 11 Dec 2009 21:22:22 +0000
From: Russell King - ARM Linux <linux@arm.linux.org.uk>
To: Mikael Pettersson <mikpe@it.uu.se>
Cc: Jamie Iles <jamie.iles@picochip.com>, Ingo Molnar <mingo@elte.hu>,
       linux-kernel@vger.kernel.org, Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH 1/2] perf tools: allow building for ARM
Message-ID: <20091211212222.GD12628@n2100.arm.linux.org.uk>
References: <1260523260-15694-1-git-send-email-jamie.iles@picochip.com> <20091211102316.GB16882@elte.hu> <20091211103030.GC4164@wear.picochip.com> <20091211103848.GA9947@elte.hu> <20091211110111.GD4164@wear.picochip.com> <19234.11393.632298.555005@pilspetsen.it.uu.se>
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On Fri, Dec 11, 2009 at 12:26:57PM +0100, Mikael Pettersson wrote:
> The correct solution is to invoke a kernel-exported CPU-specific helper
> function in the ARM kernel helper page.
> 
> I see a __kuser_memory_barrier entry there which maps to smp_dmb.

That is indeed the correct way to do this - otherwise user programs will
be tied to particular architecture versions, and either an undefined
instruction fault will happen, or worse, the desired effect will not
happen.
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