linux-kernel - Re: [RFC patch 23/27] Immediate Values - Powerpc Optimization NMI MCE support

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Message-ID: <20080416233331.GA9225@Krystal>
Date:	Wed, 16 Apr 2008 19:33:31 -0400
From:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
To:	Paul Mackerras <paulus@...ba.org>
Cc:	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	Rusty Russell <rusty@...tcorp.com.au>,
	Christoph Hellwig <hch@...radead.org>
Subject: Re: [RFC patch 23/27] Immediate Values - Powerpc Optimization NMI
	MCE support

* Paul Mackerras (paulus@...ba.org) wrote:
> Mathieu Desnoyers writes:
> 
> > Use an atomic update for immediate values.
> 
> What is meant by an "atomic" update in this context?  AFAICS you are
> using memcpy, which is not in any way guaranteed to be atomic.
> 
> Paul.

I expect memcpy to perform the copy in one memory access, given I put a 

  .align 2

before the 2 bytes instruction. It makes sure the instruction modified
fits in a single, aligned, memory write.

Or maybe am I expecting too much from memcpy ?

Mathieu

-- 
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
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