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Date:	Fri, 17 Aug 2007 11:53:42 +0800
From:	Herbert Xu <>
To:	Paul Mackerras <>
Cc:	Linus Torvalds <>,
	Christoph Lameter <>,
	Chris Snook <>,
	Ilpo J?rvinen <>,
	Satyam Sharma <>,
	"Paul E. McKenney" <>,
	Stefan Richter <>,
	Linux Kernel Mailing List <>,, Netdev <>,
	Andrew Morton <>,,, David Miller <>,,,,,,,,,
Subject: Re: [PATCH 0/24] make atomic_read() behave consistently across all architectures

On Fri, Aug 17, 2007 at 01:43:27PM +1000, Paul Mackerras wrote:
> The cost of doing so seems to me to be well down in the noise - 44
> bytes of extra kernel text on a ppc64 G5 config, and I don't believe
> the extra few cycles for the occasional extra load would be measurable
> (they should all hit in the L1 dcache).  I don't mind if x86[-64] have
> atomic_read/set be nonvolatile and find all the missing barriers, but
> for now on powerpc, I think that not having to find those missing
> barriers is worth the 0.00076% increase in kernel text size.

BTW, the sort of missing barriers that triggered this thread
aren't that subtle.  It'll result in a simple lock-up if the
loop condition holds upon entry.  At which point it's fairly
straightforward to find the culprit.

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Email: Herbert Xu ~{PmV>HI~} <>
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