linux-kernel - Re: [PATCH] AFS: Fix file locking

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Message-ID: <alpine.LFD.0.999.0707201835070.27249@woody.linux-foundation.org>
Date:	Fri, 20 Jul 2007 18:37:00 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Nick Piggin <nickpiggin@...oo.com.au>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	David Howells <dhowells@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] AFS: Fix file locking



On Fri, 20 Jul 2007, Nick Piggin wrote:
> 
> So you did. Then to answer that, yes it could be faster because there are
> stupid volatiles sprinkled all over the bitops code so you could easily
> end up having to do more loads. Does it make a real difference? Unlikely,
> but David loves counting cycles :)

I thought we long long since removed the volatiles. They are buggy and 
horrible, and we really want to let the compiler combine multiple 
test-bits, and if they matter that implies locking is buggy or something 
worse..

Ie we'd *want*

	if (test_bit(x, y) || test_bit(z,y))

to be rewritten by the compiler as testing bits x/z at the same time.

But now I'm too scared to look.

		Linus
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