From: Linus Torvalds <torvalds@linux-foundation.org>
To: Nick Piggin <nickpiggin@yahoo.com.au>
Cc: Andrew Morton <akpm@linux-foundation.org>,
David Howells <dhowells@redhat.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] AFS: Fix file locking
Date: Fri, 20 Jul 2007 18:37:00 -0700 (PDT) [thread overview]
Message-ID: <alpine.LFD.0.999.0707201835070.27249@woody.linux-foundation.org> (raw)
In-Reply-To: <46A04129.1020900@yahoo.com.au>
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
next prev parent reply other threads:[~2007-07-21 1:37 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-07-17 12:47 David Howells
2007-07-18 0:50 ` Andrew Morton
2007-07-18 5:56 ` Nick Piggin
2007-07-20 3:41 ` Andrew Morton
2007-07-20 4:59 ` Nick Piggin
2007-07-21 1:37 ` Linus Torvalds [this message]
2007-07-23 7:07 ` Nick Piggin
2007-07-23 8:50 ` Satyam Sharma
2007-07-23 9:13 ` Satyam Sharma
2007-07-23 9:13 ` David Howells
2007-07-18 9:23 ` David Howells
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