From: Richard Henderson <rth@redhat.com>
To: Andi Kleen <ak@suse.de>
Cc: Linus Torvalds <torvalds@osdl.org>,
Chuck Ebbert <76306.1226@compuserve.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
Andrew Morton <akpm@osdl.org>, Ingo Molnar <mingo@elte.hu>
Subject: Re: [patch] i386: make bitops safe
Date: Mon, 27 Feb 2006 16:54:36 -0800 [thread overview]
Message-ID: <20060228005436.GA24895@redhat.com> (raw)
In-Reply-To: <200602280047.22909.ak@suse.de>
On Tue, Feb 28, 2006 at 12:47:22AM +0100, Andi Kleen wrote:
> I remember asking rth about this at some point and IIRC
> he expressed doubts if it would actually do what expected. Richard?
It's a bit dicey to be sure. GCC may or may not be able to look
through the size of the array and not kill things beyond it. If
one could be *sure* of some actual maximum index, this would be
fine, but I don't think you can.
One could reasonably argue that if you used a structure with a
flexible array member, that GCC could not look through that. But
again I'm not 100% positive this is handled properly.
I think the best argument for simply leaving things with a memory
clobber is that these are atomic operations, and are on occasion
used as locks, or parts of locks.
r~
next prev parent reply other threads:[~2006-02-28 0:54 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-02-27 21:57 [patch] i386: make bitops safe Chuck Ebbert
2006-02-27 23:06 ` Linus Torvalds
2006-02-27 23:47 ` Andi Kleen
2006-02-28 0:54 ` Richard Henderson [this message]
2006-02-28 1:24 ` Andi Kleen
-- strict thread matches above, loose matches on Subject: below --
2006-02-28 6:04 Chuck Ebbert
2006-02-28 21:25 ` Richard Henderson
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