From: Andi Kleen <ak@suse.de>
To: Linus Torvalds <torvalds@osdl.org>, rth@redhat.com
Cc: 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: Tue, 28 Feb 2006 00:47:22 +0100 [thread overview]
Message-ID: <200602280047.22909.ak@suse.de> (raw)
In-Reply-To: <Pine.LNX.4.64.0602271502410.22647@g5.osdl.org>
On Tuesday 28 February 2006 00:06, Linus Torvalds wrote:
> On Mon, 27 Feb 2006, Chuck Ebbert wrote:
> > Make i386 bitops safe. Currently they can be fooled, even on
> > uniprocessor, by code that uses regions of the bitmap before
> > invoking the bitop. The least costly way to make them safe
> > is to add a memory clobber and tag all of them as volatile.
>
> Actually, the least costly way should be to make the "ADDR" define work
> right again.
>
> It used to do something magic like
I remember asking rth about this at some point and IIRC
he expressed doubts if it would actually do what expected. Richard?
-Andi
>
> struct fake_area {
> unsigned long members[1000];
> };
>
> #define ADDR (*(volatile struct fake_area *)addr)
>
> which was correct. I forget why it got broken into using just a "long *"
> (it happened a long long time ago).
>
> Linus
next prev parent reply other threads:[~2006-02-27 23:45 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 [this message]
2006-02-28 0:54 ` Richard Henderson
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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