Date: Wed, 11 Apr 2001 17:00:45 +0200 (MEST)
From: Andreas Franck <afranck@gmx.de>
To: David Howells <dhowells@cambridge.redhat.com>
Cc: dhowells@cambridge.redhat.com, torvalds@transmeta.com, andrewm@uow.edu.au,
        bcrl@redhat.com, alan@lxorguk.ukuu.org.uk,
        linux-kernel@vger.kernel.org
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In-Reply-To: <16847.987000228@warthog.cambridge.redhat.com>
Subject: Re: [PATCH] 2nd try: i386 rw_semaphores fix
Message-ID: <24940.987001245@www17.gmx.net>
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Hello David,

> I've been discussing it with some other kernel and GCC people, and they
> think
> that only "memory" is required.

Hmm.. I just looked at my GCC problem report from December, perhaps you're
interested, too:

http://gcc.gnu.org/ml/gcc-bugs/2000-12/msg00554.html

The example in there compiles out-of-the box and is much easier to
experiment on than the whole kernel :-)

It should reflect the situation in the kernel as of December 2000, where no
outputs were declared at all.

I can try this examples again with current GCC snapshots and will see if I
can find a working solution without reserving more registers.

> Apart from the risk of breaking it, you mean? Well, "=m" seems to reserve
> an
> extra register to hold a second copy of the semaphore address, probably
> since
> it thinks EAX might get clobbered.
> 
> Also, as a minor point, it probably ought to be "+m" not "=m".

Perhaps, I'm no real expert on this things, and "=m" worked for me, so
I used it :)

Greetings,
Andreas

-- 
GMX - Die Kommunikationsplattform im Internet.
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