From: Andi Kleen <ak@suse.de>
To: "David S. Miller" <davem@davemloft.net>
Cc: linux-arch@vger.kernel.org
Subject: Re: Kill HAVE_DEC_LOCK
Date: Tue, 13 Sep 2005 08:51:16 +0200 [thread overview]
Message-ID: <200509130851.16806.ak@suse.de> (raw)
In-Reply-To: <20050912.234700.88643507.davem@davemloft.net>
On Tuesday 13 September 2005 08:47, David S. Miller wrote:
> From: Andi Kleen <ak@suse.de>
> Date: Tue, 13 Sep 2005 08:15:50 +0200
>
> > Looks good. Unfortunately XADD cannot be used for that.
>
> If that were possible, what would be the advantage
> compared to cmpxchg{b,w,l}?
(lock xadd = essentially atomic add and return result)
It would tell the microcode exactly what we want to do so it
might optimize better. I don't know if it actually works better
on current micro architectures, but it might.
The problem is that it cannot do the spinlock atomically,
so we have to use cmpxchg anyways.
-Andi
prev parent reply other threads:[~2005-09-13 6:51 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-09-12 23:05 Kill HAVE_DEC_LOCK David S. Miller
2005-09-13 6:15 ` Andi Kleen
2005-09-13 6:47 ` David S. Miller
2005-09-13 6:51 ` Andi Kleen [this message]
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