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From: Keith Owens <kaos@sgi.com>
To: Piet Delaney <piet@www.piet.net>
Cc: Christoph Hellwig <hch@sgi.com>, "Matt D. Robinson" <yakker@aparity.com>,
       linux-kernel@vger.kernel.org, steiner@sgi.com, jeremy@sgi.com
Subject: Re: [PATCH] 2.5.44: lkcd (9/9): dump driver and build files 
In-reply-to: Your message of "22 Oct 2002 15:21:02 MST."
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Date: Wed, 23 Oct 2002 08:56:18 +1000
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On 22 Oct 2002 15:21:02 -0700, 
Piet Delaney <piet@www.piet.net> wrote:
>Looks like your right, for parisc even these functions are using a
>spinlock. Is it really necessary for parisc to use spinlocks? Even
>Solaris doesn't use spinlocks for atomic set and reads of atomic
>variables.

Hardware restriction.  Somebody read that "all locks can be implemented
in terms of a single hardware primitive" and believed it :(.  The only
atomic operation on parisc is load and clear word.  According to the
comments in asm-parisc/atomic.h, atomic_set should not require a lock,
but it is coded to use one.  Atomic add/sub obviously needs a lock.

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