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Subject: Re: [RFC] New locking primitive for 2.5
To: mfedyk@matchmail.com (Mike Fedyk)
Date: Sat, 9 Feb 2002 00:09:04 +0000 (GMT)
Cc: linux-kernel@vger.kernel.org (linux-kernel)
In-Reply-To: <20020208211628.GC343@mis-mike-wstn> from "Mike Fedyk" at Feb 08, 2002 01:16:28 PM
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From: Alan Cox <alan@lxorguk.ukuu.org.uk>
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> SMP 486s would need that (if there is such a beast).  What point does x86
> get the 64 bit instructions?  If after 586, then it would definately need a
> spinlock or somesuch in those functions.

There are SMP 486 class x86 machines that are MP 1.1 compliant. They are
sufficiently rare that I think its quite acceptable to "implement" a
cmpxchg8b macro on 486 as spin_lock_irqsave/blah/spin_unlock_irqrestore. It
would be wrong to cripple the other 99.99% of SMP users
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