From owner-freebsd-current  Tue Jan 16 13: 0:48 2001
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Date: Tue, 16 Jan 2001 12:08:03 -0800
From: Julian Elischer <julian@elischer.org>
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To: Bruce Evans <bde@zeta.org.au>
Cc: John Baldwin <jhb@FreeBSD.ORG>,
	Peter Jeremy <peter.jeremy@alcatel.com.au>, current@FreeBSD.ORG,
	Mark Murray <mark@grondar.za>
Subject: Re: Atomic breakage?
References: <Pine.BSF.4.21.0101162335080.2035-100000@besplex.bde.org>
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Bruce Evans wrote:
> 
> On Mon, 15 Jan 2001, John Baldwin wrote:
> 
> > On 14-Jan-01 Peter Jeremy wrote:
> > > And for BDE's benefit - atomic.h is broken for IA32's with 64-bit
> > > longs.  (I believe that can be fixed for Pentiums and above using
> > > CMPXCHG8B, but I can't test the code).
> >
> > The i386 with 64-bit longs doesn't boot from what I hear.  Also, long in
> > machine/types.h is 32-bits long.  I don't think we need to bother with 64-bit
> > longs.  Adding 64-bit atomic ops will be expensive on <= 486.
> 
> It has booted fine for several years.  I last built it on 8 Oct 2000.  I
> haven't committed all the bits so it probably doesn't even build in -current.
> 
> Erm, long isn't in machine/types.h.  In <machine>, only the long limits in
> <machine/limits.h> and a few bogus typedefs depend on the size of a long.
> 
> I bother with 64-bit longs whether I need to or not :-).  They get used on
> i386's mainly in old code and interfaces that don't use typedefs.
> Hopefully 64-bit scalars will never need to be accessed atomically.

Too late.

Many statistics in interfaces (i.e. bytes transmitted) are already 64 bit
words.

> 
> Bruce
> 
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-- 
      __--_|\  Julian Elischer
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