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Re: preempt safe fpu-emulator

To: Ralf Baechle <ralf@linux-mips.org>
Subject: Re: preempt safe fpu-emulator
From: "Maciej W. Rozycki" <macro@linux-mips.org>
Date: Thu, 28 Apr 2005 16:25:30 +0100 (BST)
Cc: "Kevin D. Kissell" <KevinK@mips.com>, Atsushi Nemoto <anemo@mba.ocn.ne.jp>, linux-mips@linux-mips.org
In-reply-to: <20050428152123.GH1276@linux-mips.org>
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <20050427.143622.77402407.nemoto@toshiba-tops.co.jp> <20050428134118.GC1276@linux-mips.org> <002d01c54bfa$5b913f80$0deca8c0@Ulysses> <20050428152123.GH1276@linux-mips.org>
Sender: linux-mips-bounce@linux-mips.org
On Thu, 28 Apr 2005, Ralf Baechle wrote:

> > When I first integrated the Algorithmics emulator with the Linux kernel
> > several years back, I tried doing something like this but ran into some
> > problem that I cannot recall exactly - there may have been some case
> > where the system expected threads to "inherit" FCSR changes.  I agree
> > that this is an obviously cleaner approach, but be careful.
> 
> The global variables definately won't fly anymore in preemptable and SMP
> kernels.  Or rather any attempt to get that to work would only make things
> worse, so they had to go.

 It depends on how they were actually used -- real FPU circuitry is 
"global", too, and somehow it works or at least it has to.

  Maciej

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