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Date: Wed, 20 Feb 2002 14:24:16 +0100
From: Ralf Baechle <ralf@oss.sgi.com>
To: Daniel Jacobowitz <dan@debian.org>
Cc: Jun Sun <jsun@mvista.com>, Greg Lindahl <lindahl@conservativecomputer.com>,
   linux-mips@oss.sgi.com
Subject: Re: FPU emulator unsafe for SMP?
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In-Reply-To: <20020219233222.A22099@nevyn.them.org>; from dan@debian.org on Tue, Feb 19, 2002 at 11:32:22PM -0500
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On Tue, Feb 19, 2002 at 11:32:22PM -0500, Daniel Jacobowitz wrote:

> > If you do use floating point, I think it is pretty common to have
> > only process that uses fpu and runs for very long.  In that case,
> > leaving FPU owned by the process also saves quite a bit.
> 
> Not true.  For instance, on a processor with hardware FPU, setjmp()
> will save FPU registers.  That means most processes will actually end
> up taking the FPU at least once.

The cleassic reason to take the FPU is the ctc1 $0, $31 instruction used
to initalize the FPU control register rsp. it's equivalent on other
architectures.  This should be fixed in glibc since a few years.

   Ralf