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Subject: Re: FPU precision & signal handlers (bug?)
To: eries@there.com (Eric Ries)
Date: Mon, 4 Mar 2002 22:37:57 +0000 (GMT)
Cc: linux-kernel@vger.kernel.org
In-Reply-To: <200203041858.g24IwW115990@thdev4.there.com> from "Eric Ries" at Mar 04, 2002 10:58:32 AM
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From: Alan Cox <alan@lxorguk.ukuu.org.uk>
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> handlers. We use signals extensively in our program, and were quite
> surprised to find kernel FINIT traps being generated from them. After
> reading through the 2.4.2 source, I now believe that all signal
> handlers run with the default FPU control word in effect. Here's
> why...

Think about MMX and hopefully it makes sense then.

> strikes me as kind of a hack. Why should the signal handler, alone
> among all my functions (excepting main) be responsible for blowing
> away the control word?

Right - I would expect it to be restored at the end of the signal handler
for you - is that occuring or not ? I just want to make sure I understand
the precise details of the problem here.

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