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Date: Fri, 7 Feb 2003 10:46:21 -0800
From: Jun Sun <jsun@mvista.com>
To: Vivien Chappelier <vivienc@nerim.net>
Cc: Ralf Baechle <ralf@oss.sgi.com>, linux-mips@linux-mips.org,
	jsun@mvista.com
Subject: Re: [PATCH 2.5] clear USEDFPU in copy_thread
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In-Reply-To: <20030206164342.G13258@mvista.com>; from jsun@mvista.com on Thu, Feb 06, 2003 at 04:43:42PM -0800
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On Thu, Feb 06, 2003 at 04:43:42PM -0800, Jun Sun wrote:
> 
> You should *not* clear USEDFPU in copy_thread().  Imagine
> you assign a floating point variable f=0.3, then do fork()
> and then in the child process, alas, f is undefined (zero
> most likely).
> 
> If you really want to do it, it should be in start_thread().
>

This is plain stupid comment!  I was thinking about task->used_math
flag.  Please igore it.  
 
> I am still curious whether this is a bug in i386 as well or they do
> clear the flag in some non-obvious way.  Note that the unlazy_fpu()
> in copy_thread won't do it.  It only clears the current process's
> USEDFPU flag, while the child process's flag is set way back in
> copy_flags() calls inside do_fork().
>

But this comment still makes sense... 

Jun