lkml.org 
[lkml]   [2003]   [Mar]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [BK-2.5] Move "used FPU status" into new non-atomic thread_info->status field.
Linus Torvalds wrote:
> On Mon, 10 Mar 2003, David S. Miller wrote:
>
>>
>>At least on sparc{32,64}, we consider FPU state to be clobbered coming
>>into system calls, this eliminates a lot of hair wrt. FPU state
>>restoring in cases such as fork().
>>
>
> We could _probably_ do it on x86 too. The standard C calling convention on
> x86 says FPU register state is clobbered, if I remember correctly.
> However, some of the state is "long-term", like rounding modes, exception
> masking etc, and even if we didn't save the register state we would have
> to save that part.
>
> And once you save that part, you're better off saving the registers too,
> since it's all loaded and saved with the same fxsave/fxrestor instruction
> (ie we'd actually have to do _more_ work to save only part of the FP
> state).

Does this open the door for using FP in the kernel?

Chris


--
Chris Friesen | MailStop: 043/33/F10
Nortel Networks | work: (613) 765-0557
3500 Carling Avenue | fax: (613) 765-2986
Nepean, ON K2H 8E9 Canada | email: cfriesen@nortelnetworks.com

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2005-03-22 13:33    [W:0.031 / U:1.820 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site