Re: Question: Using floating point in the kernel

[Andi Kleen]

On Thu, Sep 21, 2000 at 11:08:36PM +0100, Alan Cox wrote:
> > On Thu, Sep 21, 2000 at 11:36:17AM +0000, John Alvord wrote:
> > > A 2.5-time problem is that portions of the kernel are planned to
> > > become interruptible... so saving and restoring around a certain usage
> > > would be insufficient.
> > 
> > It is sufficient when you do tsk->flags |= PF_USEDFPU first.
> 
> Unless you sleep

Unless I'm missing something the lazy FPU state save in the 2.4 switch_to will
do the right thing at least on x86. Your kernel FPU state will overwrite the 
user FPU state in current, but that's ok because it is undefined anyways 
(and you restore the correct state when you wake up again) 


-Andi

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