Re: context switch vs. signal delivery [was: Re: Accelerating user mode linux]

[Andi Kleen]

On Mon, Aug 05, 2002 at 11:09:41PM +0100, Jamie Lokier wrote:
> Andi Kleen wrote:
> > > 2: What happens when the user's signal handler decides it wants to save
> > > the FPU state itself (after all) and proceed with some FPU use.  Will
> > > sigreturn restore the user-saved FPU state?  Just curious.
> > 
> > Nope it won't because there is no saved state. The previous context's FPU 
> > state will be silently corrupted.
> 
> I meant if the user's signal handler decides it wants to save the FPU
> state directly into the signal context struct, after deciding to do
> that.  Won't that work?

In theory yes. The space should be already allocated on the stack, it just
has to be filled in.

-Andi