> > > > I have been chasing a FPU register corruption problem on a SMP box. The
> > > > curruption seems to be caused by FPU emulator code. Is that code SMP safe?
> > > > If not, what are the volunerable spots?
> > >
> > > In theory the fp emulation code should be MP safe as the full emulation
> > > is only accessing it's context in the fp register set of struct
> > > task_struct. The 32-bit kernel's fp register switching is entirely broken
> > > (read: close to non-existant). Lots of brownie points for somebody to
> > > backport that from the 64-bit kernel to the 32-bit kernel and forward
> > > port all the FPU emu bits to the 64-bit kernel ...
> > >
> >
> > Brownie sounds good. :-) So what is the "fp register switching" you are
> > referring to? There is set of code related to lazy fpu context switch,
> > which seems to be working fine now.
> >
>
> Hmm, I see. The lazy fpu context switch code is not SMP safe.
> I see fishy things like "last_task_used_math" etc...
What, you mean "last_task_used_math" isn't allocated in a
processor-specific page of kseg3??? ;-)
Kevin K.
