On Fri, Feb 15, 2002 at 10:59:09AM +0100, Kevin D. Kissell wrote: > > > > > 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??? ;-) > You must be talking about another OS, right? :-) I don't think Linux has processor-specific page, although this sounds like a good idea to explore. Jun
