Fix small race in 44x tlbie function

[Volkmar Uhlig]

> -----Original Message-----
> From: galak at kernel.crashing.org [mailto:galak at kernel.crashing.org] 
> Sent: Wednesday, August 08, 2007 11:21 AM
> To: david at gibson.dropbear.id.au
> Cc: paulus at samba.org; linuxppc-dev at ozlabs.org; Todd Inglett; 
> Volkmar Uhlig
> Subject: Re: Fix small race in 44x tlbie function
> 
> 
> On Aug 6, 2007, at 11:20 PM, David Gibson wrote:
> 
> > The 440 family of processors don't have a tlbie instruction.  So, we
> > implement TLB invalidates by explicitly searching the TLB 
> with tlbsx.,
> > then clobbering the relevant entry, if any.  Unfortunately 
> the PID for
> > the search needs to be stored in the MMUCR register, which is also
> > used by the TLB miss handler.  Interrupts were enabled in 
> _tlbie(), so
> > an interrupt between loading the MMUCR and the tlbsx could cause
> > incorrect search results, and thus a failure to invalide TLB entries
> > which needed to be invalidated.
> >
> > This patch fixes the problem in both arch/ppc and arch/powerpc by
> > inhibiting interrupts (even critical and debug interrupts) 
> across the
> > relevant instructions.
> >
> > Signed-off-by: David Gibson <david at gibson.dropbear.id.au>
> > ---
> > Paul, this one's a bugfix, which I think should go into 2.6.23.
> 
> Did you actually see this happen?

Yes!  (I guess you didn't get the initial mail...)

- Volkmar