[PATCH] Fix performance monitor exception in 2.6.20-series

[Benjamin Herrenschmidt]

>   IMHO, option  #1 is very  nice, as long  as the PMU interrupt  handler behaves
> itself.  One reason option #1 is desirable is, with PC-sampling, we are now able
> to  sample  regions _inside_  interrupt-disabled  sections  (assuming an  actual
> external interrupt  hasn't really occured yet). Before,  with hardware disabling
> of  interrupts,  the  PMU  exceptions  were  necessarily  delivered  outside  of
> interrupt disabled sections. 
> 
>   Anyways, does anyone see a problem with the following patch? 

Well, are you absolutely sure that nothing will break as a result of
having a PMU interrupt happening right when it's not expected to ?

You are basically turning the PMU interrupt into an NMI... I'm not sure
how safe that is.

Ben.