ftrace introduces instability into kernel 2.6.27(-rc2,-rc3)

[Benjamin Herrenschmidt]

> 
> Ok, there are two cases where it's ok :
> 
> 1 - in stop_machine, considering we are not touching code executed in
> NMI handlers.
> 2 - when using my replace_instruction_safe() which uses a temporary
> breakpoint when doing the instruction replacement.
> 
> In those cases you could use text_poke_early().

Note that vmap/vunmap will be very slow.

Ben.