Heads up: cpumask changes

[Rusty Russell <rusty@rustcorp.com.au>]

Hi all,

   With large NR_CPUS coming, Mike and I have been working to make dynamic 
cpumasks an option.  The main change is to APIs which pass cpumask_t around; 
they'll now be '[const] struct cpumask *'.  This unfortunately will hit arch 
code as interfaces get frobbed, and a couple of nasty one-shot transitions are 
unavoidable.

   For archs which never intend to support CONFIG_CPUMASK_OFFSTACK, the rest 
of the changes will be cosmetic (eg. s/cpumask_t/struct cpumask/ eventually).  
For x86 and others who allow CONFIG_CPUMASK_OFFSTACK, "struct cpumask" will 
eventually be undefined so it cannot be assigned or used on the stack: this 
means use cpumask_copy(), cpumask_var_t and as a last resort, 
DEFINE_BITMAP(bitmap, NR_CPUS) and to_cpumask(bitmap).

   We've been working most closely with Ingo, as x86, irq and scheduler are 
most effected.  Apologies in advance for the churn, but the final result will 
be a neater API than what we have now as well as stupid numbers of cpus in 
your .config.

Thanks!
Rusty.