[patch 0/4] CPU hot-plug support for x86_64

[Ashok Raj <ashok.raj@intel.com>]

Hi Andi

Attached are patches that would apply over 2.6.12-rc4-mm2 to provide
cpu hotplug support. It seems to hold up to stress (make -j's) on a 4way
HT system)

FYI: Iam sending this via quilt mail, hopefully it makes its way ok, 
otherwise please pardon, and i will resend my usuall way again if this 
doesn't work.

- I tested with booting maxcpus=1, then you can kick each cpu online.
  * I also manually migrate interrupts to the new CPU, and ensure they are off
    when that same cpu is being offlined.
  * Seems to have trouble with CONFIG_SCHED_SMT, i need to look into this
    later.
- Offline works as well

Andi: You had mentioned that you would not prefer to replace the broadcast IPI
      with the mask version for performance. Currently this seems to be the
	  most optimal way without putting a sledge hammer on the cpu_up process.

	  If there are any known performance issues that we are worried about
	  we should look for alternative mechanism. 

TBD: 
0. Verify with CONFIG_NUMA (not done yet)
1. ACPI integration for physical cpu hotplug support.
2. replace fixup_irqs() with a correct implementation. This works fine for now
   but has potential to miss interrupts. (in works).


Cheers,
Ashok Raj