[PATCH 0 of 4] Xen spinlock updates and performance measurements

Hi Ingo,

This series has some updates to Xen's spinlock implementation,
including adding a set of performance measurements in debugfs.

The series consists of:
 - correctly deal with a spinlock in an interrupt handler interrupting
   another spinlock spinning on a lock. [2.6.27 bugfix]
 - Add Xen debugfs support, including performance metrics for
   spinlocks, multicalls and mmu operations.
 - Allow interrupts to be enabled while spinning (blocking) for a lock
 - Measure time spinlocks spend blocked

Thanks,
	J