HW-BKPT: Introduce new features to the hw-breakpoint infrastructure

Hi All,
Please find a set of patches that implement the features listed
below. This is a sequel to the patchset posted yesterday
http://lkml.org/lkml/2009/8/25/371 and contains a new patch 3/3.

Patch 1/2: Allow per-cpu kernel-space Hardware Breakpoint requests Patch 2/2: Allow kernel breakpoints to be modified through a new API Patch 3/3: Allow breakpoints to be enabled/disabled without yielding the breakpoint request through a new API - enable_hw_breakpoint().

During discussion on LKML, these features were deemed necessary for effective exploitation of hardware breakpoints by perf-tools.

The patches are based off -tip tree. Kindly let me know your comments on the same.

Thanks,
K.Prasad