[PATCH 0/4] convert perf to local64_t

[Peter Zijlstra <a.p.zijlstra@chello.nl>]

These patches introduce local64_t.

Since perf_event:count is only modified cross-cpu when child-counters
feed back their changes on exit, and we can use a secondary variable
for that, we can convert perf to use local64_t instead of atomic64_t
and use instructions without buslock semantics.

The local64_t implementation uses local_t for 64 bits, since local_t is
of type long, for 32 bit it falls back to atomic64_t. Architectures can
provide their own implementation as usual.