[PATCH] x86_64: Fix race in TSC synchronization

Plug a race in TSC synchronization

We need to do tsc_sync_wait() before the CPU is set online to prevent
multiple CPUs from doing it in parallel - which won't work because TSC
sync has global unprotected state.

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>