review (S) for 6956931: assert(SafepointSynchronize::is_at_safepoint()) failed: must be executed at a safepoint

[Tom Rodriguez]

http://cr.openjdk.java.net/~never/6956931

6956931: assert(SafepointSynchronize::is_at_safepoint()) failed: must be executed at a safepoint
Reviewed-by:

SSince the sweeper no longer runs at a safepoint the compiled method
unload logic doesn't always run at a safepoint so we need a new
synchronous notification path that's equivalent to the
compiled_method_load logic.  I refactored the code a bit to share the
core notification logic and I refactored the notification in nmethod
to remove duplication.  Tested with NSK jvmti,jdb,jdi,hprof suites.