There are some methods missing METHOD_EXIT events when running
java -server -Xrunhprof:cpu=times on applications.

So hprof outputs a lot of:
HPROF ERROR: method on stack top != method exiting..

method_entry and method_exit are not paired up.
hprof received method_entry for one method but didn't receive
method_exit for it; instead it receives a method_exit event
for its caller.

See 4489387 and 4491764 to reproduce the problem.