RFR: 8225351(13): assert failed: Revoke failed, unhandled biased lock state

[Robbin Ehn]

Hi all, please review.

When looking at a JavaThreads locks we retrieve them per frame via it's monitors
list. How this list actually populated differs from frame type. If a JavaThread 
tries to enter a new monitor a basic lock is directly/indirectly via e.g. scope 
info added to the virtual monitor list. If this lock is biased towards another
JavaThread we try to revoke that bias with a safepoint. In this case a deopt
handshake is already in queue. The handshake is thus executed before the revoke
safepoint.
The handshake goes over the monitors in compiled frames, find this lock and we
hit the assert. The assert make sure we actual can revoke the lock. A basic lock
on stack should always, if biased, be biased to current thread, with the
exception:
We may have a stack lock biased against another thread until
ObjectSynchronizer::fast_enter returns.

To handle this exception we can safely ignore biased lock towards other threads
in the deopt handshake. Since such locks will always be revoked before we
deopt/unpack stack.

Code:
http://cr.openjdk.java.net/~rehn/8225351/v1/webrev/index.html
Issue:
https://bugs.openjdk.java.net/browse/JDK-8225351

Passes t1-7
The assert code tested with local code changes to HandshakeAlot handshake.
We then see this state where last lock can be biased towards another thread and 
the thread is trying to execute revoke safepoint.

Thanks, Robbin