RFR: 8220724: TestBiasedLockRevocationEvents fails while matching revoke events to VMOperation events

[Patricio Chilano]

Hi,

Could you review this small patch?

https://bugs.openjdk.java.net/browse/JDK-8220724
http://cr.openjdk.java.net/~pchilanomate/8220724/v01/webrev/

The subtest testRevocationSafepointIdCorrelation() in 
TestBiasedLockRevocationEvents.java fails intermittently because there 
could be a mismatch between the safepoint id recorded by the VMThread 
during the execution of a VM_RevokeBias or VM_BulkRevokeBias operation, 
and the one recorded by the JavaThread that requested the VM operation. 
I added a more detailed description of the problem in the comments of 
the bug.

Testing tiers1-3 in mach5 and test TestBiasedLockRevocationEvents.java 
with flag -XX:+SafepointALot.

Thanks!
Patricio