{14] RFR(M): 8233111: Epoch shift synchronization point for Compiler threads

[Markus Gronlund]

Greetings,

Please review the following changeset addressing a race in the area of Klass / Method tagging during a safepoint, between Compiler threads and the JFR epoch shift. 

Bug: https://bugs.openjdk.java.net/browse/JDK-8233111
Webrev: http://cr.openjdk.java.net/~mgronlun/8233111/webrev01/ 
Testing: jdk_jfr

Thanks
Markus