7011859: java/util/concurrent/Semaphore/RacingReleases.java failing

[Alan Bateman]

This test has been failing (very intermittently) for some time. It was 
assumed to be a HotSpot issue on SPARC but more recently it has been 
duplicated on Linux x64 too. David Simms has notes in the bug [1] from 
this instrumentation and analysis, and Doug has pushed a fix to his CVS 
that fixes the issue (although they may still be an underlying issue 
that still needs to be hunted down).

Doug's fix updates AQS and AQLS to re-read the head and avoid the race. 
We need to bring this into jdk8/tl, the webrev with the patch is here:

http://cr.openjdk.java.net/~alanb/7011859/webrev/

-Alan

[1] https://bugs.openjdk.java.net/browse/JDK-7011859