The reporter was using 1.7.0_17 which is known to have deadlock issues in LogManager. Some more info from the JDK team:
"There have been actually two deadlocks
reported with findLogger / drainLoggerRefQueueBounded.
which I think is what you are observing, and that one is
marked fixed in 7u25 b11.
Later and more recently another deadlock was reported
but with a slightly different trace. I never managed to
reproduced it - but saw its theoretical possibility in
7 and 8.
This is https://bugs.openjdk.java.net/browse/JDK-8027670
which as been fixed by https://bugs.openjdk.java.net/browse/JDK-8029281
but in JDK 8 b120 only (not in JDK 7).
By looking at your stack trace and the fix made for
the code that is currently in 7 - I think the issue
you are observing is the one that has been fixed in 7u25. "