Crash when using java debugger and kafka

[Christopher Ng]

Using Shenandoah, the test case at this link:
https://github.com/facboy/shenandoah-bug will hang consuming all cores, and
becoming non-responsive to eg interrupts signals, etc.  the same does not
happen if G1 is used.

I first came across this when debugging from an IDE (Intellij IDEA).  I
haven't  really been able to work out why this is happening.  The JDK
version is

openjdk version "1.8.0_222"
OpenJDK Runtime Environment (build 1.8.0_222-b10)
OpenJDK 64-Bit Server VM (build 25.222-b10, mixed mode)

running on CentOS Linux release 7.6.1810 (Core).

I suspect a race condition as turning up the logging (eg to info on Kafka)
seems to stop the bug happening.  For the test case it seems that having
the JVM listen (as opposed to connect to a running debugger) seems to also
stop the bug, though in the main codebase where I first encountered this
bug, this did not make a difference (ie the bug still occurred).  i also
found that running strace (when trying to diagnose the issue with the main
codebase) also stopped the bug happening.