Possibly related to nio4r? This is using nio4r 0.4.2 which includes the selector close synchronization fix.
Stack trace here:
Originally experienced it on Travis:
It's definitely in nio4r. When I uncomment the code that cleans up stuff in NIO_Selector_shutdown it doesn't crash anymore. It of course leaks stuff then, so we don't want that :).
Let me try synchronizing the selector cleanup and see if that fixes the problem.
I was trying to locate the JVM's version of this same code for comparison but could not :|