Program hangs if thread is created in static initializer block

Question

I have come across a situation where my program hangs, looks like deadlock. But I tried figuring it out with jconsole and visualvm, but they didn\'t detect any deadlock. Sam

Answer 1

classloading is kind of a sensitive time in the jvm. when classes are being initialized, they hold an internal jvm lock which will pause any other thread trying to work with the same class. so, your spawned thread is most likely waiting for the StaticInitializer class to be fully initialized before proceeding. however, your StaticInitializer class is waiting for the thread to complete before being fully initialized. thus, deadlock.

of course, if you are truly trying to do something like this, the secondary thread is superfluous since you are joining it right after you start it (so you might as well just execute that code directly).

UPDATE:

my guess as to why the deadlock is not detected is because it is occurring at a much lower level than the level at which the standard deadlock detection code works. that code works with normal object locking, whereas this is deep jvm internal stuff.