If the native routine blocks the kernel thread, it blocks, and if not, it doesn't. While something could hypothetically be done about blocking native routines,

If the native routine blocks the kernel thread, it blocks, and if not, it doesn't. While something could hypothetically be done about blocking native routines, we don't see it as an important use case. Calling blocking native code from Java is quite uncommon. We've so far identified only one common case, DNS lookup, and will address it specifically.