Methods of a class that use this annotation are treated specially by the compilers: (1) the normal thread switch test that would be emitted in the method prologue is omitted. (2) the stack overflow test that would be emitted in the method prologue is omitted.

Uninterruptible and Unpreemptible have the same direct effect on the generated code. The difference is that Uninterruptible indicates a stronger invariant: It is a programming error (and will be reported as such) for Uninterruptible code to contain any bytecodes that could cause a loss of control. Furthermore, Uninterruptible code will be generated assuming no RuntimeExceptions are raised and without any GC maps (since by definition there can be noGC if control is not lost). Unpreemtible code will have GC maps for all potential GC points and may contain places where a thread explicitly yields.