Another problem related to indefinite postponement is called . This occurs when a waiting thread (letâ s call this thread1) cannot proceed because itâ s waiting (either directly or indirectly) for another thread (letâ s call this thread2) to proceed, while simultaneously thread2 cannot proceed because itâ s waiting (either directly or indirectly) for thread1 to proceed. The two threads are waiting for each other, so the actions that would enable each thread to continue execution can never occur.