spurious wakeups

     An added benefit of allowing spurious wakeups is that applications are forced to code a predicate-testing-loop  around   the  condition  wait. This also makes the application tolerate superfluous condition broadcasts or signals on the same
       condition variable that may be coded in some other part of the application. The resulting applications are  thus  more  robust. Therefore, IEEE Std 1003.1-2001 explicitly documents that spurious wakeups may occur.