B.12.4 $HIBER and $WAKE

$HIBER and $WAKE result in upcalls to DECthreads. When a user thread calls $HIBER, only that thread is blocked; all other threads continue running. The blocking thread is immediately unscheduled and another thread is scheduled to run instead. When a thread (or another process) calls $WAKE, all hibernating threads are awakened.

Prior to OpenVMS Version 7.0, a thread which called a $HIBER (or called a library routine which eventually resulted in a call to $HIBER) would cause the whole process to hibernate for a brief period whenever that thread was scheduled to "run". Also, with multiple threads in calls to $HIBER simultaneously, there was no reliable way to wake the threads (or a specific thread); the next hibernating thread to be scheduled would awaken, and any other threads would continue to sleep.

In OpenVMS Alpha Version 7.0, these problems are resolved. However, this new behavior has some other effects. For instance, hibernation- based services, such as LIB$WAIT and the C RTL sleep() routine, may be prone to premature completion. If the service does not validate its wakeup (that is, ensure that enough time has passed or that there is some other reason for it to return), then it will be prone to this problem, as are the above services, since they do not perform such wake-up validation.