The rtems_event_send directive allows a task (or an ISR) to
direct an event set to a target task. Based upon the state of
the target task, one of the following situations applies:
Target Task is Blocked Waiting for Events
If the waiting task's input event condition is
satisfied, then the task is made ready for execution.
If the waiting task's input event condition is not
satisfied, then the event set is posted but left pending and the
task remains blocked.
RTEMS C User's Guide