RTEMS 4.9.3 On-Line Library

Semaphore Manager SEMAPHORE_RELEASE - Release a semaphore

RTEMS Ada User's Guide

9.4.5: SEMAPHORE_RELEASE - Release a semaphore

CALLING SEQUENCE:

procedure Semaphore_Release (
   ID     : in     RTEMS.ID;
   Result :    out RTEMS.Status_Codes
);

DIRECTIVE STATUS CODES:

RTEMS.SUCCESSFUL - semaphore released successfully
RTEMS.INVALID_ID - invalid semaphore id
RTEMS.NOT_OWNER_OF_RESOURCE - calling task does not own semaphore

DESCRIPTION:

This directive releases the semaphore specified by id. The semaphore count is incremented by one. If the count is zero or negative, then the first task on this semaphore's wait queue is removed and unblocked. The unblocked task may preempt the running task if the running task's preemption mode is enabled and the unblocked task has a higher priority than the running task.

NOTES:

The calling task may be preempted if it causes a higher priority task to be made ready for execution.

Releasing a global semaphore which does not reside on the local node will generate a request telling the remote node to release the semaphore.

If the task to be unblocked resides on a different node from the semaphore, then the semaphore allocation is forwarded to the appropriate node, the waiting task is unblocked, and the proxy used to represent the task is reclaimed.

The outermost release of a local, binary, priority inheritance or priority ceiling semaphore may result in the calling task having its priority lowered. This will occur if the calling task holds no other binary semaphores and it has inherited a higher priority.

RTEMS Ada User's Guide