RTEMS 4.9.4 On-Line Library

Message Manager MESSAGE_QUEUE_URGENT - Put message at front of a queue

RTEMS C User's Guide

10.4.5: MESSAGE_QUEUE_URGENT - Put message at front of a queue

CALLING SEQUENCE:

rtems_status_code rtems_message_queue_urgent(
  rtems_id    id,
  const void *buffer,
  size_t      size
);

DIRECTIVE STATUS CODES:

RTEMS_SUCCESSFUL - message sent successfully
RTEMS_INVALID_ID - invalid queue id
RTEMS_INVALID_SIZE - invalid message size
RTEMS_INVALID_ADDRESS - buffer is NULL
RTEMS_UNSATISFIED - out of message buffers
RTEMS_TOO_MANY - queue's limit has been reached

DESCRIPTION:

This directive sends the message buffer of size bytes in length to the queue specified by id. If a task is waiting on the queue, then the message is copied to the task's buffer and the task is unblocked. If no tasks are waiting on the queue, then the message is copied to a message buffer which is obtained from this message queue's message buffer pool. The message buffer is then placed at the front of the queue.

NOTES:

The calling task will be preempted if it has preemption enabled and a higher priority task is unblocked as the result of this directive.

Sending a message to a global message queue which does not reside on the local node will generate a request telling the remote node to post the message on the specified message queue.

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

RTEMS C User's Guide