RTEMS 4.9.0 On-Line Library

Task Manager rel_wai - Release Wait of Other Task

RTEMS ITRON 3.0 API User's Guide

1.4.11: rel_wai - Release Wait of Other Task

CALLING SEQUENCE:

ER rel_wai(
  ID tskid
);

STATUS CODES:

E_OK - Normal Completion

E_ID - Invalid ID Number (tskid was invalid or could not be used)

E_NOEXS - Object does not exist (the task specified by tskid does not exist)

E_OACV - Object access violation (A tskid less than -4 was specified from a user task. This is implementation dependent.)

E_OBJ - Invalid object state (the target task is not in WAIT state (including when it is in DORMANT state or when the issuing task specifies itself))

EN_OBJNO - An object number which could not be accessed on the target node is specified.

EN_CTXID - Specified an object on another node when the system call was issued from a task in dispatch disabled state or from a task-independent portion

DESCRIPTION:

This system call forcibly releases WAIT state (not including SUSPEND state) of the task specified by tskid.

An E_RLWAI error is returned to the task whose WAIT state has been released using rel_wai.

Wait release requests by rel_wai are not queued. In other words, if the task specified by tskid is already in WAIT state, the WAIT state is released, otherwise an E_OBJ error will be returned to the issuer. An E_OBJ error will also result when a task specifies itself to this system call.

Rel_wai does not release SUSPEND state. If rel_wai is issued on a task in WAIT-SUSPEND state, WAIT will be released but SUSPEND will continue for that task. When SUSPEND should also be released, the frsm_tsk system call must be issued separately.

NOTES:

A function similar to timeout can be implemented using an alarm handler which issues this system call on tasks specified time after they have entered WAIT state.

Rel_wai and wup_tsk differ in the following points.

Wup_tsk can only release the WAIT state by slp_tsk or tslp_tsk, while rel_wai can release WAIT states caused by these and other calls (including wai_flg, wai_sem, rcv_msg, get_blk, etc.).
As seen from the target task, releasing WAIT state with wup_tsk results in a normal completion (E_OK), whereas releasing WAIT state with rel_wai results in an error (E_RLWAI).
When wup_tsk is used, a request is queued even if neither slp_tsk nor tslp_tsk have been executed on the target task yet. When rel_wai is used to the task which is not in WAIT state, an E_OBJ error will result.

RTEMS ITRON 3.0 API User's Guide