Outline

Change task priority.

C format

 ER      chg_pri (ID tskid, PRI tskpri);

 ER      ichg_pri (ID tskid, PRI tskpri);

Parameter(s)

I/O	Parameter	Description
I	ID tskid;	ID number of the task whose priority is to be changed. TSK_SELF: Invoking task. Value: ID number of the task whose priority is to be changed.
I	PRI tskpri;	New base priority of the task. TPRI_INI: Initial priority. Value: New base priority.

Explanation

These service calls change the priority of the task specified by parameter tskid (current priority) to a value specified by parameter tskpri.

If the target task is in the RUNNING or READY state after this service call is issued, this service call re-queues the task at the end of the ready queue corresponding to the priority specified by parameter tskpri, following priority change processing.

Note When the target task is queued to a wait queue in the order of priority, the wait order may change due to issue of this service call.

Example When three tasks (task A: priority level 10, task B: priority level 11, task C: priority level 12) are queued to the semaphore wait queue in the order of priority, and the priority level of task B is changed from 11 to 9, the wait order will be changed as follows.

Return value

Macro	Value	Description
E_OK	0	Normal completion.
E_PAR	-17	Parameter error. - tskpri < 0x0 - tskpri > Maximum priority
E_ID	-18	Invalid ID number. - tskid < 0x0 - tskid > Maximum ID number - When this service call was issued from a non-task, TSK_SELF was specified tskid.
E_CTX	-25	Context error. - This service call was issued int the CPU locked state.
E_OBJ	-41	Object state error. - Specified task is in the DORMANT state.
E_NOEXS	-42	Non-existent object. - Specified task is not registered.