Outline

Lock mutex (waiting forever).

C format

 ER      loc_mtx (ID mtxid);

Parameter(s)

I/O	Parameter	Description
I	ID mtxid;	ID number of the mutex.

Explanation

This service call locks the mutex specified by parameter mtxid.

If the target mutex could not be locked (another task has been locked) when this service call is issued, this service call queues the invoking task to the target mutex wait queue and moves it from the RUNNING state to the WAITING state (mutex wait state).

The WAITING state for a mutex is cancelled in the following cases.

WAITING State for a Mutex Cancel Operation	Return Value
The locked state of the target mutex was cancelled as a result of issuing unl_mtx.	E_OK
The locked state of the target mutex was cancelled as a result of issuing ext_tsk.	E_OK
The locked state of the target mutex was cancelled as a result of issuing exd_tsk.	E_OK
The locked state of the target mutex was cancelled as a result of issuing ter_tsk.	E_OK
Forced release from waiting (accept rel_wai while waiting).	E_RLWAI
Forced release from waiting (accept irel_wai while waiting).	E_RLWAI
Forced release from waiting (accept del_mtx while waiting).	E_DLT

When the mutex is locked, this service call changes the current priority of the invoking task to the ceiling priority of the target mutex. However, this service call does not change the current priority when the invoking task has locked other mutexes and the ceiling priority of the target mutex is lower than or equal to the ceiling priority of the locked mutexes.

Note 1 Invoking tasks are queued to the target mutex wait queue in task current priority order. Among tasks with the same priority, they are queued in FIFO order.

Note 2 This service call returns "E_ILUSE" if this service call is re-issued for the mutex that has been locked by the invoking task (multiple-locking of mutex).

Return value

Macro	Value	Description
E_OK	0	Normal completion.
E_ID	-18	InvalidID number. - mtxid < 0 - mtxid > VTMAX_MTX
E_CTX	-25	Context error. - This service call was issued from a non-task. - This service call was issued in the CPU locked state. - This service call was issued in the dispatching disabled state. - This service call was issued in the status "PSW.IPL > kernel interrupt mask level".
E_MACV	-26	Memory access violation. - Stack pointer points out of user stack for invoking task.
E_ILUSE	-28	Illegal use of service call. - The invoking task has already locked the target mutex. - Ceiling priority violation (the base priority of the invoking task < the ceiling priority of the target mutex)
E_NOEXS	-42	Non-existent object. - The mutex specified by mtxid does not exist.
E_RLWAI	-49	Forced release from the WAITING state. - Accept rel_wai/irel_wai while waiting.
E_DLT	-51	Waiting object deleted. - Accept del_mtx while waiting.