mxUnlock (Function)

The mxUnlock() function will unlock a MUTEX variable previously locked by the mxLock() function.

A mutex can only be unlocked by the owner of the mutex.

The mutex mechanism is traditionally used for implementing critical sections. Also see the section on thread syncronization for more information.

Input:

mx : MUTEX

The MUTEX to unlock.                

Returns: INT

Declaration:

FUNCTION mxUnlock : INT;
VAR_INPUT
   mx : MUTEX;
END_VAR;

Example:

INCLUDE rtcu.inc
 
VAR
   mxCnt : MUTEX;
   Count : DINT := 0;
END_VAR;
 
THREAD_BLOCK Thread_A;
WHILE TRUE DO
   mxLock(mx:=mxCnt);
   Count := Count + 1;
   mxUnlock(mx:=mxCnt);
END_WHILE;
END_THREAD_BLOCK;
 
THREAD_BLOCK Thread_B;
WHILE TRUE DO
   mxLock(mx:=mxCnt);
   Count := Count + 5;
   mxUnlock(mx:=mxCnt);
END_WHILE;
END_THREAD_BLOCK;
 
PROGRAM test;
VAR
   TA    : Thread_A;
   TB    : Thread_B;
   i     : INT;
END_VAR;
 
mxCnt := mxInit();
 
TA();
TB();
 
BEGIN
   Sleep(delay:=1000);
   DebugFmt(message:="Count: \4",v4:=Count);
END;
 
END_PROGRAM;