en:software:qview:qview_6:qcl_library:sy10entercriticalsection

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en:software:qview:qview_6:qcl_library:sy10entercriticalsection [2017/04/04 17:27] – created qem103en:software:qview:qview_6:qcl_library:sy10entercriticalsection [2019/08/29 17:01] (current) – external edit 127.0.0.1
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 +====== SY10EnterCriticalSection ======
 +
 +**SY = **//System function//
 +
 +The SY10EnterCriticalSection function __puts the calling task unit in a critical section__.
 +
 +===== IMPLEMENTATION =====
 +
 +**SY10EnterCriticalSection(lookPool)**
 +
 +Parameters:
 +
 +^IN/OUT^VARIABLE TYPE^EXAMPLE NAME^DIM^^
 +|  IN      |  CONST   |  unitID    |  L  | Caller ID unit task|
 +|  IN      |  ARRGBL  |  pool      |  B  | Critical section pools informations|
 +|  IN/OUT  |  GLOBAL  |  locked    |  F  | Lock state (0 = unlocked, 1 = locked)|
 +|  IN      |  CONST   |  blocking  |  L  | Lock mode (0 = non-blocking, 1 = blocking)|
 +
 +
 +Description:
 +
 +Through the SY10EnterCriticalSection call the unit task caller asks the system to enter a critical section.
 +
 +If the critical section is free caller will be assigned to the task by returning the State locked to 1.
 +If the task that requires you to enter the critical section is already entered, the function will return the State locked to 1 incrementing the counter of requests for the task in progress.
 +
 +If the critical section is already occupied by another unit task and the blocking mode is set to 0 and you will have immediate exit with status 0 locked.
 +
 +Otherwise based on the blocking you will have the return with locked state 0 or the unit task is put on hold and run automatically one context switch.
 +
 +=== Example ===
 +
 +The following example initializes an information pool used then to a critical section.
 +
 +\\
 +**task unit:**
 +<code QCL>
 +;===
 +; Unit B
 +;
 +GLOBAL
 + Counter L INOUT
 +
 +; local variables
 +CONST
 + UNIT_ID 2
 +
 +GLOBAL
 + locked F
 + looping L
 +
 +; main entry point
 +BEGIN
 + CALL TASK_INIT
 + WHILE TRUE
 + CALL TASK_EXECUTE
 + WAIT A_LOOP
 + ENDWHILE
 +END
 +
 +;===
 +; Task initialization
 +;
 +SUB TASK_INIT
 + WAIT INIT.Initialized
 +ENDSUB
 +
 +;===
 +; Task execution
 +;
 +SUB TASK_EXECUTE
 +
 + SY10EnterCriticalSection(UNIT_ID, LockPool, locked, TRUE)
 + CALL COUNTER_ADD
 + SY10LeaveCriticalSection(UNIT_ID, LockPool, locked, TRUE)
 +
 +ENDSUB
 +
 +;===
 +; Counter add
 +;
 +SUB COUNTER_ADD
 + Counter = Counter + 1
 +
 + ; this simulate an automatic context switch for a device write and read access
 + WAIT A_LOOP
 +ENDSUB
 +</code>