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:
;=== ; 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