Mutexes are used for task synchronization. A source code area that is protected by a mutex can only be executed by one task at the time. The mechanism is comparable with a semaphore that is initialized with a counter of 1. A mutex is a special semaphore, that allows a task having the mutex locked can execute the mutex lock functions again and again without being blocked (this is called reentrancy).
§ posMutexCreate()
| POSEXTERN POSMUTEX_t POSCALL posMutexCreate |
( |
void |
| ) |
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§ posMutexDestroy()
| POSEXTERN void POSCALL posMutexDestroy |
( |
POSMUTEX_t |
mutex | ) |
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§ posMutexLock()
Mutex function. This function locks a code section so that only one task can execute the code at a time. If an other task already has the lock, the task requesting the lock will be blocked until the mutex is unlocked again. Note that a posMutexLock appears always in a pair with posMutexUnlock.
- Parameters
-
| mutex | handle to the mutex object. |
- Returns
- zero on success.
- Note
- POSCFG_FEATURE_MUTEXES must be defined to 1 to have mutex support compiled in.
- See also
- posMutexTryLock, posMutexUnlock, posMutexCreate
§ posMutexTryLock()
Mutex function. Tries to get the mutex lock. This function does not block when the mutex is not available, instead it returns a value showing that the mutex could not be locked.
- Parameters
-
| mutex | handle to the mutex object. |
- Returns
- zero when the mutex lock could be set. Otherwise, when the mutex lock is yet helt by an other task, the function returns 1. A negative value is returned on error.
- Note
- POSCFG_FEATURE_MUTEXES must be defined to 1 to have mutex support compiled in.
POSCFG_FEATURE_MUTEXTRYLOCK must be defined to 1 to have this function compiled in.
- See also
- posMutexLock, posMutexUnlock, posMutexCreate
§ posMutexUnlock()
