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Mutual Exclusion Semaphores API Changes

Mutual Exclusion Semaphores API Changes

Mar 23, 2021

The table below shows the difference in API for mutual exclusion semaphore management.

Mutual Exclusion Semaphores API

µC/OS-II (os_mutex.c)

µC/OS-III (os_mutex.c)

Note

BOOLEAN OSMutexAccept( OS_EVENT *pevent, INT8U *perr);

(1)

OS_EVENT * OSMutexCreate( INT8U prio, INT8U *perr);

void OSMutexCreate( OS_MUTEX *p_mutex, CPU_CHAR *p_name, OS_ERR *p_err);

(2)

OS_EVENT * OSMutexDel( OS_EVENT *pevent, INT8U opt, INT8U *perr);

void OSMutexDel( OS_MUTEX *p_mutex, OS_OPT opt, OS_ERR *p_err);

void OSMutexPend( OS_EVENT *pevent, INT32U timeout, INT8U *perr);

void OSMutexPend( OS_MUTEX *p_mutex, OS_TICK timeout, OS_OPT opt, CPU_TS *p_ts, OS_ERR *p_err);

(3)

OS_OBJ_QTY OSMutexPendAbort( OS_MUTEX *p_mutex, OS_OPT opt, OS_ERR *p_err);

INT8U OSMutexPost( OS_EVENT *pevent);

void OSMutexPost( OS_MUTEX *p_mutex, OS_OPT opt, OS_ERR *p_err);

INT8U OSMutexQuery( OS_EVENT *pevent, OS_MUTEX_DATA *p_mutex_data);

(4)

(1) In µC/OS-III, there is no “accept” API, since this feature is built into the OSMutexPend() by specifying the OS_OPT_PEND_NON_BLOCKING option.

(2) In µC/OS-II, OSMutexCreate() returns the address of an OS_EVENT, which is used as the “handle” to the message mailbox. In µC/OS-III, the application must allocate storage for an OS_MUTEX, which serves the same purpose as the OS_EVENT. The benefit in µC/OS-III is that it is not necessary to predetermine the number of mutual-exclusion semaphores at compile time.

(3) µC/OS-III returns additional information when a mutex is released. The releaser takes a snapshot of the current time stamp and stores it in the OS_MUTEX. The new owner of the mutex therefore knows when the mutex was released.

(4) µC/OS-III does not provide query services as they were rarely used.