Mutual Exclusion Semaphores

Table C-11 shows the difference in API for mutual exclusion semaphore management.

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)

Table C-11 Mutual Exclusion Semaphore Management API

TC-11(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.

TC-11(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.

TC-11(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.

TC-11(4) µC/OS-III does not provide query services as they were rarely used.