📄 os_mutex.lst
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*
* Arguments : pevent is a pointer to the event control block associated with the desired
C51 COMPILER V7.50 OS_MUTEX 12/14/2007 08:25:51 PAGE 7
* mutex.
*
* timeout is an optional timeout period (in clock ticks). If non-zero, your task will
* wait for the resource up to the amount of time specified by this argument.
* If you specify 0, however, your task will wait forever at the specified
* mutex or, until the resource becomes available.
*
* perr is a pointer to where an error message will be deposited. Possible error
* messages are:
* OS_ERR_NONE The call was successful and your task owns the mutex
* OS_ERR_TIMEOUT The mutex was not available within the specified 'timeo
-ut'.
* OS_ERR_PEND_ABORT The wait on the mutex was aborted.
* OS_ERR_EVENT_TYPE If you didn't pass a pointer to a mutex
* OS_ERR_PEVENT_NULL 'pevent' is a NULL pointer
* OS_ERR_PEND_ISR If you called this function from an ISR and the result
* would lead to a suspension.
* OS_ERR_PIP_LOWER If the priority of the task that owns the Mutex is
* HIGHER (i.e. a lower number) than the PIP. This error
* indicates that you did not set the PIP higher (lower
* number) than ALL the tasks that compete for the Mutex.
* Unfortunately, this is something that could not be
* detected when the Mutex is created because we don't kno
-w
* what tasks will be using the Mutex.
* OS_ERR_PEND_LOCKED If you called this function when the scheduler is locke
-d
*
* Returns : none
*
* Note(s) : 1) The task that owns the Mutex MUST NOT pend on any other event while it owns the mutex.
*
* 2) You MUST NOT change the priority of the task that owns the mutex
*********************************************************************************************************
*/
void OSMutexPend (OS_EVENT *pevent, INT16U timeout, INT8U *perr) reentrant
{
INT8U pip; /* Priority Inheritance Priority (PIP) */
INT8U mprio; /* Mutex owner priority */
BOOLEAN rdy; /* Flag indicating task was ready */
OS_TCB *ptcb;
OS_EVENT *pevent2;
INT8U y;
INT8U pend_stat;
#if OS_CRITICAL_METHOD == 3 /* Allocate storage for CPU status register */
OS_CPU_SR cpu_sr = 0;
#endif
#if OS_ARG_CHK_EN > 0
if (perr == (INT8U *)0) { /* Validate 'perr' */
return;
}
if (pevent == (OS_EVENT *)0) { /* Validate 'pevent' */
*perr = OS_ERR_PEVENT_NULL;
return;
}
#endif
if (pevent->OSEventType != OS_EVENT_TYPE_MUTEX) { /* Validate event block type */
*perr = OS_ERR_EVENT_TYPE;
return;
C51 COMPILER V7.50 OS_MUTEX 12/14/2007 08:25:51 PAGE 8
}
if (OSIntNesting > 0) { /* See if called from ISR ... */
*perr = OS_ERR_PEND_ISR; /* ... can't PEND from an ISR */
return;
}
if (OSLockNesting > 0) { /* See if called with scheduler locked ... */
*perr = OS_ERR_PEND_LOCKED; /* ... can't PEND when locked */
return;
}
OS_ENTER_CRITICAL();
pip = (INT8U)(pevent->OSEventCnt >> 8); /* Get PIP from mutex */
/* Is Mutex available? */
if ((INT8U)(pevent->OSEventCnt & OS_MUTEX_KEEP_LOWER_8) == OS_MUTEX_AVAILABLE) {
pevent->OSEventCnt &= OS_MUTEX_KEEP_UPPER_8; /* Yes, Acquire the resource */
pevent->OSEventCnt |= OSTCBCur->OSTCBPrio; /* Save priority of owning task */
pevent->OSEventPtr = (void *)OSTCBCur; /* Point to owning task's OS_TCB */
if (OSTCBCur->OSTCBPrio <= pip) { /* PIP 'must' have a SMALLER prio ... */
OS_EXIT_CRITICAL(); /* ... than current task! */
*perr = OS_ERR_PIP_LOWER;
} else {
OS_EXIT_CRITICAL();
*perr = OS_ERR_NONE;
}
return;
}
mprio = (INT8U)(pevent->OSEventCnt & OS_MUTEX_KEEP_LOWER_8); /* No, Get priority of mutex owner */
ptcb = (OS_TCB *)(pevent->OSEventPtr); /* Point to TCB of mutex owner */
if (ptcb->OSTCBPrio > pip) { /* Need to promote prio of owner?*/
if (mprio > OSTCBCur->OSTCBPrio) {
y = ptcb->OSTCBY;
if ((OSRdyTbl[y] & ptcb->OSTCBBitX) != 0) { /* See if mutex owner is ready */
OSRdyTbl[y] &= ~ptcb->OSTCBBitX; /* Yes, Remove owner from Rdy ...*/
if (OSRdyTbl[y] == 0) { /* ... list at current prio */
OSRdyGrp &= ~ptcb->OSTCBBitY;
}
rdy = OS_TRUE;
} else {
pevent2 = ptcb->OSTCBEventPtr;
if (pevent2 != (OS_EVENT *)0) { /* Remove from event wait list */
if ((pevent2->OSEventTbl[ptcb->OSTCBY] &= ~ptcb->OSTCBBitX) == 0) {
pevent2->OSEventGrp &= ~ptcb->OSTCBBitY;
}
}
rdy = OS_FALSE; /* No */
}
ptcb->OSTCBPrio = pip; /* Change owner task prio to PIP */
#if OS_LOWEST_PRIO <= 63
ptcb->OSTCBY = (INT8U)( ptcb->OSTCBPrio >> 3);
ptcb->OSTCBX = (INT8U)( ptcb->OSTCBPrio & 0x07);
ptcb->OSTCBBitY = (INT8U)(1 << ptcb->OSTCBY);
ptcb->OSTCBBitX = (INT8U)(1 << ptcb->OSTCBX);
#else
ptcb->OSTCBY = (INT8U)((ptcb->OSTCBPrio >> 4) & 0xFF);
ptcb->OSTCBX = (INT8U)( ptcb->OSTCBPrio & 0x0F);
ptcb->OSTCBBitY = (INT16U)(1 << ptcb->OSTCBY);
ptcb->OSTCBBitX = (INT16U)(1 << ptcb->OSTCBX);
#endif
if (rdy == OS_TRUE) { /* If task was ready at owner's priority ...*/
OSRdyGrp |= ptcb->OSTCBBitY; /* ... make it ready at new priority. */
OSRdyTbl[ptcb->OSTCBY] |= ptcb->OSTCBBitX;
} else {
pevent2 = ptcb->OSTCBEventPtr;
C51 COMPILER V7.50 OS_MUTEX 12/14/2007 08:25:51 PAGE 9
if (pevent2 != (OS_EVENT *)0) { /* Add to event wait list */
pevent2->OSEventGrp |= ptcb->OSTCBBitY;
pevent2->OSEventTbl[ptcb->OSTCBY] |= ptcb->OSTCBBitX;
}
}
OSTCBPrioTbl[pip] = ptcb;
}
}
OSTCBCur->OSTCBStat |= OS_STAT_MUTEX; /* Mutex not available, pend current task */
OSTCBCur->OSTCBStatPend = OS_STAT_PEND_OK;
OSTCBCur->OSTCBDly = timeout; /* Store timeout in current task's TCB */
OS_EventTaskWait(pevent); /* Suspend task until event or timeout occurs */
OS_EXIT_CRITICAL();
OS_Sched(); /* Find next highest priority task ready */
OS_ENTER_CRITICAL();
if (OSTCBCur->OSTCBStatPend != OS_STAT_PEND_OK) { /* See if we timed out during the pend */
pend_stat = OSTCBCur->OSTCBStatPend;
OS_EventTOAbort(pevent);
OS_EXIT_CRITICAL();
switch (pend_stat) {
case OS_STAT_PEND_TO:
default:
*perr = OS_ERR_TIMEOUT; /* Indicate that we didn't get mutex within TO */
break;
case OS_STAT_PEND_ABORT:
*perr = OS_ERR_PEND_ABORT; /* Indicate that we aborted getting mutex */
break;
}
return;
}
OSTCBCur->OSTCBEventPtr = (OS_EVENT *)0;
OS_EXIT_CRITICAL();
*perr = OS_ERR_NONE;
}
/*$PAGE*/
/*
*********************************************************************************************************
* POST TO A MUTUAL EXCLUSION SEMAPHORE
*
* Description: This function signals a mutual exclusion semaphore
*
* Arguments : pevent is a pointer to the event control block associated with the desired
* mutex.
*
* Returns : OS_ERR_NONE The call was successful and the mutex was signaled.
* OS_ERR_EVENT_TYPE If you didn't pass a pointer to a mutex
* OS_ERR_PEVENT_NULL 'pevent' is a NULL pointer
* OS_ERR_POST_ISR Attempted to post from an ISR (not valid for MUTEXes)
* OS_ERR_NOT_MUTEX_OWNER The task that did the post is NOT the owner of the MUTEX.
* OS_ERR_PIP_LOWER If the priority of the new task that owns the Mutex is
* HIGHER (i.e. a lower number) than the PIP. This error
* indicates that you did not set the PIP higher (lower
* number) than ALL the tasks that compete for the Mutex.
* Unfortunately, this is something that could not be
* detected when the Mutex is created because we don't know
* what tasks will be using the Mutex.
*********************************************************************************************************
*/
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