μC/OS-II—Semaphore management 1 (os_sem.c)

Directory

• Semaphore management
• • Semaphore creation
  • Semaphore deletion
  • Get/wait for semaphore
  • emit semaphore

Semaphore management

Semaphore creation

OS_EVENT *OSSemCreate (INT16U cnt)
{<!-- -->
OS_EVENT *pevent;
#if OS_CRITICAL_METHOD == 3u /* Allocate storage for CPU status register */
OS_CPU_SR cpu_sr = 0u;
#endif
#ifdef OS_SAFETY_CRITICAL_IEC61508
\t
if (OSSafetyCriticalStartFlag == OS_TRUE)
{<!-- -->
OS_SAFETY_CRITICAL_EXCEPTION();
return ((OS_EVENT *)0);
}
\t
#endif
\t
if (OSIntNesting > 0u) /* See if called from ISR ... */
{<!-- -->
return ((OS_EVENT *)0); /* ... can't CREATE from an ISR */
}
\t
OS_ENTER_CRITICAL();
pevent = OSEventFreeList; /* Get next free event control block */
\t
if (OSEventFreeList != (OS_EVENT *)0) /* See if pool of free ECB pool was empty */
{<!-- -->
OSEventFreeList = (OS_EVENT *)OSEventFreeList->OSEventPtr;
}
\t
OS_EXIT_CRITICAL();
\t
if (pevent != (OS_EVENT *)0) /* Get an event control block */
{<!-- -->
pevent->OSEventType = OS_EVENT_TYPE_SEM;
pevent->OSEventCnt = cnt; /* Set semaphore value */
pevent->OSEventPtr = (void *)0; /* Unlink from ECB free list */
#if OS_EVENT_NAME_EN > 0u
pevent->OSEventName = (INT8U *) (void *)"?";
#endif
OS_EventWaitListInit (pevent); /* Initialize to 'nobody waiting' on sem. */
}
\t
return (pevent);
}

Semaphore deletion

#if OS_SEM_DEL_EN > 0u
OS_EVENT *OSSemDel (OS_EVENT *pevent,
INT8U opt,
INT8U *perr)
{<!-- -->
BOOLEAN tasks_waiting;
OS_EVENT *pevent_return;
#if OS_CRITICAL_METHOD == 3u /* Allocate storage for CPU status register */
OS_CPU_SR cpu_sr = 0u;
#endif
#ifdef OS_SAFETY_CRITICAL
\t
if (perr == (INT8U *)0)
{<!-- -->
OS_SAFETY_CRITICAL_EXCEPTION();
return ((OS_EVENT *)0);
}
\t
#endif
#if OS_ARG_CHK_EN > 0u
\t
if (pevent == (OS_EVENT *)0) /* Validate 'pevent' */
{<!-- -->
*perr = OS_ERR_PEVENT_NULL;
return (pevent);
}
\t
#endif
\t
if (pevent->OSEventType != OS_EVENT_TYPE_SEM) /* Validate event block type */
{<!-- -->
*perr = OS_ERR_EVENT_TYPE;
return (pevent);
}
\t
if (OSIntNesting > 0u) /* See if called from ISR ... */
{<!-- -->
*perr = OS_ERR_DEL_ISR; /* ... can't DELETE from an ISR */
return (pevent);
}
\t
OS_ENTER_CRITICAL();
\t
if (pevent->OSEventGrp != 0u) /* See if any tasks waiting on semaphore */
{<!-- -->
tasks_waiting = OS_TRUE; /* Yes */
}
\t
else
{<!-- -->
tasks_waiting = OS_FALSE; /* No */
}
\t
switch (opt)
{<!-- -->
case OS_DEL_NO_PEND: /* Delete semaphore only if no task waiting */
if (tasks_waiting == OS_FALSE)
{<!-- -->
#if OS_EVENT_NAME_EN > 0u
pevent->OSEventName = (INT8U *) (void *)"?";
#endif
pevent->OSEventType = OS_EVENT_TYPE_UNUSED;
pevent->OSEventPtr = OSEventFreeList; /* Return Event Control Block to free list */
pevent->OSEventCnt = 0u;
OSEventFreeList = pevent; /* Get next free event control block */
OS_EXIT_CRITICAL();
*perr = OS_ERR_NONE;
pevent_return = (OS_EVENT *)0; /* Semaphore has been deleted */
}
\t\t\t
else
{<!-- -->
OS_EXIT_CRITICAL();
*perr = OS_ERR_TASK_WAITING;
pevent_return = pevent;
}
\t\t\t
break;
\t\t\t
case OS_DEL_ALWAYS: /* Always delete the semaphore */
while (pevent->OSEventGrp != 0u) /* Ready ALL tasks waiting for semaphore */
{<!-- -->
(void)OS_EventTaskRdy (pevent, (void *)0, OS_STAT_SEM, OS_STAT_PEND_ABORT);
}
\t\t\t
#if OS_EVENT_NAME_EN > 0u
pevent->OSEventName = (INT8U *) (void *)"?";
#endif
pevent->OSEventType = OS_EVENT_TYPE_UNUSED;
pevent->OSEventPtr = OSEventFreeList; /* Return Event Control Block to free list */
pevent->OSEventCnt = 0u;
OSEventFreeList = pevent; /* Get next free event control block */
OS_EXIT_CRITICAL();
\t\t\t
if (tasks_waiting == OS_TRUE) /* Reschedule only if task(s) were waiting */
{<!-- -->
OS_Sched(); /* Find highest priority task ready to run */
}
\t\t\t
*perr = OS_ERR_NONE;
pevent_return = (OS_EVENT *)0; /* Semaphore has been deleted */
break;
\t\t\t
default:
OS_EXIT_CRITICAL();
*perr = OS_ERR_INVALID_OPT;
pevent_return = pevent;
break;
}
\t
return (pevent_return);
}
#endif

Get/wait for semaphore

void OSSemPend (OS_EVENT *pevent,
INT32U timeout,
INT8U *perr)
{<!-- -->
#if OS_CRITICAL_METHOD == 3u /* Allocate storage for CPU status register */
OS_CPU_SR cpu_sr = 0u;
#endif
#ifdef OS_SAFETY_CRITICAL
\t
if (perr == (INT8U *)0)
{<!-- -->
OS_SAFETY_CRITICAL_EXCEPTION();
return;
}
\t
#endif
#if OS_ARG_CHK_EN > 0u
\t
if (pevent == (OS_EVENT *)0) /* Validate 'pevent' */
{<!-- -->
*perr = OS_ERR_PEVENT_NULL;
return;
}
\t
#endif
\t
if (pevent->OSEventType != OS_EVENT_TYPE_SEM) /* Validate event block type */
{<!-- -->
*perr = OS_ERR_EVENT_TYPE;
return;
}
\t
if (OSIntNesting > 0u) /* See if called from ISR ... */
{<!-- -->
*perr = OS_ERR_PEND_ISR; /* ... can't PEND from an ISR */
return;
}
\t
if (OSLockNesting > 0u) /* See if called with scheduler locked ... */
{<!-- -->
*perr = OS_ERR_PEND_LOCKED; /* ... can't PEND when locked */
return;
}
\t
OS_ENTER_CRITICAL();
\t
if (pevent->OSEventCnt > 0u) /* If sem. is positive, resource available ... */
{<!-- -->
pevent->OSEventCnt--; /* ... decrement semaphore only if positive. */
OS_EXIT_CRITICAL();
*perr = OS_ERR_NONE;
return;
}
\t
/* Otherwise, must wait until event occurs */
OSTCBCur->OSTCBStat |= OS_STAT_SEM; /* Resource not available, pend on semaphore */
OSTCBCur->OSTCBStatPend = OS_STAT_PEND_OK;
OSTCBCur->OSTCBDly = timeout; /* Store pend timeout in 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();
\t
switch (OSTCBCur->OSTCBStatPend) /* See if we timed-out or aborted */
{<!-- -->
case OS_STAT_PEND_OK:
*perr = OS_ERR_NONE;
break;
\t\t\t
case OS_STAT_PEND_ABORT:
*perr = OS_ERR_PEND_ABORT; /* Indicate that we aborted */
break;
\t\t\t
case OS_STAT_PEND_TO:
default:
OS_EventTaskRemove (OSTCBCur, pevent);
*perr = OS_ERR_TIMEOUT; /* Indicate that we didn't get event within TO */
break;
}
\t
OSTCBCur->OSTCBStat = OS_STAT_RDY; /* Set task status to ready */
OSTCBCur->OSTCBStatPend = OS_STAT_PEND_OK; /* Clear pend status */
OSTCBCur->OSTCBEventPtr = (OS_EVENT *)0; /* Clear event pointers */
#if (OS_EVENT_MULTI_EN > 0u)
OSTCBCur->OSTCBEventMultiPtr = (OS_EVENT **)0;
#endif
OS_EXIT_CRITICAL();
}

Emit semaphore

INT8U OSSemPost (OS_EVENT *pevent)
{<!-- -->
#if OS_CRITICAL_METHOD == 3u /* Allocate storage for CPU status register */
OS_CPU_SR cpu_sr = 0u;
#endif
#if OS_ARG_CHK_EN > 0u
\t
if (pevent == (OS_EVENT *)0) /* Validate 'pevent' */
{<!-- -->
return (OS_ERR_PEVENT_NULL);
}
\t
#endif
\t
if (pevent->OSEventType != OS_EVENT_TYPE_SEM) /* Validate event block type */
{<!-- -->
return (OS_ERR_EVENT_TYPE);
}
\t
OS_ENTER_CRITICAL();
\t
if (pevent->OSEventGrp != 0u) /* See if any task waiting for semaphore */
{<!-- -->
/* Ready HPT waiting on event */
(void)OS_EventTaskRdy (pevent, (void *)0, OS_STAT_SEM, OS_STAT_PEND_OK);
OS_EXIT_CRITICAL();
OS_Sched(); /* Find HPT ready to run */
return (OS_ERR_NONE);
}
\t
if (pevent->OSEventCnt < 65535u) /* Make sure semaphore will not overflow */
{<!-- -->
pevent->OSEventCnt + + ; /* Increment semaphore count to register event */
OS_EXIT_CRITICAL();
return (OS_ERR_NONE);
}
\t
OS_EXIT_CRITICAL(); /* Semaphore value has reached its maximum */
return (OS_ERR_SEM_OVF);
}