os_sem.c

lpc2368-keil环境下的ucos的移植例程

/*
*********************************************************************************************************
*   											 uC/OS-II
*   									   The Real-Time Kernel
*   									   SEMAPHORE MANAGEMENT
*
*   					   (c) Copyright 1992-2002, Jean J. Labrosse, Weston, FL
*   										All Rights Reserved
*
* File : OS_SEM.C
* By   : Jean J. Labrosse
*********************************************************************************************************
*/

#ifndef  OS_MASTER_FILE
#include "..\APP\includes.h"
#endif

#if OS_SEM_EN > 0
/*
*********************************************************************************************************
*   										ACCEPT SEMAPHORE
*
* Description: This function checks the semaphore to see if a resource is available or, if an event
*   		   occurred.  Unlike OSSemPend(), OSSemAccept() does not suspend the calling task if the
*   		   resource is not available or the event did not occur.
*
* Arguments  : pevent     is a pointer to the event control block
*
* Returns    : >  0 	  if the resource is available or the event did not occur the semaphore is
*   					  decremented to obtain the resource.
*   		   == 0 	  if the resource is not available or the event did not occur or,
*   					  if 'pevent' is a NULL pointer or,
*   					  if you didn't pass a pointer to a semaphore
*********************************************************************************************************
*/

#if OS_SEM_ACCEPT_EN > 0
INT16U OSSemAccept(OS_EVENT *pevent)
{
#if OS_CRITICAL_METHOD == 3 						  /* Allocate storage for CPU status register      */
	OS_CPU_SR  cpu_sr;
#endif    
	INT16U     cnt;


#if OS_ARG_CHK_EN > 0
	if (pevent == (OS_EVENT *) 0)
	{
		/* Validate 'pevent'							 */
		return (0);
	}
	if (pevent->OSEventType != OS_EVENT_TYPE_SEM)
	{
		/* Validate event block type					 */
		return (0);
	}
#endif
	OS_ENTER_CRITICAL();
	cnt = pevent->OSEventCnt;
	if (cnt > 0)
	{
		/* See if resource is available 				 */
		pevent->OSEventCnt--;   					  /* Yes, decrement semaphore and notify caller    */
	}
	OS_EXIT_CRITICAL();
	return (cnt);   								  /* Return semaphore count 					   */
}
#endif    

/*$PAGE*/
/*
*********************************************************************************************************
*   										CREATE A SEMAPHORE
*
* Description: This function creates a semaphore.
*
* Arguments  : cnt  		 is the initial value for the semaphore.  If the value is 0, no resource is
*   						 available (or no event has occurred).  You initialize the semaphore to a
*   						 non-zero value to specify how many resources are available (e.g. if you have
*   						 10 resources, you would initialize the semaphore to 10).
*
* Returns    : != (void *)0  is a pointer to the event control clock (OS_EVENT) associated with the
*   						 created semaphore
*   		   == (void *)0  if no event control blocks were available
*********************************************************************************************************
*/

OS_EVENT * OSSemCreate(INT16U cnt)
{
#if OS_CRITICAL_METHOD == 3 							   /* Allocate storage for CPU status register */
	OS_CPU_SR  cpu_sr;
#endif    
	OS_EVENT  *pevent;


	if (OSIntNesting > 0)
	{
		/* See if called from ISR ...   			*/
		return ((OS_EVENT *) 0);							/* ... can't CREATE from an ISR             */
	}
	OS_ENTER_CRITICAL();
	pevent = OSEventFreeList;   						   /* Get next free event control block 	   */
	if (OSEventFreeList != (OS_EVENT *) 0)
	{
		/* See if pool of free ECB pool was empty   */
		OSEventFreeList = (OS_EVENT *) OSEventFreeList->OSEventPtr;
	}
	OS_EXIT_CRITICAL();
	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 			   */
		OS_EventWaitListInit(pevent);   				   /* Initialize to 'nobody waiting' on sem.   */
	}
	return (pevent);
}

/*$PAGE*/
/*
*********************************************************************************************************
*   									  DELETE A SEMAPHORE
*
* Description: This function deletes a semaphore and readies all tasks pending on the semaphore.
*
* Arguments  : pevent   	 is a pointer to the event control block associated with the desired
*   						 semaphore.
*
*   		   opt  		 determines delete options as follows:
*   						 opt == OS_DEL_NO_PEND   Delete semaphore ONLY if no task pending
*   						 opt == OS_DEL_ALWAYS    Deletes the semaphore even if tasks are waiting.
*   												 In this case, all the tasks pending will be readied.
*
*   		   err  		 is a pointer to an error code that can contain one of the following values:
*   						 OS_NO_ERR  			 The call was successful and the semaphore was deleted
*   						 OS_ERR_DEL_ISR 		 If you attempted to delete the semaphore from an ISR
*   						 OS_ERR_INVALID_OPT 	 An invalid option was specified
*   						 OS_ERR_TASK_WAITING	 One or more tasks were waiting on the semaphore
*   						 OS_ERR_EVENT_TYPE  	 If you didn't pass a pointer to a semaphore
*   						 OS_ERR_PEVENT_NULL 	 If 'pevent' is a NULL pointer.
*
* Returns    : pevent   	 upon error
*   		   (OS_EVENT *)0 if the semaphore was successfully deleted.
*
* Note(s)    : 1) This function must be used with care.  Tasks that would normally expect the presence of
*   			  the semaphore MUST check the return code of OSSemPend().
*   		   2) OSSemAccept() callers will not know that the intended semaphore has been deleted unless
*   			  they check 'pevent' to see that it's a NULL pointer.
*   		   3) This call can potentially disable interrupts for a long time.  The interrupt disable
*   			  time is directly proportional to the number of tasks waiting on the semaphore.
*   		   4) Because ALL tasks pending on the semaphore will be readied, you MUST be careful in
*   			  applications where the semaphore is used for mutual exclusion because the resource(s)
*   			  will no longer be guarded by the semaphore.
*********************************************************************************************************
*/

#if OS_SEM_DEL_EN > 0
OS_EVENT * OSSemDel(OS_EVENT *pevent, INT8U opt, INT8U *err)
{
#if OS_CRITICAL_METHOD == 3 							   /* Allocate storage for CPU status register */
	OS_CPU_SR  cpu_sr;
#endif    
	BOOLEAN    tasks_waiting;


	if (OSIntNesting > 0)
	{
		/* See if called from ISR ...   			*/
		*err = OS_ERR_DEL_ISR;  						   /* ... can't DELETE from an ISR             */
		return (pevent);
	}
#if OS_ARG_CHK_EN > 0
	if (pevent == (OS_EVENT *) 0)
	{
		/* Validate 'pevent'						*/
		*err = OS_ERR_PEVENT_NULL;
		return (pevent);
	}
	if (pevent->OSEventType != OS_EVENT_TYPE_SEM)
	{
		/* Validate event block type				*/
		*err = OS_ERR_EVENT_TYPE;
		return (pevent);
	}
#endif
	OS_ENTER_CRITICAL();
	if (pevent->OSEventGrp != 0x00)
	{
		/* See if any tasks waiting on semaphore	*/
		tasks_waiting = TRUE;   						   /* Yes   								   */
	}
	else
	{
		tasks_waiting = FALSE;  						   /* No									   */
	}
	switch (opt)
	{
		case OS_DEL_NO_PEND:
			/* Delete semaphore only if no task waiting */
			if (tasks_waiting == FALSE)
			{
				pevent->OSEventType = OS_EVENT_TYPE_UNUSED;
				pevent->OSEventPtr = OSEventFreeList;    /* Return Event Control Block to free list  */
				OSEventFreeList = pevent;   		  /* Get next free event control block  	  */
				OS_EXIT_CRITICAL();
				*err = OS_NO_ERR;
				return ((OS_EVENT *) 0);				   /* Semaphore has been deleted			   */
			}
			else
			{
				OS_EXIT_CRITICAL();
				*err = OS_ERR_TASK_WAITING;
				return (pevent);
			}

		case OS_DEL_ALWAYS:
			/* Always delete the semaphore  			*/
			while (pevent->OSEventGrp != 0x00)
			{
				/* Ready ALL tasks waiting for semaphore	*/
				OS_EventTaskRdy(pevent, (void *) 0, OS_STAT_SEM);
			}
			pevent->OSEventType = OS_EVENT_TYPE_UNUSED;
			pevent->OSEventPtr = OSEventFreeList;   	 /* Return Event Control Block to free list  */
			OSEventFreeList = pevent;   			  /* Get next free event control block  	  */
			OS_EXIT_CRITICAL();
			if (tasks_waiting == TRUE)
			{
				/* Reschedule only if task(s) were waiting  */
				OS_Sched(); 							  /* Find highest priority task ready to run  */
			}
			*err = OS_NO_ERR;
			return ((OS_EVENT *) 0);					   /* Semaphore has been deleted			   */