os_sem.c
上传用户:jingkewang
上传日期:2013-04-11
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文件大小:23k
- /*
- *********************************************************************************************************
- * uC/OS-II
- * The Real-Time Kernel
- * SEMAPHORE MANAGEMENT
- *
- * (c) Copyright 1992-2005, Jean J. Labrosse, Weston, FL
- * All Rights Reserved
- *
- * File : OS_SEM.C
- * By : Jean J. Labrosse
- * Version : V2.80
- *********************************************************************************************************
- */
- #ifndef OS_MASTER_FILE
- #include <ucos_ii.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)
- {
- INT16U cnt;
- #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 (pevent == (OS_EVENT *)0) { /* Validate 'pevent' */
- return (0);
- }
- #endif
- if (pevent->OSEventType != OS_EVENT_TYPE_SEM) { /* Validate event block type */
- return (0);
- }
- 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
- /*$PAGE*/
- /*
- *********************************************************************************************************
- * CREATE A SEMAPHORE
- *
- * Description: This function creates a semaphore.
- *
- * Arguments : cnt is the initial value for the semaphore. If the value is 0, no resource is
- * available (or no event has occurred). You initialize the semaphore to a
- * non-zero value to specify how many resources are available (e.g. if you have
- * 10 resources, you would initialize the semaphore to 10).
- *
- * Returns : != (void *)0 is a pointer to the event control clock (OS_EVENT) associated with the
- * created semaphore
- * == (void *)0 if no event control blocks were available
- *********************************************************************************************************
- */
- OS_EVENT *OSSemCreate (INT16U cnt)
- {
- OS_EVENT *pevent;
- #if OS_CRITICAL_METHOD == 3 /* Allocate storage for CPU status register */
- OS_CPU_SR cpu_sr = 0;
- #endif
- if (OSIntNesting > 0) { /* See if called from ISR ... */
- return ((OS_EVENT *)0); /* ... can't CREATE from an ISR */
- }
- OS_ENTER_CRITICAL();
- pevent = OSEventFreeList; /* Get next free event control block */
- if (OSEventFreeList != (OS_EVENT *)0) { /* See if pool of free ECB pool was empty */
- OSEventFreeList = (OS_EVENT *)OSEventFreeList->OSEventPtr;
- }
- OS_EXIT_CRITICAL();
- if (pevent != (OS_EVENT *)0) { /* Get an event control block */
- pevent->OSEventType = OS_EVENT_TYPE_SEM;
- pevent->OSEventCnt = cnt; /* Set semaphore value */
- pevent->OSEventPtr = (void *)0; /* Unlink from ECB free list */
- #if OS_EVENT_NAME_SIZE > 1
- pevent->OSEventName[0] = '?'; /* Unknown name */
- pevent->OSEventName[1] = OS_ASCII_NUL;
- #endif
- OS_EventWaitListInit(pevent); /* Initialize to 'nobody waiting' on sem. */
- }
- return (pevent);
- }
- /*$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)
- {
- BOOLEAN tasks_waiting;
- OS_EVENT *pevent_return;
- #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 (err == (INT8U *)0) { /* Validate 'err' */
- return (pevent);
- }
- if (pevent == (OS_EVENT *)0) { /* Validate 'pevent' */
- *err = OS_ERR_PEVENT_NULL;
- return (pevent);
- }
- #endif
- if (pevent->OSEventType != OS_EVENT_TYPE_SEM) { /* Validate event block type */
- *err = OS_ERR_EVENT_TYPE;
- return (pevent);
- }
- if (OSIntNesting > 0) { /* See if called from ISR ... */
- *err = OS_ERR_DEL_ISR; /* ... can't DELETE from an ISR */
- return (pevent);
- }
- OS_ENTER_CRITICAL();
- if (pevent->OSEventGrp != 0) { /* 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) {
- #if OS_EVENT_NAME_SIZE > 1
- pevent->OSEventName[0] = '?'; /* Unknown name */
- pevent->OSEventName[1] = OS_ASCII_NUL;
- #endif
- pevent->OSEventType = OS_EVENT_TYPE_UNUSED;
- pevent->OSEventPtr = OSEventFreeList; /* Return Event Control Block to free list */
- pevent->OSEventCnt = 0;
- OSEventFreeList = pevent; /* Get next free event control block */
- OS_EXIT_CRITICAL();
- *err = OS_NO_ERR;
- pevent_return = (OS_EVENT *)0; /* Semaphore has been deleted */
- } else {
- OS_EXIT_CRITICAL();
- *err = OS_ERR_TASK_WAITING;
- pevent_return = pevent;
- }
- break;
- case OS_DEL_ALWAYS: /* Always delete the semaphore */
- while (pevent->OSEventGrp != 0) { /* Ready ALL tasks waiting for semaphore */
- (void)OS_EventTaskRdy(pevent, (void *)0, OS_STAT_SEM);
- }
- #if OS_EVENT_NAME_SIZE > 1
- pevent->OSEventName[0] = '?'; /* Unknown name */
- pevent->OSEventName[1] = OS_ASCII_NUL;
- #endif
- pevent->OSEventType = OS_EVENT_TYPE_UNUSED;
- pevent->OSEventPtr = OSEventFreeList; /* Return Event Control Block to free list */
- pevent->OSEventCnt = 0;
- 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;
- pevent_return = (OS_EVENT *)0; /* Semaphore has been deleted */
- break;
- default:
- OS_EXIT_CRITICAL();
- *err = OS_ERR_INVALID_OPT;
- pevent_return = pevent;
- break;
- }
- return (pevent_return);
- }
- #endif
- /*$PAGE*/
- /*
- *********************************************************************************************************
- * PEND ON SEMAPHORE
- *
- * Description: This function waits for a semaphore.
- *
- * Arguments : pevent is a pointer to the event control block associated with the desired
- * semaphore.
- *
- * 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
- * semaphore or, until the resource becomes available (or the event occurs).
- *
- * err is a pointer to where an error message will be deposited. Possible error
- * messages are:
- *
- * OS_NO_ERR The call was successful and your task owns the resource
- * or, the event you are waiting for occurred.
- * OS_TIMEOUT The semaphore was not received within the specified
- * timeout.
- * OS_ERR_EVENT_TYPE If you didn't pass a pointer to a semaphore.
- * OS_ERR_PEND_ISR If you called this function from an ISR and the result
- * would lead to a suspension.
- * OS_ERR_PEVENT_NULL If 'pevent' is a NULL pointer.
- *
- * Returns : none
- *********************************************************************************************************
- */
- void OSSemPend (OS_EVENT *pevent, INT16U timeout, INT8U *err)
- {
- #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 (err == (INT8U *)0) { /* Validate 'err' */
- return;
- }
- if (pevent == (OS_EVENT *)0) { /* Validate 'pevent' */
- *err = OS_ERR_PEVENT_NULL;
- return;
- }
- #endif
- if (pevent->OSEventType != OS_EVENT_TYPE_SEM) { /* Validate event block type */
- *err = OS_ERR_EVENT_TYPE;
- return;
- }
- if (OSIntNesting > 0) { /* See if called from ISR ... */
- *err = OS_ERR_PEND_ISR; /* ... can't PEND from an ISR */
- return;
- }
- OS_ENTER_CRITICAL();
- if (pevent->OSEventCnt > 0) { /* If sem. is positive, resource available ... */
- pevent->OSEventCnt--; /* ... decrement semaphore only if positive. */
- OS_EXIT_CRITICAL();
- *err = OS_NO_ERR;
- return;
- }
- /* Otherwise, must wait until event occurs */
- OSTCBCur->OSTCBStat |= OS_STAT_SEM; /* Resource not available, pend on semaphore */
- OSTCBCur->OSTCBPendTO = FALSE;
- 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();
- if (OSTCBCur->OSTCBPendTO == TRUE) { /* See if we timedout */
- OS_EventTO(pevent);
- OS_EXIT_CRITICAL();
- *err = OS_TIMEOUT; /* Indicate that didn't get event within TO */
- return;
- }
- OSTCBCur->OSTCBEventPtr = (OS_EVENT *)0;
- OS_EXIT_CRITICAL();
- *err = OS_NO_ERR;
- }
- /*$PAGE*/
- /*
- *********************************************************************************************************
- * POST TO A SEMAPHORE
- *
- * Description: This function signals a semaphore
- *
- * Arguments : pevent is a pointer to the event control block associated with the desired
- * semaphore.
- *
- * Returns : OS_NO_ERR The call was successful and the semaphore was signaled.
- * OS_SEM_OVF If the semaphore count exceeded its limit. In other words, you have
- * signalled the semaphore more often than you waited on it with either
- * OSSemAccept() or OSSemPend().
- * OS_ERR_EVENT_TYPE If you didn't pass a pointer to a semaphore
- * OS_ERR_PEVENT_NULL If 'pevent' is a NULL pointer.
- *********************************************************************************************************
- */
- INT8U OSSemPost (OS_EVENT *pevent)
- {
- #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 (pevent == (OS_EVENT *)0) { /* Validate 'pevent' */
- return (OS_ERR_PEVENT_NULL);
- }
- #endif
- if (pevent->OSEventType != OS_EVENT_TYPE_SEM) { /* Validate event block type */
- return (OS_ERR_EVENT_TYPE);
- }
- OS_ENTER_CRITICAL();
- if (pevent->OSEventGrp != 0) { /* See if any task waiting for semaphore*/
- (void)OS_EventTaskRdy(pevent, (void *)0, OS_STAT_SEM); /* Ready HPT waiting on event */
- OS_EXIT_CRITICAL();
- OS_Sched(); /* Find HPT ready to run */
- return (OS_NO_ERR);
- }
- if (pevent->OSEventCnt < 65535u) { /* Make sure semaphore will not overflow */
- pevent->OSEventCnt++; /* Increment semaphore count to register event */
- OS_EXIT_CRITICAL();
- return (OS_NO_ERR);
- }
- OS_EXIT_CRITICAL(); /* Semaphore value has reached its maximum */
- return (OS_SEM_OVF);
- }
- /*$PAGE*/
- /*
- *********************************************************************************************************
- * QUERY A SEMAPHORE
- *
- * Description: This function obtains information about a semaphore
- *
- * Arguments : pevent is a pointer to the event control block associated with the desired
- * semaphore
- *
- * p_sem_data is a pointer to a structure that will contain information about the
- * semaphore.
- *
- * Returns : OS_NO_ERR The call was successful and the message was sent
- * OS_ERR_EVENT_TYPE If you are attempting to obtain data from a non semaphore.
- * OS_ERR_PEVENT_NULL If 'pevent' is a NULL pointer.
- * OS_ERR_PDATA_NULL If 'p_sem_data' is a NULL pointer
- *********************************************************************************************************
- */
- #if OS_SEM_QUERY_EN > 0
- INT8U OSSemQuery (OS_EVENT *pevent, OS_SEM_DATA *p_sem_data)
- {
- #if OS_LOWEST_PRIO <= 63
- INT8U *psrc;
- INT8U *pdest;
- #else
- INT16U *psrc;
- INT16U *pdest;
- #endif
- INT8U i;
- #if OS_CRITICAL_METHOD == 3 /* Allocate storage for CPU status register */
- OS_CPU_SR cpu_sr = 0;
- #endif
- #if OS_ARG_CHK_EN > 0
- if (pevent == (OS_EVENT *)0) { /* Validate 'pevent' */
- return (OS_ERR_PEVENT_NULL);
- }
- if (p_sem_data == (OS_SEM_DATA *)0) { /* Validate 'p_sem_data' */
- return (OS_ERR_PDATA_NULL);
- }
- #endif
- if (pevent->OSEventType != OS_EVENT_TYPE_SEM) { /* Validate event block type */
- return (OS_ERR_EVENT_TYPE);
- }
- OS_ENTER_CRITICAL();
- p_sem_data->OSEventGrp = pevent->OSEventGrp; /* Copy message mailbox wait list */
- psrc = &pevent->OSEventTbl[0];
- pdest = &p_sem_data->OSEventTbl[0];
- for (i = 0; i < OS_EVENT_TBL_SIZE; i++) {
- *pdest++ = *psrc++;
- }
- p_sem_data->OSCnt = pevent->OSEventCnt; /* Get semaphore count */
- OS_EXIT_CRITICAL();
- return (OS_NO_ERR);
- }
- #endif /* OS_SEM_QUERY_EN */
- /*$PAGE*/
- /*
- *********************************************************************************************************
- * SET SEMAPHORE
- *
- * Description: This function sets the semaphore count to the value specified as an argument. Typically,
- * this value would be 0.
- *
- * You would typically use this function when a semaphore is used as a signaling mechanism
- * and, you want to reset the count value.
- *
- * Arguments : pevent is a pointer to the event control block
- *
- * cnt is the new value for the semaphore count. You would pass 0 to reset the
- * semaphore count.
- *
- * err is a pointer to an error code returned by the function as follows:
- *
- * OS_NO_ERR The call was successful and the semaphore value was set.
- * OS_ERR_EVENT_TYPE If you didn't pass a pointer to a semaphore.
- * OS_ERR_PEVENT_NULL If 'pevent' is a NULL pointer.
- * OS_ERR_TASK_WAITING If tasks are waiting on the semaphore.
- *********************************************************************************************************
- */
- #if OS_SEM_SET_EN > 0
- void OSSemSet (OS_EVENT *pevent, INT16U cnt, INT8U *err)
- {
- #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 (err == (INT8U *)0) { /* Validate 'err' */
- return;
- }
- if (pevent == (OS_EVENT *)0) { /* Validate 'pevent' */
- *err = OS_ERR_PEVENT_NULL;
- return;
- }
- #endif
- if (pevent->OSEventType != OS_EVENT_TYPE_SEM) { /* Validate event block type */
- *err = OS_ERR_EVENT_TYPE;
- return;
- }
- OS_ENTER_CRITICAL();
- *err = OS_NO_ERR;
- if (pevent->OSEventCnt > 0) { /* See if semaphore already has a count */
- pevent->OSEventCnt = cnt; /* Yes, set it to the new value specified. */
- } else { /* No */
- if (pevent->OSEventGrp == 0) { /* See if task(s) waiting? */
- pevent->OSEventCnt = cnt; /* No, OK to set the value */
- } else {
- *err = OS_ERR_TASK_WAITING;
- }
- }
- OS_EXIT_CRITICAL();
- }
- #endif
- #endif /* OS_SEM_EN */