大家来看个关于看门狗程序

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/* countingSemDemo.c - Demonstrates task synchronization using counting
* semaphores.
*/

/* Copyright 1984-1997 Wind River Systems, Inc. */

/*
modification history
--------------------
01c,06nov97,mm added copyright.
01b,16sep97,ram included files stdio.h, taskLib.h, usrLib.h, sysLib.h
Used the semShow() function to display info about
the semaphore inplace of the show() function.
01a,27mar94,ms cleaned up for VxDemo
*/

/*
* DESCRIPTION
* Counting semaphore example. Using binary semaphores for task
* synchronization may, if the events can occur rapidly enough, cause
* a loss of data, i.e. an event can be missed if the events can occur
* faster then a task can process them. Using counting semaphores may
* solve this problem. This program demonstrates task synchronization using
* counting semaphores. User can also select to use a binary semaphore instead
* of a counting semaphore in this demonstration, for comparision between the
* two semaphores.
*
* RETURNS: OK or ERROR
*
* EXAMPLE
*
* -> sp countingSemDemo, typeOfSemaphore
*
* where typeOfSemaphore is the value of the type of semaphore to be used
* for task synchronization in this demonstration. For using counting
* semaphores use a value 'c' or 'C' for typeOfSemaphore parameter and for
* using binary semaphores use a value 'b' or 'B' for typeOfSemaphore
* parameter.
*
* example:
* -> sp countingSemDemo, 'c'
* -> sp countingSemDemo, 'b'
*
*/

/* include files */

#include "vxWorks.h"
#include "wdLib.h"
#include "stdio.h"
#include "semLib.h"
#include "taskLib.h"
#include "usrLib.h"
#include "sysLib.h"

/* defines */

#define TASK_PRIORITY 101
#define TASK_STACK_SIZE 5000
#define TIME_BETWEEN_INTERRUPTS 1 /* 1 tick */
#define TASK_WORK_TIME 2 /* 2 ticks */
#define NUM_OF_GIVES 3

/* globals */

LOCAL SEM_ID semId = NULL; /* counting or binary semaphore ID */
LOCAL WDOG_ID wdId = NULL; /* watchdog ID */
LOCAL int syncTaskTid = 0; /* tid of syncTask */
LOCAL int numToGive = NUM_OF_GIVES; /* Number of times semGive is called */

/* forward declaratiuon */
void syncISR(int); /* ISR to unblock syncTask */
void cleanUp (); /* cleanup routine */
void syncTask (); /* task that needs to be synchronized
* with external events */

/*****************************************************************************
* countingSemDemo - demonstrates task synchronization using counting
* semaphores. User can also select to use binary semaphore instead of
* counting semaphore in this demonstration, for comparision between the two
* semaphores.
*
* RETURNS: OK or ERROR
*
*/

STATUS countingSemDemo
(
char semType /* counting semaphore type 'c' or binary semaphore
* type 'b'
*/
)
{
switch (semType)
{
case 'c':
case 'C':
if ((semId = semCCreate (SEM_Q_PRIORITY, 0)) == NULL)
{
perror ("semCCreate");
return (ERROR);
}
break;

case 'b':
case 'B':
if ((semId = semBCreate(SEM_Q_PRIORITY, SEM_EMPTY)) == NULL)
{
perror ("semBCreate");
return (ERROR);
}
break;

default:
printf ("Unknown semType -- must be 'c' or 'b'\n");
return (ERROR);
}

if ((wdId = wdCreate()) == NULL)
{
perror ("wdCreate");
cleanUp ();
return (ERROR);
}

if ((syncTaskTid = taskSpawn ("tsyncTask", TASK_PRIORITY, 0,TASK_STACK_SIZE,(FUNCPTR) syncTask, 0,0,0,0,0,0,0,0,0,0)) == ERROR)
{
perror ("taskSpawn");
cleanUp();
return (ERROR);
}

/* watchdog simulates hardware interrupts */
if (wdStart (wdId, TIME_BETWEEN_INTERRUPTS, (FUNCPTR) syncISR, numToGive)
== ERROR)
{
perror ("wdStart");
cleanUp ();
return (ERROR);
}

/* arbitrary delay to allow program to complete before clean up */
taskDelay (sysClkRateGet() + ((TASK_WORK_TIME + 2) * numToGive));

cleanUp();
return (OK);
}

/*****************************************************************************
* syncTask - synchronizes with interrupts using counting or binary
* semaphores.
*/

void syncTask (void)
{
int eventCount = 0;

FOREVER
{
if (semTake (semId, WAIT_FOREVER) == ERROR)
{
perror ("syncTask semTake");
return;
}

/* Do "work" */
taskDelay (TASK_WORK_TIME);
semShow (semId,1);

eventCount++;
printf ("semaphore taken %d times\n", eventCount);
}

}

/*****************************************************************************
* syncISR - simulates a hardware device which generates interrupts very
* quickly and synchronizes with syncTask using semaphores.
*/
void syncISR
(
int times
)
{
semGive (semId);
times--;
if (times > 0)
wdStart (wdId, TIME_BETWEEN_INTERRUPTS, (FUNCPTR) syncISR, times);
}

/*****************************************************************************
* cleanUP - deletes the syncTask, deletes the semaphore and the watchdog timer
* previously created by countingSemDemo.
*/
void cleanUp ()
{
if (syncTaskTid)
taskDelete (syncTaskTid);
if (semId)
semDelete (semId);
if (wdId)
wdDelete (wdId);

}

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从网上找的：

WatchDog
VxWorks提供了一个看门狗定时器（watchdog timer）机制，利用提供的函数，任何任务都可以创建一个看门狗定时器，经过指定的延时后，实现在系统时钟ISR的上下文中运行指定的程序。在VxWorks中，看门狗定时器作为系统时钟中断服务程序的一部分来维护。因此，与看门狗定时器相联系的函数运行在系统时钟中断级。在使用看门狗定时器实现定时/延时时，经过指定的时间，应用程序中断在系统时钟中断优先级上面，然而，如果内核不能立即执行这个中断服务程序，这个任务就被排队到tExcTask 工作队列中去，处在 tExcTask工作队列中的任务的优先级为 tExcTask (通常是 0)。对于使用看门狗定时器的中断服务程序，仍然必须遵守一般的ISR所要遵守的规则。通过wdCreate( )可以创建一个看门狗定时器。调用wdStart()启动定时器，延时参数以tick为单位，同时还要指定定时完成后要调用的程序。如果你的应用程序需要多个看门狗函数，使用wdCreate( )为每个需求产生独立的看门狗ID。因为对于给定的看门狗ID，只有最近的wdStart()有效。在指定的tick计数到达之前，要取消一个看门狗计时器，可以调用wdCancel()实现。每调用一次wdStart()，看门狗定时器只执行一次。对于一些要求周期性执行的应用程序。要获得该效果，定时器函数本身必须通过递归调用wdStart()来重新启动定时器。利用看门狗定时器，调用的任务不会被阻塞：因为wdStart()调用是立即返回的。使用该方法实现延时，关联函数所受限制太大，好多系统调用不可用，郁闷也…

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任务的优先级的问题

这个问题，你可以发到vxworks的板块，那里会有比较多的同学。

本想帮你移动过去，无奈，不知道咋移动的！

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