VxWorks任务改变优先级示例

/* includes */
#include "vxWorks.h"
#include "taskLib.h"
#include "kernelLib.h"
#include "sysLib.h"

 

/* function prototypes */
void taskOne(void);
void taskTwo(void);
void taskThree(void);

 

/* globals */
#define ITER1 100
#define ITER2 10
#define HIGH 100 /* high priority */
#define MID 101 /* medium priority */
#define LOW 102 /* low priority */
#define LONG_TIME 0xFFFFFFL

 

void sched(void) /* function to create the two tasks */
{
    int taskIdOne, taskIdTwo, taskIdThree, taskIdFour;
    printf("\n\n\n\n\n");
   
    /* spawn the three tasks */
    if ((taskIdOne = taskSpawn("task1", LOW, 0x100, 20000, (FUNCPTR)taskOne, 0, 0,
                            0, 0, 0, 0, 0, 0, 0, 0)) == ERROR)
        printf("taskSpawn taskOne failed\n");
   
    if ((taskIdTwo = taskSpawn("task2", MID, 0x100, 20000, (FUNCPTR)taskTwo, 0, 0,
                            0, 0, 0, 0, 0, 0, 0, 0)) == ERROR)
        printf("taskSpawn taskTwo failed\n");
   
    if ((taskIdThree = taskSpawn("task3", HIGH, 0x100, 20000, (FUNCPTR)taskThree,
                                0, 0, 0, 0, 0, 0, 0, 0, 0, 0)) == ERROR)
        printf("taskSpawn taskThree failed\n");
   
    if ((taskIdFour = taskSpawn("task4", HIGH, 0x100, 20000, (FUNCPTR)taskFour,
                                0, 0, 0, 0, 0, 0, 0, 0, 0, 0)) == ERROR)
        printf("taskSpawn taskFour failed\n");   
}

 

void taskOne(void)
{
    unsigned int i, j;
    for (i = 0; i < ITER1; i++)
    {
        /* log messages */
        for (j = 0; j < ITER2; j++)
            printf("task1\n");
   
        /* allow time for context switch */
        for (j = 0; j < LONG_TIME; j++)
            ;
    }
}

 

void taskTwo(void)
{
    unsigned int i, j;
    for (i = 0; i < ITER1; i++)
    {
        /* log messages */
        for (j = 0; j < ITER2; j++)
            printf("task2\n");
       
        /* allow time for context switch */
        for (j = 0; j < LONG_TIME; j++)
            ;
    }
}

 

void taskThree(void)
{
    unsigned int i, j;
    for (i = 0; i < ITER1; i++)
    {
        /* log messages */
        for (j = 0; j < ITER2; j++)
            printf("task3\n");
       
        /* allow time for context switch */
        for (j = 0; j < LONG_TIME; j++)
            ;
    }
}

 

void taskFour(void)
{
  taskDelay(TIMESLICE / 10);
  taskPrioritySet(taskIdOne, HIGH - 1);
}

  task4延迟100毫秒后，将task1的优先级设置到最高：在task2任务运行输出“task2”的过程中，task1抢占了task2的CPU资源，先是输出了所有的“task1”，最后剩余的“task2”得以输出。
  
   在VxWorks中，我们可以使用taskPrioritySet()函数来动态改变任务的优先级，这个函数的原型是：
STATUS taskPrioritySet (int tid, /* task ID */ int newPriority /* new priority */ );