实例：优先级反转 - 曲径通幽论坛

#include "includes.h"



#define TASK_STK_SIZE                 512

  OS_STK    StartTaskStk[TASK_STK_SIZE];
  OS_STK        MyTaskStk[TASK_STK_SIZE];        /* Tasks stacks                                  */
  OS_STK    YouTaskStk[TASK_STK_SIZE];
  OS_STK    HerTaskStk[TASK_STK_SIZE];

  INT16S key;
  char *s1 = "MyTask is running";
  char *s2 = "YouTask is running";
  char *s3 = "HerTask is running";
  char *ss = "Mytask require the semaphore";

  INT8U   err;
  INT8U   y = 0;
  INT32U   times = 0;
  OS_EVENT *Semp;

void StartTask(void *data);
void MyTask(void *data);                  /* Function prototypes of Startup task           */
void YouTask(void *data);
void HerTask(void *data);

void main (void)
{

PC_DispClrScr(DISP_FGND_WHITE + DISP_BGND_BLACK);      /* Clear the screen                         */

OSInit();                                              /* Initialize uC/OS-II                      */
    PC_DOSSaveReturn();                                    /* Save environment to return to DOS        */
PC_VectSet(uCOS, OSCtxSw);                             /* Install uC/OS-II's context switch vector */
Semp = OSSemCreate(1);

OSTaskCreate(StartTask, (void *)0, &StartTaskStk[TASK_STK_SIZE - 1], 0);
OSStart();                                             /* Start multitasking                       */
}

void StartTask(void *pdata)
{
#if OS_CRITICAL_METHOD == 3                                /* Allocate storage for CPU status register */
OS_CPU_SR cpu_sr;
#endif

pdata = pdata;                                         /* Prevent compiler warning                 */

OS_ENTER_CRITICAL();
PC_VectSet(0x08, OSTickISR);                           /* Install uC/OS-II's clock tick ISR        */
PC_SetTickRate(OS_TICKS_PER_SEC);                      /* Reprogram tick rate                      */
OS_EXIT_CRITICAL();

OSStatInit();                                          /* Initialize uC/OS-II's statistics         */

OSTaskCreate(MyTask,(void *)0, &MyTaskStk[TASK_STK_SIZE - 1], 3);

OSTaskCreate(YouTask,(void *)0, &YouTaskStk[TASK_STK_SIZE - 1], 4);

OSTaskCreate(HerTask,(void *)0, &HerTaskStk[TASK_STK_SIZE - 1], 5);

for(;;)
{

if( PC_GetKey(&key) == TRUE )
{
   if( key == 0x1B )
   {
    PC_DOSReturn();
    }

}
     OSTimeDlyHMSM(0,0,3,0);
  }

}
void MyTask (void *pdata)
{
#if OS_CRITICAL_METHOD == 3                                /* Allocate storage for CPU status register */
OS_CPU_SR cpu_sr;
#endif

pdata = pdata;                                         /* Prevent compiler warning                 */

for (;;)
   {

OSTimeDlyHMSM(0,0,0,200);

    PC_DispStr(10,++y,ss,DISP_BGND_BLACK + DISP_FGND_WHITE);

   OSSemPend(Semp,0,&err);

    PC_DispStr(10,++y,s1,DISP_BGND_BLACK + DISP_FGND_WHITE);

   OSSemPost(Semp);

OSTimeDlyHMSM(0,0,0,200);

   }

}

void YouTask(void *pdata)
{
#if OS_CRITICAL_METHOD == 3                                /* Allocate storage for CPU status register */
OS_CPU_SR cpu_sr;
#endif

pdata = pdata;

for (;;)
   {
    PC_DispStr(10,++y,s2,DISP_BGND_BLACK + DISP_FGND_WHITE);

   OSTimeDlyHMSM(0,0,0,300);
}

}

void HerTask( void *pdata )
{
#if OS_CRITICAL_METHOD == 3
OS_CPU_SR cpu_sr;
#endif

  pdata = pdata;

  for(;;)
  {
   OSSemPend( Semp,0,&err);

    PC_DispStr(10,++y,s3,DISP_BGND_BLACK + DISP_FGND_WHITE);

   for( times; times<20000000; times++ )
   {
    OS_Sched();
   }

   OSSemPost( Semp );

   OSTimeDlyHMSM(0,0,1,0);
  }

}