请教多任务调度的问题

ChinaLingBo

请教多任务调度的问题 [复制链接]

以下是我找的一个ucos-ii的一个应用例子，现在想问的是main（）中调用OSTaskCreateExt（）创建了TaskStart（）任务后，通过调用OSStart（）运行TaskStart（）任务，在TaskStart（）中运行到for（；；）之后进入死循环，之后的任务调用是如何进行的呢？请各位高手不吝赐教！！！！！拜谢！！！！

/*
*********************************************************************************************************
*                                                uC/OS-II
*                                          The Real-Time Kernel
*
*                           (c) Copyright 1992-1999, Jean J. Labrosse, Weston, FL
*                                           All Rights Reserved
*
*                                                 V2.00
*
*                                               EXAMPLE #2
*********************************************************************************************************
*/

#include "includes.h"

/*
*********************************************************************************************************
*                                              CONSTANTS
*********************************************************************************************************
*/

#define          TASK_STK_SIZE     512                /* Size of each task's stacks (# of WORDs)       */

#define          TASK_START_ID       0                /* Application tasks IDs                         */
#define          TASK_CLK_ID         1
#define          TASK_1_ID           2
#define          TASK_2_ID           3
#define          TASK_3_ID           4
#define          TASK_4_ID           5
#define          TASK_5_ID           6

#define          TASK_START_PRIO    10                /* Application tasks priorities                  */
#define          TASK_CLK_PRIO      11
#define          TASK_1_PRIO        12
#define          TASK_2_PRIO        13
#define          TASK_3_PRIO        14
#define          TASK_4_PRIO        15
#define          TASK_5_PRIO        16

/*
*********************************************************************************************************
*                                              VARIABLES
*********************************************************************************************************
*/

OS_STK           TaskStartStk[TASK_STK_SIZE];         /* Startup    task stack                         */
OS_STK           TaskClkStk[TASK_STK_SIZE];           /* Clock      task stack                         */
OS_STK           Task1Stk[TASK_STK_SIZE];             /* Task #1    task stack                         */
OS_STK           Task2Stk[TASK_STK_SIZE];             /* Task #2    task stack                         */
OS_STK           Task3Stk[TASK_STK_SIZE];             /* Task #3    task stack                         */
OS_STK           Task4Stk[TASK_STK_SIZE];             /* Task #4    task stack                         */
OS_STK           Task5Stk[TASK_STK_SIZE];             /* Task #5    task stack                         */

OS_EVENT        *AckMbox;                             /* Message mailboxes for Tasks #4 and #5         */
OS_EVENT        *TxMbox;

INT16U           TaskFPUFlag;

/*
*********************************************************************************************************
*                                         FUNCTION PROTOTYPES
*********************************************************************************************************
*/

        void     TaskStart(void *data);               /* Function prototypes of tasks                  */
static  void     TaskStartCreateTasks(void);
        void     TaskClk(void *data);
        void     Task1(void *data);
        void     Task2(void *data);
        void     Task3(void *data);
        void     Task4(void *data);
        void     Task5(void *data);

/*$PAGE*/
/*
*********************************************************************************************************
*                                                  MAIN
*********************************************************************************************************
*/

void main (void)
{
    OS_STK *ptos;
    OS_STK *pbos;
    INT32U  size;

    PC_DispClrScr(DISP_FGND_WHITE);                        /* 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 */

    PC_ElapsedInit();                                      /* Initialized elapsed time measurement     */

    TaskFPUFlag = _8087;

    ptos        = &TaskStartStk[TASK_STK_SIZE - 1];
    pbos        = &TaskStartStk[0];
    size        = TASK_STK_SIZE;
    OSTaskStkInit_FPE_x86(&ptos, &pbos, &size);            /* TaskStart() will use Floating-Point      */
    OSTaskCreateExt(TaskStart,
                   (void *)0,
                   ptos,
                   TASK_START_PRIO,
                   TASK_START_ID,
                   pbos,
                   size,
                   (void *)0,
                   OS_TASK_OPT_STK_CHK | OS_TASK_OPT_STK_CLR);

    OSStart();                                             /* Start multitasking                       */
}
/*$PAGE*/

ChinaLingBo

/*
*********************************************************************************************************
*                                               STARTUP TASK
*********************************************************************************************************
*/

void  TaskStart (void *data)
{
#if OS_CRITICAL_METHOD == 3                      /* Allocate storage for CPU status register           */
    OS_CPU_SR  cpu_sr;
#endif
    char       s[80];
    INT16S     key;


    data = data;                                           /* Prevent compiler warning                 */

    PC_DispStr(26,  0, "uC/OS-II, The Real-Time Kernel", DISP_FGND_WHITE + DISP_BGND_RED + DISP_BLINK);
    PC_DispStr(33,  1, "Jean J. Labrosse", DISP_FGND_WHITE);
    PC_DispStr(36,  3, "EXAMPLE #2", DISP_FGND_WHITE);
    PC_DispStr( 0,  9, "Task           Total Stack  Free Stack  Used Stack  ExecTime (uS)", DISP_FGND_WHITE);
    PC_DispStr( 0, 10, "-------------  -----------  ----------  ----------  -------------", DISP_FGND_WHITE);
    PC_DispStr( 0, 12, "TaskStart():", DISP_FGND_WHITE);
    PC_DispStr( 0, 13, "TaskClk()  :", DISP_FGND_WHITE);
    PC_DispStr( 0, 14, "Task1()    :", DISP_FGND_WHITE);
    PC_DispStr( 0, 15, "Task2()    :", DISP_FGND_WHITE);
    PC_DispStr( 0, 16, "Task3()    :", DISP_FGND_WHITE);
    PC_DispStr( 0, 17, "Task4()    :", DISP_FGND_WHITE);
    PC_DispStr( 0, 18, "Task5()    :", DISP_FGND_WHITE);
    PC_DispStr(28, 24, "<-PRESS 'ESC' TO QUIT->", DISP_FGND_WHITE + DISP_BLINK);

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

    PC_DispStr(0, 22, "Determining  CPU's capacity ...", DISP_FGND_WHITE);
    OSStatInit();                                          /* Initialize uC/OS-II's statistics         */
    PC_DispClrRow(22, DISP_FGND_WHITE + DISP_BGND_BLACK);

    AckMbox = OSMboxCreate((void *)0);                     /* Create 2 message mailboxes               */
    TxMbox  = OSMboxCreate((void *)0);

    TaskStartCreateTasks();                                /* Create all other tasks                   */

    PC_DispStr( 0, 22, "#Tasks          : xxxxx  CPU Usage: xxx %", DISP_FGND_WHITE);
    PC_DispStr( 0, 23, "#Task switch/sec: xxxxx", DISP_FGND_WHITE);

    for (;;) {
        sprintf(s, "%5d", OSTaskCtr);                     /* Display #tasks running                    */
        PC_DispStr(18, 22, s, DISP_FGND_BLUE + DISP_BGND_CYAN);
        sprintf(s, "%3d", OSCPUUsage);                    /* Display CPU usage in %                    */
        PC_DispStr(36, 22, s, DISP_FGND_BLUE + DISP_BGND_CYAN);
        sprintf(s, "%5d", OSCtxSwCtr);                    /* Display #context switches per second      */
        PC_DispStr(18, 23, s, DISP_FGND_BLUE + DISP_BGND_CYAN);

        OSCtxSwCtr = 0;                                    /* Clear context switch counter             */

        sprintf(s, "V%3.2f", OSVersion() * 0.01);
        PC_DispStr(75, 24, s, DISP_FGND_YELLOW + DISP_BGND_BLUE);

        switch (TaskFPUFlag) {
            case 0:
                 PC_DispStr(71, 22, " NO  FPU ", DISP_FGND_BLUE + DISP_BGND_CYAN);
                 break;

            case 1:
                 PC_DispStr(71, 22, " 8087 FPU", DISP_FGND_BLUE + DISP_BGND_CYAN);
                 break;

            case 2:
                 PC_DispStr(71, 22, "80287 FPU", DISP_FGND_BLUE + DISP_BGND_CYAN);
                 break;

            case 3:
                 PC_DispStr(71, 22, "80387 FPU", DISP_FGND_BLUE + DISP_BGND_CYAN);
                 break;
        }

        if (PC_GetKey(&key)) {                             /* See if key has been pressed              */
            if (key == 0x1B) {                             /* Yes, see if it's the ESCAPE key          */
                PC_DOSReturn();                            /* Yes, return to DOS                       */
            }
        }

        OSTimeDly(OS_TICKS_PER_SEC);                       /* Wait one second                          */
    }
}
/*$PAGE*/

ChinaLingBo

/*
*********************************************************************************************************
*                                             CREATE TASKS
*********************************************************************************************************
*/

static  void  TaskStartCreateTasks (void)
{
    OSTaskCreateExt(TaskClk,
                   (void *)0,
                   &TaskClkStk[TASK_STK_SIZE - 1],
                   TASK_CLK_PRIO,
                   TASK_CLK_ID,
                   &TaskClkStk[0],
                   TASK_STK_SIZE,
                   (void *)0,
                   OS_TASK_OPT_STK_CHK | OS_TASK_OPT_STK_CLR);

    OSTaskCreateExt(Task1,
                   (void *)0,
                   &Task1Stk[TASK_STK_SIZE - 1],
                   TASK_1_PRIO,
                   TASK_1_ID,
                   &Task1Stk[0],
                   TASK_STK_SIZE,
                   (void *)0,
                   OS_TASK_OPT_STK_CHK | OS_TASK_OPT_STK_CLR);

    OSTaskCreateExt(Task2,
                   (void *)0,
                   &Task2Stk[TASK_STK_SIZE - 1],
                   TASK_2_PRIO,
                   TASK_2_ID,
                   &Task2Stk[0],
                   TASK_STK_SIZE,
                   (void *)0,
                   OS_TASK_OPT_STK_CHK | OS_TASK_OPT_STK_CLR);

    OSTaskCreateExt(Task3,
                   (void *)0,
                   &Task3Stk[TASK_STK_SIZE - 1],
                   TASK_3_PRIO,
                   TASK_3_ID,
                   &Task3Stk[0],
                   TASK_STK_SIZE,
                   (void *)0,
                   OS_TASK_OPT_STK_CHK | OS_TASK_OPT_STK_CLR);

    OSTaskCreateExt(Task4,
                   (void *)0,
                   &Task4Stk[TASK_STK_SIZE-1],
                   TASK_4_PRIO,
                   TASK_4_ID,
                   &Task4Stk[0],
                   TASK_STK_SIZE,
                   (void *)0,
                   OS_TASK_OPT_STK_CHK | OS_TASK_OPT_STK_CLR);

    OSTaskCreateExt(Task5,
                   (void *)0,
                   &Task5Stk[TASK_STK_SIZE-1],
                   TASK_5_PRIO,
                   TASK_5_ID,
                   &Task5Stk[0],
                   TASK_STK_SIZE,
                   (void *)0,
                   OS_TASK_OPT_STK_CHK | OS_TASK_OPT_STK_CLR);
}

/*$PAGE*/
/*
*********************************************************************************************************
*                                               TASK #1
*
* Description: This task executes every 100 mS and measures the time it task to perform stack checking
*              for each of the 5 application tasks.  Also, this task displays the statistics related to
*              each task's stack usage.
*********************************************************************************************************
*/

void  Task1 (void *pdata)
{
    INT8U       err;
    OS_STK_DATA data;                       /* Storage for task stack data                             */
    INT16U      time;                       /* Execution time (in uS)                                  */
    INT8U       i;
    char        s[80];

    pdata = pdata;
    for (;;) {
        for (i = 0; i < 7; i++) {
            PC_ElapsedStart();
            err  = OSTaskStkChk(TASK_START_PRIO+i, &data);
            time = PC_ElapsedStop();
            if (err == OS_NO_ERR) {
                sprintf(s, "%4ld        %4ld        %4ld        %6d",
                        data.OSFree + data.OSUsed,
                        data.OSFree,
                        data.OSUsed,
                        time);
                PC_DispStr(19, 12+i, s, DISP_FGND_YELLOW);
            }
        }
        OSTimeDlyHMSM(0, 0, 0, 100);                       /* Delay for 100 mS                         */
    }
}
/*$PAGE*/
/*
*********************************************************************************************************
*                                               TASK #2
*
* Description: This task displays a clockwise rotating wheel on the screen.
*********************************************************************************************************
*/

void  Task2 (void *data)
{
    data = data;
    for (;;) {
        PC_DispChar(70, 15, '|',  DISP_FGND_WHITE + DISP_BGND_RED);
        OSTimeDly(10);
        PC_DispChar(70, 15, '/',  DISP_FGND_WHITE + DISP_BGND_RED);
        OSTimeDly(10);
        PC_DispChar(70, 15, '-',  DISP_FGND_WHITE + DISP_BGND_RED);
        OSTimeDly(10);
        PC_DispChar(70, 15, '\\', DISP_FGND_WHITE + DISP_BGND_RED);
        OSTimeDly(10);
    }
}
/*$PAGE*/
/*
*********************************************************************************************************
*                                               TASK #3
*
* Description: This task displays a counter-clockwise rotating wheel on the screen.
*
* Note(s)    : I allocated 100 bytes of storage on the stack to artificially 'eat' up stack space.
*********************************************************************************************************
*/

void  Task3 (void *data)
{
    char    dummy[500];
    INT16U  i;

    data = data;
    for (i = 0; i < 499; i++) {        /* Use up the stack with 'junk'                                 */
        dummy = '?';
    }
    for (;;) {
        PC_DispChar(70, 16, '|',  DISP_FGND_WHITE + DISP_BGND_BLUE);
        OSTimeDly(20);
        PC_DispChar(70, 16, '\\', DISP_FGND_WHITE + DISP_BGND_BLUE);
        OSTimeDly(20);
        PC_DispChar(70, 16, '-',  DISP_FGND_WHITE + DISP_BGND_BLUE);
        OSTimeDly(20);
        PC_DispChar(70, 16, '/',  DISP_FGND_WHITE + DISP_BGND_BLUE);
        OSTimeDly(20);
    }
}
/*$PAGE*/
/*
*********************************************************************************************************
*                                               TASK #4
*
* Description: This task sends a message to Task #5.  The message consist of a character that needs to
*              be displayed by Task #5.  This task then waits for an acknowledgement from Task #5
*              indicating that the message has been displayed.
*********************************************************************************************************
*/

void  Task4 (void *data)
{
    char   txmsg;                                                     /*这儿为什么用char来定义数据类型呢？*/
    INT8U  err;

    data  = data;
    txmsg = 'A';
    for (;;) {
        while (txmsg <= 'Z') {
            OSMboxPost(TxMbox, (void *)&txmsg);  /* Send message to Task #5                            */
            OSMboxPend(AckMbox, 0, &err);        /* Wait for acknowledgement from Task #5              */
            txmsg++;                             /* Next message to send                               */
        }
        txmsg = 'A';                             /* Start new series of messages                       */
    }
}
/*$PAGE*/

ChinaLingBo

/*
*********************************************************************************************************
*                                               TASK #5
*
* Description: This task displays messages sent by Task #4.  When the message is displayed, Task #5
*              acknowledges Task #4.
*********************************************************************************************************
*/

void  Task5 (void *data)
{
    char  *rxmsg;
    INT8U  err;

    data = data;
    for (;;) {
        rxmsg = (char *)OSMboxPend(TxMbox, 0, &err);                  /* Wait for message from Task #4 */
        PC_DispChar(70, 18, *rxmsg, DISP_FGND_YELLOW + DISP_BGND_RED);
        OSTimeDlyHMSM(0, 0, 1, 0);                                    /* Wait 1 second                 */
        OSMboxPost(AckMbox, (void *)1);                               /* Acknowledge reception of msg  */
    }
}
/*$PAGE*/
/*
*********************************************************************************************************
*                                               CLOCK TASK
*********************************************************************************************************
*/

void  TaskClk (void *data)
{
    char s[40];

    data = data;
    for (;;) {
        PC_GetDateTime(s);
        PC_DispStr(0, 24, s, DISP_FGND_BLUE + DISP_BGND_CYAN);
        OSTimeDly(OS_TICKS_PER_SEC);
    }
}

花开花谢

任务调度发生在时基或者中断退出时，当然，有的精简了中断退出时的调度，也就只有按时基调度

zzhere2007

任务的调度发生在 延时和每个节拍计时的中断 ，进入循环后，等待节拍中断，在进入任务

ChinaLingBo

谢谢，大概明白了一点，能说的再详细一些吗？

ChinaLingBo

太高深了，时基是个什么东东？初学者见笑了！