rxt51_tiny:why can not tasks switching?

code as following,and run on c8051f020.

unsigned char code cString1[]={"\nCommand: 1\0"};
unsigned char code cString2[]={"\nCommand: 2\0"};
unsigned char code cString3[]={"\nCommand: 3\0"};
unsigned char code cString4[]={"\nCommand: 4\0"};
unsigned char code cString5[]={"\nCommand: 5\0"};
unsigned char code cString6[]={"\nCommand: 6\0"};
unsigned char code cString7[]={"\nCommand: 7\0"};
unsigned char code cString8[]={"\nCommand: 8\0"};

/******************************************************************************/
/*        Task 0 'Initial_p': Initialize                                      */
/******************************************************************************/
void Initial_P (void) _task_ Initial_p
{  /* program execution starts here        */
    unsigned int iCount = 0;
    Initial();
    C8051ConfigBaud (96,0);                /* initialize the serial interface      */
    C8051ConfigBaud (192,1);
    Printf0 (cString1);
    os_create_task (SystemMan_p);             /* start clock task                     */
    os_create_task (Uart0Man_p);              /* start command task                   */
    os_create_task (Uart1Man_p);              /* start lights task                    */
    os_create_task (RecvData_p);              /* start keyread task                   */
    os_create_task (FlashMan_p);
    os_create_task (StaDisplay_p);
    os_create_task (TimeMan_p);
    os_delete_task (Initial_p);                /* stop init task (no longer needed)    */
}




/******************************************************************************/
/*        Task 1 'SystemMan_p': command processor */
/******************************************************************************/
void SystemMan_P (void) _task_ SystemMan_p
{
    while (1)
    {
        Printf0 (cString2);
        PRLED = 1;
        PRLED = 0;
                                os_wait (K_TMO, 2, 0);
    }
}
/******************************************************************************/
/*        Task 2 'SystemMan_p'                                                */
/******************************************************************************/
void Uart0Man_P (void)  _task_ Uart0Man_p  {
while (1)
    {
        Printf0 (cString3);
                                PGLED = 1;
                                PGLED = 0;
                                os_wait (K_TMO, 2, 0);
    }
}
/******************************************************************************/
/*        Task 3 'Uart1Man_p': runs if current time is outside start & end time */
/******************************************************************************/
void Uart1Man_P (void) _task_ Uart1Man_p  {
  while (1)
    {
        Printf0 (cString4);
                                RADRLED = 1;
                                RADRLED = 0;
                                os_wait (K_TMO, 2, 0);
    }
}

/******************************************************************************/
/*      Task 4 'RecvData_p': executes if current time is between start & end time */
/******************************************************************************/
void RecvData_P (void) _task_ RecvData_p
{
while (1)
    {
        Printf0 (cString5);
                                RADGLED = 1;
                                RADGLED = 0;
                os_wait (K_TMO, 2, 0);
    }
}


/******************************************************************************/
/*        Task 5 'FlashMan_p': process key stroke from pedestrian push button    */
/******************************************************************************/
void FlashMan_P (void) _task_ FlashMan_p  {

while (1)
    {
        Printf0 (cString6);
                                SRLED = 1 ;
                                SRLED =0 ;
                                os_wait (K_TMO, 2, 0);
    }
}

/******************************************************************************/
/*        Task 6 'StaDisplay_p': check if ESC (escape character) was entered    */
/******************************************************************************/
void StaDisplay_P (void) _task_ StaDisplay_p
{
while (1)
    {
        Printf0 (cString7);
                                SGLED = 1;
                                SGLED = 0;
                                os_wait (K_TMO, 2, 0);
    }
}

/******************************************************************************/
/*        Task 7 'TimeMan_p': check if ESC (escape character) was entered    */
/******************************************************************************/
void TimeMan_P (void) _task_ TimeMan_p  {
while (1)
    {
        Printf0 (cString8);
                                BLT_BLED = 1;
                                BLT_BLED = 0;
                                os_wait (K_TMO, 2, 0);
    }
}

why the result only print:
Command: 1
Command: 2
Command: 3
Command: 4
Command: 5
Command: 6
Command: 7
Command: 8
Command: 2
Command: 3
Command: 4