Why the TCPIP_task has two argrument?

[JerryFan]

I am reading RTCS code(MQX4.0), and confused that TCPIP_task has two argrument.

In the rtcs\source\tcpip\tcpip.c:

void TCPIP_task

(

     pointer dummy,

     pointer creatro

)

while all other task, such as shell task has only one argrument.

[karelm_]

Hi,

This is because TCP/IP task is created by calling function RTCS_task_create() instead of standard MQX _task_create(). RTCS_task_create has following prototype:

extern uint_32 RTCS_task_create

(

   char_ptr          name,

   uint_32           priority,

   uint_32           stacksize,

   void (_CODE_PTR_  start)(pointer, pointer),

   pointer           arg

);

As you can see every task created by this function must have two parameters (task parameter and creator). However the TCP/IP task require no parameter so it is called 'dummy' in its definition.

[JerryFan]

Thanks a lot, Karel.

After going through the code, I wanna try to summurize this:

1.   RTCS_task_create created the task RTCS_task, and take a local variable "&task" as parameter, then wait the task.sem be posted.

{

     ......

   struct rtcs_task_state  task;

   RTCS_sem_init(&task.sem);

   task.start = start;

   task.arg   = arg;

   task.error = RTCS_OK;

   ...

   task_template.TASK_ADDRESS       = RTCS_task;

   task_template.CREATION_PARAMETER = (uint_32)&task;

   if (_task_create(0, 0, (uint_32)&task_template) == MQX_NULL_TASK_ID) {

     ...

   } /* Endif */

   RTCS_sem_wait(&task.sem);

   RTCS_sem_destroy(&task.sem);

   return task.error;

} /* Endbody */

2. RTCS_task run and call task->start(task->arg, task), ie, TCPIP_task(task->arg, task). The "task" here point to "struct rtcs_task_state  task" within  RTCS_task_create's stack.

3. TCPIP_task runs and post task.sem and continue running

4. RTCS_task_create return.

So the "creator"  just a local variable of the creator.