MQX Software SolutionsのトピックRe: Why the TCPIP_task has two argrument?

Why the TCPIP_task has two argrument?

JerryFan — Fri, 26 Apr 2013 08:45:47 GMT

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.

Re: Why the TCPIP_task has two argrument?

karelm_ — Tue, 30 Apr 2013 07:28:43 GMT

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.

Re: Why the TCPIP_task has two argrument?

JerryFan — Wed, 15 May 2013 02:52:14 GMT

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.