#16 Task specific callback for resource cleanup.

[Stefano Oliveri]

The idea is to extend the semantic of the vTaskDelete function in order to give a task a change to release task specific resource before it is deleted.

A task can use an API function like the following to notify the kernel about its callback:

vTaskSetCallback(Event callbackType, xTaskHandle task, func *pCallback)

callbackType - specifies the callback is setting (to be used for further extension).

task - specifies the task identifier.

pCallback - specifies the pointer to some defined function type.

[Stefano Oliveri]

Sequence Diagram

[Stefano Oliveri]

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Regards,
Stefano

[Hein Tibosch]

Although this is a very old proposal, I'd like to respond to it.

The biggest problem with the proposed solution is that the function pointed to by pCallback will be called ( executed ) from either a different task or worse, from the idle task. Note that no guarantees can be given about the available stack space, the current task priority, or task specific privileges.

When task-A terminates, its termination code should be better executed from the task-A context. This means that also vTaskDelete() will be called by task to be deleted.

So why not send a message to task-A that says "please terminate"? The task can first finish any important action, release mutexes / resources, and then call its own termination code. The final thing to do is call vTaskDelete().

void vMyTask( void * pvParameter )
{
    while( !has_to_stop )
    {
        /* Do the work. */
    }
    my_exit_code();

    vTaskDelete( NULL );
}

For C++ users: this solution also allows to declare objects that have destructors:

void vMyTask( void * pvParameter )
{
    {
        CClass some_object;

        while( !has_to_stop )
        {
            /* Do the work. */
        }
        /* CClass::~CClass (destructor) will be executed. */
    }
    my_exit_code();

    vTaskDelete( NULL );
}

As for this feature request: I recommend closing it after 13 years.