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Why do critical resource freeing in IDLE task

Posted by Engin AYDOGAN on June 16, 2008
It looks like very critical resource freeing is done in the idle task. Which is for instance, freeing the resources of a task which is deleted. I, naively, think that the resource freeing should have been done in the vTaskDelete instead. Probably it has been chosen to be this because of making the task deletion more deterministic but it makes a very undeterministic resource freeing.

i.e. I needed to stop a task and start another one. But it sometimes succeeds and sometimes fails. I've added `prvCheckTasksWaitingTermination();' in `vTaskDelete()' and it looks like working now.

I wonder what were the design choices you've made when putting resource freeing in idle task ?

Kind regards,

Engin

RE: Why do critical resource freeing in IDLE task

Posted by Richard on June 16, 2008
Two reasons:

1) Freeing memory can be time consuming.
2) A task cannot delete the memory it is itself using, this has to happen after the task has been prevented from ever running again otherwise if it got switched back in it would cause big issues.

There are of course other ways of doing this. The memory could be freed from within a critical section within the task itself for example, but this could prove to be a lengthy critical section depending on the implementation of free().

There are some other threads on this site regarding this, I think these give some work arounds for you.

Regards.


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