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Creating tasks after the scheduler is started

Posted by Richard on May 7, 2008
[moved from private email]

Is it possible when the scheduler is running to
create another task?
In all the demo's I can't find an example when the scheduler is running to
create more tasks.

For example:
- Normally:
First main -> Start Tasks -> Create those Tasks -> Start
Scheduler.
- What I want:
First main -> Start Tasks -> Create those Tasks -> Start
Scheduler -> Create Another Task when needed.

RE: Creating tasks after the scheduler is started

Posted by Richard on May 7, 2008
Yes - you can create and tasks after the scheduler has been started. You call xTaskCreate() in the normal way. The file FreeRTOS/Demo/Common/Minimal/death.c demonstrates this (the name comes from the fact that tasks are dynamically created then killed).

The thing to watch out for is memory fragmentation. When you create a task memory is allocated, when you delete a task it is freed, so doing this continuously can result in fragmentation problems. If the memory cannot be allocated then the task cannot be freed. If the tasks you create and delete all have the same stack size, and these are the only dynamically created/deleted objects then this might not be a problem.

Note that if you are using heap_1.c then memory cannot be re-allocated. See http://www.freertos.org/a00111.html for more information.

Regards.


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