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Reformated. Does FreeRTOS allow creation of Queues, Mutexes, and Semaphores within Critical Regions?

Posted by mikestitt on March 25, 2014

Sorry if this is posted twice. It did not seem like my first post was submitted correctly, so I'm trying to resubmit.

The FAQ: http://www.freertos.org/FAQHelp.html

States: "I get stuck on the line that starts for( pxIterator = ( ListItem_t * ) &( pxList->xListEnd );

Likely causes include: [...snip...] Calling an API function from within a critical section or when the RTOS scheduler is suspended."

Can this prohibition be clarified to limit calls to API functions which might run the scheduler within taskENTER_CRITICAL() regions? That is, allow API functions that don't run the scheduler?

To provide easy to use contracts between modules, I'd like to use lazy instantiation of communication mechanisms like this:

~~~~~~ :::c xQueueHandle getValidAppQueue(void) { static xQueueHandle appStateQueueHandle = 0; taskENTERCRITICAL(); if (!appStateQueueHandle) { appStateQueueHandle = xQueueCreate(1, sizeof( appStateQueueType)); } taskEXITCRITICAL(); return appStateQueueHandle; } ~~~~~~

But the FAQ implies that by calling XQueueCreate within a critical region, I'm violating the FreeRTOS API.



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