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xQueueReceive stops working suddenly during operation

Posted by hristozov on June 30, 2016

Hi, I am using STM32F4 with freeRTOSv8.0.1. IDE is coocox. I have a task that blocks on a queue

xQueueReceive( QueueBtPkg, &bt_pkg_ptr, portMAX_DELAY);

and three higher priority tasks that puts data on the queue. When one of this task puts something on the queue, the queue unlocks it task and everything is OK. This works for between few minutes and a couple of hours, then the xQueueReceive stops unlocking it task and becomes full.

My first thought was that this is classic case of task starvation. The task where the queue is never executes because the other three higher priority tasks always run. In order to check this I created a dummy task

~~~ void taskdebug(void * pvParameters) { while (1) { if (debugmessagecntEEG[debugiEEG] > 10) { asm("nop"); } } } ~~~

and put break point on the asm("nop"). This task has the lowest priority. It priority is lower then the task with the queue. In the if statement I check a value updated by the three sending tasks. This value is returned by uxQueueMessagesWaiting(QueueBtPkg).

debug_message_cnt_EEG[debug_i_EEG] = uxQueueMessagesWaiting(QueueBtPkg);

Now I see that the program stops at the break point at asm("nop"). This means that the queue is not empty but doesn't unlock the it task. Because the dummy task also has the lowest priority and it is unlocked there is no task starvation.

Anny ideas, what can cause this?


xQueueReceive stops working suddenly during operation

Posted by edwards3 on June 30, 2016

do you have configASSERT() implemented? http://www.freertos.org/FAQHelp.html http://www.freertos.org/RTOS-Cortex-M3-M4.html


xQueueReceive stops working suddenly during operation

Posted by hristozov on July 1, 2016

Yes


xQueueReceive stops working suddenly during operation

Posted by rtel on July 1, 2016

You have one task that is draining the queue. When the queue becomes full, what is this task doing? Is it still blocked on the queue, or is it not blocked on the queue any more?


xQueueReceive stops working suddenly during operation

Posted by hristozov on July 1, 2016

Is it still blocked on the queue


xQueueReceive stops working suddenly during operation

Posted by rtel on July 1, 2016

How have you determined that? For example, are you examining the data structures internally (requires some expert knowledge), viewing the system status on a debugger plug-in, adding in your own debug code (for example setting a pin on the way into the queue receive function and clearing the pin on the way out), or something else?


xQueueReceive stops working suddenly during operation

Posted by hristozov on July 1, 2016

I am using a dummy task with lower priority then the priority of the task blocking on the queue, please my first post.

Can you point me to documentation on how to examine the data structure internally.


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