FreeRTOS pvPortMalloc eror un ISR

Posted by jcc18 on December 1, 2016

Hi I have problem with prvMalloc when I used in ISR. I used a FreeRTOS 8.2.3 for microblaze.

I need reserve memory in ISR but I call a prvMalloc the program stack It corrupts. I debug a prvMalloc, the stack is corrupt after running xTaskResumeAll:

https://postimg.org/image/cruh4v02n/ Good stck https://postimg.org/image/7rsfj6527/ Back Stack

In xTaskResumeAll the stack corrupt in taskEXIT_CRITICAL because the interrupt are enable:

https://postimg.org/image/mdo1l5r8f/

http://https://postimg.org/image/djx54249r/ Error in InterruptEnable

How i reserve memory in ISR???

Thanks Regard

Sorry my english is very bad 🙁


FreeRTOS pvPortMalloc eror un ISR

Posted by richard_damon on December 1, 2016

The Heap Functions for FreeRTOS are not ISR safe, because they do not turn off the interupts for the full period they need to protect the heap (as that is likely much too long for many applications).

Allocating heap memory in an ISR is generally a bad idea, as the timing characteristics for a general heap are not good for an ISR (somewhat slow and unpredictable). Generally, it is best to pre-allocate the memory the ISR might need, and have it use that.

If you really need to use the heap in the ISR, then you will need to make your own version of the malloc wrapper which guards itself with a critical section (disable interrupts), and a second wrapper, as a xxxFromISR which has any needed ISR wraping (depends if the Microblaze port supports interrupt nesting). Note, this will cause a significant increase in worse case interrupt latency, which may be hard to detect, as it will be intermittent.