FreeRTOS V9.0.0 stm32f411 I am getting a hardfault after a while of calling the following simplified code within an ISR. Am I getting the settings wrong in the config settings for ISR priorities? or am I calling the FROMISR API incorrectly? the ISR: ~~~ void ISRCallback() BaseTypet xHigherPriorityTaskWoken = pdFALSE; for (int i = 0; i < NUMOFACTIVEOBJECTS; i++) {
if (EventSubscribers[evtId][i]) {
xQueueSendToBackFromISR(AEAO::AllAO[i]->queueExecuteForEvt, &AddingsubscriberArgs->Arg4, &xHigherPriorityTaskWoken); } } if( xHigherPriorityTaskWoken ) { /* Actual macro used here is port specific. */ portYIELDFROM_ISR (xHigherPriorityTaskWoken); } ~~~ it is sending an object to one or more queues. After this ISRcallback is executed exactly 31 times, a hardfault occurs at this line of code in the timers.c file at line 618 hardfault location: ~~~ if( xTaskResumeAll() == pdFALSE ) { /* Yield to wait for either a command to arrive, or the block time to expire. If a command arrived between the critical section being exited and this yield then the yield will not cause the task to block. */ portYIELD_WITHIN_API(); } ~~~ It must be something to do with the way I am calling the xQueueSendToBackFromISR API because when I remove all mentions of this, the hardfault does not happen anymore. here are the relevant settings I have for the NVIC: ~~~ NVICSetPriorityGrouping(NVICPRIORITYGROUP_4); ~~~ for the ISR: ~~~ HALNVICSetPriority(USART2IRQn, 5, 0); HALNVICEnableIRQ(USART2IRQn); ~~~ for the tasks that the queues the isr sends to : PRIORITY 10 for the freertosconfig: ~~~

define configMAX_PRIORITIES ( 16 )

define configUSE_TIMERS 1

define configTIMERTASKPRIORITY ( configMAX_PRIORITIES – 1 )

#define configPRIO_BITS 4

define configLIBRARYLOWESTINTERRUPT_PRIORITY 15

define configLIBRARYMAXSYSCALLINTERRUPTPRIORITY 5

define configKERNELINTERRUPTPRIORITY ( configLIBRARYLOWESTINTERRUPTPRIORITY << (8 – configPRIOBITS) )

/* !!!! configMAXSYSCALLINTERRUPT_PRIORITY must not be set to zero !!!! See http://www.FreeRTOS.org/RTOS-Cortex-M3-M4.html. */

define configMAXSYSCALLINTERRUPTPRIORITY ( configLIBRARYMAXSYSCALLINTERRUPTPRIORITY << (8 – configPRIOBITS) )

~~~

Nothing obviously wrong on a first read. Not relevant to the issue you are facing but there is no need to test xHigherPriorityTaskWoken before passing it to portYIELDFROMISR() as the test is performed inside the macro. Have you tried the normal things, like checking for stack overflows, etc.? https://www.freertos.org/FAQHelp.html I suspect so given the information you provided in your post….in which case try updating the source files in the FreeRTOS/Source directory to the latest version from SourceForge as that contains a lot more configASSERT() statements designed to try and catch misconfigurations in the Cortex-M priorities.

Thanks for the response. I found the problem. It was a stack overflow on one of the stacks that I had thought I removed from a while ago.
Is there a better way to check for stack overflows other than using uxTaskGetStackHighWaterMark. The way I had been doing it from before is just sprinking in uxTaskGetStackHighWaterMark across tasks I wanted to check, However as you saw, that is error prone.

There is a configCHECKFORSTACK_OVERFLOW which will check the stack of the task that is being swapped out for overflow.