Hi, CPU: STM32F407, FreeRTOS V9.0.0, IDE: Eclipse Software came from CUBEMX I have a real time interrupt running outside of FreeRtos, it uses no system calls. It should run at a 1msec rate. I am using LWIP and when it makes a call to taskEnterCritical() my interrupt stops firing. I have set the priority of the interrupt to 0 (Highest). The configLIBRARYMAXSYSCALLINTERRUPTPRIORITY is set to 5 in FreeRTOSconfig.h So I would think that when the critical section is entered that all interrupts with a priority setting >=5 would be disabled but that my real time interrupt would be allowed to run. In tracing this down this is definately the spot where the interrupt stops getting serviced and what is worse is that since the EnterTaskCritical is nesting my interrupt does not get serviced until the last ExitTaskCritical is called which blocks me out for about 120msec which my application can’t stand. I know it’s not supposed to work this way but I have yet to be able to figure out what the issue is. Any suggestions?

Can you post how lwIP is implementing taskEnterCritical(). It should call the FreeRTOS taskENTERCRITICAL(), which will mask interrupts up to configMAXSYSCALLINTERRUPTPRIORITY only. If it is instead just globally disabling interrupts in the core, rather than the NVIC, then that would be the cause of you problem.

Richard, The LWIP function is LOCKTCPIPCORE which calls sysmutexlock which calls osMutexWait which calls xSemaphoreTake which calls xQueueGenericReceive which calls taskEnterCritical which calls the Assembly code in portDisableInterrupts which is defiend as vRaiseBasePri which sets the basePri register. I have no visibility what it is stuffing in there as I have not figured out where the values are comong from, the inline ASM is mov #0,#1 mov basepri,#0

My bad – the issue I have been fighting for the last 2 days was not a code issue at all, it was due to semihosting and the jtag programmer. Once I disabled all semihosting messaging it works flawlessly. File that away in your synapsis for future reference.

Thanks for taking the time to report back.