Hi there, I work with a freeRTOS system that runs on a STM H7, generated with Cubemx. I would like to release a semaphore (in User code Tload_Timer_IrqProcess) from the “TIM1 update interrupt”, i.e. the freeRTOS heart: /** * @brief This function handles TIM1 update interrupt. */ void TIM1_UP_…

How did you release the semaphore from within an ISR? Did you use the FromISR variant, like xSemaphoreGiveFromISR()? There are some useful comments in semphr.h, and on freertos.org , of course. Please also read these comments . There have been many posts about this subject.

@htibosch : yes @aggarg : I don`t want to change the realtime priority of the freertos heart Isn’t there a way to service a semaphore from a high priority interrupt?

well you MUST not call a FreeRTOS API fn from an ISR above max sys call, it will not work. The only option you have is to raise MAX SYSCALL to include pri 0.

@RAc : Yes, I already know that this does not work, but it works when I comment out the “tASSERT_IF_INTERRUPT_PRIORITY_INVALID();” in queue.c. You can`t raise LIBRARY_MAX_SYSCALL_INTERRUPT_PRIORITY to 0, cubemx limits this to 1…6

Actually, it only appears to work, but you can be sure to experience random and unpredictable crashes. The critical section shield is vital to ensure coherency of the system data structures.

Yes RAc, thats the reason why I`m asking here …

And what I also don’t like is when I change LIBRARY_MAX_SYSCALL_INTERRUPT_PRIORITY in cubemx, then a lot of interrupts are suddenly shifted to 1, I couldn’t be responsible for the effects. I just want to free up a semaphore and not launch a major attack on the system…

Just don’t do it (freeing a semaphore) this way as it’s not possible. Free it somewhere else in task context if you really, really want to do it (why ?). For me it seems odd to even think of doing potentially lengthy resource management in an ISR (callback) besides the fact that an ISR is a very re…

@recently : Please do not confuse Cube MX restrictions and FreeRTOS restrictions. You should ask in the partner forum about the Cube quirks…

Is there any way to free a semaphore from a priority 0 interrupt?

Kernel

aggarg (Gaurav Aggarwal) March 17, 2022, 9:40am 3

Can you not change the priority of this interrupt? See here for explanation - Understanding priority levels of ISR and FreeRTOS APIs - #16 by aggarg

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Is there any way to free a semaphore from a priority 0 interrupt?

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