FREERTOS: Binary-Semaphore initial state bug

[ak52]

Hello Experts,

i am facing a similar issue on the STM32F407G discovery board. Is there any solution or a temporary fix for this iisue?

https://community.st.com/t5/stm32cubemx-mcus/re-freertos-semaphore-not-initialised-correctly-by-cubemx/td-p/780252

 

Changing the initial state of the semaphore to Depleted does nothing in the semaphore definition and creation:

In freertos.c, inside the function MX_FREERTOS_Init(). i  think the second function parameter should be zero

 

I am trying a simple GPIO interrupt to task signaling, but the task always takes a semaphore without the GPIO interrupt the first time. I have attached the complete freertos.c file for context. This is the console screenshot to highlight the bug:

 

 

I tried to manually change:

myBinarySem01Handle = osSemaphoreCreate(osSemaphore(myBinarySem01), 1);

to

myBinarySem01Handle = osSemaphoreCreate(osSemaphore(myBinarySem01), 0);

Now the task does not take the semaphore during start up, but the moment the GPIO interrupt occurs(push-button), the whole system hangs in an asset failure:

Is there any solution to this problem? I have attached my freertos.c file as well.

[Pavel A.]

If the 2nd parameter is 0, osSemaphoreCreate likely returned NULL handle (myBinarySem01Handle ), this is why you assert in xQueueGiveFromISR. Please see the source in cmsis_os.c and you will understand.

 

[ak52]

Yes, thanks for pointing it out. Looking at osSemaphoreCreate  function i realized it was returning NULL.

This brings up the question how do we change the semaphores initial state to depleted/empty?

I also tried to use the native FreeRTOS APIs (xSemaphoreCreateBinary) which creates the semaphore in an 'empty' state, this worked for me, so i am pretty confident there is some issue in the cmsis implementation.

[Pavel A.]

Is config_USE_COUNTING_SEMAPHORES defined as 1 ?

Maybe, change osSemaphoreCreate  like following:

...........
 if (count == 1) {
 return xSemaphoreCreateBinaryStatic( semaphore_def->controlblock );
 }
 else if (count == 0) {
 sema = xSemaphoreCreateBinaryStatic( semaphore_def->controlblock );
 if (!sema) return sema;
 osSemaphoreWait(sema, 0); //immediately take it
 return sema;
 }
 else {
..........

 

[ak52]

Thanks , you solution worked. But i used it in a different way, I did not want to modify the HAL function as it overwrites every time there is a change in the .ioc file

So i did something like this:

osSemaphoreId bin_sem_id;
osSemaphoreDef(bin_sem);

bin_sem_id = osSemaphoreCreate(osSemaphore(bin_sem), 1);

if (bin_sem_id != NULL) 
{
 osSemaphoreWait(bin_sem_id, 0); // Take the semaphore immediately (no blocking)
 // Now the semaphore has a count of 0 and is unavailable.
} 
else 
{
 // Semaphore creation failed
}