After taskENTER_CRITICAL(), I call xsemaphoretake. Why doesn't it crash?

My code is as follows:


I’m a little confused.
Isn’t it stipulated that FreeRTOS API can’t be called Between taskENTER_CRITICAL and taskEXIT_CRITICAL.?

Entering a critical section means that interrupts ( up to a certain priority ) are suppressed.
Now you call xSemaphoreTake() during a critical section: how can it block when interrupts are not allowed.

PS. Have you defined configASSERT() in a proper way ?

I would recommend to either use a semaphore, or a critical section, preferably the former.

  • A semaphore will stop other tasks from entering the protected section.
  • A critical section will stop other tasks and interrupts from executing.

Most API’s can not be called during a critical section.

The API can be called within a critical section, it just is not allowed for the code to actually block.

Note, xSemaphoreTask as an additional parameter, how long to block if the semaphore isn’t available, and returns a value, if it was successful.

You COULD have code that does a take with a 0 time to wait, and check if got the semaphore, and if it did, do some actions and then give the semaphore back.

Also, you can have logic or scheduling policy breaches in the code without the code crashing.