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

Kernel
1

My code is as follows:

taskENTER_CRITICAL();
xSemaphoreTake(Semaphore)；
……
xSemaphoreGive(Semaphore)；
taskEXIT_CRITICAL();

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

2

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.

3

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.

4

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