Does HAL_UART_Transmit/HAL_UART_Receive needs a semaphore?

[ubaldot]

Say that HAL_UART_Transmit function is concurrently called by two tasks.

So far, I know such a function is blocking, but I am not 100% sure that because of that it shall not be locked before usage if a concurrent task is going to call it.  

[TDK · Accepted solution]

Yes, it needs an exclusive access mechanism.

At best, the second call will fail and return HAL_BUSY. At worst, it will mess up the software state machine as __HAL_LOCK is not thread-safe.

[ubaldot]

Thanks. I will lock it with a mutexat OS level then.