receiving-uart in a task

Hi everybody,

I don't know if this question is yet resolved in this forum,but i try: I'm using ucosII,and a task that's waiting to receive character from uart (using scanf()...) but this task never release the control to the operating system,so i can't execute other task unless i use the lowest priority for the uart task.Is thi possible?Does not the HAL put the task sleeping waiting for a character?

thanks in advance