Semaphore in OS API

General
1

If you are asking a question, please follow this template:

  1. My goal is: [using Semaphore to protect FIFO]
  2. My actions are: [I have created FIFO in UART port which can be called in different tasks]
  3. The result I see is: [Want to use semaphore to protect the read/write access]
  4. My expectation & question is: [Does the OS has such API ??]
2

mOS is an event-driven framework, there are no threads, there is no preemption. You only need that if you work at the chip or the OS level; the System API has a recursive lock but that is all I know.
BTW, the UARTs already have FIFOs, you can check the code for your particular platform to see how the developers handled it.