Semaphores: Mutual Exclusion (revisited)

Thread A and thread B must obey the protocol: wait for the unit from the semaphore before using the shared resource (buffer) and release the unit after completion.

char cShared[10];

RTHANDLE hSema4;

// do this once:

hSema4 = CreateRtSemaphore (1, 1, FIFO_QUEUEING);

// do this for every access to cShared:

wRem = WaitForRtSemaphore (hSema4, 1, WAIT_FOREVER);

// manipulate the buffer, for example:

cShared[5] = 99;

ReleaseRtSemaphore (hSema4, 1);

You obviously will do error checking in production quality code. We just do not include it here to show the key idea of the code.