Volatile example: Circular Buffer

• Lock free circular buffer is based on the shared variables updates, visible from all threads

#define next(a) (((a)+1)%nEntries)

volatile int writeptr, readptr;

/* Producer */

while (1) {

buffer[writeptr] = new stuff;

while (next(writeptr) == readptr);

writeptr = next(writeptr);

}

/* Consumer: */

while (1) {

while (writeptr == readptr);

stuff = buffer[readptr];

readptr = next(readptr);

}

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