Multi Read Single Write (Reader Writer Problem's Solution)

https://en.wikipedia.org/wiki/Readers%E2%80%93writer_lock


Begin Read

Lock r.
Increment b.
If b = 1, lock g.
Unlock r.
End Read


Lock r.
Decrement b.
If b = 0, unlock g.
Unlock r.
Begin Write

Lock g.
End Write

Unlock g.