Process 2 Process 1 can not directly access resources
So the system has opened up a shared space, but for the shared space operations are mutually exclusive
mutually exclusive is to say that only one process to operate in this space, to wait for another
regular means of PV operation
Pipeline: a special kind of file sharing
only when the write data filled pipeline, in order to use this time to read the data pipeline removed, emptied the same way only to re-read
