There is a situation that two groups of concurrent processes share a file. When two or more reading processes access the shared data at the same time, there will be no side effects. However, if a write process and other processes access the shared data at the same time, the data inconsistency error may be caused.

So, to solve this problem, we need to realize the following:

1. Allows multiple readers to read files at the same time


2. Only one writer is allowed to write information to the file


3. No other reader or writer is allowed to work until any writer has completed the writing operation


4. Before a writer performs a write operation, he should let all existing readers and writers quit


5. The following algorithm is read process priority because it may cause the write process to starve