Read Write Lock
We discuss a common interview question involving synchronization of multiple reader threads and a single writer thread.
We'll cover the following...
Read Write Lock
Imagine you have an application where you have multiple readers and a single writer. You are asked to design a lock which lets multiple readers read at the same time, but only one writer write at a time.
Solution
First of all let us define the APIs our class will expose. We'll need two for writer and two for reader. These are:
- acquire_read_lock
- release_read_lock
- acquire_write_lock
- release_write_lock
This problem becomes simple if you think about each case:
Before we allow a reader to enter the critical section, we need to make sure that there's no writer in progress. It is ok to have other readers in the critical section since they aren't making any modifications.
Before we allow a writer to enter the critical section, we need to make sure that there's no reader or writer in the critical section.
Let's start with the reader use case. We can have multiple readers acquire the read lock and to keep track of all of them; we'll need a count. We increment this ...