CMP$3001$ Operating Systems

Project $($Synchronization$)$

Due: Sunday, December $29$th $(23$:$59)$

The Reader Writer Problem

In this project you will need to provide a solution to readers$-$writers problem in which several processes $($readers and writers$)$ are trying to access shared variables. Obviously, if two readers access the shared data simultaneously, no adverse effects will result, hence, they are allowed to access. However, if a writer and some other process $($either a reader or a writer$)$ access the data simultaneously, chaos may ensue. To ensure that these difficulties do not arise, we require that the writers have exclusive access to the shared data while writing to the data.

The solution must guarantee that:

If a writer has begun writing process, then

No additional writer can perform write functionNo reader is allowed to readThe writer must ensure that data not yet read by all readers is not overwritten.

If $1$ or more readers are reading, then

Other readers may read as wellNo writer may perform write function until all readers have finished reading.Readers must read the same data only once.

$$You are given Test class written in Java that use ReadWriteLock class and threads for the problem. You are expected to use Semaphore provided in the code.$$

Two operations on the semaphore is allowed; acquire$()$ and release$()($they correspond wait and signal functions$)$

To do: Implement methods of ReadWriteLock class given.

class ReadWriteLock$\{$

$$ private Semaphore S$=$new Semaphore$(1)$;$$

$$ public void readLock$()\{$

$\}$

$$ public void writeLock$()\{$

$\}$

$$ public void readUnLock$()\{$

$\}$

$$ public void writeUnLock$()\{$

$\}$

$$

$\}$