implementation of semaphore in kernel.
There are using three application at user level.
In 1st application three threads using for Open,Write and close.
in 2nd application three threads using for Open,read and close.
And last application is same as 2nd app.
thread semaphore is also used for synchronize the operation in every single application.
At Kernel level: when file open in Read-only mode it wait for completion of write operation then after semaphore release to access by both reader.
