Some semaphore implementations provide a function getValue () that returns the current value of a semaphore. This function may, for instance, be invoked prior to calling wait () so that a process will only call wait () if the value of the semaphore is > 0, thereby preventing blocking while waiting for the semaphore. For example:

if (getValue (&sem) >0

wait (&sem);

What is the problem in this approach?

Question

Elliana Keith

Computers & Technology

28 March, 13:03

Some semaphore implementations provide a function getValue () that returns the current value of a semaphore. This function may, for instance, be invoked prior to calling wait () so that a process will only call wait () if the value of the semaphore is > 0, thereby preventing blocking while waiting for the semaphore. For example:

if (getValue (&sem) >0

wait (&sem);

What is the problem in this approach?

+4

Answers (1)

Know the Answer?

Romeo Vaughan · Answer 1

Answer and Explanation:

The values of the semaphore can always be 0 for a particular process A, because whenever process A checks the

value by using getValue (&sem), some process B can be using the semaphore, after process B releases and puts

the value to 1, some other process C can get that semaphore by seeing the value > 0 and decrements its value

to 0 again. Now If the process A comes again It will see the value to be 0 again and this can go on ...

process A will never get the semaphore.