Question

12a Explain briefly (without giving any code) how threads can be used to simplify code that performs asyn- chronous operations such as communicating with an IO controller. 12b Explain briefly the difference between uthread_yield and uthread_block. 12c Is it possible for a thread to unblock itself? Explain your answer. 12d Consider a system in which there is at least one thread on the ready queue when a thread unblocks. What happens to the unblocked thread? Explain.

Answer 1

12a.Threading is a programming language that permits two or more programming execution points to run in application at the same time.Threads can be used to simplify code that performs asynchronous operations within an IO controller is that the thread will continue to work in parallel.In case of multithreading with IO controller it has two effects

1.Use multiple CPUs concurrently.

2.Use a CPU with one thread blocked.

12b.U thread_yield-It temporarily stops current thread if other threads are waiting.

uthread_block-A sleeping thread could be woken by using uthread_block.

12c.A thread could not be waken by itself.A thread that is blocked in wait() cannot execute any code until unblocked.

12d.A system in which there is only one thread is on ready queue when a thread unblocks then multithreading takes place.On a single core microprocessor it is possible to run multiple threads but not in parallel.The threads are running at same time but they are running in time slices allocated and controlled by OS.