Consider the below implementations of a semaphore's wait and signal operations: wait ) { disable interrupts; sem.value--; if (sem.value < 0) { save_state (current) ; // current process State[current] = Blocked; //A gets blocked Enqueue(current, sem.queue); current = select_from_ready_queue(0: State[current] = Running; restore_state (current); //B starts running signal){ disable interrupts; sem.value++; if (sem.value <= 0){ k = Dequeue(sem.queue); State[k] = Ready; Enqueue (k, ReadyQueue); } Enable interrupts; } Enable interrupts; } a) What are the critical sections inside the wait and signal operations which are protected by disabling and enabling of interrupts? b) Give example of a specific execution scenario for the above code leading to inconsistency if the critical sections inside implementation of wait() and signal) are not protected (by disabling of interrupts c) Suppose that process A calling semaphore wait() gets blocked and another process B is selected to run (refer to the above code). Since interrupts are enabled only at the completion of the wait operation, will B start executing with the interrupts disabled? Explain your answer.

Consider the below implementations of a semaphore's wait and signal operations: wait ) { disable interrupts; sem.value--; if (sem.value < 0) { save_state (current) ; // current process State[current] = Blocked; //A gets blocked Enqueue(current, sem.queue); current = select_from_ready_queue(0: State[current] = Running; restore_state (current); //B starts running signal){ disable interrupts; sem.value++; if (sem.value <= 0){ k = Dequeue(sem.queue); State[k] = Ready; Enqueue (k, ReadyQueue); } Enable interrupts; } Enable interrupts; } a) What are the critical sections inside the wait and signal operations which are protected by disabling and enabling of interrupts? b) Give example of a specific execution scenario for the above code leading to inconsistency if the critical sections inside implementation of wait() and signal) are not protected (by disabling of interrupts c) Suppose that process A calling semaphore wait() gets blocked and another process B is selected to run (refer to the above code). Since interrupts are enabled only at the completion of the wait operation, will B start executing with the interrupts disabled? Explain your answer.

Systems Architecture

7th Edition

ISBN:9781305080195

Author:Stephen D. Burd

Publisher:Stephen D. Burd

Chapter13: Internet And Distributed Application Services

Section: Chapter Questions

Problem 5VE

See similar textbooks