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 processState[current] = Blocked; //A gets blockedEnqueue(current, sem.queue);current = select_from_ready_queue();State[current] = Running;restore_state (current); //B starts running}Enable interrupts;}signal(){Disable interrupts;sem.value++;if (sem.value <= 0){k = Dequeue(sem.queue);State[k] = Ready;Enqueue (k, ReadyQueue);}Enable interrupts;}%3|a) What are the critical sections inside the wait and signal operations which are protected bydisabling and enabling of interrupts?b) Give example of a specific execution scenario for the above code leading to inconsistency ifthe critical sections inside implementation of wait() and signal0 are not protected (bydisabling of interrupts).c) Suppose that process A calling semaphore wait() gets blocked and another process B isselected to run (refer to the above code). Since interrupts are enabled only at the completionof the wait operation, will B start executing with the interrupts disabled? Explain youranswer.

Solution: a) sem.value is the one which is protected by wait and signal, because in the critical…

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(); 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; }

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(); 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; }

Database System Concepts

7th Edition

ISBN:9780078022159

Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Chapter1: Introduction

Section: Chapter Questions

Problem 1PE

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Concept explainers

Embedded Software Development

Using specific programming languages (like C and C++) to write code for a specific hardware device in which it runs is called embedded software development. It makes the device smart by performing actions based on user's input which improves the user experience. They are designed to perform function-specific tasks rather than doing multiple tasks like computers. The embedded system is incredibly intuitive. An embedded software system could be a system developed and organized on any device, apart from an old-fashioned computer. It is the brain of a specific device; however, it is a solely useless tool and simple to elucidate what software system is embedded.

Question

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();
State[current] = Running;
restore_state (current); //B starts running
}
Enable interrupts;
}
signal(){
Disable interrupts;
sem.value++;
if (sem.value <= 0){
k = Dequeue(sem.queue);
State[k] = Ready;
Enqueue (k, ReadyQueue);
}
Enable interrupts;
}
%3|
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 signal0 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.

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