Strict Alternation (Software approach)
- the integer variable turn (keeps track of whose turn it is to enter the CR),
- initially, process 0 inspects turn, finds it to be 0, and enters its CR,
- process 1 also finds it to be 0 and therefore sits in a tight loop continually testing turn to see when it becomes,
Which of the mutual exclusion properties does strict alternation satisfy?
answer: Strict alternation satisfies mutex – only the thread whose turn it is (determined by the turn variable) can access the shared data.
What is bounded waiting in OS?
Bounded Waiting. ▪ After a process made a request to enter its. critical section and before it is granted the. permission to enter, there exists a bound on. the number of turns that other processes are allowed to enter.
What is Peterson's solution in OS?
Peterson's algorithm (or Peterson's solution) is a concurrent programming algorithm for mutual exclusion that allows two or more processes to share a single-use resource without conflict, using only shared memory for communication.
What is mutual exclusion in OS with example?
A mutual exclusion (mutex) is a program object that prevents simultaneous access to a shared resource. This concept is used in concurrent programming with a critical section, a piece of code in which processes or threads access a shared resource.
What is bounded buffer problem in OS?
The bounded-buffer problems (aka the producer-consumer problem) is a classic example of concurrent access to a shared resource. A bounded buffer lets multiple producers and multiple consumers share a single buffer. Producers write data to the buffer and consumers read data from the buffer.
What is deadlock OS?
A deadlock is a situation in which two computer programs sharing the same resource are effectively preventing each other from accessing the resource, resulting in both programs ceasing to function. The earliest computer operating systems ran only one program at a time.
What is Peterson's problem?
Peterson's solution provides a good algorithmic description of solving the critical-section problem and illustrates some of the complexities involved in designing software that addresses the requirements of mutual exclusion, progress, and bounded waiting.
What is semaphore OS?
Semaphore is an integer variable which is used as a signal to allow or not allow a process to access the critical section of the code or certain other resources. There are two types of semaphores: Binary - take on values 0 or 1. Counting - take on any integer value.
Can Peterson's algorithm result in deadlock?
However, in Peterson solution, A deadlock can never happen because the process which first sets the turn variable will enter in the critical section for sure. Therefore, if a process is preempted after executing line number 4 of the entry section then it will definitely get into the critical section in its next chance.
What is difference between mutex and semaphore?
A Mutex is different than a semaphore as it is a locking mechanism while a semaphore is a signalling mechanism. A binary semaphore can be used as a Mutex but a Mutex can never be used as a semaphore.
What is no preemption in OS?
7.2. No preemption - Once a process is holding a resource ( i.e. once its request has been granted ), then that resource cannot be taken away from that process until the process voluntarily releases it.
What is mutual exclusion and critical section in OS?
Mutual exclusion implies that only one process can be inside the critical section at any time. If any other processes require the critical section, they must wait until it is free. Progresss. Progress means that if a process is not using the critical section, then it should not stop any other process from accessing it.
What is bounded waiting in synchronization?
Bounded Waiting: A bound must exist on the number of times that other processes are allowed to enter their critical sections after a process has made a request to enter its critical section and before that request is granted.
Does deadlock imply bounded waiting?
Deadlock means no progress and progress not related to Bounded Wait . Deadlock not related to BW . If there is a deadlock , bounded waiting can possible. But progress can not possible.
Which of the following condition stands true for bounded waiting?
Which of the following condition stands true for Bounded Waiting? If no thread is executing in its critical section, and if there are some threads that wish to enter their critical sections, then one of these threads will get into the critical section.
What are the two steps of process execution?
Answer is "I/O Burst, CPU Burst"
What happens when process 0 leaves the CS?
When process 0 leaves the CS, it sets turn to 1, to allow process 1 to enter its CS. Suppose process 1 finishes its CS quickly, so both processes are in their non-CS sections, with turn set to 0. Now process 0 executes its whole loop quickly, coming back to its non-CS with turn set to 1. At this point, process 0 finishes its non-CS and goes back to the top of its loop. Unfortunately, it is not permitted to enter its CS now, because turn is 1 and process 1 is busy with its non-CS. This situation violates condition 3 set out before; process 0 is being blocked by a process not in its CS. Therefore, taking turns is not a good idea when one of the processes is much slower than the other.
Why is it not permitted to enter its CS now?
Unfortunately, it is not permitted to enter its CS now, because turn is 1 and process 1 is busy with its non-CS. This situation violates condition 3 set out before; process 0 is being blocked by a process not in its CS. Therefore, taking turns is not a good idea when one of the processes is much slower than the other.
