Process Synchronization and Critical Section

Study Notes

Process synchronization is the coordination of processes that require access to shared data
Critical-section problem: If multiple processes attempt to modify shared data at the same time, the data becomes inconsistent, impacting the accuracy, completeness and correctness.
The critical-section problem aims to ensure that only one process accesses shared data at a time

Concurrent processes can access shared data, causing inconsistency
The critical section problem emerges when multiple processes concurrently access and manipulate shared data, leading to unpredictable and potentially incorrect results.
Race condition: Processes accessing and manipulating shared data in an uncontrolled order leads to inconsistent results.

A system of n processes (p0, p1, … pn-1) access shared resources.
Each process has a critical section: a segment of code that accesses and modifies shared data.
To ensure data integrity, a protocol is required to ensure that only one process can execute its critical section at a time.
The critical section problem involves designing a protocol that guarantees mutual exclusion within the critical section.

Each process Pi has a generic structure:
- Entry Section: Where a process requests permission to enter its critical section.
- Critical Section: Where the process can execute operations on shared data.
- Exit Section: Where the process releases the critical section, allowing other processes to enter.
- Remainder Section: Where the process performs non-critical operations.

The solution requires satisfying two requirements:
- Mutual Exclusion: Ensures that no other process can execute in its critical section while another process is in its critical section.
- Progress: Guarantees that if no process is in its critical section, and several process wish to enter, then only those not in their remainder sections can participate in the decision of who will enter their critical section next, and this decision cannot be postponed indefinitely.