Subject – Operating System Topic – Process Synchronization (example based on Algo-2).

Subject – Operating System Topic – Process Synchronization (example based on Algo-2).

Here is a GATE-focused explanation for:

Subject: Operating System

Topic: Process Synchronization

Example Based on Algo-2 – Dekker’s Algorithm

What is Process Synchronization?

In multiprocessing systems, multiple processes may try to access shared resources (like memory or files) simultaneously. This leads to race conditions if not properly synchronized.

To prevent this, process synchronization algorithms are used to manage access to the critical section (CS).

Algo-2: Dekker’s Algorithm (Two-Process Synchronization)

Purpose: Software-based solution to achieve mutual exclusion for 2 processes (P0 and P1)

Historical Significance: One of the earliest algorithms that satisfies:

• Mutual Exclusion

• Bounded Waiting

• Progress

Shared Variables Used:

Process Pi’s Code (i = 0 or 1):

Explanation of Key Parts:

• flag[i] = true: Process Pi wants to enter CS.

• while (flag[1-i]): If the other process also wants to enter, check turn.

• If turn != i: It waits and gives a chance to the other process.

• After exiting CS: Sets turn to the other process and resets its flag.

Example Scenario:

1. P0 and P1 both want to enter CS.

2. Both set flag[0] = true and flag[1] = true.

3. Now, both check each other’s flag:

   • If turn = 1, P0 waits and P1 proceeds.

   • If turn = 0, P1 waits and P0 proceeds.

4. After exiting CS, the current process gives turn to the other.

Satisfaction of Synchronization Requirements:

Requirement	Satisfied?	How?
Mutual Exclusion		Only one process enters CS at a time
Progress		No process is blocked unnecessarily
Bounded Waiting		Each process eventually gets a turn

GATE-Style Question:

Q: In Dekker’s algorithm, what ensures bounded waiting?

A. flag[]
B. turn variable
C. Both A and B
D. None of the above

Answer: C — Both are required to implement bounded waiting.

Would you like:

• A diagram/flowchart of Dekker’s Algorithm?

• A comparison between Dekker’s and Peterson’s Algorithm?

• MCQs and practice problems for GATE?

Let me know!

Subject – Operating System Topic – Process Synchronization (example based on Algo-2).

OPERATING SYSTEMS PROCESS SYNCHRONIZATION