CSEIT – GATE 2025 Subject – Operating System/Topic – Process Synchronization (based on Algo-3).
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Here is a structured and GATE-focused explanation for:
🎓 CSE/IT – GATE 2025
📘 Subject: Operating System
📌 Topic: Process Synchronization (Based on Algo-3 – Peterson’s Algorithm)
🧠 What is Process Synchronization?
Process Synchronization is the technique used to coordinate the execution of concurrent processes that share resources. It ensures that:
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Only one process accesses the critical section (CS) at a time (Mutual Exclusion),
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The system makes progress without unnecessary delay,
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Every process eventually gets a chance (Bounded Waiting).
🔐 Algo-3: Peterson’s Algorithm
📌 Used for: Synchronization between 2 processes (P0 and P1)
📌 Type: Software-based solution
📌 Key Features:
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Guarantees mutual exclusion
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Ensures progress and bounded waiting
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No need for hardware-level atomic instructions
⚙️ Shared Variables:
👨💻 Code for Process Pi (i = 0 or 1):
✅ How It Works:
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Each process sets its flag to
trueindicating its interest in entering CS. -
It gives the turn to the other process.
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If the other process also wants to enter and it’s its turn, the current process waits.
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This guarantees mutual exclusion.
📌 Satisfies the 3 Conditions of Critical Section Problem:
| Condition | Met? | Explanation |
|---|---|---|
| Mutual Exclusion | ✅ | Only one process can enter the CS at a time. |
| Progress | ✅ | A process not in CS doesn’t block others. |
| Bounded Waiting | ✅ | Each process gets a turn in a finite time. |
🧪 GATE-Style Example Question:
Q: In Peterson’s algorithm for two processes P0 and P1, what ensures mutual exclusion?
A. Setting turn = 1 - i
B. The flag array
C. The combination of flag[] and turn
D. None of the above
✅ Correct Answer: C – Both flag[] and turn are essential for mutual exclusion.
📖 Summary:
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Peterson’s Algorithm is simple but powerful.
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It’s a frequent topic in GATE questions.
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Best understood by writing and simulating the code.
Would you like:
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A flowchart of the algorithm?
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A PDF of this explanation?
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More practice questions or MCQs?
Let me know how you’d like to prepare!