Short Trick Of Process Synchronization ( Solve any question in few minutes).

Short Trick Of Process Synchronization ( Solve any question in few minutes).

Here’s a short trick guide to help you quickly solve any Process Synchronization question in GATE (or similar competitive exams) in a few minutes:

Topic: Process Synchronization

Goal: Identify Mutual Exclusion, Progress, Bounded Waiting in code
Target: GATE-level MCQs or code analysis

TRICK 1: Look for the 3 Magic Words

Always check if the algorithm/code satisfies:

1. Mutual Exclusion – Only 1 process in the Critical Section

2. Progress – No unnecessary blocking

3. Bounded Waiting – Every process eventually gets a turn

Tip: If even one of these is violated, it’s not a correct solution.

TRICK 2: Remember the CORE ALGORITHMS

Algo No.	Name	Processes	Hardware Needed	Reliable?	Notes
1	Simple Lock	2+	No		Violates progress
2	Dekker’s Algo	2	No		Software-only
3	Peterson’s Algo	2	No		Easy to simulate
4	Test-and-Set Lock	2+	Yes (Atomic op)		Uses hardware instruction
5	Semaphore	2+	No		wait() and signal()
6	Monitor	2+	No		High-level abstraction

Peterson’s = Most Common in GATE Questions!

TRICK 3: Identify the Entry & Exit Sections

Quickly scan the code for these patterns:

Entry Section (wants to enter CS):

• flag[i] = true; → intention to enter

• turn = 1 - i; → gives other process a chance

• while(...) → busy wait / condition checking

Exit Section (leaves CS):

• flag[i] = false;

• turn = ...; → resets turn for the other process

TRICK 4: Use This YES/NO Table

Condition to Check	Look for in Code	Shortcut Decision
Mutual Exclusion?	Only one process allowed in CS	if while(flag[] && turn) pattern exists
Progress?	No unnecessary delay if CS is free	if turn changes appropriately
Bounded Waiting?	Process won’t wait forever	if turn is assigned fairly

TRICK 5: Look for Common MCQ Keywords

Watch for these question patterns:

• “Which condition is violated?”
  → Use the YES/NO table above

• “How many processes can be in CS?”
  → If more than one, Mutual Exclusion is violated

• “What is the purpose of turn or flag[]?”
  → flag[] = intent, turn = fairness

• “Identify correct algorithm from options”
  → Match pattern to Peterson, Dekker, etc.

Super Short Summary

flag[] = true → process wants to enter
while (flag[other] && turn == other) → wait
Critical Section
Reset flag[i] = false, set turn = other

Example (Peterson’s):

This ensures:
Mutual Exclusion
Progress
Bounded Waiting

Would you like:

• A printable cheat sheet?

• Practice MCQs with answers?

• Visual flowcharts for each algorithm?

Let me know!

Short Trick Of Process Synchronization ( Solve any question in few minutes).

Process Synchronization Race Condition: Critical Section …

Chapter 5: Process Synchronization