Deadlock Interactive Demo

Master Deadlock concepts with FullstackGada! 🔒

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🔒 What is a Deadlock?

Deadlock: When two or more processes get stuck waiting for each other, unable to proceed or release resources!

💕 Love Triangle Analogy

👨
Person A: Holds Resource B, wants Resource A.
👨‍🦲
Person B: Holds Resource A, wants another resource.
👩
Resource A: Waiting for Person A, held by Person B.
🔄
Result: Circular wait—nobody lets go!
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🎮 Live Deadlock Simulator

Scenario: Two processes fight for resources!
🔵 Process 1
Status: Ready
🔴 Process 2
Status: Ready
💎 Resource A
Owner: None
💍 Resource B
Owner: None

Simulation Log:

Ready to simulate deadlock...

4️⃣ Four Conditions of Deadlock

Coffman Conditions: All four conditions must be met for a deadlock to occur!
// 🔐 Mutual Exclusion Condition
// A resource can only be used by one process at a time
Resource resourceA = new Resource("Resource A");
resourceA.setExclusive(true); // Only one can access
// Process 1 tries to access
if(resourceA.isAvailable()) {
resourceA.lockBy("Process 1");
System.out.println("Process 1 locked Resource A!");
}
// Process 2 tries to access same resource
if(resourceA.isAvailable()) {
System.out.println("Process 2: Resource A not available! 😢");
// Will have to wait...
}

🔐 Mutual Exclusion Examples:

👩
Person A: Only one person can talk to her at a time.
🖨️
Printer: Only one document can print at a time.
💾
Database Lock: Only one transaction can modify a record.
Click to test mutual exclusion condition...
// ⏳ Hold and Wait Condition
// A process holds resources while waiting for others
class Process {
List heldResources = new ArrayList<>();
List waitingFor = new ArrayList<>();
public void executeProcess1() {
// Process 1 holds Resource B
heldResources.add(new Resource("Resource B"));
System.out.println("Process 1: Holding Resource B!");
// Wants Resource A too
waitingFor.add(new Resource("Resource A"));
System.out.println("Process 1: Waiting for Resource A!");
}
}
// Process 2 holds Resource A, wants another resource
process2.hold("Resource A");
process2.waitFor("Other Resource");

⏳ Hold and Wait Examples:

👨
Process 1: Holds Resource B, waits for Resource A.
👨‍🦲
Process 2: Holds Resource A, waits for another resource.
💻
Database: Locks Table A, waits for Table B.
Click to test hold and wait condition...
// 🚫 No Preemption Condition
// Resources cannot be forcefully taken
class Resource {
private String owner;
private boolean canPreempt = false;
public boolean forceRelease(String newOwner) {
if(!canPreempt) {
System.out.println(owner + " says: I'll release it myself!");
return false; // Cannot preempt
}
return true;
}
}
// Example usage
Resource resourceA = new Resource("Resource A");
resourceA.lockBy("Process 2");
// Process 1 tries to preempt
if(!resourceA.forceRelease("Process 1")) {
System.out.println("Process 1: Must wait for Process 2 to release!");
}

🚫 No Preemption Examples:

👨‍🦲
Process 2: "Resource A is mine, no one can take it!"
🖨️
Printer: Document printing cannot be interrupted.
💾
File Lock: Process must release it; OS can't force it.
Click to test no preemption condition...
// 🔄 Circular Wait Condition
// Processes form a circular chain of waiting
// Circular dependency chain
Process process1 = new Process("Process 1");
Process process2 = new Process("Process 2");
Process process3 = new Process("Process 3");
// Process 1 holds Resource B, wants Resource A
process1.hold("Resource B");
process1.waitFor("Resource A"); // Held by Process 2
// Process 2 holds Resource A, wants Resource C
process2.hold("Resource A");
process2.waitFor("Resource C"); // Held by Process 3
// Process 3 holds Resource C, wants Resource B
process3.hold("Resource C");
process3.waitFor("Resource B"); // Back to Process 1!
// Result: Circular wait - nobody moves!
// Process 1 -> Process 2 -> Process 3 -> Process 1 (cycle!)

🔄 Circular Wait Examples:

👨➡️💎
Process 1: Holds Resource B, wants Resource A (held by Process 2).
👨‍🦲➡️💍
Process 2: Holds Resource A, wants Resource C (held by Process 3).
👨‍💼➡️💎
Process 3: Holds Resource C, wants Resource B (held by Process 1).
🔄
Circle Complete: Infinite loop of waiting!
Click to test circular wait condition...

🛡️ Deadlock Prevention Techniques

Prevention Strategy: Break one of the four conditions to avoid deadlock!
Technique How It Works Real-World Example Pros/Cons
🔑 Resource Ordering Allocate resources in a fixed order. Always lock Resource B before Resource A. ✅ Simple | ❌ Restrictive
⏰ Timeout Cancel the process if it waits too long. Wait 5 minutes, then abort the transaction. ✅ Practical | ❌ May lose work
⚡ Short Transactions Complete tasks quickly to reduce lock time. Lock resource briefly, then release. ✅ Reduces deadlock chance | ❌ May need multiple transactions
🔍 Auto Detection System detects and resolves deadlocks. Database rolls back one transaction automatically. ✅ Automatic | ❌ Some work lost

🌍 Real-World Deadlock Examples

Scenario Deadlock Situation How It Happens Solution
🏦 Banking System Two accounts transferring funds. Account A locks Account 1, Account B locks Account 2, each waits for the other. Resource ordering—lock lower account number first.
🛒 E-commerce Inventory and order processing conflict. Order locks product, inventory locks order table. Short transactions, proper lock ordering.
📱 Phone System Two calls connect simultaneously. Call A dials B, Call B dials A at the same time. Call queueing, timeout mechanism.
🚗 Traffic Intersection Cars block all paths. All cars need to move forward but can't back up. Traffic signals, roundabouts.
💻 File System Two processes access files. Process 1 locks File A, needs File B; Process 2 locks File B, needs File A. File locking hierarchy, deadlock detection.

💡 Pro Tips for Avoiding Deadlocks

  • 🔑 Resource Ordering: Always acquire resources in a consistent order.
  • ⏰ Use Timeouts: Set limits to prevent infinite waiting.
  • ⚡ Keep Transactions Short: Minimize lock duration to reduce conflicts.
  • 🔍 Enable Deadlock Detection: Let systems like databases handle conflicts automatically.
Pro Tip: "Break the deadlock cycle before it traps you!" 😄