Showed an example, that raceconditions are still possible even with mutex

G-concurrency/racecondition.rs

@@ -0,0 +1,58 @@
+use std::sync::{Arc, Mutex};
+use std::thread;
+use std::time::Duration;
+
+fn main() {
+    // A shared bank account starting with $100
+    let account_balance = Arc::new(Mutex::new(100));
+
+    // Thread A: Attempts to withdraw $80
+    let balance_clone1 = Arc::clone(&account_balance);
+    let handle1 = thread::spawn(move || {
+        // 1. CHECK: Lock the account just to check the balance
+        let current_balance = *balance_clone1.lock().unwrap();
+        
+        if current_balance >= 80 {
+            println!("Thread A: Balance is ${}. Approval granted!", current_balance);
+            
+            // Simulate a tiny delay (e.g., network latency or CPU context switch)
+            // This gives Thread B time to sneak in and check the balance
+            thread::sleep(Duration::from_millis(5));
+            
+            // 2. ACT: Lock again to deduct the money
+            let mut balance_guard = balance_clone1.lock().unwrap();
+            *balance_guard -= 80;
+            println!("Thread A: Successfully withdrew $80.");
+        } else {
+            println!("Thread A: Declined. Insufficient funds.");
+        }
+    });
+
+    // Thread B: Simultaneously attempts to withdraw $80
+    let balance_clone2 = Arc::clone(&account_balance);
+    let handle2 = thread::spawn(move || {
+        // 1. CHECK: Lock the account just to check the balance
+        let current_balance = *balance_clone2.lock().unwrap();
+        
+        if current_balance >= 80 {
+            println!("Thread B: Balance is ${}. Approval granted!", current_balance);
+            
+            // Simulate a tiny delay (e.g., network latency or CPU context switch)
+            // This gives Thread B time to sneak in and check the balance
+            thread::sleep(Duration::from_millis(5));
+            
+            // 2. ACT: Lock again to deduct the money
+            let mut balance_guard = balance_clone2.lock().unwrap();
+            *balance_guard -= 80;
+            println!("Thread B: Successfully withdrew $80.");
+        } else {
+            println!("Thread B: Declined. Insufficient funds.");
+        }
+    });
+
+    handle1.join().unwrap();
+    handle2.join().unwrap();
+
+    // Final result
+    println!("Final Bank Balance: ${}", *account_balance.lock().unwrap());
+}