feat: add pthread race condition demonstration using shared variable

Implemented a multithreaded C program where two threads concurrently modify
a shared global variable without synchronization. Demonstrates real-world
data races and non-deterministic output caused by unsynchronized access
to shared memory.

Signed-off-by: https://github.com/Someshdiwan <[email protected]>

Author: Someshdiwan

Section19MultiThreading/Threading Inside Look/RaceConditionDemo.c

@@ -0,0 +1,53 @@
+#include <pthread.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+// Shared variable used by both threads
+volatile long int a = 0;
+
+// Thread function 1 — increments 'a' by each loop index
+void* threadFunction1(void* args)
+{
+    for (int i = 1; i <= 500000; i++) {
+        a = a + i;  // Updating shared variable (not thread-safe)
+    }
+    return NULL;
+}
+
+// Thread function 2 — performs the same addition as thread 1
+void* threadFunction2(void* args)
+{
+    for (int i = 1; i <= 500000; i++) {
+        a = a + i;  // Concurrent modification of shared data
+    }
+    return NULL;
+}
+
+int main(int argc, char** argv)
+{
+    pthread_t one, two;  // Thread identifiers
+    a = 0;               // Initialize shared variable
+
+    // Start two threads running separate functions
+    pthread_create(&one, NULL, threadFunction1, NULL);
+    pthread_create(&two, NULL, threadFunction2, NULL);
+
+    // Wait for both threads to finish
+    pthread_join(one, NULL);
+    pthread_join(two, NULL);
+
+    // Print the final result after both threads have completed
+    printf("Final value of a = %ld\n", a);
+
+    return 0;
+}
+
+/*
+•	Actually creates two threads with pthread_create.
+•	Both threadFunction1 and threadFunction2 run concurrently, each modifying the same global variable a.
+•	Because updates to a are not synchronized, the final result varies each run — a textbook race condition example.
+•	Demonstrates real multithreading behavior.
+
+Result: inconsistent and unpredictable — shows concurrency and data races.
+*/