adding race condition example

Signed-off-by: VictorRodriguez <victor.rodriguez.bahena@intel.com>

Author: VictorRodriguez

labs/04/race_condition.c

@@ -0,0 +1,58 @@
+#include <pthread.h>
+#include <semaphore.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#define NITER 1000000
+
+int cnt = 0;
+
+void * Count(void * a)
+{
+    int i, tmp;
+    for(i = 0; i < NITER; i++)
+    {
+        tmp = cnt;      /* copy the global cnt locally */
+        tmp = tmp+1;    /* increment the local copy */
+        cnt = tmp;      /* store the local value into the global cnt */
+    }
+}
+
+int main(int argc, char * argv[])
+{
+    pthread_t tid1, tid2;
+
+    if(pthread_create(&tid1, NULL, Count, NULL))
+    {
+      printf("\n ERROR creating thread 1");
+      exit(1);
+    }
+
+    if(pthread_create(&tid2, NULL, Count, NULL))
+    {
+      printf("\n ERROR creating thread 2");
+      exit(1);
+    }
+
+    if(pthread_join(tid1, NULL))    /* wait for the thread 1 to finish */
+    {
+      printf("\n ERROR joining thread");
+      exit(1);
+    }
+
+    if(pthread_join(tid2, NULL))        /* wait for the thread 2 to finish */
+    {
+      printf("\n ERROR joining thread");
+      exit(1);
+    }
+
+    if (cnt < 2 * NITER)
+        printf("\n BOOM! cnt is [%d], should be %d\n", cnt, 2*NITER);
+    else
+        printf("\n OK! cnt is [%d]\n", cnt);
+
+    pthread_exit(NULL);
+}
+
+
+