Disabled external gits

cs453-ca/CS453-2021-project/sync-examples/counter2.c

@@ -0,0 +1,45 @@
+#include <pthread.h>
+#include <inttypes.h>
+#include <assert.h>
+#include <stdio.h>
+
+#include "lock.h"
+
+#define RUNS (4096 * 256)
+#define THREADS 4
+
+static struct lock_t lock;
+
+static int counter = 0;
+
+void* count(void* null) {
+  for (int r = 0; r < RUNS; r++) {
+    lock_acquire(&lock);
+    counter++;
+    lock_release(&lock);
+    // Still equivalent, but only one thread accesses counter at a time, so it's
+    // thread safe, no concurrent access/data race. :)
+    // **Correct**
+  }
+}
+
+int main() {
+  lock_init(&lock);
+  pthread_t handlers[THREADS];
+
+  for (intptr_t i = 0; i < THREADS; i++) {
+    int res = pthread_create(&handlers[i], NULL, count, NULL);
+    assert(!res);
+  }
+
+  for (int i = 0; i < THREADS; i++) {
+    int res = pthread_join(handlers[i], NULL);
+    assert(!res);
+  }
+
+  if (counter != RUNS * THREADS) {
+    printf("Didn't count so well. :/, found %d\n", counter);
+  } else {
+    printf("Counted up to %d.\n", counter);
+  }
+}