test

exp1/badcount.c

@@ -0,0 +1,62 @@
+#include <pthread.h>
+#include <time.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+int cnt = 0;
+sem_t mutex;
+
+void *increase(void *vargp)
+{
+    unsigned int niters = (unsigned int)vargp;
+    for (unsigned int i = 0; i < niters; i++)
+    {
+        sem_wait(&mutex);
+        cnt++;
+        sem_post(&mutex);
+    }
+    return NULL;
+}
+
+void *decrease(void *vargp)
+{
+    unsigned int niters = (unsigned int)vargp;
+    for (unsigned int i = 0; i < niters; i++)
+    {
+        sem_wait(&mutex);
+        cnt--;
+        sem_post(&mutex);
+    }
+    return NULL;
+}
+
+int main(int argc, char **argv)
+{
+    unsigned int niters;
+    pthread_t t1,t2;
+
+    if (argc != 2)
+    {
+        printf("Usage: %s <niters>\n", argv[0]);
+        exit(2);
+    }
+    niters = atoll(argv[1]);
+
+    sem_init(&mutex, 0, 1);
+    pthread_create(&t1,NULL,increase,(void*)niters);
+    pthread_create(&t2,NULL,decrease,(void*)niters);
+    pthread_join(t1,NULL);
+    pthread_join(t2,NULL);
+
+    if (cnt != 0)
+    {
+        printf("Error! cnt=%d\n", cnt);
+    }
+    else
+    {
+        printf("Correct! cnt=%d\n", cnt);
+    }
+    sem_destroy(&mutex);
+    exit(0);
+}