thread example mutex_init

thread_examples/thread_example_semaphore.c

@@ -12,12 +12,11 @@
 
 struct global_data{
     int count;
+    pthread_mutex_t mtx;
     sem_t sem_a;
     sem_t sem_b;
 };
 
-pthread_mutex_t mtx = PTHREAD_MUTEX_INITIALIZER;
-
 void * task_a(void * ctx)
 {
     struct global_data *d = ctx;
@@ -26,10 +25,10 @@ void * task_a(void * ctx)
     printf("started task_a\n");
     for(i=0; i < d->count; ++i){
 	sem_wait(&d->sem_a);
-	pthread_mutex_lock(&mtx);
+	pthread_mutex_lock(&d->mtx);
 	printf("task_a: %d\n",i);
 	sem_post(&d->sem_b);
-	pthread_mutex_unlock(&mtx);
+	pthread_mutex_unlock(&d->mtx);
     }
     return NULL;
 }
@@ -42,10 +41,10 @@ void * task_b(void * ctx)
     printf("started task_b\n");
     for(i=0; i < d->count; ++i){
 	sem_wait(&d->sem_b);
-	pthread_mutex_lock(&mtx);
+	pthread_mutex_lock(&d->mtx);
 	printf("task_b: %d\n",i);
 	sem_post(&d->sem_a);
-	pthread_mutex_unlock(&mtx);
+	pthread_mutex_unlock(&d->mtx);
     }
     return NULL;
 }
@@ -53,6 +52,7 @@ void * task_b(void * ctx)
 int global_data_init(struct global_data *d)
 {
     d->count = 10;
+    pthread_mutex_init(&d->mtx, NULL);
     if(sem_init(&d->sem_a, 0, 0)){
 	return 1;
     }
@@ -85,10 +85,10 @@ int main()
 	exit(3);
     }
     sleep(1);
-    pthread_mutex_lock(&mtx);
+    pthread_mutex_lock(&data.mtx);
     printf("signalling semaphore\n");
     sem_post(&data.sem_a);
-    pthread_mutex_unlock(&mtx);
+    pthread_mutex_unlock(&data.mtx);
     pthread_join(thread_a, NULL);
     pthread_join(thread_b, NULL);
    return 0;