rwlock of pthread demo

rwlock_example/rwlock_example.c

@@ -0,0 +1,103 @@
+#include <stdio.h>
+#include <unistd.h>
+#include <assert.h>
+#include <pthread.h>
+
+static pthread_rwlock_t rw_lock;
+static int n_r = 0;
+static int n_w = 0;
+pthread_mutex_t state_check_mutex;
+
+static void
+cs_static_check() {
+
+	pthread_mutex_lock(&state_check_mutex);
+	assert(n_r >= 0 && n_w >= 0); /* cannot be negative */
+
+	if (n_r == 0 && n_w == 0) {
+		//valid condition
+	}
+	else if (n_r > 0 && n_w == 0) {
+		//valid condition
+	}
+	else if (n_r == 0 && n_w == 1) {
+		//valid condition
+	}
+	else
+		assert(0);
+
+	printf("n_r = %d, n_w = %d\n", n_r, n_w);
+	pthread_mutex_unlock(&state_check_mutex);
+}
+
+static void
+execute_cs() {
+
+	cs_status_check();
+}
+
+static void
+reader_enter_cs() {
+	pthread_mutex_lock(&state_check_mutex);
+	n_r++;
+	pthread_mutex_unlock(&state_check_mutex);
+}
+
+static void
+reader_leaves_cs() {
+	pthread_mutex_lock(&state_check_mutex);
+	n_r--;
+	pthread_mutex_unlock(&state_check_mutex);
+}
+
+
+static void
+writer_enter_cs() {
+	n_w++;
+}
+
+static void
+writer_leaves_cs() {
+	n_w--;
+}
+
+void*
+read_thread_fn(void* arg) {
+	while (1) {
+		pthread_rwlock_rdlock(&rw_lock);
+
+		reader_enter_cs();
+		execute_cs();
+		reader_leaves_cs();
+
+		pthread_rwlock_unlock(&rw_lock);
+	}
+}
+
+void*
+write_thread_fn(void* arg) {
+
+	while (1) {
+		pthread_rwlock_wrlock(&rw_lock);
+		writer_enter_cs();
+		execute_cs();
+		writer_leaves_cs();
+		pthread_rwlock_unlock(&rw_lock);
+	}
+}
+
+int
+main(int argc, char* argv[]) {
+
+	static pthread_t th1, th2, th3, th4, th5, th6;
+	pthread_rwlock_init(&rw_lock, NULL);
+	pthread_mutex_init(&state_check_mutex, NULL);
+	pthread_create(&th1, NULL, read_thread_fn, NULL);
+	pthread_create(&th2, NULL, read_thread_fn, NULL);
+	pthread_create(&th3, NULL, read_thread_fn, NULL);
+	pthread_create(&th4, NULL, write_thread_fn, NULL);
+	pthread_create(&th5, NULL, write_thread_fn, NULL);
+	pthread_create(&th6, NULL, write_thread_fn, NULL);
+	pthread_exit(0);
+	return 0;
+}