test: add tests for the uv_rwlock implementation

PR-URL: libuv#525
Reviewed-By: Saúl Ibarra Corretgé <saghul@gmail.com>

test/test-list.h

@@ -291,6 +291,7 @@ TEST_DECLARE   (threadpool_cancel_single)
 TEST_DECLARE   (thread_local_storage)
 TEST_DECLARE   (thread_mutex)
 TEST_DECLARE   (thread_rwlock)
+TEST_DECLARE   (thread_rwlock_trylock)
 TEST_DECLARE   (thread_create)
 TEST_DECLARE   (thread_equal)
 TEST_DECLARE   (dlerror)
@@ -707,6 +708,7 @@ TASK_LIST_START
   TEST_ENTRY  (thread_local_storage)
   TEST_ENTRY  (thread_mutex)
   TEST_ENTRY  (thread_rwlock)
+  TEST_ENTRY  (thread_rwlock_trylock)
   TEST_ENTRY  (thread_create)
   TEST_ENTRY  (thread_equal)
   TEST_ENTRY  (dlerror)

test/test-mutexes.c

@@ -61,3 +61,62 @@ TEST_IMPL(thread_rwlock) {
 
   return 0;
 }
+
+
+TEST_IMPL(thread_rwlock_trylock) {
+  uv_rwlock_t rwlock;
+  int r;
+
+  r = uv_rwlock_init(&rwlock);
+  ASSERT(r == 0);
+
+  /* No locks held. */
+
+  r = uv_rwlock_trywrlock(&rwlock);
+  ASSERT(r == 0);
+
+  /* Write lock held. */
+
+  r = uv_rwlock_tryrdlock(&rwlock);
+  ASSERT(r == UV_EBUSY);
+  r = uv_rwlock_trywrlock(&rwlock);
+  ASSERT(r == UV_EBUSY);
+
+  uv_rwlock_wrunlock(&rwlock);
+
+  /* No locks held. */
+
+  r = uv_rwlock_tryrdlock(&rwlock);
+  ASSERT(r == 0);
+
+  /* One read lock held. */
+
+  r = uv_rwlock_tryrdlock(&rwlock);
+  ASSERT(r == 0);
+
+  /* Two read locks held. */
+
+  r = uv_rwlock_trywrlock(&rwlock);
+  ASSERT(r == UV_EBUSY);
+
+  uv_rwlock_rdunlock(&rwlock);
+
+  /* One read lock held. */
+
+  uv_rwlock_rdunlock(&rwlock);
+
+  /* No read locks held. */
+
+  r = uv_rwlock_trywrlock(&rwlock);
+  ASSERT(r == 0);
+
+  /* Write lock held. */
+
+  uv_rwlock_wrunlock(&rwlock);
+
+  /* No locks held. */
+
+  uv_rwlock_destroy(&rwlock);
+
+  return 0;
+}