pthread: added pthread_rwlock_tryrd/wrlock()

Closes https://github.com/espressif/esp-idf/issues/9229

components/pthread/pthread_rwlock.c

@@ -1,5 +1,5 @@
 /*
- * SPDX-FileCopyrightText: 2021 Espressif Systems (Shanghai) CO LTD
+ * SPDX-FileCopyrightText: 2021-2023 Espressif Systems (Shanghai) CO LTD
  *
  * SPDX-License-Identifier: Apache-2.0
  */
@@ -191,6 +191,34 @@ int	pthread_rwlock_rdlock (pthread_rwlock_t *rwlock)
     return 0;
 }
 
+int	pthread_rwlock_tryrdlock (pthread_rwlock_t *rwlock)
+{
+    esp_pthread_rwlock_t *esp_rwlock;
+    int res;
+
+    res = checkrw_lock(rwlock);
+    if (res != 0) {
+        return res;
+    }
+
+    esp_rwlock = (esp_pthread_rwlock_t *)*rwlock;
+    res = pthread_mutex_trylock(&esp_rwlock->resource_mutex);
+    if (res != 0) {
+        return res;
+    }
+
+    if (esp_rwlock->active_writers == 0) {
+        esp_rwlock->active_readers++;
+        res = 0;
+    } else {
+        res = EBUSY;
+    }
+
+    pthread_mutex_unlock(&esp_rwlock->resource_mutex);
+
+    return res;
+}
+
 int	pthread_rwlock_wrlock(pthread_rwlock_t *rwlock)
 {
     esp_pthread_rwlock_t *esp_rwlock;
@@ -219,6 +247,35 @@ int	pthread_rwlock_wrlock(pthread_rwlock_t *rwlock)
     return 0;
 }
 
+int	pthread_rwlock_trywrlock (pthread_rwlock_t *rwlock) {
+    esp_pthread_rwlock_t *esp_rwlock;
+    int res;
+
+    res = checkrw_lock(rwlock);
+    if (res != 0) {
+        return res;
+    }
+
+    esp_rwlock = (esp_pthread_rwlock_t *)*rwlock;
+    res = pthread_mutex_trylock(&esp_rwlock->resource_mutex);
+    if (res != 0) {
+        return res;
+    }
+
+    if (esp_rwlock->active_readers > 0 ||
+            esp_rwlock->active_writers > 0 ||
+            esp_rwlock->waiting_writers > 0) { // the last check for waiting_writers is to avoid skipping the queue
+        res = EBUSY;
+    } else {
+        esp_rwlock->active_writers++;
+        res = 0;
+    }
+
+    pthread_mutex_unlock(&esp_rwlock->resource_mutex);
+
+    return res;
+}
+
 int	pthread_rwlock_unlock (pthread_rwlock_t *rwlock)
 {
     esp_pthread_rwlock_t *esp_rwlock;

components/pthread/test_apps/pthread_unity_tests/main/test_pthread_rwlock.c

@@ -293,3 +293,89 @@ TEST_CASE("wrlock multiple writers wait", "[pthread][rwlock]")
     TEST_ASSERT_EQUAL_INT(pthread_rwlock_destroy(&rwlock), 0);
     vQueueDelete(wait_queue);
 }
+
+TEST_CASE("tryrdlock invalid param", "[pthread][rwlock]")
+{
+    TEST_ASSERT_EQUAL_INT(pthread_rwlock_tryrdlock(NULL), EINVAL);
+
+    pthread_rwlock_t rwlock = 0;
+    TEST_ASSERT_EQUAL_INT(pthread_rwlock_tryrdlock(&rwlock), EINVAL);
+}
+
+TEST_CASE("tryrdlock fails on write-locked rwlock", "[pthread][rwlock]")
+{
+    pthread_rwlock_t rwlock;
+    TEST_ASSERT_EQUAL_INT(pthread_rwlock_init(&rwlock, NULL), 0);
+    TEST_ASSERT_EQUAL_INT(pthread_rwlock_wrlock(&rwlock), 0);
+
+    TEST_ASSERT_EQUAL_INT(pthread_rwlock_tryrdlock(&rwlock), EBUSY);
+
+    TEST_ASSERT_EQUAL_INT(pthread_rwlock_unlock(&rwlock), 0);
+    TEST_ASSERT_EQUAL_INT(pthread_rwlock_destroy(&rwlock), 0);
+}
+
+TEST_CASE("tryrdlock succeeds on read-locked rwlock", "[pthread][rwlock]")
+{
+    pthread_rwlock_t rwlock;
+    TEST_ASSERT_EQUAL_INT(pthread_rwlock_init(&rwlock, NULL), 0);
+    TEST_ASSERT_EQUAL_INT(pthread_rwlock_rdlock(&rwlock), 0);
+
+    TEST_ASSERT_EQUAL_INT(pthread_rwlock_tryrdlock(&rwlock), 0);
+
+    TEST_ASSERT_EQUAL_INT(pthread_rwlock_unlock(&rwlock), 0);
+    TEST_ASSERT_EQUAL_INT(pthread_rwlock_unlock(&rwlock), 0);
+    TEST_ASSERT_EQUAL_INT(pthread_rwlock_destroy(&rwlock), 0);
+}
+
+TEST_CASE("tryrdlock lock statically initialized lock", "[pthread][rwlock]")
+{
+    pthread_rwlock_t rwlock = PTHREAD_RWLOCK_INITIALIZER;
+
+    TEST_ASSERT_EQUAL_INT(pthread_rwlock_tryrdlock(&rwlock), 0);
+
+    TEST_ASSERT_EQUAL_INT(pthread_rwlock_unlock(&rwlock), 0);
+    TEST_ASSERT_EQUAL_INT(pthread_rwlock_destroy(&rwlock), 0);
+}
+
+TEST_CASE("trywrlock invalid param", "[pthread][rwlock]")
+{
+    TEST_ASSERT_EQUAL_INT(pthread_rwlock_trywrlock(NULL), EINVAL);
+
+    pthread_rwlock_t rwlock = 0;
+    TEST_ASSERT_EQUAL_INT(pthread_rwlock_trywrlock(&rwlock), EINVAL);
+}
+
+TEST_CASE("trywrlock fails on write-locked rwlock", "[pthread][rwlock]")
+{
+    pthread_rwlock_t rwlock;
+    TEST_ASSERT_EQUAL_INT(pthread_rwlock_init(&rwlock, NULL), 0);
+    TEST_ASSERT_EQUAL_INT(pthread_rwlock_wrlock(&rwlock), 0);
+
+    TEST_ASSERT_EQUAL_INT(pthread_rwlock_trywrlock(&rwlock), EBUSY);
+
+    TEST_ASSERT_EQUAL_INT(pthread_rwlock_unlock(&rwlock), 0);
+    TEST_ASSERT_EQUAL_INT(pthread_rwlock_destroy(&rwlock), 0);
+}
+
+TEST_CASE("trywrlock fails on read-locked rwlock", "[pthread][rwlock]")
+{
+    pthread_rwlock_t rwlock;
+    TEST_ASSERT_EQUAL_INT(pthread_rwlock_init(&rwlock, NULL), 0);
+    TEST_ASSERT_EQUAL_INT(pthread_rwlock_rdlock(&rwlock), 0);
+
+    TEST_ASSERT_EQUAL_INT(pthread_rwlock_trywrlock(&rwlock), EBUSY);
+
+    TEST_ASSERT_EQUAL_INT(pthread_rwlock_unlock(&rwlock), 0);
+    TEST_ASSERT_EQUAL_INT(pthread_rwlock_unlock(&rwlock), 0);
+    TEST_ASSERT_EQUAL_INT(pthread_rwlock_destroy(&rwlock), 0);
+}
+
+TEST_CASE("trywrlock lock statically initialized lock", "[pthread][rwlock]")
+{
+    pthread_rwlock_t rwlock = PTHREAD_RWLOCK_INITIALIZER;
+
+    TEST_ASSERT_EQUAL_INT(pthread_rwlock_trywrlock(&rwlock), 0);
+
+    TEST_ASSERT_EQUAL_INT(pthread_rwlock_unlock(&rwlock), 0);
+    TEST_ASSERT_EQUAL_INT(pthread_rwlock_destroy(&rwlock), 0);
+}

docs/en/api-reference/system/pthread.rst

@@ -123,18 +123,23 @@ In IDF, POSIX *unnamed* semaphores are implemented. The accessible API is descri
 * `sem_getvalue() <https://pubs.opengroup.org/onlinepubs/9699919799/functions/sem_getvalue.html>`_
 
 Read/Write Locks
-^^^^^^^^^^^^^^^^^^^
+^^^^^^^^^^^^^^^^
+The following API functions of the POSIX reader-writer locks specification are implemented:
+
+* `pthread_rwlock_init() <https://pubs.opengroup.org/onlinepubs/9699919799/functions/pthread_rwlock_init.html>`_
 
-* ``pthread_rwlock_init()``
   - The ``attr`` argument is not implemented and is ignored.
-* ``pthread_rwlock_destroy()``
-* ``pthread_rwlock_rdlock()``
-* ``pthread_rwlock_wrlock()``
-* ``pthread_rwlock_unlock()``
 
-Static initializer constant ``PTHREAD_RWLOCK_INITIALIZER`` is supported.
+* `pthread_rwlock_destroy() <https://pubs.opengroup.org/onlinepubs/9699919799/functions/pthread_rwlock_destroy.html>`_
+* `pthread_rwlock_rdlock() <https://pubs.opengroup.org/onlinepubs/9699919799/functions/pthread_rwlock_rdlock.html>`_
+* `pthread_rwlock_tryrdlock() <https://pubs.opengroup.org/onlinepubs/9699919799/functions/pthread_rwlock_tryrdlock.html>`_
+* `pthread_rwlock_wrlock() <https://pubs.opengroup.org/onlinepubs/9699919799/functions/pthread_rwlock_wrlock.html>`_
+* `pthread_rwlock_trywrlock() <https://pubs.opengroup.org/onlinepubs/9699919799/functions/pthread_rwlock_trywrlock.html>`_
+* `pthread_rwlock_unlock() <https://pubs.opengroup.org/onlinepubs/9699919799/functions/pthread_rwlock_unlock.html>`_
 
-.. note:: These functions can be called from tasks created using either pthread or FreeRTOS APIs
+The static initializer constant ``PTHREAD_RWLOCK_INITIALIZER`` is supported.
+
+.. note:: These functions can be called from tasks created using either pthread or FreeRTOS APIs.
 
 Thread-Specific Data
 ^^^^^^^^^^^^^^^^^^^^