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-rw-r--r--locks/win32/thread_rwlock.c165
1 files changed, 165 insertions, 0 deletions
diff --git a/locks/win32/thread_rwlock.c b/locks/win32/thread_rwlock.c
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+++ b/locks/win32/thread_rwlock.c
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+/* Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements. See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License. You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "apr.h"
+#include "apr_private.h"
+#include "apr_general.h"
+#include "apr_strings.h"
+#include "apr_arch_thread_rwlock.h"
+#include "apr_portable.h"
+
+static apr_status_t thread_rwlock_cleanup(void *data)
+{
+ apr_thread_rwlock_t *rwlock = data;
+
+ if (! CloseHandle(rwlock->read_event))
+ return apr_get_os_error();
+
+ if (! CloseHandle(rwlock->write_mutex))
+ return apr_get_os_error();
+
+ return APR_SUCCESS;
+}
+
+APR_DECLARE(apr_status_t)apr_thread_rwlock_create(apr_thread_rwlock_t **rwlock,
+ apr_pool_t *pool)
+{
+ *rwlock = apr_palloc(pool, sizeof(**rwlock));
+
+ (*rwlock)->pool = pool;
+ (*rwlock)->readers = 0;
+
+ if (! ((*rwlock)->read_event = CreateEvent(NULL, TRUE, FALSE, NULL))) {
+ *rwlock = NULL;
+ return apr_get_os_error();
+ }
+
+ if (! ((*rwlock)->write_mutex = CreateMutex(NULL, FALSE, NULL))) {
+ CloseHandle((*rwlock)->read_event);
+ *rwlock = NULL;
+ return apr_get_os_error();
+ }
+
+ apr_pool_cleanup_register(pool, *rwlock, thread_rwlock_cleanup,
+ apr_pool_cleanup_null);
+
+ return APR_SUCCESS;
+}
+
+static apr_status_t apr_thread_rwlock_rdlock_core(apr_thread_rwlock_t *rwlock,
+ DWORD milliseconds)
+{
+ DWORD code = WaitForSingleObject(rwlock->write_mutex, milliseconds);
+
+ if (code == WAIT_FAILED || code == WAIT_TIMEOUT)
+ return APR_FROM_OS_ERROR(code);
+
+ /* We've successfully acquired the writer mutex, we can't be locked
+ * for write, so it's OK to add the reader lock. The writer mutex
+ * doubles as race condition protection for the readers counter.
+ */
+ InterlockedIncrement(&rwlock->readers);
+
+ if (! ResetEvent(rwlock->read_event))
+ return apr_get_os_error();
+
+ if (! ReleaseMutex(rwlock->write_mutex))
+ return apr_get_os_error();
+
+ return APR_SUCCESS;
+}
+
+APR_DECLARE(apr_status_t) apr_thread_rwlock_rdlock(apr_thread_rwlock_t *rwlock)
+{
+ return apr_thread_rwlock_rdlock_core(rwlock, INFINITE);
+}
+
+APR_DECLARE(apr_status_t)
+apr_thread_rwlock_tryrdlock(apr_thread_rwlock_t *rwlock)
+{
+ return apr_thread_rwlock_rdlock_core(rwlock, 0);
+}
+
+static apr_status_t
+apr_thread_rwlock_wrlock_core(apr_thread_rwlock_t *rwlock, DWORD milliseconds)
+{
+ DWORD code = WaitForSingleObject(rwlock->write_mutex, milliseconds);
+
+ if (code == WAIT_FAILED || code == WAIT_TIMEOUT)
+ return APR_FROM_OS_ERROR(code);
+
+ /* We've got the writer lock but we have to wait for all readers to
+ * unlock before it's ok to use it.
+ */
+ if (rwlock->readers) {
+ /* Must wait for readers to finish before returning, unless this
+ * is an trywrlock (milliseconds == 0):
+ */
+ code = milliseconds
+ ? WaitForSingleObject(rwlock->read_event, milliseconds)
+ : WAIT_TIMEOUT;
+
+ if (code == WAIT_FAILED || code == WAIT_TIMEOUT) {
+ /* Unable to wait for readers to finish, release write lock: */
+ if (! ReleaseMutex(rwlock->write_mutex))
+ return apr_get_os_error();
+
+ return APR_FROM_OS_ERROR(code);
+ }
+ }
+
+ return APR_SUCCESS;
+}
+
+APR_DECLARE(apr_status_t) apr_thread_rwlock_wrlock(apr_thread_rwlock_t *rwlock)
+{
+ return apr_thread_rwlock_wrlock_core(rwlock, INFINITE);
+}
+
+APR_DECLARE(apr_status_t)apr_thread_rwlock_trywrlock(apr_thread_rwlock_t *rwlock)
+{
+ return apr_thread_rwlock_wrlock_core(rwlock, 0);
+}
+
+APR_DECLARE(apr_status_t) apr_thread_rwlock_unlock(apr_thread_rwlock_t *rwlock)
+{
+ apr_status_t rv = 0;
+
+ /* First, guess that we're unlocking a writer */
+ if (! ReleaseMutex(rwlock->write_mutex))
+ rv = apr_get_os_error();
+
+ if (rv == APR_FROM_OS_ERROR(ERROR_NOT_OWNER)) {
+ /* Nope, we must have a read lock */
+ if (rwlock->readers &&
+ ! InterlockedDecrement(&rwlock->readers) &&
+ ! SetEvent(rwlock->read_event)) {
+ rv = apr_get_os_error();
+ }
+ else {
+ rv = 0;
+ }
+ }
+
+ return rv;
+}
+
+APR_DECLARE(apr_status_t) apr_thread_rwlock_destroy(apr_thread_rwlock_t *rwlock)
+{
+ return apr_pool_cleanup_run(rwlock->pool, rwlock, thread_rwlock_cleanup);
+}
+
+APR_POOL_IMPLEMENT_ACCESSOR(thread_rwlock)