diff options
Diffstat (limited to 'locks/win32/thread_rwlock.c')
| -rw-r--r-- | locks/win32/thread_rwlock.c | 165 |
1 files changed, 165 insertions, 0 deletions
diff --git a/locks/win32/thread_rwlock.c b/locks/win32/thread_rwlock.c new file mode 100644 index 0000000..fd9d579 --- /dev/null +++ b/locks/win32/thread_rwlock.c @@ -0,0 +1,165 @@ +/* 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) |