/* 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. */ #ifndef APR_THREAD_COND_H #define APR_THREAD_COND_H /** * @file apr_thread_cond.h * @brief APR Condition Variable Routines */ #include "apr.h" #include "apr_pools.h" #include "apr_errno.h" #include "apr_time.h" #include "apr_thread_mutex.h" #ifdef __cplusplus extern "C" { #endif /* __cplusplus */ #if APR_HAS_THREADS || defined(DOXYGEN) /** * @defgroup apr_thread_cond Condition Variable Routines * @ingroup APR * @{ */ /** Opaque structure for thread condition variables */ typedef struct apr_thread_cond_t apr_thread_cond_t; /** * Note: destroying a condition variable (or likewise, destroying or * clearing the pool from which a condition variable was allocated) if * any threads are blocked waiting on it gives undefined results. */ /** * Create and initialize a condition variable that can be used to signal * and schedule threads in a single process. * @param cond the memory address where the newly created condition variable * will be stored. * @param pool the pool from which to allocate the condition. */ APR_DECLARE(apr_status_t) apr_thread_cond_create(apr_thread_cond_t **cond, apr_pool_t *pool); /** * Put the active calling thread to sleep until signaled to wake up. Each * condition variable must be associated with a mutex, and that mutex must * be locked before calling this function, or the behavior will be * undefined. As the calling thread is put to sleep, the given mutex * will be simultaneously released; and as this thread wakes up the lock * is again simultaneously acquired. * @param cond the condition variable on which to block. * @param mutex the mutex that must be locked upon entering this function, * is released while the thread is asleep, and is again acquired before * returning from this function. * @remark Spurious wakeups may occur. Before and after every call to wait on * a condition variable, the caller should test whether the condition is already * met. */ APR_DECLARE(apr_status_t) apr_thread_cond_wait(apr_thread_cond_t *cond, apr_thread_mutex_t *mutex); /** * Put the active calling thread to sleep until signaled to wake up or * the timeout is reached. Each condition variable must be associated * with a mutex, and that mutex must be locked before calling this * function, or the behavior will be undefined. As the calling thread * is put to sleep, the given mutex will be simultaneously released; * and as this thread wakes up the lock is again simultaneously acquired. * @param cond the condition variable on which to block. * @param mutex the mutex that must be locked upon entering this function, * is released while the thread is asleep, and is again acquired before * returning from this function. * @param timeout The amount of time in microseconds to wait. This is * a maximum, not a minimum. If the condition is signaled, we * will wake up before this time, otherwise the error APR_TIMEUP * is returned. */ APR_DECLARE(apr_status_t) apr_thread_cond_timedwait(apr_thread_cond_t *cond, apr_thread_mutex_t *mutex, apr_interval_time_t timeout); /** * Signals a single thread, if one exists, that is blocking on the given * condition variable. That thread is then scheduled to wake up and acquire * the associated mutex. Although it is not required, if predictable scheduling * is desired, that mutex must be locked while calling this function. * @param cond the condition variable on which to produce the signal. * @remark If no threads are waiting on the condition variable, nothing happens. */ APR_DECLARE(apr_status_t) apr_thread_cond_signal(apr_thread_cond_t *cond); /** * Signals all threads blocking on the given condition variable. * Each thread that was signaled is then scheduled to wake up and acquire * the associated mutex. This will happen in a serialized manner. * @param cond the condition variable on which to produce the broadcast. * @remark If no threads are waiting on the condition variable, nothing happens. */ APR_DECLARE(apr_status_t) apr_thread_cond_broadcast(apr_thread_cond_t *cond); /** * Destroy the condition variable and free the associated memory. * @param cond the condition variable to destroy. */ APR_DECLARE(apr_status_t) apr_thread_cond_destroy(apr_thread_cond_t *cond); /** * Get the pool used by this thread_cond. * @return apr_pool_t the pool */ APR_POOL_DECLARE_ACCESSOR(thread_cond); #endif /* APR_HAS_THREADS */ /** @} */ #ifdef __cplusplus } #endif #endif /* ! APR_THREAD_COND_H */