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For more * information on the Apache Software Foundation, please see * . */ #ifndef APR_THREAD_RWLOCK_H #define APR_THREAD_RWLOCK_H #include "apr.h" #include "apr_pools.h" #include "apr_errno.h" #ifdef __cplusplus extern "C" { #endif /* __cplusplus */ #if APR_HAS_THREADS /** * @file apr_thread_rwlock.h * @brief APR Thread RWLock Routines */ /** * @defgroup APR_ThreadRWLock Thread RWLock Routines * @ingroup APR * @{ */ typedef struct apr_thread_rwlock_t apr_thread_rwlock_t; /** * Create and initialize a read-write lock that can be used to synchronize * threads. * @param rwlock the memory address where the newly created readwrite lock * will be stored. * @param pool the pool from which to allocate the mutex. */ APR_DECLARE(apr_status_t) apr_thread_rwlock_create(apr_thread_rwlock_t **rwlock, apr_pool_t *pool); /** * Acquire a shared-read lock on the given read-write lock. This will allow * multiple threads to enter the same critical section while they have acquired * the read lock. * @param rwlock the read-write lock on which to acquire the shared read. */ APR_DECLARE(apr_status_t) apr_thread_rwlock_rdlock(apr_thread_rwlock_t *rwlock); /** * Attempt to acquire the shread-read lock on the given read-write lock. This * is the same as apr_thread_rwlock_rdlock(), only that the funtion fails * if there is another thread holding the write lock, or if there are any * write threads blocking on the lock. If the function failes for this case, * APR_EBUSY will be returned. Note: it is important that the * APR_STATUS_IS_EBUSY(s) macro be used to determine if the return value was * APR_EBUSY, for portability reasons. * @param rwlock the rwlock on which to attempt the shared read. */ APR_DECLARE(apr_status_t) apr_thread_rwlock_tryrdlock(apr_thread_rwlock_t *rwlock); /** * Acquire an exclusive-write lock on the given read-write lock. This will * allow only one single thread to enter the critical sections. If there * are any threads currently holding thee read-lock, this thread is put to * sleep until it can have exclusive access to the lock. * @param rwlock the read-write lock on which to acquire the exclusive write. */ APR_DECLARE(apr_status_t) apr_thread_rwlock_wrlock(apr_thread_rwlock_t *rwlock); /** * Attempt to acquire the exclusive-write lock on the given read-write lock. * This is the same as apr_thread_rwlock_wrlock(), only that the funtion fails * if there is any other thread holding the lock (for reading or writing), * in which case the function will return APR_EBUSY. Note: it is important * that the APR_STATUS_IS_EBUSY(s) macro be used to determine if the return * value was APR_EBUSY, for portability reasons. * @param rwlock the rwlock on which to attempt the exclusive write. */ APR_DECLARE(apr_status_t) apr_thread_rwlock_trywrlock(apr_thread_rwlock_t *rwlock); /** * Release either the read or write lock currently held by the calling thread * associated with the given read-write lock. * @param rwlock the read-write lock rom which to release the lock. */ APR_DECLARE(apr_status_t) apr_thread_rwlock_unlock(apr_thread_rwlock_t *rwlock); /** * Destroy the read-write lock and free the associated memory. * @param rwlock the rwlock to destroy. */ APR_DECLARE(apr_status_t) apr_thread_rwlock_destroy(apr_thread_rwlock_t *rwlock); /** * Get the pool used by this thread_rwlock. * @return apr_pool_t the pool */ APR_POOL_DECLARE_ACCESSOR(thread_rwlock); #endif /* APR_HAS_THREADS */ #ifdef __cplusplus } #endif #endif /* ! APR_THREAD_RWLOCK_H */