1 /* 2 * Copyright (c) International Business Machines Corp., 2001-2004 3 * 4 * This program is free software; you can redistribute it and/or modify 5 * it under the terms of the GNU General Public License as published by 6 * the Free Software Foundation; either version 2 of the License, or 7 * (at your option) any later version. 8 * 9 * This program is distributed in the hope that it will be useful, 10 * but WITHOUT ANY WARRANTY; without even the implied warranty of 11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See 12 * the GNU General Public License for more details. 13 * 14 * You should have received a copy of the GNU General Public License 15 * along with this program; if not, write to the Free Software 16 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA 17 */ 18 #ifndef _RWLOCK_H 19 #define _RWLOCK_H 20 21 #include <pthread.h> 22 23 /* #define RWDEBUG 1 */ 24 25 /* n_readers >= 0 means 0 or more readers */ 26 /* n_readers < 0 means a writer */ 27 struct rwlock { 28 pthread_mutex_t plock; 29 int n_readers; 30 pthread_cond_t pcond; 31 #ifdef RWDEBUG 32 int writer_tid; 33 int n_read_waiting; 34 int n_write_waiting; 35 #endif 36 }; 37 38 void init_rwlock(struct rwlock *rw); 39 40 void rw_lock_read(struct rwlock *rw); 41 void rw_lock_write(struct rwlock *rw); 42 43 void rw_unlock_read(struct rwlock *rw); 44 void rw_unlock_write(struct rwlock *rw); 45 46 int rw_trylock_read(struct rwlock *rw); 47 int rw_trylock_write(struct rwlock *rw); 48 49 50 51 #endif 52