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#include <pthread.h> 19#include <stdlib.h> 20#include <stdio.h> 21 22/* #define RWDEBUG 1 */ 23#include "config.h" 24#include "rwlock.h" 25 26void init_rwlock(struct rwlock *rw) 27{ 28 rw->n_readers = 0; 29 pthread_mutex_init(&rw->plock, NULL); 30 pthread_cond_init(&rw->pcond, NULL); 31#ifdef RWDEBUG 32 rw->n_write_waiting = 0; 33 rw->n_read_waiting = 0; 34 rw->writer_tid = -1; 35#endif 36} 37 38void rw_lock_read(struct rwlock *rw) 39{ 40 pthread_mutex_lock(&rw->plock); 41#ifdef RWDEBUG 42 rw->n_read_waiting++; 43#endif 44 while (rw->n_readers < 0) 45 pthread_cond_wait(&rw->pcond, &rw->plock); 46 rw->n_readers++; 47#ifdef RWDEBUG 48 rw->n_read_waiting--; 49#endif 50 pthread_mutex_unlock(&rw->plock); 51} 52 53void rw_lock_write(struct rwlock *rw) 54{ 55 pthread_mutex_lock(&rw->plock); 56#ifdef RWDEBUG 57 rw->n_write_waiting++; 58#endif 59 while (rw->n_readers != 0) 60 pthread_cond_wait(&rw->pcond, &rw->plock); 61 rw->n_readers = -1; 62#ifdef RWDEBUG 63 rw->n_write_waiting--; 64 rw->writer_tid = (int)pthread_self(); 65#endif 66 pthread_mutex_unlock(&rw->plock); 67 68} 69 70void rw_unlock_read(struct rwlock *rw) 71{ 72 pthread_mutex_lock(&rw->plock); 73 rw->n_readers -= 1; 74 pthread_cond_signal(&rw->pcond); 75 pthread_mutex_unlock(&rw->plock); 76} 77 78void rw_unlock_write(struct rwlock *rw) 79{ 80 pthread_mutex_lock(&rw->plock); 81 rw->n_readers = 0; 82 pthread_cond_broadcast(&rw->pcond); 83 pthread_mutex_unlock(&rw->plock); 84} 85 86int rw_trylock_read(struct rwlock *rw) 87{ 88 int ret = 1; 89 pthread_mutex_lock(&rw->plock); 90 if (rw->n_readers >= 0) { 91 rw->n_readers++; 92 ret = 0; 93 } 94 pthread_mutex_unlock(&rw->plock); 95 return ret; 96} 97 98int rw_trylock_write(struct rwlock *rw) 99{ 100 int ret = 1; 101 pthread_mutex_lock(&rw->plock); 102 if (rw->n_readers == 0) { 103 ret = 0; 104 rw->n_readers = -1; 105 } 106 pthread_mutex_unlock(&rw->plock); 107 return ret; 108} 109