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 26 void 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 38 void 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 53 void 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 70 void 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 78 void 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 86 int 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 98 int 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
