| /* |
| * Copyright (c) International Business Machines Corp., 2001-2004 |
| * |
| * This program is free software; you can redistribute it and/or modify |
| * it under the terms of the GNU General Public License as published by |
| * the Free Software Foundation; either version 2 of the License, or |
| * (at your option) any later version. |
| * |
| * This program is distributed in the hope that it will be useful, |
| * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See |
| * the GNU General Public License for more details. |
| * |
| * You should have received a copy of the GNU General Public License |
| * along with this program; if not, write to the Free Software |
| * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
| */ |
| #include <pthread.h> |
| #include <stdlib.h> |
| #include <stdio.h> |
| |
| /* #define RWDEBUG 1 */ |
| #include "config.h" |
| #include "rwlock.h" |
| |
| void init_rwlock(struct rwlock *rw) |
| { |
| rw->n_readers = 0; |
| pthread_mutex_init(&rw->plock, NULL); |
| pthread_cond_init(&rw->pcond, NULL); |
| #ifdef RWDEBUG |
| rw->n_write_waiting = 0; |
| rw->n_read_waiting = 0; |
| rw->writer_tid = -1; |
| #endif |
| } |
| |
| void rw_lock_read(struct rwlock *rw) |
| { |
| pthread_mutex_lock(&rw->plock); |
| #ifdef RWDEBUG |
| rw->n_read_waiting++; |
| #endif |
| while (rw->n_readers < 0) |
| pthread_cond_wait(&rw->pcond, &rw->plock); |
| rw->n_readers++; |
| #ifdef RWDEBUG |
| rw->n_read_waiting--; |
| #endif |
| pthread_mutex_unlock(&rw->plock); |
| } |
| |
| void rw_lock_write(struct rwlock *rw) |
| { |
| pthread_mutex_lock(&rw->plock); |
| #ifdef RWDEBUG |
| rw->n_write_waiting++; |
| #endif |
| while (rw->n_readers != 0) |
| pthread_cond_wait(&rw->pcond, &rw->plock); |
| rw->n_readers = -1; |
| #ifdef RWDEBUG |
| rw->n_write_waiting--; |
| rw->writer_tid = (int)pthread_self(); |
| #endif |
| pthread_mutex_unlock(&rw->plock); |
| |
| } |
| |
| void rw_unlock_read(struct rwlock *rw) |
| { |
| pthread_mutex_lock(&rw->plock); |
| rw->n_readers -= 1; |
| pthread_cond_signal(&rw->pcond); |
| pthread_mutex_unlock(&rw->plock); |
| } |
| |
| void rw_unlock_write(struct rwlock *rw) |
| { |
| pthread_mutex_lock(&rw->plock); |
| rw->n_readers = 0; |
| pthread_cond_broadcast(&rw->pcond); |
| pthread_mutex_unlock(&rw->plock); |
| } |
| |
| int rw_trylock_read(struct rwlock *rw) |
| { |
| int ret = 1; |
| pthread_mutex_lock(&rw->plock); |
| if (rw->n_readers >= 0) { |
| rw->n_readers++; |
| ret = 0; |
| } |
| pthread_mutex_unlock(&rw->plock); |
| return ret; |
| } |
| |
| int rw_trylock_write(struct rwlock *rw) |
| { |
| int ret = 1; |
| pthread_mutex_lock(&rw->plock); |
| if (rw->n_readers == 0) { |
| ret = 0; |
| rw->n_readers = -1; |
| } |
| pthread_mutex_unlock(&rw->plock); |
| return ret; |
| } |