355 lines
9.4 KiB
C
355 lines
9.4 KiB
C
/*
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* File : pthread_rwlock.c
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* This file is part of RT-Thread RTOS
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* COPYRIGHT (C) 2006 - 2010, RT-Thread Development Team
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Change Logs:
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* Date Author Notes
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* 2010-10-26 Bernard the first version
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*/
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#include <pthread.h>
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int pthread_rwlockattr_init(pthread_rwlockattr_t *attr)
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{
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if (!attr)
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return EINVAL;
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*attr = PTHREAD_PROCESS_PRIVATE;
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return 0;
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}
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RTM_EXPORT(pthread_rwlockattr_init);
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int pthread_rwlockattr_destroy(pthread_rwlockattr_t *attr)
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{
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if (!attr)
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return EINVAL;
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return 0;
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}
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RTM_EXPORT(pthread_rwlockattr_destroy);
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int pthread_rwlockattr_getpshared(const pthread_rwlockattr_t *attr,
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int *pshared)
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{
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if (!attr || !pshared)
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return EINVAL;
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*pshared = PTHREAD_PROCESS_PRIVATE;
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return 0;
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}
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RTM_EXPORT(pthread_rwlockattr_getpshared);
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int pthread_rwlockattr_setpshared(pthread_rwlockattr_t *attr, int pshared)
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{
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if (!attr || pshared != PTHREAD_PROCESS_PRIVATE)
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return EINVAL;
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return 0;
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}
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RTM_EXPORT(pthread_rwlockattr_setpshared);
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int pthread_rwlock_init(pthread_rwlock_t *rwlock,
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const pthread_rwlockattr_t *attr)
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{
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if (!rwlock)
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return EINVAL;
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rwlock->attr = PTHREAD_PROCESS_PRIVATE;
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pthread_mutex_init(&(rwlock->rw_mutex), NULL);
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pthread_cond_init(&(rwlock->rw_condreaders), NULL);
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pthread_cond_init(&(rwlock->rw_condwriters), NULL);
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rwlock->rw_nwaitwriters = 0;
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rwlock->rw_nwaitreaders = 0;
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rwlock->rw_refcount = 0;
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return 0;
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}
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RTM_EXPORT(pthread_rwlock_init);
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int pthread_rwlock_destroy (pthread_rwlock_t *rwlock)
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{
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int result;
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if (!rwlock)
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return EINVAL;
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if (rwlock->attr == -1)
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return 0; /* rwlock is not initialized */
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if ( (result = pthread_mutex_lock(&rwlock->rw_mutex)) != 0)
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return(result);
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if (rwlock->rw_refcount != 0 ||
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rwlock->rw_nwaitreaders != 0 ||
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rwlock->rw_nwaitwriters != 0)
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{
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result = EBUSY;
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return result;
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}
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else
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{
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/* check whether busy */
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result = rt_sem_trytake(&(rwlock->rw_condreaders.sem));
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if (result == RT_EOK)
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{
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result = rt_sem_trytake(&(rwlock->rw_condwriters.sem));
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if (result == RT_EOK)
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{
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rt_sem_release(&(rwlock->rw_condreaders.sem));
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rt_sem_release(&(rwlock->rw_condwriters.sem));
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pthread_cond_destroy(&rwlock->rw_condreaders);
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pthread_cond_destroy(&rwlock->rw_condwriters);
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}
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else
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{
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rt_sem_release(&(rwlock->rw_condreaders.sem));
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result = EBUSY;
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}
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}
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else
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result = EBUSY;
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}
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pthread_mutex_unlock(&rwlock->rw_mutex);
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if (result == 0)
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pthread_mutex_destroy(&rwlock->rw_mutex);
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return result;
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}
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RTM_EXPORT(pthread_rwlock_destroy);
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int pthread_rwlock_rdlock(pthread_rwlock_t *rwlock)
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{
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int result;
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if (!rwlock)
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return EINVAL;
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if (rwlock->attr == -1)
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pthread_rwlock_init(rwlock, NULL);
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if ((result = pthread_mutex_lock(&rwlock->rw_mutex)) != 0)
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return(result);
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/* give preference to waiting writers */
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while (rwlock->rw_refcount < 0 || rwlock->rw_nwaitwriters > 0)
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{
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rwlock->rw_nwaitreaders++;
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/* rw_mutex will be released when waiting for rw_condreaders */
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result = pthread_cond_wait(&rwlock->rw_condreaders, &rwlock->rw_mutex);
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/* rw_mutex should have been taken again when returned from waiting */
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rwlock->rw_nwaitreaders--;
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if (result != 0) /* wait error */
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break;
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}
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/* another reader has a read lock */
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if (result == 0)
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rwlock->rw_refcount++;
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pthread_mutex_unlock(&rwlock->rw_mutex);
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return (result);
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}
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RTM_EXPORT(pthread_rwlock_rdlock);
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int pthread_rwlock_tryrdlock(pthread_rwlock_t *rwlock)
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{
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int result;
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if (!rwlock)
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return EINVAL;
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if (rwlock->attr == -1)
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pthread_rwlock_init(rwlock, NULL);
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if ((result = pthread_mutex_lock(&rwlock->rw_mutex)) != 0)
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return(result);
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if (rwlock->rw_refcount < 0 || rwlock->rw_nwaitwriters > 0)
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result = EBUSY; /* held by a writer or waiting writers */
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else
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rwlock->rw_refcount++; /* increment count of reader locks */
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pthread_mutex_unlock(&rwlock->rw_mutex);
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return(result);
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}
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RTM_EXPORT(pthread_rwlock_tryrdlock);
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int pthread_rwlock_timedrdlock(pthread_rwlock_t *rwlock,
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const struct timespec *abstime)
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{
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int result;
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if (!rwlock)
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return EINVAL;
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if (rwlock->attr == -1)
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pthread_rwlock_init(rwlock, NULL);
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if ( (result = pthread_mutex_lock(&rwlock->rw_mutex)) != 0)
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return(result);
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/* give preference to waiting writers */
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while (rwlock->rw_refcount < 0 || rwlock->rw_nwaitwriters > 0)
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{
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rwlock->rw_nwaitreaders++;
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/* rw_mutex will be released when waiting for rw_condreaders */
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result = pthread_cond_timedwait(&rwlock->rw_condreaders, &rwlock->rw_mutex, abstime);
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/* rw_mutex should have been taken again when returned from waiting */
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rwlock->rw_nwaitreaders--;
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if (result != 0)
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break;
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}
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/* another reader has a read lock */
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if (result == 0)
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rwlock->rw_refcount++;
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pthread_mutex_unlock(&rwlock->rw_mutex);
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return (result);
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}
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RTM_EXPORT(pthread_rwlock_timedrdlock);
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int pthread_rwlock_timedwrlock(pthread_rwlock_t *rwlock,
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const struct timespec *abstime)
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{
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int result;
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if (!rwlock)
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return EINVAL;
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if (rwlock->attr == -1)
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pthread_rwlock_init(rwlock, NULL);
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if ((result = pthread_mutex_lock(&rwlock->rw_mutex)) != 0)
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return(result);
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while (rwlock->rw_refcount != 0)
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{
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rwlock->rw_nwaitwriters++;
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/* rw_mutex will be released when waiting for rw_condwriters */
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result = pthread_cond_timedwait(&rwlock->rw_condwriters, &rwlock->rw_mutex, abstime);
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/* rw_mutex should have been taken again when returned from waiting */
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rwlock->rw_nwaitwriters--;
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if (result != 0)
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break;
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}
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if (result == 0)
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rwlock->rw_refcount = -1;
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pthread_mutex_unlock(&rwlock->rw_mutex);
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return(result);
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}
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RTM_EXPORT(pthread_rwlock_timedwrlock);
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int pthread_rwlock_trywrlock(pthread_rwlock_t *rwlock)
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{
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int result;
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if (!rwlock)
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return EINVAL;
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if (rwlock->attr == -1)
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pthread_rwlock_init(rwlock, NULL);
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if ((result = pthread_mutex_lock(&rwlock->rw_mutex)) != 0)
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return(result);
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if (rwlock->rw_refcount != 0)
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result = EBUSY; /* held by either writer or reader(s) */
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else
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rwlock->rw_refcount = -1; /* available, indicate a writer has it */
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pthread_mutex_unlock(&rwlock->rw_mutex);
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return(result);
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}
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RTM_EXPORT(pthread_rwlock_trywrlock);
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int pthread_rwlock_unlock(pthread_rwlock_t *rwlock)
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{
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int result;
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if (!rwlock)
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return EINVAL;
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if (rwlock->attr == -1)
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pthread_rwlock_init(rwlock, NULL);
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if ( (result = pthread_mutex_lock(&rwlock->rw_mutex)) != 0)
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return(result);
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if (rwlock->rw_refcount > 0)
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rwlock->rw_refcount--; /* releasing a reader */
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else if (rwlock->rw_refcount == -1)
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rwlock->rw_refcount = 0; /* releasing a writer */
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/* give preference to waiting writers over waiting readers */
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if (rwlock->rw_nwaitwriters > 0)
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{
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if (rwlock->rw_refcount == 0)
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result = pthread_cond_signal(&rwlock->rw_condwriters);
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}
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else if (rwlock->rw_nwaitreaders > 0)
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{
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result = pthread_cond_broadcast(&rwlock->rw_condreaders);
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}
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pthread_mutex_unlock(&rwlock->rw_mutex);
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return(result);
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}
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RTM_EXPORT(pthread_rwlock_unlock);
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int pthread_rwlock_wrlock(pthread_rwlock_t *rwlock)
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{
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int result;
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if (!rwlock)
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return EINVAL;
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if (rwlock->attr == -1)
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pthread_rwlock_init(rwlock, NULL);
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if ((result = pthread_mutex_lock(&rwlock->rw_mutex)) != 0)
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return(result);
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while (rwlock->rw_refcount != 0)
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{
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rwlock->rw_nwaitwriters++;
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/* rw_mutex will be released when waiting for rw_condwriters */
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result = pthread_cond_wait(&rwlock->rw_condwriters, &rwlock->rw_mutex);
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/* rw_mutex should have been taken again when returned from waiting */
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rwlock->rw_nwaitwriters--;
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if (result != 0)
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break;
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}
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if (result == 0)
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rwlock->rw_refcount = -1;
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pthread_mutex_unlock(&rwlock->rw_mutex);
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return(result);
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}
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RTM_EXPORT(pthread_rwlock_wrlock);
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