rt-thread-official/components/pthreads/pthread_rwlock.c

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/*
* File : pthread_rwlock.c
* This file is part of RT-Thread RTOS
* COPYRIGHT (C) 2006 - 2010, RT-Thread Development Team
*
* 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.
*
* Change Logs:
* Date Author Notes
* 2010-10-26 Bernard the first version
*/
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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)
return EINVAL;
*attr = PTHREAD_PROCESS_PRIVATE;
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return 0;
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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)
return EINVAL;
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return 0;
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}
RTM_EXPORT(pthread_rwlockattr_destroy);
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int pthread_rwlockattr_getpshared(const pthread_rwlockattr_t *attr,
int *pshared)
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{
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if (!attr || !pshared)
return EINVAL;
*pshared = PTHREAD_PROCESS_PRIVATE;
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return 0;
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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)
return EINVAL;
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return 0;
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}
RTM_EXPORT(pthread_rwlockattr_setpshared);
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int pthread_rwlock_init(pthread_rwlock_t *rwlock,
const pthread_rwlockattr_t *attr)
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{
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if (!rwlock)
return EINVAL;
rwlock->attr = PTHREAD_PROCESS_PRIVATE;
pthread_mutex_init(&(rwlock->rw_mutex), NULL);
pthread_cond_init(&(rwlock->rw_condreaders), NULL);
pthread_cond_init(&(rwlock->rw_condwriters), NULL);
rwlock->rw_nwaitwriters = 0;
rwlock->rw_nwaitreaders = 0;
rwlock->rw_refcount = 0;
return 0;
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}
RTM_EXPORT(pthread_rwlock_init);
int pthread_rwlock_destroy (pthread_rwlock_t *rwlock)
{
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int result;
if (!rwlock)
return EINVAL;
if (rwlock->attr == -1)
return 0; /* rwlock is not initialized */
if ( (result = pthread_mutex_lock(&rwlock->rw_mutex)) != 0)
return(result);
if (rwlock->rw_refcount != 0 ||
rwlock->rw_nwaitreaders != 0 ||
rwlock->rw_nwaitwriters != 0)
{
result = EBUSY;
return result;
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}
else
{
/* check whether busy */
result = rt_sem_trytake(&(rwlock->rw_condreaders.sem));
if (result == RT_EOK)
{
result = rt_sem_trytake(&(rwlock->rw_condwriters.sem));
if (result == RT_EOK)
{
rt_sem_release(&(rwlock->rw_condreaders.sem));
rt_sem_release(&(rwlock->rw_condwriters.sem));
pthread_cond_destroy(&rwlock->rw_condreaders);
pthread_cond_destroy(&rwlock->rw_condwriters);
}
else
{
rt_sem_release(&(rwlock->rw_condreaders.sem));
result = EBUSY;
}
}
else
result = EBUSY;
}
pthread_mutex_unlock(&rwlock->rw_mutex);
if (result == 0)
pthread_mutex_destroy(&rwlock->rw_mutex);
return result;
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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;
if (!rwlock)
return EINVAL;
if (rwlock->attr == -1)
pthread_rwlock_init(rwlock, NULL);
if ((result = pthread_mutex_lock(&rwlock->rw_mutex)) != 0)
return(result);
/* give preference to waiting writers */
while (rwlock->rw_refcount < 0 || rwlock->rw_nwaitwriters > 0)
{
rwlock->rw_nwaitreaders++;
/* rw_mutex will be released when waiting for rw_condreaders */
result = pthread_cond_wait(&rwlock->rw_condreaders, &rwlock->rw_mutex);
/* rw_mutex should have been taken again when returned from waiting */
rwlock->rw_nwaitreaders--;
if (result != 0) /* wait error */
break;
}
/* another reader has a read lock */
if (result == 0)
rwlock->rw_refcount++;
pthread_mutex_unlock(&rwlock->rw_mutex);
return (result);
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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)
return EINVAL;
if (rwlock->attr == -1)
pthread_rwlock_init(rwlock, NULL);
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if ((result = pthread_mutex_lock(&rwlock->rw_mutex)) != 0)
return(result);
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if (rwlock->rw_refcount < 0 || rwlock->rw_nwaitwriters > 0)
result = EBUSY; /* held by a writer or waiting writers */
else
rwlock->rw_refcount++; /* increment count of reader locks */
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pthread_mutex_unlock(&rwlock->rw_mutex);
return(result);
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}
RTM_EXPORT(pthread_rwlock_tryrdlock);
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int pthread_rwlock_timedrdlock(pthread_rwlock_t *rwlock,
const struct timespec *abstime)
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{
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int result;
if (!rwlock)
return EINVAL;
if (rwlock->attr == -1)
pthread_rwlock_init(rwlock, NULL);
if ( (result = pthread_mutex_lock(&rwlock->rw_mutex)) != 0)
return(result);
/* give preference to waiting writers */
while (rwlock->rw_refcount < 0 || rwlock->rw_nwaitwriters > 0)
{
rwlock->rw_nwaitreaders++;
/* rw_mutex will be released when waiting for rw_condreaders */
result = pthread_cond_timedwait(&rwlock->rw_condreaders, &rwlock->rw_mutex, abstime);
/* rw_mutex should have been taken again when returned from waiting */
rwlock->rw_nwaitreaders--;
if (result != 0)
break;
}
/* another reader has a read lock */
if (result == 0)
rwlock->rw_refcount++;
pthread_mutex_unlock(&rwlock->rw_mutex);
return (result);
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}
RTM_EXPORT(pthread_rwlock_timedrdlock);
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int pthread_rwlock_timedwrlock(pthread_rwlock_t *rwlock,
const struct timespec *abstime)
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{
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int result;
if (!rwlock)
return EINVAL;
if (rwlock->attr == -1)
pthread_rwlock_init(rwlock, NULL);
if ((result = pthread_mutex_lock(&rwlock->rw_mutex)) != 0)
return(result);
while (rwlock->rw_refcount != 0)
{
rwlock->rw_nwaitwriters++;
/* rw_mutex will be released when waiting for rw_condwriters */
result = pthread_cond_timedwait(&rwlock->rw_condwriters, &rwlock->rw_mutex, abstime);
/* rw_mutex should have been taken again when returned from waiting */
rwlock->rw_nwaitwriters--;
if (result != 0)
break;
}
if (result == 0)
rwlock->rw_refcount = -1;
pthread_mutex_unlock(&rwlock->rw_mutex);
return(result);
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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;
if (!rwlock)
return EINVAL;
if (rwlock->attr == -1)
pthread_rwlock_init(rwlock, NULL);
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if ((result = pthread_mutex_lock(&rwlock->rw_mutex)) != 0)
return(result);
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if (rwlock->rw_refcount != 0)
result = EBUSY; /* held by either writer or reader(s) */
else
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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}
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;
if (!rwlock)
return EINVAL;
if (rwlock->attr == -1)
pthread_rwlock_init(rwlock, NULL);
if ( (result = pthread_mutex_lock(&rwlock->rw_mutex)) != 0)
return(result);
if (rwlock->rw_refcount > 0)
rwlock->rw_refcount--; /* releasing a reader */
else if (rwlock->rw_refcount == -1)
rwlock->rw_refcount = 0; /* releasing a writer */
/* give preference to waiting writers over waiting readers */
if (rwlock->rw_nwaitwriters > 0)
{
if (rwlock->rw_refcount == 0)
result = pthread_cond_signal(&rwlock->rw_condwriters);
}
else if (rwlock->rw_nwaitreaders > 0)
{
result = pthread_cond_broadcast(&rwlock->rw_condreaders);
}
pthread_mutex_unlock(&rwlock->rw_mutex);
return(result);
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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;
if (!rwlock)
return EINVAL;
if (rwlock->attr == -1)
pthread_rwlock_init(rwlock, NULL);
if ((result = pthread_mutex_lock(&rwlock->rw_mutex)) != 0)
return(result);
while (rwlock->rw_refcount != 0)
{
rwlock->rw_nwaitwriters++;
/* rw_mutex will be released when waiting for rw_condwriters */
result = pthread_cond_wait(&rwlock->rw_condwriters, &rwlock->rw_mutex);
/* rw_mutex should have been taken again when returned from waiting */
rwlock->rw_nwaitwriters--;
if (result != 0)
break;
}
if (result == 0)
rwlock->rw_refcount = -1;
pthread_mutex_unlock(&rwlock->rw_mutex);
return(result);
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}
RTM_EXPORT(pthread_rwlock_wrlock);