145 lines
3.7 KiB
C
145 lines
3.7 KiB
C
/****************************************************************************
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* libs/libc/pthread/pthread_rwlock_rdlock.c
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <stdint.h>
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#include <pthread.h>
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#include <errno.h>
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#include <debug.h>
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/****************************************************************************
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* Private Functions
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****************************************************************************/
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static void rdlock_cleanup(FAR void *arg)
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{
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FAR pthread_rwlock_t *rw_lock = (FAR pthread_rwlock_t *)arg;
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pthread_mutex_unlock(&rw_lock->lock);
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}
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static int tryrdlock(FAR pthread_rwlock_t *rw_lock)
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{
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int err;
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if (rw_lock->num_writers > 0 || rw_lock->write_in_progress)
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{
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err = EBUSY;
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}
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else if (rw_lock->num_readers == UINT_MAX)
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{
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err = EAGAIN;
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}
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else
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{
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rw_lock->num_readers++;
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err = OK;
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}
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return err;
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}
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: pthread_rwlock_rdlock
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*
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* Description:
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* Locks a read/write lock for reading
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*
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* Input Parameters:
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* None
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*
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* Returned Value:
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* None
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*
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* Assumptions:
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*
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****************************************************************************/
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int pthread_rwlock_tryrdlock(FAR pthread_rwlock_t *rw_lock)
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{
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int err = pthread_mutex_trylock(&rw_lock->lock);
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if (err != 0)
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{
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return err;
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}
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err = tryrdlock(rw_lock);
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pthread_mutex_unlock(&rw_lock->lock);
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return err;
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}
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int pthread_rwlock_clockrdlock(FAR pthread_rwlock_t *rw_lock,
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clockid_t clockid,
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FAR const struct timespec *ts)
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{
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int err = pthread_mutex_lock(&rw_lock->lock);
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if (err != 0)
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{
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return err;
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}
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pthread_cleanup_push(&rdlock_cleanup, rw_lock);
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while ((err = tryrdlock(rw_lock)) == EBUSY)
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{
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if (ts != NULL)
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{
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err = pthread_cond_clockwait(&rw_lock->cv, &rw_lock->lock,
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clockid, ts);
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}
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else
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{
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err = pthread_cond_wait(&rw_lock->cv, &rw_lock->lock);
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}
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if (err != 0)
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{
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break;
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}
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}
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pthread_cleanup_pop(0);
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pthread_mutex_unlock(&rw_lock->lock);
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return err;
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}
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int pthread_rwlock_timedrdlock(FAR pthread_rwlock_t *rw_lock,
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FAR const struct timespec *ts)
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{
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return pthread_rwlock_clockrdlock(rw_lock, CLOCK_REALTIME, ts);
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}
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int pthread_rwlock_rdlock(FAR pthread_rwlock_t * rw_lock)
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{
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return pthread_rwlock_timedrdlock(rw_lock, NULL);
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}
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