a48c784cc4
A mutex may be configured with rather exotic options such as recursive, unsafe, etc. The availability of these mutex options is controlled by configuation settings. When each option is enabled, additional fields are managed inside of the mutex structure. pthread_cond_wait() and pthread_timed_wait() do the following atomically: (1) unlock the mutex, (2) wait for the condition, and (3) restore the mutex lock. When that lock is restored, pthread_cond_[timed]wait() must also restore the exact configuration of the mutex data structure if these "exotic" features are enabled.
158 lines
4.0 KiB
C
158 lines
4.0 KiB
C
/****************************************************************************
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* sched/pthread/pthread_condwait.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 <unistd.h>
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#include <pthread.h>
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#include <sched.h>
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#include <errno.h>
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#include <debug.h>
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#include <nuttx/cancelpt.h>
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#include "pthread/pthread.h"
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: int pthread_cond_wait
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*
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* Description:
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* A thread can wait for a condition variable to be signalled or broadcast.
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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_cond_wait(FAR pthread_cond_t *cond, FAR pthread_mutex_t *mutex)
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{
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int status;
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int ret;
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sinfo("cond=0x%p mutex=0x%p\n", cond, mutex);
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/* pthread_cond_wait() is a cancellation point */
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enter_cancellation_point();
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/* Make sure that non-NULL references were provided. */
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if (cond == NULL || mutex == NULL)
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{
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ret = EINVAL;
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}
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/* Make sure that the caller holds the mutex */
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else if (mutex->pid != (int)getpid())
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{
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ret = EPERM;
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}
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else
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{
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#ifndef CONFIG_PTHREAD_MUTEX_UNSAFE
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uint8_t mflags;
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#endif
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#ifdef CONFIG_PTHREAD_MUTEX_TYPES
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uint8_t type;
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int16_t nlocks;
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#endif
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/* Give up the mutex */
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sinfo("Give up mutex / take cond\n");
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sched_lock();
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mutex->pid = -1;
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#ifndef CONFIG_PTHREAD_MUTEX_UNSAFE
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mflags = mutex->flags;
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#endif
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#ifdef CONFIG_PTHREAD_MUTEX_TYPES
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type = mutex->type;
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nlocks = mutex->nlocks;
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#endif
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ret = pthread_mutex_give(mutex);
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/* Take the semaphore. This may be awakened only be a signal (EINTR)
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* or if the thread is canceled (ECANCELED)
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*/
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status = pthread_sem_take((FAR sem_t *)&cond->sem, NULL, false);
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if (ret == OK)
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{
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/* Report the first failure that occurs */
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ret = status;
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}
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sched_unlock();
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/* Reacquire the mutex.
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*
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* When cancellation points are enabled, we need to hold the mutex
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* when the pthread is canceled and cleanup handlers, if any, are
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* entered.
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*/
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sinfo("Reacquire mutex...\n");
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status = pthread_mutex_take(mutex, NULL, false);
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if (ret == OK)
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{
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/* Report the first failure that occurs */
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ret = status;
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}
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/* Did we get the mutex? */
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if (status == OK)
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{
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/* Yes.. Then initialize it properly */
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mutex->pid = getpid();
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#ifndef CONFIG_PTHREAD_MUTEX_UNSAFE
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mutex->flags = mflags;
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#endif
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#ifdef CONFIG_PTHREAD_MUTEX_TYPES
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mutex->type = type;
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mutex->nlocks = nlocks;
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#endif
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}
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}
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leave_cancellation_point();
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sinfo("Returning %d\n", ret);
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return ret;
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}
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