275 lines
7.6 KiB
C
275 lines
7.6 KiB
C
/****************************************************************************
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* sched/pthread/pthread_completejoin.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 <sys/types.h>
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#include <stdbool.h>
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#include <pthread.h>
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#include <assert.h>
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#include <errno.h>
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#include <debug.h>
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#include "sched/sched.h"
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#include "group/group.h"
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#include "pthread/pthread.h"
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/****************************************************************************
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* Private Functions
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****************************************************************************/
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/****************************************************************************
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* Name: pthread_notifywaiters
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*
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* Description:
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* Notify all other threads waiting in phread join for this thread's
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* exit data. This must be done by the child at child thread
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* destruction time.
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*
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****************************************************************************/
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static bool pthread_notifywaiters(FAR struct join_s *pjoin)
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{
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int ntasks_waiting;
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int status;
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sinfo("pjoin=0x%p\n", pjoin);
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/* Are any tasks waiting for our exit value? */
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status = nxsem_get_value(&pjoin->exit_sem, &ntasks_waiting);
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if (status == OK && ntasks_waiting < 0)
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{
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/* Set the data semaphore so that this thread will be
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* awakened when all waiting tasks receive the data
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*/
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nxsem_init(&pjoin->data_sem, 0, (ntasks_waiting + 1));
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/* Post the semaphore to restart each thread that is waiting
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* on the semaphore
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*/
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do
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{
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status = pthread_sem_give(&pjoin->exit_sem);
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if (status == OK)
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{
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status = nxsem_get_value(&pjoin->exit_sem, &ntasks_waiting);
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}
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}
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while (ntasks_waiting < 0 && status == OK);
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/* Now wait for all these restarted tasks to obtain the return
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* value.
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*/
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pthread_sem_take(&pjoin->data_sem, NULL, false);
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return true;
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}
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return false;
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}
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/****************************************************************************
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* Name: pthread_removejoininfo
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*
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* Description:
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* Remove a join structure from the local data set.
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*
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* Input Parameters:
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* pid
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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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* The caller has provided protection from re-entrancy.
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*
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****************************************************************************/
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static void pthread_removejoininfo(FAR struct task_group_s *group,
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pid_t pid)
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{
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FAR struct join_s *prev;
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FAR struct join_s *join;
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/* Find the entry with the matching pid */
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for (prev = NULL, join = group->tg_joinhead;
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(join && (pid_t)join->thread != pid);
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prev = join, join = join->next);
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/* Remove it from the data set. */
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/* First check if this is the entry at the head of the list. */
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if (join)
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{
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if (!prev)
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{
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/* Check if this is the only entry in the list */
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if (!join->next)
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{
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group->tg_joinhead = NULL;
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group->tg_jointail = NULL;
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}
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/* Otherwise, remove it from the head of the list */
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else
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{
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group->tg_joinhead = join->next;
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}
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}
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/* It is not at the head of the list, check if it is at the tail. */
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else if (!join->next)
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{
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group->tg_jointail = prev;
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prev->next = NULL;
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}
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/* No, remove it from the middle of the list. */
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else
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{
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prev->next = join->next;
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}
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}
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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_completejoin
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*
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* Description:
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* A thread has been terminated -- either by returning, calling
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* pthread_exit(), or through pthread_cancel(). In any event, we must
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* complete any pending join events.
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*
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* Input Parameters:
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* exit_value
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*
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* Returned Value:
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* OK unless there is no join information associated with the pid.
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* This could happen, for example, if a task started with task_create()
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* calls pthread_exit().
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*
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* Assumptions:
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*
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****************************************************************************/
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int pthread_completejoin(pid_t pid, FAR void *exit_value)
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{
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FAR struct task_group_s *group = task_getgroup(pid);
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FAR struct join_s *pjoin;
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sinfo("pid=%d exit_value=%p group=%p\n", pid, exit_value, group);
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DEBUGASSERT(group);
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/* First, find thread's structure in the private data set. */
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pthread_sem_take(&group->tg_joinsem, NULL, false);
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pjoin = pthread_findjoininfo(group, pid);
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if (!pjoin)
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{
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serr("ERROR: Could not find join info, pid=%d\n", pid);
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pthread_sem_give(&group->tg_joinsem);
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return ERROR;
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}
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else
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{
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bool waiters;
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/* Save the return exit value in the thread structure. */
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pjoin->terminated = true;
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pjoin->exit_value = exit_value;
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/* Notify waiters of the availability of the exit value */
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waiters = pthread_notifywaiters(pjoin);
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/* If there are no waiters and if the thread is marked as detached.
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* then discard the join information now. Otherwise, the pthread
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* join logic will call pthread_destroyjoin() when all of the threads
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* have sampled the exit value.
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*/
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if (!waiters && pjoin->detached)
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{
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pthread_destroyjoin(group, pjoin);
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}
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/* Giving the following semaphore will allow the waiters
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* to call pthread_destroyjoin.
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*/
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pthread_sem_give(&group->tg_joinsem);
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}
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return OK;
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}
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/****************************************************************************
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* Name: pthread_destroyjoin
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*
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* Description:
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* This is called from pthread_completejoin if the join info was
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* detached or from pthread_join when the last waiting thread has
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* received the thread exit info.
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*
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* Or it may never be called if the join info was never detached or if
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* no thread ever calls pthread_join. In case, there is a memory leak!
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*
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* Assumptions:
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* The caller holds tg_joinsem
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*
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****************************************************************************/
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void pthread_destroyjoin(FAR struct task_group_s *group,
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FAR struct join_s *pjoin)
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{
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sinfo("pjoin=0x%p\n", pjoin);
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/* Remove the join info from the set of joins */
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pthread_removejoininfo(group, (pid_t)pjoin->thread);
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/* Destroy its semaphores */
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nxsem_destroy(&pjoin->data_sem);
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nxsem_destroy(&pjoin->exit_sem);
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/* And deallocate the pjoin structure */
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kmm_free(pjoin);
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}
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