nuttx/sched/pthread/pthread_completejoin.c
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C

/****************************************************************************
* sched/pthread/pthread_completejoin.c
*
* Copyright (C) 2007, 2009, 2011, 2013 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <gnutt@nuttx.org>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* 3. Neither the name NuttX nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <sys/types.h>
#include <stdbool.h>
#include <pthread.h>
#include <errno.h>
#include <debug.h>
#include "sched/sched.h"
#include "group/group.h"
#include "pthread/pthread.h"
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Name: pthread_notifywaiters
*
* Description:
* Notify all other threads waiting in phread join for this thread's
* exit data. This must be done by the child at child thread
* destruction time.
*
****************************************************************************/
static bool pthread_notifywaiters(FAR struct join_s *pjoin)
{
int ntasks_waiting;
int status;
sinfo("pjoin=0x%p\n", pjoin);
/* Are any tasks waiting for our exit value? */
status = nxsem_getvalue(&pjoin->exit_sem, &ntasks_waiting);
if (status == OK && ntasks_waiting < 0)
{
/* Set the data semaphore so that this thread will be
* awakened when all waiting tasks receive the data
*/
nxsem_init(&pjoin->data_sem, 0, (ntasks_waiting + 1));
/* Post the semaphore to restart each thread that is waiting
* on the semaphore
*/
do
{
status = pthread_sem_give(&pjoin->exit_sem);
if (status == OK)
{
status = nxsem_getvalue(&pjoin->exit_sem, &ntasks_waiting);
}
}
while (ntasks_waiting < 0 && status == OK);
/* Now wait for all these restarted tasks to obtain the return
* value.
*/
pthread_sem_take(&pjoin->data_sem, NULL, false);
return true;
}
return false;
}
/****************************************************************************
* Name: pthread_removejoininfo
*
* Description:
* Remove a join structure from the local data set.
*
* Input Parameters:
* pid
*
* Returned Value:
* None.
*
* Assumptions:
* The caller has provided protection from re-entrancy.
*
****************************************************************************/
static void pthread_removejoininfo(FAR struct task_group_s *group,
pid_t pid)
{
FAR struct join_s *prev;
FAR struct join_s *join;
/* Find the entry with the matching pid */
for (prev = NULL, join = group->tg_joinhead;
(join && (pid_t)join->thread != pid);
prev = join, join = join->next);
/* Remove it from the data set. */
/* First check if this is the entry at the head of the list. */
if (join)
{
if (!prev)
{
/* Check if this is the only entry in the list */
if (!join->next)
{
group->tg_joinhead = NULL;
group->tg_jointail = NULL;
}
/* Otherwise, remove it from the head of the list */
else
{
group->tg_joinhead = join->next;
}
}
/* It is not at the head of the list, check if it is at the tail. */
else if (!join->next)
{
group->tg_jointail = prev;
prev->next = NULL;
}
/* No, remove it from the middle of the list. */
else
{
prev->next = join->next;
}
}
}
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: pthread_completejoin
*
* Description:
* A thread has been terminated -- either by returning, calling
* pthread_exit(), or through pthread_cancel(). In any event, we must
* complete any pending join events.
*
* Input Parameters:
* exit_value
*
* Returned Value:
* OK unless there is no join information associated with the pid.
* This could happen, for example, if a task started with task_create()
* calls pthread_exit().
*
* Assumptions:
*
****************************************************************************/
int pthread_completejoin(pid_t pid, FAR void *exit_value)
{
FAR struct task_group_s *group = task_getgroup(pid);
FAR struct join_s *pjoin;
sinfo("pid=%d exit_value=%p group=%p\n", pid, exit_value, group);
DEBUGASSERT(group);
/* First, find thread's structure in the private data set. */
pthread_sem_take(&group->tg_joinsem, NULL, false);
pjoin = pthread_findjoininfo(group, pid);
if (!pjoin)
{
serr("ERROR: Could not find join info, pid=%d\n", pid);
pthread_sem_give(&group->tg_joinsem);
return ERROR;
}
else
{
bool waiters;
/* Save the return exit value in the thread structure. */
pjoin->terminated = true;
pjoin->exit_value = exit_value;
/* Notify waiters of the availability of the exit value */
waiters = pthread_notifywaiters(pjoin);
/* If there are no waiters and if the thread is marked as detached.
* then discard the join information now. Otherwise, the pthread
* join logic will call pthread_destroyjoin() when all of the threads
* have sampled the exit value.
*/
if (!waiters && pjoin->detached)
{
pthread_destroyjoin(group, pjoin);
}
/* Giving the following semaphore will allow the waiters
* to call pthread_destroyjoin.
*/
pthread_sem_give(&group->tg_joinsem);
}
return OK;
}
/****************************************************************************
* Name: pthread_destroyjoin
*
* Description:
* This is called from pthread_completejoin if the join info was
* detached or from pthread_join when the last waiting thread has
* received the thread exit info.
*
* Or it may never be called if the join info was never detached or if
* no thread ever calls pthread_join. In case, there is a memory leak!
*
* Assumptions:
* The caller holds tg_joinsem
*
****************************************************************************/
void pthread_destroyjoin(FAR struct task_group_s *group,
FAR struct join_s *pjoin)
{
sinfo("pjoin=0x%p\n", pjoin);
/* Remove the join info from the set of joins */
pthread_removejoininfo(group, (pid_t)pjoin->thread);
/* Destroy its semaphores */
nxsem_destroy(&pjoin->data_sem);
nxsem_destroy(&pjoin->exit_sem);
/* And deallocate the pjoin structure */
sched_kfree(pjoin);
}