/************************************************************
* pthread_join.c
*
* Copyright (C) 2007 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <spudmonkey@racsa.co.cr>
*
* 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 Gregory Nutt 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 <sys/types.h>
#include <unistd.h>
#include <pthread.h>
#include <errno.h>
#include <debug.h>
#include "os_internal.h"
#include "pthread_internal.h"
/************************************************************
* Definitions
************************************************************/
/************************************************************
* Private Type Declarations
************************************************************/
/************************************************************
* Global Variables
************************************************************/
/************************************************************
* Private Variables
************************************************************/
/************************************************************
* Private Functions
************************************************************/
/************************************************************
* Public Functions
************************************************************/
/************************************************************
* Function: pthread_join
*
* Description:
* A thread can await termination of another thread and
* retrieve the return value of the thread.
*
* Parameters:
* thread
* pexit_value
*
* Return Value:
* 0 if successful. Otherwise, one of the following error codes:
* EINVAL The value specified by thread does not refer to a
* joinable thread.
* ESRCH No thread could be found corresponding to that
* specified by the given thread ID.
* EDEADLK A deadlock was detected or the value of thread
* specifies the calling thread.
*
* Assumptions:
*
************************************************************/
int pthread_join(pthread_t thread, pthread_addr_t *pexit_value)
{
join_t *pjoin;
int ret;
dbg("thread=%d\n", thread);
/* First make sure that this is not an attempt to join to
* ourself.
*/
if ((pid_t)thread == getpid())
{
return EDEADLK;
}
/* Make sure no other task is mucking with the data structures
* while we are performing the following operations. NOTE:
* we can be also sure that pthread_exit() will not execute
* because it will also attempt to get this semaphore.
*/
(void)pthread_takesemaphore(&g_join_semaphore);
/* Find the join information associated with this thread.
* This can fail for one of three reasons: (1) There is no
* thread associated with 'thread,' (2) the thread is a task
* and does not have join information, or (3) the thread
* was detached and has exitted.
*/
pjoin = pthread_findjoininfo((pid_t)thread);
if (!pjoin)
{
/* Determine what kind of error to return */
_TCB *tcb = sched_gettcb((pthread_t)thread);
dbg("Could not find thread data\n");
/* Case (1) or (3) -- we can't tell which. Assume (3) */
if (!tcb)
{
ret = ESRCH;
}
/* The thread is still active but has no join info. In that
* case, it must be a task and not a pthread.
*/
else /* if ((tcb->flags & EDEADLK) == 0) */
{
ret = EINVAL;
}
(void)pthread_givesemaphore(&g_join_semaphore);
}
else if (pjoin->terminated)
{
dbg("Thread has terminated\n");
/* Get the thread exit value from the terminated thread. */
if (pexit_value)
{
dbg("exit_value=0x%p\n", pjoin->exit_value);
*pexit_value = pjoin->exit_value;
}
/* Then remove and deallocate the thread entry. */
(void)pthread_removejoininfo((pid_t)thread);
(void)pthread_givesemaphore(&g_join_semaphore);
sched_free(pjoin);
ret = OK;
}
else
{
dbg("Thread is still running\n");
/* Relinquish the data set semaphore, making certain that
* no task has the opportunity to run between the time
* we relinquish the data set semaphore and the time that
* we wait on the join semaphore.
*/
sched_lock();
(void)pthread_givesemaphore(&g_join_semaphore);
/* Take the thread's join semaphore */
(void)pthread_takesemaphore(&pjoin->exit_sem);
/* Get the thread exit value */
if (pexit_value)
{
*pexit_value = pjoin->exit_value;
dbg("exit_value=0x%p\n", pjoin->exit_value);
}
/* Post the thread's join semaphore so that exitting thread
* will know that we have received the data.
*/
(void)pthread_givesemaphore(&pjoin->data_sem);
/* Pre-emption is okay now. */
sched_unlock();
ret = OK;
}
dbg("Returning %d\n", ret);
return ret;
}
