d2410c93c6
git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@181 42af7a65-404d-4744-a932-0658087f49c3
248 lines
7.7 KiB
C
248 lines
7.7 KiB
C
/************************************************************
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* pthread_join.c
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*
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* Copyright (C) 2007 Gregory Nutt. All rights reserved.
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* Author: Gregory Nutt <spudmonkey@racsa.co.cr>
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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* 3. Neither the name Gregory Nutt nor the names of its contributors may be
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* used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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* POSSIBILITY OF SUCH DAMAGE.
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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 <sys/types.h>
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#include <unistd.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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#include "os_internal.h"
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#include "pthread_internal.h"
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/************************************************************
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* Definitions
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************************************************************/
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/************************************************************
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* Private Type Declarations
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************************************************************/
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/************************************************************
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* Global Variables
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************************************************************/
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/************************************************************
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* Private Variables
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************************************************************/
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/************************************************************
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* Private Functions
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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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* Function: pthread_join
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*
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* Description:
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* A thread can await termination of another thread and
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* retrieve the return value of the thread.
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*
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* Parameters:
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* thread
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* pexit_value
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*
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* Return Value:
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* 0 if successful. Otherwise, one of the following error codes:
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*
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* EINVAL The value specified by thread does not refer to a
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* joinable thread.
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* ESRCH No thread could be found corresponding to that
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* specified by the given thread ID.
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* EDEADLK A deadlock was detected or the value of thread
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* specifies the calling thread.
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*
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* Assumptions:
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*
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************************************************************/
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int pthread_join(pthread_t thread, pthread_addr_t *pexit_value)
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{
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FAR join_t *pjoin;
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int ret;
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dbg("thread=%d\n", thread);
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/* First make sure that this is not an attempt to join to
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* ourself.
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*/
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if ((pid_t)thread == getpid())
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{
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return EDEADLK;
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}
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/* Make sure no other task is mucking with the data structures
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* while we are performing the following operations. NOTE:
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* we can be also sure that pthread_exit() will not execute
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* because it will also attempt to get this semaphore.
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*/
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(void)pthread_takesemaphore(&g_join_semaphore);
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/* Find the join information associated with this thread.
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* This can fail for one of three reasons: (1) There is no
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* thread associated with 'thread,' (2) the thread is a task
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* and does not have join information, or (3) the thread
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* was detached and has exitted.
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*/
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pjoin = pthread_findjoininfo((pid_t)thread);
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if (!pjoin)
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{
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/* Determine what kind of error to return */
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FAR _TCB *tcb = sched_gettcb((pthread_t)thread);
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dbg("Could not find thread data\n");
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/* Case (1) or (3) -- we can't tell which. Assume (3) */
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if (!tcb)
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{
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ret = ESRCH;
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}
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/* The thread is still active but has no join info. In that
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* case, it must be a task and not a pthread.
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*/
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else
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{
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ret = EINVAL;
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}
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(void)pthread_givesemaphore(&g_join_semaphore);
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}
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else
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{
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/* We found the join info structure. Increment for the reference
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* to the join structure that we have. This will keep things
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* stable for we have to do
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*/
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sched_lock();
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pjoin->crefs++;
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/* Check if the thread is still running. If not, then things are
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* simpler. There are still race conditions to be concerned with.
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* For example, there could be multiple threads executing in the
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* 'else' block below when we enter!
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*/
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if (pjoin->terminated)
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{
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dbg("Thread has terminated\n");
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/* Get the thread exit value from the terminated thread. */
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if (pexit_value)
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{
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dbg("exit_value=0x%p\n", pjoin->exit_value);
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*pexit_value = pjoin->exit_value;
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}
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}
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else
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{
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dbg("Thread is still running\n");
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/* Relinquish the data set semaphore. Since pre-emption is
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* disabled, we can be certain that no task has the
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* opportunity to run between the time we relinquish the
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* join semaphore and the time that we wait on the thread exit
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* semaphore.
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*/
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(void)pthread_givesemaphore(&g_join_semaphore);
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/* Take the thread's thread exit semaphore. We will sleep here
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* until the thread exits. We need to exercise caution because
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* there could be multiple threads waiting here for the same
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* pthread to exit.
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*/
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(void)pthread_takesemaphore(&pjoin->exit_sem);
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/* The thread has exited! Get the thread exit value */
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if (pexit_value)
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{
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*pexit_value = pjoin->exit_value;
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dbg("exit_value=0x%p\n", pjoin->exit_value);
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}
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/* Post the thread's data semaphore so that the exitting thread
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* will know that we have received the data.
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*/
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(void)pthread_givesemaphore(&pjoin->data_sem);
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/* Retake the join semaphore, we need to hold this when
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* pthread_destroyjoin is called.
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*/
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(void)pthread_takesemaphore(&g_join_semaphore);
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}
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/* Pre-emption is okay now. The logic still cannot be re-entered
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* because we hold the join semaphore
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*/
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sched_unlock();
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/* Release our reference to the join structure and, if the reference
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* count decrements to zero, deallocate the join structure.
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*/
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if (--pjoin->crefs <= 0)
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{
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(void)pthread_destroyjoin(pjoin);
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}
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(void)pthread_givesemaphore(&g_join_semaphore);
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ret = OK;
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}
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dbg("Returning %d\n", ret);
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return ret;
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}
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