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/*
* pthread_join.c
*
* Description:
* This translation unit implements functions related to thread
* synchronisation.
*
* --------------------------------------------------------------------------
*
* Pthreads-win32 - POSIX Threads Library for Win32
* Copyright(C) 1998 John E. Bossom
* Copyright(C) 1999,2005 Pthreads-win32 contributors
*
* Contact Email: rpj@callisto.canberra.edu.au
*
* The current list of contributors is contained
* in the file CONTRIBUTORS included with the source
* code distribution. The list can also be seen at the
* following World Wide Web location:
* http://sources.redhat.com/pthreads-win32/contributors.html
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library in the file COPYING.LIB;
* if not, write to the Free Software Foundation, Inc.,
* 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
*/
#include "pthread.h"
#include "implement.h"
/*
* Not needed yet, but defining it should indicate clashes with build target
* environment that should be fixed.
*/
#include <signal.h>
int
pthread_join (pthread_t thread, void **value_ptr)
/*
* ------------------------------------------------------
* DOCPUBLIC
* This function waits for 'thread' to terminate and
* returns the thread's exit value if 'value_ptr' is not
* NULL. This also detaches the thread on successful
* completion.
*
* PARAMETERS
* thread
* an instance of pthread_t
*
* value_ptr
* pointer to an instance of pointer to void
*
*
* DESCRIPTION
* This function waits for 'thread' to terminate and
* returns the thread's exit value if 'value_ptr' is not
* NULL. This also detaches the thread on successful
* completion.
* NOTE: detached threads cannot be joined or canceled
*
* RESULTS
* 0 'thread' has completed
* EINVAL thread is not a joinable thread,
* ESRCH no thread could be found with ID 'thread',
* ENOENT thread couldn't find it's own valid handle,
* EDEADLK attempt to join thread with self
*
* ------------------------------------------------------
*/
{
int result;
pthread_t self;
ptw32_thread_t * tp = (ptw32_thread_t *) thread.p;
/*
* Possibilities for the target thread on entry to pthread_join():
*
* 1) the target thread is detached, in which case it could be destroyed and
* it's thread id (struct) reused before we get the reuse lock;
* 2) the target thread is joinable, in which case it will not be destroyed
* until it has been joined, and it's thread id cannot be reused before we
* get access to it.
*
* Only (1) is a potential race condition.
* While (1) is possibly an application programming error, pthread_join is
* required to handle it with an error.
* If an application attempts to join a detached thread that exits before we
* get the reuse lock, it's thread struct could be reused for a new joinable
* thread before we get the reuse_lock and we will then be joining the wrong
* thread.
*
* To fix this properly would require a reuse count as part of the thread id
* so that we could confirm that we are working with the same thread. This
* option will require a major change to the API, forcing recompilation of
* applications that use the library.
*
* Cheaper alternatives that do not change the API are:
* - separate reuse stacks could be used for detached and joinable
* threads. Threads which detach themselves will not present a race condition
* because they will be placed on a different stack to that which provides
* reusable structs to new joinable threads.
* The problem with this solution is that, an application that creates
* joinable threads which then detach themselves can cause the detach reuse
* stack to grow indefinitely.
*
* - maintain a sufficiently large reuse pool and manage it as a FIFO
* queue. This would prevent the immediate reuse of thread structs, but this
* only provides a statistical safeguard, not a deterministic one.
*
* - include an entry point array at the start of each thread struct so that
* each reuse (modulo N) returns a different thread id (pointer to the thread
* struct). Offset 0 from this pointer will contain a validity field and an
* offset value field (subtracted from the pointer to obtain the address of
* thread struct). This option is similar to including a reuse counter with
* the thread id but maintains the thread id as a simple pointer.
*
* As at 03/11/2004, the reuse count option has been implemented.
*/
EnterCriticalSection (&ptw32_thread_reuse_lock);
/*
* The first test is the same as pthread_kill(thread, 0), duplicated here
* so that we can use the reuse_lock to ensure the thread isn't destroyed
* and reused before we've finished with the POSIX thread struct.
*/
if (tp == NULL
|| NULL == tp->threadH
|| THREAD_PRIORITY_ERROR_RETURN == GetThreadPriority (tp->threadH))
{
result = ESRCH;
}
else if (PTHREAD_CREATE_DETACHED == tp->detachState)
{
result = EINVAL;
}
else
{
/*
* The target thread is joinable and can't be reused before we join it.
*/
LeaveCriticalSection (&ptw32_thread_reuse_lock);
self = pthread_self();
if (NULL == self.p)
{
result = ENOENT;
}
else if (0 != pthread_equal (self, thread))
{
result = EDEADLK;
}
else
{
/*
* Pthread_join is a cancelation point.
* If we are canceled then our target thread must not be
* detached (destroyed). This is guarranteed because
* pthreadCancelableWait will not return if we
* are canceled.
*/
result = pthreadCancelableWait (tp->threadH);
if (0 == result)
{
#if ! defined (__MINGW32__) || defined (__MSVCRT__) || defined (__DMC__)
if (value_ptr != NULL
&& !GetExitCodeThread (tp->threadH, (LPDWORD) value_ptr))
{
result = ESRCH;
}
else
{
/*
* The result of making multiple simultaneous calls to
* pthread_join() specifying the same target is undefined.
*/
ptw32_threadDestroy (thread);
}
#else /* __MINGW32__ && ! __MSVCRT__ */
/*
* If using CRTDLL, the thread may have exited, and endthread
* will have closed the handle.
*/
if (value_ptr != NULL)
{
*value_ptr = tp->exitStatus;
}
/*
* The result of making multiple simultaneous calls to
* pthread_join() specifying the same target is undefined.
*/
ptw32_threadDestroy (thread);
#endif /* __MINGW32__ && ! __MSVCRT__ */
}
else
{
result = ESRCH;
}
}
goto FAIL0;
}
LeaveCriticalSection (&ptw32_thread_reuse_lock);
FAIL0:
return (result);
} /* pthread_join */
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