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/*
* pthread_once.c
*
* Description:
* This translation unit implements miscellaneous thread functions.
*
* --------------------------------------------------------------------------
*
* 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"
static void PTW32_CDECL
ptw32_once_init_routine_cleanup(void * arg)
{
pthread_once_t * once_control = (pthread_once_t *) arg;
(void) PTW32_INTERLOCKED_EXCHANGE((LPLONG)&once_control->state, (LONG)PTW32_ONCE_INIT);
if (InterlockedExchangeAdd((LPLONG)&once_control->semaphore, 0L)) /* MBR fence */
{
ReleaseSemaphore(once_control->semaphore, 1, NULL);
}
}
int
pthread_once (pthread_once_t * once_control, void (*init_routine) (void))
/*
* ------------------------------------------------------
* DOCPUBLIC
* If any thread in a process with a once_control parameter
* makes a call to pthread_once(), the first call will summon
* the init_routine(), but subsequent calls will not. The
* once_control parameter determines whether the associated
* initialization routine has been called. The init_routine()
* is complete upon return of pthread_once().
* This function guarantees that one and only one thread
* executes the initialization routine, init_routine when
* access is controlled by the pthread_once_t control
* key.
*
* pthread_once() is not a cancelation point, but the init_routine
* can be. If it's cancelled then the effect on the once_control is
* as if pthread_once had never been entered.
*
*
* PARAMETERS
* once_control
* pointer to an instance of pthread_once_t
*
* init_routine
* pointer to an initialization routine
*
*
* DESCRIPTION
* See above.
*
* RESULTS
* 0 success,
* EINVAL once_control or init_routine is NULL
*
* ------------------------------------------------------
*/
{
int result;
int state;
HANDLE sema;
if (once_control == NULL || init_routine == NULL)
{
result = EINVAL;
goto FAIL0;
}
else
{
result = 0;
}
while ((state =
PTW32_INTERLOCKED_COMPARE_EXCHANGE((PTW32_INTERLOCKED_LPLONG)&once_control->state,
(PTW32_INTERLOCKED_LONG)PTW32_ONCE_STARTED,
(PTW32_INTERLOCKED_LONG)PTW32_ONCE_INIT))
!= PTW32_ONCE_DONE)
{
if (PTW32_ONCE_INIT == state)
{
#ifdef _MSC_VER
#pragma inline_depth(0)
#endif
pthread_cleanup_push(ptw32_once_init_routine_cleanup, (void *) once_control);
(*init_routine)();
pthread_cleanup_pop(0);
#ifdef _MSC_VER
#pragma inline_depth()
#endif
(void) PTW32_INTERLOCKED_EXCHANGE((LPLONG)&once_control->state,
(LONG)PTW32_ONCE_DONE);
/*
* we didn't create the semaphore.
* it is only there if there is someone waiting.
*/
if (InterlockedExchangeAdd((LPLONG)&once_control->semaphore, 0L)) /* MBR fence */
{
ReleaseSemaphore(once_control->semaphore,
once_control->numSemaphoreUsers, NULL);
}
}
else
{
InterlockedIncrement((LPLONG)&once_control->numSemaphoreUsers);
if (!InterlockedExchangeAdd((LPLONG)&once_control->semaphore, 0L)) /* MBR fence */
{
sema = CreateSemaphore(NULL, 0, INT_MAX, NULL);
if (PTW32_INTERLOCKED_COMPARE_EXCHANGE((PTW32_INTERLOCKED_LPLONG)&once_control->semaphore,
(PTW32_INTERLOCKED_LONG)sema,
(PTW32_INTERLOCKED_LONG)0))
{
CloseHandle(sema);
}
}
/*
* Check 'state' again in case the initting thread has finished or
* cancelled and left before seeing that there was a semaphore.
*/
if (InterlockedExchangeAdd((LPLONG)&once_control->state, 0L) == PTW32_ONCE_STARTED)
{
WaitForSingleObject(once_control->semaphore, INFINITE);
}
if (0 == InterlockedDecrement((LPLONG)&once_control->numSemaphoreUsers))
{
/* we were last */
if ((sema =
(HANDLE) PTW32_INTERLOCKED_EXCHANGE((LPLONG)&once_control->semaphore, (LONG)0)))
{
CloseHandle(sema);
}
}
}
}
/*
* ------------
* Failure Code
* ------------
*/
FAIL0:
return (result);
} /* pthread_once */
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