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- /*
- * pthread_once.c
- *
- * Description:
- * This translation unit implements miscellaneous thread functions.
- *
- * --------------------------------------------------------------------------
- *
- * Pthreads-embedded (PTE) - POSIX Threads Library for embedded systems
- * Copyright(C) 2008 Jason Schmidlapp
- *
- * Contact Email: [email protected]
- *
- *
- * Based upon Pthreads-win32 - POSIX Threads Library for Win32
- * Copyright(C) 1998 John E. Bossom
- * Copyright(C) 1999,2005 Pthreads-win32 contributors
- *
- * Contact Email: [email protected]
- *
- * The original list of contributors to the Pthreads-win32 project
- * is contained in the file CONTRIBUTORS.ptw32 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 "pte_osal.h"
- #include "pthread.h"
- #include "implement.h"
- #define PTE_ONCE_STARTED 1
- #define PTE_ONCE_INIT 0
- #define PTE_ONCE_DONE 2
- static void
- pte_once_init_routine_cleanup(void * arg)
- {
- pthread_once_t * once_control = (pthread_once_t *) arg;
- (void) PTE_ATOMIC_EXCHANGE(&once_control->state,PTE_ONCE_INIT);
- if (PTE_ATOMIC_EXCHANGE_ADD((int*)&once_control->semaphore, 0L)) /* MBR fence */
- {
- pte_osSemaphorePost((pte_osSemaphoreHandle) once_control->semaphore, 1);
- }
- }
- 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;
- pte_osSemaphoreHandle sema;
- if (once_control == NULL || init_routine == NULL)
- {
- result = EINVAL;
- goto FAIL0;
- }
- else
- {
- result = 0;
- }
- while ((state =
- PTE_ATOMIC_COMPARE_EXCHANGE(&once_control->state,
- PTE_ONCE_STARTED,
- PTE_ONCE_INIT))
- != PTE_ONCE_DONE)
- {
- if (PTE_ONCE_INIT == state)
- {
- pthread_cleanup_push(pte_once_init_routine_cleanup, (void *) once_control);
- (*init_routine)();
- pthread_cleanup_pop(0);
- (void) PTE_ATOMIC_EXCHANGE(&once_control->state,PTE_ONCE_DONE);
- /*
- * we didn't create the semaphore.
- * it is only there if there is someone waiting.
- */
- if (PTE_ATOMIC_EXCHANGE_ADD((int*)&once_control->semaphore, 0L)) /* MBR fence */
- {
- pte_osSemaphorePost((pte_osSemaphoreHandle) once_control->semaphore,once_control->numSemaphoreUsers);
- }
- }
- else
- {
- PTE_ATOMIC_INCREMENT(&once_control->numSemaphoreUsers);
- if (!PTE_ATOMIC_EXCHANGE_ADD((int*)&once_control->semaphore, 0L)) /* MBR fence */
- {
- pte_osSemaphoreCreate(0, (pte_osSemaphoreHandle*) &sema);
- if (PTE_ATOMIC_COMPARE_EXCHANGE((int *) &once_control->semaphore,
- (int) sema,
- 0))
- {
- pte_osSemaphoreDelete((pte_osSemaphoreHandle)sema);
- }
- }
- /*
- * Check 'state' again in case the initting thread has finished or
- * cancelled and left before seeing that there was a semaphore.
- */
- if (PTE_ATOMIC_EXCHANGE_ADD(&once_control->state, 0L) == PTE_ONCE_STARTED)
- {
- pte_osSemaphorePend((pte_osSemaphoreHandle) once_control->semaphore,NULL);
- }
- if (0 == PTE_ATOMIC_DECREMENT(&once_control->numSemaphoreUsers))
- {
- /* we were last */
- if ((sema =
- (pte_osSemaphoreHandle) PTE_ATOMIC_EXCHANGE((int *) &once_control->semaphore,0)))
- {
- pte_osSemaphoreDelete(sema);
- }
- }
- }
- }
- /*
- * ------------
- * Failure Code
- * ------------
- */
- FAIL0:
- return (result);
- } /* pthread_once */
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