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* This translation unit implements barrier primitives.
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* Pthreads-win32 - POSIX Threads Library for Win32
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Library General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Library General Public License for more details.
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* You should have received a copy of the GNU Library General Public
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* License along with this library; if not, write to the Free
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* Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
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#include "implement.h"
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#define _LPLONG PVOID*
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pthread_barrier_init(pthread_barrier_t * barrier,
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const pthread_barrierattr_t * attr,
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if (barrier == NULL || count == 0)
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if (NULL != (b = (pthread_barrier_t) calloc(1, sizeof(*b))))
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b->pshared = (attr != NULL && *attr != NULL
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: PTHREAD_PROCESS_PRIVATE);
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b->nCurrentBarrierHeight = b->nInitialBarrierHeight = count;
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* Two semaphores are used in the same way as two stepping
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* stones might be used in crossing a stream. Once all
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* threads are safely on one stone, the other stone can
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* be moved ahead, and the threads can start moving to it.
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* If some threads decide to eat their lunch before moving
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* then the other threads have to wait.
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if (0 == sem_init(&(b->semBarrierBreeched[0]), b->pshared, 0))
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if (0 == sem_init(&(b->semBarrierBreeched[1]), b->pshared, 0))
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(void) sem_destroy(&(b->semBarrierBreeched[0]));
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pthread_barrier_destroy(pthread_barrier_t *barrier)
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if (barrier == NULL || *barrier == (pthread_barrier_t) PTW32_OBJECT_INVALID)
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if (0 == (result = sem_destroy(&(b->semBarrierBreeched[0]))))
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if (0 == (result = sem_destroy(&(b->semBarrierBreeched[1]))))
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(void) sem_init(&(b->semBarrierBreeched[0]),
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pthread_barrier_wait(pthread_barrier_t *barrier)
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if (barrier == NULL || *barrier == (pthread_barrier_t) PTW32_OBJECT_INVALID)
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if (0 == InterlockedDecrement((long *) &(b->nCurrentBarrierHeight)))
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/* Must be done before posting the semaphore. */
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b->nCurrentBarrierHeight = b->nInitialBarrierHeight;
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* There is no race condition between the semaphore wait and post
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* because we are using two alternating semas and all threads have
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* entered barrier_wait and checked nCurrentBarrierHeight before this
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* barrier's sema can be posted. Any threads that have not quite
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* entered sem_wait below when the multiple_post has completed
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* will nevertheless continue through the semaphore (barrier)
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* and will not be left stranded.
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result = (b->nInitialBarrierHeight > 1
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? sem_post_multiple(&(b->semBarrierBreeched[step]),
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b->nInitialBarrierHeight - 1)
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BOOL switchCancelState;
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pthread_t self = pthread_self();
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* This routine is not a cancelation point, so temporarily
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* prevent sem_wait() from being one.
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* PTHREAD_CANCEL_ASYNCHRONOUS threads can still be canceled.
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switchCancelState = (self->cancelType == PTHREAD_CANCEL_DEFERRED &&
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0 == pthread_setcancelstate(PTHREAD_CANCEL_DISABLE,
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result = sem_wait(&(b->semBarrierBreeched[step]));
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if (switchCancelState)
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(void) pthread_setcancelstate(oldCancelState, NULL);
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* The first thread across will be the PTHREAD_BARRIER_SERIAL_THREAD.
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* It also sets up the alternate semaphore as the next barrier.
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result = ((_LONG) step ==
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InterlockedCompareExchange((_LPLONG) &(b->iStep),
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? PTHREAD_BARRIER_SERIAL_THREAD
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pthread_barrierattr_init (pthread_barrierattr_t * attr)
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* ------------------------------------------------------
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* Initializes a barrier attributes object with default
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* pointer to an instance of pthread_barrierattr_t
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* Initializes a barrier attributes object with default
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* 1) Used to define barrier types
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* 0 successfully initialized attr,
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* ENOMEM insufficient memory for attr.
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* ------------------------------------------------------
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pthread_barrierattr_t ba;
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ba = (pthread_barrierattr_t) calloc (1, sizeof (*ba));
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ba->pshared = PTHREAD_PROCESS_PRIVATE;
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} /* pthread_barrierattr_init */
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pthread_barrierattr_destroy (pthread_barrierattr_t * attr)
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* ------------------------------------------------------
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* Destroys a barrier attributes object. The object can
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* pointer to an instance of pthread_barrierattr_t
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* Destroys a barrier attributes object. The object can
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* 1) Does not affect barrieres created using 'attr'
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* 0 successfully released attr,
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* EINVAL 'attr' is invalid.
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* ------------------------------------------------------
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if (attr == NULL || *attr == NULL)
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pthread_barrierattr_t ba = *attr;
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} /* pthread_barrierattr_destroy */
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pthread_barrierattr_getpshared (const pthread_barrierattr_t * attr,
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* ------------------------------------------------------
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* Determine whether barriers created with 'attr' can be
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* shared between processes.
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* pointer to an instance of pthread_barrierattr_t
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* will be set to one of:
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* PTHREAD_PROCESS_SHARED
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* May be shared if in shared memory
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* PTHREAD_PROCESS_PRIVATE
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* Mutexes creatd with 'attr' can be shared between
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* processes if pthread_barrier_t variable is allocated
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* in memory shared by these processes.
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* 1) pshared barriers MUST be allocated in shared
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* 2) The following macro is defined if shared barriers
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* _POSIX_THREAD_PROCESS_SHARED
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* 0 successfully retrieved attribute,
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* EINVAL 'attr' is invalid,
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* ------------------------------------------------------
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if ((attr != NULL && *attr != NULL) &&
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*pshared = (*attr)->pshared;
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*pshared = PTHREAD_PROCESS_PRIVATE;
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} /* pthread_barrierattr_getpshared */
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pthread_barrierattr_setpshared (pthread_barrierattr_t * attr,
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* ------------------------------------------------------
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* Barriers created with 'attr' can be shared between
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* processes if pthread_barrier_t variable is allocated
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* in memory shared by these processes.
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* pointer to an instance of pthread_barrierattr_t
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* PTHREAD_PROCESS_SHARED
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* May be shared if in shared memory
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* PTHREAD_PROCESS_PRIVATE
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* Mutexes creatd with 'attr' can be shared between
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* processes if pthread_barrier_t variable is allocated
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* in memory shared by these processes.
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* 1) pshared barriers MUST be allocated in shared
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* 2) The following macro is defined if shared barriers
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* _POSIX_THREAD_PROCESS_SHARED
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* 0 successfully set attribute,
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* EINVAL 'attr' or pshared is invalid,
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* ENOSYS PTHREAD_PROCESS_SHARED not supported,
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* ------------------------------------------------------
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if ((attr != NULL && *attr != NULL) &&
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((pshared == PTHREAD_PROCESS_SHARED) ||
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(pshared == PTHREAD_PROCESS_PRIVATE)))
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if (pshared == PTHREAD_PROCESS_SHARED)
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#if !defined( _POSIX_THREAD_PROCESS_SHARED )
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pshared = PTHREAD_PROCESS_PRIVATE;
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#endif /* _POSIX_THREAD_PROCESS_SHARED */
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(*attr)->pshared = pshared;
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} /* pthread_barrierattr_setpshared */
added
removed
win32/contrib/pthreads/barrier.c
