2016-08-07 16:25:30 +02:00
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/****************************************************************************
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2018-05-29 21:21:26 +02:00
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* libs/libc/pthread/pthread_barrierwait.c
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2007-03-24 00:22:22 +01:00
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*
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2021-03-02 15:54:21 +01:00
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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2007-03-24 00:22:22 +01:00
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*
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2021-03-02 15:54:21 +01:00
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* http://www.apache.org/licenses/LICENSE-2.0
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2007-03-24 00:22:22 +01:00
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*
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2021-03-02 15:54:21 +01:00
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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2007-03-24 00:22:22 +01:00
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*
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2016-08-07 16:25:30 +02:00
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****************************************************************************/
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2007-03-24 00:22:22 +01:00
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2016-08-07 16:25:30 +02:00
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/****************************************************************************
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2007-03-24 00:22:22 +01:00
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* Included Files
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2016-08-07 16:25:30 +02:00
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****************************************************************************/
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2007-03-24 00:22:22 +01:00
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2009-12-14 19:39:29 +01:00
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#include <nuttx/config.h>
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2023-04-11 01:45:05 +02:00
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#include <nuttx/irq.h>
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2007-03-24 00:22:22 +01:00
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#include <pthread.h>
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#include <semaphore.h>
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#include <errno.h>
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#include <debug.h>
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2016-08-07 16:25:30 +02:00
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/****************************************************************************
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2007-03-24 00:22:22 +01:00
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* Public Functions
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2016-08-07 16:25:30 +02:00
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****************************************************************************/
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2007-03-24 00:22:22 +01:00
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2016-08-07 16:25:30 +02:00
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/****************************************************************************
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2012-07-14 21:30:31 +02:00
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* Name: pthread_barrier_wait
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2007-03-24 00:22:22 +01:00
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*
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* Description:
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2016-08-07 16:25:30 +02:00
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* The pthread_barrier_wait() function synchronizse participating threads
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* at the barrier referenced by 'barrier'. The calling thread is blocked
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* until the required number of threads have called pthread_barrier_wait()
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* specifying the same 'barrier'. When the required number of threads
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* have called pthread_barrier_wait() specifying the 'barrier', the
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* constant PTHREAD_BARRIER_SERIAL_THREAD will be returned to one
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* unspecified thread and zero will be returned to each of the remaining
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* threads. At this point, the barrier will be reset to the state it had
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* as a result of the most recent pthread_barrier_init() function that
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* referenced it.
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2007-03-24 00:22:22 +01:00
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*
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* The constant PTHREAD_BARRIER_SERIAL_THREAD is defined in pthread.h and
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* its value must be distinct from any other value returned by
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* pthread_barrier_wait().
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2007-03-24 00:22:22 +01:00
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*
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* The results are undefined if this function is called with an
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* uninitialized barrier.
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2007-03-24 00:22:22 +01:00
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*
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* If a signal is delivered to a thread blocked on a barrier, upon return
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* from the signal handler the thread will resume waiting at the barrier
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* if the barrier wait has not completed; otherwise, the thread will
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* continue as normal from the completed barrier wait. Until the thread in
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* the signal handler returns from it, it is unspecified whether other
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* threads may proceed past the barrier once they have all reached it.
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2007-03-24 00:22:22 +01:00
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*
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* A thread that has blocked on a barrier will not prevent any unblocked
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* thread that is eligible to use the same processing resources from
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* eventually making forward progress in its execution. Eligibility for
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* processing resources will be determined by the scheduling policy.
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2007-03-24 00:22:22 +01:00
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*
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2018-03-13 16:52:27 +01:00
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* Input Parameters:
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* barrier - the barrier to wait on
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*
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2018-02-01 17:00:02 +01:00
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* Returned Value:
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* 0 (OK) on success or EINVAL if the barrier is not valid.
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*
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* Assumptions:
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*
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2016-08-07 16:25:30 +02:00
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****************************************************************************/
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2007-03-24 00:22:22 +01:00
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int pthread_barrier_wait(FAR pthread_barrier_t *barrier)
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{
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int semcount;
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int ret = OK;
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2023-04-11 01:45:05 +02:00
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irqstate_t flags;
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2007-03-24 00:22:22 +01:00
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if (!barrier)
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{
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return EINVAL;
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}
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/* Disable pre-emption throughout the following */
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2023-04-11 01:45:05 +02:00
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flags = enter_critical_section();
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2007-03-24 00:22:22 +01:00
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/* Find out how many threads are already waiting at the barrier */
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2017-10-03 23:35:24 +02:00
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ret = sem_getvalue(&barrier->sem, &semcount);
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2007-03-24 00:22:22 +01:00
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if (ret != OK)
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{
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2023-04-11 01:45:05 +02:00
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leave_critical_section(flags);
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2021-01-28 10:03:22 +01:00
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return get_errno();
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2007-03-24 00:22:22 +01:00
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}
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/* If the number of waiters would be equal to the count, then we are done */
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2014-01-14 20:30:22 +01:00
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if ((1 - semcount) >= (int)barrier->count)
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2007-03-24 00:22:22 +01:00
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{
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/* Free all of the waiting threads */
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while (semcount < 0)
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{
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2020-01-02 17:49:34 +01:00
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sem_post(&barrier->sem);
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sem_getvalue(&barrier->sem, &semcount);
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2007-03-24 00:22:22 +01:00
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}
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/* Then return PTHREAD_BARRIER_SERIAL_THREAD to the final thread */
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2023-04-11 01:45:05 +02:00
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leave_critical_section(flags);
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2007-03-24 00:22:22 +01:00
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return PTHREAD_BARRIER_SERIAL_THREAD;
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}
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else
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{
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/* Otherwise, this thread must wait as well */
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while (sem_wait(&barrier->sem) != OK)
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{
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/* If the thread is awakened by a signal, just continue to wait */
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2012-07-14 21:30:31 +02:00
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int errornumber = get_errno();
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2007-03-24 00:22:22 +01:00
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if (errornumber != EINTR)
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{
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/* If it is awakened by some other error, then there is a
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* problem
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*/
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2023-04-11 01:45:05 +02:00
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leave_critical_section(flags);
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2007-03-24 00:22:22 +01:00
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return errornumber;
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}
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}
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/* We will only get here when we are one of the N-1 threads that were
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* waiting for the final thread at the barrier. We just need to return
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* zero.
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*/
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2023-04-11 01:45:05 +02:00
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leave_critical_section(flags);
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2007-03-24 00:22:22 +01:00
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return 0;
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}
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}
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