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/*
* Amazon FreeRTOS POSIX V1.1.0
* Copyright (C) 2018 Amazon.com, Inc. or its affiliates. All Rights Reserved.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy of
* this software and associated documentation files (the "Software"), to deal in
* the Software without restriction, including without limitation the rights to
* use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
* the Software, and to permit persons to whom the Software is furnished to do so,
* subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
* FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
* COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
* IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
* CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*
* http://aws.amazon.com/freertos
* http://www.FreeRTOS.org
*/
/**
* @file FreeRTOS_POSIX_pthread_barrier.c
* @brief Implementation of barrier functions in pthread.h
*/
/* C standard library includes. */
#include <stddef.h>
/* FreeRTOS+POSIX includes. */
#include "FreeRTOS_POSIX.h"
#include "FreeRTOS_POSIX/errno.h"
#include "FreeRTOS_POSIX/pthread.h"
#include "atomic.h"
/*
* @brief barrier max count
*
* Barriers are implemented on FreeRTOS event groups, of which 8 bits are usable
* when configUSE_16_BIT_TICKS is 1. Otherwise, 24 bits are usable.
*/
/**@{ */
#if ( configUSE_16_BIT_TICKS == 1 )
#define posixPTHREAD_BARRIER_MAX_COUNT ( 8 )
#else
#define posixPTHREAD_BARRIER_MAX_COUNT ( 24 )
#endif
/**@} */
/*-----------------------------------------------------------*/
int pthread_barrier_destroy( pthread_barrier_t * barrier )
{
pthread_barrier_internal_t * pxBarrier = ( pthread_barrier_internal_t * ) ( barrier );
/* Free all resources used by the barrier. */
( void ) vEventGroupDelete( ( EventGroupHandle_t ) &pxBarrier->xBarrierEventGroup );
( void ) vSemaphoreDelete( ( SemaphoreHandle_t ) &pxBarrier->xThreadCountSemaphore );
return 0;
}
/*-----------------------------------------------------------*/
int pthread_barrier_init( pthread_barrier_t * barrier,
const pthread_barrierattr_t * attr,
unsigned count )
{
int iStatus = 0;
pthread_barrier_internal_t * pxNewBarrier = ( pthread_barrier_internal_t * ) ( barrier );
/* Silence warnings about unused parameters. */
( void ) attr;
/* Ensure count is greater than 0. */
if( count == 0 )
{
iStatus = EINVAL;
}
/* Ensure that count will fit in a FreeRTOS event group. */
if( iStatus == 0 )
{
if( count > posixPTHREAD_BARRIER_MAX_COUNT )
{
/* No memory exists in the event group for more than
* posixPTHREAD_BARRIER_MAX_COUNT threads. */
iStatus = ENOMEM;
}
}
if( iStatus == 0 )
{
/* Set the current thread count and threshold. */
pxNewBarrier->uThreadCount = 0;
pxNewBarrier->uThreshold = count;
/* Create the FreeRTOS event group. This call will not fail when its
* argument isn't NULL. */
( void ) xEventGroupCreateStatic( &pxNewBarrier->xBarrierEventGroup );
/* Create the semaphore that prevents more than count threads from being
* unblocked by a single successful pthread_barrier_wait. This semaphore
* counts down from count and cannot decrement below 0. */
( void ) xSemaphoreCreateCountingStatic( ( UBaseType_t ) count, /* Max count. */
( UBaseType_t ) count, /* Initial count. */
&pxNewBarrier->xThreadCountSemaphore );
}
return iStatus;
}
/*-----------------------------------------------------------*/
int pthread_barrier_wait( pthread_barrier_t * barrier )
{
int iStatus = 0;
unsigned i = 0; /* Loop iterator. */
pthread_barrier_internal_t * pxBarrier = ( pthread_barrier_internal_t * ) ( barrier );
unsigned uThreadNumber = 0;
/* Decrement the number of threads waiting on this barrier. This will prevent more
* than pxBarrier->uThreshold threads from being unblocked by a single successful
* pthread_barrier_wait call.
*
* This call will never fail because it blocks forever.
*/
( void ) xSemaphoreTake( ( SemaphoreHandle_t ) &pxBarrier->xThreadCountSemaphore, portMAX_DELAY );
uThreadNumber = Atomic_Increment_u32( ( uint32_t * ) &pxBarrier->uThreadCount );
/* Set the bit in the event group representing this thread, then wait for the other
* threads to set their bit. This call should wait forever until all threads have set
* their bit, so the return value is ignored. */
( void ) xEventGroupSync( ( EventGroupHandle_t ) &pxBarrier->xBarrierEventGroup,
1 << uThreadNumber, /* Which bit in the event group to set. */
( 1 << pxBarrier->uThreshold ) - 1, /* Wait for all threads to set their bits. */
portMAX_DELAY );
/* The first thread to enter the barrier gets PTHREAD_BARRIER_SERIAL_THREAD as its
* return value and resets xThreadCountSemaphore. */
if( uThreadNumber == 0 )
{
iStatus = PTHREAD_BARRIER_SERIAL_THREAD;
/* uThreadCount can be safely changed without locking xThreadCountMutex
* because xThreadCountSemaphore is currently 0. */
pxBarrier->uThreadCount = 0;
/* Reset xThreadCountSemaphore. This allows more threads to enter the
* barrier, starting a new cycle. */
for( i = 0; i < pxBarrier->uThreshold; i++ )
{
xSemaphoreGive( ( SemaphoreHandle_t ) &pxBarrier->xThreadCountSemaphore );
}
}
return iStatus;
}
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