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/* Copyright (c) 2016, Linaro Limited
* All rights reserved.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
#include <odp/drv/barrier.h>
#include <odp/drv/sync.h>
#include <odp/api/cpu.h>
#include <odp/drv/atomic.h>
void odpdrv_barrier_init(odpdrv_barrier_t *barrier, int count)
{
barrier->count = (uint32_t)count;
odpdrv_atomic_init_u32(&barrier->bar, 0);
}
/*
* Efficient barrier_sync -
*
* Barriers are initialized with a count of the number of callers
* that must sync on the barrier before any may proceed.
*
* To avoid race conditions and to permit the barrier to be fully
* reusable, the barrier value cycles between 0..2*count-1. When
* synchronizing the wasless variable simply tracks which half of
* the cycle the barrier was in upon entry. Exit is when the
* barrier crosses to the other half of the cycle.
*/
void odpdrv_barrier_wait(odpdrv_barrier_t *barrier)
{
uint32_t count;
int wasless;
odpdrv_mb_full();
count = odpdrv_atomic_fetch_inc_u32(&barrier->bar);
wasless = count < barrier->count;
if (count == 2 * barrier->count - 1) {
/* Wrap around *atomically* */
odpdrv_atomic_sub_u32(&barrier->bar, 2 * barrier->count);
} else {
while ((odpdrv_atomic_load_u32(&barrier->bar) < barrier->count)
== wasless)
odp_cpu_pause();
}
odpdrv_mb_full();
}
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