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/* Copyright (c) 2013, Linaro Limited
* All rights reserved.
*
* SPDX-License-Identifier: BSD-3-Clause
*/
#include "config.h"
#include <odp/api/barrier.h>
#include <odp/api/sync.h>
#include <odp/api/cpu.h>
#include <odp/api/atomic.h>
void odp_barrier_init(odp_barrier_t *barrier, int count)
{
barrier->count = (uint32_t)count;
odp_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 odp_barrier_wait(odp_barrier_t *barrier)
{
uint32_t count;
int wasless;
odp_mb_release();
count = odp_atomic_fetch_inc_u32(&barrier->bar);
wasless = count < barrier->count;
if (count == 2 * barrier->count - 1) {
/* Wrap around *atomically* */
odp_atomic_sub_u32(&barrier->bar, 2 * barrier->count);
} else {
while ((odp_atomic_load_u32(&barrier->bar) < barrier->count)
== wasless)
odp_cpu_pause();
}
odp_mb_acquire();
}
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