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/*
* Copyright (c) 2019-2020 Arm Limited.
*
* SPDX-License-Identifier: MIT
*
* 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.
*/
#pragma once
#ifndef NO_MULTI_THREADING
#include <atomic>
namespace arm_gemm {
class barrier {
private:
unsigned int m_threads;
std::atomic<unsigned int> m_waiters;
std::atomic<unsigned int> m_leavers;
public:
barrier(unsigned int threads) : m_threads(threads), m_waiters(0), m_leavers(0) { }
/* This isn't safe if any thread is waiting... */
void set_nthreads(unsigned int nthreads) {
m_threads = nthreads;
}
void arrive_and_wait() {
m_waiters++;
while (m_waiters != m_threads) {
; /* spin */
}
unsigned int v = m_leavers.fetch_add(1);
if (v == (m_threads - 1)) {
m_waiters -= m_threads;
m_leavers = 0;
} else {
while (m_leavers > 0) {
; /* spin */
}
}
}
};
} // namespace arm_gemm
#else
namespace arm_gemm {
class barrier {
public:
barrier(unsigned int) { }
void arrive_and_wait() { }
void set_nthreads(unsigned int ) { }
};
} // namespace arm_gemm
#endif
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