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https://github.com/libretro/beetle-psx-libretro.git
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96 lines
2.4 KiB
C++
96 lines
2.4 KiB
C++
/* Copyright (c) 2017-2018 Hans-Kristian Arntzen
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*
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* Permission is hereby granted, free of charge, to any person obtaining
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* a copy of this software and associated documentation files (the
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* "Software"), to deal in the Software without restriction, including
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* without limitation the rights to use, copy, modify, merge, publish,
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* distribute, sublicense, and/or sell copies of the Software, and to
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* permit persons to whom the Software is furnished to do so, subject to
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* the following conditions:
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*
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* The above copyright notice and this permission notice shall be
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* included in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
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* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
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* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
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* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
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* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
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* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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*/
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#pragma once
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#include <atomic>
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#ifdef __SSE2__
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#include <emmintrin.h>
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#endif
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namespace Util
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{
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class RWSpinLock
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{
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public:
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enum { Reader = 2, Writer = 1 };
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RWSpinLock()
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{
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counter.store(0);
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}
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inline void lock_read()
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{
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unsigned v = counter.fetch_add(Reader, std::memory_order_acquire);
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while ((v & Writer) != 0)
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{
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#ifdef __SSE2__
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_mm_pause();
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#endif
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v = counter.load(std::memory_order_acquire);
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}
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}
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inline void unlock_read()
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{
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counter.fetch_sub(Reader, std::memory_order_release);
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}
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inline void lock_write()
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{
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uint32_t expected = 0;
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while (!counter.compare_exchange_weak(expected, Writer,
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std::memory_order_acquire,
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std::memory_order_relaxed))
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{
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#ifdef __SSE2__
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_mm_pause();
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#endif
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expected = 0;
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}
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}
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inline void unlock_write()
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{
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counter.fetch_and(~Writer, std::memory_order_release);
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}
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inline void promote_reader_to_writer()
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{
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uint32_t expected = Reader;
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while (!counter.compare_exchange_weak(expected, Writer,
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std::memory_order_acquire,
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std::memory_order_relaxed))
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{
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#ifdef __SSE2__
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_mm_pause();
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#endif
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expected = Reader;
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}
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}
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private:
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std::atomic<uint32_t> counter;
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};
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}
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