Created
January 30, 2019 22:28
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A C++ shared Spinlock implementation
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| #pragma once | |
| #include <atomic> | |
| using namespace std; | |
| #ifdef _WIN32 | |
| #include <intrin.h> | |
| #pragma intrinsic(_InterlockedExchange) | |
| #define LOCK_TEST_AND_SET(_lock) _InterlockedExchange(&_lock, 1) | |
| #define LOCK_RELEASE(_lock) _InterlockedExchange(&_lock, 0) | |
| #else | |
| #define LOCK_TEST_AND_SET(_lock) __sync_lock_test_and_set(&_lock, 1) | |
| #define LOCK_RELEASE(_lock) __sync_lock_release(&_lock) | |
| #endif | |
| class Spinlock { | |
| private: | |
| std::atomic_flag flag; | |
| volatile long _write = 0; | |
| volatile atomic_int _read; | |
| void _lock() { | |
| while (true) { | |
| if (!LOCK_TEST_AND_SET(_write)) | |
| return; | |
| while (_write); | |
| } | |
| } | |
| public: | |
| Spinlock() : _read(false), flag(ATOMIC_FLAG_INIT) { } | |
| inline void lock() { | |
| while (flag.test_and_set(std::memory_order_acquire)); | |
| } | |
| inline void unlock() { | |
| flag.clear(std::memory_order_release); | |
| } | |
| inline void lockWrite() { | |
| bool w = false; | |
| while (true) { | |
| if (!w && !LOCK_TEST_AND_SET(_write)) { | |
| w = true; | |
| } | |
| if (w && !_read) { | |
| return; | |
| } | |
| while ((!w && _write) || _read); | |
| } | |
| } | |
| inline void unlockWrite() { | |
| LOCK_RELEASE(_write); | |
| } | |
| inline void lockRead() { | |
| lockWrite(); | |
| _read++; | |
| unlockWrite(); | |
| } | |
| inline void unlockRead() { | |
| _read--; | |
| } | |
| }; |
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