1 /* 2 * Copyright 2015 Google Inc. 3 * 4 * Use of this source code is governed by a BSD-style license that can be 5 * found in the LICENSE file. 6 */ 7 8 #ifndef SkSpinlock_DEFINED 9 #define SkSpinlock_DEFINED 10 11 #include "SkTypes.h" 12 #include <atomic> 13 14 class SkSpinlock { 15 public: 16 constexpr SkSpinlock() = default; 17 18 void acquire() { 19 // To act as a mutex, we need an acquire barrier when we acquire the lock. 20 if (fLocked.exchange(true, std::memory_order_acquire)) { 21 // Lock was contended. Fall back to an out-of-line spin loop. 22 this->contendedAcquire(); 23 } 24 } 25 26 // Acquire the lock or fail (quickly). Lets the caller decide to do something other than wait. 27 bool tryAcquire() { 28 // To act as a mutex, we need an acquire barrier when we acquire the lock. 29 if (fLocked.exchange(true, std::memory_order_acquire)) { 30 // Lock was contended. Let the caller decide what to do. 31 return false; 32 } 33 return true; 34 } 35 36 void release() { 37 // To act as a mutex, we need a release barrier when we release the lock. 38 fLocked.store(false, std::memory_order_release); 39 } 40 41 private: 42 SK_API void contendedAcquire(); 43 44 std::atomic<bool> fLocked{false}; 45 }; 46 47 #endif//SkSpinlock_DEFINED 48
