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 // This file is not part of the public Skia API. 9 10 #ifndef SkSpinlock_DEFINED 11 #define SkSpinlock_DEFINED 12 13 #include "../private/SkAtomics.h" 14 15 #define SK_DECLARE_STATIC_SPINLOCK(name) namespace {} static SkPODSpinlock name 16 17 // This class has no constructor and must be zero-initialized (the macro above does this). 18 class SK_API SkPODSpinlock { 19 public: acquire()20 void acquire() { 21 // To act as a mutex, we need an acquire barrier if we take the lock. 22 if (sk_atomic_exchange(&fLocked, true, sk_memory_order_acquire)) { 23 // Lock was contended. Fall back to an out-of-line spin loop. 24 this->contendedAcquire(); 25 } 26 } 27 release()28 void release() { 29 // To act as a mutex, we need a release barrier. 30 sk_atomic_store(&fLocked, false, sk_memory_order_release); 31 } 32 33 private: 34 void contendedAcquire(); 35 bool fLocked; 36 }; 37 38 // For non-global-static use cases, this is normally what you want. 39 class SkSpinlock : public SkPODSpinlock { 40 public: SkSpinlock()41 SkSpinlock() { this->release(); } 42 }; 43 44 #endif//SkSpinlock_DEFINED 45