| /* |
| * Copyright 2015 Google Inc. |
| * |
| * Use of this source code is governed by a BSD-style license that can be |
| * found in the LICENSE file. |
| */ |
| |
| #ifndef SkSpinlock_DEFINED |
| #define SkSpinlock_DEFINED |
| |
| #include "include/core/SkTypes.h" |
| #include "include/private/base/SkThreadAnnotations.h" |
| #include <atomic> |
| |
| class SK_CAPABILITY("mutex") SkSpinlock { |
| public: |
| constexpr SkSpinlock() = default; |
| |
| void acquire() SK_ACQUIRE() { |
| // To act as a mutex, we need an acquire barrier when we acquire the lock. |
| if (fLocked.exchange(true, std::memory_order_acquire)) { |
| // Lock was contended. Fall back to an out-of-line spin loop. |
| this->contendedAcquire(); |
| } |
| } |
| |
| // Acquire the lock or fail (quickly). Lets the caller decide to do something other than wait. |
| bool tryAcquire() SK_TRY_ACQUIRE(true) { |
| // To act as a mutex, we need an acquire barrier when we acquire the lock. |
| if (fLocked.exchange(true, std::memory_order_acquire)) { |
| // Lock was contended. Let the caller decide what to do. |
| return false; |
| } |
| return true; |
| } |
| |
| void release() SK_RELEASE_CAPABILITY() { |
| // To act as a mutex, we need a release barrier when we release the lock. |
| fLocked.store(false, std::memory_order_release); |
| } |
| |
| private: |
| SK_API void contendedAcquire(); |
| |
| std::atomic<bool> fLocked{false}; |
| }; |
| |
| class SK_SCOPED_CAPABILITY SkAutoSpinlock { |
| public: |
| SkAutoSpinlock(SkSpinlock& mutex) SK_ACQUIRE(mutex) : fSpinlock(mutex) { fSpinlock.acquire(); } |
| ~SkAutoSpinlock() SK_RELEASE_CAPABILITY() { fSpinlock.release(); } |
| |
| private: |
| SkSpinlock& fSpinlock; |
| }; |
| |
| #endif//SkSpinlock_DEFINED |