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