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 "include/core/SkTypes.h"
12#include "include/private/SkThreadAnnotations.h"
13#include <atomic>
14
15class SK_CAPABILITY("mutex") SkSpinlock {
16public:
17 constexpr SkSpinlock() = default;
18
19 void acquire() SK_ACQUIRE() {
20 // To act as a mutex, we need an acquire barrier when we acquire the lock.
21 if (fLocked.exchange(true, std::memory_order_acquire)) {
22 // Lock was contended. Fall back to an out-of-line spin loop.
23 this->contendedAcquire();
24 }
25 }
26
27 // Acquire the lock or fail (quickly). Lets the caller decide to do something other than wait.
28 bool tryAcquire() SK_TRY_ACQUIRE(true) {
29 // To act as a mutex, we need an acquire barrier when we acquire the lock.
30 if (fLocked.exchange(true, std::memory_order_acquire)) {
31 // Lock was contended. Let the caller decide what to do.
32 return false;
33 }
34 return true;
35 }
36
37 void release() SK_RELEASE_CAPABILITY() {
38 // To act as a mutex, we need a release barrier when we release the lock.
39 fLocked.store(false, std::memory_order_release);
40 }
41
42private:
43 SK_API void contendedAcquire();
44
45 std::atomic<bool> fLocked{false};
46};
47
48class SK_SCOPED_CAPABILITY SkAutoSpinlock {
49public:
50 SkAutoSpinlock(SkSpinlock& mutex) SK_ACQUIRE(mutex) : fSpinlock(mutex) { fSpinlock.acquire(); }
51 ~SkAutoSpinlock() SK_RELEASE_CAPABILITY() { fSpinlock.release(); }
52
53private:
54 SkSpinlock& fSpinlock;
55};
56
57#endif//SkSpinlock_DEFINED
58