Line data    Source code

       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           3 :     constexpr SkSpinlock() = default;
      17             : 
      18          47 :     void acquire() {
      19             :         // To act as a mutex, we need an acquire barrier when we acquire the lock.
      20          47 :         if (fLocked.exchange(true, std::memory_order_acquire)) {
      21             :             // Lock was contended.  Fall back to an out-of-line spin loop.
      22           0 :             this->contendedAcquire();
      23             :         }
      24          47 :     }
      25             : 
      26             :     // Acquire the lock or fail (quickly). Lets the caller decide to do something other than wait.
      27           0 :     bool tryAcquire() {
      28             :         // To act as a mutex, we need an acquire barrier when we acquire the lock.
      29           0 :         if (fLocked.exchange(true, std::memory_order_acquire)) {
      30             :             // Lock was contended. Let the caller decide what to do.
      31           0 :             return false;
      32             :         }
      33           0 :         return true;
      34             :     }
      35             : 
      36          47 :     void release() {
      37             :         // To act as a mutex, we need a release barrier when we release the lock.
      38          47 :         fLocked.store(false, std::memory_order_release);
      39          47 :     }
      40             : 
      41             : private:
      42             :     SK_API void contendedAcquire();
      43             : 
      44             :     std::atomic<bool> fLocked{false};
      45             : };
      46             : 
      47             : #endif//SkSpinlock_DEFINED