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   * Copyright (c) 2011, Duane Merrill.  All rights reserved.
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  /**
   * \file
   * Simple portable mutex
   */
  
  
  #pragma once
  
  #if (__cplusplus > 199711L) || (defined(_MSC_VER) && _MSC_VER >= 1800)
      #include <mutex>
  #else
      #if defined(_WIN32) || defined(_WIN64)
          #include <intrin.h>
  
          #define WIN32_LEAN_AND_MEAN
          #define NOMINMAX
          #include <windows.h>
          #undef WIN32_LEAN_AND_MEAN
          #undef NOMINMAX
  
          /**
           * Compiler read/write barrier
           */
          #pragma intrinsic(_ReadWriteBarrier)
  
      #endif
  #endif
  
  #include "../util_namespace.cuh"
  
  
  /// Optional outer namespace(s)
  CUB_NS_PREFIX
  
  /// CUB namespace
  namespace cub {
  
  
  /**
   * Simple portable mutex
   *   - Wraps std::mutex when compiled with C++11 or newer (supported on all platforms)
   *   - Uses GNU/Windows spinlock mechanisms for pre C++11 (supported on x86/x64 when compiled with cl.exe or g++)
   */
  struct Mutex
  {
  #if (__cplusplus > 199711L) || (defined(_MSC_VER) && _MSC_VER >= 1800)
  
      std::mutex mtx;
  
      void Lock()
      {
          mtx.lock();
      }
  
      void Unlock()
      {
          mtx.unlock();
      }
  
      void TryLock()
      {
          mtx.try_lock();
      }
  
  #else       //__cplusplus > 199711L
  
      #if defined(_MSC_VER)
  
          // Microsoft VC++
          typedef long Spinlock;
  
      #else
  
          // GNU g++
          typedef int Spinlock;
  
          /**
           * Compiler read/write barrier
           */
          __forceinline__ void _ReadWriteBarrier()
          {
              __sync_synchronize();
          }
  
          /**
           * Atomic exchange
           */
          __forceinline__ long _InterlockedExchange(volatile int * const Target, const int Value)
          {
              // NOTE: __sync_lock_test_and_set would be an acquire barrier, so we force a full barrier
              _ReadWriteBarrier();
              return __sync_lock_test_and_set(Target, Value);
          }
  
          /**
           * Pause instruction to prevent excess processor bus usage
           */
          __forceinline__ void YieldProcessor()
          {
          }
  
      #endif  // defined(_MSC_VER)
  
          /// Lock member
          volatile Spinlock lock;
  
          /**
           * Constructor
           */
          Mutex() : lock(0) {}
  
          /**
           * Return when the specified spinlock has been acquired
           */
          __forceinline__ void Lock()
          {
              while (1)
              {
                  if (!_InterlockedExchange(&lock, 1)) return;
                  while (lock) YieldProcessor();
              }
          }
  
  
          /**
           * Release the specified spinlock
           */
          __forceinline__ void Unlock()
          {
              _ReadWriteBarrier();
              lock = 0;
          }
  
  #endif      // __cplusplus > 199711L
  
  };
  
  
  
  
  }               // CUB namespace
  CUB_NS_POSTFIX  // Optional outer namespace(s)