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xgboost/cub/cub/host/mutex.cuh  view on Meta::CPAN

#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

    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)