105 lines
3.1 KiB
C++
105 lines
3.1 KiB
C++
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/*
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The Capo Library
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Code covered by the MIT License
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Author: mutouyun (http://orzz.org)
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*/
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#pragma once
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#include <atomic> // std::atomic_flag, std::atomic_signal_fence
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#include <thread> // std::this_thread
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#include <chrono> // std::chrono::milliseconds
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#if defined(_MSC_VER)
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#include <windows.h> // YieldProcessor
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#endif/*_MSC_VER*/
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namespace capo {
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namespace detail_spin_lock {
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////////////////////////////////////////////////////////////////
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/// Gives hint to processor that improves performance of spin-wait loops.
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////////////////////////////////////////////////////////////////
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#if defined(_MSC_VER)
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/*
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See: http://msdn.microsoft.com/en-us/library/windows/desktop/ms687419(v=vs.85).aspx
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Not for intel c++ compiler, so ignore http://software.intel.com/en-us/forums/topic/296168
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*/
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# define CAPO_SPIN_LOCK_PAUSE_() YieldProcessor()
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#elif defined(__GNUC__)
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#if defined(__i386__) || defined(__x86_64__)
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/*
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See: Intel(R) 64 and IA-32 Architectures Software Developer's Manual V2
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PAUSE-Spin Loop Hint, 4-57
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http://www.intel.com/content/www/us/en/architecture-and-technology/64-ia-32-architectures-software-developer-instruction-set-reference-manual-325383.html?wapkw=instruction+set+reference
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*/
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# define CAPO_SPIN_LOCK_PAUSE_() __asm__ __volatile__("pause")
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#elif defined(__ia64__) || defined(__ia64)
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/*
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See: Intel(R) Itanium(R) Architecture Developer's Manual, Vol.3
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hint - Performance Hint, 3:145
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http://www.intel.com/content/www/us/en/processors/itanium/itanium-architecture-vol-3-manual.html
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*/
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# define CAPO_SPIN_LOCK_PAUSE_() __asm__ __volatile__ ("hint @pause")
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#elif defined(__arm__)
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/*
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See: ARM Architecture Reference Manuals (YIELD)
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http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.subset.architecture.reference/index.html
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*/
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# define CAPO_SPIN_LOCK_PAUSE_() __asm__ __volatile__ ("yield")
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#endif
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#endif/*compilers*/
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#if !defined(CAPO_SPIN_LOCK_PAUSE_)
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/*
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Just use a compiler fence, prevent compiler from optimizing loop
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*/
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# define CAPO_SPIN_LOCK_PAUSE_() std::atomic_signal_fence(std::memory_order_seq_cst)
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#endif/*!defined(CAPO_SPIN_LOCK_PAUSE_)*/
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////////////////////////////////////////////////////////////////
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/// Yield to other threads
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////////////////////////////////////////////////////////////////
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inline void yield(unsigned k)
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{
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if (k < 4) { /* Do nothing */ }
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else
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if (k < 16) { CAPO_SPIN_LOCK_PAUSE_(); }
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else
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if (k < 32) { std::this_thread::yield(); }
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else
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{ std::this_thread::sleep_for(std::chrono::milliseconds(1)); }
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}
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} // namespace detail_spin_lock
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////////////////////////////////////////////////////////////////
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/// Spinlock
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////////////////////////////////////////////////////////////////
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class spin_lock
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{
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std::atomic_flag lc_ = ATOMIC_FLAG_INIT;
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public:
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bool try_lock(void)
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{
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return !lc_.test_and_set(std::memory_order_acquire);
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}
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void lock(void)
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{
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for (unsigned k = 0; lc_.test_and_set(std::memory_order_acquire); ++k)
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detail_spin_lock::yield(k);
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}
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void unlock(void)
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{
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lc_.clear(std::memory_order_release);
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}
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};
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} // namespace capo
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