mirror of
https://github.com/mutouyun/cpp-ipc.git
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116 lines
3.4 KiB
C++
116 lines
3.4 KiB
C++
#pragma once
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#include <atomic>
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#include <thread>
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#include <chrono>
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#include <limits>
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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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#pragma push_macro("IPC_LOCK_PAUSE_")
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#undef IPC_LOCK_PAUSE_
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#if defined(_MSC_VER)
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#include <windows.h> // YieldProcessor
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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 IPC_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 IPC_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 IPC_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 IPC_LOCK_PAUSE_() __asm__ __volatile__ ("yield")
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#endif
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#endif/*compilers*/
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#if !defined(IPC_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 IPC_LOCK_PAUSE_() std::atomic_signal_fence(std::memory_order_seq_cst)
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#endif/*!defined(IPC_LOCK_PAUSE_)*/
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////////////////////////////////////////////////////////////////
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/// Yield to other threads
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////////////////////////////////////////////////////////////////
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namespace ipc {
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inline void yield(unsigned k) {
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if (k < 4) { /* Do nothing */ }
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else
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if (k < 16) { IPC_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 ipc
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#pragma pop_macro("IPC_LOCK_PAUSE_")
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namespace ipc {
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class rw_lock {
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std::atomic_size_t lc_ { 0 };
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enum : std::size_t {
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w_flag = (std::numeric_limits<std::size_t>::max)()
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};
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public:
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void lock() {
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for (unsigned k = 0;; ++k) {
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std::size_t expected = 0;
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if (lc_.compare_exchange_weak(expected, w_flag, std::memory_order_acq_rel)) {
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break;
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}
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yield(k);
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}
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}
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void unlock() {
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lc_.store(0, std::memory_order_release);
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}
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void lock_shared() {
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for (unsigned k = 0;; ++k) {
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std::size_t old = lc_.load(std::memory_order_relaxed);
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std::size_t unlocked = old + 1;
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if (unlocked &&
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lc_.compare_exchange_weak(old, unlocked, std::memory_order_acq_rel)) {
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break;
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}
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yield(k);
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std::atomic_thread_fence(std::memory_order_acquire);
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}
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}
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void unlock_shared() {
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lc_.fetch_sub(1, std::memory_order_release);
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}
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};
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} // namespace ipc
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