在《Java线程》这篇文章中说过使用CAS技术来实现自旋锁,C++中atomic的compare_exchange_strong()就是CAS技术的体现,另外还有TAS技术,TAS和CAS都是硬件同步的指令,只不过它俩的同步方式不太一样。atomic_flag的test_and_set()就是TAS技术的体现,test_and_set()会设置当前atomic_flag,并返回在这次设置之前是否已经被...
while(false==m_atomicState.compare_exchange_strong(state, emLocked)) { state=emUnlocked; } } voidunlock() { EM_LockState state=emLocked; while(false==m_atomicState.compare_exchange_strong(state, emUnlocked)) { state=emLocked; } } private: boost::atomic<EM_LockState>m_atomicState; }; ...
if ( std::atomic_compare_exchange_strong( &m_lTailIterator, &lTailIteratorOrig, lTailIterator )) { // Sets of sizeof(void*) are always atomic (you wont set a partial pointer). m_queue[lTailIteratorOrig] = NULL; // Gets of sizeof(void*) are always atomic (you wont get a partia...
程序是一个典型的生产者与消费者的关系,都可以使用多线程,其效率要比使用上层的互斥锁要快很多,因为它直接使用底层的原子操作来进行同步数据的。 freedeque.h 1#pragmaonce#ifndef INCLUDED_UTILS_LFRINGQUEUE2#defineINCLUDED_UTILS_LFRINGQUEUE34#define_ENABLE_ATOMIC_ALIGNMENT_FIX5#defineATOMIC_FLAG_INIT 0678#p...
error LNK2019: unresolved external symbol "__declspec(dllimport) void __cdecl std::_Debug_message(wchar_t const *,wchar_t const *,unsigned int)" (__imp_?_Debug_message@std@@YAXPEB_W0I@Z) referenced in function "int __cdecl std::_Atomic_compare_exchange_strong_4(unsigned long volatile...
从上面的分析,可以看出,多生产者,多消费者情形,它不同于单生产者,它需要考虑数据的实时变化,并且获取,然后比较操作,因此它经常使用atomic CAS来完成,而本文中涉及compare_exchange_weak和compare_exchange_strong原子操作,读者可以从源代码中感受一下这两者的使用区别。
error LNK2019: unresolved external symbol "__declspec(dllimport) void __cdecl std::_Debug_message(wchar_t const *,wchar_t const *,unsigned int)" (__imp_?_Debug_message@std@@YAXPEB_W0I@Z) referenced in function "int __cdecl std::_Atomic_compare_exchange_strong_4(unsigned long volatile...
tail_.compare_exchange_strong(tail, new_tail); } } } } Push图示 无锁队列Boost库Pop的源码和注释 template<typenameU> boolpop (U & ret) { usingdetail::likely; for(;;) { tagged_node_handle head = head_.load(memory_order_acquire); ...
unlock()时的release语义实际更像“刷新cache同步到内存”lock()是的acquire语义更像“从内存同步所有读...
*/booloverlay_initialized(booltoggle/* defaults to: false */){staticboost::atomic<bool> is_initilized(false);// writerif(toggle) {returnis_initilized.exchange(!is_initilized.load()); }// readerreturnis_initilized.load(); } 开发者ID:2510,项目名称:xtreemfs,代码行数:24,代码来源:preload....