无锁栈实现一例
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一、何谓无锁队列无锁队列，顾名思义，即不需要加锁的队列；之所以不需要额外加锁，是因为其本身已经是线程安全的。
二、为什么要在队列中集成线程安全的机制？
这里我想采用对比的方式来讲述。有锁队列，这可能是最简单的一种队列了，比如我们在多线程情况下使用标准STD的deque，那么毫无疑问需要对其加锁。加锁其实是将协调过程交给了操作系统来管理，但无锁队列却是在CPU层面就做到了协调，所以在效率上会高很多。更详细的解释请参见http://www.searchtb.com/2012/10/introduction_to_disruptor.html
三、如何实现？
这里主要是采用ACS。
1. 定义队列。这里由于测试的缘故，队列节点内的数据比较简单。
/* ACS node define. */typedef struct acs_node_t { std::string id; int index; struct acs_node_t* next;} acs_node_t;/* ACS deque define. */typedef struct acs_deque_t { struct acs_node_t head; struct acs_node_t* tail;} acs_deque_t;void acs_deque_init(acs_deque_t* deq);int acs_deque_empty(acs_deque_t* deq);void acs_deque_push(acs_deque_t* deq, acs_node_t* node);acs_node_t* acs_deque_pop(acs_deque_t* deq);
void acs_deque_init(acs_deque_t* deq){ if (deq) { deq->tail = &deq->head; deq->head.next = NULL; }}int acs_deque_empty(acs_deque_t* deq){ if (!deq) return 1; return deq->head.next == NULL;}void acs_deque_push(acs_deque_t* deq, acs_node_t* node){ acs_node_t* q = NULL; do { q = deq->tail; } while (InterlockedCompareExchangePointer((PVOID*)&q->next, 0, node) != q->next); InterlockedCompareExchangePointer((PVOID*)&deq->tail, q, node);}acs_node_t* acs_deque_pop(acs_deque_t* deq){ acs_node_t* q = NULL; do { q = deq->head.next; if (q == NULL) return NULL; } while (InterlockedCompareExchangePointer((PVOID*)&deq->head.next, q, q->next) != deq->head.next); return q;}接口采用了Windows的ACS函数，当然你也可以将其更改为linux版本的ACS函数。4. 其他代码为测试代码，全部代码为
#include <stdio.h>#include <string>#define WIN32_LEAN_AND_MEAN#include <Windows.h>#include <deque>static const int knThreadCount = 4;static const int knMaxNodeCount = 50000;static const int knPopedCount = 5000;/* ACS node define. */typedef struct acs_node_t { std::string id; int index; struct acs_node_t* next;} acs_node_t;/* ACS deque define. */typedef struct acs_deque_t { struct acs_node_t head; struct acs_node_t* tail;} acs_deque_t;typedef struct DequeData { std::string id; int index;} DequeData;typedef std::deque<DequeData*> StdDeque;CRITICAL_SECTION g_stdcs;int g_aes_cost_time = 0;int g_std_cost_time = 0;class HRTimer {public: HRTimer(); ~HRTimer() {} double GetFrequency(void); void StartTimer(void); double StopTimer(void);private: LARGE_INTEGER start_; LARGE_INTEGER stop_; double frequency_;};HRTimer::HRTimer() : start_(), stop_(), frequency_(0.f){ frequency_ = this->GetFrequency();}double HRTimer::GetFrequency(void){ LARGE_INTEGER proc_freq; if (!::QueryPerformanceFrequency(&proc_freq)) return 0.f; return proc_freq.QuadPart;}void HRTimer::StartTimer(void){ HANDLE curth = ::GetCurrentThread(); DWORD_PTR oldmask = ::SetThreadAffinityMask(curth, 0); ::QueryPerformanceCounter(&start_); ::SetThreadAffinityMask(curth, oldmask);}double HRTimer::StopTimer(void){ HANDLE curth = ::GetCurrentThread(); DWORD_PTR oldmask = ::SetThreadAffinityMask(curth, 0); ::QueryPerformanceCounter(&stop_); ::SetThreadAffinityMask(curth, oldmask); return ((stop_.QuadPart - start_.QuadPart) / frequency_) * 1000;}class AutoHRTimer {public: AutoHRTimer(HRTimer& hrt, const char* name); ~AutoHRTimer();private: HRTimer& hrt_; const char* name_;};AutoHRTimer::AutoHRTimer(HRTimer& hrt, const char* name) : hrt_(hrt), name_(name){ hrt_.StartTimer();}AutoHRTimer::~AutoHRTimer(){ double diff = hrt_.StopTimer(); fprintf(stdout, "%s cost time %f ms\n", name_, diff);}HRTimer g_hrtimer;void acs_deque_init(acs_deque_t* deq);int acs_deque_empty(acs_deque_t* deq);void acs_deque_push(acs_deque_t* deq, acs_node_t* node);acs_node_t* acs_deque_pop(acs_deque_t* deq);void acs_deque_init(acs_deque_t* deq){ if (deq) { deq->tail = &deq->head; deq->head.next = NULL; }}int acs_deque_empty(acs_deque_t* deq){ if (!deq) return 1; return deq->head.next == NULL;}void acs_deque_push(acs_deque_t* deq, acs_node_t* node){ acs_node_t* q = NULL; do { q = deq->tail; } while (InterlockedCompareExchangePointer((PVOID*)&q->next, 0, node) != q->next); InterlockedCompareExchangePointer((PVOID*)&deq->tail, q, node);}acs_node_t* acs_deque_pop(acs_deque_t* deq){ acs_node_t* q = NULL; do { q = deq->head.next; if (q == NULL) return NULL; } while (InterlockedCompareExchangePointer((PVOID*)&deq->head.next, q, q->next) != deq->head.next); return q;}static DWORD AesThreadFunc(void* arg){ acs_deque_t* ad = (acs_deque_t*)arg; for (int i = 0; i < knMaxNodeCount; ++i) { acs_node_t* an = new acs_node_t; an->id = "randid_"; an->id.push_back((i % 10) + '0'); an->index = i; an->next = NULL; acs_deque_push(ad, an); } // for return 0;}static void TestAcsDeque(){ acs_deque_t ad; acs_node_t* poped_node = NULL; HANDLE th[knThreadCount]; { AutoHRTimer ahr(g_hrtimer, "ACS push 50000"); acs_deque_init(&ad); for (int i = 0; i < knThreadCount; ++i) { th[i] = CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)AesThreadFunc, &ad, 0, NULL); } // for ::WaitForMultipleObjects(knThreadCount, th, TRUE, INFINITE); } { // Test pop. AutoHRTimer ahr(g_hrtimer, "ACS pop 5000"); for (int i = 0; i < knPopedCount; ++i) { poped_node = acs_deque_pop(&ad); delete poped_node; } } { AutoHRTimer ahr(g_hrtimer, "ACS free 45000"); acs_node_t* cur = ad.head.next; while (cur != NULL) { acs_node_t* tmp = cur; cur = cur->next; delete tmp; } }}static DWORD StdThreadFunc(void* arg){ StdDeque* deq_list = (StdDeque*)arg; for (int i = 0; i < knMaxNodeCount; ++i) { DequeData* dd = new DequeData; dd->id = "randid_"; dd->id.push_back((i % 10) + '0'); dd->index = i; EnterCriticalSection(&g_stdcs); deq_list->push_back(dd); LeaveCriticalSection(&g_stdcs); } // for return 0;}static void TestLockedDeque(){ StdDeque deq_list; DequeData* poped_dd = NULL; HANDLE th[knThreadCount]; InitializeCriticalSectionAndSpinCount(&g_stdcs, 2000); { AutoHRTimer ahr(g_hrtimer, "STD push 50000"); for (int i = 0; i < knThreadCount; ++i) { th[i] = CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)StdThreadFunc, &deq_list, 0, NULL); } // for ::WaitForMultipleObjects(knThreadCount, th, TRUE, INFINITE); } { AutoHRTimer ahr(g_hrtimer, "STD pop 5000"); for (int i = 0; i < knPopedCount; ++i) { poped_dd = deq_list.front(); deq_list.pop_front(); delete poped_dd; } } { AutoHRTimer ahr(g_hrtimer, "STD free 45000"); StdDeque::iterator iter = deq_list.begin(); while (iter != deq_list.end()) { DequeData* dd = *iter; delete dd; ++iter; } deq_list.clear(); } DeleteCriticalSection(&g_stdcs);}int main(){ while (1) { TestAcsDeque(); TestLockedDeque(); Sleep(3000); fprintf(stdout, "--------------------------------------\n"); } getchar(); return 0;}5. 将无锁队列同std的有锁队列进行对比，效果如下图
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