{"id":7667,"date":"2026-08-18T13:48:04","date_gmt":"2026-08-18T05:48:04","guid":{"rendered":"https:\/\/i007.cc\/wordpress\/?p=7667"},"modified":"2026-08-18T13:51:30","modified_gmt":"2026-08-18T05:51:30","slug":"%e6%97%a0%e9%94%81%e9%98%9f%e5%88%97%ef%bc%88lock-free-queue%ef%bc%89%e5%ae%9e%e7%8e%b0%e8%af%a6%e8%a7%a3","status":"publish","type":"post","link":"https:\/\/i007.cc\/wordpress\/archives\/7667","title":{"rendered":"\u65e0\u9501\u961f\u5217\uff08Lock-Free Queue\uff09\u5b9e\u73b0\u8be6\u89e3"},"content":{"rendered":"
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\u65e0\u9501\u961f\u5217\u662f\u5e76\u53d1\u7f16\u7a0b\u4e2d\u7684\u9ad8\u9891\u9762\u8bd5\u9898\uff0c\u5c24\u5176\u5728\u4e91\u57fa\u7840\u8bbe\u65bd\u3001\u9ad8\u6027\u80fd\u4e2d\u95f4\u4ef6\u573a\u666f\u4e2d\u5fc5\u8003\u3002\u4ee5\u4e0b\u4ece\u539f\u7406\u5230\u5b9e\u73b0\u9010\u5c42\u62c6\u89e3\u3002<\/span><\/h1>\n<\/div>\n
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\u4e00\u3001\u4e3a\u4ec0\u4e48\u9700\u8981\u65e0\u9501\u961f\u5217<\/h2>\n<\/div>\n
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\u4f20\u7edf\u4e92\u65a5\u9501\u961f\u5217\u7684\u95ee\u9898\uff1a<\/div>\n<\/div>\n
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  • \u963b\u585e<\/strong>\uff1a\u7ebf\u7a0b\u62ff\u4e0d\u5230\u9501\u5c31\u7761\u7720\uff0c\u4e0a\u4e0b\u6587\u5207\u6362\u5f00\u9500\u5927\uff08~1-5\u03bcs\uff09<\/li>\n
  • \u4f18\u5148\u7ea7\u53cd\u8f6c<\/strong>\uff1a\u4f4e\u4f18\u5148\u7ea7\u7ebf\u7a0b\u6301\u9501\uff0c\u9ad8\u4f18\u5148\u7ea7\u7ebf\u7a0b\u963b\u585e<\/li>\n
  • \u6b7b\u9501\u98ce\u9669<\/strong>\uff1a\u591a\u9501\u573a\u666f\u5bb9\u6613\u51fa\u9519<\/li>\n
  • \u4e0d\u53ef\u91cd\u5165<\/strong>\uff1a\u4fe1\u53f7\u5904\u7406\u51fd\u6570\u4e2d\u4e0d\u80fd\u7528\u9501<\/li>\n<\/ul>\n<\/div>\n
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    \u65e0\u9501\u961f\u5217\u7684\u6838\u5fc3\u4fdd\u8bc1\uff1a\u67d0\u4e2a\u7ebf\u7a0b\u7684\u5ef6\u8fdf\u6216\u5d29\u6e83\u4e0d\u4f1a\u963b\u585e\u5176\u4ed6\u7ebf\u7a0b\u7684\u63a8\u8fdb<\/strong>\uff08obstruction-free \/lock-free\/wait-free \u4e09\u7ea7\uff09\u3002<\/div>\n<\/div>\n
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    \u4e8c\u3001\u6838\u5fc3\u539f\u8bed<\/h2>\n<\/div>\n
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    1. CAS\uff08Compare-And-Swap\uff09<\/h3>\n<\/div>\n
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    bool CAS(addr, expected, desired):\r\n    if *addr == expected:\r\n        *addr = desired\r\n        return true\r\n    return false<\/pre>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n
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    C++11 \u5bf9\u5e94 std::atomic::compare_exchange_weak\/strong<\/code>\u3002<\/div>\n<\/div>\n
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    2. \u5185\u5b58\u5e8f\uff08Memory Order\uff09<\/h3>\n<\/div>\n
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    \u8fd9\u662f\u9762\u8bd5\u6df1\u6c34\u533a\uff0c\u5fc5\u987b\u8bb2\u6e05\u695a\uff1a<\/div>\n<\/div>\n
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    \u8868\u683c<\/div>\n
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    <\/div>\n<\/div>\n<\/div>\n
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    \n\n\n\n\n\n\n\n\n\n
    \u5185\u5b58\u5e8f<\/th>\n\u542b\u4e49<\/th>\n\u961f\u5217\u4e2d\u7528\u9014<\/th>\n<\/tr>\n<\/thead>\n
    relaxed<\/code><\/td>\n\u53ea\u4fdd\u8bc1\u539f\u5b50\u6027\uff0c\u4e0d\u4fdd\u8bc1\u987a\u5e8f<\/td>\n\u8ba1\u6570\u5668\u3001\u7edf\u8ba1\u5b57\u6bb5<\/td>\n<\/tr>\n
    acquire<\/code><\/td>\n\u8bfb\u4e4b\u540e\u7684\u64cd\u4f5c\u4e0d\u80fd\u91cd\u6392\u5230\u8bfb\u4e4b\u524d<\/td>\n\u51fa\u961f\u8bfb head<\/td>\n<\/tr>\n
    release<\/code><\/td>\n\u5199\u4e4b\u524d\u7684\u64cd\u4f5c\u4e0d\u80fd\u91cd\u6392\u5230\u5199\u4e4b\u540e<\/td>\n\u5165\u961f\u5199 tail<\/td>\n<\/tr>\n
    acq_rel<\/code><\/td>\n\u517c\u5177 acquire + release<\/td>\nCAS \u64cd\u4f5c<\/td>\n<\/tr>\n
    seq_cst<\/code><\/td>\n\u5168\u5c40\u5168\u5e8f<\/td>\n\u9ed8\u8ba4\uff0c\u6700\u4fdd\u5b88\uff0c\u6027\u80fd\u6700\u5dee<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n
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    \u5173\u952e\u914d\u5bf9<\/strong>\uff1a\u4e00\u4e2a\u7ebf\u7a0b release<\/code> \u5199\uff0c\u53e6\u4e00\u4e2a\u7ebf\u7a0b acquire<\/code> \u8bfb\uff0c\u5f62\u6210 synchronizes-with<\/em> \u5173\u7cfb\uff0c\u4fdd\u8bc1\u53ef\u89c1\u6027\u3002<\/div>\n<\/div>\n
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    3. ABA \u95ee\u9898<\/h3>\n<\/div>\n
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    \u7ebf\u7a0b 1 \u8bfb A<\/code>\uff0c\u51c6\u5907 CAS\uff1b\u671f\u95f4\u7ebf\u7a0b 2 \u6539\u6210 B<\/code> \u53c8\u6539\u56de A<\/code>\uff1b\u7ebf\u7a0b 1 \u7684 CAS \u6210\u529f\u4f46\u72b6\u6001\u5df2\u53d8\u3002<\/div>\n<\/div>\n
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    \u89e3\u51b3\u65b9\u6848<\/strong>\uff1a<\/div>\n<\/div>\n
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    • \u6807\u8bb0\u6307\u9488\uff08Tagged Pointer\uff09<\/strong>\uff1a\u6307\u9488 + \u7248\u672c\u53f7\u6253\u5305\u6210\u4e00\u4e2a 64 \u4f4d\u503c\uff08\u5229\u7528 64 \u4f4d\u5730\u5740\u4f4e\u51e0\u4f4d\u672a\u4f7f\u7528\uff09<\/li>\n
    • DCAS\uff08Double CAS\uff09<\/strong>\uff1a\u540c\u65f6\u6bd4\u8f83\u6307\u9488\u548c\u7248\u672c\u53f7<\/li>\n
    • ** Hazard Pointer \/ Epoch-based Reclamation**\uff1a\u5b89\u5168\u5185\u5b58\u56de\u6536<\/li>\n<\/ul>\n<\/div>\n
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      \u4e09\u3001\u7ecf\u5178\u5b9e\u73b0\uff1aMichael-Scott Queue\uff081996\uff09<\/h2>\n<\/div>\n
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      \u8fd9\u662f\u6700\u7ecf\u5178\u7684\u65e0\u9501\u961f\u5217\u7b97\u6cd5<\/strong>\uff0cJava ConcurrentLinkedQueue<\/code>\u3001Boost lockfree::queue<\/code> \u90fd\u57fa\u4e8e\u5b83\u3002\u9762\u8bd5\u8bb2\u8fd9\u4e2a\u6700\u7a33\u59a5\u3002<\/div>\n<\/div>\n
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      \u7b97\u6cd5\u6838\u5fc3<\/h3>\n<\/div>\n
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      • \u94fe\u8868\u7ed3\u6784\uff0chead<\/code> \u548c tail<\/code> \u90fd\u662f\u539f\u5b50\u6307\u9488<\/li>\n
      • \u5165\u961f\u53ea\u64cd\u4f5c tail<\/code>\uff0c\u51fa\u961f\u53ea\u64cd\u4f5c head<\/code>\uff0c\u4e24\u8005\u7ade\u4e89\u6700\u5c0f<\/li>\n
      • \u4f7f\u7528 dummy node\uff08\u54e8\u5175\u8282\u70b9\uff09<\/strong> \u907f\u514d head\/tail \u5728\u7a7a\u961f\u5217\u65f6\u91cd\u5408\u7684\u8fb9\u754c\u95ee\u9898<\/li>\n<\/ul>\n<\/div>\n
        \n
        \u5165\u961f\uff08Enqueue\uff09<\/h3>\n<\/div>\n
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        plaintext<\/div>\n
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        1. \u65b0\u5efa\u8282\u70b9 node\uff0cnext = nullptr\r\n2. \u5faa\u73af\uff1a\r\n   a. \u8bfb\u53d6 tail = this->tail\r\n   b. \u8bfb\u53d6 next = tail->next\r\n   c. \u5982\u679c tail \u6ca1\u53d8\uff08\u53cc\u91cd\u68c0\u67e5\uff09\uff1a\r\n      - \u5982\u679c next == nullptr\uff1a\r\n          CAS(tail->next, nullptr, node)  \/\/ \u5c1d\u8bd5\u628a\u65b0\u8282\u70b9\u6302\u5230 tail \u540e\u9762\r\n          \u6210\u529f\u5219 CAS(tail, tail, node)   \/\/ \u63a8\u8fdb tail\uff08\u53ef\u80fd\u5931\u8d25\uff0c\u6ca1\u5173\u7cfb\uff09\r\n          \u8fd4\u56de\r\n      - \u5426\u5219\uff1a\r\n          CAS(tail, tail, next)  \/\/ \u5e2e\u5176\u4ed6\u7ebf\u7a0b\u63a8\u8fdb tail\uff08\u8f85\u52a9\u673a\u5236\uff09<\/pre>\n
         <\/p>\n<\/div>\n<\/div>\n<\/div>\n
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        \u6ce8\u610f\uff1atail \u53ef\u80fd\u6ede\u540e<\/strong>\u3002\u5982\u679c\u5165\u961f\u7ebf\u7a0b CAS tail \u5931\u8d25\uff0c\u8bf4\u660e\u53e6\u4e00\u4e2a\u7ebf\u7a0b\u5df2\u7ecf\u63a8\u8fdb\u4e86\uff0c\u4e0b\u4e00\u6b21\u5faa\u73af\u4f1a\u8bfb\u5230\u65b0\u7684 tail\u3002<\/div>\n<\/div>\n
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        \u51fa\u961f\uff08Dequeue\uff09<\/h3>\n<\/div>\n
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        plaintext<\/div>\n
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        1. \u5faa\u73af\uff1a\r\n   a. \u8bfb\u53d6 head = this->head\r\n   b. \u8bfb\u53d6 tail = this->tail\r\n   c. \u8bfb\u53d6 next = head->next\r\n   d. \u5982\u679c head \u6ca1\u53d8\uff1a\r\n      - \u5982\u679c head == tail\uff1a\r\n          \u5982\u679c next == nullptr\uff1a\u961f\u5217\u4e3a\u7a7a\uff0c\u8fd4\u56de false\r\n          \u5426\u5219\uff1aCAS(tail, tail, next)  \/\/ \u5e2e\u63a8\u8fdb tail\r\n      - \u5426\u5219\uff1a\r\n          \u8bfb\u53d6 next->value\r\n          \u5982\u679c CAS(head, head, next) \u6210\u529f\uff1a\r\n              \u91ca\u653e\u65e7 head\uff08\u9700\u8981\u5b89\u5168\u56de\u6536\u673a\u5236\uff09\r\n              \u8fd4\u56de value<\/pre>\n
         <\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n
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        C++ \u5b8c\u6574\u5b9e\u73b0\uff08\u5e26\u7248\u672c\u53f7\u89e3\u51b3 ABA\uff09<\/h3>\n<\/div>\n
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        cpp<\/div>\n
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        \u8fd0\u884c<\/div>\n
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        #include <atomic>\r\n#include <cstdint>\r\n#include <utility>\r\n\r\ntemplate <typename T>\r\nclass MichaelScottQueue {\r\nprivate:\r\n    struct Node {\r\n        T value;\r\n        std::atomic<Node*> next;\r\n        Node(T v) : value(std::move(v)), next(nullptr) {}\r\n        Node() : value{}, next(nullptr) {}  \/\/ dummy node\r\n    };\r\n\r\n    \/\/ \u7528 64 \u4f4d\u6253\u5305\u6307\u9488 + \u7248\u672c\u53f7\uff08\u5047\u8bbe\u6307\u9488\u9ad816\u4f4d\u53ef\u7528\uff0c\u5b9e\u9645\u9700\u6839\u636e\u5e73\u53f0\u8c03\u6574\uff09\r\n    \/\/ \u66f4\u7a33\u59a5\u7684\u505a\u6cd5\u662f\u7528 std::atomic<std::pair<Node*, uint64_t>> \u4f46\u4e0d\u4fdd\u8bc1\u539f\u5b50\r\n    \/\/ \u5de5\u4e1a\u5b9e\u73b0\u901a\u5e38\u7528 128 \u4f4d CAS\uff08cmpxchg16b\uff09\u6216 tagged pointer\r\n    struct TaggedPtr {\r\n        Node* ptr;\r\n        uint64_t tag;\r\n    };\r\n\r\n    std::atomic<Node*> head_;\r\n    std::atomic<Node*> tail_;\r\n\r\npublic:\r\n    MichaelScottQueue() {\r\n        Node* dummy = new Node();\r\n        head_.store(dummy, std::memory_order_relaxed);\r\n        tail_.store(dummy, std::memory_order_relaxed);\r\n    }\r\n\r\n    ~MichaelScottQueue() {\r\n        \/\/ \u6e05\u7406\u6240\u6709\u8282\u70b9\r\n        Node* cur = head_.load(std::memory_order_relaxed);\r\n        while (cur) {\r\n            Node* next = cur->next.load(std::memory_order_relaxed);\r\n            delete cur;\r\n            cur = next;\r\n        }\r\n    }\r\n\r\n    void enqueue(T value) {\r\n        Node* node = new Node(std::move(value));\r\n        Node* tail;\r\n        while (true) {\r\n            tail = tail_.load(std::memory_order_acquire);\r\n            Node* next = tail->next.load(std::memory_order_acquire);\r\n            \/\/ \u786e\u8ba4 tail \u6ca1\u88ab\u5176\u4ed6\u7ebf\u7a0b\u4fee\u6539\r\n            if (tail != tail_.load(std::memory_order_acquire))\r\n                continue;\r\n\r\n            if (next == nullptr) {\r\n                \/\/ \u5c1d\u8bd5\u628a\u65b0\u8282\u70b9\u94fe\u63a5\u5230 tail \u540e\u9762\r\n                if (tail->next.compare_exchange_weak(\r\n                        next, node,\r\n                        std::memory_order_release,\r\n                        std::memory_order_relaxed)) {\r\n                    \/\/ \u5c1d\u8bd5\u63a8\u8fdb tail\uff0c\u5931\u8d25\u4e5f\u6ca1\u5173\u7cfb\uff08\u5176\u4ed6\u7ebf\u7a0b\u6216\u4e0b\u6b21\u4f1a\u63a8\u8fdb\uff09\r\n                    tail_.compare_exchange_strong(\r\n                        tail, node,\r\n                        std::memory_order_release,\r\n                        std::memory_order_relaxed);\r\n                    return;\r\n                }\r\n            } else {\r\n                \/\/ tail \u6ede\u540e\u4e86\uff0c\u5e2e\u5176\u4ed6\u7ebf\u7a0b\u63a8\u8fdb\r\n                tail_.compare_exchange_strong(\r\n                    tail, next,\r\n                    std::memory_order_release,\r\n                    std::memory_order_relaxed);\r\n            }\r\n        }\r\n    }\r\n\r\n    bool dequeue(T& out) {\r\n        Node* head;\r\n        while (true) {\r\n            head = head_.load(std::memory_order_acquire);\r\n            Node* tail = tail_.load(std::memory_order_acquire);\r\n            Node* next = head->next.load(std::memory_order_acquire);\r\n\r\n            if (head != head_.load(std::memory_order_acquire))\r\n                continue;\r\n\r\n            if (head == tail) {\r\n                if (next == nullptr)\r\n                    return false;  \/\/ \u7a7a\u961f\u5217\r\n                \/\/ tail \u6ede\u540e\uff0c\u5e2e\u63a8\u8fdb\r\n                tail_.compare_exchange_strong(\r\n                    tail, next,\r\n                    std::memory_order_release,\r\n                    std::memory_order_relaxed);\r\n            } else {\r\n                out = std::move(next->value);\r\n                \/\/ \u63a8\u8fdb head\uff0c\u65e7 head \u53d8\u6210\u65b0\u7684 dummy\r\n                if (head_.compare_exchange_weak(\r\n                        head, next,\r\n                        std::memory_order_release,\r\n                        std::memory_order_relaxed)) {\r\n                    \/\/ \u26a0\ufe0f \u8fd9\u91cc\u4e0d\u80fd\u76f4\u63a5 delete head\uff01\r\n                    \/\/ \u5176\u4ed6\u7ebf\u7a0b\u53ef\u80fd\u8fd8\u5728\u8bfb\u8fd9\u4e2a\u8282\u70b9\uff08\u901a\u8fc7\u65e7\u7684 head \u6307\u9488\uff09\r\n                    \/\/ \u9700\u8981 Hazard Pointer \/ Epoch \/ RCU \u7b49\u5b89\u5168\u56de\u6536\u673a\u5236\r\n                    \/\/ delete head;  \/\/ \u5371\u9669\uff01\r\n                    return true;\r\n                }\r\n            }\r\n        }\r\n    }\r\n};<\/pre>\n
         <\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n
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        <\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n
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        \u56db\u3001\u5185\u5b58\u5b89\u5168\u56de\u6536\uff08\u9762\u8bd5\u5fc5\u95ee\uff09<\/h2>\n<\/div>\n
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        \u4e0a\u9762\u4ee3\u7801\u4e2d delete head<\/code> \u88ab\u6ce8\u91ca\u6389\u4e86\uff0c\u8fd9\u662f\u65e0\u9501\u6570\u636e\u7ed3\u6784\u6700\u6838\u5fc3\u7684\u96be\u70b9<\/strong>\u3002<\/div>\n<\/div>\n
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        \u95ee\u9898<\/h3>\n<\/div>\n
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        \u7ebf\u7a0b A \u51fa\u961f\uff0cCAS \u6210\u529f\u628a head \u4ece\u8282\u70b9 X \u79fb\u5230 X->next\uff0c\u51c6\u5907 delete X\u3002\u4f46\u6b64\u65f6\u7ebf\u7a0b B \u53ef\u80fd\u521a\u8bfb\u5230\u65e7\u7684 head = X\uff0c\u6b63\u5728\u8bbf\u95ee X->next\u3002\u5982\u679c A \u5148 delete \u4e86 X\uff0cB \u5c31\u8bbf\u95ee\u4e86\u5df2\u91ca\u653e\u5185\u5b58\uff08UAF\uff09\u3002<\/div>\n<\/div>\n
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        \u4e09\u79cd\u4e3b\u6d41\u65b9\u6848<\/h3>\n<\/div>\n
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        \u8868\u683c<\/div>\n
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        \n\n\n\n\n\n\n\n
        \u65b9\u6848<\/th>\n\u539f\u7406<\/th>\n\u4ee3\u8868\u5b9e\u73b0<\/th>\n\u4f18\u7f3a\u70b9<\/th>\n<\/tr>\n<\/thead>\n
        Hazard Pointer<\/strong><\/td>\n\u7ebf\u7a0b\u58f0\u660e “\u6211\u6b63\u5728\u8bbf\u95ee X”\uff0c\u56de\u6536\u8005\u68c0\u67e5\u6240\u6709 hazard pointer \u540e\u624d\u91ca\u653e<\/td>\nFolly hazptr<\/code>\u3001libcds<\/td>\n\u5b89\u5168\u4f46\u626b\u63cf\u5f00\u9500\u5927<\/td>\n<\/tr>\n
        Epoch-based Reclamation (EBR)<\/strong><\/td>\n\u5206\u4e09\u4e2a epoch\uff0c\u5f53\u524d epoch \u8fdb\u5165\u7684\u7ebf\u7a0b\u90fd\u9000\u51fa\u540e\u624d\u56de\u6536\u4e0a\u4e0a\u4e2a epoch \u7684\u5783\u573e<\/td>\nLinux RCU\u3001Crossbeam<\/td>\n\u6027\u80fd\u597d\uff0c\u4f46\u56de\u6536\u5ef6\u8fdf<\/td>\n<\/tr>\n
        \u4e50\u89c2\u9501 + \u5ef6\u8fdf\u56de\u6536<\/strong><\/td>\n\u7528 tagged pointer \u907f\u514d ABA\uff0c\u8282\u70b9\u653e\u5165\u5ef6\u8fdf\u91ca\u653e\u961f\u5217\uff0c\u5b9a\u671f\u6279\u91cf\u56de\u6536<\/td>\nBoost lockfree<\/td>\n\u5b9e\u73b0\u7b80\u5355\uff0c\u5185\u5b58\u5360\u7528\u9ad8<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n
        \n
        \u7b80\u5316\u7248\u9762\u8bd5\u7b54\u6848<\/strong>\uff1a\u53ef\u4ee5\u8bf4 ” \u751f\u4ea7\u73af\u5883\u4e2d\u901a\u5e38\u7528 Hazard Pointer \u6216 Epoch-based \u56de\u6536\uff0c\u9762\u8bd5 demo \u4e2d\u53ef\u4ee5\u7528 std::atomic<Node*><\/code> + \u7248\u672c\u53f7\u6253\u5305\u907f\u514d ABA\uff0c\u8282\u70b9\u7528 GC \u6216\u5ef6\u8fdf\u56de\u6536 “\u3002<\/div>\n<\/div>\n
        \n
        \n
        \u4e94\u3001SPSC \u65e0\u9501\u73af\u5f62\u7f13\u51b2\u533a\uff08\u66f4\u7b80\u5355\u3001\u66f4\u9ad8\u6027\u80fd\uff09<\/h2>\n<\/div>\n
        \n
        \u5982\u679c\u662f\u5355\u751f\u4ea7\u8005\u5355\u6d88\u8d39\u8005<\/strong>\u573a\u666f\uff0c\u73af\u5f62\u7f13\u51b2\u533a\u662f\u6700\u4f18\u89e3\uff0c\u4e0d\u9700\u8981 CAS \u5faa\u73af\uff0c\u6027\u80fd\u8fdc\u8d85 Michael-Scott\u3002<\/div>\n<\/div>\n
        \n
        \n
        \n
        \n
        \n
        \n
        cpp<\/div>\n
        <\/div>\n<\/div>\n
        \n
        \u8fd0\u884c<\/div>\n
        <\/div>\n
        \n
        template <typename T, size_t N>\r\nclass SPSCQueue {\r\nprivate:\r\n    \/\/ \u7f13\u5b58\u884c\u5bf9\u9f50\uff0c\u907f\u514d false sharing\r\n    alignas(64) std::atomic<size_t> head_{0};  \/\/ \u6d88\u8d39\u8005\u5199\uff0c\u751f\u4ea7\u8005\u8bfb\r\n    alignas(64) std::atomic<size_t> tail_{0};  \/\/ \u751f\u4ea7\u8005\u5199\uff0c\u6d88\u8d39\u8005\u8bfb\r\n    T buffer_[N];\r\n\r\npublic:\r\n    bool enqueue(T value) {\r\n        size_t tail = tail_.load(std::memory_order_relaxed);\r\n        size_t next = (tail + 1) % N;\r\n        \/\/ \u751f\u4ea7\u8005\u53ea\u9700\u8981\u770b head \u7684\u6700\u65b0\u503c\uff08acquire \u4fdd\u8bc1\u770b\u5230\u6d88\u8d39\u8005\u4e4b\u524d\u7684\u5199\uff09\r\n        if (next == head_.load(std::memory_order_acquire))\r\n            return false;  \/\/ \u6ee1\r\n        buffer_[tail] = std::move(value);\r\n        \/\/ release \u4fdd\u8bc1 buffer \u5199\u5165\u5bf9\u6d88\u8d39\u8005\u53ef\u89c1\r\n        tail_.store(next, std::memory_order_release);\r\n        return true;\r\n    }\r\n\r\n    bool dequeue(T& out) {\r\n        size_t head = head_.load(std::memory_order_relaxed);\r\n        if (head == tail_.load(std::memory_order_acquire))\r\n            return false;  \/\/ \u7a7a\r\n        out = std::move(buffer_[head]);\r\n        head_.store((head + 1) % N, std::memory_order_release);\r\n        return true;\r\n    }\r\n};<\/pre>\n
         <\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n
        \n
        <\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n
        \n
        \u5173\u952e\u70b9<\/strong>\uff1a<\/div>\n<\/div>\n
        \n
          \n
        • head<\/code> \u548c tail<\/code> \u5206\u522b\u5728\u4e0d\u540c\u7f13\u5b58\u884c\uff08alignas(64)<\/code>\uff09\uff0c\u907f\u514d\u4f2a\u5171\u4eab\uff08False Sharing\uff09<\/strong><\/li>\n
        • \u751f\u4ea7\u8005\u53ea\u5199 tail<\/code>\u3001\u8bfb head<\/code>\uff1b\u6d88\u8d39\u8005\u53ea\u5199 head<\/code>\u3001\u8bfb tail<\/code>\u2014\u2014 \u6ca1\u6709\u7ade\u4e89\uff0c\u4e0d\u9700\u8981 CAS<\/li>\n
        • \u5185\u5b58\u5e8f\uff1a\u5199\u6570\u636e\u7528 release<\/code>\uff0c\u8bfb\u5bf9\u65b9\u6307\u9488\u7528 acquire<\/code><\/li>\n<\/ul>\n<\/div>\n
          \n
          \n
          \u516d\u3001\u9762\u8bd5\u9ad8\u9891\u8ffd\u95ee<\/h2>\n<\/div>\n
          \n
          Q1: CAS \u5931\u8d25\u91cd\u8bd5\u4f1a\u4e0d\u4f1a\u5bfc\u81f4\u6d3b\u9501\uff08Livelock\uff09\uff1f<\/h3>\n<\/div>\n
          \n
          Michael-Scott \u961f\u5217\u662f lock-free<\/strong> \u4f46\u4e0d\u662f wait-free<\/strong>\u3002\u6781\u7aef\u60c5\u51b5\u4e0b\u591a\u4e2a\u7ebf\u7a0b\u53cd\u590d CAS \u5931\u8d25\u53ef\u80fd\u77ed\u6682\u6d3b\u9501\uff0c\u4f46\u6709\u8f85\u52a9\u63a8\u8fdb\u673a\u5236<\/strong>\uff08\u5e2e\u5176\u4ed6\u7ebf\u7a0b\u63a8\u8fdb tail\uff09\u4fdd\u8bc1\u7cfb\u7edf\u6574\u4f53\u63a8\u8fdb\uff0c\u5b9e\u9645\u4e0d\u4f1a\u6c38\u4e45\u6d3b\u9501\u3002<\/div>\n<\/div>\n
          \n
          Q2: \u4e3a\u4ec0\u4e48\u7528 dummy node\uff1f<\/h3>\n<\/div>\n
          \n
          \u7a7a\u961f\u5217\u65f6 head == tail == dummy\u3002\u5982\u679c\u4e0d\u7528 dummy\uff0c\u5165\u961f\u7b2c\u4e00\u4e2a\u8282\u70b9\u65f6\u9700\u8981\u540c\u65f6\u4fee\u6539 head \u548c tail\uff0c\u4e24\u4e2a\u539f\u5b50\u64cd\u4f5c\u65e0\u6cd5\u539f\u5b50\u5730\u5b8c\u6210\uff0c\u4f1a\u4ea7\u751f\u7ade\u6001\u3002dummy node \u8ba9\u5165\u961f\u6c38\u8fdc\u53ea\u6539 tail->next \u548c tail\uff0c\u51fa\u961f\u6c38\u8fdc\u53ea\u6539 head\uff0c\u804c\u8d23\u5206\u79bb\u3002<\/div>\n<\/div>\n
          \n
          Q3: \u65e0\u9501\u961f\u5217\u4e00\u5b9a\u6bd4\u6709\u9501\u5feb\u5417\uff1f<\/h3>\n<\/div>\n
          \n
          \u4e0d\u4e00\u5b9a<\/strong>\u3002<\/div>\n<\/div>\n
          \n
            \n
          • \u4f4e\u7ade\u4e89\u573a\u666f\uff1a\u6709\u9501\u961f\u5217\uff08std::mutex<\/code> + std::queue<\/code>\uff09\u56e0\u4e3a\u4e0d\u9700\u8981 CAS \u91cd\u8bd5\u548c\u5185\u5b58\u5c4f\u969c\uff0c\u53ef\u80fd\u66f4\u5feb<\/li>\n
          • \u9ad8\u7ade\u4e89\u573a\u666f\uff1a\u65e0\u9501\u961f\u5217\u4f18\u52bf\u660e\u663e\uff0c\u56e0\u4e3a\u4e0d\u4f1a\u963b\u585e\u7ebf\u7a0b<\/li>\n
          • \u5185\u5b58\u56de\u6536\u5f00\u9500\u53ef\u80fd\u62b5\u6d88\u65e0\u9501\u6536\u76ca<\/li>\n
          • \u9762\u8bd5\u6807\u51c6\u7b54\u6848\uff1a\u53d6\u51b3\u4e8e\u573a\u666f\uff0cSPSC \u73af\u5f62\u7f13\u51b2\u533a > \u6709\u9501 > MPMC \u65e0\u9501\u94fe\u8868<\/strong>\uff08\u5927\u81f4\uff09<\/li>\n<\/ul>\n<\/div>\n
            \n
            Q4: \u5982\u4f55\u5b9e\u73b0\u6709\u754c\u65e0\u9501\u961f\u5217\uff1f<\/h3>\n<\/div>\n
            \n
              \n
            • \u65b9\u6848 1\uff1a\u73af\u5f62\u7f13\u51b2\u533a + \u539f\u5b50\u7d22\u5f15\uff08SPSC \u7b80\u5355\uff0cMPMC \u9700\u8981 CAS\uff09<\/li>\n
            • \u65b9\u6848 2\uff1a\u94fe\u8868 + \u539f\u5b50\u8ba1\u6570\u5668\uff08enqueue \u524d CAS \u9012\u589e\u8ba1\u6570\uff0c\u6ee1\u5219\u62d2\u7edd\uff09<\/li>\n<\/ul>\n<\/div>\n
              \n
              Q5: C++ \u4e2d compare_exchange_weak<\/code> \u548c strong<\/code> \u7684\u533a\u522b\uff1f<\/h3>\n<\/div>\n
              \n
                \n
              • weak<\/code> \u53ef\u80fd\u4f2a\u5931\u8d25<\/strong>\uff08spurious failure\uff09\uff1a\u503c\u76f8\u7b49\u4e5f\u8fd4\u56de false\uff0c\u56e0\u4e3a\u5e73\u53f0\u5e95\u5c42\u662f LL\/SC\uff08Load-Linked\/Store-Conditional\uff09\uff0c\u6027\u80fd\u7565\u597d<\/li>\n
              • strong<\/code> \u4fdd\u8bc1\u4e0d\u4f2a\u5931\u8d25<\/li>\n
              • \u5faa\u73af\u4e2d\u7528 weak<\/strong>\uff08\u53cd\u6b63\u8981\u91cd\u8bd5\uff09\uff0c\u5355\u6b21\u5224\u65ad\u7528 strong<\/strong><\/li>\n<\/ul>\n<\/div>\n
                \n
                \n
                \u4e03\u3001\u603b\u7ed3\uff1a\u9762\u8bd5\u56de\u7b54\u6846\u67b6<\/h2>\n<\/div>\n
                \n
                \u88ab\u95ee\u5230 “\u8bb2\u8bb2\u65e0\u9501\u961f\u5217” \u65f6\uff0c\u6309\u8fd9\u4e2a\u7ed3\u6784\u7b54\uff1a<\/div>\n<\/div>\n
                \n
                  \n
                1. \u4e00\u53e5\u8bdd\u5b9a\u4e49<\/strong>\uff1a\u7528 CAS \u7b49\u539f\u5b50\u64cd\u4f5c\u66ff\u4ee3\u4e92\u65a5\u9501\u7684\u5e76\u53d1\u961f\u5217\uff0c\u4fdd\u8bc1\u7cfb\u7edf\u7ea7\u63a8\u8fdb<\/li>\n
                2. \u6838\u5fc3\u539f\u8bed<\/strong>\uff1aCAS + \u5185\u5b58\u5e8f\uff08acquire\/release \u914d\u5bf9\uff09<\/li>\n
                3. \u7ecf\u5178\u7b97\u6cd5<\/strong>\uff1aMichael-Scott \u94fe\u8868\u961f\u5217\uff0c\u8bb2\u5165\u961f \/ \u51fa\u961f\u6d41\u7a0b + dummy node \u4f5c\u7528<\/li>\n
                4. \u4e24\u5927\u96be\u9898<\/strong>\uff1aABA\uff08tagged pointer\uff09+ \u5b89\u5168\u5185\u5b58\u56de\u6536\uff08Hazard Pointer \/ Epoch\uff09<\/li>\n
                5. \u6027\u80fd\u4f18\u5316<\/strong>\uff1aSPSC \u73af\u5f62\u7f13\u51b2\u533a\u3001\u7f13\u5b58\u884c\u5bf9\u9f50\u907f\u514d\u4f2a\u5171\u4eab<\/li>\n
                6. \u9002\u7528\u573a\u666f<\/strong>\uff1a\u9ad8\u5e76\u53d1\u3001\u4f4e\u5ef6\u8fdf\u3001\u4e0d\u80fd\u963b\u585e\u7684\u573a\u666f\uff08\u7f51\u7edc\u5305\u5904\u7406\u3001\u4efb\u52a1\u8c03\u5ea6\u3001\u4e2d\u65ad\u4e0a\u4e0b\u6587\uff09<\/li>\n<\/ol>\n<\/div>\n
                  \n
                  \u8fd9\u4e2a\u56de\u7b54\u8986\u76d6\u4e86\u539f\u7406\u3001\u5b9e\u73b0\u3001\u5751\u70b9\u3001\u6027\u80fd\uff0c\u9762\u8bd5\u8db3\u591f\u6df1\u5165\u3002\u9700\u8981\u6211\u9488\u5bf9\u67d0\u4e2a\u70b9\uff08\u6bd4\u5982 Hazard Pointer \u5177\u4f53\u5b9e\u73b0\u3001128 \u4f4d CAS\u3001\u6216\u8005 Go\/Java \u4e2d\u7684\u65e0\u9501\u961f\u5217\uff09\u518d\u5c55\u5f00\u5417\uff1f<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"
                  \u65e0\u9501\u961f\u5217\u662f\u5e76\u53d1\u7f16\u7a0b\u4e2d\u7684\u9ad8\u9891\u9762\u8bd5\u9898\uff0c\u5c24\u5176\u5728<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"colormag_page_container_layout":"default_layout","colormag_page_sidebar_layout":"default_layout","footnotes":""},"categories":[24],"tags":[],"class_list":["post-7667","post","type-post","status-publish","format-standard","hentry","category-value_docs"],"_links":{"self":[{"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/posts\/7667","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/comments?post=7667"}],"version-history":[{"count":2,"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/posts\/7667\/revisions"}],"predecessor-version":[{"id":7669,"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/posts\/7667\/revisions\/7669"}],"wp:attachment":[{"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/media?parent=7667"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/categories?post=7667"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/i007.cc\/wordpress\/wp-json\/wp\/v2\/tags?post=7667"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}