{"id":776,"date":"2022-02-10T18:09:11","date_gmt":"2022-02-10T10:09:11","guid":{"rendered":"https:\/\/swordofmorning.com\/?p=776"},"modified":"2025-10-09T13:55:35","modified_gmt":"2025-10-09T05:55:35","slug":"concurrent-programming-03","status":"publish","type":"post","link":"https:\/\/swordofmorning.com\/index.php\/2022\/02\/10\/concurrent-programming-03\/","title":{"rendered":"\u5e76\u53d1\u7f16\u7a0b 03 \u5728\u7ebf\u7a0b\u95f4\u5171\u4eab\u6570\u636e"},"content":{"rendered":"

<\/div><\/p>\n

  \u5728\u4f7f\u7528\u591a\u7ebf\u7a0b\u7f16\u7a0b\u7684\u65f6\u5019\uff0c\u6211\u4eec\u9700\u8981\u6ce8\u610f\u7ebf\u7a0b\u4e4b\u95f4\u5171\u4eab\u6570\u636e\u7684\u95ee\u9898\uff0c\u8fd9\u79cd\u95ee\u9898\u57fa\u672c\u4e0a\u662f\u5bf9\u7edf\u4e00\u6570\u636e\u540c\u65f6\u8bfb\u5199\u9020\u6210\u7684\uff0c\u8be6\u7ec6\u60c5\u51b5\u53ef\u4ee5\u53c2\u8003\u8ba1\u7b97\u673a\u64cd\u4f5c\u7cfb\u7edf<\/strong>\uff0c\u8fd9\u91cc\u4e0d\u591a\u8d58\u8ff0\u3002\u4e3a\u4e86\u907f\u514d\u8fd9\u79cd\u60c5\u51b5\uff0c\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528\u51e0\u79cd\u65b9\u6cd5\u6765\u89e3\u51b3\uff0c\u4e00\u662f\u7ed9\u6570\u636e\u4e0a\u9501<\/strong>\uff08\u4e92\u65a5\u5143\uff0cmutex\uff09\uff0c\u8fd9\u662f\u672c\u7ae0\u7684\u5185\u5bb9\uff1b\u4e8c\u662f\u65e0\u9501\u7f16\u7a0b<\/strong>\uff08lock-free programming\uff09\uff0c\u8fd9\u5c06\u5728\u540e\u9762\u7684\u7ae0\u8282\u4e2d\u8ba8\u8bba\uff1b\u8fd8\u6709\u4e00\u79cd\u65b9\u5f0f\u662f\u5c06\u5bf9\u6570\u636e\u7ed3\u6784\u7684\u64cd\u4f5c\u66f4\u65b0\u4e3a\u4e00\u4e2a\u4e8b\u52a1<\/strong>\uff08transaction\uff09\u3002<\/p>\n

\u4e00\u3001\u4f7f\u7528\u4e92\u65a5\u5143\u4fdd\u62a4\u5171\u4eab\u6570\u636e<\/h2>\n

  \u8fd9\u91cc\u6211\u4eec\u4e0d\u8fc7\u591a\u4ecb\u7ecdmutex\u7684\u8bbe\u8ba1\u601d\u60f3\uff0c\u6211\u4eec\u4e3b\u8981\u4ecb\u7ecd\u5176\u5728C++\u4e2d\u7684\u4f7f\u7528\u3002<\/p>\n

1.1 \u5728C++\u4e2d\u4f7f\u7528mutex<\/h3>\n

  \u5728C++\u4e2d\uff0c\u901a\u8fc7\u6784\u9020std::mutex\u7684\u5b9e\u4f8b\u521b\u5efa\u4e92\u65a5\u5143\uff0c\u8c03\u7528\u6210\u5458\u51fd\u6570lock()\u6765\u9501\u5b9a\u5b83\uff0c\u8c03\u7528\u6210\u5458\u51fd\u6570unlock()\u6765\u7ed3\u679c\u5b83\u3002\u7136\u800c\uff0c\u76f4\u63a5\u8c03\u7528\u6210\u5458\u51fd\u6570\u662f\u4e0d\u63a8\u8350\u7684\u505a\u6cd5\uff0c\u56e0\u4e3a\u6211\u4eec\u9700\u8981\u5728\u51fd\u6570\u5305\u62ec\u5f02\u5e38\u5728\u5185<\/em>\u7684\u6bcf\u4e2a\u51fa\u53e3\u90fd\u8c03\u7528unlock()\u3002\u4f5c\u4e3a\u66ff\u4ee3\uff0cSTL\u63d0\u4f9b\u6765std::lock_guard\u7c7b\u6a21\u677f\uff0c\u5b9e\u73b0\u4e86\u4e92\u65a5\u5143\u7684RAII\u60ef\u7528\u8bed\u6cd5\uff1b\u5b83\u5728\u6784\u9020\u65f6\u9501\u5b9a\u6240\u7ed9\u7684\u4e92\u65a5\u5143\uff0c\u5728\u6790\u6784\u65f6\u89e3\u9501\u6240\u7ed9\u7684\u4e92\u65a5\u5143\u3002\u4e0b\u9762\u662f\u4e00\u4e2a\u6f14\u793a\uff0cstd::mutex\u548cstd::lock_guard()\u90fd\u58f0\u660e\u4e8e<mutex>\u3002<\/p>\n

#include <list>\n#include <mutex>\n#include <algorithm>\n\nstd::list<int> some_list;\nstd::mutex some_mutex;\n\n\/\/ \u5411\u94fe\u8868\u4e2d\u6dfb\u52a0\u5143\u7d20\nvoid add_to_list(int val)\n{\n    std::lock_guard<std::mutex> guard(some_mutex);\n    some_list.push_back(val);\n}\n\n\/\/ \u67e5\u627e\u5143\u7d20val\u662f\u5426\u5728\u94fe\u8868\u4e2d\nbool list_contains(int val)\n{\n    std::lock_guard<std::mutex> guard(some_mutex);\n\n    return std::find(some_list.begin(), some_list.end(), val) \n        != some_list.end();\n}<\/code><\/pre>\n
  \u5728\u4e0a\u9762\u7684\u4ee3\u7801\u4e2d\uff0c\u6211\u4eec\u4f7f\u7528\u4e86\u4e00\u4e2a\u5168\u5c40mutex\u6765\u5bf9\u5217\u8868\u5b9e\u65bd\u6765\u4fdd\u62a4\u3002\u5728\u901a\u5e38\u7684\u4f7f\u7528\u4e2d\uff0c\u6211\u4eec\u53ef\u4ee5\u5c06\u5b83\u5c01\u88c5\u5230\u4e00\u4e2a\u7c7b\u4e2d\uff0c\u4ee5private\u7684\u5f62\u52bf\u6765\u907f\u514d\u51b2\u7a81\u3002\u4f46\u503c\u5f97\u6ce8\u610f\u7684\u662f\uff0c\u4f20\u9012\u5f15\u7528\u548c\u6307\u9488\u53ef\u80fd\u4f1a\u9020\u6210\u8d8a\u8fc7mutex\u7684\u60c5\u51b5<\/strong>\uff0c\u4e0b\u9762\u6765\u770b\u4e00\u6bb5\u7cdf\u7cd5\u7684\u4ee3\u7801\uff1a<\/p>\n
\/* ===== class : \u6570\u636e\u7c7b ===== *\/\nclass data\n{\nprivate:\n    int m_a;\npublic: \n    void DoSth();\n}\n\n\/* ===== class : \u5c01\u88c5\u6570\u636e\u7c7b ===== *\/\nclass data_wrapper\n{\nprivate:\n    data m_data;\n    std::mutex m_dataMutex;\npublic:\n    template<typename Function>\n    void ProcessData(Function func)\n    {\n        \/\/ \u4f20\u9012\u201c\u53d7\u4fdd\u62a4\u201d\u7684\u6570\u636e\u5230func\n        std::lock_guard<std::mutex> guard(m_dataMutex);\n        func(m_data);\n    }\n}\n\ndata* unprotectedData;\n\n\/\/ \u4e00\u4e2a\u6076\u610f\u51fd\u6570\uff0c\u7528\u4e8e\u83b7\u53d6data_wrapper\u4e2d\u7684&m_data\nvoid malicious_func(data& protectedData)\n{\n    unprotectedData = & protectedData;\n}\n\ndata_warpper dw;\n\nvoid foo()\n{\n    dw.process_data(malicious_func);\n    \/\/ unpData\u5df2\u7ecf\u6216\u5f97\u4e86data\u7684\u5f15\u7528\uff0c\u73b0\u5728\u53ef\u4ee5\u7ed5\u5f00mutex\u76f4\u63a5\u4f7f\u7528doSth\n    unprotectedData->DoSth();\n}<\/code><\/pre>\n
  \u5728\u4e0a\u9762\u7684\u7684\u4ee3\u7801\u4e2d\uff0c\u6211\u4eec\u901a\u8fc7foo\uff0c\u5411data_wrapper\u4f20\u5165\u4e00\u4e2a\u6076\u610f\u51fd\u6570\uff0c\u6216\u5f97\u4e86\u5176m_data\u7684\u5f15\u7528\u3002\u800c\u83b7\u5f97\u4e86data\u7684unprotectedData\u5c31\u53ef\u4ee5\u7ed5\u8fc7mutex\u65e0\u9700\u9501\u5b9a\u4e92\u65a5\u5143\u5373\u53ef\u8c03\u7528DoSth\u3002\u6240\u4ee5\uff0c\u6211\u4eec\u5e94\u5f53\u6ce8\u610f\u4e0d\u8981\u5c06\u53d7\u4fdd\u62a4\u6570\u636e\u7684\u6307\u9488\u548c\u5f15\u7528\u4f20\u9012\u5230\u9501\u7684\u8303\u56f4\u4e4b\u5916\uff0c\u65e0\u8bba\u662f\u4ece\u51fd\u6570\u4e2d\u8fd4\u56de\u5b83\u4eec\u3001\u5c06\u5176\u5b58\u653e\u5728\u5916\u90e8\u53ef\u89c1\u7684\u5185\u5b58\u4e2d\uff0c\u8fd8\u662f\u4f5c\u4e3a\u53c2\u6570\u4f20\u9012\u7ed9\u7528\u6237\u63d0\u4f9b\u7684\u51fd\u6570<\/strong>\u3002<\/p>\n
1.2 \u53d1\u73b0\u63a5\u53e3\u4e2d\u56fa\u6709\u7684\u7ade\u4e89\u6761\u4ef6<\/h3>\n
  \u56de\u5fc6\u4e0b\u6211\u4eec\u7684\u7b2c\u4e00\u6bb5\u4ee3\u7801\uff0c\u6211\u4eec\u5bf9\u4e00\u4e2alist\u6574\u4f53\u6dfb\u52a0\u4e86\u4fdd\u62a4\uff0c\u800c\u4e0d\u662f\u5bf9\u5176\u4e2d\u7684\u6bcf\u4e00\u4e2a\u8282\u70b9\u6dfb\u52a0\u4fdd\u62a4\u3002\u5982\u679c\u662f\u540e\u8005\u7684\u8bdd\uff0c\u6211\u4eec\u5728\u5220\u9664\u8282\u70b9\u7684\u65f6\u5019\u4ecd\u7136\u53ef\u80fd\u9762\u5bf9\u7ade\u4e89\u95ee\u9898\u3002\u4e0b\u9762\u6211\u4eec\u6765\u770b\u53e6\u4e00\u4e2a\u4f8b\u5b50\uff1a\u8003\u8651\u5728\u591a\u7ebf\u7a0b\u4e2d\u4f7f\u7528std::stack\u3002\u4e0b\u9762\u662fstd::stack\u7684\u63a5\u53e3\uff08\u4e0d\u5305\u542b\u6784\u9020\u51fd\u6570\uff09\u3002<\/p>\n
bool empty() const;\nsize_t size() const;\nT& top();\nT const& top() const;\nvoid push(T const&);\nvoid push(T&&);\nvoid pop();\nvoid swap(stack&&);<\/code><\/pre>\n
  \u6211\u4eec\u53ef\u4ee5\u5c06\u4e0a\u8ff0\u7684top\u4fee\u6539\u4e3a\u975e\u5f15\u7528\u7684\u65b9\u5f0f\uff0c\u8fd9\u6837\u5c31\u9075\u5faa\u6765\u6211\u4eec\u57281.1\u4e2d\u63d0\u51fa\u7684\u51c6\u5219\u3002\u4f46\u662f\u8fd9\u6837\u7684stack\u4ecd\u7136\u662f\u5b58\u5728\u98ce\u9669\u7684\uff0c\u8003\u8651\u4e0b\u9762\u8fd9\u79cd\u60c5\u51b5\uff1a<\/p>\n
std::stack<int> st;\n\nif (!st.empty())                    \/\/ 1\n{\n    int const val = st.top();       \/\/ 2\n    st.pop();                       \/\/ 3\n    doSth(val);\n}<\/code><\/pre>\n
\u5047\u8bbe\u73b0\u5728st\u4e2d\u6709\u4e00\u4e2a\u5143\u7d20\uff0c\u73b0\u5728\u6709\u4e24\u4e2a\u7ebf\u7a0b\u8bbf\u95ee\u5b83\uff0c\u5b83\u4eec\u7684\u987a\u5e8f\u662f\u8fd9\u6837\u7684\uff1a<\/p>\n\n\n\n\n\n\n\n\n\n
\u7ebf\u7a0bA<\/th>\n\u7ebf\u7a0bB<\/th>\n<\/tr>\n<\/thead>\n
if(!st.empty())<\/td>\n<\/td>\n<\/tr>\n
int const val = st.top();<\/td>\nif(!st.empty())<\/td>\n<\/tr>\n
st.pop();<\/td>\nint const val = st.top();<\/td>\n<\/tr>\n
doSth(val);<\/td>\nst.pop()<\/td>\n<\/tr>\n
<\/td>\ndoSth(val);<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
\u6211\u4eec\u53ef\u4ee5\u770b\u5230\uff0c\u5728\u4e0a\u8ff0\u76841\u30012\u30013\u4e4b\u95f4\u53ef\u80fd\u53d1\u751f\u7ade\u4e89\uff0c\u751a\u81f3\u5728\u540e\u9762\u7684doSth()\u672a\u88ab\u8c03\u7528\u5c31\u5df2\u7ecf\u51fa\u6808\uff0c\u4f7f\u5f97val\u6240\u5f15\u7528\u7684\u5bf9\u8c61\u4e3a\u7a7a\u3002\u4e0b\u9762\u6211\u4eec\u6765\u770b\u51e0\u79cd\u89e3\u51b3\u65b9\u6cd5\uff1a<\/p>\n
1.2.1 T1:\u4f20\u5165\u5f15\u7528<\/h4>\n
  \u6211\u4eec\u8003\u8651\u628a\u63a5\u53d7\u51fa\u6808\u503c\u7684\u53d8\u91cf\u7684\u5f15\u7528\uff0c\u4f5c\u4e3a\u53c2\u6570\u4f20\u9012\u7ed9pop()\u8c03\u7528\uff1a<\/p>\n
int result;\nst.pop(result);<\/code><\/pre>\n
\u8fd9\u6837\u7684\u4ee3\u7801\u5728\u5927\u591a\u6570\u65f6\u5019\u90fd\u8bd5\u7528\uff0c\u4f46\u662f\u5982\u679c\u6211\u4eec\u7684stack\u91cc\u9762\u5b58\u653e\u7684\u662f\u4e00\u4e2avector\uff0c\u90a3\u4e48\u6211\u4eec\u5728pop\u4e4b\u524d\u90fd\u5c06\u8981\u4e8b\u5148\u6784\u9020\u4e00\u4e2avector\uff0c\u8fd9\u662f\u4e0d\u63a8\u8350\u7684\u3002\u540c\u65f6\uff0c\u8fd9\u8981\u6c42\u4f20\u5165\u5bf9\u8c61\u662f\u53ef\u8d4b\u503c\u7684\uff08operator=\uff09<\/em>\uff0c\u800c\u4e0d\u4ec5\u4ec5\u662f\u590d\u5236\u6216\u8005\u79fb\u52a8\u6784\u9020\u3002<\/p>\n
1.2.2 T2:\u8981\u6c42\u4e0d\u5f15\u53d1\u5f02\u5e38\u7684\u62f7\u8d1d\u6216\u79fb\u52a8\u6784\u9020\u51fd\u6570<\/h4>\n
  \u63d0\u4f9b\u4e0d\u5f15\u53d1\u5f02\u5e38\u7684\u62f7\u8d1d\u3001\u79fb\u52a8\u6784\u9020\u51fd\u6570\u3002<\/p>\n
1.2.3 T3:\u8fd4\u56de\u6307\u5411\u51fa\u6808\u9876\u7684\u6307\u9488<\/h4>\n
  \u8fd9\u79cd\u65b9\u6cd5\u7684\u4f18\u70b9\u662f\u53ef\u4ee5\u81ea\u7531\u590d\u5236\u5e76\u4e14\u4e0d\u4f1a\u5f15\u53d1\u5f02\u5e38\uff0c\u968f\u4e4b\u800c\u6765\u7684\u56f0\u96be\u5219\u662f\u5185\u5b58\u7ba1\u7406\u3002\u5bf9\u6b64\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528std::shared_ptr\u6765\u89e3\u51b3\u8fd9\u4e00\u95ee\u9898\u3002<\/p>\n
1.2.4 \u5b9e\u73b0\u7ebf\u7a0b\u5b89\u5168\u7684stack<\/h4>\n
  \u6211\u4eec\u901a\u8fc7\u5bf9std::stack\u52a0\u9501\u7684\u65b9\u5f0f\u6765\u5b9e\u73b0\u7ebf\u7a0b\u5b89\u5168\u3002<\/p>\n
#include <exception>\n#include <stack>\n#include <mutex>\n#include <memory>\n#include <thread>\n\n\/\/ \u81ea\u5b9a\u4e49\u5f02\u5e38\nstruct empty_stack : std::exception\n{\n    const char* what() const throw() \n    {\n        std::cout << "empty stack!" << std::endl;\n    }\n};\n\ntemplate<typename T>\nclass ts_stack\n{\nprivate:\n    std::stack<T> m_data;\n\n    \/\/ \u4f7f\u7528mutable\u5141\u8bb8bool empty() const\u4fee\u6539\n    mutable std::mutex m_mutex;\n\npublic:\n    \/\/ \u9ed8\u8ba4\u6784\u9020\u51fd\u6570 do nothing\n    ts_stack() { }\n\n    \/\/ \u62f7\u8d1d\u6784\u9020\n    ts_stack(const ts_stack& other)\n    {\n        std::lock_guard<std::mutex> lock(other.m_mutex);\n        m_data = other.m_data;\n    }\n\n    \/\/ \u7981\u6b62\u8d4b\u503c\n    ts_stack& operator=(const ts_stack&) = delete;\n\n    \/\/ \u5165\u6808\n    void push(T inputVal)\n    {\n        std::lock_guard<std::mutex> lock(this->m_mutex);\n        m_data.push(inputVal);\n    }\n\n    \/\/ \u4ee5ptr\u65b9\u5f0f\u51fa\u6808\n    std::shared_ptr<T> pop()\n    {\n        std::lock_guard<std::mutex> lock(this->m_mutex);\n        if (m_data.empty()) throw empty_stack();\n\n        \/\/ res\u53ea\u80fd\u6307\u5411top()\uff0cconst pointer to res\n        std::shared_ptr<T> const res(std::make_shared<T>(m_data.top()));\n        m_data.pop();\n        return res;\n    }\n\n    \/\/ \u4ee5\u4f20\u503c\u7684\u65b9\u5f0f\u51fa\u6808\n    void pop(T& val)\n    {\n        std::lock_guard<std::mutex> lock(this->m_mutex);\n        if (m_data.empty()) throw empty_stack();\n\n        val = m_data.top();\n        m_data.pop();\n    }\n\n    bool empty() const\n    {\n        std::lock_guard<std::mutex> lock(this->m_mutex);\n        return m_data.empty();\n    }\n};<\/code><\/pre>\n
1.3 \u6b7b\u9501<\/h3>\n
  \u6211\u4eec\u5df2\u7ecf\u4e86\u89e3\u5982\u4f55\u5728\u7ebf\u7a0b\u4e4b\u95f4\u5171\u4eab\u6570\u636e\uff0c\u56e0\u4e3a\u6dfb\u52a0mutex\u6211\u4eec\u9047\u5230\u4e86\u65b0\u7684\u9ebb\u70e6\uff1a\u6b7b\u9501\u3002\u56de\u5fc6\u54f2\u5b66\u5bb6\u5c31\u9910\u95ee\u9898\uff0c\u5982\u679c\u6bcf\u4e2a\u54f2\u5b66\u5bb6\u4eec\u603b\u662f\u5148\u62ff\u5de6\u8fb9\u7684\u7b77\u5b50\uff0c\u518d\u62ff\u53f3\u8fb9\u7684\u7b77\u5b50<\/em>\u90a3\u4e48\u5c31\u6709\u53ef\u80fd\u9020\u6210\u6b7b\u9501\u3002\u4e0b\u9762\u6211\u4eec\u6765\u770b\u4e00\u770b\u5728C++\u4e2d\u5982\u4f55\u5904\u7406\u6b7b\u9501\u76f8\u5173\u7684\u95ee\u9898\u3002STL\u63d0\u4f9bstd::lock\u53ef\u4ee5\u540c\u65f6\u9501\u5b9a\u4e24\u4e2a\u6216\u66f4\u591a\u4e92\u65a5\u5143\uff0c\u4e0b\u9762\u6211\u4eec\u6765\u770b\u4e00\u4e0b\u5b83\u662f\u5982\u4f55\u8fd0\u4f5c\u7684\uff1a<\/p>\n
class data;\nvoid swap(data& lhs, data& rhs);\n\nclass X\n{\nprivate:\n    data m_data;\n    std::mutex m_mutex;\npublic:\n    X(const data& p_data) : m_data(p_data) { }\n\n    friend void swap(X& lhs, X& rhs)\n    {\n        \/\/ \u907f\u514d\u4e24\u4e2a\u53c2\u6570\u5f15\u7528\u540c\u4e00\u5bf9\u8c61\uff0c\u4ece\u800c\u5f15\u53d1\u5f02\u5e38\n        if (&lhs == &rhs)   return;\n\n        \/\/ \u9501\u5b9a\u4e24\u4e2a\u5bf9\u8c61\n        std::lock(lhs.m_mutex, rhs.m_mutex);\n\n        \/\/ \u6784\u9020lock_guard\uff0c\u4f7f\u7528std::adopt_lock\u53c2\u6570\u544a\u77e5\u5176\u5df2\u7ecf\u88ab\u9501\u5b9a\uff0c\u907f\u514d\u5728lg\u6784\u9020\u51fd\u6570\u4e2d\u91cd\u590d\u9501\u5b9a\uff0c\u5e76\u4e14\u8ba9\u9501\u5bf9\u8c61\u6765\u7ba1\u7406\u4e92\u65a5\u5143\n        std::lock_guard<std::mutex> lock_lhs(lhs.m_mutex, std::adopt_lock);\n        std::lock_guard<std::mutex> rock_lhs(rhs.m_mutex, std::adopt_lock);\n\n        swap(lhs.m_data, rhs.m_data);\n    }\n};<\/code><\/pre>\n
\u8fd9\u91cc\u6211\u4eec\u53ea\u9700\u8981\u6ce8\u610f\u4e24\u70b9\uff0c\u4e00\u662f\u5728\u6784\u9020\u591a\u4e2astd::lock_guard\u5bf9\u8c61\u4e4b\u524d\u8c03\u7528lock\u8fdb\u884c\u9501\u5b9a\uff1b\u4e8c\u662f\u6784\u9020lg\u5bf9\u8c61\u65f6\u4f7f\u7528\u53c2\u6570std::adopt_lock\u4f7f\u5176\u6cbf\u7528mutex\u5df2\u6709\u9501\u7684\u6743\u9650\u3002\u503c\u5f97\u4e00\u63d0\u7684\u662f\uff0cstd::lock\u5728\u9501\u5b9alhs.m_mutex\u6216\u8005rhs.m_mutex\u65f6\u90fd\u53ef\u80fd\u5f15\u53d1\u5f02\u5e38\uff0c\u8be5\u5f02\u5e38\u4f20\u64ad\u51fastd::lock\u3002<\/p>\n
1.4 \u907f\u514d\u6b7b\u9501\u7684\u8fdb\u4e00\u6b65\u6307\u5357<\/h3>\n
  \u6b7b\u9501\u5e76\u4e0d\u4e00\u5b9a\u5168\u6765\u81ea\u4e8e\u9501\u5b9a\uff0c\u5728\u4e24\u4e2a\u7ebf\u7a0b\u4e0a\u76f8\u4e92\u8c03\u7528join()\u540c\u6837\u53ef\u4ee5\u5f15\u53d1\u6b7b\u9501\uff0c\u5373\u5faa\u73af\u7b49\u5f85\u3002\u907f\u514d\u6b7b\u9501\u7684\u89c4\u5219\u7b80\u800c\u8a00\u4e4b\u662f\uff0c\u5982\u679c\u4e00\u4e2a\u7ebf\u7a0b\u5728\u7b49\u5f85\u4f60\uff0c\u90a3\u4e48\u4f60\u5c31\u4e0d\u8981\u7b49\u5b83<\/strong>\u3002<\/p>\n
1.4.1 \u907f\u514d\u5d4c\u5957\u9501<\/h4>\n
  \u7b2c\u4e00\u4e2a\u601d\u8def\u662f\uff1a\u5982\u679c\u4f60\u5df2\u7ecf\u6301\u6709\u4e00\u4e2a\u9501\uff0c\u5c31\u522b\u518d\u83b7\u53d6\u9501\u3002\u5982\u679c\u4f60\u575a\u6301\u8fd9\u4e2a\u51c6\u5219\uff0c\u5149\u51ed\u4f7f\u7528\u9501\u662f\u4e0d\u53ef\u80fd\u5bfc\u81f4\u6b7b\u9501\u7684\uff0c\u56e0\u4e3a\u6bcf\u4e2a\u7ebf\u7a0b\u4ec5\u6301\u6709\u4e00\u4e2a\u9501\uff08\u60f3\u60f3\u6bcf\u4e2a\u54f2\u5b66\u5bb6\u53ea\u62ff\u4e00\u6839\u7b77\u5b50\u5403\u996d\uff09\u3002\u5982\u679c\u8981\u83b7\u53d6\u591a\u4e2a\u9501\uff0c\u5e94\u8be5\u4ee5std::lock\u7684\u5355\u4e2a\u52a8\u4f5c\u6765\u5b9e\u73b0\u3002<\/p>\n
1.4.2 \u6301\u6709\u9501\u65f6\uff0c\u907f\u514d\u8c03\u7528\u7528\u6237\u63d0\u4f9b\u7684\u4ee3\u7801<\/h4>\n
  \u4e3e\u4e2a\u4f8b\u5b50\uff0c\u5728\u6211\u4eec\u7684\u591a\u7ebf\u7a0b\u5b89\u5168stack\u4e2d\uff0c\u5728\u53c2\u6570\u7c7b\u578b\u4e0a\u7684\u6bcf\u4e00\u4e2a\u64cd\u4f5c\u90fd\u662f\u7528\u6237\u63d0\u4f9b\u7684\u4ee3\u7801\u3002\u4e3a\u4e86\u907f\u514d\u6b7b\u9501\uff0c\u6211\u4eec\u5e94\u5f53\u907f\u514d\u8fd9\u79cd\u64cd\u4f5c\uff0c\u7136\u800c\u5f53\u64cd\u4f5c\u65e0\u6cd5\u907f\u514d\u65f6\uff0c\u6211\u4eec\u9700\u8981\u65b0\u7684\u51c6\u5219\u3002<\/p>\n
1.4.3 \u4ee5\u56fa\u5b9a\u987a\u5e8f\u83b7\u53d6\u9501<\/h4>\n
  \u8fd9\u662f\u57281.3\u4e2d\u7684\u4f8b\u5b50\uff0c\u5982\u679c\u6211\u4eec\u4e0d\u80fd\u505a\u5230\u4ee5std::lock\u5355\u4e2a\u52a8\u4f5c\u5b9e\u73b0\u9501\u5b9a\uff0c\u90a3\u4e48\u6b21\u4f18\u505a\u6cd5\u662f\u5728\u6bcf\u4e2a\u7ebf\u7a0b\u4e2d\u4ee5\u76f8\u540c\u987a\u5e8f\u83b7\u5f97\u5b83\u4eec\u3002<\/p>\n
1.4.4 \u4f7f\u7528\u9501\u5c42\u6b21<\/h4>\n
  \u9501\u5c42\u6b21\u7684\u601d\u8def\u662f\uff1a\u7ed9mutex\u5206\u7ea7\uff0c\u5f53\u6301\u6709\u9ad8\u7ea7\u9501\u65f6\uff0c\u5141\u8bb8\u6301\u6709\u4f4e\u7ea7\u9501\uff1b\u5f53\u6301\u6709\u4f4e\u7ea7\u9501\u65f6\uff0c\u4e0d\u5141\u8bb8\u6301\u6709\u9ad8\u7ea7\u9501\u3002\u4e0b\u9762\u662f\u4e00\u4e2a\u7b80\u5355\u6f14\u793a\uff1a<\/p>\n
\/\/ \u4e24\u4e2a\u5177\u6709\u4e0d\u540c\u5c42\u6b21\u7b49\u7ea7\u7684\u9501\nHierarchical_Mutex High_Level_Mutex(100);\nHierarchical_Mutex Low_Level_Mutex(50);\n\nint do_low_level_stuff();\nint do_high_level_stuff();\n\nint low_level_func()\n{\n    std::lock_guard<Hierarchical_Mutex> lg(Low_Level_Mutex);\n    return do_low_level_stuff();\n}\n\nint high_level_func()\n{\n    std::lock_guard<Hierarchical_Mutex> lg(High_Level_Mutex);\n    return do_high_level_stuff();\n}\n\n\/\/ OK\uff0c\u5b83\u6301\u6709\u4e86\u9ad8\u7ea7\u9501\u518d\u53bb\u6301\u6709\u4f4e\u7ea7\u9501\nvoid thread_a()\n{\n    high_level_func();\n    low_level_func();\n}\n\n\/\/ Not OK\uff0c\u5b83\u6301\u6709\u4e86\u4f4e\u7ea7\u9501\uff0c\u5c31\u4e0d\u80fd\u6301\u6709\u6bd4\u5b83\u66f4\u9ad8\u7ea7\u7684\u9501\nvoid thread_b()\n{\n    low_level_func();\n    high_level_func();\n}\n<\/code><\/pre>\n
  \u4e0b\u9762\u6211\u4eec\u6765\u770b\u4e00\u4e0b\u5982\u4f55\u5b9e\u73b0Hierarchical_Mutex\uff1a<\/p>\n
class Hierarchical_Mutex\n{\nprivate:\n    std::mutex m_internal_mutex;\n\n    \/\/ \u5177\u4f53\u5bf9\u8c61\u9501\u7684\u5c42\u6b21\u503c\n    unsigned long const m_hierarchy_val;\n\n    \/\/ \u524d\u4e00\u4e2a\u7ebf\u7a0b\u4f7f\u7528\u7684\u5c42\u6b21\u503c\n    unsigned long m_previous_hierarchy_val;\n\n    \/\/ \u5f53\u524d\u7ebf\u7a0b\u6240\u6709\u9501\u7684\u6700\u5c0f\u503c\uff0c\u4ee5\u4fdd\u8bc1\u65b0\u9501\u7b49\u7ea7\u4e0d\u80fd\u8d85\u8fc7\u65e7\u9501\n    \/\/ \u4f7f\u7528thread_local\u5f53\u524d\u7ebf\u7a0b\u7684\u5c42\u6b21\u503c\uff0c\u5728\u7c7b\u5916\u521d\u59cb\u5316\u4e3aULONG_MAX\u4ee5\u4fdd\u8bc1\u7b2c\u4e00\u6b21\u9501\u5b9a\u80fd\u6210\u529f\n    static thread_local unsigned long m_this_thread_hierarchy_val;\n\n    void check_for_hierarchy_violation()\n    {\n        if(m_this_thread_hierarchy_val <= m_hierarchy_val)\n        {\n            throw std::logic_error("mutex hierarchy violated");\n        }\n    }\n\n    \/\/ \u66f4\u65b0\u5f53\u524d\u7ebf\u7a0b\u9501\u7684\u5c42\u6b21\u503c\n    void update_hierarchy_val()\n    {\n        m_previous_hierarchy_val = m_this_thread_hierarchy_val;\n        m_this_thread_hierarchy_val = m_hierarchy_val;\n    }\n\npublic:\n    explicit Hierarchical_Mutex(unsigned long val):\n        m_hierarchy_val(val),\n        m_previous_hierarchy_val(0)\n        { }\n\n    void lock()\n    {\n        check_for_hierarchy_violation();\n        m_internal_mutex.lock();\n        update_hierarchy_val();\n    }\n\n    void unlock()\n    {\n        m_this_thread_hierarchy_val = m_previous_hierarchy_val;\n        m_internal_mutex.unlock();\n    }\n\n    bool try_lock()\n    {\n        check_for_hierarchy_violation();\n        if(!m_internal_mutex.try_lock())    return false;\n\n        update_hierarchy_val();\n        return true;\n    }\n};\n\n\/\/ \u521d\u59cb\u5316m_this_thread_hierarchy_val\nthread_local unsigned long Hierarchical_Mutex::m_this_thread_hierarchy_val(ULONG_MAX);<\/code><\/pre>\n
  \u6211\u4eec\u6765\u4ed4\u7ec6\u770b\u4e00\u4e0b\u5b83\u662f\u5982\u4f55\u8fd0\u4f5c\u7684\uff0c\u4ee5\u4e0a\u9762\u7684\u4ee3\u7801\u4e3a\u4f8b:<\/p>\n
Hierarchical_Mutex High_Level_Mutex(100);\nHierarchical_Mutex Low_Level_Mutex(50);\n\nvoid thread_a()\n{\n    high_level_func();\n    \/*\n        \u7b2c\u4e00\u6b21\u9501\u5b9a\uff0cm_this_thread_hierarchy_val(ULONG_MAX) > m_hierarchy_val(100)\uff0c\u9501\u5b9a\u6210\u529f\uff1b\n        \u66f4\u65b0\uff1am_this_thread_hierarchy_val = 100\n            m_previous_hierarchy_val = ULONG_MAX\n    *\/\n    low_level_func();\n    \/*\n        \u7b2c\u4e8c\u6b21\u9501\u5b9a\uff0cm_this_thread_hierarchy_val(100) > m_hierarchy_val(50)\uff0c\u9501\u5b9a\u6210\u529f\uff1b\n        \u66f4\u65b0\uff1am_this_thread_hierarchy_val = 50\n            m_previous_hierarchy_val = 100\n    *\/\n\n    \/\/ \u89e3\u9501\u65f6\u7531\u4f4e\u5411\u9ad8\uff0c\u7531lock_guard\u81ea\u884c\u5b8c\u6210\n}<\/code><\/pre>\n
1.5 \u4f7f\u7528std::unique_lock\u7075\u6d3b\u9501\u5b9a<\/h3>\n
  \u901a\u8fc7\u677e\u5f1b\u4e0d\u53d8\u91cf\uff0cstd::unique_lock\u6bd4std::lock_guard\u63d0\u4f9b\u4e86\u66f4\u591a\u7684\u7075\u6d3b\u6027\uff0c\u4e00\u4e2astd::unique_lock\u5b9e\u4f8b\u5e76\u4e0d\u603b\u662f\u62e5\u6709\u4e0e\u4e4b\u76f8\u5173\u8054\u7684\u4e92\u65a5\u5143\u3002\u6b63\u5982\u6211\u4eec\u57281.3\u4e2d\u6240\u63d0\u5230\u7684\uff0c\u5bf9std::lock_guard\u6dfb\u52a0\u7b2c\u4e8c\u53c2\u6570std::adopt_lock\u4ee5\u8ba9\u9501\u5bf9\u8c61\u6765\u7ba1\u7406\u4e92\u65a5\u5143\u4e00\u6837\uff0c\u6211\u4eec\u4e5f\u53ef\u4ee5\u628astd::defer_lock\u4f5c\u4e3a\u7b2c\u4e8c\u53c2\u6570\u4f20\u9012\uff0c\u6765\u8868\u793a\u8be5\u4e92\u65a5\u5143\u5728\u6784\u9020\u65f6\u5e94\u4fdd\u6301\u88ab\u9501\u5b9a\u3002\u8fd9\u4e2a\u9501\u5c31\u53ef\u4ee5\u5728\u8fd9\u4e4b\u540e\u901a\u8fc7std::unique_lock\u5bf9\u8c61\uff08\u800c\u4e0d\u662f\u4e92\u65a5\u5143\uff09\u4e0a\u8c03\u7528lock()\uff0c\u6216\u662f\u901a\u8fc7\u5c06std::unique_lock\u5bf9\u8c61\u4f20\u9012\u7ed9std::lock()\u6765\u83b7\u53d6\u3002
\n  \u4e0b\u9762\u6211\u4eec\u4f7f\u7528std::unique_lock\u548cstd::defer_lock\u6765\u66ff\u4ee3std::lock_guard\u548cstd::adopt_lock\uff0c\u4ee3\u7801\u540c1.3\uff0c\u4f5c\u5c11\u8bb8\u53d8\u5316\uff1a<\/p>\n
class data;\nvoid swap(data& lhs, data& rhs);\n\nclass X\n{\nprivate:\n    data m_data;\n    std::mutex m_mutex;\npublic:\n    X(const data& p_data) : m_data(p_data) { }\n\n    friend void swap(X& lhs, X& rhs)\n    {\n        \/\/ \u907f\u514d\u4e24\u4e2a\u53c2\u6570\u5f15\u7528\u540c\u4e00\u5bf9\u8c61\uff0c\u4ece\u800c\u5f15\u53d1\u5f02\u5e38\n        if (&lhs == &rhs)   return;\n\n        \/\/ std::lock(lhs.m_mutex, rhs.m_mutex);\n\n        \/\/ std::lock_guard<std::mutex> lock_lhs(lhs.m_mutex, std::adopt_lock);\n        \/\/ std::lock_guard<std::mutex> rock_lhs(rhs.m_mutex, std::adopt_lock);\n\n        \/\/ std::defer_lock\u4fdd\u7559\u4e92\u65a5\u5143\u4e3a\u672a\u9501\u5b9a\n        std::unique_lock<std::mutex> lock_lhs(lhs.m_mutex, std::defer_lock);\n        std::unique_lock<std::mutex> lock_rhs(rhs.m_mutex, std::defer_lock);\n\n        \/\/ \u6ce8\u610f\uff0c\u8fd9\u91cc\u4f20\u9012std::uinique_lock\uff0cmutex\u5728\u8fd9\u91cc\u88ab\u9501\u5b9a\n        std::lock(lock_lhs, lock_rhs);\n\n        swap(lhs.m_data, rhs.m_data);\n    }\n};<\/code><\/pre>\n
  \u503c\u5f97\u6ce8\u610f\u7684\u662f\uff0c\u5982\u679c\u6211\u4eec\u5728class X\u5df2\u7ecf\u9501\u5b9a\u4e86\u4e92\u65a5\u5143\uff0c\u90a3\u4e48\u6211\u4eec\u5728\u5176\u6790\u6784\u51fd\u6570\u4e2d\u5e94\u8be5\u8c03\u7528unlock\uff0c\u6211\u4eec\u53ef\u4ee5\u901a\u8fc7owns_lock()\u6765\u5224\u522b\uff1a<\/p>\n
void Unlock(std::unique_lock<std::mutex>& lock)\n{\n    REALM_ASSERT(lock.owns_lock());\n    lock.unlock();\n}<\/code><\/pre>\n
  std::unique_lock\u76f8\u6bd4std::lock_guard\u6765\u8bf4\uff0c\u7a7a\u95f4\u65f6\u95f4\u82b1\u8d39\u66f4\u591a\uff0c\u4f46\u662f\u6362\u6765\u4e86\u66f4\u591a\u7684\u7075\u6d3b\u6027\uff0c\u5728\u80fd\u4f7f\u7528lock_guard\u7684\u65f6\u5019\u6709\u9650\u4f7f\u7528lock_guard\u3002\u5982\u679c\u4f60\u8981\u5b9e\u73b0\u5ef6\u8fdf\u9501\u5b9a\uff08\u4e0a\u9762\u7684\u4ee3\u7801\u90a3\u6837\uff09\u3001\u5728\u4f5c\u7528\u57df\u4e4b\u95f4\u8f6c\u79fb\u9501\u7684\u6240\u6709\u6743\uff0c\u8003\u8651\u4f7f\u7528std::unique_lock\u3002<\/p>\n
1.6 \u5728\u4f5c\u7528\u57df\u4e4b\u95f4\u8f6c\u79fb\u9501\u7684\u6240\u6709\u6743<\/h3>\n
  \u56e0\u4e3astd::unique_lock\u5b9e\u4f8b\u5e76\u6ca1\u6709\u62e5\u6709<\/strong>\u4e0e\u5176\u76f8\u5173\u7684\u4e92\u65a5\u5143\uff0c\u6240\u4ee5\u901a\u8fc7moving\uff0c\u4e92\u65a5\u5143\u7684\u6240\u6709\u6743\u53ef\u4ee5\u5728\u5b9e\u4f8b\u4e4b\u95f4\u8fdb\u884c\u8f6c\u79fb\u3002\u5728\u67d0\u4e9b\u60c5\u51b5\u4e0b\uff0c\u8fd9\u4e9b\u8f6c\u79fb\u662f\u81ea\u52a8\u7684\uff0c\u4f8b\u5982\u4ece\u51fd\u6570\u4e2d\u8fd4\u56de\u4e00\u4e2a\u5b9e\u4f8b\uff1b\u800c\u5728\u5176\u4ed6\u60c5\u51b5\u4e0b\uff0c\u5219\u5fc5\u987b\u901a\u8fc7std::move()\u6765\u663e\u793a\u5b9e\u73b0\u3002\u4ece\u6839\u672c\u4e0a\u6765\u8bf4\uff0c\u8fd9\u53d6\u51b3\u4e8e\u6e90\u662f\u5426\u662f\u5de6\u503c\u3002\u5982\u679c\u662f\u5de6\u503c\uff0c\u6240\u6709\u6743\u7684\u8f6c\u79fb\u5fc5\u987b\u662f\u663e\u793a\u7684\uff1b\u5982\u679c\u662f\u53f3\u503c\uff0c\u6240\u6709\u6743\u7684\u8f6c\u79fb\u5219\u662f\u81ea\u52a8\u7684\u3002<\/p>\n
  \u4e00\u79cd\u53ef\u80fd\u7684\u7528\u6cd5\uff0c\u662f\u5141\u8bb8\u51fd\u6570\u9501\u5b9a\u4e00\u4e2a\u4e92\u65a5\u5143\uff0c\u5e76\u5c06\u6b64\u9501\u7684\u6240\u6709\u6743\u8f6c\u79fb\u7ed9\u8c03\u7528\u8005\uff0c\u4e8e\u662f\u8c03\u7528\u8005\u63a5\u4e0b\u6765\u53ef\u4ee5\u5728\u540c\u4e00\u4e2a\u9501\u7684\u4fdd\u62a4\u4e0b\u6267\u884c\u989d\u5916\u7684\u64cd\u4f5c\u3002\u4e0b\u9762\u7684\u4ee3\u7801\u7247\u6bb5\u5c55\u793a\u4e86\u8fd9\u6837\u7684\u4f8b\u5b50\uff1a\u51fd\u6570get_lock()\u9501\u5b9a\u4e86\u4e92\u65a5\u5143\uff0c\u7136\u540e\u5c06\u9501\u8fd4\u56de\u7ed9\u8c03\u7528\u8005\u4e4b\u524d\u51c6\u5907\u7684\u6570\u636e\u3002<\/p>\n
std::unque_lock<std::mutex> get_lock()\n{\n    extern std::mutex some_mutex;\n    std::unique_lock<std::mutex> ul(some_mutex);\n    prepare_data();\n\n    \/\/ ul\u5728\u51fd\u6570\u5185\u90e8\u58f0\u660e\uff0c\u53ef\u4ee5\u76f4\u63a5return\u800c\u65e0\u9700\u8c03\u7528std::move()\n    return ul;\n}\n\nvoid process_data()\n{\n    auto ul(get_lock());\n    do_sth();\n}<\/code><\/pre>\n
1.7 \u9501\u5b9a\u5728\u6070\u5f53\u7684\u7c92\u5ea6<\/h3>\n
  \u9501\u7c92\u5ea6\u662f\u4e00\u4e2a\u6587\u5b57\u672f\u8bed\uff0c\u7528\u6765\u63cf\u8ff0\u5355\u4e2a\u9501\u6240\u4fdd\u62a4\u7684\u6570\u636e\u91cf\u3002\u7ec6\u9897\u7c92\u5ea6\u4fdd\u62a4\u7740\u5c11\u91cf\u7684\u6570\u636e\uff0c\u7c97\u9897\u7c92\u8bfb\u4fdd\u62a4\u7740\u5927\u91cf\u6570\u636e\u3002\u9009\u62e9\u4e00\u4e2a\u5408\u9002\u7684\u9897\u7c92\u5ea6\u6765\u4fdd\u62a4\u6570\u636e\u662f\u5f88\u91cd\u8981\u7684\uff0c\u540c\u6837\u91cd\u8981\u7684\u662f\uff0c\u786e\u4fdd\u53ea\u5728\u771f\u6b63\u9700\u8981\u9501\u7684\u64cd\u4f5c\u4e2d\u6301\u6709\u9501<\/strong>\u3002\u5982\u679c\u53ef\u80fd\uff0c\u4ec5\u5728\u5b9e\u9645\u8bbf\u95ee\u5171\u4eab\u6570\u636e\u7684\u65f6\u5019\u9501\u5b9a\u4e92\u65a5\u5143\uff0c\u5c1d\u8bd5\u5728\u9501\u7684\u5916\u9762\u505a\u4efb\u610f\u7684\u6570\u636e\u5904\u7406\u3002\u7279\u522b\u7684\uff0c\u5728\u6301\u6709\u9501\u65f6\uff0c\u4e0d\u8981\u505a\u4efb\u4f55\u786e\u5b9e\u53ef\u80fd\u7684\u8017\u65f6\u6d3b\u52a8\uff0c\u4f8b\u5982\u6587\u4ef6IO\u3002\u9664\u975e\u771f\u7684\u9700\u8981\u4fdd\u62a4\u6587\u4ef6\uff0c\u5426\u5219\u4e0d\u8981\u6301\u6709\u9501\u3002<\/p>\n
  \u5728\u8fd9\u79cd\u60c5\u51b5\u4e0b\u8fd0\u4f5c\u826f\u597d\uff0c\u56e0\u4e3a\u5b83\u80fd\u5728\u4ee3\u7801\u4e0d\u9700\u8981\u8bbf\u95ee\u5171\u4eab\u6570\u636e\u65f6\u8c03\u7528unlock()\uff0c\u7136\u540e\u5728\u4ee3\u7801\u9700\u8981\u8bbf\u95ee\u5171\u4eab\u6570\u636e\u65f6\u518d\u6b21\u8c03\u7528lock()\u3002<\/p>\n
void get_and_process_data()\n{\n    std::unique_lock<std::mutex> my_lock(the_mutex);\n\n    data data_to_process = get_next_data();\n\n    \/\/ \u52a0\u5de5\u65f6\u4e0d\u9700\u8981\u52a0\u9501\uff0c\u8fd9\u91cc\u89e3\u9501\n    my_lock.unlock();\n\n    result res = process(data_to_process);\n\n    \/\/ \u9501\u5b9a\u4ee5\u786e\u4fdd\u6570\u636e\u4e0d\u4f1a\u53d8\u66f4\n    my_lock.lock();\n\n    write_result(data_to_process, res);\n}<\/code><\/pre>\n
  \u8fd9\u79cd\u9501\u5b9a\u65b9\u5f0f\u7684\u597d\u5904\u662f\u663e\u800c\u6613\u89c1\u7684\uff0c\u5982\u679c\u4f7f\u7528\u4e92\u65a5\u5143\u4fdd\u62a4\u6574\u4e2a\u6570\u636e\u7ed3\u6784\uff0c\u4e0d\u4ec5\u53ef\u80fd\u8ba9\u66f4\u591a\u7684\u9501\u7ade\u4e89\uff0c\u540c\u65f6\u9501\u88ab\u6301\u6709\u7684\u65f6\u95f4\u4e5f\u53ef\u80fd\u5ef6\u957f\u3002\u5982\u4e0a\u6240\u793a\uff0c\u9501\u5b9a\u5728\u6070\u5f53\u7684\u7c92\u5ea6\u4e0d\u4ec5\u5173\u4e4e\u9501\u5b9a\u7684\u6570\u636e\u91cf\uff0c\u8fd9\u4e5f\u662f\u5173\u7cfb\u5230\u9501\u4f1a\u88ab\u6301\u6709\u591a\u957f\u65f6\u95f4\uff0c\u4ee5\u53ca\u5728\u6301\u6709\u9501\u65f6\u6267\u884c\u54ea\u4e9b\u64cd\u4f5c\u3002\u4e00\u822c\u60c5\u51b5\u4e0b\uff0c\u53ea\u5e94\u8be5\u4ee5\u6267\u884c\u8981\u6c42\u7684\u64cd\u4f5c\u6240\u9700\u7684\u6700\u5c0f\u53ef\u80fd\u65f6\u95f4\u53bb\u6301\u6709\u9501<\/strong>\u3002\u8fd9\u4e5f\u610f\u5473\u7740\u8017\u65f6\u7684\u64cd\u4f5c\uff0c\u4f8b\u5982\u83b7\u53d6\u53e6\u5916\u4e00\u4e2a\u9501\u3001\u6587\u4ef6IO\uff0c\u90fd\u4e0d\u5e94\u8be5\u5728\u6301\u6709\u9501\u7684\u65f6\u5019\u53bb\u505a\uff0c\u9664\u975e\u5fc5\u8981\u3002<\/p>\n
  \u5728\u4e4b\u524d\u7684\u4f8b\u5b50\u4e2d\uff0c\u6211\u4eec\u7684swap\u51fd\u6570\u660e\u663e\u9700\u8981\u5e76\u53d1\u8bbf\u95ee\u4e24\u4e2a\u5bf9\u8c61\uff0c\u6240\u4ee5\u6211\u4eec\u9501\u5b9a\u4e86\u4e24\u4e2a\u4e92\u65a5\u91cf\u3002\u4e0b\u9762\u6765\u770b\u53e6\u4e00\u4e2a\u4f8b\u5b50\uff0c\u6211\u4eec\u8003\u8651\u91cd\u8f7doperator==\u4ee5\u8fdb\u884c\u4e24\u4e2a\u5b9e\u4f8b\u4e4b\u95f4\u7684\u6bd4\u8f83\uff1a<\/p>\n
class Y\n{\nprivate:\n    int m_data;\n\n    \/\/ \u4f7f\u7528mutable\u5141\u8bb8int get_data() const\u4fee\u6539\n    mutable std::mutex m_mutex;\n\n    int get_data() const\n    {\n        std::lock_guard<std::mutex> lg(m_mutex);\n        return m_data;\n    }\n\npublic:\n    Y(int data) : m_data(data) { }\n\n    friend bool operator==(Y const& lhs, Y const& rhs)\n    {\n        if (&lhs == &rhs)   return true;\n\n        \/\/ \u5206\u4e24\u6b21\u9501\u5b9a\u4e0d\u540c\u5bf9\u8c61\u7684\u4e92\u65a5\u91cf\n        int const lhs_val = lhs.get_data();\n        int const rhs_val = rhs.get_data();\n\n        return lhs_val == rhs_val;\n    }\n};<\/code><\/pre>\n
  \u53ef\u4ee5\u770b\u5230\uff0c\u6211\u4eec\u5206\u522b\u4f7f\u7528\u4e24\u6b21\u9501\uff0c\u800c\u4e0d\u662f\u4e00\u6b21\u9501\u5b9a\u4e24\u4e2a\u4e92\u65a5\u91cf\uff0c\u8fd9\u6837\u5f53\u7136\u4f1a\u8ba9\u8fd0\u884c\u66f4\u5feb\u3002\u4f46\u968f\u4e4b\u800c\u6765\u7684\u95ee\u9898\u5219\u662f\uff0c\u5728\u4e24\u6b21get_data()\u4e4b\u95f4\u53ef\u80fd\u4f1a\u6709\u64cd\u4f5c\u4f7f\u5f97rhs\u53d1\u751f\u6539\u53d8\uff0c\u4ece\u800c\u4f7f\u5f97\u6211\u4eec\u51fd\u6570\u7684\u8bed\u4e49\u53d1\u751f\u6539\u53d8\uff1a\u4ee5\u524d\u662f\uff0clhs\u548crhs\u5728\u540c\u4e00\u65f6\u95f4\u76f8\u7b49\u5417\uff1b\u73b0\u5728\u662f\uff0c\u67d0\u4e00\u65f6\u95f4\u7684lhs\u548c\u53e6\u4ee5\u65f6\u95f4\u7684rhs\u76f8\u7b49\u5417\u3002<\/p>\n
  \u6709\u65f6\uff0c\u6839\u672c\u6ca1\u6709\u4e00\u4e2a\u5408\u9002\u7684\u9897\u7c92\u7ea7\u522b\uff0c\u5e76\u975e\u6240\u6709\u7684\u5bf9\u6570\u636e\u7ed3\u6784\u7684\u8bbf\u95ee\u90fd\u8981\u8981\u6c42\u540c\u6837\u7ea7\u522b\u7684\u4fdd\u62a4\u3002\u5728\u8fd9\u79cd\u60c5\u51b5\u4e0b\uff0c\u6211\u4eec\u8003\u8651\u4f7f\u7528\u4ee3\u66ff\u673a\u5236\u3002<\/p>\n
\u4e8c\u3001\u7528\u4e8e\u5171\u4eab\u6570\u636e\u4fdd\u62a4\u7684\u66ff\u4ee3\u5de5\u5177<\/h2>\n
  \u867d\u7136\u4e92\u65a5\u5143\u662f\u6700\u901a\u7528\u7684\u673a\u5236\uff0c\u4f46\u662f\u63d0\u5230\u4fdd\u62a4\u5171\u4eab\u6570\u636e\u65f6\uff0c\u5b83\u4eec\u5e76\u4e0d\u662f\u552f\u4e00\u7684\u9009\u62e9\u3002<\/p>\n
  \u4e00\u79cd\u7279\u522b\u6781\u7aef\uff08\u4f46\u76f8\u5f53\u5e38\u89c1\uff09\u7684\u60c5\u51b5\u662f\uff0c\u5171\u4eab\u6570\u636e\u53ea\u6709\u5728\u521d\u59cb\u5316\u65f6\u624d\u9700\u8981\u5e76\u53d1\u8bbf\u95ee\u7684\u4fdd\u62a4\uff0c\u4f46\u5728\u90a3\u4e4b\u540e\u5374\u4e0d\u9700\u8981\u663e\u5f0f\u540c\u6b65\u3002\u8fd9\u53ef\u80fd\u662f\u56e0\u4e3a\u4ece\u4e00\u5f00\u59cb\uff0c\u6570\u636e\u5c31\u662f\u53ea\u8bfb\u7684\uff0c\u6240\u4ee5\u4e0d\u5b58\u5728\u540c\u6b65\u7684\u95ee\u9898\uff1b\u6216\u8005\u662f\u56e0\u4e3a\u5fc5\u8981\u7684\u4fdd\u62a4\u4f5c\u4e3a\u6570\u636e\u4e0a\u64cd\u4f5c\u7684\u4e00\u90e8\u5206\u88ab\u9690\u5f0f\u5730\u6267\u884c\u3002\u5728\u4efb\u4e00\u60c5\u51b5\u4e2d\uff0c\u5728\u6570\u636e\u88ab\u521d\u59cb\u5316\u540e\u9501\u5b9a\u4e92\u65a5\u5143\uff0c\u7eaf\u7cb9\u662f\u4e3a\u4e86\u4fdd\u62a4\u521d\u59cb\u5316\uff0c\u8fd9\u662f\u4e0d\u5fc5\u8981\u7684\uff0c\u5e76\u4e14\u4f1a\u5bf9\u6027\u80fd\u4ea7\u751f\u5f71\u54cd\u3002\u57fa\u4e8e\u8fd9\u4e2a\u539f\u56e0\uff0cSTL\u63d0\u4f9b\u4e86\u4e00\u79cd\u673a\u5236\uff0c\u7eaf\u7cb9\u5728\u521d\u59cb\u5316\u8fc7\u7a0b\u4e2d\u4fdd\u62a4\u5171\u4eab\u6570\u636e\u3002<\/p>\n
2.1 \u5728\u521d\u59cb\u5316\u65f6\u4fdd\u62a4\u5171\u4eab\u6570\u636e<\/h3>\n
  \u5047\u8bbe\u73b0\u5728\u6709\u4e00\u4e2a\u6784\u9020\u8d77\u6765\u975e\u5e38\u6602\u8d35\u7684\u8d44\u6e90\uff08\u4e5f\u8bb8\u662f\u6570\u636e\u5e93\u94fe\u63a5\uff0c\u6216\u8005\u662f\u5206\u914d\u5185\u5b58\uff09\u3002\u50cf\u8fd9\u6837\u7684\u5ef6\u8fdf\u521d\u59cb\u5316\uff08Lazy Initialization\uff09<\/strong>\u5728\u5355\u7ebf\u7a0b\u4ee3\u7801\u4e2d\u662f\u5f88\u5e38\u89c1\u7684\uff1a<\/p>\n
std::shared_ptr<some_resource> resource_ptr;\n\nvoid foo()\n{\n    \/\/ \u5ef6\u8fdf\u521d\u59cb\u5316\n    if (!resource_ptr)  resource_ptr.reset(new some_resource);\n\n    resource_ptr->dosth();\n}<\/code><\/pre>\n
  \u5982\u679c\u5171\u4eab\u8d44\u6e90\u672c\u8eab\u5bf9\u4e8e\u5e76\u53d1\u8bbf\u95ee\u662f\u5b89\u5168\u7684\uff0c\u5f53\u5c06\u5176\u8f6c\u6362\u4e3a\u591a\u7ebf\u7a0b\u4ee3\u7801\u65f6\uff0c\u552f\u4e00\u9700\u8981\u4fdd\u62a4\u7684\u90e8\u5206\u5c31\u662f\u5176\u521d\u59cb\u5316<\/em>\u90e8\u5206\u3002\u4f46\u662f\u50cf\u4e0b\u9762\u4e00\u6bb5\u4ee3\u7801<\/strong>\u4e2d\u7684\u8f6c\u6362\uff0c\u4f1a\u5f15\u8d77\u4f7f\u7528\u8d44\u6e90\u7684\u7a0b\u5e8f\u4ea7\u751f\u4e0d\u5fc5\u8981\u7684\u5e8f\u5217\u5316\u3002\u8fd9\u662f\u56e0\u4e3a\u6bcf\u4e2a\u7ebf\u7a0b\u90fd\u5fc5\u987b\u7b49\u5f85\u4e92\u65a5\u5143\uff0c\u4ee5\u68c0\u67e5\u8d44\u6e90\u662f\u5426\u521d\u59cb\u5316\u3002<\/p>\n
std::shared_ptr<some_resource> resource_ptr;\nstd::mutex resource_mutex;\n\nvoid foo()\n{\n    std::unique_lock<std::mutex> lk(rescoure_mutex);\n\n    if (!resource_ptr)  resource_ptr.reset(new some_resource);\n\n    lk.unlock();\n\n    resource_ptr->dosth();\n}<\/code><\/pre>\n
  C++STL\u63d0\u4f9b\u4e86std::once_flag\u548cstd::call_once\uff0c\u4e0e\u5176\u9501\u5b9a\u4e92\u65a5\u5143\u5e76\u663e\u5f0f\u5730\u68c0\u67e5\u6307\u9488\uff0c\u4e0d\u5982\u6bcf\u4e2a\u7ebf\u7a0b\u90fd\u53ef\u4ee5\u8c03\u7528std::call_once\u3002\u6211\u4eec\u901a\u8fc7\u4e0b\u9762\u7684\u4f8b\u5b50\u6765\u770b\u4e00\u4e0b\uff0c\u901a\u8fc7std::call_once\u6765\u5b9e\u73b0\u540c\u4e0a\u8ff0\u4ee3\u7801\u76f8\u540c\u7684\u529f\u80fd\u3002<\/p>\n
std::shared_ptr<some_resource> resource_ptr;\nstd::once_flag resource_flag;\n\nvoid init_resource()\n{\n    resource_ptr.reset(new some_resource);\n}\n\nvoid foo()\n{\n    \/\/ \u8c03\u7528\u4e00\u6b21\u521d\u59cb\u5316\n    std::call_once(resource_flag, init_resource);\n    resource_ptr->dosth();\n}<\/code><\/pre>\n
  \u4e0b\u9762\u6211\u4eec\u6765\u770b\u4e00\u4e2a\u4f8b\u5b50\uff0c\u6f14\u793a\u5982\u4f55\u4f7f\u7528std::call_once\u5b8c\u6210\u7c7b\u6210\u5458\u7684\u5ef6\u8fdf\u521d\u59cb\u5316\u3002<\/p>\n
class X\n{\nprivate:\n    ConnInfo m_CI;\n    ConnHandle m_CH;\n    std::once_flag m_ConnInit_Flag;\n\n    void openConn()\n    {\n        \/\/ connection\n    }\n\npublic:\n    X(const ConnInfo& a_CI) : m_CI(a_CI) { }\n\n    void Send(const Data& data)\n    {\n        std::call_once(m_ConnInit_Flag, &X::openConn, this);\n        m_CH.send(data);\n    }\n\n    data Receive()\n    {\n        std::call_once(m_ConnInit_Flag, &X::openConn, this);\n        return m_CH.receive();\n    }\n}<\/code><\/pre>\n
  \u5728\u4e0a\u9762\u7684\u4f8b\u5b50\u4e2d\uff0c\u521d\u59cb\u5316\u5728\u9996\u6b21<\/strong>\u8c03\u7528Send()\u6216Receive()\u65f6\u5b8c\u6210\uff0c\u4f7f\u7528\u6210\u5458\u51fd\u6570openConn()\u6765\u5b8c\u6210\u521d\u59cb\u5316\uff0c\u540c\u65f6\u6700\u540e\u9700\u8981\u5c06this\u4f20\u5165\u3002\u503c\u5f97\u6ce8\u610f\u7684\u662f\uff0c\u50cfstd::mutex\u548cstd::once_flag\u8fd9\u79cd\u4e0d\u80fd\u590d\u5236\u6216\u79fb\u52a8\u7684\u5b9e\u4f8b\u6765\u8bf4\uff0c\u5982\u679c\u8981\u4f7f\u7528\u5b83\uff0c\u5c31\u5e94\u8be5\u663e\u5f0f\u5730\u5b9a\u4e49\u3002<\/p>\n
2.2 \u4fdd\u62a4\u5f88\u5c11\u66f4\u65b0\u7684\u6570\u636e\u7ed3\u6784<\/h3>\n
  \u9664\u4e86\u5728\u521d\u59cb\u5316\u540e\u53ea\u8bfb\u7684\u6570\u636e\uff0c\u8fd8\u6709\u4e9b\u5f88\u5c11\u66f4\u65b0\u7684\u6570\u636e\uff0c\u5b83\u4eec\u5728\u5927\u591a\u6570\u60c5\u51b5\u4e0b\u662f\u53ea\u8bfb\u7684\u3002\u4e0b\u9762\u6765\u770b\u4e00\u4e0b\u5982\u4f55\u5bf9\u5b83\u4eec\u8fdb\u884c\u4fdd\u62a4\u3002\u5047\u8bbe\u73b0\u5728\u6211\u4eec\u6709\u4e00\u4e2aDNS\u7f13\u5b58\u8868\uff0c\u6211\u4eec\u5e0c\u671b\u786e\u4fdd\u6240\u6709\u7ebf\u7a0b\u5728\u8bfb\u5199\u65f6\u6b63\u5e38\u8fd0\u884c\u3002\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528std::mutex\u6765\u5b8c\u6210\uff0c\u4f46\u662f\u4f7f\u7528std::mutex\u7684\u4e00\u4e2a\u7f3a\u70b9\u662f\uff0c\u4f1a\u6d88\u9664\u6570\u636e\u7ed3\u6784\u6ca1\u6709\u8fdb\u884c\u4fee\u6539\u65f6\u7684\u5e76\u53d1\u8bfb\u53d6\u6570\u636e\u7684\u53ef\u80fd\u6027\u3002\u6211\u4eec\u53ef\u4ee5\u8003\u8651\u4e00\u79cd\u65b0\u7684\u4e92\u65a5\u5143\uff0creader-writer mutex\uff0c\u5b83\u8003\u8651\u4e86\u4e24\u79cd\u4e0d\u540c\u7684\u7528\u6cd5\uff1a\u7531\u5355\u4e2a\u201c\u5199\u201d\u7ebf\u7a0b\u72ec\u5360\u8bbf\u95ee\u6216\u5171\u4eab\uff1b\u7531\u591a\u4e2a\u201c\u8bfb\u201d\u7ebf\u7a0b\u5e76\u53d1\u8bbf\u95ee\u3002<\/p>\n
  STL\u5e76\u6ca1\u6709\u5b9e\u73b0\u8fd9\u6837\u7684\u4e92\u65a5\u5143\uff0c\u6240\u4ee5\u6211\u4eec\u901a\u8fc7Boost\u5e93\u7684boost::shared_mutex\u6765\u4ee3\u66ffstd::mutex\u3002boost::shared_mutex\u7684\u8bbe\u8ba1\u5f88\u50cfSTL\u5e93\u7684smart ptr\uff1a\u5f53\u4efb\u610f\u4e00\u4e2a\u7ebf\u7a0b\u7531\u4e8e\u5171\u4eab\u9501<\/strong>\u65f6\uff0c\u5176\u4ed6\u8bd5\u56fe\u72ec\u5360<\/strong>\u9501\u7684\u7ebf\u7a0b\u4f1a\u88ab\u963b\u585e\uff0c\u77e5\u9053\u5176\u4ed6\u7ebf\u7a0b\u64a4\u56de\u5b83\u4eec\u7684\u9501\uff1b\u5f53\u4efb\u610f\u4e00\u4e2a\u7ebf\u7a0b\u62e5\u6709\u72ec\u5360\u9501<\/strong>\u65f6\uff0c\u5176\u4ed6\u7ebf\u7a0b\u90fd\u4e0d\u80fd\u62e5\u6709\u72ec\u5360\u9501\u6216\u5171\u4eab\u9501<\/strong>\uff0c\u76f4\u5230\u7b2c\u4e00\u4e2a\u7ebf\u7a0b\u64a4\u9500\u5b83\u7684\u72ec\u5360\u9501\u3002<\/p>\n
  \u4e0b\u9762\u6211\u4eec\u6765\u4ee5DNS\u8868\u7684\u5e76\u53d1\u8bbf\u95ee\u6765\u6f14\u793a\u5982\u4f55\u4f7f\u7528boost::shared_mutex\u3002<\/p>\n
#include <map>\n#include <string>\n#include <mutex>\n#include <boost\/thread\/shared_mutex.hpp>\n\nclass DnsEntry;\n\nclass DnsCache\n{\nprivate:\n    std::map<std::string, DnsEntry> m_Entries;\n\n    mutable boost::shared_mutex m_Mutex;\n\npublic:\n    DnsEntry FindEntry(const std::string& domain) const\n    {\n        \/\/ \u8bfb\u53d6\uff0c\u5171\u4eab\u9501\n        boost::shared_lock<boost::shared_mutex> lk(m_Mutex);\n\n        \/\/ \u67e5\u627e\n        std::map<std::string, DnsEntry>::const_iterator const it = m_Entries.find(domain);\n\n        return it == m_Entries.end() ?\n                DnsEntry() :\n                it-second();\n    }\n\n    void UpdateEntry(const std::string& domain, const DnsEntry& dns)\n    {\n        \/\/ \u5199\u5165\uff0c\u72ec\u5360\u9501\n        std::lock_guard<boost::shared_mutex> lk(m_Mutex);\n\n        m_Entries[domain] = dns;\n    }\n}<\/code><\/pre>\n","protected":false},"excerpt":{"rendered":"
  \u5728\u4f7f\u7528\u591a\u7ebf\u7a0b\u7f16\u7a0b\u7684\u65f6\u5019\uff0c\u6211\u4eec\u9700\u8981\u6ce8\u610f\u7ebf\u7a0b\u4e4b\u95f4\u5171\u4eab\u6570\u636e\u7684\u95ee\u9898\uff0c\u8fd9\u79cd\u95ee\u9898\u57fa\u672c\u4e0a\u662f\u5bf9\u7edf\u4e00\u6570\u636e\u540c\u65f6\u8bfb\u5199\u9020\u6210\u7684\uff0c\u8be6\u7ec6 …<\/p>","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[59],"tags":[],"amp_enabled":true,"_links":{"self":[{"href":"https:\/\/swordofmorning.com\/index.php\/wp-json\/wp\/v2\/posts\/776"}],"collection":[{"href":"https:\/\/swordofmorning.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/swordofmorning.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/swordofmorning.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/swordofmorning.com\/index.php\/wp-json\/wp\/v2\/comments?post=776"}],"version-history":[{"count":1,"href":"https:\/\/swordofmorning.com\/index.php\/wp-json\/wp\/v2\/posts\/776\/revisions"}],"predecessor-version":[{"id":777,"href":"https:\/\/swordofmorning.com\/index.php\/wp-json\/wp\/v2\/posts\/776\/revisions\/777"}],"wp:attachment":[{"href":"https:\/\/swordofmorning.com\/index.php\/wp-json\/wp\/v2\/media?parent=776"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/swordofmorning.com\/index.php\/wp-json\/wp\/v2\/categories?post=776"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/swordofmorning.com\/index.php\/wp-json\/wp\/v2\/tags?post=776"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}