{"id":7564,"date":"2026-08-01T00:29:00","date_gmt":"2026-07-31T16:29:00","guid":{"rendered":"https:\/\/i007.cc\/wordpress\/?p=7564"},"modified":"2026-08-01T00:29:00","modified_gmt":"2026-07-31T16:29:00","slug":"%e8%ae%b2%e8%ae%b2volatile-%e5%92%8c-atomic-%e7%9a%84%e5%8c%ba%e5%88%ab","status":"publish","type":"post","link":"https:\/\/i007.cc\/wordpress\/archives\/7564","title":{"rendered":"\u8bb2\u8bb2volatile \u548c atomic \u7684\u533a\u522b"},"content":{"rendered":"
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\u8fd9\u9053\u9898\u662f NVIDIA \u9762\u8bd5\u91cc\u62c9\u5f00\u5dee\u8ddd\u7684\u9898\u76ee\uff0c\u7b54\u5bf9\u7684\u4eba\u4e0d\u591a\u3002\u5f88\u591a\u4eba\u4ee5\u4e3a\u00a0volatile<\/code>\u00a0\u662f”\u5f31\u5316\u7248\u7684\u00a0atomic<\/code>“\uff0c\u5b9e\u9645\u4e0a\u4e24\u8005\u89e3\u51b3\u7684\u662f\u5b8c\u5168\u4e0d\u540c\u7684\u95ee\u9898\u3002<\/p>\n

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\u4e24\u8005\u5404\u81ea\u89e3\u51b3\u4ec0\u4e48\u95ee\u9898<\/h3>\n

volatile<\/code>\u00a0\u89e3\u51b3\u7684\u95ee\u9898\uff1a\u9632\u6b62\u7f16\u8bd1\u5668\u4f18\u5316\u6389\u5bf9\u67d0\u4e2a\u5185\u5b58\u4f4d\u7f6e\u7684\u8bfb\u5199\u3002<\/strong><\/p>\n

std::atomic<\/code>\u00a0\u89e3\u51b3\u7684\u95ee\u9898\uff1a\u4fdd\u8bc1\u591a\u7ebf\u7a0b\u5e76\u53d1\u8bbf\u95ee\u5171\u4eab\u53d8\u91cf\u65f6\u7684\u6b63\u786e\u6027\u3002<\/strong><\/p>\n

\u8fd9\u4e24\u4ef6\u4e8b\u672c\u8d28\u4e0a\u4e0d\u540c\uff0c\u6df7\u7528\u662f C++ \u5e76\u53d1 bug \u7684\u9ad8\u9891\u6765\u6e90\u3002<\/p>\n

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volatile\uff1a\u53ea\u548c\u7f16\u8bd1\u5668\u8bf4\u8bdd<\/h3>\n

volatile<\/code>\u00a0\u544a\u8bc9\u7f16\u8bd1\u5668\uff1a”\u8fd9\u4e2a\u53d8\u91cf\u7684\u503c\u53ef\u80fd\u88ab\u4f60\u770b\u4e0d\u5230\u7684\u529b\u91cf\u6539\u53d8\uff0c\u6bcf\u6b21\u8bfb\u90fd\u5fc5\u987b\u771f\u6b63\u53bb\u5185\u5b58\u91cc\u53d6\uff0c\u6bcf\u6b21\u5199\u90fd\u5fc5\u987b\u771f\u6b63\u5199\u56de\u5185\u5b58\uff0c\u4e0d\u8981\u4f18\u5316\u3002”<\/p>\n

\u770b\u4e00\u4e2a\u7ecf\u5178\u4f8b\u5b50\uff1a<\/p>\n

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cpp<\/div>\n
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\/\/ \u573a\u666f\uff1a\u8f6e\u8be2\u4e00\u4e2a\u786c\u4ef6\u72b6\u6001\u5bc4\u5b58\u5668\r\nint* status_reg = reinterpret_cast<int*>(0xDEAD0000);  \/\/ \u5185\u5b58\u6620\u5c04 IO\r\n\r\n\/\/ \u4e0d\u52a0 volatile\uff1a\r\nwhile (*status_reg == 0) {}   \/\/ \u7f16\u8bd1\u5668\u770b\u5230\uff1a\u8fd9\u4e2a\u503c\u4ece\u6ca1\u88ab\u4fee\u6539\u8fc7\r\n                              \/\/ \u4f18\u5316\u540e\u53d8\u6210\uff1aif (*status_reg == 0) while(true) {}\r\n                              \/\/ \u53ea\u8bfb\u4e00\u6b21\uff0c\u7136\u540e\u6c38\u8fdc\u5faa\u73af\uff01\r\n\r\n\/\/ \u52a0 volatile\uff1a\r\nvolatile int* status_reg = reinterpret_cast<volatile int*>(0xDEAD0000);\r\nwhile (*status_reg == 0) {}   \/\/ \u7f16\u8bd1\u5668\u8001\u8001\u5b9e\u5b9e\u6bcf\u6b21\u53bb\u5185\u5b58\u8bfb\r\n                              \/\/ \u56e0\u4e3a\u5b83\u77e5\u9053\u8fd9\u4e2a\u5730\u5740\u7684\u503c\u53ef\u80fd\u88ab\u786c\u4ef6\u6539\u53d8<\/pre>\n
 <\/p>\n<\/div>\n<\/div>\n
volatile<\/code>\u00a0\u7684\u6838\u5fc3\u4fdd\u8bc1\uff1a\u5bf9\u8be5\u53d8\u91cf\u7684\u6bcf\u6b21\u8bfb\u5199\u5728\u7f16\u8bd1\u540e\u7684\u6c47\u7f16\u91cc\u90fd\u771f\u5b9e\u5b58\u5728\uff0c\u4e0d\u4f1a\u88ab\u5408\u5e76\u3001\u5220\u9664\u3001\u7f13\u5b58\u5230\u5bc4\u5b58\u5668\u3002<\/strong><\/p>\n
volatile<\/code>\u00a0\u7684\u8fb9\u754c<\/strong>\uff1a\u5b83\u53ea\u548c\u7f16\u8bd1\u5668\u7684\u4f18\u5316\u884c\u4e3a\u6709\u5173\uff0c\u5bf9 CPU \u7684\u4e71\u5e8f\u6267\u884c\u5b8c\u5168\u6ca1\u6709\u7ea6\u675f\u529b\u3002<\/p>\n
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std::atomic\uff1a\u540c\u65f6\u548c\u7f16\u8bd1\u5668\u3001CPU \u8bf4\u8bdd<\/h3>\n
\u591a\u7ebf\u7a0b\u7a0b\u5e8f\u9762\u4e34\u4e24\u5c42\u4e71\u5e8f\uff1a<\/p>\n
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\u6e90\u4ee3\u7801\u987a\u5e8f\r\n    \u2193 \u7f16\u8bd1\u5668\u53ef\u80fd\u91cd\u6392\uff08\u6307\u4ee4\u8c03\u5ea6\u4f18\u5316\uff09\r\n\u6c47\u7f16\u6307\u4ee4\u987a\u5e8f\r\n    \u2193 CPU \u53ef\u80fd\u91cd\u6392\uff08\u4e71\u5e8f\u6267\u884c\u3001Store Buffer\u3001Cache\uff09\r\n\u5b9e\u9645\u6267\u884c\u987a\u5e8f<\/pre>\n
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volatile<\/code>\u00a0\u53ea\u963b\u6b62\u7b2c\u4e00\u5c42\uff0cstd::atomic<\/code>\u00a0\u4e24\u5c42\u90fd\u963b\u6b62\uff0c\u5e76\u4e14\u989d\u5916\u4fdd\u8bc1\u64cd\u4f5c\u7684\u539f\u5b50\u6027<\/strong>\uff08\u4e0d\u53ef\u5206\u5272\uff09\uff1a<\/p>\n
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cpp<\/div>\n
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std::atomic<int> counter{0};\r\n\r\n\/\/ \u7ebf\u7a0b1\r\ncounter.fetch_add(1, std::memory_order_relaxed);\r\n\r\n\/\/ \u8fd9\u4e00\u6761\u6307\u4ee4\u5728\u5e95\u5c42\u5c55\u5f00\u4e3a\uff1a\r\n\/\/ 1. \u8bfb counter \u7684\u5f53\u524d\u503c\r\n\/\/ 2. \u52a0 1\r\n\/\/ 3. \u5199\u56de\r\n\/\/ std::atomic \u4fdd\u8bc1\u8fd9\u4e09\u6b65\u5bf9\u5176\u4ed6\u7ebf\u7a0b\u662f\u4e0d\u53ef\u5206\u5272\u7684\r\n\/\/ \u4e0d\u53ef\u80fd\u6709\u53e6\u4e00\u4e2a\u7ebf\u7a0b\u5728\u6b65\u9aa4 1 \u548c 3 \u4e4b\u95f4\u63d2\u5165\uff0c\u8bfb\u5230\u4e2d\u95f4\u72b6\u6001<\/pre>\n
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\u4e3a\u4ec0\u4e48 volatile \u5728\u591a\u7ebf\u7a0b\u91cc\u6ca1\u6709\u610f\u4e49<\/h3>\n
\u7528\u4e00\u4e2a\u5178\u578b\u7684\u9519\u8bef\u6765\u8bf4\u660e\uff1a<\/p>\n
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cpp<\/div>\n
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volatile bool ready = false;\r\nint data = 0;\r\n\r\n\/\/ \u7ebf\u7a0b1\uff08\u751f\u4ea7\u8005\uff09\r\nvoid producer() {\r\n    data  = 42;        \/\/ \u6b65\u9aa4 A\r\n    ready = true;      \/\/ \u6b65\u9aa4 B\r\n}\r\n\r\n\/\/ \u7ebf\u7a0b2\uff08\u6d88\u8d39\u8005\uff09\r\nvoid consumer() {\r\n    while (!ready) {}  \/\/ \u7b49\u5f85\u6b65\u9aa4 B\r\n    std::cout << data; \/\/ \u671f\u671b\u8bfb\u5230 42\r\n}<\/pre>\n
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\u770b\u8d77\u6765\u5408\u7406\uff0c\u5b9e\u9645\u4e0a\u6709\u4e09\u4e2a\u95ee\u9898\uff1a<\/p>\n
\u95ee\u9898\u4e00\uff1a\u7f16\u8bd1\u5668\u53ef\u4ee5\u628a A \u548c B \u8c03\u6362\u987a\u5e8f\u3002<\/strong><\/p>\n
volatile<\/code>\u00a0\u963b\u6b62\u7f16\u8bd1\u5668\u5bf9\u00a0ready<\/code>\u00a0\u672c\u8eab\u7684\u4f18\u5316\uff0c\u4f46\u4e0d\u963b\u6b62\u5b83\u628a\u00a0data = 42<\/code>\u00a0\u79fb\u5230\u00a0ready = true<\/code>\u00a0\u4e4b\u540e\u2014\u2014\u8fd9\u4e24\u884c\u64cd\u4f5c\u7684\u662f\u4e0d\u540c\u7684\u53d8\u91cf\uff0c\u7f16\u8bd1\u5668\u8ba4\u4e3a\u53ef\u4ee5\u81ea\u7531\u8c03\u5ea6\u3002<\/p>\n
\u95ee\u9898\u4e8c\uff1aCPU \u7684 Store Buffer \u53ef\u80fd\u8ba9 B \u5bf9\u5176\u4ed6\u6838\u53ef\u89c1\uff0c\u4f46 A \u8fd8\u6ca1\u6709\u3002<\/strong><\/p>\n
\u73b0\u4ee3 CPU \u6709\u5199\u7f13\u51b2\u533a\uff0c\u5199\u64cd\u4f5c\u4e0d\u4e00\u5b9a\u7acb\u523b\u5bf9\u5176\u4ed6\u6838\u53ef\u89c1\u3002\u7ebf\u7a0b2 \u53ef\u80fd\u770b\u5230\u00a0ready = true<\/code>\uff0c\u4f46\u00a0data<\/code>\u00a0\u7684\u5199\u5165\u8fd8\u5728\u7ebf\u7a0b1 \u7684 Store Buffer \u91cc\uff0c\u6ca1\u6709\u5237\u5230\u5171\u4eab\u5185\u5b58\u3002<\/p>\n
\u95ee\u9898\u4e09\uff1avolatile<\/code>\u00a0\u672c\u8eab\u4e0d\u4fdd\u8bc1\u539f\u5b50\u6027\u3002<\/strong><\/p>\n
\u5728\u67d0\u4e9b\u67b6\u6784\u4e0a\uff0c64 \u4f4d\u5199\u53ef\u80fd\u88ab\u62c6\u6210\u4e24\u6b21 32 \u4f4d\u5199\u3002\u5982\u679c\u53e6\u4e00\u4e2a\u7ebf\u7a0b\u6070\u597d\u5728\u4e2d\u95f4\u8bfb\uff0c\u4f1a\u8bfb\u5230\u6495\u88c2\u7684\u503c\u3002<\/p>\n
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cpp<\/div>\n
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\/\/ \u6b63\u786e\u5199\u6cd5\uff1a\r\nstd::atomic<bool> ready{false};\r\nint data = 0;\r\n\r\nvoid producer() {\r\n    data = 42;\r\n    \/\/ memory_order_release\uff1a\u4fdd\u8bc1\u6b64\u884c\u4e4b\u524d\u7684\u6240\u6709\u5199\u5165\uff0c\r\n    \/\/ \u5bf9\u770b\u5230 ready=true \u7684\u7ebf\u7a0b\u53ef\u89c1\r\n    ready.store(true, std::memory_order_release);\r\n}\r\n\r\nvoid consumer() {\r\n    \/\/ memory_order_acquire\uff1a\u4fdd\u8bc1\u6b64\u884c\u4e4b\u540e\u7684\u6240\u6709\u8bfb\u53d6\uff0c\r\n    \/\/ \u80fd\u770b\u5230 store(release) \u4e4b\u524d\u7684\u6240\u6709\u5199\u5165\r\n    while (!ready.load(std::memory_order_acquire)) {}\r\n    std::cout << data;  \/\/ \u4fdd\u8bc1\u8bfb\u5230 42\r\n}<\/pre>\n
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\u539f\u5b50\u6027\u7684\u771f\u5b9e\u542b\u4e49<\/h3>\n
volatile<\/code>\u00a0\u7684\u8bfb\u5199\u4e0d\u4fdd\u8bc1\u539f\u5b50\u6027<\/strong>\uff1a<\/p>\n
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cpp<\/div>\n
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volatile long long v = 0;\r\n\r\n\/\/ \u5728 32 \u4f4d\u7cfb\u7edf\u4e0a\uff0c\u8fd9\u4e00\u884c\u53ef\u80fd\u7f16\u8bd1\u4e3a\u4e24\u6761\u6307\u4ee4\uff1a\r\nv = 0x0123456789ABCDEF;\r\n\/\/ mov [v],   0x89ABCDEF   \u2190 \u4f4e 32 \u4f4d\r\n\/\/ mov [v+4], 0x01234567   \u2190 \u9ad8 32 \u4f4d\r\n\/\/ \u53e6\u4e00\u4e2a\u7ebf\u7a0b\u5728\u4e24\u6761\u6307\u4ee4\u4e4b\u95f4\u8bfb\uff0c\u4f1a\u8bfb\u5230\u6495\u88c2\u7684\u503c\r\n\r\nstd::atomic<long long> a{0};\r\na.store(0x0123456789ABCDEF);\r\n\/\/ \u7f16\u8bd1\u4e3a\u5355\u6761\u539f\u5b50\u6307\u4ee4\uff0c\u6216\u8005\u5e26\u9501\u7684\u64cd\u4f5c\uff0c\u4e0d\u53ef\u80fd\u88ab\u4e2d\u95f4\u89c2\u5bdf<\/pre>\n
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\u4ec0\u4e48\u65f6\u5019\u9700\u8981\u540c\u65f6\u7528\u4e24\u8005<\/h3>\n
\u8fd9\u662f\u5c11\u6709\u4eba\u77e5\u9053\u7684\u573a\u666f\uff1a\u5185\u5b58\u6620\u5c04 IO \u7684\u5bc4\u5b58\u5668\u88ab\u591a\u4e2a\u7ebf\u7a0b\u540c\u65f6\u8bbf\u95ee\u3002<\/strong><\/p>\n
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cpp<\/div>\n
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\/\/ \u53ea\u7528 volatile\uff1a\u591a\u7ebf\u7a0b\u8bbf\u95ee\u4e0d\u5b89\u5168\uff08\u65e0\u539f\u5b50\u6027\uff09\r\nvolatile int* hw_reg = (volatile int*)0xDEAD0000;\r\n\r\n\/\/ \u53ea\u7528 atomic\uff1a\u7f16\u8bd1\u5668\u53ef\u80fd\u8ba4\u4e3a\u6ca1\u6709\"\u5916\u90e8\u4fee\u6539\"\u800c\u4f18\u5316\u6389\u67d0\u4e9b\u8bfb\r\nstd::atomic<int>* hw_reg = (std::atomic<int>*)0xDEAD0000;\r\n\r\n\/\/ \u6b63\u786e\u505a\u6cd5\uff1avolatile + atomic\uff08C++20 \u6709 atomic_ref\uff0c\u66f4\u4f18\u96c5\uff09\r\n\/\/ \u6216\u8005\u7528\u5e73\u53f0\u7279\u5b9a\u7684\u5185\u5b58\u5c4f\u969c + volatile\r\nvolatile std::atomic<int>* hw_reg = (volatile std::atomic<int>*)0xDEAD0000;<\/pre>\n
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\u5b9e\u9645\u4e0a\u8fd9\u4e2a\u573a\u666f\u5728\u666e\u901a\u6e38\u620f\u540e\u7aef\u5f00\u53d1\u91cc\u51e0\u4e4e\u9047\u4e0d\u5230\uff0c\u66f4\u591a\u51fa\u73b0\u5728\u9a71\u52a8\u7a0b\u5e8f\u548c\u5d4c\u5165\u5f0f\u7cfb\u7edf\u91cc\u2014\u2014\u5bf9 NVIDIA \u9762\u8bd5\u6765\u8bf4\u662f\u52a0\u5206\u9879\u3002<\/p>\n
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\u4e00\u5f20\u8868\u5bf9\u6bd4<\/h3>\n
\n\n\n\n\n\n\n\n\n\n\n\n
<\/th>\nvolatile<\/code><\/th>\nstd::atomic<\/code><\/th>\n<\/tr>\n<\/thead>\n
\u9632\u6b62\u7f16\u8bd1\u5668\u4f18\u5316\/\u5408\u5e76\u8bfb\u5199<\/td>\n\u2705<\/td>\n\u2705<\/td>\n<\/tr>\n
\u9632\u6b62 CPU \u4e71\u5e8f\u6267\u884c<\/td>\n\u274c<\/td>\n\u2705<\/td>\n<\/tr>\n
\u4fdd\u8bc1\u64cd\u4f5c\u539f\u5b50\u6027<\/td>\n\u274c<\/td>\n\u2705<\/td>\n<\/tr>\n
\u7ebf\u7a0b\u5b89\u5168<\/td>\n\u274c<\/td>\n\u2705<\/td>\n<\/tr>\n
\u9002\u7528\u4e8e\u5185\u5b58\u6620\u5c04 IO<\/td>\n\u2705<\/td>\n\u274c\uff08\u53ef\u80fd\u88ab\u4f18\u5316\uff09<\/td>\n<\/tr>\n
\u9002\u7528\u4e8e\u591a\u7ebf\u7a0b\u5171\u4eab\u53d8\u91cf<\/td>\n\u274c<\/td>\n\u2705<\/td>\n<\/tr>\n
\u8fd0\u884c\u65f6\u5f00\u9500<\/td>\n\u65e0<\/td>\n\u6709\uff08\u5185\u5b58\u5c4f\u969c\u3001\u539f\u5b50\u6307\u4ee4\uff09<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n
\n
\u9762\u8bd5\u91cc\u7684\u4e00\u53e5\u8bdd\u603b\u7ed3<\/h3>\n
volatile<\/code>\u00a0\u89e3\u51b3\u7684\u662f”\u7f16\u8bd1\u5668\u628a\u6211\u7684\u8bfb\u5199\u4f18\u5316\u6389\u4e86”\u7684\u95ee\u9898\uff0c\u9002\u7528\u4e8e\u786c\u4ef6\u5bc4\u5b58\u5668\u548c\u4fe1\u53f7\u5904\u7406\uff1bstd::atomic<\/code>\u00a0\u89e3\u51b3\u7684\u662f”\u591a\u7ebf\u7a0b\u5e76\u53d1\u8bbf\u95ee\u5171\u4eab\u6570\u636e”\u7684\u95ee\u9898\uff0c\u540c\u65f6\u63d0\u4f9b\u539f\u5b50\u6027\u548c\u5185\u5b58\u5e8f\u4fdd\u8bc1\u3002\u4e24\u8005\u9488\u5bf9\u7684\u662f\u5b8c\u5168\u4e0d\u540c\u7684\u95ee\u9898\uff0c\u5728\u591a\u7ebf\u7a0b\u573a\u666f\u91cc\u00a0volatile<\/code>\u00a0\u4e0d\u662f\u00a0atomic<\/code>\u00a0\u7684\u66ff\u4ee3\u54c1\uff0c\u5b83\u6839\u672c\u4e0d\u63d0\u4f9b\u4efb\u4f55\u7ebf\u7a0b\u5b89\u5168\u4fdd\u8bc1\u3002<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"
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