{"id":10021162,"date":"2026-01-04T16:42:52","date_gmt":"2026-01-04T08:42:52","guid":{"rendered":"https:\/\/itmax.cn\/?p=10021162"},"modified":"2026-01-04T16:42:52","modified_gmt":"2026-01-04T08:42:52","slug":"%e6%b7%b1%e5%85%a5%e7%90%86%e8%a7%a3-interlocked-compareexchange%ef%bc%9ac-net-%e5%8e%9f%e5%ad%90%e6%93%8d%e4%bd%9c%e6%a0%b8%e5%bf%83%e5%8e%9f%e7%90%86","status":"publish","type":"post","link":"https:\/\/itmax.cn\/?p=10021162","title":{"rendered":"\u6df1\u5165\u7406\u89e3 Interlocked.CompareExchange\uff1aC#.NET \u539f\u5b50\u64cd\u4f5c\u6838\u5fc3\u539f\u7406"},"content":{"rendered":"<h3>\u4ec0\u4e48\u662f Interlocked.CompareExchange\uff1f<\/h3>\n<p><code>Interlocked.CompareExchange<\/code> \u662f <code>.NET<\/code> \u4e2d <code>System.Threading.Interlocked<\/code> \u7c7b\u7684\u6700\u6838\u5fc3\u539f\u5b50\u64cd\u4f5c\u65b9\u6cd5\u3002\u5b83\u6267\u884c\u6bd4\u8f83\u5e76\u4ea4\u6362\uff08<code>Compare-And-Swap<\/code>\uff0c\u7b80\u79f0 <code>CAS<\/code>\uff09 \u64cd\u4f5c\uff1a\u5728\u591a\u7ebf\u7a0b\u73af\u5883\u4e0b\uff0c\u5b89\u5168\u5730\u5c06\u53d8\u91cf\u7684\u503c\u4e0e\u9884\u671f\u503c\u6bd4\u8f83\uff0c\u5982\u679c\u76f8\u7b49\u5219\u66ff\u6362\u4e3a\u65b0\u503c\uff0c\u6574\u4e2a\u8fc7\u7a0b\u539f\u5b50\u4e0d\u53ef\u4e2d\u65ad\u3002<\/p>\n<p>\u5173\u952e\u7279\u6027<\/p>\n<ul>\n<li>\u539f\u5b50\u6027\uff1a\u6574\u4e2a\u64cd\u4f5c\u5728CPU\u7ea7\u522b\u662f\u539f\u5b50\u7684\uff0c\u4e0d\u4f1a\u88ab\u7ebf\u7a0b\u8c03\u5ea6\u6253\u65ad<\/li>\n<li>\u65e0\u9501\u64cd\u4f5c\uff1a\u65e0\u9700\u4f7f\u7528\u9501\u5373\u53ef\u5b9e\u73b0\u7ebf\u7a0b\u5b89\u5168<\/li>\n<li>\u5185\u5b58\u5c4f\u969c\uff1a\u9690\u542b\u5b8c\u6574\u5185\u5b58\u5c4f\u969c\uff08<code>full fence<\/code>\uff09\uff0c\u786e\u4fdd\u64cd\u4f5c\u524d\u540e\u5185\u5b58\u8bbf\u95ee\u987a\u5e8f<\/li>\n<\/ul>\n<p>\u8fd4\u56de\u503c\u91cd\u8981\u6027\uff1a\u8fd4\u56de\u503c\u662f\u5224\u65ad\u64cd\u4f5c\u662f\u5426\u6210\u529f\u7684\u5173\u952e<\/p>\n<ul>\n<li>\u6838\u5fc3\u7b7e\u540d\uff08\u5e38\u89c1\u91cd\u8f7d\uff09\uff1a<\/li>\n<\/ul>\n<pre><code class=\"csharp\">public static int CompareExchange(ref int location, int value, int comparand);\npublic static long CompareExchange(ref long location, long value, long comparand);\npublic static T CompareExchange&lt;T&gt;(ref T location, T value, T comparand) where T : class;\npublic static float CompareExchange(ref float location, float value, float comparand);\npublic static double CompareExchange(ref double location, double value, double comparand);<\/code><\/pre>\n<ul>\n<li>\n<p>\u53c2\u6570\u89e3\u91ca\uff1a<\/p>\n<ul>\n<li><code>location<\/code>\uff1a\u8981\u64cd\u4f5c\u7684\u5171\u4eab\u53d8\u91cf\uff08\u5fc5\u987b\u7528 <code>ref<\/code> \u4f20\u9012\uff09\u3002<\/li>\n<li><code>value<\/code>\uff1a\u5982\u679c\u6bd4\u8f83\u6210\u529f\uff0c\u8981\u5199\u5165\u7684\u65b0\u503c\u3002<\/li>\n<li><code>comparand<\/code>\uff1a\u9884\u671f\u65e7\u503c\uff08\u7528\u4e8e\u6bd4\u8f83\uff09\u3002<\/li>\n<li>\u8fd4\u56de\u503c\uff1a\u64cd\u4f5c\u524d <code>location<\/code> \u7684\u5b9e\u9645\u503c\uff08\u65e0\u8bba\u6210\u529f\u4e0e\u5426\u90fd\u8fd4\u56de\u65e7\u503c\uff09\u3002<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p><code>CAS<\/code> \u662f\u73b0\u4ee3\u65e0\u9501\uff08<code>lock-free<\/code>\uff09\u5e76\u53d1\u7f16\u7a0b\u7684\u57fa\u7840\uff0c\u8bb8\u591a\u9ad8\u7ea7\u7ed3\u6784\uff08\u5982 <code>ConcurrentDictionary<\/code>\u3001<code>SpinLock<\/code>\uff09\u5185\u90e8\u90fd\u4f9d\u8d56\u5b83\u3002<\/p>\n<h3>\u4e3a\u4ec0\u4e48\u4f7f\u7528 Interlocked.CompareExchange\uff1f<\/h3>\n<p>\u5728\u591a\u7ebf\u7a0b\u4e2d\uff0c\u76f4\u63a5\u8bfb\u53d6-\u4fee\u6539-\u5199\u5165\uff08\u5982 <code>if (count == 0) count = 1;<\/code>\uff09\u4f1a\u4ea7\u751f\u7ade\u4e89\u6761\u4ef6\uff1a\u591a\u4e2a\u7ebf\u7a0b\u53ef\u80fd\u540c\u65f6\u8bfb\u53d6\u76f8\u540c\u503c\uff0c\u5bfc\u81f4\u8986\u76d6\u66f4\u65b0\u3002<\/p>\n<ul>\n<li>\u4f20\u7edf\u9501\u7684\u95ee\u9898\uff1a<code>lock<\/code> \u5f00\u9500\u5927\uff08\u4e92\u65a5\u9501\u3001\u4e0a\u4e0b\u6587\u5207\u6362\uff09\uff0c\u4e0d\u9002\u5408\u9ad8\u9891\u8f7b\u91cf\u64cd\u4f5c\u3002<\/li>\n<li>\n<p><code>CAS<\/code> \u7684\u4f18\u52bf\uff1a<\/p>\n<ul>\n<li>\u65e0\u9501\uff08<code>Lock-Free<\/code>\uff09\uff1a\u4e0d\u963b\u585e\u7ebf\u7a0b\uff0c\u9ad8\u5e76\u53d1\u4e0b\u6027\u80fd\u6781\u9ad8\u3002<\/li>\n<li>\u4e50\u89c2\u5e76\u53d1\uff1a\u5047\u8bbe\u51b2\u7a81\u5c11\uff0c\u5148\u5c1d\u8bd5\u64cd\u4f5c\uff0c\u5931\u8d25\u5219\u91cd\u8bd5\uff08\u81ea\u65cb\uff09\u3002<\/li>\n<li>\u539f\u5b50\u6027\uff1a\u786c\u4ef6\u7ea7\u4fdd\u8bc1\uff08<code>x86 \u7684 cmpxchg<\/code> \u6307\u4ee4\uff09\u3002<\/li>\n<\/ul>\n<\/li>\n<li>\n<p>\u5178\u578b\u5e94\u7528\u573a\u666f\uff1a<\/p>\n<ul>\n<li>\u5b9e\u73b0\u7ebf\u7a0b\u5b89\u5168\u7684\u5355\u4f8b\u6a21\u5f0f\uff08\u53cc\u68c0\u67e5\u9501\uff09\u3002<\/li>\n<li>\u81ea\u5b9a\u4e49\u65e0\u9501\u961f\u5217\/\u6808\u3002<\/li>\n<li>\u539f\u5b50\u66f4\u65b0\u590d\u6742\u72b6\u6001\uff08\u6807\u5fd7\u4f4d + \u8ba1\u6570\u5668\uff09\u3002<\/li>\n<li>\u5b9e\u73b0\u81ea\u5b9a\u4e49\u540c\u6b65\u539f\u8bed\uff08\u5982 <code>SpinLock<\/code>\u3001<code>SemaphoreSlim<\/code> \u5185\u90e8\uff09\u3002<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p>\u4f20\u7edf\u7684 \u201c\u6bd4\u8f83 + \u8d4b\u503c\u201d \u662f\u4e24\u6b65\u975e\u539f\u5b50\u64cd\u4f5c\uff0c\u591a\u7ebf\u7a0b\u4e0b\u4f1a\u56e0\u7ade\u6001\u6761\u4ef6\u5bfc\u81f4\u903b\u8f91\u9519\u8bef\u3002<\/p>\n<pre><code class=\"csharp\">\/\/ \u975e\u539f\u5b50\u64cd\u4f5c\uff1a\u591a\u7ebf\u7a0b\u4e0b\u53ef\u80fd\u540c\u65f6\u901a\u8fc7if\u5224\u65ad\uff0c\u5bfc\u81f4\u8d4b\u503c\u9519\u8bef\nprivate static int _value = 0;\npublic static void UnsafeUpdate(int oldVal, int newVal)\n{\n    if (_value == oldVal) \/\/ \u6b65\u9aa41\uff1a\u8bfb\u53d6\u5e76\u6bd4\u8f83\n    {\n        _value = newVal;  \/\/ \u6b65\u9aa42\uff1a\u8d4b\u503c\n    }\n}<\/code><\/pre>\n<p>\u4e24\u4e2a\u7ebf\u7a0b\u53ef\u80fd\u540c\u65f6\u901a\u8fc7if\u5224\u65ad\uff08\u90fd\u8bfb\u5230 <code>_value=oldVal<\/code> \uff09\uff0c\u6700\u7ec8\u90fd\u6267\u884c\u8d4b\u503c\uff0c\u5bfc\u81f4\u903b\u8f91\u9519\u8bef\u3002<\/p>\n<p><code>Interlocked.CompareExchange<\/code> \u5c06 \u201c\u6bd4\u8f83\u201d \u548c \u201c\u8d4b\u503c\u201d \u5408\u5e76\u4e3a\u4e0d\u53ef\u4e2d\u65ad\u7684\u539f\u5b50\u64cd\u4f5c\uff0c\u4ece\u5e95\u5c42\u675c\u7edd\u7ade\u6001\u6761\u4ef6\uff0c\u4e14\u65e0\u9700\u963b\u585e\u7ebf\u7a0b\uff08\u65e0\u9501\uff09\u3002<\/p>\n<p>\u4e0e <code>lock<\/code> \u7684\u6839\u672c\u533a\u522b<\/p>\n<table>\n<thead>\n<tr>\n<th>\u7ef4\u5ea6<\/th>\n<th>lock<\/th>\n<th>CompareExchange<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>\u662f\u5426\u963b\u585e<\/td>\n<td>\u662f<\/td>\n<td>\u5426<\/td>\n<\/tr>\n<tr>\n<td>\u662f\u5426\u4e0a\u4e0b\u6587\u5207\u6362<\/td>\n<td>\u662f<\/td>\n<td>\u5426<\/td>\n<\/tr>\n<tr>\n<td>\u7c92\u5ea6<\/td>\n<td>\u4efb\u610f\u4ee3\u7801\u5757<\/td>\n<td>\u5355\u53d8\u91cf<\/td>\n<\/tr>\n<tr>\n<td>\u6027\u80fd<\/td>\n<td>\u8f83\u4f4e<\/td>\n<td>\u6781\u9ad8<\/td>\n<\/tr>\n<tr>\n<td>\u9002\u5408<\/td>\n<td>\u590d\u6742\u903b\u8f91<\/td>\n<td>\u72b6\u6001\u5207\u6362<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h3>\u4ec0\u4e48\u65f6\u5019\u8be5\u7528 CompareExchange\uff1f<\/h3>\n<table>\n<thead>\n<tr>\n<th>\u573a\u666f<\/th>\n<th>\u63a8\u8350<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>\u7b80\u5355\u72b6\u6001\u5207\u6362<\/td>\n<td>\u2714<\/td>\n<\/tr>\n<tr>\n<td>\u8ba1\u6570\u3001\u6807\u5fd7\u4f4d<\/td>\n<td>\u2714<\/td>\n<\/tr>\n<tr>\n<td>\u9ad8\u5e76\u53d1\u70ed\u70b9<\/td>\n<td>\u2714<\/td>\n<\/tr>\n<tr>\n<td>\u590d\u6742\u4e1a\u52a1\u6d41\u7a0b<\/td>\n<td>\u274c<\/td>\n<\/tr>\n<tr>\n<td>\u591a\u53d8\u91cf\u4e00\u81f4\u6027<\/td>\n<td>\u274c<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<h3>\u5982\u4f55\u4f7f\u7528 Interlocked.CompareExchange\uff1f<\/h3>\n<h4>\u6700\u7b80\u5355\u7684 CAS \u64cd\u4f5c\uff08\u5224\u65ad\u662f\u5426\u4ea4\u6362\u6210\u529f\uff09<\/h4>\n<pre><code class=\"csharp\">private static int _counter = 0;\n\npublic static void TestCas()\n{\n    \/\/ \u76ee\u6807\uff1a\u5982\u679c_counter\u662f0\uff0c\u5c31\u6539\u4e3a100\n    int expected = 0;    \/\/ \u9884\u671f\u503c\n    int newValue = 100;  \/\/ \u65b0\u503c\n    \n    \/\/ \u6267\u884cCAS\u64cd\u4f5c\n    int original = Interlocked.CompareExchange(ref _counter, newValue, expected);\n    \n    \/\/ \u5224\u65ad\u662f\u5426\u4ea4\u6362\u6210\u529f\uff08\u539f\u59cb\u503c == \u9884\u671f\u503c \u2192 \u6210\u529f\uff09\n    if (original == expected)\n    {\n        Console.WriteLine($&quot;\u4ea4\u6362\u6210\u529f\uff01\u539f\u59cb\u503c\uff1a{original}\uff0c\u65b0\u503c\uff1a{_counter}&quot;);\n    }\n    else\n    {\n        Console.WriteLine($&quot;\u4ea4\u6362\u5931\u8d25\uff01\u539f\u59cb\u503c\uff1a{original}\uff0c\u5f53\u524d\u503c\uff1a{_counter}&quot;);\n    }\n}<\/code><\/pre>\n<p>\u8f93\u51fa\uff1a\u4ea4\u6362\u6210\u529f\uff01\u539f\u59cb\u503c\uff1a0\uff0c\u65b0\u503c\uff1a100\uff08\u82e5\u518d\u6b21\u6267\u884c\uff0c\u4f1a\u8f93\u51fa\u5931\u8d25\uff0c\u56e0\u4e3a<code>_counter<\/code> \u5df2\u4e0d\u662f 0\uff09\u3002<\/p>\n<h4>\u539f\u5b50\u6761\u4ef6\u66f4\u65b0<\/h4>\n<pre><code class=\"csharp\">private int _status = 0;  \/\/ 0: \u672a\u521d\u59cb\u5316, 1: \u521d\u59cb\u5316\u4e2d, 2: \u5df2\u5b8c\u6210\n\npublic void Initialize()\n{\n    if (Interlocked.CompareExchange(ref _status, 1, 0) == 0)\n    {\n        \/\/ \u53ea\u6709\u7b2c\u4e00\u4e2a\u7ebf\u7a0b\u8fdb\u5165\u8fd9\u91cc\n        try\n        {\n            \/\/ \u6267\u884c\u521d\u59cb\u5316\u903b\u8f91\n            DoInitialize();\n        }\n        finally\n        {\n            \/\/ \u6807\u8bb0\u5b8c\u6210\uff08\u539f\u5b50\u64cd\u4f5c\uff0c\u65e0\u9700 CAS\uff09\n            Interlocked.Exchange(ref _status, 2);\n        }\n    }\n    else\n    {\n        \/\/ \u5176\u4ed6\u7ebf\u7a0b\u7b49\u5f85\u5b8c\u6210\n        while (_status != 2) Thread.SpinWait(10);\n    }\n}<\/code><\/pre>\n<ul>\n<li>\u89e3\u91ca\uff1a\u53ea\u6709\u5f53 <code>_status<\/code> \u4e3a 0 \u65f6\u624d\u8bbe\u7f6e\u4e3a 1 \u5e76\u6267\u884c\u521d\u59cb\u5316\u3002<\/li>\n<\/ul>\n<h4>\u5b9e\u73b0\u81ea\u65cb\u9501<\/h4>\n<pre><code class=\"csharp\">public class SpinLock\n{\n    private int _lock = 0; \/\/ 0=\u672a\u9501\u5b9a, 1=\u5df2\u9501\u5b9a\n    \n    public void Enter()\n    {\n        while (Interlocked.CompareExchange(ref _lock, 1, 0) != 0)\n        {\n            \/\/ \u7b49\u5f85 - \u53ef\u4ee5\u4f7f\u7528Thread.SpinWait\u4f18\u5316\n            Thread.SpinWait(100);\n        }\n    }\n    \n    public void Exit()\n    {\n        Interlocked.Exchange(ref _lock, 0);\n    }\n}<\/code><\/pre>\n<h4>\u7ecf\u5178\u573a\u666f\uff1a\u65e0\u9501\u8ba1\u6570\u5668\uff08\u5faa\u73af CAS\uff09<\/h4>\n<p>\u5355\u6b21 <code>CAS<\/code> \u53ef\u80fd\u56e0\u5176\u4ed6\u7ebf\u7a0b\u4fee\u6539\u53d8\u91cf\u5931\u8d25\uff0c\u9700\u5faa\u73af\u91cd\u8bd5\uff08\u81ea\u65cb <code>CAS<\/code>\uff09\uff0c\u5b9e\u73b0\u7ebf\u7a0b\u5b89\u5168\u7684\u8ba1\u6570\u5668\uff1a<\/p>\n<pre><code class=\"csharp\">private static int _casCounter = 0;\n\n\/\/\/ &lt;summary&gt;\n\/\/\/ \u65e0\u9501\u539f\u5b50\u9012\u589e\uff08\u66ff\u4ee3Interlocked.Increment\uff09\n\/\/\/ &lt;\/summary&gt;\npublic static int IncrementCounter()\n{\n    int current;   \/\/ \u5f53\u524d\u503c\n    int newValue;  \/\/ \u65b0\u503c\n    do\n    {\n        \/\/ 1. \u539f\u5b50\u8bfb\u53d6\u5f53\u524d\u503c\uff08Interlocked\u4fdd\u8bc1\u53ef\u89c1\u6027\uff09\n        current = _casCounter;\n        \/\/ 2. \u8ba1\u7b97\u65b0\u503c\uff08\u4ec5\u672c\u5730\u8ba1\u7b97\uff0c\u65e0\u7ade\u6001\uff09\n        newValue = current + 1;\n        \/\/ 3. CAS\u64cd\u4f5c\uff1a\u82e5\u5f53\u524d\u503c\u672a\u88ab\u4fee\u6539\uff0c\u5c31\u66f4\u65b0\u4e3a\u65b0\u503c\n        \/\/ \u8fd4\u56de\u503c\u2260current \u2192 \u88ab\u5176\u4ed6\u7ebf\u7a0b\u4fee\u6539\uff0c\u91cd\u8bd5\n    } while (Interlocked.CompareExchange(ref _casCounter, newValue, current) != current);\n    \n    return newValue; \/\/ \u8fd4\u56de\u9012\u589e\u540e\u7684\u503c\n}\n\n\/\/ \u6d4b\u8bd5\uff1a1000\u4e2a\u7ebf\u7a0b\u5404\u8c03\u75281\u6b21\uff0c\u6700\u7ec8\u7ed3\u679c\u5fc5\u4e3a1000\nvar tasks = Enumerable.Range(0, 1000)\n    .Select(_ =&gt; Task.Run(IncrementCounter))\n    .ToList();\nTask.WaitAll(tasks.ToArray());\nConsole.WriteLine($&quot;\u6700\u7ec8\u8ba1\u6570\u5668\u503c\uff1a{_casCounter}&quot;); \/\/ \u8f93\u51fa\uff1a1000<\/code><\/pre>\n<h3>\u9ad8\u7ea7\u5e94\u7528\u573a\u666f<\/h3>\n<h4>\u6cdb\u578b\u7248\u672c\uff1a\u61d2\u52a0\u8f7d\u5355\u4f8b\uff08\u53cc\u68c0\u67e5\u9501\u6a21\u5f0f\uff09<\/h4>\n<pre><code class=\"csharp\">public sealed class Singleton\n{\n    private static Singleton _instance = null;\n\n    private Singleton() { }\n\n    public static Singleton Instance\n    {\n        get\n        {\n            if (_instance == null)\n            {\n                var temp = new Singleton();\n                Interlocked.CompareExchange(ref _instance, temp, null);\n            }\n            return _instance;\n        }\n    }\n}<\/code><\/pre>\n<p>\u5728 <code>.NET<\/code> \u4e2d\u9700\u52a0 <code>Lazy&lt;T&gt;<\/code> \u66f4\u5b89\u5168\uff1a<\/p>\n<pre><code class=\"csharp\">private static Lazy&lt;Singleton&gt; _instance = new Lazy&lt;Singleton&gt;(() =&gt; new Singleton());\npublic static Singleton Instance =&gt; _instance.Value;<\/code><\/pre>\n<h4>\u65e0\u9501\u72b6\u6001\u673a\uff08\u539f\u5b50\u72b6\u6001\u8f6c\u6362\uff09<\/h4>\n<p>\u63a7\u5236\u5bf9\u8c61\u72b6\u6001\u7684\u539f\u5b50\u8f6c\u6362\uff08\u5982\u4ece <code>Idle\u2192Running<\/code> \uff0c\u907f\u514d\u72b6\u6001\u6df7\u4e71\uff09\uff1a<\/p>\n<pre><code class=\"csharp\">\/\/ \u5b9a\u4e49\u72b6\u6001\u679a\u4e3e\npublic enum TaskState { Idle, Running, Completed, Failed }\n\npublic class TaskStateMachine\n{\n    private TaskState _state = TaskState.Idle;\n\n    \/\/\/ &lt;summary&gt;\n    \/\/\/ \u539f\u5b50\u8f6c\u6362\uff1aIdle \u2192 Running\uff08\u4ec5\u5f53\u72b6\u6001\u4e3aIdle\u65f6\u6210\u529f\uff09\n    \/\/\/ &lt;\/summary&gt;\n    public bool TryStart()\n    {\n        TaskState original = Interlocked.CompareExchange(\n            ref _state, \n            TaskState.Running,  \/\/ \u65b0\u503c\n            TaskState.Idle      \/\/ \u9884\u671f\u503c\n        );\n        return original == TaskState.Idle; \/\/ \u539f\u59cb\u503c=\u9884\u671f\u503c \u2192 \u8f6c\u6362\u6210\u529f\n    }\n\n    \/\/\/ &lt;summary&gt;\n    \/\/\/ \u539f\u5b50\u8f6c\u6362\uff1aRunning \u2192 Completed\n    \/\/\/ &lt;\/summary&gt;\n    public bool TryComplete()\n    {\n        TaskState original = Interlocked.CompareExchange(\n            ref _state, \n            TaskState.Completed, \n            TaskState.Running\n        );\n        return original == TaskState.Running;\n    }\n}\n\n\/\/ \u4f7f\u7528\nvar stateMachine = new TaskStateMachine();\nConsole.WriteLine(stateMachine.TryStart());    \/\/ true\uff08\u72b6\u6001\u53d8\u4e3aRunning\uff09\nConsole.WriteLine(stateMachine.TryStart());    \/\/ false\uff08\u5df2\u4e0d\u662fIdle\uff09\nConsole.WriteLine(stateMachine.TryComplete()); \/\/ true\uff08\u72b6\u6001\u53d8\u4e3aCompleted\uff09<\/code><\/pre>\n<h4>\u81ea\u65cb\u5b9e\u73b0\u539f\u5b50\u52a0\u6cd5\uff08\u6a21\u62df Interlocked.Add\uff09<\/h4>\n<pre><code class=\"csharp\">private int _counter = 0;\n\npublic int Increment()\n{\n    int oldValue, newValue;\n    do\n    {\n        oldValue = _counter;\n        newValue = oldValue + 1;\n    } while (Interlocked.CompareExchange(ref _counter, newValue, oldValue) != oldValue);\n    return newValue;\n}<\/code><\/pre>\n<ul>\n<li>\u89e3\u91ca\uff1a\u5faa\u73af\u76f4\u5230 <code>CAS<\/code> \u6210\u529f\uff08\u81ea\u65cb\uff09\uff0c\u5b9e\u73b0\u65e0\u9501\u9012\u589e<\/li>\n<\/ul>\n<h4>\u5bf9\u8c61\u5f15\u7528\u66ff\u6362\uff08\u7ebf\u7a0b\u5b89\u5168\u8d4b\u503c\uff09<\/h4>\n<pre><code class=\"csharp\">private List&lt;int&gt; _cache = null;\n\npublic void UpdateCache(List&lt;int&gt; newCache)\n{\n    Interlocked.CompareExchange(ref _cache, newCache, _cache);  \/\/ \u4ec5\u5f53\u672a\u88ab\u5176\u4ed6\u7ebf\u7a0b\u4fee\u6539\u65f6\u66f4\u65b0\n}<\/code><\/pre>\n<h3>Interlocked.CompareExchange \u7684\u5185\u90e8\u5b9e\u73b0<\/h3>\n<ul>\n<li>\n<p>\u786c\u4ef6\u652f\u6301\uff1a<\/p>\n<ul>\n<li><code>x86\/x64<\/code>\uff1a<code>LOCK CMPXCHG<\/code> \u6307\u4ee4\uff0c\u603b\u7ebf\u9501\u4fdd\u8bc1\u539f\u5b50\u6027\u3002<\/li>\n<li><code>ARM<\/code>\uff1aLDREX\/STREX \u6307\u4ee4\u5bf9\uff08<code>Load-Exclusive\/Store-Exclusive<\/code>\uff09\uff0c\u5931\u8d25\u91cd\u8bd5\u3002<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<p>\u540c\u65f6\uff0c\u8be5\u64cd\u4f5c\u4f1a\u89e6\u53d1\u5168\u5185\u5b58\u5c4f\u969c\uff08<code>Full Memory Barrier<\/code>\uff09\uff1a<\/p>\n<ul>\n<li>\u4fdd\u8bc1\u64cd\u4f5c\u524d\u540e\u7684\u5185\u5b58\u8bfb\u5199\u4e0d\u4f1a\u88ab <code>CPU<\/code> \u91cd\u6392\u5e8f\uff1b<\/li>\n<li>\u786e\u4fdd\u6240\u6709\u7ebf\u7a0b\u80fd\u7acb\u5373\u770b\u5230\u53d8\u91cf\u7684\u6700\u65b0\u503c\uff08\u907f\u514d <code>CPU<\/code> \u7f13\u5b58\u5bfc\u81f4\u7684 \u201c\u810f\u8bfb\u201d\uff09\u3002<\/li>\n<li><code>.NET<\/code> \u5b9e\u73b0\uff08<code>CoreCLR<\/code> \u7b80\u5316\u4f2a\u7801\uff09\uff1a<\/li>\n<\/ul>\n<pre><code class=\"csharp\">public static int CompareExchange(ref int location, int value, int comparand)\n{\n    \/\/ \u5185\u8054\u4e3a\u5e73\u53f0\u7279\u5b9a\u539f\u5b50\u6307\u4ee4\n    fixed (int* ptr = &amp;location)\n    {\n        return InterlockedCompareExchange(ptr, value, comparand);\n    }\n}<\/code><\/pre>\n<ul>\n<li>\n<p>\u6027\u80fd\uff1a<\/p>\n<ul>\n<li>\u65e0\u7ade\u4e89\uff1a<code>O(1)<\/code>\uff0c\u6781\u5feb\u3002<\/li>\n<li>\u9ad8\u7ade\u4e89\uff1a\u81ea\u65cb\u6d88\u8017 <code>CPU<\/code>\uff0c\u4f46\u4ecd\u8fdc\u4f18\u4e8e\u9501\uff08\u65e0\u4e0a\u4e0b\u6587\u5207\u6362\uff09\u3002<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<h3>\u6ce8\u610f\u4e8b\u9879\u4e0e\u6700\u4f73\u5b9e\u8df5<\/h3>\n<ul>\n<li>\u81ea\u65cb\u5faa\u73af\uff1a\u603b\u662f\u7528 <code>do-while<\/code> \u5305\u88c5 <code>CAS<\/code>\uff0c\u5f62\u6210\u201c\u4e50\u89c2\u5faa\u73af\u201d\u3002<\/li>\n<li>\n<p><code>ABA<\/code> \u95ee\u9898\uff1a<\/p>\n<ul>\n<li>\u7ebf\u7a0b 1 \u8bfb\u53d6\u503c\u4e3aA\uff0c\u51c6\u5907 <code>CAS<\/code> \u4e3aC\uff1b\u7ebf\u7a0b 2 \u5c06A\u6539\u4e3aB\uff0c\u53c8\u6539\u56deA\uff1b\u7ebf\u7a0b 1 \u7684 <code>CAS<\/code> \u4f1a\u6210\u529f\uff0c\u4f46\u4e2d\u95f4\u72b6\u6001\u5df2\u53d8\u5316\uff0c\u53ef\u80fd\u5bfc\u81f4\u903b\u8f91\u9519\u8bef<\/li>\n<li>\u89e3\u51b3\u65b9\u6cd5\uff1a\u7248\u672c\u53f7 + \u5f15\u7528 <code>CAS<\/code>\u3002<\/li>\n<\/ul>\n<\/li>\n<li>\u5185\u5b58\u53ef\u89c1\u6027\uff1a<code>Interlocked<\/code> \u64cd\u4f5c\u81ea\u5e26\u5168\u5185\u5b58\u5c4f\u969c\uff08<code>full fence<\/code>\uff09\uff0c\u65e0\u9700\u989d\u5916 <code>volatile<\/code>\u3002<\/li>\n<li>\u907f\u514d\u8fc7\u5ea6\u4f7f\u7528\uff1a\u7b80\u5355\u8ba1\u6570\u7528 <code>Interlocked.Increment<\/code>\uff1b\u96c6\u5408\u7528 <code>Concurrent<\/code> \u7c7b\u3002<\/li>\n<li>\n<p>\u66ff\u4ee3\u65b9\u6848\uff1a<\/p>\n<ul>\n<li>\u9ad8\u5c42\uff1a<code>ConcurrentDictionary\u3001BlockingCollection<\/code>\u3002<\/li>\n<li>\u73b0\u4ee3\uff1a<code>System.Threading.Channels<\/code>\uff08\u751f\u4ea7\u8005-\u6d88\u8d39\u8005\uff09\u3002<\/li>\n<li><code>.NET 8+<\/code>\uff1a\u8003\u8651 <code>System.Threading.Lock<\/code>\uff08<code>C# 12<\/code> \u65b0\u7279\u6027\uff0c\u66f4\u7b80\u6d01\uff09\u3002<\/li>\n<\/ul>\n<\/li>\n<\/ul>\n<h3>ABA \u95ee\u9898<\/h3>\n<h4>\u4ec0\u4e48\u662f ABA \u95ee\u9898\uff1f<\/h4>\n<p><code>ABA<\/code> \u95ee\u9898 \u662f\u65e0\u9501\uff08<code>lock-free<\/code>\uff09\u7f16\u7a0b\u4e2d\u4f7f\u7528 <code>Compare-And-Swap<\/code> (<code>CAS<\/code>) \u64cd\u4f5c\u65f6\u7684\u4e00\u79cd\u7ecf\u5178\u9690\u60a3\u3002<\/p>\n<p>\u573a\u666f\u63cf\u8ff0\uff1a<\/p>\n<ul>\n<li>\u7ebf\u7a0b A \u8bfb\u53d6\u5171\u4eab\u53d8\u91cf\u503c\uff1aA<\/li>\n<li>\u7ebf\u7a0b B \u5148\u5c06\u503c\u6539\u4e3a B\uff0c\u7136\u540e\u53c8\u6539\u56de A<\/li>\n<li>\u7ebf\u7a0b A \u6267\u884c <code>CAS<\/code>\uff1a\u671f\u671b\u503c\u662f A\uff0c\u5f53\u524d\u503c\u4e5f\u662f A \u2192 <code>CAS<\/code> \u6210\u529f\uff01<\/li>\n<li>\u4f46\u5b9e\u9645\u4e0a\u503c\u5df2\u7ecf\u88ab\u5176\u4ed6\u7ebf\u7a0b\u4fee\u6539\u8fc7\uff0c\u8bed\u4e49\u5df2\u7ecf\u6539\u53d8\uff0c\u7ebf\u7a0b A \u5374\u8bef\u4ee5\u4e3a\u201c\u4e00\u5207\u672a\u53d8\u201d\u3002<\/li>\n<\/ul>\n<p>\u8fd9\u4f1a\u5bfc\u81f4\u903b\u8f91\u9519\u8bef\uff0c\u5c24\u5176\u5728\u65e0\u9501\u6808\u3001\u961f\u5217\u7b49\u6570\u636e\u7ed3\u6784\u4e2d\uff0c\u53ef\u80fd\u9020\u6210\u8282\u70b9\u4e22\u5931\u3001\u5faa\u73af\u5f15\u7528\u6216\u5185\u5b58\u6cc4\u6f0f\u3002<\/p>\n<h4>\u89e3\u51b3\u65b9\u6848\uff1a\u7248\u672c\u53f7 + \u5f15\u7528 CAS<\/h4>\n<ol>\n<li>\u5b9a\u4e49\u300c\u7248\u672c\u5316\u72b6\u6001\u5bf9\u8c61\u300d<\/li>\n<\/ol>\n<pre><code class=\"csharp\">sealed class VersionedValue\n{\n    public readonly int Value;\n    public readonly int Version;\n\n    public VersionedValue(int value, int version)\n    {\n        Value = value;\n        Version = version;\n    }\n\n    public override string ToString()\n        =&gt; $&quot;Value={Value}, Version={Version}&quot;;\n}<\/code><\/pre>\n<p>\u5173\u952e\u70b9\uff1a<\/p>\n<ul>\n<li>\u4e0d\u53ef\u53d8\uff08<code>readonly<\/code>\uff09<\/li>\n<li>\u6bcf\u6b21\u4fee\u6539 \u2192 \u65b0\u5bf9\u8c61<\/li>\n<li><code>CAS<\/code> \u6bd4\u8f83\u7684\u662f \u5bf9\u8c61\u5f15\u7528<\/li>\n<\/ul>\n<ol start=\"2\">\n<li>\u8fd0\u884c\u793a\u4f8b<\/li>\n<\/ol>\n<pre><code class=\"csharp\">using System;\nusing System.Threading;\nusing System.Threading.Tasks;\n\nclass Program\n{\n    static VersionedValue state = new VersionedValue(1, 0);\n\n    static void Main()\n    {\n        var t1 = Task.Run(Thread1);\n        var t2 = Task.Run(Thread2);\n\n        Task.WaitAll(t1, t2);\n\n        Console.WriteLine($&quot;Final state: {state}&quot;);\n    }\n\n    static void Thread1()\n    {\n        var old = state; \/\/ \u8bfb A(v0)\n        Console.WriteLine($&quot;T1 read: {old}&quot;);\n\n        Thread.Sleep(200);\n\n        var newState = new VersionedValue(3, old.Version + 1);\n\n        var result = Interlocked.CompareExchange(\n            ref state,\n            newState,\n            old\n        );\n\n        if (result == old)\n        {\n            Console.WriteLine(&quot;T1 CAS succeeded&quot;);\n        }\n        else\n        {\n            Console.WriteLine($&quot;T1 CAS failed, current = {result}&quot;);\n        }\n    }\n\n    static void Thread2()\n    {\n        Thread.Sleep(50);\n\n        \/\/ A \u2192 B\n        state = new VersionedValue(2, state.Version + 1);\n        \/\/ B \u2192 A\n        state = new VersionedValue(1, state.Version + 1);\n\n        Console.WriteLine($&quot;T2 changed state twice: {state}&quot;);\n    }\n}<\/code><\/pre>\n<ol start=\"3\">\n<li>\u5178\u578b\u8f93\u51fa<\/li>\n<\/ol>\n<pre><code>T1 read: Value=1, Version=0\nT2 changed state twice: Value=1, Version=2\nT1 CAS failed, current = Value=1, Version=2\nFinal state: Value=1, Version=2<\/code><\/pre>\n<p>\u6838\u5fc3\u7ed3\u679c\uff1a<\/p>\n<ul>\n<li>\u503c\u8fd8\u662f 1<\/li>\n<li>\u7248\u672c\u5df2\u7ecf\u53d8\u4e86<\/li>\n<li><code>CAS<\/code> \u5931\u8d25<\/li>\n<li><code>ABA<\/code> \u88ab\u6210\u529f\u8bc6\u522b<\/li>\n<\/ul>\n<h4>\u4e3a\u4ec0\u4e48\u8fd9\u4e2a\u65b9\u6848\u4e00\u5b9a\u80fd\u9632 ABA\uff1f<\/h4>\n<blockquote><p>CAS \u6bd4\u8f83\u7684\u662f\u201c\u5bf9\u8c61\u5f15\u7528\u201d\uff0c\u800c\u4e0d\u662f\u503c<\/p><\/blockquote>\n<p>\u5373\u4f7f\uff1a<\/p>\n<pre><code>Value: 1 \u2192 2 \u2192 1<\/code><\/pre>\n<p>\u4f46\uff1a<\/p>\n<pre><code>Reference: A \u2192 B \u2192 C<\/code><\/pre>\n<p>A \u2260 C<\/p>\n<p><code>CAS<\/code> \u4e0d\u53ef\u80fd\u8bef\u5224\u6210\u529f<\/p>\n<h4>\u9ec4\u91d1\u7ec4\u5408<\/h4>\n<table>\n<thead>\n<tr>\n<th>\u6280\u672f<\/th>\n<th>\u4f5c\u7528<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Interlocked.CompareExchange<\/td>\n<td>\u539f\u5b50\u6027<\/td>\n<\/tr>\n<tr>\n<td>\u4e0d\u53ef\u53d8\u5bf9\u8c61<\/td>\n<td>\u6d88\u9664\u4e2d\u95f4\u6001<\/td>\n<\/tr>\n<tr>\n<td>\u7248\u672c\u53f7<\/td>\n<td>\u660e\u786e\u53d8\u5316\u5386\u53f2<\/td>\n<\/tr>\n<tr>\n<td>GC<\/td>\n<td>\u907f\u514d\u60ac\u5782\u6307\u9488<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<blockquote><p>.NET \u5b98\u65b9\u5e76\u53d1\u96c6\u5408\u3001Immutable \u7cfb\u5217\uff0c\u90fd\u662f\u8fd9\u4e2a\u601d\u60f3<\/p><\/blockquote>\n<h4>\u4ec0\u4e48\u65f6\u5019\u8be5\u7528\u8fd9\u4e00\u5957\uff1f<\/h4>\n<p>\u9002\u5408\uff1a<\/p>\n<ul>\n<li>\u81ea\u5b9a\u4e49\u72b6\u6001\u673a<\/li>\n<li><code>CAS<\/code> + \u72b6\u6001\u5207\u6362<\/li>\n<li>\u65e0\u9501\u7f13\u5b58<\/li>\n<li>\u9ad8\u9891\u5e76\u53d1\u66f4\u65b0<\/li>\n<\/ul>\n<p>\u4e0d\u9002\u5408\uff1a<\/p>\n<ul>\n<li>\u666e\u901a\u8ba1\u6570<\/li>\n<li>\u7b80\u5355\u6807\u5fd7\u4f4d<\/li>\n<li>\u4f4e\u5e76\u53d1\u4e1a\u52a1<\/li>\n<\/ul>\n<h3>\u603b\u7ed3<\/h3>\n<blockquote>\n<p>Interlocked.CompareExchange \u662f .NET \u65e0\u9501\u5e76\u53d1\u7684\u201c\u539f\u5b50\u5f00\u5173\u201d<br \/>\u7528\u5b83\u53ef\u4ee5\uff1a<\/p>\n<ul>\n<li>\u4e0d\u52a0\u9501<\/li>\n<li>\u4e0d\u963b\u585e<\/li>\n<li>\u5728\u7ade\u4e89\u4e2d\u5b89\u5168\u4fee\u6539\u72b6\u6001<\/li>\n<\/ul>\n<\/blockquote>\n<p><a href=\"https:\/\/segmentfault.com\/a\/1190000047519594\">https:\/\/segmentfault.com\/a\/1190000047519594<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>\u4ec0\u4e48\u662f Interlocked.CompareExchange\uff1f Interlocked.CompareExc [&hellip;]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_memberships_contains_paid_content":false,"footnotes":""},"categories":[4],"tags":[],"class_list":["post-10021162","post","type-post","status-publish","format-standard","hentry","category-share"],"jetpack_sharing_enabled":true,"jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/posts\/10021162","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/itmax.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=10021162"}],"version-history":[{"count":0,"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/posts\/10021162\/revisions"}],"wp:attachment":[{"href":"https:\/\/itmax.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=10021162"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/itmax.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=10021162"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/itmax.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=10021162"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}