{"id":10008331,"date":"2023-09-25T19:55:39","date_gmt":"2023-09-25T11:55:39","guid":{"rendered":"https:\/\/blog.itmax.cn\/?p=10008331"},"modified":"2023-09-25T19:55:39","modified_gmt":"2023-09-25T11:55:39","slug":"%e6%8e%a2%e7%b4%a2%e6%8a%bd%e8%b1%a1%e5%90%8c%e6%ad%a5%e9%98%9f%e5%88%97-aqs","status":"publish","type":"post","link":"https:\/\/itmax.cn\/?p=10008331","title":{"rendered":"\u63a2\u7d22\u62bd\u8c61\u540c\u6b65\u961f\u5217 AQS"},"content":{"rendered":"<blockquote><p>by\u00a0emanjusaka from\u00a0<a target=\"_blank\" href=\"https:\/\/link.segmentfault.com\/?enc=xRXwgnpXWBFS%2FG4ng2J2og%3D%3D.04Oifrbi9Ho%2Fufzlw49glSQYt%2FDq3awye6c1xw8f8Yl6GAZCFEDxjgpoS4Yn0lJk\" rel=\"noopener noreferrer\">https:\/\/www.emanjusaka.top\/archives\/8<\/a>\u00a0\u5f7c\u5cb8\u82b1\u5f00\u53ef\u5948\u4f55  <br \/>\u672c\u6587\u6b22\u8fce\u5206\u4eab\u4e0e\u805a\u5408\uff0c\u5168\u6587\u8f6c\u8f7d\u8bf7\u7559\u4e0b\u539f\u6587\u5730\u5740\u3002<\/p><\/blockquote>\n<h2>\u524d\u8a00<\/h2>\n<p>AbstractQueuedSynchronizer\u62bd\u8c61\u540c\u6b65\u961f\u5217\u7b80\u79f0AQS\uff0c\u5b83\u662f\u5b9e\u73b0\u540c\u6b65\u5668\u7684\u57fa\u7840\u7ec4\u4ef6\uff0c\u5e76\u53d1\u5305\u4e2d\u9501\u7684\u5e95\u5c42\u5c31\u662f\u4f7f\u7528AQS\u5b9e\u73b0\u7684\u3002\u5927\u591a\u6570\u5f00\u53d1\u8005\u53ef\u80fd\u6c38\u8fdc\u4e0d\u4f1a\u76f4\u63a5\u4f7f\u7528AQS\uff0c\u4f46\u662f\u77e5\u9053\u5176\u539f\u7406\u5bf9\u4e8e\u67b6\u6784\u8bbe\u8ba1\u8fd8\u662f\u5f88\u6709\u5e2e\u52a9\u7684\u3002AQS\u662fJava\u4e2d\u7684\u4e00\u4e2a\u62bd\u8c61\u7c7b\uff0c\u5168\u79f0\u662fAbstractQueuedSynchronizer\uff0c\u5373\u62bd\u8c61\u961f\u5217\u540c\u6b65\u5668\u3002\u5b83\u5b9a\u4e49\u4e86\u4e24\u79cd\u8d44\u6e90\u5171\u4eab\u6a21\u5f0f\uff1a\u72ec\u5360\u5f0f\u548c\u5171\u4eab\u5f0f\u3002\u72ec\u5360\u5f0f\u6bcf\u6b21\u53ea\u80fd\u6709\u4e00\u4e2a\u7ebf\u7a0b\u6301\u6709\u9501\uff0c\u4f8b\u5982ReentrantLock\u5b9e\u73b0\u7684\u5c31\u662f\u72ec\u5360\u5f0f\u7684\u9501\u8d44\u6e90\uff1b\u5171\u4eab\u5f0f\u5141\u8bb8\u591a\u4e2a\u7ebf\u7a0b\u540c\u65f6\u83b7\u53d6\u9501\uff0c\u5e76\u53d1\u8bbf\u95ee\u5171\u4eab\u8d44\u6e90\uff0cReentrantReadWriteLock\u548cCountDownLatch\u7b49\u5c31\u662f\u5b9e\u73b0\u7684\u8fd9\u79cd\u6a21\u5f0f\u3002AQS\u7ef4\u62a4\u4e86\u4e00\u4e2avolatile\u7684state\u53d8\u91cf\u548c\u4e00\u4e2aFIFO\uff08\u5148\u8fdb\u5148\u51fa\uff09\u7684\u961f\u5217\u3002\u5176\u4e2dstate\u53d8\u91cf\u4ee3\u8868\u7684\u662f\u7ade\u4e89\u8d44\u6e90\u6807\u8bc6\uff0c\u800c\u961f\u5217\u4ee3\u8868\u7684\u662f\u7ade\u4e89\u8d44\u6e90\u5931\u8d25\u7684\u7ebf\u7a0b\u6392\u961f\u65f6\u5b58\u653e\u7684\u5bb9\u5668 \u3002<\/p>\n<h2>\u4e00\u3001\u539f\u7406<\/h2>\n<p>AQS\u7684\u6838\u5fc3\u601d\u60f3\u662f\u901a\u8fc7\u4e00\u4e2aFIFO\u7684\u961f\u5217\u6765\u7ba1\u7406\u7ebf\u7a0b\u7684\u7b49\u5f85\u548c\u5524\u9192\uff0c\u540c\u65f6\u7ef4\u62a4\u4e86\u4e00\u4e2astate\u53d8\u91cf\u6765\u8868\u793a\u540c\u6b65\u72b6\u6001\uff0c\u53ef\u4ee5\u901a\u8fc7getState\u3001setState\u3001compareAndSetState\u51fd\u6570\u4fee\u6539\u5176\u503c\u3002\u5f53\u4e00\u4e2a\u7ebf\u7a0b\u60f3\u8981\u83b7\u53d6\u9501\u65f6\uff0c\u5982\u679cstate\u4e3a0\uff0c\u5219\u8868\u793a\u8be5\u7ebf\u7a0b\u83b7\u53d6\u9501\u6210\u529f\uff0c\u5426\u5219\u8868\u793a\u8be5\u7ebf\u7a0b\u83b7\u53d6\u9501\u5931\u8d25\u3002\u5b83\u5c06\u88ab\u653e\u5165\u7b49\u5f85\u961f\u5217\u4e2d\uff0c\u76f4\u5230\u6ee1\u8db3\u7279\u5b9a\u6761\u4ef6\u624d\u80fd\u518d\u6b21\u5c1d\u8bd5\u83b7\u53d6\u3002\u5f53\u4e00\u4e2a\u7ebf\u7a0b\u91ca\u653e\u9501\u65f6\uff0c\u5982\u679cstate\u4e3a1\uff0c\u5219\u8868\u793a\u8be5\u7ebf\u7a0b\u91ca\u653e\u9501\u6210\u529f\uff0c\u5426\u5219\u8868\u793a\u8be5\u7ebf\u7a0b\u91ca\u653e\u9501\u5931\u8d25\u3002AQS\u901a\u8fc7CAS\u64cd\u4f5c\u6765\u5b9e\u73b0\u52a0\u9501\u548c\u89e3\u9501\u3002<\/p>\n<h3>1.1 CLH\u961f\u5217<\/h3>\n<p>\u200b<img decoding=\"async\"   referrerpolicy=\"no-referrer\" src=\"https:\/\/segmentfault.com\/img\/remote\/1460000044256519\" alt=\"CLH\u961f\u5217\" title=\"CLH\u961f\u5217\">\u200b<\/p>\n<p>AQS\u4e2d\u7684CLH\u961f\u5217\u9501\u662fCLH\u9501\u7684\u4e00\u79cd\u53d8\u4f53\uff0c\u5c06\u81ea\u65cb\u64cd\u4f5c\u6539\u6210\u4e86\u963b\u585e\u7ebf\u7a0b\u64cd\u4f5c\u3002AQS \u4e2d\u7684\u5bf9 CLH \u9501\u6570\u636e\u7ed3\u6784\u7684\u6539\u8fdb\u4e3b\u8981\u5305\u62ec\u4e09\u65b9\u9762\uff1a\u6269\u5c55\u6bcf\u4e2a\u8282\u70b9\u7684\u72b6\u6001\u3001\u663e\u5f0f\u7684\u7ef4\u62a4\u524d\u9a71\u8282\u70b9\u548c\u540e\u7ee7\u8282\u70b9\u4ee5\u53ca\u8bf8\u5982\u51fa\u961f\u8282\u70b9\u663e\u5f0f\u8bbe\u4e3a null \u7b49\u8f85\u52a9 GC \u7684\u4f18\u5316\u3002<\/p>\n<p>\u5728 AQS\uff08AbstractQueuedSynchronizer\uff09\u4e2d\u4f7f\u7528\u7684 CLH \u961f\u5217\uff0chead \u6307\u9488\u548c tail \u6307\u9488\u5206\u522b\u6307\u5411 CLH \u961f\u5217\u4e2d\u7684\u4e24\u4e2a\u5173\u952e\u8282\u70b9\u3002<\/p>\n<ol>\n<li>head \u6307\u9488\uff1ahead \u6307\u9488\u6307\u5411 CLH \u961f\u5217\u4e2d\u7684\u9996\u4e2a\u8282\u70b9\uff0c\u8be5\u8282\u70b9\u8868\u793a\u5f53\u524d\u6301\u6709\u9501\u7684\u7ebf\u7a0b\u3002\u5f53\u4e00\u4e2a\u7ebf\u7a0b\u6210\u529f\u5730\u83b7\u53d6\u5230\u9501\u65f6\uff0c\u5b83\u5c31\u6210\u4e3a\u4e86\u6301\u6709\u9501\u7684\u7ebf\u7a0b\uff0c\u5e76\u4e14\u4f1a\u5c06\u8be5\u4fe1\u606f\u8bb0\u5f55\u5728 head \u6307\u9488\u6240\u6307\u5411\u7684\u8282\u70b9\u4e2d\u3002<\/li>\n<li>tail \u6307\u9488\uff1atail \u6307\u9488\u6307\u5411 CLH \u961f\u5217\u4e2d\u7684\u6700\u540e\u4e00\u4e2a\u8282\u70b9\uff0c\u8be5\u8282\u70b9\u8868\u793a\u961f\u5217\u4e2d\u6700\u540e\u4e00\u4e2a\u7b49\u5f85\u83b7\u53d6\u9501\u7684\u7ebf\u7a0b\u3002\u5f53\u4e00\u4e2a\u7ebf\u7a0b\u5c1d\u8bd5\u83b7\u53d6\u9501\u65f6\uff0c\u5b83\u4f1a\u751f\u6210\u4e00\u4e2a\u65b0\u7684\u8282\u70b9\uff0c\u5e76\u5c06\u5176\u63d2\u5165\u5230 CLH \u961f\u5217\u7684\u5c3e\u90e8\uff0c\u7136\u540e\u6210\u4e3a tail \u6307\u9488\u6240\u6307\u5411\u7684\u8282\u70b9\u3002\u8fd9\u6837\uff0ctail \u6307\u9488\u7684\u4f5c\u7528\u662f\u6807\u8bb0\u5f53\u524d CLH \u961f\u5217\u4e2d\u6700\u540e\u4e00\u4e2a\u7b49\u5f85\u83b7\u53d6\u9501\u7684\u7ebf\u7a0b\u3002<\/li>\n<\/ol>\n<p>\u901a\u8fc7 head \u6307\u9488\u548c tail \u6307\u9488\uff0cCLH \u961f\u5217\u80fd\u591f\u7ef4\u62a4\u4e00\u79cd\u6709\u5e8f\u7684\u7b49\u5f85\u961f\u5217\u7ed3\u6784\uff0c\u4fdd\u8bc1\u7ebf\u7a0b\u83b7\u53d6\u9501\u7684\u987a\u5e8f\u548c\u4e92\u65a5\u8bbf\u95ee\u7684\u6b63\u786e\u6027\u3002\u5f53\u4e00\u4e2a\u7ebf\u7a0b\u91ca\u653e\u9501\u65f6\uff0c\u5b83\u4f1a\u4fee\u6539\u5f53\u524d\u8282\u70b9\u7684\u72b6\u6001\uff0c\u5e76\u5524\u9192\u540e\u7ee7\u8282\u70b9\u4e0a\u7684\u7ebf\u7a0b\uff0c\u8ba9\u540e\u7eed\u7684\u7ebf\u7a0b\u80fd\u591f\u53ca\u65f6\u611f\u77e5\u9501\u7684\u91ca\u653e\uff0c\u5e76\u4e89\u593a\u83b7\u53d6\u9501\u7684\u673a\u4f1a\u3002<\/p>\n<h3>1.2 \u7ebf\u7a0b\u540c\u6b65<\/h3>\n<p>\u5bf9\u4e8eAQS\u6765\u8bf4\uff0c\u7ebf\u7a0b\u540c\u6b65\u7684\u5173\u952e\u662f\u5bf9\u72b6\u6001\u503cstate\u8fdb\u884c\u64cd\u4f5c\u3002state\u4e3a0\u65f6\u8868\u793a\u6ca1\u6709\u7ebf\u7a0b\u6301\u6709\u9501\uff0c\u5927\u4e8e0\u65f6\u8868\u793a\u6709\u7ebf\u7a0b\u6301\u6709\u9501\u3002\u6839\u636estate\u662f\u5426\u5c5e\u4e8e\u4e00\u4e2a\u7ebf\u7a0b\uff0c\u64cd\u4f5cstate\u7684\u65b9\u5f0f\u5206\u4e3a\u72ec\u5360\u65b9\u5f0f\u548c\u5171\u4eab\u65b9\u5f0f\u3002<\/p>\n<p>\u5728\u72ec\u5360\u65b9\u5f0f\u4e0b\u83b7\u53d6\u548c\u91ca\u653e\u8d44\u6e90\u4f7f\u7528\u7684\u65b9\u6cd5\u4e3a\uff1a<\/p>\n<ul>\n<li>void acquire\uff08int arg\uff09<\/li>\n<li>void acquireInterruptibly\uff08int arg\uff09<\/li>\n<li>boolean release\uff08int arg\uff09<\/li>\n<\/ul>\n<p>\u4f7f\u7528\u72ec\u5360\u65b9\u5f0f\u83b7\u53d6\u7684\u8d44\u6e90\u662f\u4e0e\u5177\u4f53\u7ebf\u7a0b\u7ed1\u5b9a\u7684\uff0c\u5c31\u662f\u8bf4\u5982\u679c\u4e00\u4e2a\u7ebf\u7a0b\u83b7\u53d6\u5230\u4e86\u8d44\u6e90\uff0c\u5c31\u4f1a\u6807\u8bb0\u662f\u8fd9\u4e2a\u7ebf\u7a0b\u83b7\u53d6\u5230\u4e86\uff0c\u5176\u4ed6\u7ebf\u7a0b\u518d\u5c1d\u8bd5\u64cd\u4f5cstate\u83b7\u53d6\u8d44\u6e90\u65f6\u4f1a\u53d1\u73b0\u5f53\u524d\u8be5\u8d44\u6e90\u4e0d\u662f\u81ea\u5df1\u6301\u6709\u7684\uff0c\u5c31\u4f1a\u5728\u83b7\u53d6\u5931\u8d25\u540e\u88ab\u963b\u585e\u3002<\/p>\n<p>\u5728\u5171\u4eab\u65b9\u5f0f\u4e0b\u83b7\u53d6\u548c\u91ca\u653e\u8d44\u6e90\u7684\u65b9\u6cd5\u4e3a\uff1a<\/p>\n<ul>\n<li>void acquireShared\uff08int arg\uff09<\/li>\n<li>voidacquireSharedInterruptibly\uff08int arg\uff09<\/li>\n<li>boolean releaseShared\uff08int arg\uff09\u3002<\/li>\n<\/ul>\n<p>\u5bf9\u5e94\u5171\u4eab\u65b9\u5f0f\u7684\u8d44\u6e90\u4e0e\u5177\u4f53\u7ebf\u7a0b\u662f\u4e0d\u76f8\u5173\u7684\uff0c\u5f53\u591a\u4e2a\u7ebf\u7a0b\u53bb\u8bf7\u6c42\u8d44\u6e90\u65f6\u901a\u8fc7CAS\u65b9\u5f0f\u7ade\u4e89\u83b7\u53d6\u8d44\u6e90\uff0c\u5f53\u4e00\u4e2a\u7ebf\u7a0b\u83b7\u53d6\u5230\u4e86\u8d44\u6e90\u540e\uff0c\u53e6\u5916\u4e00\u4e2a\u7ebf\u7a0b\u518d\u6b21\u53bb\u83b7\u53d6\u65f6\u5982\u679c\u5f53\u524d\u8d44\u6e90\u8fd8\u80fd\u6ee1\u8db3\u5b83\u7684\u9700\u8981\uff0c\u5219\u5f53\u524d\u7ebf\u7a0b\u53ea\u9700\u8981\u4f7f\u7528CAS\u65b9\u5f0f\u8fdb\u884c\u83b7\u53d6\u5373\u53ef\u3002<\/p>\n<h2>\u4e8c\u3001\u8d44\u6e90\u83b7\u53d6\u4e0e\u91ca\u653e<\/h2>\n<h3>2.1 \u72ec\u5360\u5f0f<\/h3>\n<ol>\n<li>\n<p>\u5f53\u4e00\u4e2a\u7ebf\u7a0b\u8c03\u7528acquire\uff08int arg\uff09\u65b9\u6cd5\u83b7\u53d6\u72ec\u5360\u8d44\u6e90\u65f6\uff0c\u4f1a\u9996\u5148\u4f7f\u7528tryAcquire\u65b9\u6cd5\u5c1d\u8bd5\u83b7\u53d6\u8d44\u6e90\uff0c\u5177\u4f53\u662f\u8bbe\u7f6e\u72b6\u6001\u53d8\u91cfstate\u7684\u503c\uff0c\u6210\u529f\u5219\u76f4\u63a5\u8fd4\u56de\uff0c\u5931\u8d25\u5219\u5c06\u5f53\u524d\u7ebf\u7a0b\u5c01\u88c5\u4e3a\u7c7b\u578b\u4e3aNode.EXCLUSIVE\u7684Node\u8282\u70b9\u540e\u63d2\u5165\u5230AQS\u963b\u585e\u961f\u5217\u7684\u5c3e\u90e8\uff0c\u5e76\u8c03\u7528LockSupport.park\uff08this\uff09\u65b9\u6cd5\u6302\u8d77\u81ea\u5df1\u3002<\/p>\n<pre><code class=\"java\">    public final void acquire(int arg) {\n      if (! tryAcquire(arg) &amp;&amp;\n          acquireQueued(addWaiter(Node.EXCLUSIVE), arg))\n          selfInterrupt();\n   }<\/code><\/pre>\n<\/li>\n<\/ol>\n<p>&lt;!&#8212;-&gt;<\/p>\n<ol start=\"2\">\n<li>\n<p>\u5f53\u4e00\u4e2a\u7ebf\u7a0b\u8c03\u7528release\uff08int arg\uff09\u65b9\u6cd5\u65f6\u4f1a\u5c1d\u8bd5\u4f7f\u7528tryRelease\u64cd\u4f5c\u91ca\u653e\u8d44\u6e90\uff0c\u8fd9\u91cc\u662f\u8bbe\u7f6e\u72b6\u6001\u53d8\u91cfstate\u7684\u503c\uff0c\u7136\u540e\u8c03\u7528LockSupport.unpark\uff08thread\uff09\u65b9\u6cd5\u6fc0\u6d3bAQS\u961f\u5217\u91cc\u9762\u88ab\u963b\u585e\u7684\u4e00\u4e2a\u7ebf\u7a0b\uff08thread\uff09\u3002\u88ab\u6fc0\u6d3b\u7684\u7ebf\u7a0b\u5219\u4f7f\u7528tryAcquire\u5c1d\u8bd5\uff0c\u770b\u5f53\u524d\u72b6\u6001\u53d8\u91cfstate\u7684\u503c\u662f\u5426\u80fd\u6ee1\u8db3\u81ea\u5df1\u7684\u9700\u8981\uff0c\u6ee1\u8db3\u5219\u8be5\u7ebf\u7a0b\u88ab\u6fc0\u6d3b\uff0c\u7136\u540e\u7ee7\u7eed\u5411\u4e0b\u8fd0\u884c\uff0c\u5426\u5219\u8fd8\u662f\u4f1a\u88ab\u653e\u5165AQS\u961f\u5217\u5e76\u88ab\u6302\u8d77\u3002<\/p>\n<pre><code class=\"java\">    public final boolean release(int arg) {\n        if (tryRelease(arg)) {\n            Node h = head;\n            if (h ! = null &amp;&amp; h.waitStatus ! = 0)\n                unparkSuccessor(h);\n            return true;\n        }\n        return false;\n    }<\/code><\/pre>\n<\/li>\n<\/ol>\n<h3>2.2 \u5171\u4eab\u5f0f<\/h3>\n<ol>\n<li>\n<p>\u5f53\u7ebf\u7a0b\u8c03\u7528acquireShared\uff08int arg\uff09\u83b7\u53d6\u5171\u4eab\u8d44\u6e90\u65f6\uff0c\u4f1a\u9996\u5148\u4f7f\u7528tryAcquireShared\u5c1d\u8bd5\u83b7\u53d6\u8d44\u6e90\uff0c\u5177\u4f53\u662f\u8bbe\u7f6e\u72b6\u6001\u53d8\u91cfstate\u7684\u503c\uff0c\u6210\u529f\u5219\u76f4\u63a5\u8fd4\u56de\uff0c\u5931\u8d25\u5219\u5c06\u5f53\u524d\u7ebf\u7a0b\u5c01\u88c5\u4e3a\u7c7b\u578b\u4e3aNode.SHARED\u7684Node\u8282\u70b9\u540e\u63d2\u5165\u5230AQS\u963b\u585e\u961f\u5217\u7684\u5c3e\u90e8\uff0c\u5e76\u4f7f\u7528LockSupport.park\uff08this\uff09\u65b9\u6cd5\u6302\u8d77\u81ea\u5df1\u3002<\/p>\n<pre><code class=\"java\">    public final void acquireShared(int arg) {\n        if (tryAcquireShared(arg) &lt; 0)\n            doAcquireShared(arg);\n    }<\/code><\/pre>\n<\/li>\n<\/ol>\n<p>&lt;!&#8212;-&gt;<\/p>\n<ol start=\"2\">\n<li>\n<p>\u5f53\u4e00\u4e2a\u7ebf\u7a0b\u8c03\u7528releaseShared\uff08int arg\uff09\u65f6\u4f1a\u5c1d\u8bd5\u4f7f\u7528tryReleaseShared\u64cd\u4f5c\u91ca\u653e\u8d44\u6e90\uff0c\u8fd9\u91cc\u662f\u8bbe\u7f6e\u72b6\u6001\u53d8\u91cfstate\u7684\u503c\uff0c\u7136\u540e\u4f7f\u7528LockSupport.unpark\uff08thread\uff09\u6fc0\u6d3bAQS\u961f\u5217\u91cc\u9762\u88ab\u963b\u585e\u7684\u4e00\u4e2a\u7ebf\u7a0b\uff08thread\uff09\u3002\u88ab\u6fc0\u6d3b\u7684\u7ebf\u7a0b\u5219\u4f7f\u7528tryReleaseShared\u67e5\u770b\u5f53\u524d\u72b6\u6001\u53d8\u91cfstate\u7684\u503c\u662f\u5426\u80fd\u6ee1\u8db3\u81ea\u5df1\u7684\u9700\u8981\uff0c\u6ee1\u8db3\u5219\u8be5\u7ebf\u7a0b\u88ab\u6fc0\u6d3b\uff0c\u7136\u540e\u7ee7\u7eed\u5411\u4e0b\u8fd0\u884c\uff0c\u5426\u5219\u8fd8\u662f\u4f1a\u88ab\u653e\u5165AQS\u961f\u5217\u5e76\u88ab\u6302\u8d77\u3002<\/p>\n<pre><code class=\"java\">    public final boolean releaseShared(int arg) {\n          if (tryReleaseShared(arg)) {\n              doReleaseShared();\n              return true;\n          }\n          return false;\n      }<\/code><\/pre>\n<\/li>\n<\/ol>\n<h2>\u4e09\u3001\u57fa\u4e8eAQS\u5b9e\u73b0\u81ea\u5b9a\u4e49\u540c\u6b65\u5668<\/h2>\n<p>\u57fa\u4e8eAQS\u5b9e\u73b0\u4e00\u4e2a\u4e0d\u53ef\u91cd\u5165\u7684\u72ec\u5360\u9501\uff0c\u81ea\u5b9a\u4e49AQS\u9700\u8981\u91cd\u5199\u4e00\u7cfb\u5217\u51fd\u6570\uff0c\u8fd8\u9700\u8981\u5b9a\u4e49\u539f\u5b50\u53d8\u91cfstate\u7684\u542b\u4e49\u3002\u8fd9\u91cc\u5b9a\u4e49\uff0cstate\u4e3a0\u8868\u793a\u76ee\u524d\u9501\u6ca1\u6709\u88ab\u7ebf\u7a0b\u6301\u6709\uff0cstate\u4e3a1\u8868\u793a\u9501\u5df2\u7ecf\u88ab\u67d0\u4e00\u4e2a\u7ebf\u7a0b\u6301\u6709\uff0c\u7531\u4e8e\u662f\u4e0d\u53ef\u91cd\u5165\u9501\uff0c\u6240\u4ee5\u4e0d\u9700\u8981\u8bb0\u5f55\u6301\u6709\u9501\u7684\u7ebf\u7a0b\u83b7\u53d6\u9501\u7684\u6b21\u6570\u3002<\/p>\n<pre><code class=\"java\">package top.emanjusaka;\n\nimport java.io.Serializable;\nimport java.util.concurrent.TimeUnit;\nimport java.util.concurrent.locks.AbstractQueuedSynchronizer;\nimport java.util.concurrent.locks.Condition;\nimport java.util.concurrent.locks.Lock;\n\npublic class UnReentrantLock implements Lock, Serializable {\n    \/\/ \u501f\u52a9 AbstractQueuedSynchronizer \u5b9e\u73b0\n    private static class Sync extends AbstractQueuedSynchronizer {\n        \/\/ \u67e5\u770b\u662f\u5426\u6709\u7ebf\u7a0b\u6301\u6709\u9501\n        protected boolean isHeldExclusively() {\n            return getState() == 1;\n        }\n        \/\/ \u5c1d\u8bd5\u83b7\u53d6\u9501\n        public boolean tryAcquire(int acquires) {\n            assert acquires == 1;\n            \/\/ \u4f7f\u7528CAS \u8bbe\u7f6estate\n            if (compareAndSetState(0, 1)) {\n                \/\/ \u5982\u679c CAS \u64cd\u4f5c\u6210\u529f\uff0c\u8868\u793a\u6210\u529f\u83b7\u5f97\u4e86\u9501\u3002\u8fd9\u65f6\uff0c\u901a\u8fc7 setExclusiveOwnerThread \u65b9\u6cd5\u5c06\u5f53\u524d\u7ebf\u7a0b\u8bbe\u7f6e\u4e3a\u72ec\u5360\u9501\u7684\u62e5\u6709\u8005\n                setExclusiveOwnerThread(Thread.currentThread());\n                return true;\n            }\n            \/\/ \u5982\u679c CAS \u64cd\u4f5c\u5931\u8d25\uff0c\u5373\u65e0\u6cd5\u5c06 state \u7684\u503c\u4ece 0 \u8bbe\u7f6e\u4e3a 1\uff0c\u8868\u793a\u9501\u5df2\u88ab\u5176\u4ed6\u7ebf\u7a0b\u5360\u7528\uff0c\u65e0\u6cd5\u83b7\u53d6\u9501\uff0c\u4e8e\u662f\u8fd4\u56de false\u3002\n            return false;\n        }\n        \/\/ \u5c1d\u8bd5\u91ca\u653e\u9501\n        protected boolean tryRelease(int releases) {\n            assert releases == 1;\n            if (getState() == 0)\n                throw new IllegalMonitorStateException();\n            \/\/ \u91ca\u653e\u6210\u529f\uff0c\u5c06\u72ec\u5360\u9501\u7684\u62e5\u6709\u8005\u8bbe\u4e3anull\n            setExclusiveOwnerThread(null);\n            \/\/ \u5c06state\u7684\u503c\u8bbe\u4e3a0\n            setState(0);\n            return true;\n        }\n\n        Condition newCondition() {\n            return new ConditionObject();\n        }\n    }\n\n    private final Sync sync = new Sync();\n\n    @Override\n    public void lock() {\n        sync.acquire(1);\n    }\n\n    @Override\n    public boolean tryLock() {\n        return sync.tryAcquire(1);\n    }\n\n    @Override\n    public void unlock() {\n        sync.release(1);\n    }\n\n    @Override\n    public Condition newCondition() {\n        return sync.newCondition();\n    }\n\n    public boolean isLocked() {\n        return sync.isHeldExclusively();\n    }\n\n    public void lockInterruptibly() throws InterruptedException {\n        sync.acquireInterruptibly(1);\n    }\n\n    public boolean tryLock(long timeout, TimeUnit unit) throws InterruptedException {\n        return sync.tryAcquireSharedNanos(1, unit.toNanos(timeout));\n    }\n\n}<\/code><\/pre>\n<p>\u5728\u91ca\u653e\u9501\u65f6\u5e76\u6ca1\u6709\u4f7f\u7528 CAS\uff08Compare and Swap\uff09\u64cd\u4f5c\uff0c\u800c\u662f\u76f4\u63a5\u4f7f\u7528\u4e86\u00a0setState\u200b \u65b9\u6cd5\u6765\u5c06\u00a0state\u200b \u7684\u503c\u8bbe\u7f6e\u4e3a 0\u3002<\/p>\n<p>\u8fd9\u662f\u56e0\u4e3a\u5728\u91ca\u653e\u9501\u7684\u8fc7\u7a0b\u4e2d\uff0c\u5e76\u4e0d\u9700\u8981\u6d89\u53ca\u5230\u591a\u7ebf\u7a0b\u5e76\u53d1\u7684\u95ee\u9898\u3002\u53ea\u6709\u6301\u6709\u9501\u7684\u7ebf\u7a0b\u624d\u80fd\u591f\u91ca\u653e\u9501\uff0c\u5176\u4ed6\u7ebf\u7a0b\u65e0\u6cd5\u5bf9\u9501\u8fdb\u884c\u64cd\u4f5c\u3002\u56e0\u6b64\uff0c\u4e0d\u9700\u8981\u4f7f\u7528 CAS \u6765\u8fdb\u884c\u539f\u5b50\u6027\u7684\u72b6\u6001\u66f4\u65b0\u3002<\/p>\n<p>\u5728\u8fd9\u79cd\u60c5\u51b5\u4e0b\uff0c\u53ef\u4ee5\u76f4\u63a5\u4f7f\u7528\u666e\u901a\u7684\u65b9\u6cd5\u6765\u8bbe\u7f6e\u00a0state\u200b \u7684\u503c\u4e3a 0\uff0c\u5c06\u72ec\u5360\u9501\u7684\u62e5\u6709\u8005\u8bbe\u4e3a null\u3002\u56e0\u4e3a\u53ea\u6709\u4e00\u4e2a\u7ebf\u7a0b\u53ef\u4ee5\u64cd\u4f5c\u8fd9\u4e2a\u9501\uff0c\u4e0d\u5b58\u5728\u5e76\u53d1\u7ade\u4e89\u7684\u60c5\u51b5\uff0c\u4e5f\u5c31\u4e0d\u9700\u8981\u4f7f\u7528 CAS \u6765\u4fdd\u8bc1\u539f\u5b50\u6027\u3002<\/p>\n<p>\u9700\u8981\u6ce8\u610f\u7684\u662f\uff0c\u5f53\u8c03\u7528\u00a0tryRelease\u200b \u65b9\u6cd5\u65f6\uff0c\u5e94\u8be5\u4fdd\u8bc1\u5f53\u524d\u7ebf\u7a0b\u662f\u6301\u6709\u9501\u7684\u7ebf\u7a0b\uff0c\u5426\u5219\u4f1a\u629b\u51fa\u00a0IllegalMonitorStateException\u200b \u5f02\u5e38\u3002\u8fd9\u662f\u4e3a\u4e86\u786e\u4fdd\u53ea\u6709\u62e5\u6709\u9501\u7684\u7ebf\u7a0b\u624d\u80fd\u91ca\u653e\u9501\uff0c\u9632\u6b62\u8bef\u91ca\u653e\u5176\u4ed6\u7ebf\u7a0b\u7684\u9501\u3002<\/p>\n<h2>\u56db\u3001\u53c2\u8003\u8d44\u6599<\/h2>\n<ol>\n<li>\u300a\u5e76\u53d1\u7f16\u7a0b\u4e4b\u7f8e\u300b<\/li>\n<li>\u200bAbstractQueuedSynchronizer\u200b\u200b\u62bd\u8c61\u7c7b\u7684\u6e90\u7801<\/li>\n<\/ol>\n<blockquote><p>\u672c\u6587\u539f\u521b\uff0c\u624d\u758f\u5b66\u6d45\uff0c\u5982\u6709\u7eb0\u6f0f\uff0c\u6b22\u8fce\u6307\u6b63\u3002\u5c0a\u8d35\u7684\u670b\u53cb\uff0c\u5982\u679c\u672c\u6587\u5bf9\u60a8\u6709\u6240\u5e2e\u52a9\uff0c\u6b22\u8fce\u70b9\u8d5e\uff0c\u5e76\u671f\u5f85\u60a8\u7684\u53cd\u9988\uff0c\u4ee5\u4fbf\u4e8e\u4e0d\u65ad\u4f18\u5316\u3002<br \/>\u539f\u6587\u5730\u5740\uff1a\u00a0<a target=\"_blank\" href=\"https:\/\/link.segmentfault.com\/?enc=cU%2FQarP5kaOfny1EKU3Ybg%3D%3D.EcdcW1bdu0oo3lUm6w8p75bHi03tcHX78yM9VLg9Mhedt880ZolEw3e1wnjLf2Vf\" rel=\"noopener noreferrer\">https:\/\/www.emanjusaka.top\/archives\/8<\/a><br \/>\u5fae\u4fe1\u516c\u4f17\u53f7\uff1aemanjusaka\u7684\u7f16\u7a0b\u6808<\/p><\/blockquote>\n<p><a href=\"https:\/\/segmentfault.com\/a\/1190000044256517\">https:\/\/segmentfault.com\/a\/1190000044256517<\/a><\/p>\n","protected":false},"excerpt":{"rendered":"<p>by\u00a0emanjusaka from\u00a0https:\/\/www.emanjusaka.top\/archives\/ [&hellip;]<\/p>\n","protected":false},"author":1,"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-10008331","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\/10008331","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\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/itmax.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=10008331"}],"version-history":[{"count":0,"href":"https:\/\/itmax.cn\/index.php?rest_route=\/wp\/v2\/posts\/10008331\/revisions"}],"wp:attachment":[{"href":"https:\/\/itmax.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=10008331"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/itmax.cn\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=10008331"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/itmax.cn\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=10008331"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}