{"id":650,"date":"2013-12-19T16:58:21","date_gmt":"2013-12-19T08:58:21","guid":{"rendered":"http:\/\/coderbee.net\/?p=650"},"modified":"2013-12-23T21:43:39","modified_gmt":"2013-12-23T13:43:39","slug":"java-%e5%86%85%e5%ad%98%e6%a8%a1%e5%9e%8b-jmm","status":"publish","type":"post","link":"https:\/\/coderbee.net\/index.php\/concurrent\/20131219\/650","title":{"rendered":"Java \u5185\u5b58\u6a21\u578b JMM"},"content":{"rendered":"<p>JMM\uff0cJava Memory Model\uff0cJava \u5185\u5b58\u6a21\u578b\u3002<\/p>\n<h2>\u4ec0\u4e48\u662f\u5185\u5b58\u6a21\u578b\uff0c\u8981\u4ed6\u4f55\u7528\uff1f<\/h2>\n<p>\u5047\u5b9a\u4e00\u4e2a\u7ebf\u7a0b\u4e3a\u53d8\u91cfvar\u8d4b\u503c\uff1a<code>var = 3;<\/code>\uff0c\u5185\u5b58\u6a21\u578b\u8981\u56de\u7b54\u7684\u95ee\u9898\u662f\uff1a\u5728\u4ec0\u4e48\u6761\u4ef6\u4e0b\uff0c\u8bfb\u53d6\u53d8\u91cfvar\u7684\u7ebf\u7a0b\u53ef\u4ee5\u770b\u5230<code>3<\/code>\u8fd9\u4e2a\u503c\uff1f<\/p>\n<p>\u5982\u679c\u7f3a\u5c11\u4e86\u540c\u6b65\uff0c\u7ebf\u7a0b\u53ef\u80fd\u65e0\u6cd5\u770b\u5230\u5176\u4ed6\u7ebf\u7a0b\u64cd\u4f5c\u7684\u7ed3\u679c\u3002\u5bfc\u81f4\u8fd9\u79cd\u60c5\u51b5\u7684\u539f\u56e0\u53ef\u4ee5\u6709\uff1a\u7f16\u8bd1\u5668\u751f\u6210\u6307\u4ee4\u7684\u6b21\u5e8f\u53ef\u4ee5\u4e0d\u540c\u4e8e\u6e90\u4ee3\u7801\u7684\u201c\u663e\u7136\u201d\u7248\u672c\uff0c\u7f16\u8bd1\u5668\u8fd8\u4f1a\u628a\u53d8\u91cf\u5b58\u50a8\u5728\u5bc4\u5b58\u5668\u800c\u4e0d\u662f\u5185\u5b58\u4e2d\uff1b\u5904\u7406\u5668\u53ef\u4ee5\u4e71\u5e8f\u6216\u5e76\u884c\u6267\u884c\u6307\u4ee4\uff1b\u7f13\u5b58\u4f1a\u6539\u53d8\u5199\u5165\u63d0\u4ea4\u5230\u4e3b\u5b58\u5f97\u5230\u53d8\u91cf\u7684\u6b21\u5e8f\uff1b\u5b58\u50a8\u5728\u5904\u7406\u5668\u672c\u5730\u7f13\u5b58\u4e2d\u7684\u53d8\u91cf\u5bf9\u5176\u4ed6\u5904\u7406\u5668\u4e0d\u53ef\u89c1 \u7b49\u7b49\u3002<\/p>\n<h3>\u6570\u636e\u4f9d\u8d56\u6027<\/h3>\n<p>\u5982\u679c\u4e24\u4e2a\u64cd\u4f5c\u8bbf\u95ee\u540c\u4e00\u4e2a\u53d8\u91cf\uff0c\u4e14\u8fd9\u4e24\u4e2a\u64cd\u4f5c\u4e2d\u6709\u4e00\u4e2a\u4e3a\u5199\u64cd\u4f5c\uff0c\u6b64\u65f6\u8fd9\u4e24\u4e2a\u64cd\u4f5c\u4e4b\u95f4\u5c31\u5b58\u5728\u6570\u636e\u4f9d\u8d56\u6027\u3002\u6570\u636e\u4f9d\u8d56\u5206\u4e0b\u5217\u4e09\u79cd\u7c7b\u578b\uff1a<\/p>\n<pre>\n\u540d\u79f0\u3000\u3000\u3000\u4ee3\u7801\u793a\u4f8b\u3000\u3000\u3000\u3000\u3000\u8bf4\u660e\n\u5199\u540e\u8bfb\u3000\u3000a = 1;b = a;\u3000\u3000\u3000\u5199\u4e00\u4e2a\u53d8\u91cf\u4e4b\u540e\uff0c\u518d\u8bfb\u8fd9\u4e2a\u4f4d\u7f6e\u3002\n\u5199\u540e\u5199\u3000\u3000a = 1;a = 2;\u3000\u3000\u3000\u5199\u4e00\u4e2a\u53d8\u91cf\u4e4b\u540e\uff0c\u518d\u5199\u8fd9\u4e2a\u53d8\u91cf\u3002\n\u8bfb\u540e\u5199\u3000\u3000a = b;b = 1;\u3000\u3000\u3000\u8bfb\u4e00\u4e2a\u53d8\u91cf\u4e4b\u540e\uff0c\u518d\u5199\u8fd9\u4e2a\u53d8\u91cf\u3002\n<\/pre>\n<p>\u4e0a\u9762\u4e09\u79cd\u60c5\u51b5\uff0c\u53ea\u8981\u91cd\u6392\u5e8f\u4e24\u4e2a\u64cd\u4f5c\u7684\u6267\u884c\u987a\u5e8f\uff0c\u7a0b\u5e8f\u7684\u6267\u884c\u7ed3\u679c\u5c06\u4f1a\u88ab\u6539\u53d8\u3002<\/p>\n<p>\u7f16\u8bd1\u5668\u548c\u5904\u7406\u5668\u5728\u91cd\u6392\u5e8f\u65f6\uff0c\u4f1a\u9075\u5b88\u6570\u636e\u4f9d\u8d56\u6027\uff0c\u7f16\u8bd1\u5668\u548c\u5904\u7406\u5668\u4e0d\u4f1a\u6539\u53d8\u5b58\u5728\u6570\u636e\u4f9d\u8d56\u5173\u7cfb\u7684\u4e24\u4e2a\u64cd\u4f5c\u7684\u6267\u884c\u987a\u5e8f\u3002<\/p>\n<h3>as-if-serial\u8bed\u4e49<\/h3>\n<p>as-if-serial\u8bed\u4e49\u7684\u610f\u601d\u6307\uff1a\u4e0d\u7ba1\u600e\u4e48\u91cd\u6392\u5e8f\uff0c\uff08\u5355\u7ebf\u7a0b\uff09\u7a0b\u5e8f\u7684\u6267\u884c\u7ed3\u679c\u4e0d\u80fd\u88ab\u6539\u53d8\u3002\u7f16\u8bd1\u5668\u3001runtime \u548c\u5904\u7406\u5668\u90fd\u5fc5\u987b\u9075\u5b88as-if-serial\u8bed\u4e49\u3002<\/p>\n<h3>\u6570\u636e\u7ade\u4e89<\/h3>\n<p>\u5f53\u7a0b\u5e8f\u672a\u6b63\u786e\u540c\u6b65\u65f6\uff0c\u5c31\u4f1a\u5b58\u5728\u6570\u636e\u7ade\u4e89\u3002java\u5185\u5b58\u6a21\u578b\u89c4\u8303\u5bf9\u6570\u636e\u7ade\u4e89\u7684\u5b9a\u4e49\u4e3a\uff1a\u5728\u4e00\u4e2a\u7ebf\u7a0b\u4e2d\u5199\u4e00\u4e2a\u53d8\u91cf\uff0c\u5728\u53e6\u4e00\u4e2a\u7ebf\u7a0b\u8bfb\u540c\u4e00\u4e2a\u53d8\u91cf\uff0c\u800c\u4e14\u5199\u548c\u8bfb\u6ca1\u6709\u901a\u8fc7\u540c\u6b65\u6765\u6392\u5e8f\u3002<\/p>\n<h3>\u987a\u5e8f\u4e00\u81f4\u6027\u6a21\u578b<\/h3>\n<p>\u64cd\u4f5c\u6267\u884c\u7684\u987a\u5e8f\u662f\u552f\u4e00\u7684\uff0c\u5c31\u662f\u5b83\u4eec\u51fa\u73b0\u5728\u7a0b\u5e8f\u4e2d\u7684\u987a\u5e8f\uff0c\u8fd9\u4e0e\u6267\u884c\u5b83\u4eec\u7684\u5904\u7406\u5668\u65e0\u5173\uff1b\u53d8\u91cf\u6bcf\u4e00\u6b21\u8bfb\u64cd\u4f5c\uff0c\u90fd\u80fd\u5f97\u5230\u6267\u884c\u5e8f\u5217\u4e0a\u8fd9\u4e2a\u53d8\u91cf\u6700\u65b0\u7684\u5199\u5165\u503c\uff0c\u65e0\u8bba\u8fd9\u662f\u54ea\u4e2a\u5904\u7406\u5668\u5199\u5165\u7684\u3002\u8fd9\u4e2a\u662f\u4e00\u4e2a\u7406\u60f3\u7684\u6a21\u578b\uff0cJMM\u662f\u4e0d\u652f\u6301\u7684\u3002<\/p>\n<p>Java \u8bed\u8a00\u89c4\u8303\u89c4\u5b9a\u4e86 JVM \u8981\u7ef4\u62a4<strong>\u5185\u90e8\u7ebf\u7a0b\u7c7b\u4f3c\u987a\u5e8f\u8bed\u610f\uff08within-thread as-if-serial semantics\uff09<\/strong>\uff1a\u53ea\u8981\u7a0b\u5e8f\u7684\u6700\u7ec8\u7ed3\u679c\u7b49\u540c\u4e8e\u5b83\u5728\u4e25\u683c\u7684\u987a\u5e8f\u73af\u5883\u4e2d\u6267\u884c\u7684\u7ed3\u679c\uff0c\u90a3\u4e48\u4e0a\u8ff0\u6240\u6709\u7684\u884c\u4e3a\u90fd\u662f\u5141\u8bb8\u7684\u3002<\/p>\n<p><strong>JMM \u89c4\u5b9a\u4e86 JVM \u7684\u4e00\u79cd\u6700\u5c0f\u4fdd\u8bc1\uff1a\u4ec0\u4e48\u65f6\u5019\u5199\u5165\u4e00\u4e2a\u53d8\u91cf\u4f1a\u5bf9\u5176\u4ed6\u7ebf\u7a0b\u53ef\u89c1\u3002<\/strong><br \/>\n<!--more--><\/p>\n<h2>Java \u5185\u5b58\u6a21\u578b<\/h2>\n<p>Java \u5185\u5b58\u6a21\u578b\u7684\u5b9a\u4e49\u662f\u901a\u8fc7\u52a8\u4f5c\uff08actions\uff09\u7684\u5f62\u5f0f\u8fdb\u884c\u63cf\u8ff0\u7684\uff0c\u6240\u8c13\u52a8\u4f5c\uff0c\u5305\u62ec\u53d8\u91cf\u8bfb\u548c\u5199\u3001\u76d1\u89c6\u5668\u52a0\u9501\u548c\u91ca\u653e\u9501\u3001\u7ebf\u7a0b\u7684\u542f\u52a8\u548c\u62fc\u63a5\uff08join\uff09\u3002<\/p>\n<p>JMM\u4e3a\u6240\u6709\u7a0b\u5e8f\u5185\u90e8\u7684\u52a8\u4f5c\u5b9a\u4e49\u4e86\u4e00\u4e2a\u53eb happens-before \u7684\u504f\u5e8f\u5173\u7cfb\uff08\u504f\u5e8f\u5173\u7cfb\u662f\u53cd\u5bf9\u79f0\u7684\u3001\u81ea\u53cd\u7684\u548c\u4f20\u9012\u7684\u5173\u7cfb\uff09\u3002\u5982\u679c\u64cd\u4f5c A \u548c B \u6ee1\u8db3 happens-before \u5173\u7cfb\uff0c\u90a3\u4e48\u6267\u884c\u52a8\u4f5c B \u7684\u7ebf\u7a0b\u5c31\u53ef\u4ee5\u770b\u5230\u52a8\u4f5c A \u7684\u7ed3\u679c\uff1b\u5982\u679c\u4e24\u4e2a\u64cd\u4f5c\u4e4b\u95f4\u6ca1\u6709 happens-before \u5173\u7cfb\uff0c\u90a3\u4e48 JVM \u5c31\u53ef\u4ee5\u5bf9\u5b83\u4eec\u968f\u610f\u5730\u91cd\u6392\u5e8f\u3002<\/p>\n<h3>happens-before\u6cd5\u5219<\/h3>\n<ul>\n<li><strong>\u7a0b\u5e8f\u6b21\u5e8f\u6cd5\u5219<\/strong>\uff1a\u7ebf\u7a0b\u4e2d\u7684\u6bcf\u4e2a\u52a8\u4f5c A \u90fd happens-before \u4e8e\u8be5\u7ebf\u7a0b\u4e2d\u7684\u6bcf\u4e00\u4e2a\u52a8\u4f5c B\uff0c\u5176\u4e2d\uff0c\u5728\u7a0b\u5e8f\u4e2d\uff0c\u6240\u6709\u7684\u52a8\u4f5c B \u90fd\u51fa\u73b0\u5728\u52a8\u4f5c A \u4e4b\u540e\u3002\uff08\u6ce8\uff1a\u6b64\u6cd5\u5219\u53ea\u662f\u8981\u6c42\u9075\u5faa  as-if-serial\u8bed\u4e49\uff09<\/p>\n<\/li>\n<li>\n<p><strong>\u76d1\u89c6\u5668\u9501\u6cd5\u5219<\/strong>\uff1a\u5bf9\u4e00\u4e2a\u76d1\u89c6\u5668\u9501\u7684\u89e3\u9501 happens-before \u4e8e\u6bcf\u4e00\u4e2a\u540e\u7eed\u5bf9\u540c\u4e00\u76d1\u89c6\u5668\u9501\u7684\u52a0\u9501\u3002\uff08\u663e\u5f0f\u9501\u7684\u52a0\u9501\u548c\u89e3\u9501\u6709\u7740\u4e0e\u5185\u7f6e\u9501\uff0c\u5373\u76d1\u89c6\u5668\u9501\u76f8\u540c\u7684\u5b58\u50a8\u8bed\u610f\u3002\uff09<\/p>\n<\/li>\n<li>\n<p><strong>volatile\u53d8\u91cf\u6cd5\u5219<\/strong>\uff1a\u5bf9 volatile \u57df\u7684\u5199\u5165\u64cd\u4f5c happens-before \u4e8e\u6bcf\u4e00\u4e2a\u540e\u7eed\u5bf9\u540c\u4e00\u57df\u7684\u8bfb\u64cd\u4f5c\u3002\uff08\u539f\u5b50\u53d8\u91cf\u7684\u8bfb\u5199\u64cd\u4f5c\u6709\u7740\u4e0e volatile \u53d8\u91cf\u76f8\u540c\u7684\u8bed\u610f\u3002\uff09\uff08volatile\u53d8\u91cf\u5177\u6709\u53ef\u89c1\u6027\u548c\u8bfb\u5199\u539f\u5b50\u6027\u3002\uff09<\/p>\n<\/li>\n<li>\n<p><strong>\u7ebf\u7a0b\u542f\u52a8\u6cd5\u5219<\/strong>\uff1a\u5728\u4e00\u4e2a\u7ebf\u7a0b\u91cc\uff0c\u5bf9 Thread.start \u7684\u8c03\u7528\u4f1a happens-before \u4e8e\u6bcf\u4e00\u4e2a\u542f\u52a8\u7ebf\u7a0b\u4e2d\u7684\u52a8\u4f5c\u3002<\/p>\n<\/li>\n<li>\n<p><strong>\u7ebf\u7a0b\u7ec8\u6b62\u6cd5\u5219<\/strong>\uff1a\u7ebf\u7a0b\u4e2d\u7684\u4efb\u4f55\u52a8\u4f5c\u90fd happens-before \u4e8e\u5176\u4ed6\u7ebf\u7a0b\u68c0\u6d4b\u5230\u8fd9\u4e2a\u7ebf\u7a0b\u5df2\u7ec8\u7ed3\uff0c\u6216\u8005\u4ece Thread.join \u65b9\u6cd5\u8c03\u7528\u4e2d\u6210\u529f\u8fd4\u56de\uff0c\u6216\u8005 Thread.isAlive \u65b9\u6cd5\u8fd4\u56defalse\u3002<\/p>\n<\/li>\n<li>\n<p><strong>\u4e2d\u65ad\u6cd5\u5219\u6cd5\u5219<\/strong>\uff1a\u4e00\u4e2a\u7ebf\u7a0b\u8c03\u7528\u53e6\u4e00\u4e2a\u7ebf\u7a0b\u7684 interrupt \u65b9\u6cd5  happens-before \u4e8e\u88ab\u4e2d\u65ad\u7ebf\u7a0b\u53d1\u73b0\u4e2d\u65ad\uff08\u901a\u8fc7\u629b\u51faInterruptedException\uff0c \u6216\u8005\u8c03\u7528 isInterrupted \u65b9\u6cd5\u548c interrupted \u65b9\u6cd5\uff09\u3002<\/p>\n<\/li>\n<li>\n<p><strong>\u7ec8\u7ed3\u6cd5\u5219<\/strong>\uff1a\u4e00\u4e2a\u5bf9\u8c61\u7684\u6784\u9020\u51fd\u6570\u7684\u7ed3\u675f  happens-before \u4e8e\u8fd9\u4e2a\u5bf9\u8c61 finalizer \u5f00\u59cb\u3002<\/p>\n<\/li>\n<li>\n<p><strong>\u4f20\u9012\u6027<\/strong>\uff1a\u5982\u679c A   happens-before \u4e8e B\uff0c\u4e14 B   happens-before \u4e8e C\uff0c\u5219 A   happens-before \u4e8e C\u3002<\/p>\n<\/li>\n<\/ul>\n<p>\u5bf9\u4e8efinal\u57df\uff0c\u7f16\u8bd1\u5668\u548c\u5904\u7406\u5668\u8981\u9075\u5b88\u4e24\u4e2a\u91cd\u6392\u5e8f\u89c4\u5219\uff1a<\/p>\n<ul>\n<li>\u5728\u6784\u9020\u51fd\u6570\u5185\u5bf9\u4e00\u4e2afinal\u57df\u7684\u5199\u5165\uff0c\u4e0e\u968f\u540e\u628a\u8fd9\u4e2a\u88ab\u6784\u9020\u5bf9\u8c61\u7684\u5f15\u7528\u8d4b\u503c\u7ed9\u4e00\u4e2a\u5f15\u7528\u53d8\u91cf\uff0c\u8fd9\u4e24\u4e2a\u64cd\u4f5c\u4e4b\u95f4\u4e0d\u80fd\u91cd\u6392\u5e8f\u3002<\/li>\n<li>\u521d\u6b21\u8bfb\u4e00\u4e2a\u5305\u542bfinal\u57df\u7684\u5bf9\u8c61\u7684\u5f15\u7528\uff0c\u4e0e\u968f\u540e\u521d\u6b21\u8bfb\u8fd9\u4e2afinal\u57df\uff0c\u8fd9\u4e24\u4e2a\u64cd\u4f5c\u4e4b\u95f4\u4e0d\u80fd\u91cd\u6392\u5e8f\u3002<\/li>\n<\/ul>\n<p><strong>\u6ce8\u610f\uff1a<\/strong><\/p>\n<ul>\n<li>\u5173\u4e8e final \u57df\u7684\u5185\u5b58\u8bed\u4e49\uff0c\u662f\u5728\u6ca1\u6709 this \u5f15\u7528\u9038\u51fa\u7684\u524d\u63d0\u4e0b\u7684\u3002<\/li>\n<li>\u5bf9\u4e8e\u4f9d\u8d56\u76d1\u89c6\u5668\u9501\u6cd5\u5219\u7684\u5185\u5b58\u53ef\u89c1\u6027\uff0c\u5bf9\u5171\u4eab\u53d8\u91cf\u53d8\u91cf\u7684\u6240\u6709\u8bbf\u95ee\u90fd\u5fc5\u987b\u5728\u540c\u6b65\u7684\u60c5\u51b5\u4e0b\u624d\u6709\u610f\u4e49\u3002<\/li>\n<\/ul>\n<p>\u5bf9\u4e8eJava\u7f16\u7a0b\u6765\u8bf4\uff0c\u9700\u8981\u5173\u6ce8\u7684\u6cd5\u5219\u6709\uff1a\u7a0b\u5e8f\u6b21\u5e8f\u6cd5\u5219\u3001\u76d1\u89c6\u5668\u9501\u6cd5\u5219\u3001volatile\u53d8\u91cf\u6cd5\u5219\uff0c\u8fd8\u6709 final \u57df\u7684\u89c4\u5219\u3002<\/p>\n<h3>final \u57df\u4e0e this \u5f15\u7528\u9038\u51fa<\/h3>\n<p>this \u5f15\u7528\u9038\u51fa\u7684\u4e3e\u4f8b\uff1a<\/p>\n<pre><code class=\"java\">public class ThisEscape {\n       private final int a; \/\/ final \u57df\n\n       public ThisEscape( int init, List&lt;Object&gt; list) {\n             \/\/ \u5bf9 final \u57df\u8d4b\u503c, JMM \u4e0d\u4fdd\u8bc1\u8fd9\u4e2a\u5199\u4e4b\u540e\u6709 store barrier\n             a = init;\n\n             \/\/ \u628a this \u6dfb\u52a0\u5230\u4e00\u4e2a\u5916\u90e8\u96c6\u5408\uff0c\u5bfc\u81f4 this \u5f15\u7528\u9038\u51fa\u3002\n             \/\/ \u5176\u4ed6\u7ebf\u7a0b\u901a\u8fc7\u8fd9\u4e2a\u9038\u51fa\u7684\u5f15\u7528\u770b\u5230\u7684 a \u53ef\u80fd\u4ecd\u7136\u662f\u672a\u521d\u59cb\u5316\u7684\u503c\u3002\n            list.add( this );\n\n             \/\/ ...  \u5176\u4ed6\u6784\u9020\u8bed\u53e5\n\n             \/\/ \u6784\u9020\u51fd\u6570\u7ed3\u675f:   store barrier; return;\n      }\n}\n<\/code><\/pre>\n<p>JMM \u5bf9 final \u57df\u7684\u4fdd\u8bc1\u53ef\u7406\u89e3\u4e3a\u5b83\u53ea\u4f1a\u5728\u6784\u9020\u51fd\u6570\u8fd4\u56de\u4e4b\u524d\u63d2\u5165\u4e00\u4e2a\u5b58\u50a8\u5c4f\u969c\uff0c\u4fdd\u8bc1\u6784\u9020\u51fd\u6570\u5185\u5bf9 final \u57df\u7684\u8d4b\u503c\u5728\u6784\u9020\u51fd\u6570\u8fd4\u56de\u4e4b\u524d\u5199\u5230\u4e3b\u5b58\u3002<\/p>\n<h3>happens-before \u4e3e\u4f8b\u8bf4\u660e<\/h3>\n<pre><code class=\"java\">public class JMM {\n       int a ;\n       int b ;\n       int multi ;\n       volatile int sum ; \/\/\n\n       public void order() {\n             int c = 12;   \/\/ 1\n             int d = 34;   \/\/ 2\n             \/\/ \u4f5c\u4e3a\u65b9\u6cd5\u5185\u7684\u5c40\u90e8\u53d8\u91cf\uff0cc\u3001d \u53ea\u80fd\u88ab\u5f53\u524d\u7ebf\u7a0b\u8bbf\u95ee\uff0c\u4e0d\u5b58\u5728\u6570\u636e\u7ade\u4e89\uff1b\n             \/\/ \u6b65\u9aa4 1 \u548c 2 \u6ca1\u6709\u6570\u636e\u4f9d\u8d56\uff0c\u4e14\u5b83\u4eec\u4e4b\u95f4\u6ca1\u6709\u9650\u5236\u91cd\u6392\u5e8f\u7684\u64cd\u4f5c\uff0c\u6240\u4ee5\u8fd9\u4e24\u6b65\u4e4b\u95f4 \u53ef\u4ee5\u81ea\u7531\u91cd\u6392\u5e8f\u3002\n\n             multi = c * d; \/\/ 3\n             \/\/ 3 \u548c \u6b65\u9aa4 1\u30012 \u4e4b\u95f4\u6709\u6570\u636e\u4f9d\u8d56\uff0c\u6240\u4ee5 3 \u548c 1\u30012 \u7ec4\u6210\u7684\u6574\u4f53\u4e4b\u95f4\u4e0d\u80fd\u91cd\u6392\u5e8f\u3002\n             \/\/ 1\u30012 \u53ef\u80fd\u91cd\u6392\u5e8f\u4e86\uff0c\u6240\u4ee5\u8bf4\u662f\u6574\u4f53\u3002\n\n             sum = c + d;  \/\/ 5\n             \/\/ insert store barrier here   !!!!!\n             \/\/ \u6b65\u9aa4 5 \u4e0e 3 \u4e4b\u95f4\u867d\u7136\u6ca1\u6709\u6570\u636e\u4f9d\u8d56\uff0c\u4f46 volatile \u7684\u8bed\u4e49\u7981\u6b62\u4e24\u8005\u4e4b\u95f4\u7684\u91cd\u6392\u5e8f\u3002\n             \/\/ \u6267\u884c\u5b8c store barrier \u4e4b\u540e\uff0c\u5176\u4ed6\u7ebf\u7a0b\u90fd\u53ef\u4ee5\u770b\u5230\u5f53\u524d\u7ebf\u7a0b\u5199\u5165 sum \u548c multi \u7684\u6700\u65b0\u503c\u3002\n\n             int doubleTemp = multi * 2;  \/\/ 5\n             \/\/ multi \u662f\u5bf9\u8c61\u7684\u5c5e\u6027\uff0c\u662f\u5171\u4eab\u53d8\u91cf\uff0c\n             \/\/ \u5982\u679c\u6709\u53e6\u4e00\u4e2a\u7ebf\u7a0b\u8fdb\u884c\u5199\u64cd\u4f5c\uff0c\u7531\u4e8e\u5bf9 multi \u7684\u8bbf\u95ee\u6ca1\u6709\u8fdb\u884c\u540c\u6b65\uff0c\u4e0e\u5f53\u524d\u7ebf\u7a0b\u7684\u8bfb\u64cd\u4f5c\u5b58\u5728\u6570\u636e\u7ade\u4e89\u3002\n             \/\/ \u6240\u4ee5\u5728\u591a\u7ebf\u7a0b\u7684\u60c5\u51b5\u4e0b\u6b65\u9aa4 5 \u7684\u6267\u884c\u7ed3\u679c\u662f\u4e0d\u786e\u5b9a\u7684\u3002\n\n             \/\/ insert load barrier here   !!!!!\n             \/\/ volatile \u53d8\u91cf\u7684\u8bfb\u64cd\u4f5c\u4e4b\u524d\u4f1a\u4f5c\u5e9f\u5f53\u524d CPU \u7684\u672c\u5730\u7f13\u5b58\uff0c\u540e\u7eed\u53d8\u91cf\u7684\u8bbf\u95ee\u9700\u8981\u91cd\u65b0\u4ece\u4e3b\u5b58\u8bfb\u53d6\u3002\n             int doubleSum = sum * 2;  \/\/ 8\n             \/\/ \u7531\u4e8e volatile \u53d8\u91cf\u4e0d\u5177\u6709\u4e92\u65a5\u6027\uff0c\u4e14\u5f53\u524d\u65b9\u6cd5\u6ca1\u6709\u4f7f\u7528\u9501\u8fdb\u884c\u540c\u6b65\uff0c\n             \/\/ \u6240\u4ee5\u6b65\u9aa4 8 \u8bfb\u5230\u7684 sum \u7684\u503c\u53ef\u80fd\u4e0d\u662f \u6b65\u9aa4 5 \u5199\u5165\u7684\u503c\uff08\u88ab\u5176\u4ed6\u7ebf\u7a0b\u4fee\u6539\u4e86\uff09\u3002\n      }\n}\n<\/code><\/pre>\n<p>\u6df1\u5165\u7406\u89e3 Java \u5185\u5b58\u6a21\u578b\u662f\u7406\u89e3 JUC \u5305\u548c\u7f16\u5199\u9ad8\u6027\u80fd\u5e76\u53d1\u7a0b\u5e8f\u7684\u57fa\u7840\u3002<\/p>\n<p>\u53ef\u4ee5\u901a\u8fc7JUC\u91cc\u540c\u6b65\u5668\u53ca\u5176\u5e94\u7528\u7684\u6e90\u7801\u5206\u6790\u53bb\u611f\u53d7\u4e0b\u5185\u5b58\u6a21\u578b\u7684\u5e94\u7528\uff1a<\/p>\n<ul>\n<li><a href=\"http:\/\/coderbee.net\/index.php\/concurrent\/20131205\/600\">JUC AQS<\/a><\/li>\n<li><a href=\"http:\/\/coderbee.net\/index.php\/concurrent\/20131209\/614\">JUC \u6e90\u7801\u5206\u6790 \u4e00 AbstractQueuedSynchronizer<\/a><\/li>\n<li><a href=\"http:\/\/coderbee.net\/index.php\/concurrent\/20131209\/618\">JUC \u6e90\u7801\u5206\u6790 \u4e8c ReentrantLock<\/a><\/li>\n<li><a href=\"http:\/\/coderbee.net\/index.php\/concurrent\/20131213\/631\">JUC \u6e90\u7801\u5206\u6790 \u4e09 AbstractQueuedSynchronizer \u5171\u4eab\u6a21\u5f0f \u4e0e CountDownLatch<\/a><\/li>\n<li><a href=\"http:\/\/coderbee.net\/index.php\/concurrent\/20131220\/653\">JUC \u6e90\u7801\u5206\u6790 \u56db wait notify notifyAll \u4e0e \u6761\u4ef6\u5bf9\u8c61<\/a><\/li>\n<\/ul>\n<h2>\u53c2\u8003\u8d44\u6599<\/h2>\n<ul>\n<li><a href=\"http:\/\/www.infoq.com\/cn\/author\/%E7%A8%8B%E6%99%93%E6%98%8E\">\u6df1\u5165\u7406\u89e3Java\u5185\u5b58\u6a21\u578b<\/a> \u5e8f\u5217\u6587\u7ae0<\/li>\n<li>\u300aJava \u5e76\u53d1\u7f16\u7a0b\u5b9e\u8df5\u300b <\/li>\n<li><a href=\"http:\/\/coderbee.net\/index.php\/concurrent\/20131211\/624\">\u5185\u5b58\u5c4f\u969c\/\u6805\u680f \uff08 Memory Barriers \/ Fences \uff09<\/a><\/li>\n<\/ul>\n<hr\/>\n<p>\u6b22\u8fce\u5173\u6ce8\u6211\u7684\u5fae\u4fe1\u516c\u4f17\u53f7: <strong>coderbee\u7b14\u8bb0<\/strong>\uff0c\u53ef\u4ee5\u66f4\u53ca\u65f6\u56de\u590d\u4f60\u7684\u8ba8\u8bba\u3002<\/p>\n<p><img loading=\"lazy\" decoding=\"async\" width=\"258\" height=\"258\" src=\"https:\/\/coderbee.net\/wp-content\/uploads\/2019\/01\/coderbee-note.jpg\" class=\"alignnone size-full wp-image-1707\"><\/p>\n","protected":false},"excerpt":{"rendered":"<p>JMM\uff0cJava Memory Model\uff0cJava \u5185\u5b58\u6a21\u578b\u3002 \u4ec0\u4e48\u662f\u5185\u5b58\u6a21\u578b &hellip; <a href=\"https:\/\/coderbee.net\/index.php\/concurrent\/20131219\/650\">\u7ee7\u7eed\u9605\u8bfb <span class=\"meta-nav\">&rarr;<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[121],"tags":[136,135,134,133,111],"_links":{"self":[{"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/posts\/650"}],"collection":[{"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/comments?post=650"}],"version-history":[{"count":5,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/posts\/650\/revisions"}],"predecessor-version":[{"id":679,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/posts\/650\/revisions\/679"}],"wp:attachment":[{"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/media?parent=650"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/categories?post=650"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/coderbee.net\/index.php\/wp-json\/wp\/v2\/tags?post=650"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}