CAS\uff1a Compare and Swap,\u7ffb\u8bd1\u6210\u6bd4\u8f83\u5e76\u4ea4\u6362\u3002
\njava.util.concurrent\u5305\u4e2d\u501f\u52a9CAS\u5b9e\u73b0\u4e86\u533a\u522b\u4e8esynchronouse\u540c\u6b65\u9501\u7684\u4e00\u79cd\u4e50\u89c2\u9501\u3002
\nCAS\u901a\u8fc7\u8c03\u7528JNI\u7684\u4ee3\u7801\u5b9e\u73b0\u7684\u3002JNI\uff1aJava Native Interface\u4e3aJAVA\u672c\u5730\u8c03\u7528\uff0c\u5141\u8bb8java \u8c03\u7528\u5176\u4ed6\u8bed\u8a00\u3002
\nCAS\u5e94\u7528<\/p>\n
CAS\u67093\u4e2a\u64cd\u4f5c\u6570\uff0c\u5185\u5b58\u503cV,\u65e7\u7684\u9884\u671f\u503cA,\u8981\u4fee\u6539\u7684\u65b0\u503cB,\u5f53\u4e14\u4ec5\u5f53\u9884\u671f\u503cA\u548c\u5185\u5b58\u503cV \u76f8\u540c\u65f6\uff0c\u5c06\u5185\u5b58\u503cV\u4fee\u6539\u4e3aB,\u5426\u5219\u4ec0\u4e48\u90fd\u4e0d\u505a
\nCAS\u7684\u7f3a\u70b9\u662f\uff1a
\nCAS\u867d\u7136\u5f88\u9ad8\u6548\u7684\u89e3\u51b3\u539f\u5b50\u64cd\u4f5c\uff0c\u4f46\u662fCAS\u4ecd\u7136\u5b58\u5728\u4e09\u5927\u95ee\u9898\uff0cABA\u95ee\u9898\uff0c\u5faa\u73af\u65f6\u95f4\u957f\u5f00\u9500\u5927 \u548c\u53ea\u80fd\u4fdd\u8bc1\u4e00\u4e2a\u5171\u4eab\u53d8\u91cf\u7684\u539f\u5b50\u64cd\u4f5c
\n1\u3001\tABA\u95ee\u9898\u3002\u56e0\u4e3aCAS\u9700\u8981\u5728\u64cd\u4f5c\u503c\u7684\u65f6\u5019\u68c0\u67e5\u4e0b\u503c\u6709\u6ca1\u6709\u53d1\u751f\u53d8\u5316\uff0c\u5982\u679c\u6ca1\u6709\u53d1\u751f\u53d8\u5316\u5219 \u66f4\u65b0\uff0c\u4f46\u662f\u5982\u679c\u4e00\u4e2a\u503c\u539f\u6765\u662fA,\u53d8\u6210\u4e86 B,\u53c8\u53d8\u6210\u4e86 A,\u90a3\u4e48\u4f7f\u7528CAS\u8fdb\u884c\u68c0\u67e5\u65f6\u4f1a\u53d1\u73b0\u5b83 \u7684\u503c\u6ca1\u6709\u53d1\u751f\u53d8\u5316\uff0c\u4f46\u662f\u5b9e\u9645\u4e0a\u5374\u53d8\u5316\u4e86\u3002ABA\u95ee\u9898\u7684\u89e3\u51b3\u601d\u8def\u5c31\u662f\u4f7f\u7528\u7248\u672c\u53f7\u3002\u5728\u53d8\u91cf\u524d\u9762 \u8ffd\u52a0\u4e0a\u7248\u672c\u53f7\uff0c\u6bcf\u6b21\u53d8\u91cf\u66f4\u65b0\u7684\u65f6\u5019\u628a\u7248\u672c\u53f7\u52a0\u4e00\uff0c\u90a3\u4e48A-B-A\u5c31\u4f1a\u53d8\u62101A-2B\u20143A\u3002
\n\u4eceJaval.5\u5f00\u59cbJDK\u7684atomic\u5305\u91cc\u63d0\u4f9b\u4e86 \u4e00\u4e2a\u7c7bAtomicStampedReference\u6765\u89e3\u51b3ABA\u95ee\u9898\u3002 \u8fd9\u4e2a\u7c7b\u7684compareAndSet\u65b9\u6cd5\u4f5c\u7528\u662f\u9996\u5148\u68c0\u67e5\u5f53\u524d\u5f15\u7528\u662f\u5426\u7b49\u4e8e\u9884\u671f\u5f15\u7528\uff0c\u5e76\u4e14\u5f53\u524d\u6807\u5fd7\u662f\u5426 \u7b49\u4e8e\u9884\u671f\u6807\u5fd7\uff0c\u5982\u679c\u5168\u90e8\u76f8\u7b49\uff0c\u5219\u4ee5\u539f\u5b50\u65b9\u5f0f\u5c06\u8be5\u5f15\u7528\u548c\u8be5\u6807\u5fd7\u7684\u503c\u8bbe\u7f6e\u4e3a\u7ed9\u5b9a\u7684\u66f4\u65b0\u503c\u3002
\n2\u3001\t\u5faa\u73af\u65f6\u95f4\u957f\u5f00\u9500\u5927\u3002\u81ea\u65cbCAS\u5982\u679c\u957f\u65f6\u95f4\u4e0d\u6210\u529f\uff0c\u4f1a\u7ed9CPU\u5e26\u6765\u975e\u5e38\u5927\u7684\u6267\u884c\u5f00\u9500\u3002\u5982\u679c JVM\u80fd\u652f\u6301\u5904\u7406\u5668\u63d0\u4f9b\u7684pause\u6307\u4ee4\u90a3\u4e48\u6548\u7387\u4f1a\u6709\u4e00\u5b9a\u7684\u63d0\u5347\uff0cpause\u6307\u4ee4\u6709\u4e24\u4e2a\u4f5c\u7528\uff0c\u7b2c\u4e00 \u5b83\u53ef\u4ee5\u5ef6\u8fdf\u6d41\u6c34\u7ebf\u6267\u884c\u6307\u4ee4(de-pipeline)\uff0c\u4f7fCPU\u4e0d\u4f1a\u6d88\u8017\u8fc7\u591a\u7684\u6267\u884c\u8d44\u6e90\uff0c\u5ef6\u8fdf\u7684\u65f6\u95f4\u53d6 \u51b3\u4e8e\u5177\u4f53\u5b9e\u73b0\u7684\u7248\u672c\uff0c\u5728\u4e00\u4e9b\u5904\u7406\u5668\u4e0a\u5ef6\u8fdf\u65f6\u95f4\u662f\u96f6\u3002\u7b2c\u4e8c\u5b83\u53ef\u4ee5\u907f\u514d\u5728\u9000\u51fa\u5faa\u73af\u7684\u65f6\u5019\u56e0\u5185\u5b58\u987a\u5e8f\u51b2\u7a81(memory order violation)\u800c\u5f15\u8d77 CPU \u6d41\u6c34\u7ebf\u88ab\u6e05\u7a7a(CPU pipeline flush), \u4ece\u800c\u63d0\u9ad8CPU\u7684\u6267\u884c\u6548\u7387\u3002
\n3\u3001\t\u53ea\u80fd\u4fdd\u8bc1\u4e00\u4e2a\u5171\u4eab\u53d8\u91cf\u7684\u539f\u5b50\u64cd\u4f5c\u3002\u5f53\u5bf9\u4e00\u4e2a\u5171\u4eab\u53d8\u91cf\u6267\u884c\u64cd\u4f5c\u65f6\uff0c\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528\u5faa\u73af CAS\u7684\u65b9\u5f0f\u6765\u4fdd\u8bc1\u539f\u5b50\u64cd\u4f5c\uff0c\u4f46\u662f\u5bf9\u591a\u4e2a\u5171\u4eab\u53d8\u91cf\u64cd\u4f5c\u65f6\uff0c\u5faa\u73afCAS\u5c31\u65e0\u6cd5\u4fdd\u8bc1\u64cd\u4f5c\u7684\u539f\u5b50\u6027, \u8fd9\u4e2a\u65f6\u5019\u5c31\u53ef\u4ee5\u7528\u9501\uff0c\u6216\u8005\u6709\u4e00\u4e2a\u53d6\u5de7\u7684\u529e\u6cd5\uff0c\u5c31\u662f\u628a\u591a\u4e2a\u5171\u4eab\u53d8\u91cf\u5408\u5e76\u6210\u4e00\u4e2a\u5171\u4eab\u53d8\u91cf\u6765\u64cd \u4f5c\u3002\u6bd4\u5982\u6709\u4e24\u4e2a\u5171\u4eab\u53d8\u91cfi=2,j=a,\u5408\u5e76\u4e00\u4e0bij=2a,\u7136\u540e\u7528CAS\u6765\u64cd\u4f5cij\u3002\u4eceJaval.5\u5f00 \u59cbJDK\u63d0\u4f9b\u4e86 AtomicReference\u7c7b\u6765\u4fdd\u8bc1\u5f15\u7528\u5bf9\u8c61\u4e4b\u95f4\u7684\u539f\u5b50\u6027\uff0c\u4f60\u53ef\u4ee5\u628a\u591a\u4e2a\u53d8\u91cf\u653e\u5728\u4e00\u4e2a \u5bf9\u8c61\u91cc\u6765\u8fdb\u884cCAS\u64cd\u4f5c\u3002<\/p>\n","protected":false},"excerpt":{"rendered":"
CAS\uff1a Compare and Swap,\u7ffb\u8bd1\u6210\u6bd4\u8f83\u5e76\u4ea4\u6362\u3002 java.util.concurrent\u5305\u4e2d\u501f […]<\/p>\n","protected":false},"author":7,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[118],"tags":[],"class_list":["post-9888","post","type-post","status-publish","format-standard","hentry","category-java"],"_links":{"self":[{"href":"http:\/\/wx.kaifamiao.info\/index.php\/wp-json\/wp\/v2\/posts\/9888","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/wx.kaifamiao.info\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/wx.kaifamiao.info\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/wx.kaifamiao.info\/index.php\/wp-json\/wp\/v2\/users\/7"}],"replies":[{"embeddable":true,"href":"http:\/\/wx.kaifamiao.info\/index.php\/wp-json\/wp\/v2\/comments?post=9888"}],"version-history":[{"count":1,"href":"http:\/\/wx.kaifamiao.info\/index.php\/wp-json\/wp\/v2\/posts\/9888\/revisions"}],"predecessor-version":[{"id":9889,"href":"http:\/\/wx.kaifamiao.info\/index.php\/wp-json\/wp\/v2\/posts\/9888\/revisions\/9889"}],"wp:attachment":[{"href":"http:\/\/wx.kaifamiao.info\/index.php\/wp-json\/wp\/v2\/media?parent=9888"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/wx.kaifamiao.info\/index.php\/wp-json\/wp\/v2\/categories?post=9888"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/wx.kaifamiao.info\/index.php\/wp-json\/wp\/v2\/tags?post=9888"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}