{"id":3853,"date":"2022-03-27T11:34:24","date_gmt":"2022-03-27T03:34:24","guid":{"rendered":"https:\/\/blog.coderfan.org\/?p=3853"},"modified":"2022-08-23T16:29:02","modified_gmt":"2022-08-23T08:29:02","slug":"epoll-and-select-usage-in-linux-system","status":"publish","type":"post","link":"https:\/\/blog.coderfan.org\/en\/epoll-and-select-usage-in-linux-system.html","title":{"rendered":"Linux\u7cfb\u7edf\u8c03\u7528epoll\u4e0eselect\u4f7f\u7528\u8be6\u89e3"},"content":{"rendered":"<div class='booster-block booster-read-block'>\n                <div class=\"twp-read-time\">\n                \t<i class=\"booster-icon twp-clock\"><\/i> <span>Read Time:<\/span>3 Minute, 46 Second                <\/div>\n\n            <\/div>\n<p class=\"has-text-align-justify\">\u5728\u4ee5\u524d\u7684\u9879\u76ee\u4e2d\uff0c\u7ecf\u5e38\u4f1a\u9700\u8981\u5bf9File Descriptor\uff08\u6ce8\u610f\uff1aI\/O\u5728Linux\u5185\u5f62\u5f0f\u4e0a\u4e5f\u4e3a\u6587\u4ef6\uff09\u8fdb\u884c\u76d1\u542c\uff0c\u5f53\u5176\u53d1\u751f\u53d8\u5316\u65f6\u6211\u4eec\u53ef\u4ee5\u76d1\u63a7\u5230\u76f8\u5173\u4fe1\u606f\uff0c\u4e4b\u540e\u4f1a\u8fdb\u884c\u76f8\u5173\u64cd\u4f5c\u3002\u90a3\u65f6\u5019\u5f88\u559c\u6b22\u901a\u8fc7select\u7684\u7cfb\u7edf\u8c03\u7528\u6765\u8fbe\u6210\u76d1\u542c\u76ee\u7684\uff08\u56e0\u4e3a\u5199\u6cd5\u56fa\u5b9a\uff0c\u65b9\u4fbf\u8bb0\u5fc6\uff09\uff0c\u540e\u6765\u5728\u770b\u5b89\u5353\u7cfb\u7edfInputFlinger\u5185\u7684EventHub\u65f6\u770b\u5230\u4e86\u5173\u4e8eepoll\u7684\u4f7f\u7528\uff0c\u4e8e\u662f\u5c31\u4ed4\u7ec6\u770b\u4e86\u4e00\u4e0b\u8fd9\u4e2a\u8fd9\u4e2a\u51fd\u6570,\u5bf9\u6bd4\u4e86\u4e00\u4e0b\u4e24\u8005\u95f4\u7684\u5dee\u5f02\uff0c\u90a3\u8fd9\u7bc7\u6587\u7ae0\u5c31\u662f\u6211\u5b66\u4e60\u6574\u7406\u7684\u5173\u4e8e\u8fd9\u4e24\u4e2a\u5e38\u7528\u7cfb\u7edf\u8c03\u7528\u7684\u4e00\u4e9b\u7b14\u8bb0\u3002<\/p>\n\n\n\n<p>\u6838\u5fc3\u77e5\u8bc6\u70b9\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li><strong>select\u4e0eepoll\u90fd\u53ef\u7528\u4e8eI\/O\u591a\u8def\u590d\u7528<\/strong><\/li><li><strong>select\u5185\u90e8\u91c7\u53d6\u8f6e\u8be2\u7684\u65b9\u5f0f\u83b7\u53d6\u6587\u4ef6\u63cf\u8ff0\u7b26\u7684\u72b6\u6001\u4fe1\u606f\uff0c\u6548\u7387\u8f83\u4f4e<\/strong><\/li><li><strong>epoll\u91c7\u7528\u4e8b\u4ef6\u9a71\u52a8\u578b\u7684\u901a\u77e5\u65b9\u5f0f\uff0c\u6548\u7387\u8f83\u9ad8<\/strong><\/li><li><strong>select\u7684\u76d1\u542c\u5b58\u5728\u4e0a\u9650\uff0c\u800cepoll\u5219\u6ca1\u6709\uff08\u5728\u7cfb\u7edf\u8d44\u6e90\u5141\u8bb8\u7684\u60c5\u51b5\u4e0b\uff09<\/strong><\/li><\/ul>\n\n\n\n<p class=\"has-text-align-justify\">\u9996\u5148\u6765\u4ecb\u7ecd\u4e00\u4e0bselect\uff0cselect\u51fd\u6570\u7684\u539f\u578b\u4e3a\uff1aint select(int nfds, fd_set <strong>readfds,                   fd_set writefds, fd_set <\/strong>* exceptfds,struct timeval *timeout);<\/p>\n\n\n\n<p>\u53c2\u6570\u89e3\u91ca\uff1a<\/p>\n\n\n\n<p> nfds \uff1a\u8be5\u53c2\u6570\u5e94\u8be5\u4e3a readfds \u3001 writefds \u3001 exceptfds \u8fd9\u4e09\u4e2afd\u96c6\u5408\u4e2d\u7684\u6700\u5927\u503c+1\u3002<\/p>\n\n\n\n<p class=\"has-text-align-justify\"> readfds \uff1a\u8be5fd\u96c6\u5408\u8868\u660e\u6211\u4eec\u9700\u8981\u76d1\u542c\u53ef\u8bfb\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u7684\u96c6\u5408\uff0c\u5982\u679c\u8fd9\u4e9b\u6587\u4ef6\u4e2d\u6709\u4e00\u4e2a\u6587\u4ef6\u53ef\u8bfb\uff0cselect\u8bed\u53e5\u5219\u4f1a\u8fd4\u56de\u4e00\u4e2a\u5927\u4e8e0\u7684\u503c\uff08\u8868\u793a\u6587\u4ef6\u53ef\u8bfb\uff09\uff0c\u8fd4\u56de\u540e\u6e05\u9664\u6389\u5176\u4e2d\u4e0d\u53ef\u8bfb\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u3002\u5982\u679c\u65e0\u6587\u4ef6\u53ef\u8bfb\uff0c\u5219\u4f1a\u6839\u636etimeout\u53c2\u6570\u5224\u65ad\u5355\u6b21\u76d1\u542c\u5468\u671f\u662f\u5426\u5230\u671f\uff0c\u5230\u671f\u8fd4\u56de0\u503c\uff0c\u53d1\u751f\u9519\u8bef\u8fd4\u56de\u8d1f\u503c\u3002\u5728select\u6b63\u786e\u8fd4\u56de\u540e\uff0c\u6211\u4eec\u53ef\u4ee5\u8fdb\u884c\u6b63\u5e38\u7684recv\u4e0eread\u64cd\u4f5c\u8fdb\u884c\u6570\u636e\u8bfb\u53d6\u3002<\/p>\n\n\n\n<p class=\"has-text-align-justify\"> writefds \uff1a\u4e0ereadfds\u7c7b\u4f3c\uff0c\u4e0d\u8fc7\u8fd9\u4e2a\u96c6\u5408\u662f\u8868\u660e\u9700\u8981\u76d1\u542c\u53ef\u5199\u72b6\u6001\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u3002\u5728select\u8fd4\u56de\u540e\uff0c\u4f1a\u6e05\u9664\u6389\u4e0d\u53ef\u5199\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\uff0c\u540c\u6837\u4e5f\u53ef\u901a\u8fc7timeout\u53c2\u6570\u8bbe\u5b9a\u8d85\u65f6\u65f6\u95f4\u3002\u4e00\u822c\u4e4b\u540e\u6211\u4eec\u4f1a\u901a\u8fc7send\u6216\u8005write\u8fdb\u884c\u6570\u636e\u5199\u5165\u3002<\/p>\n\n\n\n<p> exceptfds  \uff1a\u8fd9\u662f\u4e00\u4e2a\u53ef\u4ee5\u7528\u4e8e\u67d0\u4e9b\u7279\u6b8a\u60c5\u51b5\u800c\u53ef\u4ee5\u6392\u9664\u5728\u5916\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u96c6\u5408\u3002<\/p>\n\n\n\n<p> timeout \uff1a\u8be5\u53c2\u6570\u53ef\u4ee5\u4e3aselect\u7684\u76d1\u542c\u8bbe\u7f6e\u4e00\u4e2a\u8d85\u65f6\u65f6\u95f4\u3002<\/p>\n\n\n\n<p class=\"has-text-align-justify\">\u9664\u6b64\u4e4b\u5916\uff0cselect\u7684errno\u4fe1\u606f\u5305\u542b\u4ee5\u4e0b\u51e0\u4e2a\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>EBADF,\u8868\u660e\u6587\u4ef6\u63cf\u8ff0\u7b26\u635f\u574f<\/li><li>EINVAL\uff0c\u8868\u660e\u53c2\u6570\u4e0d\u5408\u6cd5<\/li><li>EINTER,\u8868\u660e\u63a5\u6536\u5230\u4e86\u4e2d\u65ad\u4fe1\u53f7\uff08Sig=2\uff0c\u4ee3\u8868Interrupt\uff09<\/li><li>ENOMEM\uff0c\u8868\u660e\u7cfb\u7edf\u6ca1\u6709\u8db3\u591f\u7684\u5185\u5b58<\/li><\/ul>\n\n\n\n<p class=\"has-text-align-justify\">\u901a\u5e38\u5728\u6211\u4eec\u4f7f\u7528select\u8bed\u53e5\u65f6\uff0c\u8fd8\u4f1a\u642d\u914d\u5176\u4ed6\u51fd\u6570\u8fdb\u884c\u4f7f\u7528\uff0c\u4e00\u822c\u9700\u8981\u642d\u914d<strong>FD_SET(int fd,fd_set *set),FD_ZERO(fd_set *set),FD_ISSET(int fd,fd_set *set)<\/strong>\u8fd9\u4e09\u4e2a\u51fd\u6570\u3002\u5176\u4e2d <strong>FD_SET<\/strong> \u51fd\u6570\u7528\u4e8e\u5c06\u6211\u4eec\u9700\u8981\u76d1\u542c\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u7ed1\u5b9a\u5230set\u8fd9\u4e2a\u6587\u4ef6\u63cf\u8ff0\u7b26\u7ed3\u5408\u4e2d\uff0c <strong>FD_ZERO<\/strong> \u5219\u7528\u4e8e\u5728\u7ed1\u5b9a\u524d\u5c06set\u5185\u6240\u6709\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u7ed9\u6e05\u9664\u6389\uff0c\u8be5\u51fd\u6570\u4e00\u822c\u662f\u521d\u59cb\u5316set\u65f6\u5c31\u9700\u8981\u8fdb\u884c\u8c03\u7528\u3002\u6b64\u5916\u8fd8\u6709\u4e00\u4e2aFD_ISSET\u51fd\u6570\uff0c\u5f53select\u8bed\u53e5\u8fd4\u56de\u65f6\uff0c\u4e00\u822c\u9700\u8981\u901a\u8fc7ISSET\u51fd\u6570\u5224\u5b9a\u6211\u4eec\u76d1\u542c\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u8fd8\u5728\u8be5set\u5185\u3002<\/p>\n\n\n\n<p>\u8fd9\u91cc\u653e\u4e0a\u4e00\u6bb5\u4ee3\u7801\uff0c\u5e2e\u52a9\u5927\u5bb6\u7406\u89e3\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>    msKeyEventFd=open(\"\/dev\/input\/event3\",O_RDONLY) \n    if(msKeyEventFd&lt;=0)\n    {\n        ALOGE(\"Open \/dev\/input\/event3 error,error:%s\",strerror\uff08errno));\n        goto \u2193RETURN;\n    }\n    ALOGI(\"Load event dev file success, start handle event\");\n    for (;;)\n    {\n        timeout.tv_sec = 1;\n        timeout.tv_usec = 0;\n        FD_ZERO(&amp;fds);\n        FD_SET(msKeyEventFd, &amp;fds);\n        FD_SET(msTouchEventFd, &amp;fds);\n        switch (select(msKeyEventFd + 1, &amp;fds, NULL, NULL, &amp;timeout))\n        {\n        case -1:\n            ALOGE(\"%s select error:%s\", __FUNCTION__, strerror(errno));\n            break;\n        case 0:\n            \/\/ALOGD(\"%s select timeout\", __FUNCTION__);\n            break;\n        default:\n            if (FD_ISSET(msKeyEventFd, &amp;fds))\n            {\n                getInstance()-&gt;handleKeyEvent();\n            }\n            break;\n        }\n    }\nRETURN:\n    if (msKeyEventFd &gt; 0)\n    {\n        close(msKeyEventFd);\n        msKeyEventFd = -1;\n    }<\/code><\/pre>\n\n\n\n<p class=\"has-text-align-justify\">\u8fd9\u91cc\u8fd8\u9700\u8981\u6ce8\u610f\u4e00\u70b9\uff0c\u5f80\u5f80\u6211\u4eec\u9700\u8981\u4e00\u76f4\u901a\u8fc7select\u8fdb\u884c\uff0c\u662f\u9700\u8981\u5faa\u73af\u4f53\u6765\u5b9e\u73b0\u7684\uff0c\u5728\u8fd9\u91cc\u9700\u8981\u5c06 timeout \u7684\u65f6\u95f4\u8bbe\u5b9a\u653e\u5728\u5faa\u73af\u4f53\u5185\u3002\u5982\u679ctimeout\u5168\u90e8\u8bbe\u7f6e\u4e3a0\uff0c\u5219select\u8bed\u53e5\u4f1a\u7acb\u523b\u8fd4\u56de\u4e3a0\u503c\uff0c\u5982\u679c\u4e3a\u7a7a\uff0c\u5219\u4f1a\u4e00\u76f4\u963b\u585e\u76f4\u5230\u76d1\u542c\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u51c6\u5907\u597d\u3002\u4e0eselect\u7c7b\u4f3c\u7684\u8fd8\u6709pselect\uff0c\u53ef\u4ee5\u8bf4pselect\u662fselect\u7684\u884d\u751f\uff0c\u4e24\u8005\u5728\u4f7f\u7528\u4e0a\u53ef\u4ee5\u8fdb\u884c\u4ee5\u4e0b\u5f62\u5f0f\u4e0a\u7684\u8f6c\u6362\uff1a<\/p>\n\n\n\n<p>\u4f7f\u7528pslect\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>ready = pselect(nfds, &amp;readfds, &amp;writefds, &amp;exceptfds,\ntimeout, &amp;sigmask);<\/code><\/pre>\n\n\n\n<p>\u5176\u7b49\u4ef7\u4e8e\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>sigset_t origmask;\npthread_sigmask(SIG_SETMASK, &amp;sigmask, &amp;origmask);\nready = select(nfds, &amp;readfds, &amp;writefds, &amp;exceptfds, timeout);\npthread_sigmask(SIG_SETMASK, &amp;origmask, NULL);<\/code><\/pre>\n\n\n\n<p class=\"has-text-align-justify\">\u901a\u8fc7 sigmask \u53c2\u6570\uff0cpselect\u53ef\u4ee5\u6355\u83b7\u4fe1\u53f7\uff0c\u4ee5\u9632\u6b62\u6253\u65ad\u5bf9\u6587\u4ef6\u63cf\u8ff0\u7b26\u7684\u76d1\u542c\uff0c\u8fd9\u5728\u67d0\u4e9b\u65f6\u523b\u662f\u6709\u5fc5\u8981\u7684\uff0c\u6bd4\u5982\u5b89\u5353Vold\u8fdb\u7a0b\u53d1\u9001\u4e2d\u65ad\u4fe1\u53f7\u7ed9\u6301\u6709\u8d44\u6e90\u7684\u8fdb\u7a0b\u65f6\uff0c\u800c\u8be5\u8fdb\u7a0b\u6070\u597d\u8fd8\u9700\u8981\u76d1\u542c\u67d0\u4e2a\u6587\u4ef6\uff0c\u4f7f\u7528pselect\u5c31\u53ef\u4ee5\u9632\u6b62\u76d1\u542c\u88ab\u6253\u65ad\u3002<\/p>\n\n\n\n<p class=\"has-text-align-justify\">\u8fd9\u91cc\u8fd8\u9700\u8981\u6ce8\u610f\u70b9\uff0c<strong>select\u80fd\u591f\u76d1\u542c\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u6700\u5927\u4e3aFD_SETSIZE(1024)<\/strong>\uff0c\u8fd9\u5bf9\u4e8e\u5f53\u524d\u7684\u5f88\u591a\u5e94\u7528\u6765\u8bb2\u4f1a\u5bfc\u81f4\u4e00\u5b9a\u7a0b\u5ea6\u4e0a\u5c40\u9650\uff0c\u800cepoll\u662f\u6ca1\u6709\u8fd9\u4e2a\u9650\u5236\u7684\u3002<\/p>\n\n\n\n<p class=\"has-text-align-justify\">\u63a5\u4e0b\u6765\u6211\u4eec\u8bb2\u8bb2epoll\uff0c\u4f7f\u7528epoll\u9700\u8981\u5f15\u5165\u5934\u6587\u4ef6<strong><span style=\"text-decoration: underline;\" class=\"ek-underline\">#include &lt;sys\/epoll.h&gt;<\/span><\/strong>\uff0cepoll\u5176\u5b9e\u6765\u6e90\u4e8epoll\u51fd\u6570\uff0c\u5173\u4e8epoll\u4e0d\u5728\u672c\u6587\u4e2d\u8d58\u8ff0\uff0c\u611f\u5174\u8da3\u7684\u670b\u53cb\u53ef\u4ee5\u81ea\u884c\u641c\u7d22\u76f8\u5173\u8d44\u6599\u3002<\/p>\n\n\n\n<p class=\"has-text-align-justify\">epoll\u4e0eselect\u6700\u5927\u7684\u4e0d\u540c\u5728\u4e8e\uff0cepoll\u76d1\u542cI\/O\u53d8\u5316\u662f\u7531\u4e8b\u4ef6\u89e6\u53d1\u7684\uff0c\u800cselect\u5219\u662f\u901a\u8fc7\u8f6e\u8be2\u53bb\u67e5\u770b\u6587\u4ef6\u662f\u5426\u51c6\u5907\u597d\u7684\u3002\u5982\u679c\u5728\u540c\u4e00\u65f6\u523b\uff0c\u4f60\u9700\u8981\u76d1\u542c\u591a\u4e2a\u6587\u4ef6\u63cf\u8ff0\u7b26\uff0cselect\u7684\u8f6e\u8be2\u6240\u8017\u8d39\u7684\u65f6\u95f4\u662f\u4e0d\u53ef\u5ffd\u7565\u7684\uff0c\u800cepoll\u5219\u6ca1\u6709\u8fd9\u4e2a\u95ee\u9898\u3002<\/p>\n\n\n\n<p class=\"has-text-align-justify\"><strong>epoll\u7684\u4e8b\u4ef6\u89e6\u53d1\u53ef\u4ee5\u5305\u542b\u8fb9\u7f18\u89e6\u53d1\u4e0e\u6c34\u5e73\u89e6\u53d1\uff0c\u8868\u73b0\u5728\u6a21\u62df\u7535\u8def\u4e0a\u4f60\u53ef\u4ee5\u7406\u89e3\u4e3a\u662f\u53d7\u4e0a\u5347\u6cbf\/\u4e0b\u964d\u6cbf\u89e6\u53d1\u8fd8\u662f\u53d7\u9ad8\u7535\u5e73\/\u4f4e\u7535\u5e73\u89e6\u53d1<\/strong>\u3002<\/p>\n\n\n\n<p class=\"has-text-align-justify\">\u4e0eselect\u7c7b\u4f3c\uff0c\u4f7f\u7528epoll\u5176\u5b9e\u4e5f\u6709\u4e00\u5b9a\u7684\u6d41\u7a0b\u89c4\u8303\uff0c\u5927\u81f4\u4e0a\u5305\u62ec\uff1a<\/p>\n\n\n\n<ul class=\"wp-block-list\"><li>epoll_create:\u521b\u5efa\u4e00\u4e2aepoll\u5b9e\u4f8b\u5e76\u8fd4\u56de\u4e00\u4e2a\u6587\u4ef6\u63cf\u8ff0\u7b26\u7528\u4e8e\u6307\u4ee3\u8be5\u5b9e\u5217<\/li><li>epoll_ctl\uff1a\u901a\u8fc7epoll_ctl\u5411epoll\u5b9e\u4f8b\u4e2d\u6dfb\u52a0\u4f60\u9700\u8981\u76d1\u542c\/\u79fb\u9664\u3001\u6216\u4fee\u6539\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26<\/li><li>epoll_wait:\u8fdb\u5165\u76d1\u542c\u72b6\u6001\uff0c\u76f4\u81f3\u76d1\u542c\u7684\u5bf9\u8c61\u5b58\u5728I\/O\u4e8b\u4ef6\uff0c\u8fd9\u4e2a\u76d1\u542c\u8fc7\u7a0b\u662f\u963b\u585e\u5f0f\u7684<\/li><\/ul>\n\n\n\n<p class=\"has-text-align-justify\">\u4e0b\u9762\u6211\u4eec\u6765\u8bb2\u8bb2\u8fd9\u5404\u4e2aAPI\u7684\u4f7f\u7528\u3002<\/p>\n\n\n\n<p class=\"has-text-align-justify\">\u5173\u4e8eepoll_create\uff0c\u5728\u5b9e\u9645\u4f7f\u7528\u8fc7\u7a0b\u4e2d\u901a\u5e38\u6211\u4eec\u4f7f\u7528\u7684\u662fepoll_create1\uff0c\u5176\u4f5c\u4e3aepoll_create\u7684\u62d3\u5c55\uff0c\u51fd\u6570\u539f\u578b\u4e3a\uff1a<strong>int epoll_create1(int <\/strong><em>flags<\/em><strong>);<\/strong> <\/p>\n\n\n\n<p class=\"has-text-align-justify\">\u8fd9\u91cc\u7684flags\u7528\u4e8e\u5bf9\u8be5\u6587\u4ef6\u63cf\u8ff0\u7b26\u505a\u4e00\u4e9b\u8bbe\u5b9a\uff0c\u4e00\u822c\u6211\u4eec\u4f7f\u7528O_CLOEXEC\uff0c\u8bbe\u7f6e\u8be5\u6807\u5fd7\u7684\u610f\u4e49\u5728\u4e8e\uff0c\u53ef\u4ee5\u786e\u4fdd\u5728\u591a\u7ebf\u7a0b\u7684\u64cd\u4f5c\u4e0b\u4fdd\u8bc1\u65e0\u7528\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u4f1a\u88ab\u53ca\u65f6\u5173\u95ed\uff0c\u8fd9\u4e00\u70b9\u5f88\u91cd\u8981\u3002<\/p>\n\n\n\n<p>\u5173\u4e8e\u8fd9\u4e00\u70b9\uff0c\u6458\u5f55\u4e00\u6bb5\u535a\u6587\uff1a<\/p>\n\n\n\n<p class=\"has-text-align-justify\"><em>\u6211\u4eec\u8003\u8651\u8fd9\u6837\u7684\u60c5\u51b5\uff1a\u7236\u8fdb\u7a0bfork\u51fa\u4e00\u4e2a\u5b50\u8fdb\u7a0b\uff0c\u5b50\u8fdb\u7a0b\u662f\u7236\u8fdb\u7a0b\u7684\u526f\u672c\uff0c\u83b7\u5f97\u7236\u8fdb\u7a0b\u7684\u6570\u636e\u7a7a\u95f4\u3001\u5806\u548c\u6808\u7684\u526f\u672c\uff0c\u5f53\u7136\u4e5f\u5305\u62ec\u7236\u8fdb\u7a0b\u6253\u5f00\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26<\/em>\u3002<\/p>\n\n\n\n<p class=\"has-text-align-justify\"><em>fork\u4e4b\u540e\u4e00\u822c\u6211\u4eec\u4f1a\u8c03\u7528exec\u6267\u884c\u53e6\u4e00\u4e2a\u7a0b\u5e8f\uff0c\u6b64\u65f6\u4f1a\u7528\u5168\u65b0\u7684\u7a0b\u5e8f\u66ff\u6362\u5b50\u8fdb\u7a0b\u7684\u6b63\u6587\u3001\u6570\u636e\u3001\u5806\u548c\u6808\u7b49\uff0c\u6b64\u65f6\u4fdd\u5b58\u6587\u4ef6\u63cf\u8ff0\u7b26\u7684\u53d8\u91cf\u5f53\u7136\u4e5f\u4e0d\u5b58\u5728\u4e86\uff0c\u6211\u4eec\u5c31\u65e0\u6cd5\u5173\u95ed\u65e0\u7528\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u4e86\u3002\u6240\u4ee5\u901a\u5e38\u6211\u4eec\u4f1a\u5728fork\u5b50\u8fdb\u7a0b\u540e\uff0c\u5728\u5b50\u8fdb\u7a0b\u4e2d\u76f4\u63a5\u6267\u884cclose\u5173\u6389\u65e0\u7528\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\uff0c\u7136\u540e\u518d\u6267\u884cexec\u3002<\/em><\/p>\n\n\n\n<p class=\"has-text-align-justify\"><em>\u4f46\u662f\u5728\u590d\u6742\u7cfb\u7edf\u4e2d\uff0c\u6709\u65f6\u6211\u4eecfork\u51fa\u5b50\u8fdb\u7a0b\u65f6\u5df2\u7ecf\u4e0d\u77e5\u9053\u6253\u5f00\u4e86\u591a\u5c11\u6587\u4ef6\u63cf\u8ff0\u7b26\u4e86\uff08\u5305\u62ecsocket\u53e5\u67c4\u7b49\uff09\uff0c\u5982\u679c\u8fdb\u884c\u9010\u4e00\u6e05\u7406\u96be\u5ea6\u5f88\u5927\u3002\u6211\u4eec\u671f\u671b\u7684\u662f\u80fd\u5728fork\u51fa\u5b50\u8fdb\u7a0b\u524d\u3001\u6253\u5f00\u67d0\u4e2a\u6587\u4ef6\u63cf\u8ff0\u7b26\u65f6\u5c31\u6307\u5b9a\u597d\u2014\u2014\u8fd9\u4e2a\u6587\u4ef6\u63cf\u8ff0\u7b26\u5728\u6211fork\u51fa\u5b50\u8fdb\u7a0b\u540e\u3001\u6267\u884cexec\u65f6\u5c31\u5173\u95ed\u3002\u5176\u5b9e\u662f\u6709\u8fd9\u6837\u7684\u65b9\u6cd5\u7684\uff1a\u5373\u6240\u8c13\u7684 close-on-exec\u3002<\/em><\/p>\n\n\n\n<p class=\"has-text-align-justify\">\u5728epoll_create\u8c03\u7528\u6210\u529f\u540e\uff0c\u4f1a\u8fd4\u56de0\u503c\uff0c\u5982\u679c\u8c03\u7528\u5931\u8d25\u5219\u4f1a\u8fd4\u56de-1\uff0c\u540c\u65f6\u4ea7\u751f\u76f8\u5e94\u7684errno\uff0c\u5728\u6b64\u4e0d\u505a\u8d58\u8ff0\u3002<\/p>\n\n\n\n<p class=\"has-text-align-justify\">\u4e4b\u540e\u6211\u4eec\u9700\u8981\u901a\u8fc7epoll_ctl\u52a0\u5165\u6211\u4eec\u9700\u8981\u76d1\u542c\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\uff0c\u5176\u51fd\u6570\u539f\u578b\u4e3a\uff1a<strong>int epoll_ctl(int <\/strong><em>epfd<\/em><strong>, int <\/strong><em>op<\/em><strong>, int <\/strong><em>fd<\/em><strong>, struct epoll_event *<\/strong><em>event<\/em><strong>);<\/strong><\/p>\n\n\n\n<p>\u5404\u53c2\u6570\u89e3\u91ca\u5982\u4e0b\uff1a<\/p>\n\n\n\n<p class=\"has-text-align-justify\"> <em>epfd<\/em> \uff1a\u7531epoll_create\u521b\u5efa\u5f97\u5230\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26<\/p>\n\n\n\n<p class=\"has-text-align-justify\"> <em>op<\/em> \uff1a\u4ee3\u8868\u5bf9\u6587\u4ef6\u63cf\u8ff0\u6240\u6267\u884c\u7684\u64cd\u4f5c\uff0c\u53ef\u7528\u503c\u5305\u62ec\uff1aEPOLL_CTL_ADD,\u8868\u793a\u6dfb\u52a0\uff1bEPOLL_CTL_DEL,\u8868\u793a\u5220\u9664\uff1bEPOLL_CTL_MOD\uff0c\u8868\u793a\u4fee\u6539<\/p>\n\n\n\n<p class=\"has-text-align-justify\"> <em>fd<\/em> \uff1a\u6211\u4eec\u9700\u8981\u6dfb\u52a0\/\u79fb\u9664\u6216\u8005\u4fee\u6539\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26<\/p>\n\n\n\n<p class=\"has-text-align-justify\"> <em>event<\/em> \uff1a\u7528\u4e8e\u8bbe\u5b9aepoll\u89e6\u53d1\u7684\u4e8b\u4ef6\u901a\u77e5\uff0c\u5176\u5b9e\u662f\u4e00\u4e2a\u7ed3\u6784\u4f53\uff0c\u7ed3\u6784\u4f53\u5982\u4e0b\uff1a<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>typedef union epoll_data {\n     void        *ptr;\n     int          fd;\n     uint32_t     u32;\n     uint64_t     u64;\n } epoll_data_t;\n struct epoll_event {\n     uint32_t     events;      \/* Epoll events *\/\n     epoll_data_t data;        \/* User data variable *\/\n };<\/code><\/pre>\n\n\n\n<p class=\"has-text-align-justify\">\u5728\u8fd9\u4e2a\u7ed3\u6784\u4f53\u4e2d\uff0cevents\u89c4\u5b9a\u4e86\u4e8b\u4ef6\u7c7b\u578b\uff0c\u5305\u542bEPOLLIN,\u8868\u660e\u6709\u6570\u636e\u8f93\u5165\uff0c\u53ef\u8bfb\uff1bEPOLLOUT,\u8868\u660e\u53ef\u4ee5\u8fdb\u884c\u6570\u636e\u8f93\u51fa\uff0c\u53ef\u5199\uff1bEPOLLRDHUP,\u8868\u660esocket\u5bf9\u65b9\u5173\u95ed\u8fde\u63a5\uff1bEPOLLET,\u8868\u660e\u91c7\u7528\u8fb9\u7f18\u89e6\u53d1\u65b9\u5f0f\uff0c\u6b64\u5916\u8fd8\u6709\u5f88\u591a\uff0c\u5728\u6b64\u4e0d\u505a\u8d58\u8ff0\uff0c\u800c data \u5219\u5305\u542b\u4e86\u6b64\u6b21event\u4e8b\u4ef6\u4e0b\u7684\u5177\u4f53\u6570\u636e\u5185\u5bb9\u3002<\/p>\n\n\n\n<p class=\"has-text-align-justify\">\u5728epoll_ctl\u8bbe\u5b9a\u5b8c\u6210\u4e4b\u540e\uff0c\u5c31\u53ef\u4ee5\u5229\u7528epoll_wait\u8fdb\u5165\u76d1\u542c\u72b6\u6001\u4e86\u3002\u5176\u51fd\u6570\u539f\u578b\u4e3a\uff1a<strong>int epoll_wait(int <\/strong><em>epfd<\/em><strong>, struct epoll_event *<\/strong><em>events<\/em><strong>,int <\/strong><em>maxevents<\/em><strong>, int <\/strong><em>timeout<\/em><strong>);<\/strong>\u5176\u4e2d <em>epfd<\/em> \u4e3aepoll_create\u521b\u5efa\u5f97\u5230\u7684fd\uff0c <em>events<\/em> \u7684\u5b9a\u4e49\u4e0e\u4e0a\u8ff0\u4e00\u81f4\uff0c\u5728\u5b9e\u9645\u4f7f\u7528\u65f6\u8fd9\u91cc\u901a\u5e38\u662f\u4e00\u4e2a\u6570\u7ec4\u6216\u8005\u5217\u8868\uff0c <em>maxevents<\/em> \u4ee3\u8868\u5355\u6b21wait\u6240\u83b7\u53d6\u5230\u7684\u6700\u5927event\u6570\u91cf\uff0c <em>timeout<\/em> \u4e0eselect\u7c7b\u4f3c\uff0c\u7528\u4e8e\u8bbe\u5b9a\u8d85\u65f6\u65f6\u95f4\uff0c\u8be5\u8d85\u65f6\u65f6\u95f4\u7684\u65f6\u949f\u57fa\u51c6\u662f<strong>CLOCK_MONOTONIC <\/strong>.\u8fd9\u91cc\u9700\u8981\u6ce8\u610f\u7684\u662f\uff0cepoll\u7684\u76d1\u542c\u8fd4\u56de\u4e0eselect\u7c7b\u4f3c\uff0c\u5373\uff1aI\/O\u72b6\u6001\u53d8\u5316\uff0c\u6216\u8005\u6536\u5230\u4e2d\u65ad\u4fe1\u53f7\uff0c\u6216\u8005\u662f\u8d85\u65f6\uff0c\u540c\u6837\u7684\u6211\u4eec\u53ef\u4ee5\u4f7f\u7528epoll_pwait\u6765\u5904\u7406\u6536\u5230\u4e2d\u65ad\u4fe1\u53f7\u7684\u60c5\u51b5\u3002<\/p>\n\n\n\n<p class=\"has-text-align-justify\">\u8fd9\u91cc\u6211\u4eec\u53ef\u4ee5\u770b\u770b\u5b89\u5353InputFlinger\u4e2dEventHub\u5bf9epoll\u7684\u4f7f\u7528\u3002<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code>EventHub::EventHub(void) :\n        mBuiltInKeyboardId(NO_BUILT_IN_KEYBOARD), mNextDeviceId(1), mControllerNumbers(),\n        mOpeningDevices(nullptr), mClosingDevices(nullptr),\n        mNeedToSendFinishedDeviceScan(false),\n        mNeedToReopenDevices(false), mNeedToScanDevices(true),\n        mPendingEventCount(0), mPendingEventIndex(0), mPendingINotify(false) {\n    acquire_wake_lock(PARTIAL_WAKE_LOCK, WAKE_LOCK_ID);\n\n    mEpollFd = <strong><span style=\"color: var(--theme-palette-color-1, #FB7258);\" class=\"ugb-highlight\">epoll_create1<\/span><\/strong>(EPOLL_CLOEXEC);\n    LOG_ALWAYS_FATAL_IF(mEpollFd &lt; 0, \"Could not create epoll instance: %s\", strerror(errno));\n\n    mINotifyFd = inotify_init();\n    mInputWd = inotify_add_watch(mINotifyFd, DEVICE_PATH, IN_DELETE | IN_CREATE);\n    LOG_ALWAYS_FATAL_IF(mInputWd &lt; 0, \"Could not register INotify for %s: %s\",\n            DEVICE_PATH, strerror(errno));\n    if (isV4lScanningEnabled()) {\n        mVideoWd = inotify_add_watch(mINotifyFd, VIDEO_DEVICE_PATH, IN_DELETE | IN_CREATE);\n        LOG_ALWAYS_FATAL_IF(mVideoWd &lt; 0, \"Could not register INotify for %s: %s\",\n                VIDEO_DEVICE_PATH, strerror(errno));\n    } else {\n        mVideoWd = -1;\n        ALOGI(\"Video device scanning disabled\");\n    }\n\n    struct epoll_event eventItem;\n    memset(&amp;eventItem, 0, sizeof(eventItem));\n    eventItem.events = EPOLLIN;\n    eventItem.data.fd = mINotifyFd;\n    int result = <strong><span style=\"color: var(--theme-palette-color-1, #FB7258);\" class=\"ugb-highlight\">epoll_ctl<\/span><\/strong>(mEpollFd, EPOLL_CTL_ADD, mINotifyFd, &amp;eventItem);\n    LOG_ALWAYS_FATAL_IF(result != 0, \"Could not add INotify to epoll instance.  errno=%d\", errno);<\/code><\/pre>\n\n\n\n<pre class=\"wp-block-code\"><code>        \/\/ service the timeout.\n        mPendingEventIndex = 0;\n\n        mLock.unlock(); \/\/ release lock before poll, must be before release_wake_lock\n        release_wake_lock(WAKE_LOCK_ID);\n\n        int pollResult = <strong><span style=\"color: var(--theme-palette-color-1, #FB7258);\" class=\"ugb-highlight\">epoll_wait<\/span><\/strong>(mEpollFd, mPendingEventItems, EPOLL_MAX_EVENTS, timeoutMillis);\n\n        acquire_wake_lock(PARTIAL_WAKE_LOCK, WAKE_LOCK_ID);\n        mLock.lock(); \/\/ reacquire lock after poll, must be after acquire_wake_lock\n<\/code><\/pre>\n\n\n\n<p class=\"has-text-align-justify\">\u597d\u4e86\uff0c\u4ee5\u4e0a\u5c31\u662f\u672c\u7bc7\u535a\u6587\u7684\u5168\u90e8\u4e86\uff0c\u5982\u679c\u89c9\u5f97\u8fd9\u7bc7\u6587\u7ae0\u6709\u7528\u7684\u8bdd\uff0c\u4e0d\u59a8\u70b9\u8d5e\u8f6c\u53d1\u5206\u4eab\u4e00\u4e0b\u5427\uff0c\u8c22\u8c22~<\/p>\n        <div class=\"booster-block booster-reactions-block\">\n            <div class=\"twp-reactions-icons\">\n                \n                <div class=\"twp-reacts-wrap\">\n                    <a react-data=\"be-react-1\" post-id=\"3853\" class=\"be-face-icons un-reacted\" href=\"javascript:void(0)\">\n                        <img decoding=\"async\" src=\"https:\/\/blog.coderfan.org\/wp-content\/plugins\/booster-extension\/\/assets\/icon\/happy.svg\" alt=\"Happy\">\n                    <\/a>\n                    <div class=\"twp-reaction-title\">\n                        Happy                    <\/div>\n                    <div class=\"twp-count-percent\">\n                                                    <span style=\"display: none;\" class=\"twp-react-count\">0<\/span>\n                        \n                                                <span class=\"twp-react-percent\"><span>0<\/span> %<\/span>\n                                            <\/div>\n                <\/div>\n\n                <div class=\"twp-reacts-wrap\">\n                    <a react-data=\"be-react-2\" post-id=\"3853\" class=\"be-face-icons un-reacted\" href=\"javascript:void(0)\">\n                        <img decoding=\"async\" src=\"https:\/\/blog.coderfan.org\/wp-content\/plugins\/booster-extension\/\/assets\/icon\/sad.svg\" alt=\"Sad\">\n                    <\/a>\n                    <div class=\"twp-reaction-title\">\n                        Sad                    <\/div>\n                    <div class=\"twp-count-percent\">\n                                                    <span style=\"display: none;\" class=\"twp-react-count\">0<\/span>\n                                                                        <span class=\"twp-react-percent\"><span>0<\/span> %<\/span>\n                                            <\/div>\n                <\/div>\n\n                <div class=\"twp-reacts-wrap\">\n                    <a react-data=\"be-react-3\" post-id=\"3853\" class=\"be-face-icons un-reacted\" href=\"javascript:void(0)\">\n                        <img decoding=\"async\" src=\"https:\/\/blog.coderfan.org\/wp-content\/plugins\/booster-extension\/\/assets\/icon\/excited.svg\" alt=\"Excited\">\n                    <\/a>\n                    <div class=\"twp-reaction-title\">\n                        Excited                    <\/div>\n                    <div class=\"twp-count-percent\">\n                                                    <span style=\"display: none;\" class=\"twp-react-count\">0<\/span>\n                                                                        <span 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