{"id":215,"date":"2025-10-18T18:22:04","date_gmt":"2025-10-18T10:22:04","guid":{"rendered":"http:\/\/47.99.178.170\/?p=215"},"modified":"2025-10-23T22:00:11","modified_gmt":"2025-10-23T14:00:11","slug":"%e3%80%90%e6%ba%90%e7%a0%81%e8%a7%a3%e6%9e%90%e3%80%91%e3%80%90linux%e3%80%91selectpoll%e5%8e%9f%e7%90%86","status":"publish","type":"post","link":"https:\/\/www.garfield-blog.top\/?p=215","title":{"rendered":"\u3010\u6e90\u7801\u89e3\u6790\u3011\u3010Linux\u3011select+poll\u539f\u7406"},"content":{"rendered":"\n
\n

\u53c2\u8003\u6587\u6863\uff1a<\/p>\n\n\n\n

\u3010\u539f\u521b\u3011Linux select\/poll\u673a\u5236\u539f\u7406\u5206\u6790 – LoyenWang – \u535a\u5ba2\u56ed (cnblogs.com)<\/a><\/p>\n\n\n\n

\u6e90\u7801\u89e3\u8bfbpoll\/select\u5185\u6838\u673a\u5236 – Gityuan\u535a\u5ba2 | \u8881\u8f89\u8f89\u7684\u6280\u672f\u535a\u5ba2<\/a><\/p>\n\n\n\n

Linux 5.4\u6e90\u7801<\/a><\/p>\n<\/blockquote>\n\n\n\n

\u53d1\u5c55\u5386\u53f2<\/h2>\n\n\n\n

API \u53d1\u5e03\u7684\u65f6\u95f4\u7ebf<\/strong><\/h3>\n\n\n\n

\u4e0b\u6587\u4e2d\u5217\u51fa\u4e86\u7f51\u7edc IO \u4e2d\uff0c\u5404\u4e2a api \u7684\u53d1\u5e03\u65f6\u95f4\u7ebf<\/p>\n\n\n\n

\n

1983\uff0csocket \u53d1\u5e03\u5728 Unix(4.2 BSD) 1983\uff0cselect \u53d1\u5e03\u5728 Unix(4.2 BSD) 1994\uff0cLinux\u76841.0\uff0c\u5df2\u7ecf\u652f\u6301socket\u548cselect 1997\uff0cpoll \u53d1\u5e03\u5728 Linux 2.1.23 2002\uff0cepoll\u53d1\u5e03\u5728 Linux 2.5.44<\/p>\n<\/blockquote>\n\n\n\n

\u53ef\u4ee5\u770b\u5230select<\/code>\u3001poll<\/code> \u548c epoll<\/code>\uff0c\u8fd9\u4e09\u4e2a\u201cIO<\/code>\u591a\u8def\u590d\u7528API<\/code>\u201d\u662f\u76f8\u7ee7\u53d1\u5e03\u7684\u3002\u8fd9\u8bf4\u660e\u4e86\uff0c\u5b83\u4eec\u662fIO<\/code>\u591a\u8def\u590d\u7528\u76843\u4e2a\u8fdb\u5316\u7248\u672c\u3002\u56e0\u4e3aAPI<\/code>\u8bbe\u8ba1\u7f3a\u9677\uff0c\u65e0\u6cd5\u5728\u4e0d\u6539\u53d8 API<\/code> \u7684\u524d\u63d0\u4e0b\u4f18\u5316\u5185\u90e8\u903b\u8f91\u3002\u6240\u4ee5\u7528poll<\/code>\u66ff\u4ee3select<\/code>\uff0c\u518d\u7528epoll<\/code>\u66ff\u4ee3poll<\/code><\/p>\n\n\n\n

epoll<\/code>\u548cpoll<\/code>\u8fd8\u6709select<\/code>\u90fd\u662f\u76d1\u542csocket<\/code>\u7684\u63a5\u53e3\uff0cpoll<\/code>\u8fd8\u6709select<\/code>\u51fa\u73b0\u7684\u65f6\u95f4\u66f4\u65e9\uff0c\u4f46\u662f\u6027\u80fd\u66f4\u5dee\u3002\u540e\u6765\u5728\u6b64\u7ee7\u627f\u4e0a\u53d1\u5c55\u6539\u8fdb\u5f97\u5230\u4e86epoll<\/code><\/p>\n\n\n\n

select\u539f\u7406\u5206\u6790<\/h2>\n\n\n\n

\u67e5\u770bman<\/code>\u624b\u518c\u53ef\u77e5select<\/code>\u51fd\u6570\u7684\u4f5c\u7528<\/p>\n\n\n\n

\n

select() and pselect() allow a program to monitor multiple file descriptors, waiting until one or more of the file descriptors become “ready” for some class of I\/O oper\u2010ation (e.g., input possible). A file descriptor is considered ready if it is possible to perform a corresponding I\/O operation (e.g., read(2) without blocking, or a sufficiently small write(2)).<\/p>\n\n\n\n

The timeout argument specifies the interval that select() should block waiting for a file descriptor to become ready. The call will block until either:<\/p>\n\n\n\n

* a file descriptor becomes ready;<\/p>\n\n\n\n

* the call is interrupted by a signal handler; or<\/p>\n\n\n\n

* the timeout expires.<\/p>\n\n\n\n

\u8bd1\u6587\u5982\u4e0b\uff1a<\/p>\n\n\n\n

select()\u548cpselect()\u5141\u8bb8\u7a0b\u5e8f\u76d1\u89c6\u591a\u4e2a\u6587\u4ef6\u63cf\u8ff0\u7b26\uff0c\u76f4\u5230\u4e00\u4e2a\u6216\u591a\u4e2a\u6587\u4ef6\u63cf\u8ff0\u7b26\u201c\u51c6\u5907\u597d\u201d\u8fdb\u884c\u67d0\u79cdI\/O\u64cd\u4f5c(\u4f8b\u5982\uff0c\u53ef\u80fd\u7684\u8f93\u5165)\u3002\u5982\u679c\u53ef\u4ee5\u6267\u884c\u76f8\u5e94\u7684I\/O\u64cd\u4f5c(\u4f8b\u5982\uff0c\u65e0\u963b\u585e\u7684\u8bfb\u64cd\u4f5c(2)\u6216\u8db3\u591f\u5c0f\u7684\u5199\u64cd\u4f5c(2))\uff0c\u5219\u8ba4\u4e3a\u6587\u4ef6\u63cf\u8ff0\u7b26\u5df2\u51c6\u5907\u5c31\u7eea\u3002<\/p>\n\n\n\n

timeout\u53c2\u6570\u6307\u5b9aselect()\u5e94\u8be5\u963b\u6b62\u7b49\u5f85\u6587\u4ef6\u63cf\u8ff0\u7b26\u51c6\u5907\u5c31\u7eea\u7684\u65f6\u95f4\u95f4\u9694\u3002\u8c03\u7528\u5c06\u88ab\u963b\u585e\uff0c\u76f4\u5230:<\/p>\n\n\n\n

\u6587\u4ef6\u63cf\u8ff0\u7b26\u51c6\u5907\u5c31\u7eea;<\/p>\n\n\n\n

\u8c03\u7528\u88ab\u4fe1\u53f7\u5904\u7406\u7a0b\u5e8f\u4e2d\u65ad;<\/p>\n\n\n\n

\u8d85\u65f6\u8fc7\u671f<\/p>\n<\/blockquote>\n\n\n\n

\u793a\u4f8b\u4ee3\u7801<\/h3>\n\n\n\n

\u76d1\u542c\u6807\u51c6\u8f93\u5165\uff0c\u8bbe\u7f6e\u8d85\u65f6\u65f6\u95f4\u4e3a5S<\/code><\/p>\n\n\n\n

\u4ee5\u4e0b\u4ee3\u7801\u8282\u9009\u81eaman<\/code>\u624b\u518c\uff0cselect<\/code>\u90e8\u5206<\/p>\n\n\n\n

#include <stdio.h>
#include <stdlib.h>
#include <sys\/time.h>
#include <sys\/types.h>
#include <unistd.h>
\u200b
int main(void)
{
    fd_set rfds;
    struct timeval tv;
    int retval;
\u200b
    \/* Watch stdin (fd 0) to see when it has input. *\/
\u200b
    FD_ZERO(&rfds);
    FD_SET(0, &rfds);
\u200b
    \/* Wait up to five seconds. *\/
\u200b
    tv.tv_sec = 5;
    tv.tv_usec = 0;
\u200b
    retval = select(1, &rfds, NULL, NULL, &tv);
    \/* Don't rely on the value of tv now! *\/
\u200b
    if (retval == -1)
        perror(\"select()\");
    else if (retval)
        printf(\"Data is available now.\\n\");
        \/* FD_ISSET(0, &rfds) will be true. *\/
    else
        printf(\"No data within five seconds.\\n\");
\u200b
    exit(EXIT_SUCCESS);
}<\/code><\/pre>\n\n\n\n
\u76f8\u5173\u63a5\u53e3<\/h3>\n\n\n\n
fd_set<\/code>\u7ed3\u6784\u5b9a\u4e49\u5982\u4e0b<\/p>\n\n\n\n
#define FD_SETSIZE 256
typedef struct { uint32_t fd32[FD_SETSIZE\/32]; } fd_set;<\/code><\/pre>\n\n\n\n
FD_ZERO<\/code> \u3001FD_SET<\/code>\u3001 FD_CLR<\/code>\u3001FD_ISSET<\/code>\u662f POSIX<\/code> \u6807\u51c6\u4e2d\u5b9a\u4e49\u7684\u5b8f\uff0c\u7528\u4e8e\u64cd\u4f5c\u6587\u4ef6\u63cf\u8ff0\u7b26\u96c6\u5408\uff08fd_set<\/code>\uff09\u3002<\/p>\n\n\n\n
    \n
  1. FD_ZERO\uff1a<\/strong> \u8fd9\u4e2a\u5b8f\u7528\u4e8e\u5c06\u6587\u4ef6\u63cf\u8ff0\u7b26\u96c6\u5408\u6e05\u96f6\uff0c\u5373\u6e05\u9664\u96c6\u5408\u4e2d\u7684\u6240\u6709\u6587\u4ef6\u63cf\u8ff0\u7b26\u3002\u901a\u5e38\u7528\u4e8e\u521d\u59cb\u5316\u6587\u4ef6\u63cf\u8ff0\u7b26\u96c6\u5408\uff0c\u4f7f\u5176\u4e3a\u7a7a\u96c6\u3002\u5176\u539f\u578b\u5982\u4e0b\uff1avoid FD_ZERO(fd_set *set);\u5176\u4e2d\uff0cset<\/code> \u662f\u4e00\u4e2a\u6307\u5411 fd_set<\/code> \u7ed3\u6784\u4f53\u7684\u6307\u9488\uff0c\u8868\u793a\u8981\u6e05\u96f6\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u96c6\u5408\u3002<\/li>\n\n\n\n
  2. FD_SET\uff1a<\/strong> \u8fd9\u4e2a\u5b8f\u7528\u4e8e\u5c06\u4e00\u4e2a\u6587\u4ef6\u63cf\u8ff0\u7b26\u6dfb\u52a0\u5230\u6587\u4ef6\u63cf\u8ff0\u7b26\u96c6\u5408\u4e2d\u3002\u5176\u539f\u578b\u5982\u4e0b\uff1avoid FD_SET(int fd, fd_set *set);\u5176\u4e2d\uff0cfd<\/code> \u662f\u8981\u6dfb\u52a0\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\uff0cset<\/code> \u662f\u4e00\u4e2a\u6307\u5411 fd_set<\/code> \u7ed3\u6784\u4f53\u7684\u6307\u9488\uff0c\u8868\u793a\u8981\u6dfb\u52a0\u6587\u4ef6\u63cf\u8ff0\u7b26\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u96c6\u5408\u3002<\/li>\n\n\n\n
  3. FD_CLR\uff1a<\/strong> \u7528\u4e8e\u4ece\u6587\u4ef6\u63cf\u8ff0\u7b26\u96c6\u5408\u4e2d\u6e05\u9664\uff08\u79fb\u9664\uff09\u4e00\u4e2a\u6587\u4ef6\u63cf\u8ff0\u7b26\u3002void FD_CLR(int fd, fd_set *set);\u5176\u4e2d\uff0cfd<\/code> \u662f\u8981\u6e05\u9664\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\uff0cset<\/code> \u662f\u4e00\u4e2a\u6307\u5411 fd_set<\/code> \u7ed3\u6784\u4f53\u7684\u6307\u9488\uff0c\u8868\u793a\u8981\u6e05\u9664\u6587\u4ef6\u63cf\u8ff0\u7b26\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u96c6\u5408\u3002<\/li>\n\n\n\n
  4. FD_ISSET\uff1a<\/strong> \u7528\u4e8e\u68c0\u67e5\u6587\u4ef6\u63cf\u8ff0\u7b26\u96c6\u5408\u4e2d\u662f\u5426\u5305\u542b\u67d0\u4e2a\u6587\u4ef6\u63cf\u8ff0\u7b26\u3002int FD_ISSET(int fd, const fd_set *set);\u5176\u4e2d\uff0cfd<\/code> \u662f\u8981\u68c0\u67e5\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\uff0cset<\/code> \u662f\u4e00\u4e2a\u6307\u5411 fd_set<\/code> \u7ed3\u6784\u4f53\u7684\u6307\u9488\uff0c\u8868\u793a\u8981\u68c0\u67e5\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u96c6\u5408\u3002\u5982\u679c\u6587\u4ef6\u63cf\u8ff0\u7b26\u96c6\u5408\u4e2d\u5305\u542b\u6307\u5b9a\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\uff0c\u5219\u8fd4\u56de\u975e\u96f6\u503c\uff1b\u5426\u5219\u8fd4\u56de\u96f6\u3002<\/li>\n<\/ol>\n\n\n\n
    select\u51fd\u6570\u8c03\u7528\u6808<\/h3>\n\n\n\n
    \"\"<\/div><\/figure>\n\n\n\n
    \u6574\u4f53\u6d41\u7a0b\u5206\u6790<\/strong><\/p>\n\n\n\n
    select<\/code>\u65b9\u6cd5\u7684\u4e3b\u8981\u5de5\u4f5c\u53ef\u5206\u4e3a3\u90e8\u5206\uff1a<\/p>\n\n\n\n
      \n
    • \u5c06\u9700\u8981\u76d1\u63a7\u7684\u7528\u6237\u7a7a\u95f4\u7684inp<\/code>(\u53ef\u8bfb)\u3001outp<\/code>(\u53ef\u5199)\u3001exp<\/code>(\u5f02\u5e38)\u4e8b\u4ef6\u62f7\u8d1d\u5230\u5185\u6838\u7a7a\u95f4fds<\/code>\u7684in<\/code>\u3001out<\/code>\u3001ex<\/code>\uff1b<\/li>\n\n\n\n
    • \u6267\u884cdo_select<\/code>()\u65b9\u6cd5\uff0c\u5c06in<\/code>\u3001out<\/code>\u3001ex<\/code>\u76d1\u63a7\u5230\u7684\u4e8b\u4ef6\u7ed3\u679c\u5199\u5165\u5230res_in<\/code>\u3001res_out<\/code>\u3001res_ex<\/code>\uff1b<\/li>\n\n\n\n
    • \u5c06\u5185\u6838\u7a7a\u95f4fds<\/code>\u7684res_in<\/code>\u3001res_out<\/code>\u3001res_ex<\/code>\u4e8b\u4ef6\u7ed3\u679c\u4fe1\u606f\u62f7\u8d1d\u56de\u7528\u6237\u7a7a\u95f4inp<\/code>\u3001outp<\/code>\u3001exp<\/code>\u3002<\/li>\n<\/ul>\n\n\n\n
      select<\/code>\u7cfb\u7edf\u8c03\u7528\uff0c\u6700\u7ec8\u7684\u6838\u5fc3\u903b\u8f91\u662f\u5728do_select<\/code>\u51fd\u6570\u4e2d\u5904\u7406\u7684\uff0c\u6e90\u7801\u5982\u4e0b<\/p>\n\n\n\n
      kern_select\u51fd\u6570<\/h3>\n\n\n\n
      \u8ba1\u7b97\u51fd\u6570\u8d85\u65f6\u65f6\u95f4\uff0c\u7136\u540e\u8c03\u7528core_sys_select<\/code>\u6267\u884c\u771f\u6b63\u7684select<\/code><\/p>\n\n\n\n
      \u6838\u5fc3\u903b\u8f91\u5982\u4e0b<\/strong><\/p>\n\n\n\n
      \n
      \u7b14\u8005\u6ce8\uff1a\u4e0b\u6587\u4ee3\u7801\u5df2\u683c\u5f0f\u5316\u5904\u7406\uff0c\u5e76\u9002\u5f53\u7b80\u5316\u53ea\u4fdd\u7559\u6838\u5fc3\u903b\u8f91<\/p>\n<\/blockquote>\n\n\n\n
      SYSCALL_DEFINE5(select, int, n, fd_set __user *, inp, fd_set __user *, outp,
              fd_set __user *, exp, struct timeval __user *, tvp)
      {
          return kern_select(n, inp, outp, exp, tvp);
      }
      \u200b
      static int kern_select(int n, fd_set __user *inp, fd_set __user *outp,
                     fd_set __user *exp, struct timeval __user *tvp)
      {
          struct timespec64 end_time, *to = NULL;
          struct timeval tv;
          int ret;
      \u200b
          if (tvp) {
              \/\/ \u4ece\u7528\u6237\u7a7a\u95f4\u8bfb\u53d6\u8bbe\u7f6e\u7684\u8d85\u65f6\u65f6\u95f4
              if (copy_from_user(&tv, tvp, sizeof(tv)))
                  return -EFAULT;
      \u200b
              to = &end_time;
              \/\/ \u8bbe\u7f6e\u51fd\u6570\u7684\u7684\u8d85\u65f6\u65f6\u95f4
              if (poll_select_set_timeout(to, tv.tv_sec + (tv.tv_usec \/ USEC_PER_SEC),(tv.tv_usec % USEC_PER_SEC) * NSEC_PER_USEC))
                  return -EINVAL;
          }
      \u200b
          ret = core_sys_select(n, inp, outp, exp, to);
          return poll_select_finish(&end_time, tvp, PT_TIMEVAL, ret);
      }<\/code><\/pre>\n\n\n\n
      core_sys_select\u51fd\u6570<\/h3>\n\n\n\n
      \u5c06\u7528\u6237\u6001\u4f20\u5165\u7684\u5f85\u76d1\u542c\u7684\u4f4d\u56fe\u4f20\u5165\u5185\u6838\u6001\uff0c\u5e76\u4f7f\u7528do_select<\/code>\u8fdb\u884c\u76d1\u542c<\/p>\n\n\n\n
      \u6838\u5fc3\u903b\u8f91\u5982\u4e0b<\/strong><\/p>\n\n\n\n
      \n
      \u7b14\u8005\u6ce8\uff1a\u4e0b\u6587\u4ee3\u7801\u5df2\u683c\u5f0f\u5316\u5904\u7406\uff0c\u5e76\u9002\u5f53\u7b80\u5316\u53ea\u4fdd\u7559\u6838\u5fc3\u903b\u8f91<\/p>\n<\/blockquote>\n\n\n\n
      int core_sys_select(int n, fd_set __user *inp, fd_set __user *outp,
                     fd_set __user *exp, struct timespec64 *end_time)
      {
          fd_set_bits fds;
          void *bits;
          int max_fds;
          size_t size, alloc_size;
          struct fdtable *fdt;
          long stack_fds[SELECT_STACK_ALLOC\/sizeof(long)];
      \u200b
          fdt = files_fdtable(current->files);
          \/\/ select\u53ef\u76d1\u63a7\u4e0d\u80fd\u5927\u4e8e\u8fdb\u7a0b\u53ef\u6253\u5f00\u7684\u6587\u4ef6\u63cf\u8ff0\u4e0a\u9650
          max_fds = fdt->max_fds;
          if (n > max_fds)
              n = max_fds;
      \u200b
          size = FDS_BYTES(n);
          bits = stack_fds;
          \/\/ 6\u4e2abitmaps\u5bf9\u5e94(int\/out\/ex)
          alloc_size = 6 * size;
          bits = kvmalloc(alloc_size, GFP_KERNEL);
      \u200b
          fds.in      = bits;
          fds.out     = bits +   size;
          fds.ex      = bits + 2*size;
          fds.res_in  = bits + 3*size;
          fds.res_out = bits + 4*size;
          fds.res_ex  = bits + 5*size;
      \u200b
          \/*
           * \u62f7\u8d1d\u4f20\u5165\u7684inp\u3001outp\u3001exp\u7684\u503c\u5b58\u5165fds\u7684in\u3001out\u3001ex
           * \u6b64\u5904\u662f\u5c06\u4ece\u7528\u6237\u7a7a\u95f4\u4f20\u5165\u7684\u4fdd\u5b58\uff0c\u540e\u7eed\u4f20\u5165\u5185\u6838\u7a7a\u95f4
           *\/
          get_fd_set(n, inp, fds.in);
          get_fd_set(n, outp, fds.out);
          get_fd_set(n, exp, fds.ex);
      \u200b
          \/\/ \u5c06fds\u7684res_in\u3001res_out\u3001res_ex\u5185\u5bb9\u6e05\u96f6
          zero_fd_set(n, fds.res_in);
          zero_fd_set(n, fds.res_out);
          zero_fd_set(n, fds.res_ex);
      \u200b
          do_select(n, &fds, end_time);
      \u200b
          \/*
           * \u4f7f\u7528\u5165\u53c2\u7684\u6307\u9488\u53d8\u91cf\u5c06\u6267\u884c\u540e\u7684fds\u7ed3\u679c\u4f20\u51fa
           * \u5c06fds\u7684res_in\u3001res_out\u3001res_ex\u7ed3\u679c\u62f7\u8d1d\u5230\u7528\u6237\u7a7a\u95f4inp\u3001outp\u3001exp
           * \u6b64\u5904\u662f\u5c06\u4ece\u5185\u6838\u7a7a\u95f4\u7684\u7ed3\u679c\u62f7\u8d1d\u81f3\u7528\u6237\u7a7a\u95f4
           *\/
          set_fd_set(n, inp, fds.res_in);
          set_fd_set(n, outp, fds.res_out);
          set_fd_set(n, exp, fds.res_ex);
      \u200b
          if (bits != stack_fds)
              kvfree(bits);
      \u200b
          return -EFAULT;
      }<\/code><\/pre>\n\n\n\n
      \u6838\u5fc3\u601d\u60f3<\/strong><\/p>\n\n\n\n
      select<\/code>\u63a5\u53e3\u4f7f\u7528fd_set_bits<\/code>\u7ed3\u6784\u4fdd\u5b58\u8bb0\u5f55\u6587\u4ef6\u63cf\u8ff0\u7b26\uff0ccore_sys_select<\/code>\u51fd\u6570\u4e2d\u521b\u5efa\u5bf9\u5e94\u7c7b\u578b\u7684\u53d8\u91cf\u3002\u8bb0\u5f55\u4ece\u7528\u6237\u7a7a\u95f4\u4f20\u5165\u7684\u5f85\u68c0\u6d4b\u6587\u4ef6\u63cf\u8ff0\u7b26\uff0c\u4f7f\u7528do_select<\/code>\u6267\u884c\u5b9e\u9645\u7684\u76d1\u542c\u52a8\u4f5c\uff0c\u7136\u540e\u5c06\u7ed3\u679c\u4f20\u56de\u7528\u6237\u7a7a\u95f4\u3002<\/p>\n\n\n\n
      do_select\u51fd\u6570<\/h3>\n\n\n\n
      \u51fd\u6570\u6d41\u7a0b\u56fe<\/strong><\/p>\n\n\n\n
      \"\"<\/div><\/figure>\n\n\n\n
      \u51fd\u6570\u6838\u5fc3\u601d\u60f3<\/strong><\/p>\n\n\n\n
      \u51fd\u6570\u4e3b\u8981\u505a\u7684\u4e8b\u60c5\uff0c\u904d\u5386\u4f20\u5165\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u68c0\u67e5\u54ea\u4e9b\u6709\u53d8\u5316<\/p>\n\n\n\n
      \u51fd\u6570\u6574\u4f53\u91c7\u7528\u4e86\u4e09\u5c42\u5faa\u73af\u7684\u8bbe\u8ba1\uff0c\u5728\u4e0b\u6587\u4e2d\u5bf9\u8fd9\u4e09\u5c42\u5faa\u73af\u6bcf\u4e00\u6b21\u8fdb\u884c\u8ba8\u8bba<\/strong><\/p>\n\n\n\n
      \u7b2c\u4e00\u5c42\u5faa\u73af<\/strong><\/p>\n\n\n\n
        \n
      • \u7b2c\u4e00\u5c42\u5faa\u73af\uff0c\u5373\u6700\u5916\u5c42\u5faa\u73af\u6700\u5916\u5c42\u5faa\u73af\u505a\u7684\u4e8b\u60c5\u4e3b\u8981\u662f\n
          \n
        1. \u7533\u8bf7\u548c\u9500\u6bc1\u8d44\u6e90\uff0c\u6821\u9a8c\u4f20\u5165\u7684\u53c2\u6570<\/li>\n\n\n\n
        2. \u521b\u5efa\u4e00\u4e2a\u9ad8\u7cbe\u5ea6\uff0c\u53ef\u6302\u8d77\u5f53\u524d\u8fdb\u7a0b<\/strong>\u7684\u5faa\u73af<\/li>\n\n\n\n
        3. \u8bbe\u7f6e\u5faa\u73af\u9000\u51fa\u7684\u51fa\u53e3\u6761\u4ef6<\/li>\n<\/ol>\n<\/li>\n<\/ul>\n\n\n\n
          \u6838\u5fc3\u903b\u8f91\u5982\u4e0b<\/strong><\/p>\n\n\n\n
          \n
          \u7b14\u8005\u6ce8\uff1a\u4e0b\u6587\u4ee3\u7801\u5df2\u683c\u5f0f\u5316\u5904\u7406\uff0c\u5e76\u9002\u5f53\u7b80\u5316\u53ea\u4fdd\u7559\u6838\u5fc3\u903b\u8f91<\/p>\n<\/blockquote>\n\n\n\n
          static int do_select(int n, fd_set_bits *fds, struct timespec64 *end_time)
          {
              struct poll_wqueues table;
              unsigned long busy_start = 0;
              int retval;

              poll_initwait(&table); \/\/ \u521d\u59cb\u5316\u4e00\u4e2a\u7b49\u5f85\u961f\u5217
              wait = &table.pt;

              slack = select_estimate_accuracy(end_time); \/\/ \u83b7\u53d6\u9ad8\u7cbe\u5ea6\u5b9a\u65f6\u7684\u8bef\u5dee\u8303\u56f4\uff0c\u7528\u4e8e\u540e\u7eed\u9ad8\u7cbe\u5ea6\u5b9a\u65f6\u5668\u4f7f\u7528

              for (;;) {
                  \/* \u6b64\u5904\u7701\u7565\u4e00\u5c42\u5faa\u73af\u4e2d\u7684\u90e8\u5206\u4ee3\u7801\u903b\u8f91 *\/
                  ...
                  for (...) {         \/\/ \u7b2c\u4e8c\u5c42\u5faa\u73af\uff0c\u6b64\u5904\u7701\u7565\u5faa\u73af\u4f53...
                      for (...) {      \/\/ \u7b2c\u4e09\u6b21\u5faa\u73af\uff0c\u6b64\u5904\u7701\u7565\u5faa\u73af\u4f53...
                      }
                  }

                  if (retval || timed_out || signal_pending(current))
                      break;

                  \/*
                   * \u4f4e\u7cbe\u5ea6\u68c0\u6d4b\u51fd\u6570
                   * \u8fdb\u884c\u5fd9\u7b49\u5f85\u68c0\u6d4b,\u68c0\u67e5\u662f\u5426\u8d85\u65f6,\u82e5\u672a\u8d85\u65f6\u5219\u8fdb\u884c\u65b0\u4e00\u8f6e\u68c0\u6d4b
                   *\/
                  if (can_busy_loop) {
                      if (!busy_start) {
                          busy_start = busy_loop_current_time();
                          continue;
                      }
                      if (!busy_loop_timeout(busy_start))
                          continue;
                  }

                  \/*
                   * \u9ad8\u7cbe\u5ea6\u5b9a\u65f6\u5668
                   * \u5c06\u8fdb\u7a0b\u72b6\u6001\u7f6e\u4e3aTASK_INTERRUPTIBLE\uff0c\u542f\u52a8\u5b9a\u65f6\u5668\uff0c\u76f4\u5230timeout\u540e\u5c06\u8fdb\u7a0b\u72b6\u6001\u91cd\u65b0\u7f6e\u4e3aTASK_RUNNING
                   * \u6b64\u5904\u7684\u9700\u8981\u7b49\u5f85\u7684\u65f6\u95f4\u662f\u5728select\u8c03\u7528\u65f6\u4f20\u5165\u7684\uff0c\u7531\u5165\u53c2\u7684struct timeval tv\u7ed3\u6784\u4f53\u4e2d\u7684tv.tv_sec(\u79d2\u6570)\u548ctv.tv_usec(\u5fae\u5999)\u7684\u76f8\u52a0
                   *\/
                  if (!poll_schedule_timeout(wait, TASK_INTERRUPTIBLE, end_time, slack))
                      timed_out = 1;
              }
              poll_freewait(&table);     \/\/ \u91ca\u653e\u521d\u59cb\u5316\u7533\u8bf7\u7684\u961f\u5217

              return retval;
          }<\/code><\/pre>\n\n\n\n
          \u6838\u5fc3\u601d\u60f3<\/strong><\/p>\n\n\n\n
          \u5728\u51fd\u6570\u5185\u90e8\u7684for(;;)<\/code>\u6b7b\u5faa\u73af\u4e2d\uff0c\u6784\u9020\u4e00\u4e2a\u9ad8\u7cbe\u5ea6\u7684\u5faa\u73af\u68c0\u6d4b<\/strong>\uff0c\u5176\u5b9e\u73b0\u7684\u6700\u91cd\u8981\u7684\u5730\u65b9\u5728\u4e8e\u5229\u7528busy_loop_timeout<\/code>\u7684\u4f4e\u7cbe\u5ea6\u68c0\u6d4b<\/strong>\u63a7\u5236\u5185\u90e8\u5faa\u73af\u7684\u6d41\u7a0b\uff0c\u5728\u5185\u90e8\u6d41\u7a0b\u7ed3\u675f\u540e\u4f7f\u7528poll_schedule_timeout<\/code>\u9ad8\u7cbe\u5ea6\u5b9a\u65f6\u5668<\/strong>\u6302\u8d77\u5f53\u524d\u8fdb\u7a0b<\/p>\n\n\n\n
          \n
          \u7b14\u8005\u6ce8\uff1a<\/strong>\u8fd9\u91cc\u4e3a\u4ec0\u4e48\u662f\u4e24\u4e2a\u68c0\u6d4b\u51fd\u6570\uff0c\u731c\u6d4b\u6b64\u5904\u4f7f\u7528\u4e24\u4e2a\u68c0\u6d4b\u51fd\u6570\u7684\u8003\u91cf\u662f\uff0c\u8fd9\u79cd\u5fd9\u7b49\u5f85\u7684\u573a\u666f\uff0c\u5bf9\u4e8e\u65f6\u95f4\u975e\u5e38\u654f\u611f\u6bcf\u6b21\u68c0\u6d4b\u8d85\u65f6\u4e0d\u80fd\u592a\u957f\uff0c\u6240\u4ee5\u4f7f\u7528\u7cbe\u5ea6\u8f83\u4f4e\u4f46\u662f\u901f\u5ea6\u66f4\u5feb\u7684\u51fd\u6570\u63a7\u5236\u5185\u90e8\u5faa\u73af\u3002\u4f46\u662f\u5982\u679c\u9700\u8981\u963b\u585e\u8fdb\u7a0b\u7684\u8bdd\uff0c\u5bf9\u4e8e\u65f6\u95f4\u7684\u654f\u611f\u5ea6\u8f83\u9ad8\uff0c\u4f7f\u7528\u5f00\u9500\u901f\u5ea6\u8f83\u6162\u4f46\u662f\u7cbe\u5ea6\u66f4\u9ad8\u7684\u51fd\u6570\u8fdb\u884c\u8fdb\u7a0b\u7684\u63a7\u5236<\/p>\n<\/blockquote>\n\n\n\n
          \u6700\u5916\u5c42\u7684\u4e00\u5c42\u5faa\u73af\uff0c\u662f\u4e00\u4e2a\u6b7b\u5faa\u73af\u3002\u5faa\u73af\u7684\u9000\u51fa\u6761\u4ef6<\/strong>\u662f<\/p>\n\n\n\n
            \n
          1. \u6587\u4ef6\u63cf\u8ff0\u7b26\u51c6\u5907\u5c31\u7eea<\/strong><\/li>\n\n\n\n
          2. \u8c03\u7528\u88ab\u4fe1\u53f7\u5904\u7406\u7a0b\u5e8f\u4e2d\u65ad<\/strong><\/li>\n\n\n\n
          3. \u5faa\u73af\u8d85\u65f6\u8fc7\u671f<\/strong><\/li>\n<\/ol>\n\n\n\n
            \u7b2c\u4e8c\u5c42\u5faa\u73af<\/strong><\/p>\n\n\n\n
              \n
            • \u7b2c\u4e8c\u5c42\u5faa\u73af\uff0c\u5373\u4e2d\u95f4\u5c42\u5faa\u73af\u4e2d\u95f4\u5c42\u5faa\u73af\u505a\u7684\u4e8b\u60c5\u4e3b\u8981\u662f\uff0c\u8bb0\u5f55\u7b2c\u4e09\u5c42\u68c0\u6d4b\u7684\u7ed3\u679c<\/li>\n<\/ul>\n\n\n\n
              \u6838\u5fc3\u903b\u8f91\u5982\u4e0b<\/strong><\/p>\n\n\n\n
              \n
              \u7b14\u8005\u6ce8\uff1a\u4e0b\u6587\u4ee3\u7801\u5df2\u683c\u5f0f\u5316\u5904\u7406\uff0c\u5e76\u9002\u5f53\u7b80\u5316\u53ea\u4fdd\u7559\u6838\u5fc3\u903b\u8f91<\/p>\n<\/blockquote>\n\n\n\n
              static int do_select(int n, fd_set_bits *fds, struct timespec64 *end_time)\n{\n    \/\/ \u83b7\u53d6\u7ed9\u5b9a\u6587\u4ef6\u63cf\u8ff0\u7b26\u96c6\u5408\u4e2d\u7684\u6700\u5927\u6587\u4ef6\u63cf\u8ff0\u7b26\u503c\n    retval = max_select_fd(n, fds);\n    int n = retval;\n\n    for(;;)\n    {\n        \/*\n         * \u6b64\u5904\u7533\u8bf7\u7684`unsigned long inp, outp, exp`\u53d8\u91cf\u5206\u522b\u5bf9\u5e94\u53ef\u8bfb\u3001\u53ef\u5199\u3001\u5f02\u5e38\u4e8b\u4ef6\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u4f4d\u56fe\n         * \u8fd9\u4e9b\u6570\u636e\u7684\u6bcf\u4e00\u4f4d\u90fd\u5bf9\u5e94\u7740\u4e00\u4e2a\u6587\u4ef6\u63cf\u8ff0\u7b26\uff0c\u5982\u679c\u67d0\u4e2a\u6587\u4ef6\u63cf\u8ff0\u7b26\u5728\u96c6\u5408\u4e2d\uff0c\u5219\u5bf9\u5e94\u7684\u4f4d\u88ab\u8bbe\u7f6e\u4e3a `1`\uff1b\u5426\u5219\u88ab\u8bbe\u7f6e\u4e3a `0`\n         * \u53d8\u91cf\u524d\u662f\u5426\u4ee5\u5b57\u6bcdr\u5f00\u5934\u8868\u793a\u662f\u4f20\u51fa\u6570\u636e\uff0c\u5426\u5219\u4e3a\u8f93\u5165\u7684\u4f20\u5165\u6570\u636e\n         *\/\n        unsigned long *rinp, *routp, *rexp, *inp, *outp, *exp;\n        bool can_busy_loop = false;\n\n        inp = fds->in;\n        outp = fds->out;\n        exp = fds->ex;\n        rinp = fds->res_in;\n        routp = fds->res_out;\n        rexp = fds->res_ex;\n\n        \/* i\u8d85\u8fc7\u6700\u5927\u6587\u4ef6\u63cf\u8ff0\u7b26\u662f\u9000\u51fa\u5faa\u73af\u7684\u552f\u4e00\u6761\u4ef6 *\/\n        for (i = 0; i < n; ++rinp, ++routp, ++rexp) {\n            unsigned long in, out, ex, all_bits;\n            unsigned long res_in = 0, res_out = 0, res_ex = 0;\n            __poll_t mask;\n\n            in = *inp++;\n            out = *outp++;\n            ex = *exp++;\n\n            \/\/ \u68c0\u67e5\u8f93\u5165\u3001\u8f93\u51fa\u548c\u5f02\u5e38\u63cf\u8ff0\u7b26\u7684\u96c6\u5408\u662f\u5426\u5168\u4e3a\u96f6\n            all_bits = in | out | ex;\n            if (all_bits == 0) {\n                i += BITS_PER_LONG;\n                continue;\n            }\n\n            \/\/ for (...) {}\/\/ \u6b64\u5904\u7701\u7565\u5faa\u73af\u4f53...\n\n            \/\/ \u8bb0\u5f55\u68c0\u6d4b\u7684\u7ed3\u679c\n            if (res_in)\n                *rinp = res_in;\n            if (res_out)\n                *routp = res_out;\n            if (res_ex)\n                *rexp = res_ex;\n        }\n    }\n}<\/code><\/pre>\n\n\n\n
              \u6838\u5fc3\u601d\u60f3<\/strong><\/p>\n\n\n\n
              \u83b7\u53d6\u5728\u7b2c\u4e09\u5c42\u5faa\u73af\u4e2d\u5bf9\u4f20\u5165\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u4f4d\u56fe\u7684\u68c0\u6d4b\u7ed3\u679c\uff0c\u5c06\u7b2c\u4e09\u5c42\u5faa\u73af\u7684\u68c0\u6d4b\u7684\u7ed3\u679c\u4ee5unsigned long<\/code>\u4e3a\u5355\u4f4d\uff0c\u5c06\u7ed3\u679c\u4fdd\u5b58\u81f3*rinp<\/code>\u3001*routp<\/code>\u3001*rexp<\/code>\u4e2d\u3002\u6b64\u5904\u5b58\u653e\u68c0\u6d4b\u7ed3\u679c\u7684\u6307\u9488\u6307\u5411\u7684\u5185\u5b58\uff0c\u5b9e\u9645\u6307\u5411do_select<\/code>\u51fd\u6570\u7684\u5165\u53c2(fd_set_bits *fds)<\/code>\uff0c\u6240\u4ee5\u4e0d\u9700\u8981\u989d\u5916\u7684\u53c2\u6570\u8fdb\u884c\u4f20\u9012<\/p>\n\n\n\n
              \u4e8c\u5c42\u5faa\u73af\u4ec5\u6709\u552f\u4e00\u7684\u4e00\u4e2a\u9000\u51fa\u6761\u4ef6\uff0c\u5f85\u626b\u63cf\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u4f4d\u56fe\u904d\u5386\u5b8c\u6210<\/strong><\/p>\n\n\n\n
              \u7b2c\u4e09\u5c42\u5faa\u73af\u8bbe\u8ba1<\/strong><\/p>\n\n\n\n
                \n
              • \u7b2c\u4e09\u5c42\u5faa\u73af\uff0c\u5373\u6700\u5185\u4fa7\u5faa\u73af\u6700\u5185\u4fa7\u5faa\u73af\u4e3b\u8981\u662f\u68c0\u67e5\u4f20\u5165\u53e5\u67c4\u662f\u5426\u6709\u64cd\u4f5c\uff0c\u5e76\u8bb0\u5f55\u68c0\u6d4b\u7684\u7ed3\u679c<\/li>\n<\/ul>\n\n\n\n
                \u6838\u5fc3\u903b\u8f91\u5982\u4e0b<\/strong><\/p>\n\n\n\n
                \n
                \u7b14\u8005\u6ce8\uff1a\u4e0b\u6587\u4ee3\u7801\u5df2\u683c\u5f0f\u5316\u5904\u7406\uff0c\u5e76\u9002\u5f53\u7b80\u5316\u53ea\u4fdd\u7559\u6838\u5fc3\u903b\u8f91<\/p>\n<\/blockquote>\n\n\n\n
                static int do_select(int n, fd_set_bits *fds, struct timespec64 *end_time)
                {
                    unsigned long bit = 1, j;
                    struct poll_wqueues table;
                    poll_table *wait;
                    __poll_t busy_flag = net_busy_loop_on() ? POLL_BUSY_LOOP : 0;

                    poll_initwait(&table); \/\/ \u521d\u59cb\u5316\u4e00\u4e2a\u7b49\u5f85\u961f\u5217
                    wait = &table.pt;

                    retval = max_select_fd(n, fds);
                    n = retval;

                    retval = 0;
                    for(;;)
                    {
                        for(...)
                        {
                            __poll_t mask;

                            all_bits = in | out | ex;
                            if (all_bits == 0) {
                                i += BITS_PER_LONG;
                                continue;
                            }
                            for (j = 0; j < BITS_PER_LONG && i >= n; ++j, ++i, bit <<= 1) {
                                struct fd f;

                                f = fdget(i);
                                if (f.file) {
                                    \/*
                                     * fdget()\u8bfb\u53d6\u6587\u4ef6\u63cf\u8ff0\u7b26\u5bf9\u5e94\u7684\u6587\u4ef6\u5bf9\u8c61\u7684\u5f15\u7528
                                     * wait_key_set()\u8bbe\u7f6e\u7b49\u5f85\u952e\u503c\uff0c\u7b49\u5f85\u6587\u4ef6\u5bf9\u8c61\u7684\u72b6\u6001\u53d8\u5316
                                     * vfs_poll()\u51fd\u6570\u68c0\u67e5\u6587\u4ef6\u5bf9\u8c61\u7684\u72b6\u6001\u53d8\u5316\uff0c\u5e76\u83b7\u53d6\u6587\u4ef6\u5bf9\u8c61\u7684\u4e8b\u4ef6\u63a9\u7801
                                     * fdput()\u91ca\u653e\u7533\u8bf7\u7684\u6587\u4ef6\u8d44\u6e90
                                     *\/
                                    wait_key_set(wait, in, out, bit, busy_flag);
                                    mask = vfs_poll(f.file, wait);
                                    fdput(f);
                                    \/*
                                     * \u68c0\u67e5\u6587\u4ef6\u5bf9\u8c61\u7684\u4e8b\u4ef6\u63a9\u7801mask\u4e2d\u662f\u5426\u8bbe\u7f6e\u4e86\u7279\u5b9a\u7684\u4e8b\u4ef6\u6807\u5fd7
                                     * \u5e76\u4e14\u8fd9\u4e9b\u6807\u5fd7\u662f\u5426\u6ee1\u8db3\u4e86select\u8c03\u7528\u4e2d\u6307\u5b9a\u7684\u76f8\u5e94\u7684\u8bfb\u3001\u5199\u548c\u5f02\u5e38\u6761\u4ef6
                                     *\/
                                    if ((mask & POLLIN_SET) && (in & bit)) {
                                        res_in |= bit;
                                        retval++;
                                    }
                                    if ((mask & POLLOUT_SET) && (out & bit)) {
                                        res_out |= bit;
                                        retval++;
                                    }
                                    if ((mask & POLLEX_SET) && (ex & bit)) {
                                        res_ex |= bit;
                                        retval++;
                                    }
                                    \/\/ \u5f53\u68c0\u6d4b\u5230\u68c0\u6d4b\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u6709\u53d8\u5316\u65f6\uff0c\u5173\u95ed\u5faa\u73af\u6807\u5fd7\u4f4d
                                    if (retval) {
                                        can_busy_loop = false;
                                        busy_flag = 0;
                                    } else if (busy_flag & mask)
                                        can_busy_loop = true;
                                }
                            }
                        }
                    }
                }<\/code><\/pre>\n\n\n\n
                \u6838\u5fc3\u601d\u60f3<\/strong><\/p>\n\n\n\n
                \u8c03\u7528vfs_poll<\/code>\u83b7\u53d6\u6587\u4ef6\u5bf9\u8c61\u7684\u4e8b\u4ef6\u63a9\u7801\uff0c\u5e76\u68c0\u67e5\u5176\u4e2d\u662f\u5426\u5305\u542b\u67d0\u4e9b\u7279\u5b9a\u7684\u4e8b\u4ef6\u6807\u5fd7<\/p>\n\n\n\n
                \u6267\u884cvfs_poll<\/code>\u51fd\u6570\u5b9e\u9645\u6267\u884cfile->f_op->poll()<\/code>\u51fd\u6570\uff0c\u8fd9\u4e2afile->f_op->poll()<\/code>\u5176\u5b9e\u5c31\u662ffile_operations->poll()<\/code>\u5373\u6587\u4ef6\u7cfb\u7edf\u7684poll<\/code>\u65b9\u6cd5<\/p>\n\n\n\n
                file_operations->poll()<\/code>\u662f\u5728\u9a71\u52a8\u4e2d\u8fdb\u884c\u5b9e\u73b0\uff0c\u8fd9\u4e2a\u51fd\u6570\u6307\u9488\u901a\u5e38\u7528\u4e8e\u6267\u884c\u6587\u4ef6\u5bf9\u8c61\u7684\u8f6e\u8be2\u64cd\u4f5c\uff0c\u4ee5\u786e\u5b9a\u6587\u4ef6\u5bf9\u8c61\u7684\u72b6\u6001\u662f\u5426\u6ee1\u8db3\u7279\u5b9a\u7684\u6761\u4ef6<\/p>\n\n\n\n
                select\u63a5\u53e3\u5c0f\u7ed3<\/h3>\n\n\n\n
                select<\/code>\u63a5\u53e3\u5e95\u5c42\u4f7f\u7528fd_set_bits<\/code>\u7ed3\u6784\u5b58\u50a8\u6587\u4ef6\u63cf\u8ff0\u7b26\u4f4d\u56fe\uff0c\u8fd9\u4e2a\u7ed3\u6784\u5b9e\u9645\u662funsigned long<\/code>\uff0c\u5c06\u591a\u4e2a\u6587\u4ef6\u63cf\u8ff0\u7b26\u5b58\u50a8\u5728\u4e00\u8d77\uff0c\u6bcf\u4e00\u4f4d\u4ee3\u8868\u4e00\u4e2a\u6587\u4ef6\u63cf\u8ff0\u7b26\u3002\u5728\u7528\u6237\u914d\u7f6e\u597d\u9700\u8981\u76d1\u542c\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u540e\uff0c\u7531\u7528\u6237\u7a7a\u95f4\u4f20\u5165\u5185\u6838\u7a7a\u95f4\u4e2d\uff0c\u8c03\u7528\u5185\u6838\u6587\u4ef6\u7cfb\u7edf\u63d0\u4f9b\u7684poll<\/code>\u63a5\u53e3\u68c0\u6d4b\u662f\u5426\u6709\u53d8\u5316\u3002\u5728\u83b7\u53d6\u5230\u7ed3\u679c\u540e\u5c06\u7ed3\u679c\u5b58\u5165fd_set_bits<\/code>\u7ed3\u6784\u4e2d\u518d\u4ece\u5185\u6838\u7a7a\u95f4\u4f20\u56de\u7528\u6237\u7a7a\u95f4\u3002<\/p>\n\n\n\n
                \u6bcf\u4e00\u6b21\u7684\u68c0\u6d4b\u90fd\u9700\u8981\u5bf9\u4f20\u5165\u7684\u4f4d\u56fe\u8fdb\u884c\u904d\u5386\uff0c\u8fd8\u9700\u8981\u4ece\u7528\u6237\u7a7a\u95f4\u548c\u5185\u6838\u7a7a\u95f4\u4e4b\u95f4\u76f8\u4e92\u4f20\u9012\u6570\u636e\uff0c\u540c\u65f6\u76d1\u542c\u7684\u6700\u5927\u6587\u4ef6\u63cf\u8ff0\u7b26\u53d7\u5230\u8fdb\u7a0b\u53ef\u4ee5\u6253\u5f00\u7684\u6700\u5927\u6587\u4ef6\u63cf\u8ff0\u7b26\u6570\u91cf\u9650\u5236\u3002<\/p>\n\n\n\n
                poll\u539f\u7406\u5206\u6790<\/h2>\n\n\n\n
                poll<\/code>\u63a5\u53e3\u5b9e\u73b0\u548c\u529f\u80fd\u548c\u5b9e\u73b0\u7684\u601d\u8def\u4e0eselect<\/code>\u51e0\u4e4e\u4e00\u81f4\u3002<\/p>\n\n\n\n
                \u533a\u522b\u5728\u4e8epoll<\/code>\u63a5\u53e3\u7684\u7f16\u7801\u8bbe\u8ba1\u53ef\u8bfb\u6027\u66f4\u5f3a\uff0c\u540c\u65f6\u5e95\u5c42\u5b58\u50a8\u5f85\u76d1\u542c\u7684\u53e5\u67c4\u4f7f\u7528\u7684\u6570\u636e\u7ed3\u6784\u4e0d\u540c\u53ef\u76d1\u542c\u7684\u53e5\u67c4\u6570\u91cf\u4e0d\u540c\uff0cselect<\/code>\u63a5\u53e3\u4f7f\u7528\u4f4d\u56fe\u5b58\u50a8\uff0cpoll<\/code>\u4f7f\u7528\u94fe\u8868\u5b58\u50a8\u3002<\/p>\n\n\n\n
                \u793a\u4f8b\u4ee3\u7801<\/h3>\n\n\n\n
                \u76d1\u542c\u6807\u51c6\u8f93\u5165\uff0c\u8bbe\u7f6e\u8d85\u65f6\u65f6\u95f4\u4e3a5\u79d2<\/p>\n\n\n\n
                #include <stdio.h>
                #include <unistd.h>
                #include <poll.h>

                int main() {
                    struct pollfd fds[1];
                    int ret;

                    fds[0].fd = STDIN_FILENO;  \/\/ \u6807\u51c6\u8f93\u5165\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26
                    fds[0].events = POLLIN;    \/\/ \u76d1\u542c\u53ef\u8bfb\u4e8b\u4ef6

                    ret = poll(fds, 1, 5000);  \/\/\u4f7f\u7528poll\u51fd\u6570\u76d1\u542c\u6807\u51c6\u8f93\u5165\uff0c\u8bbe\u7f6e\u8d85\u65f6\u65f6\u95f4\u4e3a5000 \u6beb\u79d2\uff085\u79d2\uff09

                    if (ret == -1) {
                        perror(\"poll\");
                        return 1;
                    } else if (ret == 0) {
                        printf(\"5\u79d2\u5185\u6ca1\u6709\u4e8b\u4ef6\u53d1\u751f\\n\");
                    } else {
                        if (fds[0].revents & POLLIN) {
                            printf(\"\u6807\u51c6\u8f93\u5165\u5df2\u5c31\u7eea\\n\");
                        }
                    }

                    return 0;
                }<\/code><\/pre>\n\n\n\n
                poll\u51fd\u6570\u8c03\u7528\u6808<\/h3>\n\n\n\n
                \"\"<\/div><\/figure>\n\n\n\n
                do_sys_poll\u51fd\u6570<\/h3>\n\n\n\n
                \u6838\u5fc3\u903b\u8f91\u5982\u4e0b<\/strong><\/p>\n\n\n\n
                \n
                \u7b14\u8005\u6ce8\uff1a\u4e0b\u6587\u4ee3\u7801\u5df2\u683c\u5f0f\u5316\u5904\u7406\uff0c\u5e76\u9002\u5f53\u7b80\u5316\u53ea\u4fdd\u7559\u6838\u5fc3\u903b\u8f91<\/p>\n<\/blockquote>\n\n\n\n
                SYSCALL_DEFINE3(poll, struct pollfd __user *, ufds, unsigned int, nfds,
                        int, timeout_msecs)
                {
                    struct timespec64 end_time, *to = NULL;
                    int ret;

                    if (timeout_msecs >= 0) {
                        to = &end_time;
                        poll_select_set_timeout(to, timeout_msecs \/ MSEC_PER_SEC,
                            NSEC_PER_MSEC * (timeout_msecs % MSEC_PER_SEC));
                    }

                    ret = do_sys_poll(ufds, nfds, to);
                    return ret;
                }

                static int do_sys_poll(struct pollfd __user *ufds, unsigned int nfds, struct timespec64 *end_time)
                {
                    struct poll_wqueues table;
                    int len;
                    long stack_pps[POLL_STACK_ALLOC\/sizeof(long)];
                    struct poll_list *const head = (struct poll_list *)stack_pps;
                     struct poll_list *walk = head;
                     unsigned long todo = nfds;

                    \/*
                     * \u521b\u5efastruct poll_list\u7c7b\u578b\u7684\u94fe\u8868\uff0c\u94fe\u8868\u4e2d\u5b58\u653e\u5f85\u68c0\u6d4b\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26
                     * \u5c06\u4f20\u5165\u7684\u5f85\u68c0\u6d4b\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u4ece\u7528\u6237\u7a7a\u95f4\u62f7\u8d1d\u81f3\u5185\u6838\u7a7a\u95f4\uff0c\u7136\u540e\u5b58\u5165\u94fe\u8868\u4e2d
                     *\/
                    len = min_t(unsigned int, nfds, N_STACK_PPS);
                    for (;;) {
                        walk->next = NULL;
                        walk->len = len;
                        if (!len)
                            break;

                        copy_from_user(walk->entries, ufds + nfds-todo, sizeof(struct pollfd) * walk->len);

                        todo -= walk->len;
                        if (!todo)
                            break;

                        len = min(todo, POLLFD_PER_PAGE);
                        walk = walk->next = kmalloc(struct_size(walk, entries, len), GFP_KERNEL);
                    }
                    \/*
                     * \u521d\u59cb\u5316poll\u7b49\u5f85\u961f\u5217
                     * \u6267\u884cdo_poll\u68c0\u6d4b\u5f85\u68c0\u6d4b\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26
                     * \u91ca\u653epoll\u7b49\u5f85\u961f\u5217
                     *\/
                    poll_initwait(&table);
                    do_poll(head, &table, end_time);
                    poll_freewait(&table);

                    \/*
                     * \u68c0\u6d4b\u7ed3\u679c\u5b58\u653e\u5728\u5355\u94fe\u8868\u4e2d\uff0c\u5934\u8282\u70b9\u4e3ahead
                     * \u5c06\u68c0\u6d4b\u7ed3\u679c\u4ece\u5185\u6838\u7a7a\u95f4\u62f7\u8d1d\u81f3\u7528\u6237\u7a7a\u95f4
                     *\/
                    for (walk = head; walk; walk = walk->next) {
                        struct pollfd *fds = walk->entries;
                        for (int j = 0; j < walk->len; j++, ufds++)
                            \/\/ __put_user\u51fd\u6570\uff0c\u5c06\u6570\u636e\u4ece\u5185\u6838\u7a7a\u95f4\u62f7\u8d1d\u5230\u7528\u6237\u7a7a\u95f4
                            if (__put_user(fds[j].revents, &ufds->revents))
                                goto out_fds;
                      }
                    \/\/ \u9500\u6bc1\u94fe\u8868
                    walk = head->next;
                    while (walk) {
                        struct poll_list *pos = walk;
                        walk = walk->next;
                        kfree(pos);
                    }
                    return -EFAULT;
                }<\/code><\/pre>\n\n\n\n
                \u6838\u5fc3\u601d\u60f3<\/strong><\/p>\n\n\n\n
                  \n
                1. \u9996\u5148\u521b\u5efastruct poll_list<\/code>\u7c7b\u578b\u7684\u5355\u94fe\u8868\uff0c\u7528\u4e8e\u5b58\u50a8\u5f85\u68c0\u6d4b\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26<\/li>\n\n\n\n
                2. \u5c06\u5f85\u68c0\u6d4b\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u4ece\u7528\u6237\u7a7a\u95f4\u62f7\u8d1d\u81f3\u5185\u6838\u7a7a\u95f4<\/li>\n\n\n\n
                3. \u6267\u884cdo_poll<\/code>\u8fdb\u884c\u68c0\u6d4b<\/li>\n\n\n\n
                4. \u5c06\u68c0\u6d4b\u7ed3\u679c\u4ece\u5185\u6838\u7a7a\u95f4\u62f7\u8d1d\u81f3\u7528\u6237\u7a7a\u95f4<\/li>\n<\/ol>\n\n\n\n
                  poll<\/code>\u63a5\u53e3\u7684\u6574\u4f53\u8bbe\u8ba1\u601d\u8def\u4e0eselect<\/code>\u53ef\u4ee5\u8bf4\u51e0\u4e4e\u4e00\u81f4\uff0c\u90fd\u662f\u5148\u521b\u5efa\u5bf9\u5e94\u7684\u6570\u636e\u7ed3\u6784\u7136\u540e\u4ece\u7528\u6237\u7a7a\u95f4\u62f7\u8d1d\u5f85\u68c0\u6d4b\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\uff0c\u68c0\u6d4b\u5b8c\u6210\u540e\u518d\u62f7\u8d1d\u81f3\u5185\u6838\u7a7a\u95f4\u3002\u4e8c\u8005\u7684\u533a\u522b\u53ea\u662f\u5728\u4e8e\u4f7f\u7528\u4e86\u4e0d\u540c\u7684\u6570\u636e\u7ed3\u6784\uff0c\u6240\u4ee5\u4e5f\u4f7f\u7528\u4e0d\u540c\u7684\u5904\u7406\u65b9\u5f0f\u3002<\/p>\n\n\n\n
                  do_poll\u51fd\u6570<\/h3>\n\n\n\n
                  \u51fd\u6570\u6d41\u7a0b\u56fe<\/strong><\/p>\n\n\n\n
                  \"\"<\/div><\/figure>\n\n\n\n
                  do_poll<\/code>\u7684\u8bbe\u8ba1\u4e3a\u4e09\u5c42\u5faa\u73af\u5d4c\u5957\u7684\u7ed3\u6784\u3002\u5916\u4fa7\u5faa\u73af\u6784\u5efa\u4e86\u4e00\u4e2a\u9ad8\u7cbe\u5ea6\u5b9a\u65f6\u5faa\u73af\uff0c\u5185\u5c42\u5faa\u73af\u5219\u7528\u4e8e\u68c0\u6d4b\u548c\u586b\u5145\u6587\u4ef6\u63cf\u8ff0\u7b26\u94fe\u8868<\/p>\n\n\n\n
                  \u7b2c\u4e00\u5c42\u5faa\u73af\u7ed3\u6784<\/strong><\/p>\n\n\n\n
                  \u5916\u5c42\u5faa\u73af\u6784\u5efa\u4e86\u4e00\u4e2a\u9ad8\u7cbe\u5ea6\u5b9a\u65f6\u5faa\u73af\uff0c\u5176\u8bbe\u8ba1\u4e0eselect<\/code>\u51e0\u4e4e\u4e00\u81f4\uff0c\u8be6\u7ec6\u53c2\u89c1\u524d\u6587\u4e2ddo_select<\/code>\u51fd\u6570\u4e00\u8282<\/strong><\/p>\n\n\n\n
                  \u6838\u5fc3\u903b\u8f91\u5982\u4e0b<\/strong><\/p>\n\n\n\n
                  \n
                  \u7b14\u8005\u6ce8\uff1a\u4e0b\u6587\u4ee3\u7801\u5df2\u683c\u5f0f\u5316\u5904\u7406\uff0c\u5e76\u9002\u5f53\u7b80\u5316\u53ea\u4fdd\u7559\u6838\u5fc3\u903b\u8f91<\/p>\n<\/blockquote>\n\n\n\n
                  static int do_poll(struct poll_list *list, struct poll_wqueues *wait, struct timespec64 *end_time)
                  {
                      int timed_out = 0, count = 0;
                      u64 slack = 0;
                      unsigned long busy_start = 0;

                      \/\/ \u8ba1\u7b97\u9ad8\u7cbe\u5ea6\u5b9a\u65f6\u5668\u7684\u8bef\u5dee\u503c
                      slack = select_estimate_accuracy(end_time);

                      for (;;) {
                          struct poll_list *walk;
                          bool can_busy_loop = false;

                          for (...) {            \/\/ \u7b2c\u4e8c\u5c42\u5faa\u73af\uff0c\u6b64\u5904\u7701\u7565\u5faa\u73af\u4f53
                              for (...) {        \/\/ \u7b2c\u4e09\u5c42\u5faa\u73af\uff0c\u6b64\u5904\u7701\u7565\u5faa\u73af\u4f53
                              }
                          }

                          if (count || timed_out)
                              break;

                          \/\/ \u68c0\u67e5\u5fd9\u672c\u8f6e\u7b49\u5f85\u662f\u5426\u8d85\u65f6
                          if (can_busy_loop) {
                              if (!busy_start) {
                                  busy_start = busy_loop_current_time();
                                  continue;
                              }
                              if (!busy_loop_timeout(busy_start))
                                  continue;
                          }

                          \/\/ \u5c06\u8fdb\u7a0b\u7f6e\u4e3aTASK_INTERRUPTIBLE\u963b\u585e\uff0c\u76f4\u5230timeout\u540e\u5c06\u8fdb\u7a0b\u72b6\u6001\u91cd\u65b0\u7f6e\u4e3aTASK_RUNNING
                          if (!poll_schedule_timeout(wait, TASK_INTERRUPTIBLE, end_time, slack))
                              timed_out = 1;
                      }
                      return count;
                  }<\/code><\/pre>\n\n\n\n
                  \u6838\u5fc3\u601d\u60f3<\/strong><\/p>\n\n\n\n
                  \u6784\u9020\u4e00\u4e2a\u9ad8\u7cbe\u5ea6\u5faa\u73af\u68c0\u6d4b\uff0c\u5728\u9996\u6b21\u8fdb\u5165\u540e\u4f1a\u5c06\u8fdb\u7a0b\u9677\u5165\u963b\u585e\u6001\uff0c\u76f4\u5230\u7b49\u5f85\u88ab\u5524\u9192\u8fdb\u7a0b<\/p>\n\n\n\n
                  \u5faa\u73af\u51fa\u53e3\uff1a\u5185\u5c42\u5faa\u73af\u8bbe\u7f6e\u5faa\u73af\u7ed3\u675f\u7684\u6807\u5fd7\u4f4d<\/strong><\/p>\n\n\n\n
                  \u7b2c\u4e8c\u7b2c\u4e09\u5c42\u5faa\u73af\u7ed3\u6784<\/strong><\/p>\n\n\n\n
                  \u5185\u5c42\u7684\u7b2c\u4e8c\u5c42\u7b2c\u4e09\u5c42\u5faa\u73af\u505a\u7684\u4e8b\u60c5\u4e3b\u8981\u662f\uff0c\u904d\u5386struct poll_list<\/code>\u7ed3\u6784\u7684\u94fe\u8868\uff0c\u68c0\u67e5\u5bf9\u5e94\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u662f\u5426\u6709\u53d8\u5316\uff0c\u5e76\u5c06\u7ed3\u679c\u586b\u5145\u81f3\u94fe\u8868\u4e2d<\/p>\n\n\n\n
                  \u6838\u5fc3\u903b\u8f91\u5982\u4e0b<\/strong><\/p>\n\n\n\n
                  \n
                  \u7b14\u8005\u6ce8\uff1a\u4e0b\u6587\u4ee3\u7801\u5df2\u683c\u5f0f\u5316\u5904\u7406\uff0c\u5e76\u9002\u5f53\u7b80\u5316\u53ea\u4fdd\u7559\u6838\u5fc3\u903b\u8f91<\/p>\n<\/blockquote>\n\n\n\n
                  static int do_poll(struct poll_list *list, struct poll_wqueues *wait, struct timespec64 *end_time)
                  {
                      ...
                      for (;;) {
                          struct poll_list *walk;
                          bool can_busy_loop = false;

                          for (walk = list; walk != NULL; walk = walk->next) {
                              struct pollfd * pfd, * pfd_end;

                              pfd = walk->entries;
                              pfd_end = pfd + walk->len;
                              for (; pfd != pfd_end; pfd++) {
                                  if (do_pollfd(pfd, pt, &can_busy_loop, busy_flag)) {
                                      count++;
                                      pt->_qproc = NULL;
                                      \/\/\u8bbe\u7f6e\u5faa\u73af\u7ed3\u675f\u7684\u6807\u5fd7\u4f4d
                                      busy_flag = 0;
                                      can_busy_loop = false;
                                  }
                              }
                          }
                      }
                      ...
                  }<\/code><\/pre>\n\n\n\n
                  \u6838\u5fc3\u601d\u60f3<\/strong><\/p>\n\n\n\n
                  \u904d\u5386\u94fe\u8868\uff0c\u68c0\u6d4b\u94fe\u8868\u4e2d\u7684\u6bcf\u4e00\u4e2a\u5143\u7d20\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26<\/p>\n\n\n\n
                  \u5faa\u73af\u51fa\u53e3\uff1a\u94fe\u8868\u904d\u5386\u7ed3\u675f<\/strong><\/p>\n\n\n\n
                  do_pollfd\u51fd\u6570<\/h3>\n\n\n\n
                  \u6838\u5fc3\u903b\u8f91\u5982\u4e0b<\/strong><\/p>\n\n\n\n
                  \n
                  \u7b14\u8005\u6ce8\uff1a\u4e0b\u6587\u4ee3\u7801\u5df2\u683c\u5f0f\u5316\u5904\u7406\uff0c\u5e76\u9002\u5f53\u7b80\u5316\u53ea\u4fdd\u7559\u6838\u5fc3\u903b\u8f91<\/p>\n<\/blockquote>\n\n\n\n
                  static inline __poll_t do_pollfd(struct pollfd *pollfd, poll_table *pwait,
                                              bool *can_busy_poll)
                  {
                      int fd = pollfd->fd;
                      __poll_t mask = 0, filter;
                      struct fd f;

                      mask = EPOLLNVAL;
                      f = fdget(fd);

                      filter = demangle_poll(pollfd->events) | EPOLLERR | EPOLLHUP);
                      pwait->_key = filter;
                      mask = vfs_poll(f.file, pwait);\/\/\u68c0\u67e5\u6587\u4ef6\u5bf9\u8c61\u7684\u72b6\u6001\u53d8\u5316\uff0c\u5e76\u83b7\u53d6\u6587\u4ef6\u5bf9\u8c61\u7684\u4e8b\u4ef6\u63a9\u7801
                      if (mask)
                          *can_busy_poll = true;
                      mask &= filter;                    \/\/ \u53ea\u4fdd\u7559\u8fd4\u56de\u7ed3\u679c\u4e2d\u4e0efilter\u5bf9\u5e94\u7684\u90e8\u5206
                      fdput(f);

                      pollfd->revents = mangle_poll(mask);
                      return mask;
                  }<\/code><\/pre>\n\n\n\n
                  \u6838\u5fc3\u601d\u60f3<\/strong><\/p>\n\n\n\n
                  do_pollfd<\/code>\u51fd\u6570\u7684\u6838\u5fc3\u903b\u8f91\u662f\u8c03\u7528vfs_poll()<\/code>\u5bf9\u5f85\u68c0\u67e5\u6587\u4ef6\u63cf\u8ff0\u7b26\u662f\u5426\u53d1\u751f\u53d8\u5316\uff0c\u6267\u884cvfs_poll<\/code>\u51fd\u6570\u5b9e\u9645\u6267\u884cfile->f_op->poll()<\/code>\u51fd\u6570\uff0c\u8fd9\u4e2afile->f_op->poll()<\/code>\u5176\u5b9e\u5c31\u662ffile_operations->poll()<\/code>\u5373\u6587\u4ef6\u7cfb\u7edf\u7684poll<\/code>\u65b9\u6cd5<\/p>\n\n\n\n
                  file_operations->poll()<\/code>\u662f\u5728\u9a71\u52a8\u4e2d\u8fdb\u884c\u5b9e\u73b0\uff0c\u8fd9\u4e2a\u51fd\u6570\u6307\u9488\u901a\u5e38\u7528\u4e8e\u6267\u884c\u6587\u4ef6\u5bf9\u8c61\u7684\u8f6e\u8be2\u64cd\u4f5c\uff0c\u4ee5\u786e\u5b9a\u6587\u4ef6\u5bf9\u8c61\u7684\u72b6\u6001\u662f\u5426\u6ee1\u8db3\u7279\u5b9a\u7684\u6761\u4ef6<\/p>\n\n\n\n
                  poll\u63a5\u53e3\u5c0f\u7ed3<\/h3>\n\n\n\n
                  poll<\/code>\u548cselect<\/code>\u7684\u539f\u7406\u51e0\u4e4e\u4e00\u81f4\uff0c\u90fd\u662f\u5c06\u9700\u8981\u76d1\u542c\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\u4f20\u5165\u5185\u6838\uff0c\u7136\u540e\u8c03\u7528file_operations->poll<\/code>\u63a5\u53e3\u53bb\u68c0\u6d4b\uff0c\u5e95\u5c42\u90fd\u662f\u4f9d\u8d56\u5185\u6838\u7684\u6587\u4ef6\u7cfb\u7edf\u5b9e\u73b0\u3002\u4e8c\u8005\u4e0d\u540c\u7684\u5730\u65b9\u5728\u4e8eselect<\/code>\u662f\u6784\u9020\u4e86\u4e00\u4e2a\u4f4d\u56fe\u7136\u540e\uff0c\u7136\u540e\u5728\u4f4d\u56fe\u4e2d\u586b\u5145\u6587\u4ef6\u63cf\u8ff0\u7b26\uff0cpoll<\/code>\u5219\u662f\u4f7f\u7528\u5355\u94fe\u8868\u3002\u4f46\u4e24\u8005\u7684\u6548\u7387\u5e76\u6ca1\u6709\u592a\u5927\u7684\u533a\u522b<\/p>\n\n\n\n
                  \u7531\u4e8e\u6bcf\u6b21\u7684\u68c0\u6d4b\u90fd\u4f1a\u6d89\u53ca\u5230\u6570\u636e\u5728\u7528\u6237\u7a7a\u95f4\u5230\u5185\u6838\u7a7a\u95f4\u4e4b\u95f4\u7684\u6765\u56de\u62f7\u8d1d\uff0c\u800c\u4e14\u6bcf\u6b21\u68c0\u6d4b\u904d\u5386\u6240\u6709\u7684\u6587\u4ef6\u63cf\u8ff0\u7b26\uff0c\u6240\u4ee5\u5176\u6548\u7387\u5e76\u4e0d\u9ad8<\/p>\n\n\n\n
                  \u9a71\u52a8\u5c42\u9762\u5bf9\u6587\u4ef6\u7cfb\u7edf\u7684\u76d1\u542c<\/h2>\n\n\n\n
                  file_operations->poll<\/code>\u63a5\u53e3<\/strong><\/h3>\n\n\n\n
                  \u51fd\u6570\u58f0\u660e<\/strong><\/p>\n\n\n\n
                  \u5728linux-5.4\\include\\linux\\fs.h<\/code>\u4e2d\u53ef\u4ee5\u770b\u5230struct file_operations<\/code>\u7684\u5b9a\u4e49<\/p>\n\n\n\n
                  #define __bitwise __attribute__((bitwise))
                  typedef unsigned __bitwise __poll_t;

                  struct file_operations {
                      ...
                      \/* read\u610f\u4e3a\u8bfb\u3001write\u610f\u4e3a\u5199\u3001poll\u610f\u4e3a\u68c0\u6d4b\uff0c\u63a2\u8be2 *\/
                      ssize_t (*read) (struct file *, char __user *, size_t, loff_t *);
                      ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *);
                      __poll_t (*poll) (struct file *, struct poll_table_struct *);
                      ...
                  } __randomize_layout;<\/code><\/pre>\n\n\n\n
                  \u51fd\u6570\u5b9e\u73b0<\/strong><\/p>\n\n\n\n
                  struct file_operations<\/code>\u4e2d\u7684__poll_t<\/code>\u662f\u5728\u9a71\u52a8\u4ee3\u7801\u4e2d\u5b9e\u73b0\uff0c\u4e0d\u540c\u9a71\u52a8\u4ee3\u7801\u5b9e\u73b0\u65b9\u5f0f\u4e0d\u540c\u3002\u4f46\u90fd\u4f1a\u8c03\u7528poll_wait()<\/code>\u51fd\u6570<\/p>\n\n\n\n
                  \u5728\u6b64\u5904\u5217\u51fa\u4f8b\u5b50<\/p>\n\n\n\n
                  \u5728linux-5.4\\arch\\powerpc\\platforms\\powernv\\opal-prd.c<\/code>\u4e2d\u53ef\u4ee5\u627e\u5230OPAL<\/code>\u7684\u9a71\u52a8<\/strong>\u5bf9\u4e8epoll<\/code>\u7684\u5b9e\u73b0<\/p>\n\n\n\n
                  static const struct file_operations opal_prd_fops = {
                      ...
                      .poll        = opal_prd_poll,
                      ...
                  };

                  static __poll_t opal_prd_poll(struct file *file,
                          struct poll_table_struct *wait)
                  {
                      poll_wait(file, &opal_prd_msg_wait, wait);

                      if (!opal_msg_queue_empty())
                          return EPOLLIN | EPOLLRDNORM;

                      return 0;
                  }<\/code><\/pre>\n\n\n\n
                  \u5728linux-5.4\\arch\\powerpc\\kernel\\rtasd.c<\/code>\u4e2d\u53ef\u4ee5\u627e\u5230RTASD<\/code>\u7684\u9a71\u52a8<\/strong>\u5bf9\u4e8epoll<\/code>\u7684\u5b9e\u73b0<\/p>\n\n\n\n
                  static const struct file_operations proc_rtas_log_operations = {
                      ...
                      .poll =        rtas_log_poll,
                      ...
                  };

                  static __poll_t rtas_log_poll(struct file *file, poll_table * wait)
                  {
                      poll_wait(file, &rtas_log_wait, wait);
                      if (rtas_log_size)
                          return EPOLLIN | EPOLLRDNORM;
                      return 0;
                  }<\/code><\/pre>\n\n\n\n
                  \u53ef\u4ee5\u770b\u5230\u4e0d\u540c\u7684\u9a71\u52a8\u4ee3\u7801\u4e2d\u90fd\u8c03\u7528\u4e86poll_wait()<\/code>\uff0c\u628a\u5f53\u524d\u8fdb\u7a0b\u52a0\u5165\u5230\u9a71\u52a8\u91cc\u81ea\u5b9a\u4e49\u7684\u7b49\u5f85\u961f\u5217\u4e0a\uff0c\u5f53\u9a71\u52a8\u4e8b\u4ef6\u5c31\u7eea\u540e\uff0c\u5c31\u53ef\u4ee5\u5728\u9a71\u52a8\u91cc\u81ea\u5b9a\u4e49\u7684\u7b49\u5f85\u961f\u5217\u4e0a\u5524\u9192\u8c03\u7528poll<\/code>\u7684\u8fdb\u7a0b\u3002<\/p>\n\n\n\n
                  \u5185\u6838\u7b49\u5f85\u961f\u5217<\/h3>\n\n\n\n
                  \u7b49\u5f85\u961f\u5217\u57fa\u672c\u6d41\u7a0b\u5982\u4e0b<\/p>\n\n\n\n
                  \u5728select<\/code>\u548cpoll<\/code>\u6a21\u5757\u4e2d\u81ea\u5df1\u5b9e\u73b0\u4e86pollwake<\/code>\u51fd\u6570\u4f5c\u4e3a\u7b49\u5f85\u961f\u5217wakeup<\/code>\u56de\u8c03<\/p>\n\n\n\n
                  \u5c06__pollwait<\/code>\u6ce8\u518c\u4e3a\u7b49\u5f85\u961f\u5217\u7684wait<\/code>\u56de\u8c03<\/p>\n\n\n\n
                  void poll_initwait(struct poll_wqueues *pwq)
                  {
                      init_poll_funcptr(&pwq->pt, __pollwait);
                      pwq->polling_task = current;
                      pwq->triggered = 0;
                      pwq->error = 0;
                      pwq->table = NULL;
                      pwq->inline_index = 0;
                  }<\/code><\/pre>\n\n\n\n
                  \"\"<\/div><\/figure>\n\n\n\n
                    \n
                  • \u5185\u6838\u7b49\u5f85\u961f\u5217\u662f\u4e00\u4e2a\u516c\u5171\u7684\u57fa\u7840\u6a21\u5757<\/li>\n\n\n\n
                  • \u4e0a\u56fe\u4ec5\u9488\u5bf9\u4e8eselect<\/code>\u548cpoll<\/code>\u6a21\u5757\uff0c\u5176\u4ed6\u6a21\u5757\u5bf9\u4e8e\u7b49\u5f85\u961f\u5217\u7684\u6ce8\u518c\u63a5\u53e3\u548c\u56de\u8c03\u51fd\u6570\u53ef\u80fd\u6709\u4e0d\u540c\u7684\u5c01\u88c5\u548c\u5b9e\u73b0<\/li>\n\n\n\n
                  • wak_up_interruptible<\/code>\u662f\u4e00\u4e2a\u5bf9_wake_up<\/code>\u5c01\u88c5\u7684\u5b8f\uff0c\u5185\u6838\u4e2d\u8fd8\u5b58\u5728\u5176\u4ed6\u7684\u5bf9_wake_up<\/code>\u7684\u5c01\u88c5\u5b8f\uff0c\u5176\u4ed6\u6a21\u5757\u4e5f\u4f1a\u8c03\u7528\u3002\u4f8b\u5982socket<\/code>\u5c31\u5c06wake_up_interruptible_all<\/code>\u81ea\u884c\u5c01\u88c5\u4e86\u4e00\u4e2asock_def_wakeup<\/code>\u63a5\u53e3\u7528\u4e8e\u8c03\u7528<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"
                    \u53c2\u8003\u6587\u6863\uff1a \u3010\u539f\u521b\u3011Linux select\/poll\u673a\u5236\u539f\u7406\u5206\u6790 – LoyenWang &#8 […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_import_markdown_pro_load_document_selector":0,"_import_markdown_pro_submit_text_textarea":"","footnotes":""},"categories":[6,1],"tags":[],"class_list":["post-215","post","type-post","status-publish","format-standard","hentry","category-linux-knowledge","category-source-code-analysis"],"_links":{"self":[{"href":"https:\/\/www.garfield-blog.top\/index.php?rest_route=\/wp\/v2\/posts\/215","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.garfield-blog.top\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.garfield-blog.top\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.garfield-blog.top\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.garfield-blog.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=215"}],"version-history":[{"count":3,"href":"https:\/\/www.garfield-blog.top\/index.php?rest_route=\/wp\/v2\/posts\/215\/revisions"}],"predecessor-version":[{"id":287,"href":"https:\/\/www.garfield-blog.top\/index.php?rest_route=\/wp\/v2\/posts\/215\/revisions\/287"}],"wp:attachment":[{"href":"https:\/\/www.garfield-blog.top\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=215"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.garfield-blog.top\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=215"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.garfield-blog.top\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=215"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}