refactor epoll related implementation (#1128)

* Refactor epoll related implementation

Add PollableInode trait
Implement PollableInode for pollable inodes

fix https://github.com/DragonOS-Community/DragonOS/issues/1094

Signed-off-by: Godones <chenlinfeng25@outlook.com>

user/apps/test_epoll/main.c

@@ -0,0 +1,129 @@
+#include <errno.h>
+#include <pthread.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/epoll.h>
+#include <sys/eventfd.h>
+#include <unistd.h>
+
+#define MAX_EVENTS 10
+
+static int efd;  // eventfd 描述符
+static int efd2; // eventfd 描述符
+
+// 工作线程：等待2秒后向 eventfd 写入事件通知
+void *worker_thread(void *arg) {
+  uint64_t u = 1;
+  printf("工作线程：等待2秒后发送事件通知...\n");
+  sleep(2); // 模拟耗时任务
+  printf("工作线程：发送事件通知...\n");
+  if (write(efd, &u, sizeof(u)) != sizeof(u)) {
+    perror("工作线程写入 eventfd 出错");
+    exit(EXIT_FAILURE);
+  }
+  printf("工作线程：事件通知已发送\n");
+  return NULL;
+}
+
+int main() {
+  int epoll_fd;
+  struct epoll_event ev, events[MAX_EVENTS];
+  int nfds;
+  pthread_t tid;
+
+  // 创建 eventfd，对象初始计数为 0
+  efd = eventfd(0, 0);
+  if (efd == -1) {
+    perror("创建 eventfd 失败");
+    exit(EXIT_FAILURE);
+  } else {
+    printf("创建 eventfd 成功，描述符 = %d\n", efd);
+  }
+
+  efd2 = dup(efd); // 复制 eventfd 描述符
+  if (efd2 == -1) {
+    perror("复制 eventfd 失败");
+    close(efd);
+    exit(EXIT_FAILURE);
+  } else {
+    printf("复制 eventfd 成功，描述符 = %d\n", efd2);
+  }
+
+  // 创建 epoll 实例
+  epoll_fd = epoll_create1(0);
+  if (epoll_fd == -1) {
+    perror("创建 epoll 实例失败");
+    close(efd);
+    exit(EXIT_FAILURE);
+  }
+
+  // 将 eventfd 添加到 epoll 监听队列，关注可读事件
+  ev.events = EPOLLIN;
+  ev.data.fd = efd;
+  if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, efd, &ev) == -1) {
+    perror("epoll_ctl 添加 eventfd 失败");
+    close(efd);
+    close(epoll_fd);
+    exit(EXIT_FAILURE);
+  }
+
+  // 将复制的 eventfd 添加到 epoll 监听队列，关注可读事件
+  ev.data.fd = efd2;
+  if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, efd2, &ev) == -1) {
+    perror("epoll_ctl 添加复制的 eventfd 失败");
+    close(efd);
+    close(efd2);
+    close(epoll_fd);
+    exit(EXIT_FAILURE);
+  }
+
+  // 创建工作线程，模拟事件发生
+  if (pthread_create(&tid, NULL, worker_thread, NULL) != 0) {
+    perror("创建工作线程失败");
+    close(efd);
+    close(efd2);
+    close(epoll_fd);
+    exit(EXIT_FAILURE);
+  }
+
+  printf("主线程：使用 epoll_wait 等待事件...\n");
+
+  // 阻塞等待事件发生
+  nfds = epoll_wait(epoll_fd, events, MAX_EVENTS, -1);
+  if (nfds == -1) {
+    perror("epoll_wait 失败");
+    exit(EXIT_FAILURE);
+  } else {
+    printf("主线程：epoll_wait 返回，事件数量 = %d\n", nfds);
+  }
+
+  // 处理就绪事件
+  //   for (int i = 0; i < nfds; i++) {
+  //     if (events[i].data.fd == efd || events[i].data.fd == efd2) {
+  //       uint64_t count;
+  //       int fd = events[i].data.fd;
+  //       printf("主线程：事件发生在 fd = %d\n", fd);
+  //       if (read(fd, &count, sizeof(count)) != sizeof(count)) {
+  //         perror("从 eventfd 读取失败");
+  //         exit(EXIT_FAILURE);
+  //       }
+  //       printf("主线程：接收到 eventfd 事件，计数值 = %lu\n", count);
+  //     }
+  //   }
+
+  // 等待工作线程结束
+  pthread_join(tid, NULL);
+
+  int r = close(epoll_fd);
+  if (r == -1) {
+    perror("关闭 epoll 实例失败");
+    exit(EXIT_FAILURE);
+  } else {
+    printf("关闭 epoll 实例成功\n");
+  }
+  close(efd);
+  close(efd2); // 关闭复制的 eventfd 描述符
+  printf("test_epoll ok\n");
+  return 0;
+}