#POSIX Polling — epoll Backend

#define FIO_POLL_ENGINE_EPOLL
#define FIO_POLL
#include "fio-stl.h"

Implementation of the portable polling API on top of Linux epoll. Normally selected automatically on Linux; define FIO_POLL_ENGINE_EPOLL to force it.

The public API is documented in 102 poll api.md. This file describes backend-specific behavior.

#Backend Details

#struct fio_poll_s

struct fio_poll_s {
  fio_poll_settings_s settings;
  struct pollfd fds[2];
  int fd[2];
};

Two internal epoll file descriptors are used: one for POLLOUT readiness and one for POLLIN/error events. A pollfd pair wakes the internal poll used to wait on both epoll FDs at once.

#fio_poll_engine

Returns "epoll".

#Fork Safety

A state callback re-creates the epoll FDs in the child process after fork.

#Notes

• Events are monitored in one-shot mode (EPOLLONESHOT). After an event fires, the descriptor must be re-armed with fio_poll_monitor.
• Error and hang-up events are dispatched through the read-side epoll FD and delivered to on_close.
• EPOLLRDHUP and EPOLLHUP are always included in the monitored events.