io_uring_prep_epoll_wait(3) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | SEE ALSO | COLOPHON

io_uring_prep_epoll_wait(3)  liburing Manual  io_uring_prep_epoll_wait(3)

NAME         top

       io_uring_prep_epoll_wait - prepare an epoll wait request

SYNOPSIS         top

       #include <sys/epoll.h>
       #include <liburing.h>

       void io_uring_prep_epoll_wait(struct io_uring_sqe *sqe,
                                     int fd,
                                     struct epoll_event *events,
                                     int maxevents,
                                     unsigned flags );"

DESCRIPTION         top

       The io_uring_prep_epoll_wait(3) function prepares an epoll_wait
       request. The submission queue entry sqe is setup to wait on a
       maximum of maxevents events on the epoll file descriptor indicated
       by fd, and filling the received events into the memory pointed to
       by events.

       This function prepares an async epoll_wait(2) request. See that
       man page for details. The use case is mostly for legacy event
       loops, where certain file descriptors may still be using epoll for
       readiness notifications. Normally this would necessitate using
       epoll_wait with the io_uring fd added to that set as well, which
       is suboptimal as epoll doesn't provide the same kind of fine
       grained batch control and wakeup reductions that io_uring does. By
       using io_uring to read epoll events, the event loop can be
       entirely switched to io_uring, and reap the benefits of batch
       waiting and context switch reductions.

RETURN VALUE         top

       None

ERRORS         top

       The CQE res field will contain the result of the operation. See
       the related man page for details on possible values. Note that
       where synchronous system calls will return -1 on failure and set
       errno to the actual error value, io_uring never uses errno.
       Instead it returns the negated errno directly in the CQE res
       field.

SEE ALSO         top

       io_uring_get_sqe(3), io_uring_submit(3), epoll_wait(2)

COLOPHON         top

       This page is part of the liburing (A library for io_uring)
       project.  Information about the project can be found at 
       ⟨https://github.com/axboe/liburing⟩.  If you have a bug report for
       this manual page, send it to [email protected].  This page
       was obtained from the project's upstream Git repository
       ⟨https://github.com/axboe/liburing⟩ on 2025-08-11.  (At that time,
       the date of the most recent commit that was found in the
       repository was 2025-08-02.)  If you discover any rendering
       problems in this HTML version of the page, or you believe there is
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       (which is not part of the original manual page), send a mail to
       [email protected]

liburing-2.10                 March 6, 2025   io_uring_prep_epoll_wait(3)

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