NAME

       io_uring_prep_timeoute - prepare a timeout request

SYNOPSIS

       #include <liburing.h>

       void io_uring_prep_timeout(struct io_uring_sqe *sqe,
                                  struct __kernel_timespec *ts,
                                  unsigned count,
                                  unsigned flags);

DESCRIPTION

       The  io_uring_prep_timeout(3)  function  prepares  a timeout request. The submission queue
       entry sqe is setup to arm a timeout specified by ts and with  a  timeout  count  of  count
       completion entries. The flags argument holds modifier flags for the request.

       This  request  type  can  be used as a timeout waking anyone sleeping for events on the CQ
       ring. The flags argument may contain:

       IORING_TIMEOUT_ABS
              The value specified in ts is an absolute value rather than a relative one.

       IORING_TIMEOUT_BOOTTIME
              The boottime clock source should be used.

       IORING_TIMEOUT_REALTIME
              The realtime clock source should be used.

       IORING_TIMEOUT_ETIME_SUCCESS
              Consider an expired timeout a success in terms of the posted completion.   Normally
              a timeout that triggers would return in a -ETIME CQE res value.

       IORING_TIMEOUT_MULTISHOT
              The   request  will  return  multiple  timeout  completions.  The  completion  flag
              IORING_CQE_F_MORE is set if more timeouts are  expected.  The  value  specified  in
              count  is  the  number of repeats. A value of 0 means the timeout is indefinite and
              can only be stopped by a removal request. Available since the 6.4 kernel.

       The timeout completion event will trigger if either the specified timeout has occurred, or
       the specified number of events to wait for have been posted to the CQ ring.

RETURN VALUE

       None

ERRORS

       These are the errors that are reported in the CQE res field. On success, 0 is returned.

       -ETIME The specified timeout occurred and triggered the completion event.

       -EINVAL
              One  of  the fields set in the SQE was invalid. For example, two clocksources where
              given, or the specified timeout seconds or nanoseconds where < 0.

       -EFAULT
              io_uring was unable to access the data specified by ts.

       -ECANCELED
              The timeout was canceled by a removal request.

NOTES

       As with any request that passes in data in a struct, that data must remain valid until the
       request has been successfully submitted. It need not remain valid until completion. Once a
       request has been submitted, the in-kernel state is stable. Very  early  kernels  (5.4  and
       earlier)  required state to be stable until the completion occurred. Applications can test
       for this behavior by  inspecting  the  IORING_FEAT_SUBMIT_STABLE  flag  passed  back  from
       io_uring_queue_init_params(3).

SEE ALSO

       io_uring_get_sqe(3),          io_uring_submit(3),         io_uring_prep_timeout_remove(3),
       io_uring_prep_timeout_update(3)