oracular (3) io_uring_prep_timeout.3.gz

NAME

       io_uring_prep_timeout - 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)