io_uring_prep_poll_update(3) liburing Manual io_uring_prep_poll_update(3)

io_uring_prep_poll_update - update an existing poll request

#include <poll.h>
#include <liburing.h>
void io_uring_prep_poll_update(struct io_uring_sqe *sqe,
                               __u64 old_user_data,
                               __u64 new_user_data,
                               unsigned poll_mask,
                               unsigned flags);

The io_uring_prep_poll_update(3) function prepares a poll update request. The submission queue entry sqe is setup to update a poll request identified by old_user_data, replacing it with the new_user_data information. The poll_mask arguments contains the new mask to use for the poll request, and flags argument contains modifier flags telling io_uring what fields to update.

The flags modifier flags is a bitmask and may contain and OR'ed mask of:

If set, the poll update request will replace the existing events being waited for with the ones specified in the poll_mask argument to the function. Note that only the lower 16 bits of events can be updated. This includes things like EPOLLIN and EPOLLOUT . Higher order masks/settings are included as internal state, and cannot be modified. That includes settings like EPOLLONESHOT , EPOLLEXCLUSIVE , and EPOLLET . If an application wishes to modify these, it must cancel/remove the existing poll request and arm a new one.
If set, the poll update request will update the existing user_data of the request with the value passed in as the new_user_data argument.
If set, this will change the poll request from a singleshot to a multishot request. This must be used along with IORING_POLL_UPDATE_EVENTS as the event field must be updated to enable multishot.


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

The request identified by user_data could not be located. This could be because it completed before the cancelation request was issued, or if an invalid identifier is used.
One of the fields set in the SQE was invalid.
The execution state of the request has progressed far enough that cancelation is no longer possible. This should normally mean that it will complete shortly, either successfully, or interrupted due to the cancelation.
IORING_POLL_UPDATE_EVENTS was set and an error occurred re-arming the poll request with the new mask. The original poll request is terminated if this happens, and that termination CQE will contain the reason for the error re-arming.

io_uring_get_sqe(3), io_uring_submit(3), io_uring_prep_poll_add(3), io_uring_prep_poll_multishot(3)

March 12, 2022 liburing-2.2