---
name: "io_uring_prep_poll_update"
section: "3"
platform: "linux"
package: "liburing"
version: "2.15-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/io_uring_prep_poll_update"
---

# io\_uring\_prep\_poll\_update(3)

update an existing poll request

## NAME

io\_uring\_prep\_poll\_update - update an existing poll request

## SYNOPSIS

```
#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***);**

## DESCRIPTION

The [**io\_uring\_prep\_poll\_update**(3)](/io_uring_prep_poll_update/3.md) 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:

- **IORING\_POLL\_UPDATE\_EVENTS**

  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.

- **IORING\_POLL\_UPDATE\_USER\_DATA**

  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.

- **IORING\_POLL\_ADD\_MULTI**

  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.

## RETURN VALUE

None

## ERRORS

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

- **-ENOENT**

  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.

- **-EINVAL**

  One of the fields set in the SQE was invalid.

- **-EALREADY**

  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.

- **-ECANCELED**

  **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.

## SEE ALSO

[**io\_uring\_get\_sqe**(3)](/io_uring_get_sqe/3.md), [**io\_uring\_submit**(3)](/io_uring_submit/3.md), [**io\_uring\_prep\_poll\_add**(3)](/io_uring_prep_poll_add/3.md), [**io\_uring\_prep\_poll\_multishot**(3)](/io_uring_prep_poll_multishot/3.md)