PollFlags

IORING_POLL_ADD_MULTI - Multishot poll. Sets IORING_CQE_F_MORE if the poll handler will continue to report CQEs on behalf of the same SQE.

The default io_uring poll mode is one-shot, where once the event triggers, the poll command is completed and won't trigger any further events. If we're doing repeated polling on the same file or socket, then it can be more efficient to do multishot, where we keep triggering whenever the event becomes true.

This deviates from the usual norm of having one CQE per SQE submitted. Add a CQE flag, IORING_CQE_F_MORE, which tells the application to expect further completion events from the submitted SQE. Right now the only user of this is POLL_ADD in multishot mode.

An application should expect more CQEs for the specificed SQE if the CQE is flagged with IORING_CQE_F_MORE. In multishot mode, only cancelation or an error will terminate the poll request, in which case the flag will be cleared.

Note: available from Linux 5.13

IORING_POLL_UPDATE_EVENTS

Update existing poll request, matching sqe->addr as the old user_data field.

Note: available from Linux 5.13

IORING_POLL_UPDATE_USER_DATA

Update existing poll request, matching sqe->addr as the old user_data field.

Note: available from Linux 5.13