io_uring_prep_poll_add(3) liburing Manual io_uring_prep_poll_add(3)

io_uring_prep_poll_add - prepare a poll request

#include <poll.h>
#include <liburing.h>
void io_uring_prep_poll_add(struct io_uring_sqe *sqe,
                            int fd,
                            unsigned poll_mask);
void io_uring_prep_poll_multishot(struct io_uring_sqe *sqe,
                                  int fd,
                                  unsigned poll_mask);

The io_uring_prep_poll_add(3) function prepares a poll request. The submission queue entry sqe is setup to use the file descriptor fd that should get polled, with the events desired specified in the poll_mask argument.

The default behavior is a single-shot poll request. When the specified event has triggered, a completion CQE is posted and no more events will be generated by the poll request. io_uring_prep_poll_multishot(3) behaves identically in terms of events, but it persist across notifications and will repeatedly post notifications for the same registration. A CQE posted from a multishot poll request will have IORING_CQE_F_MORE set in the CQE flags member, indicating that the application should expect more completions from this request. If the multishot poll request gets terminated or experiences an error, this flag will not be set in the CQE. If this happens, the application should not expect further CQEs from the original request and must reissue a new one if it still wishes to get notifications on this file descriptor.


The CQE res field will contain the result of the operation, which is a bitmask of the events notified. See the poll(2) man page for details. Note that where synchronous system calls will return -1 on failure and set errno to the actual error value, io_uring never uses errno. Instead it returns the negated errno directly in the CQE res field.

io_uring_get_sqe(3), io_uring_submit(3), poll(2), epoll_ctl(3)

March 12, 2022 liburing-2.2