io_uring_for_each_cqe(3) liburing Manual io_uring_for_each_cqe(3)

io_uring_for_each_cqe - iterate pending completion events

#include <liburing.h>
io_uring_for_each_cqe(struct io_uring *ring,
                      unsigned head,
                      struct io_uring_cqe *cqe) { }

The io_uring_for_each_cqe(3) is a macro helper that iterates completion events belonging to the ring using head as a temporary iterator, and points cqe to each pending event when iterating.

This helper provides an efficient way to iterate all pending events in the ring, and then advancing the CQ ring by calling io_uring_cq_advance(3) with the number of CQEs consumed when done. As updating the kernel visible CQ ring state involves an ordered write, doing it once for a number of events is more efficient than handling each completion separately and calling io_uring_cqe_seen(3) for each of them.

void handle_cqes(struct io_uring *ring)
	struct io_uring_cqe *cqe;
	unsigned head;
	unsigned i = 0;
	io_uring_for_each_cqe(ring, head, cqe) {
		/* handle completion */
		printf("cqe: %d\n", cqe->res);
	io_uring_cq_advance(ring, i);


io_uring_wait_cqe_timeout(3), io_uring_wait_cqe(3), io_uring_wait_cqes(3), io_uring_cqe_seen(3), io_uring_buf_ring_cq_advance(3)

June 4, 2023 liburing-2.4