io_uring_prep_poll_timeout_update(3) liburing Manual io_uring_prep_poll_timeout_update(3)

io_uring_prep_timeout_update - prepare a request to update an existing timeout

#include <liburing.h>
void io_uring_prep_timeout_update(struct io_uring_sqe *sqe,
                                  struct __kernel_timespec *ts,
                                  __u64 user_data,
                                  unsigned flags);
void io_uring_prep_timeout_remove(struct io_uring_sqe *sqe,
                                  __u64 user_data,
                                  unsigned flags);

These functions modify or cancel an existing timeout request. The submission queue entry sqe is setup to arm a timeout update or removal specified by user_data and with modifier flags given by flags. Additionally, the update request includes a ts structure, which contains new timeout information.

For an update request, the flags member may contain a bitmask of the following values:

The value specified in ts is an absolute value rather than a relative one.
The boottime clock source should be used.
The realtime clock source should be used.
Consider an expired timeout a success in terms of the posted completion. Normally a timeout that triggers would return in a -ETIME CQE res value.

The timeout remove command does not currently accept any flags.


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

The timeout identified by user_data could not be found. It may be invalid, or triggered before the update or removal request was processed.
The timeout identified by user_data is already firing and cannot be canceled.
One of the fields set in the SQE was invalid. For example, two clocksources where given, or the specified timeout seconds or nanoseconds where < 0.
io_uring was unable to access the data specified by ts.

As with any request that passes in data in a struct, that data must remain valid until the request has been successfully submitted. It need not remain valid until completion. Once a request has been submitted, the in-kernel state is stable. Very early kernels (5.4 and earlier) required state to be stable until the completion occurred. Applications can test for this behavior by inspecting the IORING_FEAT_SUBMIT_STABLE flag passed back from io_uring_queue_init_params(3).

io_uring_get_sqe(3), io_uring_submit(3), io_uring_prep_timeout(3)

March 12, 2022 liburing-2.2