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.\" Copyright (C) 2022 Jens Axboe <axboe@kernel.dk>
.\"
.\" SPDX-License-Identifier: LGPL-2.0-or-later
.\"
.TH io_uring_prep_poll_timeout_update 3 "March 12, 2022" "liburing-2.2" "liburing Manual"
.SH NAME
io_uring_prep_timeoute_update - prepare a request to update an existing timeout
.fi
.SH SYNOPSIS
.nf
.BR "#include <liburing.h>"
.PP
.BI "void io_uring_prep_timeout_update(struct io_uring_sqe *" sqe ","
.BI "                                  struct __kernel_timespec *" ts ","
.BI "                                  __u64 " user_data ","
.BI "                                  unsigned " flags ");"
.BI "
.BI "void io_uring_prep_timeout_remove(struct io_uring_sqe *" sqe ","
.BI "                                  __u64 " user_data ","
.BI "                                  unsigned " flags ");"
.PP
.SH DESCRIPTION
.PP
These functions modify or cancel an existing timeout request. The submission
queue entry
.I sqe
is setup to arm a timeout update or removal specified by
.I user_data
and with modifier flags given by
.I flags.
Additionally, the update request includes a
.I ts
structure, which contains new timeout information.

For an update request, the
.I flags
member may contain a bitmask of the following values:
.TP
.B IORING_TIMEOUT_ABS
The value specified in
.I ts
is an absolute value rather than a relative one.
.TP
.B IORING_TIMEOUT_BOOTTIME
The boottime clock source should be used.
.TP
.B IORING_TIMEOUT_REALTIME
The realtime clock source should be used.
.TP
.B IORING_TIMEOUT_ETIME_SUCCESS
Consider an expirted timeout a success in terms of the posted completion.
Normally a timeout that triggers would return in a
.B -ETIME
CQE
.I res
value.
.PP

.SH RETURN VALUE
None
.SH ERRORS
These are the errors that are reported in the CQE
.I res
field. On success,
.B 0
is returned.
.TP
.B -ENOENT
The timeout identified by
.I user_data
could not be found. It may be invalid, or triggered before the update or
removal request was processed.
.TP
.B -EALREADY
The timeout identified by
.I user_data
is already firing and cannot be canceled.
.TP
.B -EINVAL
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.
.TP
.B -EFAULT
io_uring was unable to access the data specified by
.I ts.
.SH NOTES
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
.B IORING_FEAT_SUBMIT_STABLE
flag passed back from
.BR io_uring_queue_init_params (3).
.SH SEE ALSO
.BR io_uring_get_sqe (3), io_uring_submit (3), io_uring_prep_timeout (3)