.\" Copyright (C) 2021 Stefan Roesch <shr@fb.com>
.\"
.\" SPDX-License-Identifier: LGPL-2.0-or-later
.\"
.TH io_uring_wait_cqes 3 "November 15, 2021" "liburing-2.1" "liburing Manual"
.SH NAME
io_uring_wait_cqes \- wait for one or more io_uring completion events
.SH SYNOPSIS
.nf
.B #include <liburing.h>
.PP
.BI "int io_uring_wait_cqes(struct io_uring *" ring ","
.BI "                       struct io_uring_cqe **" cqe_ptr ","
.BI "                       unsigned " wait_nr ","
.BI "                       struct __kernel_timespec *" ts ","
.BI "                       sigset_t *" sigmask ");
.fi
.SH DESCRIPTION
.PP
The
.BR io_uring_wait_cqes (3)
function returns
.I wait_nr
IO completions from the queue belonging to the
.I ring
param, waiting for them if necessary or until the timeout
.I ts
expires.
.PP
The
.I sigmask
specifies the set of signals to block. If set, it is equivalent to atomically
executing the following calls:
.PP
.in +4n
.EX
sigset_t origmask;

pthread_sigmask(SIG_SETMASK, &sigmask, &origmask);
ret = io_uring_wait_cqes(ring, cqe, wait_nr, ts, NULL);
pthread_sigmask(SIG_SETMASK, &origmask, NULL);
.EE
.in
.PP
The
.I cqe_ptr
param is filled in on success with the first CQE. Callers of this function
should use
.BR io_uring_for_each_cqe (3)
to iterate all available CQEs.

If
.I ts
is specified and an older kernel without
.B IORING_FEAT_EXT_ARG
is used, the application does not need to call
.BR io_uring_submit (3)
before calling
.BR io_uring_wait_cqes (3).
For newer kernels with that feature flag set, there is no implied submit
when waiting for a request.

.SH RETURN VALUE
On success
.BR io_uring_wait_cqes (3)
returns 0 and the cqe_ptr param is filled in. On failure it returns
.BR -errno .
.SH SEE ALSO
.BR io_uring_submit (3),
.BR io_uring_for_each_cqe (3),
.BR io_uring_wait_cqe_timeout (3),
.BR io_uring_wait_cqe (3)