.\"	$NetBSD: curlwp_bind.9,v 1.3 2026/01/01 01:12:52 uwe Exp $
.\"
.\" Copyright (c) 2025 The NetBSD Foundation
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
.\" ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
.\" TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
.\" PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
.\" BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
.\" CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
.\" SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
.\" INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
.\" CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
.\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
.\" POSSIBILITY OF SUCH DAMAGE.
.\"
.Dd December 31, 2025
.Dt CURLWP_BIND 9
.Os
.Sh NAME
.Nm curlwp_bind ,
.Nm curlwp_bindx
.Nd temporarily bind the current thread to the running CPU
.Sh SYNOPSIS
.In sys/lwp.h
.Ft int
.Fn curlwp_bind "void"
.Ft void
.Fn curlwp_bindx "int bound"
.Sh DESCRIPTION
.Fn curlwp_bind
temporarily binds the current thread to the running CPU and returns a
cookie
.Fa bound
which must be passed to
.Fn curlwp_bindx
when done.
.Pp
During this time, the thread may sleep and may be preempted, but it
will never migrate to another CPU until
.Fn curlwp_bindx .
If the CPU is offlined, the thread will not run again until the CPU is
onlined again.
.Pp
Calls to
.Fn curlwp_bind
and
.Fn curlwp_bindx
may be nested as long as the matching cookie is passed.
.Sh EXAMPLES
For temporary access to resources protected by
.Xr psref 9
from an arbitrary thread:
.Bd -literal -offset indent
struct psref psref;
int bound, s;

bound = curlwp_bind();
s = pserialize_read_enter();
IFADDR_READER_FOREACH(ifa, ifp) {
        ifa_acquire(ifa, &psref);
        pserialize_read_exit(s);

        /*
         * ifa is now stable, even if caller is preempted
         * or sleeps
         */

        s = pserialize_read_enter();
        ifa_release(ifa, &psref);
}
pserialize_read_exit(s);
curlwp_bindx(bound);
.Ed
.Sh CODE REFERENCES
.Pa sys/sys/lwp.h
.Sh SEE ALSO
.Xr localcount 9 ,
.Xr pserialize 9 ,
.Xr psref 9 ,
.Xr spl 9
.Sh HISTORY
The
.Nm
function first appeared in
.Nx 8.0
to support
.Xr psref 9 .