.\" Copyright (c) 1996 The NetBSD Foundation, Inc.
.\" All rights reserved.
.\"
.\" This code is derived from software contributed to The NetBSD Foundation
.\" by Paul Kranenburg.
.\"
.\" 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 REGENTS 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.
.\"
.\"	$NetBSD: psignal.9,v 1.1 1996/06/22 22:57:35 pk Exp $
.\" $FreeBSD$
.\"
.Dd July 14, 2023
.Dt PSIGNAL 9
.Os
.Sh NAME
.Nm psignal ,
.Nm kern_psignal ,
.Nm pgsignal ,
.Nm tdsignal
.Nd post signal to a thread, process, or process group
.Sh SYNOPSIS
.In sys/types.h
.In sys/signalvar.h
.Ft void
.Fn kern_psignal "struct proc *p" "int signum"
.Ft void
.Fn pgsignal "struct pgrp *pgrp" "int signum" "int checkctty"
.Ft void
.Fn tdsignal "struct thread *td" "int signum"
.Sh DESCRIPTION
These functions post a signal to a thread or one or more processes.
The argument
.Fa signum
common to all three functions should be in the range
.Bq 1- Ns Dv NSIG .
.Pp
The
.Fn kern_psignal
function posts signal number
.Fa signum
to the process represented by the process structure
.Fa p .
The
.Fn kern_psignal
function used to be called
.Fn psignal
but was renamed in order to eliminate a name collision with the libc
function of that name and facilitate code reuse.
With a few exceptions noted below, the target process signal disposition is
updated and is marked as runnable, so further handling of the signal is done
in the context of the target process after a context switch.
Note that
.Fn kern_psignal
does not by itself cause a context switch to happen.
.Pp
The target process is not marked as runnable in the following cases:
.Bl -bullet -offset indent
.It
The target process is sleeping uninterruptibly.
The signal will be
noticed when the process returns from the system call or trap.
.It
The target process is currently ignoring the signal.
.It
If a stop signal is sent to a sleeping process that takes the
default action
(see
.Xr sigaction 2 ) ,
the process is stopped without awakening it.
.It
.Dv SIGCONT
restarts a stopped process
(or puts them back to sleep)
regardless of the signal action
(e.g., blocked or ignored).
.El
.Pp
If the target process is being traced
.Fn kern_psignal
behaves as if the target process were taking the default action for
.Fa signum .
This allows the tracing process to be notified of the signal.
.Pp
The
.Fn pgsignal
function posts signal number
.Fa signum
to each member of the process group described by
.Fa pgrp .
If
.Fa checkctty
is non-zero, the signal will be posted only to processes that have
a controlling terminal.
.Fn pgsignal
is implemented by walking along the process list headed by the field
.Li pg_members
of the process group structure
pointed at by
.Fa pgrp
and calling
.Fn kern_psignal
as appropriate.
If
.Fa pgrp
is
.Dv NULL
no action is taken.
.Pp
The
.Fn tdsignal
function posts signal number
.Fa signum
to the thread represented by the thread structure
.Fa td .
.Sh SEE ALSO
.Xr sigaction 2 ,
.Xr signal 9 ,
.Xr tsleep 9
.Sh HISTORY
The
.Fn psignal
function was renamed to
.Fn kern_psignal
in
.Fx 9.0 .