.\"	$OpenBSD: psignal.9,v 1.8 2022/03/31 17:27:23 naddy Exp $
.\"	$NetBSD: psignal.9,v 1.5 1999/03/16 00:40:47 garbled Exp $
.\"
.\" Copyright (c) 1996 The NetBSD Foundation, Inc.
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.\"
.\" This code is derived from software contributed to The NetBSD Foundation
.\" by Paul Kranenburg.
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.Dd $Mdocdate: March 31 2022 $
.Dt PSIGNAL 9
.Os
.Sh NAME
.Nm psignal ,
.Nm pgsignal ,
.Nm pgsigio
.Nd post signal to a process
.Sh SYNOPSIS
.Ft void
.Fn psignal "struct proc *p" "int signum"
.Ft void
.Fn pgsignal "struct pgrp *pgrp" "int signum" "int checkctty"
.Ft void
.Fn pgsigio "struct sigio_ref *sir" "int sigum" "int checkctty"
.Sh DESCRIPTION
These functions post a signal to 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 psignal
function posts signal number
.Fa signum
to the process represented by the process structure
.Fa p .
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 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
.Pq see Xr sigaction 2 ,
the process is stopped without awakening it.
.It
.Dv SIGCONT
restarts a stopped process
.Pq or puts them back to sleep
regardless of the signal action
.Pq e.g., blocked or ignored .
.El
.Pp
If the target process is being traced,
.Fn 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.
If
.Fa pgrp
is
.Dv NULL ,
no action is taken.
.Pp
The
.Fn pgsigio
function posts signal number
.Fa signum
to the process or each member of the process group indicated by reference
.Fa sir .
If
.Fa checkctty
is non-zero, the signal will be posted only to processes that have
a controlling terminal.
.Sh CODE REFERENCES
These functions are implemented in the file
.Pa sys/kern/kern_sig.c .
.Sh SEE ALSO
.Xr sigaction 2 ,
.Xr sigio_setown 9 ,
.Xr tsleep 9