xref: /freebsd/share/man/man9/psignal.9 (revision 7ef62cebc2f965b0f640263e179276928885e33d)
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28.\"	$NetBSD: psignal.9,v 1.1 1996/06/22 22:57:35 pk Exp $
29.\" $FreeBSD$
30.\"
31.Dd July 14, 2023
32.Dt PSIGNAL 9
33.Os
34.Sh NAME
35.Nm psignal ,
36.Nm kern_psignal ,
37.Nm pgsignal ,
38.Nm tdsignal
39.Nd post signal to a thread, process, or process group
40.Sh SYNOPSIS
41.In sys/types.h
42.In sys/signalvar.h
43.Ft void
44.Fn kern_psignal "struct proc *p" "int signum"
45.Ft void
46.Fn pgsignal "struct pgrp *pgrp" "int signum" "int checkctty"
47.Ft void
48.Fn tdsignal "struct thread *td" "int signum"
49.Sh DESCRIPTION
50These functions post a signal to a thread or one or more processes.
51The argument
52.Fa signum
53common to all three functions should be in the range
54.Bq 1- Ns Dv NSIG .
55.Pp
56The
57.Fn kern_psignal
58function posts signal number
59.Fa signum
60to the process represented by the process structure
61.Fa p .
62The
63.Fn kern_psignal
64function used to be called
65.Fn psignal
66but was renamed in order to eliminate a name collision with the libc
67function of that name and facilitate code reuse.
68With a few exceptions noted below, the target process signal disposition is
69updated and is marked as runnable, so further handling of the signal is done
70in the context of the target process after a context switch.
71Note that
72.Fn kern_psignal
73does not by itself cause a context switch to happen.
74.Pp
75The target process is not marked as runnable in the following cases:
76.Bl -bullet -offset indent
77.It
78The target process is sleeping uninterruptibly.
79The signal will be
80noticed when the process returns from the system call or trap.
81.It
82The target process is currently ignoring the signal.
83.It
84If a stop signal is sent to a sleeping process that takes the
85default action
86(see
87.Xr sigaction 2 ) ,
88the process is stopped without awakening it.
89.It
90.Dv SIGCONT
91restarts a stopped process
92(or puts them back to sleep)
93regardless of the signal action
94(e.g., blocked or ignored).
95.El
96.Pp
97If the target process is being traced
98.Fn kern_psignal
99behaves as if the target process were taking the default action for
100.Fa signum .
101This allows the tracing process to be notified of the signal.
102.Pp
103The
104.Fn pgsignal
105function posts signal number
106.Fa signum
107to each member of the process group described by
108.Fa pgrp .
109If
110.Fa checkctty
111is non-zero, the signal will be posted only to processes that have
112a controlling terminal.
113.Fn pgsignal
114is implemented by walking along the process list headed by the field
115.Li pg_members
116of the process group structure
117pointed at by
118.Fa pgrp
119and calling
120.Fn kern_psignal
121as appropriate.
122If
123.Fa pgrp
124is
125.Dv NULL
126no action is taken.
127.Pp
128The
129.Fn tdsignal
130function posts signal number
131.Fa signum
132to the thread represented by the thread structure
133.Fa td .
134.Sh SEE ALSO
135.Xr sigaction 2 ,
136.Xr signal 9 ,
137.Xr tsleep 9
138.Sh HISTORY
139The
140.Fn psignal
141function was renamed to
142.Fn kern_psignal
143in
144.Fx 9.0 .
145