447 lines
9.5 KiB
Groff
447 lines
9.5 KiB
Groff
.\"
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.\" Copyright (C) 2002 Chad David <davidc@FreeBSD.org>. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice(s), this list of conditions and the following disclaimer as
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.\" the first lines of this file unmodified other than the possible
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.\" addition of one or more copyright notices.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice(s), this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
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.\" EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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.\" WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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.\" DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY
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.\" DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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.\" (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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.\" SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
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.\" CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
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.\" DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd November 20, 2004
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.Dt SIGNAL 9
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.Os
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.Sh NAME
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.Nm signal ,
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.Nm SIGADDSET ,
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.Nm SIGDELSET ,
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.Nm SETEMPTYSET ,
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.Nm SIGFILLSET ,
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.Nm SIGISMEMBER ,
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.Nm SIGISEMPTY ,
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.Nm SIGNOTEMPTY ,
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.Nm SIGSETEQ ,
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.Nm SIGSETNEQ ,
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.Nm SIGSETOR ,
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.Nm SIGSETAND ,
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.Nm SIGSETNAND ,
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.Nm SIGSETCANTMASK ,
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.Nm SIG_STOPSIGMASK ,
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.Nm SIG_CONTSIGMASK ,
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.Nm SIGPENDING ,
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.Nm cursig ,
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.Nm execsigs ,
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.Nm issignal ,
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.Nm killproc ,
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.Nm pgsigio ,
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.Nm postsig ,
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.Nm sigexit ,
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.Nm siginit ,
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.Nm signotify ,
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.Nm trapsignal
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.Nd "kernel signal functions"
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.Sh SYNOPSIS
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.In sys/param.h
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.In sys/proc.h
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.In sys/signalvar.h
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.Ft void
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.Fn SIGADDSET "sigset_t set" "int signo"
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.Ft void
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.Fn SIGDELSET "sigset_t set" "int signo"
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.Ft void
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.Fn SIGEMPTYSET "sigset_t set"
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.Ft void
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.Fn SIGFILLSET "sigset_t set"
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.Ft int
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.Fn SIGISMEMBER "sigset_t set" "int signo"
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.Ft int
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.Fn SIGISEMPTY "sigset_t set"
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.Ft int
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.Fn SIGNOTEMPTY "sigset_t set"
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.Ft int
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.Fn SIGSETEQ "sigset_t set1" "sigset_t set2"
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.Ft int
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.Fn SIGSETNEQ "sigset_t set1" "sigset_t set2"
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.Ft void
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.Fn SIGSETOR "sigset_t set1" "sigset_t set2"
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.Ft void
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.Fn SIGSETAND "sigset_t set1" "sigset_t set2"
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.Ft void
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.Fn SIGSETNAND "sigset_t set1" "sigset_t set2"
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.Ft void
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.Fn SIG_CANTMASK "sigset_t set"
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.Ft void
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.Fn SIG_STOPSIGMASK "sigset_t set"
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.Ft void
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.Fn SIG_CONTSIGMASK "sigset_t set"
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.Ft int
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.Fn SIGPENDING "struct proc *p"
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.Ft int
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.Fn cursig "struct thread *td"
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.Ft void
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.Fn execsigs "struct proc *p"
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.Ft int
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.Fn issignal "struct thread *td"
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.Ft void
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.Fn killproc "struct proc *p" "char *why"
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.Ft void
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.Fn pgsigio "struct sigio **sigiop" "int sig" "int checkctty"
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.Ft void
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.Fn postsig "int sig"
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.Ft void
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.Fn sigexit "struct thread *td" "int signum"
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.Ft void
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.Fn siginit "struct proc *p"
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.Ft void
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.Fn signotify "struct thread *td"
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.Ft void
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.Fn trapsignal "struct thread *td" "int sig" "u_long code"
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.Sh DESCRIPTION
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The
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.Fn SIGADDSET
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macro adds
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.Fa signo
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to
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.Fa set .
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No effort is made to ensure that
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.Fa signo
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is a valid signal number.
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.Pp
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The
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.Fn SIGDELSET
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macro removes
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.Fa signo
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from
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.Fa set .
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No effort is made to ensure that
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.Fa signo
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is a valid signal number.
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.Pp
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The
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.Fn SIGEMPTYSET
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macro clears all signals in
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.Fa set .
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.Pp
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The
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.Fn SIGFILLSET
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macro sets all signals in
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.Fa set .
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.Pp
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The
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.Fn SIGISMEMBER
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macro determines if
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.Fa signo
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is set in
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.Fa set .
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.Pp
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The
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.Fn SIGISEMPTY
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macro determines if
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.Fa set
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does not have any signals set.
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.Pp
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The
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.Fn SIGNOTEMPTY
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macro determines if
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.Fa set
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has any signals set.
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.Pp
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The
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.Fn SIGSETEQ
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macro determines if two signal sets are equal; that is, the same signals
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are set in both.
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.Pp
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The
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.Fn SIGSETNEQ
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macro determines if two signal sets differ; that is, if any signal set in
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one is not set in the other.
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.Pp
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The
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.Fn SIGSETOR
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macro ORs the signals set in
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.Fa set2
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into
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.Fa set1 .
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.Pp
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The
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.Fn SIGSETAND
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macro ANDs the signals set in
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.Fa set2
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into
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.Fa set1 .
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.Pp
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The
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.Fn SIGSETNAND
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macro NANDs the signals set in
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.Fa set2
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into
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.Fa set1 .
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.Pp
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The
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.Fn SIG_CANTMASK
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macro clears the
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.Dv SIGKILL
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and
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.Dv SIGSTOP
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signals from
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.Fa set .
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These two signals cannot be blocked or caught and
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.Fn SIG_CANTMASK
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is used in code where signals are manipulated to ensure this policy
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is enforced.
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.Pp
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The
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.Fn SIG_STOPSIGMASK
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macro clears the
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.Dv SIGSTOP ,
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.Dv SIGTSTP ,
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.Dv SIGTTIN ,
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and
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.Dv SIGTTOU
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signals from
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.Fa set .
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.Fn SIG_STOPSIGMASK
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is used to clear stop signals when a process is waiting for a child to
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exit or exec, and when a process is continuing after having been
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suspended.
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.Pp
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The
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.Fn SIG_CONTSIGMASK
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macro clears the
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.Dv SIGCONT
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signal from
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.Fa set .
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.Fn SIG_CONTSIGMASK
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is called when a process is stopped.
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.Pp
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The
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.Fn SIGPENDING
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macro determines if the given process has any pending signals that are
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not masked.
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If the process has a pending signal and the process is currently being
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traced,
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.Fn SIGPENDING
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will return true even if the signal is masked.
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.Pp
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The
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.Fn cursig
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function returns the signal number that should be delivered to process
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.Fa td->td_proc .
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If there are no signals pending, zero is returned.
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.Pp
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The
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.Fn execsigs
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function resets the signal set and signal stack of a process in preparation
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for an
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.Xr execve 2 .
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The lock for
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.Fa p
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must be held before
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.Fn execsigs
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is called.
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.Pp
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The
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.Fn issignal
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function determines if there are any pending signals for process
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.Fa td->td_proc
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that should be caught, or cause this process to terminate or interrupt its
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current system call.
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If process
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.Fa td->td_proc
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is currently being traced, ignored signals will be handled and the process
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is always stopped.
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Stop signals are handled and cleared right away by
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.Fn issignal
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unless the process is a member of an orphaned process group and the stop
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signal originated from a TTY.
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The
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.Va sched_lock
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lock may be acquired and released, and if
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.Va Giant
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is held, it may be released and reacquired.
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The
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.Vt sigacts
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structure
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.Fa td->td_proc->p_sigacts
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must be locked before calling
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.Fn issignal
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and may be released and reacquired during the call.
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The process lock for
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.Fa td->td_proc
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must be acquired before calling
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.Fn issignal
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and may be released and reacquired during the call.
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The lock for the parent of
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.Fa td->td_proc
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may also be acquired and released.
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Default signal actions are not taken for system processes and init.
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.Pp
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The
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.Fn killproc
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function delivers
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.Dv SIGKILL
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to
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.Fa p .
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.Fa why
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is logged as the reason
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.Em why
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the process was killed.
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.Pp
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The
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.Fn pgsigio
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function sends the signal
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.Fa sig
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to the process or process group
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.Fa sigiop->sio_pgid .
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If
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.Fa checkctty
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is non-zero, the signal is only delivered to processes in the process group
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that have a controlling terminal.
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If
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.Fa sigiop->sio_pgid
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is for a process (> 0), the lock for
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.Fa sigiop->sio_proc
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is acquired and released.
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If
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.Fa sigiop->sio_pgid
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is for a process group (< 0), the process group lock for
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.Fa sigiop->sio_pgrp
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is acquired and released.
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The lock
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.Va sigio_lock
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is acquired and released.
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.Pp
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The
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.Fn postsig
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function handles the actual delivery of the signal
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.Fa sig .
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.Fn postsig
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is called from
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.Fn ast
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after the kernel has been notified that a signal should be delivered
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(via a call to
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.Fn signotify ,
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which causes the flag
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.Dv PS_NEEDSIGCHK
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to be set).
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The lock for process that owns
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.Va curthread
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must be held before
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.Fn postsig
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is called, and the current process cannot be 0.
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The lock for the
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.Va p_sigacts
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field of the current process must be held before
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.Fn postsig
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is called, and may be released and reacquired.
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.Pp
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The
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.Fn sigexit
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function causes the process that owns
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.Fa td
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to exit with a return value of signal number
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.Fa sig .
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If required, the process will dump core.
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The lock for the process that owns
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.Fa td
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must be held before
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.Fn sigexit
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is called.
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.Pp
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The
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.Fn siginit
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function is called during system initialization to cause every signal with
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a default property of
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.Dv SA_IGNORE
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(except
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.Dv SIGCONT )
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to be ignored by
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.Fa p .
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The process lock for
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.Fa p
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is acquired and released by
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.Fn siginit .
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The only process that
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.Fn siginit
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is ever called for
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is
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.Va proc0 .
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.Pp
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The
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.Fn signotify
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function flags that there are unmasked signals pending that
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.Fn ast
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should handle.
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The lock for process
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.Fa td->td_proc
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must be held before
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.Fn signotify
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is called, and
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.Va sched_lock
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is acquired and released.
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.Pp
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The
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.Fn trapsignal
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function sends a signal that is the result of a trap to process
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.Fa td->td_proc .
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If the process is not being traced and the signal can be delivered
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immediately,
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.Fn trapsignal
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will deliver it directly; otherwise,
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.Fn trapsignal
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will call
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.Xr psignal 9
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to cause the signal to be delivered.
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The
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.Va sched_lock
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lock is acquired and released, as is the lock for
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.Fa td->td_proc .
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The lock for the
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.Va p_sigacts
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field of
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.Fa td->td_proc
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is acquired and released.
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.Sh RETURN VALUES
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The
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.Fn SIGISMEMBER ,
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.Fn SIGISEMPTY ,
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.Fn SIGNOTEMPTY ,
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.Fn SIGSETEQ ,
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.Fn SIGSETNEQ ,
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and
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.Fn SIGPENDING
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macros all return non-zero (true) if the condition they are checking
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is found to be true; otherwise, zero (false) is returned.
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.Pp
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The
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.Fn cursig
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function returns either a valid signal number or zero.
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.Pp
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.Fn issignal
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returns either a valid signal number or zero.
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.Sh SEE ALSO
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.Xr gsignal 9 ,
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.Xr pgsignal 9 ,
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.Xr psignal 9
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.Sh AUTHORS
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This man page was written by
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.An Chad David Aq davidc@FreeBSD.org .
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