docs/132884: [request] No manpage for SYSINIT and SYSUNINIT

[John Baldwin]

The following reply was made to PR docs/132884; it has been noted by GNATS.

From: John Baldwin <jhb at freebsd.org>
To: Sergey Kandaurov <pluknet at gmail.com>
Cc: bug-followup at freebsd.org
Subject: Re: docs/132884: [request] No manpage for SYSINIT and SYSUNINIT
Date: Wed, 1 Dec 2010 17:24:50 -0500

 On Wednesday, December 01, 2010 12:56:37 pm Sergey Kandaurov wrote:
 > What about this one?
 > It's extended from what was found at ~hmp,
 > parts taken from the arch book.
 
 I think this looks fairly good, but I hacked on it some to adjust some wording 
 I thought was awkward.  I also used .Fa instead of .Pa for macro arguments and 
 expanded the text to note things like the sorting order and to add more detail 
 on when these functions are executed (and when they aren't).  I also picked an
 MI example (and one that doesn't use the bad form of SI_SUB_FOO - 1).
 
 .\" Copyright (c) 2003 Hiten M. Pandya
 .\" 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 AUTHOR 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 AUTHOR 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.
 .\"
 .\" $FreeBSD$
 .\"
 .Dd December 1, 2010
 .Dt SYSINIT 9
 .Os
 .Sh NAME
 .Nm SYSINIT ,
 .Nm SYSUNINIT 
 .Nd a framework for dynamic kernel initialization
 .Sh SYNOPSIS
 .In sys/param.h
 .In sys/kernel.h
 .Fn SYSINIT "uniquifier" "enum sysinit_sub_id subsystem" "enum 
 sysinit_elem_order order" "sysinit_cfunc_t func" "const void *ident"
 .Fn SYSUNINIT "uniquifier" "enum sysinit_sub_id subsystem" "enum 
 sysinit_elem_order order" "sysinit_cfunc_t func" "const void *ident"
 .Sh DESCRIPTION
 .Nm
 is a mechanism for scheduling the execution of initialization and teardown
 routines.
 This is similar to init and fini routines with the addition of explicit
 ordering metadata.
 It allows runtime ordering of subsystem initialization in the kernel as well
 as kernel modules (KLDs).
 .Pp
 The
 .Fn SYSINIT
 macro creates a
 .Vt struct sysinit
 and stores it in a startup linker set.
 The
 .Vt struct sysinit
 type as well as the subsystem identifier constants
 .Pq Dv SI_SUB_*
 and initialization ordering constants
 .Pq Dv SI_ORDER_*
 are defined in
 .In sys/kernel.h :
 .Bd -literal
 struct sysinit {
 	enum sysinit_sub_id subsystem;	/* subsystem identifier*/
 	enum sysinit_elem_order	order;	/* init order within subsystem*/
 	sysinit_cfunc_t func;		/* function             */
 	const void	*udata;		/* multiplexer/argument */
 };
 .Ed
 .Pp
 The
 .Fn SYSINIT
 macro takes a
 .Fa uniquifier
 argument to identify the particular function dispatch data,
 the
 .Fa subsystem
 type of startup interface, the subsystem element
 .Fa order
 of initialization within the subsystem, the
 .Fa func
 function to call,
 and the data specified in
 .Fa ident
 argument to pass the function.
 .Pp
 The
 .Fn SYSUNINIT
 macro behaves similarly to the
 .Fn SYSINIT
 macro except that it adds the data to a shutdown linker set.
 .Pp
 The startup linker set for the kernel is scanned during boot to build a
 sorted list of initialization routines.
 The initialization routines are then executed in the sorted order.
 The
 .Fa subsystem
 is used as the primary key and is sorted in ascending order.
 The
 .Fa order
 is used as the secondary key and is sorted in ascending order.
 The relative order of two routines that have the same
 .Fa subsystem
 and
 .Fa order
 is undefined.
 .Pp
 The startup linker sets for modules that are loaded together with the kernel
 by the boot loader are scanned during the
 .Dv SI_SUB_KLD
 subsystem initialization.
 These modules' initialization routines are sorted and merged into the kernel's
 list of startup routines and are executed during boot along with the kernel's
 initialization routines.
 Note that this has the effect that any initialization routines in a kernel
 module that are scheduled earlier than
 .Dv SI_SUB_KLD
 are not executed until after
 .Dv SI_SUB_KLD
 during boot.
 .Pp
 The startup linker set for a kernel module loaded at runtime via
 .Xr kldload 2
 is scanned, sorted, and executed when the module is loaded.
 .Pp
 The shutdown linker set for a kernel module is scanned, sorted, and executed
 when a kernel module is unloaded.
 The teardown routines are sorted in the reverse order of the initialization
 routines.
 The teardown routines of the kernel and any loaded modules are
 .Sy not
 executed during shutdown.
 .Sh EXAMPLES
 This example shows the SYSINIT which displays the copyright notice during 
 boot:
 .Bd -literal -offset indent
 static void
 print_caddr_t(void *data)
 {
 	printf("%s", (char *)data);
 }
 SYSINIT(announce, SI_SUB_COPYRIGHT, SI_ORDER_FIRST, print_caddr_t,
     copyright);
 .Ed
 .Sh SEE ALSO
 .Xr kld 4 ,
 .Xr DECLARE_MODULE 9 ,
 .Xr DEV_MODULE 9 ,
 .Xr DRIVER_MODULE 9 ,
 .Xr MTX_SYSINIT 9 ,
 .Xr SYSCALL_MODULE 9
 .Sh HISTORY
 The
 .Nm
 framework first appeared in
 .Fx 2.2 .
 .Sh AUTHORS
 .An -nosplit
 The
 .Nm
 framework was written by
 .An Terrence Lambert Aq terry at FreeBSD.org .
 .Pp
 This manual page was written by
 .An Hiten Pandya Aq hmp at FreeBSD.org .
 
 
 -- 
 John Baldwin