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kern_reboot(9): some updates

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- This function no longer disables interrupts
 - MLINK to reboot.9
 - The mentions of autoconfiguration is more about shutdown_nice(),
   coming in the next commit.
 - Describe the RB_* flags relevant to this function
 - Describe behaviour when shutdown hooks fail the reset
 - Describe expected execution contexts
 - Add FF copyright
 - xref panic(9)
 - xref this page in reboot(2)

Reviewed by:	markj
Discussed with:	rpokala, Pau Amma <pauamma@gundo.com>
MFC after:	1 week
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D39133
This commit is contained in:
Mitchell Horne 2023-03-20 16:56:54 -03:00 committed by Oscar Zhao
parent b1137dfbad
commit ee285c6980
3 changed files with 82 additions and 32 deletions
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3
lib/libc/sys/reboot.2
View File

@ -156,7 +156,8 @@ The caller is not the super-user.
.Xr halt 8 ,
.Xr init 8 ,
.Xr reboot 8 ,
.Xr savecore 8
.Xr savecore 8 ,
.Xr reboot 9
.Sh HISTORY
The
.Fn reboot

1
share/man/man9/Makefile
View File

@ -1335,6 +1335,7 @@ MLINKS+=intr_event.9 intr_event_add_handler.9 \
intr_event.9 intr_event_remove_handler.9 \
intr_event.9 intr_priority.9
MLINKS+=KASSERT.9 MPASS.9
MLINKS+=kern_reboot.9 reboot.9
MLINKS+=kern_yield.9 maybe_yield.9 \
kern_yield.9 should_yield.9
MLINKS+=kernacc.9 useracc.9

110
share/man/man9/kern_reboot.9
View File

@ -1,11 +1,18 @@
.\" $NetBSD: boot.9,v 1.2 1996/09/24 07:01:26 ghudson Exp $
.\"
.\" SPDX-License-Identifier: BSD-4-Clause
.\"
.\" Copyright (c) 1997
.\" Mike Pritchard. All rights reserved.
.\"
.\" Copyright (c) 1994 Christopher G. Demetriou
.\" All rights reserved.
.\"
.\" Copyright (c) 2021,2023 The FreeBSD Foundation
.\"
.\" Portions of this documentation were written by Mitchell Horne
.\" under sponsorship from the FreeBSD Foundation.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
@ -18,7 +25,7 @@
.\" must display the following acknowledgement:
.\" This product includes software developed by Christopher G. Demetriou
.\" for the NetBSD Project.
.\" 3. The name of the author may not be used to endorse or promote products
.\" 4. The name of the author may not be used to endorse or promote products
.\" derived from this software without specific prior written permission
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
@ -34,16 +41,17 @@
.\"
.\" $FreeBSD$
.\"
.Dd September 23, 2021
.Dt KERN_REBOOT 9
.Dd March 20, 2023
.Dt REBOOT 9
.Os
.Sh NAME
.Nm kern_reboot
.Nd halt or reboot the system
.Nd reboot, halt, or power off the system
.Sh SYNOPSIS
.In sys/types.h
.In sys/systm.h
.In sys/reboot.h
.Vt extern int rebooting;
.Ft void
.Fn kern_reboot "int howto"
.In sys/eventhandler.h
@ -53,53 +61,92 @@
.Sh DESCRIPTION
The
.Fn kern_reboot
function handles final system shutdown, and either halts or reboots
the system.
function handles final system shutdown, and either halts, reboots,
or powers down the system.
The exact action to be taken is determined by the flags passed in
.Fa howto
and by whether or not the system has finished autoconfiguration.
.Fa howto .
.Pp
The relevant flags are:
.Bl -tag -compact -offset indent -width "RB_POWERCYCLE"
.It Dv RB_HALT
Halt the system in-place rather than restarting.
.It Dv RB_POWEROFF
Power down the system rather than restarting.
.It Dv RB_POWERCYCLE
Request a power-cycle in addition to restarting.
.It Dv RB_NOSYNC
Do not sync filesystems during shutdown.
.It Dv RB_DUMP
Dump kernel memory during shutdown.
.El
.Pp
The
.Fa howto
field, and its full list of flags are described in additional detail by
.Xr reboot 2 .
.Pp
If the system has finished autoconfiguration,
.Fn kern_reboot
does the following:
performs the following actions:
.Bl -enum -offset indent
.It
If this is the first invocation of
.Fn kern_reboot
and the
Set the
.Va rebooting
variable to
.Dv 1 ,
indicating that the reboot process has begun and cannot be stopped.
.It
Set the
.Va kdb_active
variable to
.Dv 0 ,
indicating that execution has left the kernel debugger, if it was previously
active.
.It
Unless the
.Dv RB_NOSYNC
flag is not set in
flag is set in
.Fa howto ,
syncs and unmounts the system disks by calling
sync and unmount the system's disks by calling
.Xr vfs_unmountall 9 .
.It
Disables interrupts.
.It
If rebooting after a crash (i.e., if
If rebooting after a panic
.Po
.Dv RB_DUMP
is set in
.Fa howto ,
but
.Dv RB_HALT
is not), saves a system crash dump.
is not set
.Pc ,
initiate a system crash dump via
.Fn doadump .
.It
Runs any shutdown hooks previously registered.
Print a message indicating that the system is about to be halted
or rebooted, and a report of the total system uptime.
.It
Prints a message indicating that the system is about to be halted
or rebooted.
Execute all registered shutdown hooks.
.It
If
.Dv RB_HALT
is set in
.Fa howto ,
halts the system.
Otherwise, reboots the system.
As a last resort, if none of the shutdown hooks handled the reboot, call the
machine-dependent
.Fn cpu_reset
function.
In the unlikely case that this is not supported,
.Fn kern_reboot
will loop forever at the end of the function.
This requires a manual reset of the system.
.El
.Pp
If the system has not finished autoconfiguration,
.Fn kern_reboot
runs any shutdown hooks previously registered,
prints a message, and halts the system.
may be called from a typical kernel execution context, when the system is
running normally.
It may also be called as the final step of a kernel panic, or from the kernel
debugger.
Therefore, the code in this function is subject to restrictions described by
the
.Sx EXECUTION CONTEXT
section of the
.Xr panic 9
man page.
.Sh RETURN VALUES
The
.Fn kern_reboot
@ -107,4 +154,5 @@ function does not return.
.Sh SEE ALSO
.Xr reboot 2 ,
.Xr EVENTHANDLER 9 ,
.Xr panic 9 ,
.Xr vfs_unmountall 9