udev on Fedore 5

udev on Fedore 5

[Piet Delaney]

I wasn't able to login to your Fedora 5 (10.10.111.220).
I tried my AMD hammer at home (hammer.piet.net) and looked
at the Fedora 5 udev scripts. I can't see what the gento 
/sbin/start_udev might be doing to boost Performance so much
and didn't see the udev daemon stuff we saw on your system.
Perhaps it's probing the modules to pre-awaken them. I'm not
using modules, so I doubt it would have an effect.
--------------------------------------------------------------
			/sbin/start_udev
--------------------------------------------------------------

#!/bin/sh
#
# start_udev
#
# script to initialize /dev by using udev.
#
# Copyright (C) 2004 Greg Kroah-Hartman <greg@kroah.com>
#
# Released under the GPL v2 only.
#
# This needs to be run at the earliest possible point in the boot
# process.
#
# Based on the udev init.d script
#
# Thanks go out to the Gentoo developers for proving
# that this is possible to do.
#
# Yes, it's very verbose, feel free to turn off all of the echo calls,
# they were there to make me feel better that everything was working
# properly during development...
#
# don't use udev if sysfs is not mounted.

sysfs_dir=/sys

[ -d $sysfs_dir/class ] || exit 1
[ -r /proc/mounts ] || exit 1
[ -x /sbin/udev ] || exit 1
[ -f /etc/udev/udev.conf ] && . /etc/udev/udev.conf


. /etc/init.d/functions

prog=udev
bin=/sbin/udev
udevd=/sbin/udevd
MAKEDEV="/sbin/MAKEDEV"
xargs_simple () {
        if [ "$1" = "-n" ]; then
                shift
                MAXNR="$1"
                shift
        else
                MAXNR\x100
        fi
        NR=$MAXNR
        ARGS=""
        [ -z "$1" ] && set echo

        while read line; do
                if [ $NR -gt 0 ]; then
                        ARGS="$ARGS $line"
                        NR=$[$NR - 1]
                else
                        "$@" $ARGS
                        NR=$MAXNR
                        ARGS="$line"
                fi
        done
        if [ -n "$ARGS" ]; then
                "$@" $ARGS
        fi
}
make_extra_nodes () {
        ln -snf /proc/self/fd $udev_root/fd
        ln -snf /proc/self/fd/0 $udev_root/stdin
        ln -snf /proc/self/fd/1 $udev_root/stdout
        ln -snf /proc/self/fd/2 $udev_root/stderr
        ln -snf /proc/kcore $udev_root/core

        [ -d $udev_root/pts ] || mkdir -m 0755 $udev_root/pts
        [ -d $udev_root/shm ] || mkdir -m 0755 $udev_root/shm
        [ -a /dev/MAKEDEV ] || ln -s $MAKEDEV /dev/MAKEDEV;

        if [ -x $MAKEDEV ]; then
                for i in /etc/udev/makedev.d/*.nodes; do
                        if [ -f "$i" ]; then
                                cat "$i" | sed -e 's,#.*,,g' | \
                                        xargs_simple -n 100 $MAKEDEV -x
                        fi
                done
        fi
        pushd /etc/udev/devices &> "$udev_root/null"
        set *
        if [ "$1" != "*" ]; then
                cp -ar "$@" $udev_root/
                pushd "$udev_root" &> "$udev_root/null"
                [ -x /sbin/restorecon ] && /sbin/restorecon "$@"
                popd &> "$udev_root/null"
        fi
        popd &> "$udev_root/null"
}

# we cannot use /usr/bin/find here
find_d () {
        where=$1
        what=$2
        found=""
        for f in $where/*; do
                if [ -d "$f" -a ! -L "$f" ]; then
                        if [ "$f" != "${f%%$what}" ];then
                                # make sure we are at the path end
                                # we have no dirname and basename
                                rest="${f#*$what}"
                                [ "${rest##*/}" = "$rest" ] &&
found="$found $f"
                        fi
                        found="$found $(find_d $f $what)"
                fi
        done
        echo "$found"
}

# we cannot use /usr/bin/find here
find_f () {
        where=$1
        what=$2
        found=""
        for f in $where/*; do
                if [ -d "$f" -a ! -L "$f" ]; then
                        found="$found $(find_f $f $what)"
                elif [ -e "$f" ]; then
                        [ "$where/" = "${f%$what}" ] && found="$found
$f"
                fi
        done
        [ -n "$found" ] && echo "$found"
}

kill_udevd() {
        if [ -x /sbin/pidof ]; then
                pid=`/sbin/pidof -x udevd`
                [ -n "$pid" ] && kill $pid
        fi
}


# call hotplug with the scsi devices
scsi_replay () {
        HOTPLUG=$(cat /proc/sys/kernel/hotplug)
        [ -z "$HOTPLUG" ] && return 1

        scsi_hosts=$(find_d /sys/devices host\*)
        SEQNUM=1

        for host in $scsi_hosts;do
                [ -d $host ] || continue
                devs=$(find_f $host type)
                for dev in $devs;do
                        [ -f $dev ] || continue
                        export SEQNUM
                        DEVPATH=${dev%/type}
                        DEVPATH=${DEVPATH#/sys}
                        export DEVPATH
                        export ACTION­d
                        $HOTPLUG scsi_device
                        SEQNUM=$[$SEQNUM + 1]
                        $HOTPLUG scsi
                        SEQNUM=$[$SEQNUM + 1]
                done
        done
        return 0
}

164,1         60%

ide_scan() {
    if [ ! -d /proc/ide ]; then
        return 1
    fi
    for i in /proc/ide/*/media; do
        read media < "$i"
        case "$media" in
            disk)
                module=ide-disk
                ;;
            cdrom)
                module=ide-cd
                ;;
            tape)
                module=ide-tape
                ;;
            floppy)
                module=ide-floppy
                ;;
            *)
                module=ide-generic
                ;;
        esac
        /sbin/modprobe $module
    done
    return 0
}


export ACTION­d
prog=udev
ret=0
STRING=$"Starting $prog: "
# propagate $udev_root from /sys
echo -n "$STRING "

# mount the tmpfs on ${udev_root%/}, if not already done
LANG=C awk "\$2 = \"${udev_root%/}\" && \$3 = \"tmpfs\" { exit
1 }" /proc/mounts && {
        if LANG=C fgrep -q "none ${udev_root%/}/pts " /proc/mounts; then
                PTSDIR=$(mktemp -d)
                mount --move $udev_root/pts "$PTSDIR"
        fi
        if LANG=C fgrep -q "none ${udev_root%/}/shm " /proc/mounts; then
                SHMDIR=$(mktemp -d)
                mount --move $udev_root/shm "$SHMDIR"
        fi
        mount -n -o mode\a55 -t tmpfs none "$udev_root"
        mkdir -m 0755 $udev_root/pts
        mkdir -m 0755 $udev_root/shm
        if [ -n "$PTSDIR" ]; then
                mount --move "$PTSDIR" $udev_root/pts
                rmdir "$PTSDIR"
        fi
        if [ -n "$SHMDIR" ]; then
                mount --move "$SHMDIR" $udev_root/shm
                rmdir "$SHMDIR"
        fi

        ret=$[$ret + $?]
}

rm -fr "$udev_db"
make_extra_nodes
kill_udevd > "$udev_root/null" 2>&1
scsi_replay > "$udev_root/null" 2>&1
ret=$[$ret + $?]
ide_scan > "$udev_root/null" 2>&1
/sbin/udevstart
ret=$[$ret + $?]
[ $ret -eq 0 ] && success $"$STRING" || failure $"$STRING"
echo
exit 0




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Re: udev on Fedore 5

[Greg KH]

On Wed, Aug 02, 2006 at 10:14:46PM -0700, Piet Delaney wrote:
> I wasn't able to login to your Fedora 5 (10.10.111.220).
> I tried my AMD hammer at home (hammer.piet.net) and looked
> at the Fedora 5 udev scripts. I can't see what the gento 
> /sbin/start_udev might be doing to boost Performance so much
> and didn't see the udev daemon stuff we saw on your system.
> Perhaps it's probing the modules to pre-awaken them. I'm not
> using modules, so I doubt it would have an effect.

The gentoo script for startup is attached below.  It picks it's startup
logic depending on the kernel version running.

Hope this helps,

greg k-h

------------------
# Copyright 1999-2005 Gentoo Foundation
# Distributed under the terms of the GNU General Public License v2

udev_version() {
	local version=0

	if [[ -x /sbin/udev ]] ; then
		version=$(/sbin/udev -V)
		# We need it without a leading '0', else bash do the wrong thing
		version=${version##0}
		# Older udev's will print nothing
		[[ -z ${version} ]] && version=0
	fi

	echo "${version}"
}

# This works for 2.6.15 kernels or greater
trigger_events() {
	list=""
	# if you want real coldplug (with all modules being loaded for all
	# devices in the system), uncomment out the next line.
	#list="$list $(echo /sys/bus/*/devices/*/uevent)"
	list="$list $(echo /sys/class/*/*/uevent)"
	list="$list $(echo /sys/block/*/uevent /sys/block/*/*/uevent)"
	for i in $list; do
		case "$i" in
			*/device/uevent)
				# skip followed device symlinks
				continue
				;;
			*/class/mem/*|*/class/tty/*)
				first="$first $i"
				;;
			*/block/md*)
				last="$last $i"
				;;
			*/*)
				default="$default $i"
				;;
		esac
	done

	# trigger the sorted events
	for i in $first $default $last; do
		echo "add" > "$i"
	done
}

populate_udev() {
	# populate /dev with devices already found by the kernel
	if [ "$(get_KV)" -gt "$(KV_to_int '2.6.14')" ] ; then
		ebegin "Populating /dev with existing devices through uevents"
		udevtrigger
		eend 0
	else
		ebegin "Populating /dev with existing devices with udevstart"
		/sbin/udevstart
		eend 0
	fi

	# loop until everything is finished
	# there's gotta be a better way...
	ebegin "Letting udev process events"
	loop=0
	while test -d /dev/.udev/queue; do
		sleep 0.1;
		test "$loop" -gt 300 && break
		loop=$(($loop + 1))
	done
	#einfo "loop = $loop"
	eend 0

	return 0
}

seed_dev() {
	# Seed /dev with some things that we know we need
	ebegin "Seeding /dev with needed nodes"

	# copy over any persistant things
	if [[ -d /lib/udev/devices ]] ; then
		cp --preserve=all --recursive --update /lib/udev/devices/* /dev
	fi

	# Not provided by sysfs but needed
	ln -snf /proc/self/fd /dev/fd
	ln -snf fd/0 /dev/stdin
	ln -snf fd/1 /dev/stdout
	ln -snf fd/2 /dev/stderr
	[[ -e /proc/kcore ]] && ln -snf /proc/kcore /dev/core

	# Create problematic directories
	mkdir -p /dev/{pts,shm}
	eend 0
}


main() {
	# Setup temporary storage for /dev
	ebegin "Mounting /dev for udev"
	if [[ ${RC_USE_FSTAB} = "yes" ]] ; then
		mntcmd=$(get_mount_fstab /dev)
	else
		unset mntcmd
	fi
	if [[ -n ${mntcmd} ]] ; then
		try mount -n ${mntcmd}
	else
		if egrep -qs tmpfs /proc/filesystems ; then
			mntcmd="tmpfs"
		else
			mntcmd="ramfs"
		fi
		# many video drivers require exec access in /dev #92921
		try mount -n -t ${mntcmd} udev /dev -o exec,nosuid,mode\a55
	fi
	eend $?

	# Create a file so that our rc system knows it's still in sysinit.
	# Existance means init scripts will not directly run.
	# rc will remove the file when done with sysinit.
	touch /dev/.rcsysinit

	# Selinux lovin; /selinux should be mounted by selinux-patched init
	if [[ -x /sbin/restorecon && -c /selinux/null ]] ; then
		restorecon /dev &> /selinux/null
	fi

	# Actually get udev rolling
	if [[ ${RC_DEVICE_TARBALL} = "yes" && \
	      -s /lib/udev-state/devices.tar.bz2 ]] ; then
		ebegin "Populating /dev with saved device nodes"
		try tar -jxpf /lib/udev-state/devices.tar.bz2 -C /dev
		eend $?
	fi

	seed_dev

	# Setup hotplugging (if possible)
	ebegin "Setting up proper hotplug agent"
	if [[ -e /proc/sys/kernel/hotplug ]] ; then
		if [ "$(get_KV)" -gt "$(KV_to_int '2.6.14')" ] ; then
			einfo "  Using netlink for hotplug events..."
			echo "" > /proc/sys/kernel/hotplug
		elif [[ $(udev_version) -ge "48" ]] ; then
			einfo "  Setting /sbin/udevsend as hotplug agent ..."
			echo "/sbin/udevsend" > /proc/sys/kernel/hotplug
		elif [[ -x /sbin/hotplug ]] ; then
			einfo "  Using /sbin/hotplug as hotplug agent ..."
		else
			einfo "  Setting /sbin/udev as hotplug agent ..."
			echo "/sbin/udev" > /proc/sys/kernel/hotplug
		fi
	fi
	eend 0

	ebegin "Starting udevd"
	/sbin/udevd --daemon
	eend $?

	populate_udev

	# Create nodes that udev can't
	ebegin "Finalizing udev configuration"
	[[ -x /sbin/dmsetup ]] && /sbin/dmsetup mknodes &>/dev/null
	[[ -x /sbin/lvm ]] && \
		/sbin/lvm vgscan -P --mknodes --ignorelockingfailure &>/dev/null
	# Running evms_activate on a LiveCD causes lots of headaches
	[[ -z ${CDBOOT} ]] && [[ -x /sbin/evms_activate ]] && \
		/sbin/evms_activate -q &>/dev/null
	eend 0
}

main


# vim:ts=4

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