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emellor@leeni.uk.xensource.com
c542b41feb
to create the lock directory. Signed-off-by: Ewan Mellor <ewan@xensource.com>
180 lines
3.4 KiB
Bash
180 lines
3.4 KiB
Bash
#
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# Copyright (c) 2005 XenSource Ltd.
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#
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# This library is free software; you can redistribute it and/or
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# modify it under the terms of version 2.1 of the GNU Lesser General Public
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# License as published by the Free Software Foundation.
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#
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# This library is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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# Lesser General Public License for more details.
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#
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# You should have received a copy of the GNU Lesser General Public
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# License along with this library; if not, write to the Free Software
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# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
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#
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dir=$(dirname "$0")
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. "$dir/xen-script-common.sh"
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exec 2>>/var/log/xen-hotplug.log
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export PATH="/sbin:/bin:/usr/bin:/usr/sbin:$PATH"
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export LANG="POSIX"
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unset $(set | grep ^LC_ | cut -d= -f1)
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log() {
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local level="$1"
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shift
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logger -p "daemon.$level" -- "$0:" "$@" || echo "$0 $@" >&2
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}
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fatal() {
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xenstore_write "$XENBUS_PATH"/hotplug-status error
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log err "$@"
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exit 1
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}
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success() {
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# Tell DevController that backend is "connected"
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xenstore_write "$XENBUS_PATH"/hotplug-status connected
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}
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do_or_die() {
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"$@" || fatal "$@ failed"
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}
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do_without_error() {
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"$@" 2>/dev/null || log debug "$@ failed"
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}
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sigerr() {
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fatal "$0 failed; error detected."
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}
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trap sigerr ERR
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##
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# xenstore_read <path>+
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#
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# Read each of the given paths, returning each result on a separate line, or
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# exit this script if any of the paths is missing.
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#
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xenstore_read() {
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local v=$(xenstore-read "$@" || true)
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[ "$v" != "" ] || fatal "xenstore-read $@ failed."
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echo "$v"
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}
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##
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# xenstore_read_default <path> <default>
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#
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# Read the given path, returning the value there or the given default if the
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# path is not present.
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#
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xenstore_read_default() {
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xenstore-read "$1" 2>/dev/null || echo "$2"
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}
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##
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# xenstore_write (<path> <value>)+
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#
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# Write each of the key/value pairs to the store, and exit this script if any
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# such writing fails.
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#
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xenstore_write() {
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log debug "Writing $@ to xenstore."
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xenstore-write "$@" || fatal "Writing $@ to xenstore failed."
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}
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#
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# Serialisation
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#
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LOCK_SLEEPTIME=1
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LOCK_SPINNING_RETRIES=5
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LOCK_RETRIES=10
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LOCK_BASEDIR=/var/run/xen-hotplug
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claim_lock()
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{
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local lockdir="$LOCK_BASEDIR/$1"
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mkdir -p "$LOCK_BASEDIR"
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_claim_lock "$lockdir"
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}
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release_lock()
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{
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_release_lock "$LOCK_BASEDIR/$1"
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}
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_claim_lock()
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{
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local lockdir="$1"
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local owner=$(_lock_owner "$lockdir")
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local retries=0
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while [ $retries -lt $LOCK_RETRIES ]
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do
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mkdir "$lockdir" 2>/dev/null && trap "release_lock $1; sigerr" ERR &&
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_update_lock_info "$lockdir" && return
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local new_owner=$(_lock_owner "$lockdir")
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if [ "$new_owner" != "$owner" ]
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then
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owner="$new_owner"
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retries=0
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fi
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if [ $retries -gt $LOCK_SPINNING_RETRIES ]
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then
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sleep $LOCK_SLEEPTIME
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else
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sleep 0
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fi
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retries=$(($retries + 1))
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done
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_steal_lock "$lockdir"
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}
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_release_lock()
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{
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trap sigerr ERR
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rm -rf "$1" 2>/dev/null || true
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}
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_steal_lock()
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{
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local lockdir="$1"
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local owner=$(cat "$lockdir/owner" 2>/dev/null || echo "unknown")
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log err "Forced to steal lock on $lockdir from $owner!"
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_release_lock "$lockdir"
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_claim_lock "$lockdir"
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}
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_lock_owner()
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{
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cat "$1/owner" 2>/dev/null || echo "unknown"
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}
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_update_lock_info()
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{
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echo "$$: $0" >"$1/owner"
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}
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log debug "$@" "XENBUS_PATH=$XENBUS_PATH"
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