111 lines
2.2 KiB
Bash
Executable File
111 lines
2.2 KiB
Bash
Executable File
#
|
|
# Copyright (c) 2005 XenSource Ltd.
|
|
#
|
|
# This library is free software; you can redistribute it and/or
|
|
# modify it under the terms of version 2.1 of the GNU Lesser General Public
|
|
# License as published by the Free Software Foundation.
|
|
#
|
|
# This library is distributed in the hope that it will be useful,
|
|
# but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
|
# Lesser General Public License for more details.
|
|
#
|
|
# You should have received a copy of the GNU Lesser General Public
|
|
# License along with this library; if not, write to the Free Software
|
|
# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
|
|
#
|
|
|
|
#
|
|
# Serialisation
|
|
#
|
|
|
|
LOCK_SLEEPTIME=1
|
|
LOCK_SPINNING_RETRIES=5
|
|
LOCK_RETRIES=100
|
|
LOCK_BASEDIR=/var/run/xen-hotplug
|
|
|
|
|
|
claim_lock()
|
|
{
|
|
local lockdir="$LOCK_BASEDIR/$1"
|
|
mkdir -p "$LOCK_BASEDIR"
|
|
_claim_lock "$lockdir"
|
|
}
|
|
|
|
|
|
release_lock()
|
|
{
|
|
_release_lock "$LOCK_BASEDIR/$1"
|
|
}
|
|
|
|
|
|
# This function will be redefined in xen-hotplug-common.sh.
|
|
sigerr() {
|
|
exit 1
|
|
}
|
|
|
|
|
|
_claim_lock()
|
|
{
|
|
local lockdir="$1"
|
|
local owner=$(_lock_owner "$lockdir")
|
|
local retries=0
|
|
|
|
while [ $retries -lt $LOCK_RETRIES ]
|
|
do
|
|
mkdir "$lockdir" 2>/dev/null && trap "_release_lock $lockdir; sigerr" ERR &&
|
|
_update_lock_info "$lockdir" && return
|
|
|
|
local new_owner=$(_lock_owner "$lockdir")
|
|
if [ "$new_owner" != "$owner" ]
|
|
then
|
|
owner="$new_owner"
|
|
retries=0
|
|
else
|
|
local pid=$(echo $owner | cut -d : -f 1)
|
|
if [ -n "$pid" -a "$pid" != "unknown" -a ! -f "/proc/$pid/status" ]
|
|
then
|
|
_release_lock $lockdir
|
|
fi
|
|
fi
|
|
|
|
if [ $retries -gt $LOCK_SPINNING_RETRIES ]
|
|
then
|
|
sleep $LOCK_SLEEPTIME
|
|
else
|
|
sleep 0
|
|
fi
|
|
retries=$(($retries + 1))
|
|
done
|
|
_steal_lock "$lockdir"
|
|
}
|
|
|
|
|
|
_release_lock()
|
|
{
|
|
trap sigerr ERR
|
|
rm -rf "$1" 2>/dev/null || true
|
|
}
|
|
|
|
|
|
_steal_lock()
|
|
{
|
|
local lockdir="$1"
|
|
local owner=$(cat "$lockdir/owner" 2>/dev/null || echo "unknown")
|
|
log err "Forced to steal lock on $lockdir from $owner!"
|
|
_release_lock "$lockdir"
|
|
_claim_lock "$lockdir"
|
|
}
|
|
|
|
|
|
_lock_owner()
|
|
{
|
|
cat "$1/owner" 2>/dev/null || echo "unknown"
|
|
}
|
|
|
|
|
|
_update_lock_info()
|
|
{
|
|
echo "$$: $0" >"$1/owner"
|
|
}
|