Refactor network-hotplug-rename

[people/ms/network.git] / src / functions / functions.lock

#!/bin/bash
###############################################################################
#                                                                             #
# IPFire.org - A linux based firewall                                         #
# Copyright (C) 2012  Michael Tremer & Christian Schmidt                      #
#                                                                             #
# This program is free software: you can redistribute it and/or modify        #
# it under the terms of the GNU General Public License as published by        #
# the Free Software Foundation, either version 3 of the License, or           #
# (at your option) any later version.                                         #
#                                                                             #
# This program 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 General Public License for more details.                                #
#                                                                             #
# You should have received a copy of the GNU General Public License           #
# along with this program.  If not, see <http://www.gnu.org/licenses/>.       #
#                                                                             #
###############################################################################

__lock_path() {
	local name=${1}

	if [ "${name:0:1}" = "/" ]; then
		echo "${name}"
	else
		echo "${LOCK_DIR}/network-${name}"
	fi
}

lock() {
	local lock="${1}"
	shift

	local timeout="60"

	# Make partent directory
	make_parent_directory "${lock}"

	(
		log DEBUG "Trying to acquire lock ${lock}"

		# Try to acquire lock on fd 9
		if ! flock -w "${timeout}" 9; then
			log ERROR "Failed to acquire lock ${lock} after ${timeout} seconds"
			exit ${EXIT_ERROR}
		fi

		log DEBUG "Acquired lock ${lock}"

		# Remember return code
		ret=${EXIT_OK}

		# Run command
		"$@" || ret=$?

		log DEBUG "Released lock ${lock}"

		exit ${ret}
	) 9>${lock} || exit $?
}

lock_exists() {
	local name=${1}
	assert isset name

	local lockfile=$(__lock_path ${name})

	if [ -e "${lockfile}" ]; then
		return ${EXIT_TRUE}
	else
		return ${EXIT_FALSE}
	fi
}

lock_acquire() {
	local name=${1}
	assert isset name

	# timeout value in seconds
	local timeout=${2}

	if ! isset timeout; then
		timeout=0
	fi

	local lockfile=$(__lock_path ${name})

	timeout=$(( ${timeout} * 4 ))

	log DEBUG "Acquiring lock '${name}'"

	# Wait until lock is available
	while [ ${timeout} -gt 0 ] && [ -e "${lockfile}" ]; do
		timeout=$(( ${timeout} - 1 ))
		sleep 0.25
	done

	# If another lock still exists, we return an error
	if [ -e "${lockfile}" ]; then
		error "Could not acquire lock '${name}'"
		return ${EXIT_ERROR}
	fi

	# Write out pid to the lockfile and make sure that
	# nobody else can access it.
	echo "$$" > ${lockfile}
	chmod 600 ${lockfile}
}

lock_release() {
	local name=${1}
	assert isset name

	local lockfile=$(__lock_path ${name})

	log DEBUG "Releasing lock '${name}'"

	# Remove the lockfile (okay if it does not exist).
	rm -f ${lockfile}
}