src/functions/functions.lock

   1 #!/bin/bash
   2 ###############################################################################
   3 #                                                                             #
   4 # IPFire.org - A linux based firewall                                         #
   5 # Copyright (C) 2012  Michael Tremer & Christian Schmidt                      #
   6 #                                                                             #
   7 # This program is free software: you can redistribute it and/or modify        #
   8 # it under the terms of the GNU General Public License as published by        #
   9 # the Free Software Foundation, either version 3 of the License, or           #
  10 # (at your option) any later version.                                         #
  11 #                                                                             #
  12 # This program is distributed in the hope that it will be useful,             #
  13 # but WITHOUT ANY WARRANTY; without even the implied warranty of              #
  14 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the               #
  15 # GNU General Public License for more details.                                #
  16 #                                                                             #
  17 # You should have received a copy of the GNU General Public License           #
  18 # along with this program.  If not, see <http://www.gnu.org/licenses/>.       #
  19 #                                                                             #
  20 ###############################################################################
  21
  22 __lock_path() {
  23         local name=${1}
  24
  25         if [ "${name:0:1}" = "/" ]; then
  26                 echo "${name}"
  27         else
  28                 echo "${LOCK_DIR}/network-${name}"
  29         fi
  30 }
  31
  32 lock_exists() {
  33         local name=${1}
  34         assert isset name
  35
  36         local lockfile=$(__lock_path ${name})
  37
  38         if [ -e "${lockfile}" ]; then
  39                 return ${EXIT_TRUE}
  40         else
  41                 return ${EXIT_FALSE}
  42         fi
  43 }
  44
  45 lock_acquire() {
  46         local name=${1}
  47         assert isset name
  48
  49         # timeout value in seconds
  50         local timeout=${2}
  51
  52         if ! isset timeout; then
  53                 timeout=0
  54         fi
  55
  56         local lockfile=$(__lock_path ${name})
  57
  58         timeout=$(( ${timeout} * 4 ))
  59
  60         log DEBUG "Acquiring lock '${name}'"
  61
  62         # Wait until lock is available
  63         while [ ${timeout} -gt 0 ] && [ -e "${lockfile}" ]; do
  64                 timeout=$(( ${timeout} - 1 ))
  65                 sleep 0.25
  66         done
  67
  68         # If another lock still exists, we return an error
  69         if [ -e "${lockfile}" ]; then
  70                 error "Could not acquire lock '${name}'"
  71                 return ${EXIT_ERROR}
  72         fi
  73
  74         # Write out pid to the lockfile and make sure that
  75         # nobody else can access it.
  76         echo "$$" > ${lockfile}
  77         chmod 600 ${lockfile}
  78 }
  79
  80 lock_release() {
  81         local name=${1}
  82         assert isset name
  83
  84         local lockfile=$(__lock_path ${name})
  85
  86         log DEBUG "Releasing lock '${name}'"
  87
  88         # Remove the lockfile (okay if it does not exist).
  89         rm -f ${lockfile}
  90 }