Race condition on restart
dwhile at while.org.uk
Wed Apr 26 16:38:52 UTC 2017
There is a bug in MailScanner which leads to a race condition.
The init script which starts/stops & restarts MailScanner removes the
PID file when MailScanner is stopped.
Unfortunately when MailScanner is issued with a SIGTERM (when issuing a
restart or stop) then it also removes the PID file (line 1419 in
What is happening is that the init script issues the kill and then
continues. This doesn't kill MailScanner but simply sends the signal.
MailScanner does some processing before dying. Consequently there is now
a race as to who will remove the PID file. The worst case is that it is
removed after MailScanner has been restarted. This leads to the hourly
ms-check constantly restarting MailScanner.
I fixed this in the init script by:
1. Removing the following lines from do_stop
# remove pid file
if [ -f $PIDFILE ] ; then
rm -f $PIDFILE
2. Moving the following lines from restart to do_stop where the above
lines were removed
while [ "$x" -lt 300 -a -f $PIDFILE ]; do
i=$(( (i+1) %4 ));
What this does is wait for MailScanner to die and remove the PID file
I don't think this is a permament fix as there ought to be a check that
it has not timed out before continuing.
More information about the MailScanner