sympl-firewall: "Another app is currently holding the xtables lock"
One user was reporting emails like this, coming from
/usr/sbin/sympl-firewall-blacklist on two hosts.
From: Cron Daemon <email@example.com> Date: Mon, 14 Sep 2020 at 19:00 Subject: Cron <root@hostname> [ -x /usr/sbin/sympl-firewall ] && /usr/sbin/sympl-firewall To: <firstname.lastname@example.org> Another app is currently holding the xtables lock. Perhaps you want to use the -w option? sympl-firewall: Firewall script failed. sympl-firewall: Flushing /sbin/iptables rules and chains. sympl-firewall: Flushing /sbin/ip6tables rules and chains. sympl-firewall: Restoring old iptables rules and chains. sympl-firewall: Restoring old ip6tables rules and chains. sympl-firewall: Left firewall script in /tmp/user/0/sympl-firewall-20200914-1505-1srb1j3-saved for inspection.
The direct cause is unclear at the moment, and they don't happen all the time (once a day or so, apparently), so it may simply be a race condition.