The buggy sessionclean cron task described in T73645: php5 session cleanup script can go nuts is now having problems on tools-bastion-02.tools.eqiad.wmflabs and tools-bastion-05.tools.eqiad.wmflabs. This script runs every half hour and uses lsof to check to see if a session file is active before cleaning it up.
Yesterday I caught 60+ copies of the script running on each trusty bastion. I manually killed them and now less than 24 hours later there are 40+ stuck again. The magic command to kill them off is ps ax|grep lsof|grep -v grep|awk '{print $1}'|xargs sudo kill.
The fix applied for MediaWiki-Vagrant in T73645 was to backport a replacement script from the upstream Debian 5.5 package via Puppet. The most current PHP 5.5 cleaning script from upstream is https://anonscm.debian.org/cgit/pkg-php/php.git/tree/debian/sessionclean?h=master-5.5&id=64d94baca49c60041d02902c4ba7d564a17a3dbf