[Dovecot] Unkillable imap process?

[Johan Persson]

Hi,

Not sure if this is relevant but having been running dovecot 1.1.4 for a long 
time (without any problem) I recently upgraded to 1.1.7 when I switched to 
SuSE 11.1 This is just running on my home server and it's a fairly standard 
fetchmail-procmail-dovecot setup.

However I recently had an incident which I cannot quite explain. I suspect it 
could be a possible disk problem but I did run a SMART check and the disks and 
HW seems ok. The mail store is mounted on a separate partition using ext3 fs

What happened was that I noticed that the load on my server went through the 
roof and that the imap process was hogging 100% of the CPU and it had been 
running so for over an hour.

Before this happened I had just setup a new laptop with Thunderbird as the 
mail client and had just done a off-line sync of my whole mail store (~1.5GB).
So for a short time the dovecot server would have been under maximum load.

I tried to recover by gracefully shutting down dovecot and when that didn't 
stop the imap process I first tried to be nice by sending it the TERM signal 
and when that didn't do it, the KILL signal.

However, I was not able to stop the imap process. I then decided to recycle 
the server and initiated a shutdown. However, not even that was able to 
complete (since the shutdown process seemed to be hanging on not being able to 
stop the imap process).  In the end I was (for the first time in over 6 years) 
forced to use the hard reset button on the server.

I do realize that this is almost impossible to diagnose, but does anyone now 
in general what could possible cause the imap process to so completely be 
locked up that it is impossible to even shut it down? 

The dovecot -n output is

 1.1.7: /etc/dovecot/dovecot.conf
# OS: Linux 2.6.27.7-9-pae i686 openSUSE 11.1 (i586) ext3
log_path: /var/log/dovecot.err
info_log_path: /var/log/dovecot.info
login_dir: /var/run/dovecot/login
login_executable: /usr/lib/dovecot/imap-login
login_processes_count: 2
login_max_processes_count: 2
login_max_connections: 5
max_mail_processes: 32
mail_max_userip_connections: 8
mail_location: maildir:/srv/mail/%u
mailbox_idle_check_interval: 15
fsync_disable: yes
auth default:
  passdb:
    driver: pam
  userdb:
    driver: passwd

Cheers
Johan