[Dovecot] freebsd 7, panics - kqueue?

[mike-maillist at nux.co.uk]

Hi,

We have a issue with a server pretty much just running dovecot, there's
about 250gb of maildirs which has about 200 simultaneous connections to
it running on freebsd 7. The machine has stayed up for about 8 days before
it panics but sometimes panics after about 24 hours.

We are running a PAE kernel (with ULE scheduler) as the machine has 2 (4
core processors) and 8gb of ram, dovecot is compiled with kqueue support
which i suspect is causing the panics.  We are currently trying with a
GENERIC kernel to see if this addresses the issue but looking back through
the dovecot lists there seems to be some issue with kqueue, freebsd and
dovecot, i am tempted to simply disable kqueue in dovecot but am not sure
on the performance penalties.

Please see the freebsd pr for the kgdb dumps - for both dumps the current
process was imap, and the second one seemed to hint towards a problem with
kqueue but im not a c or kernel hacker:

http://www.freebsd.org/cgi/query-pr.cgi?pr=129550

--- snip of what i think is relevent from the dump ---

(kgdb) list *0xc04c4c4d
0xc04c4c4d is in knlist_remove_kq (/usr/src/sys/kern/kern_event.c:1615).
1610 if (!kqislocked)
1611 KASSERT((kn->kn_status & (KN_INFLUX|KN_DETACHED)) == KN_INFLUX,
1612 ("knlist_remove called w/o knote being KN_INFLUX or already removed"));
1613 if (!knlislocked)
1614 knl->kl_lock(knl->kl_lockarg);
1615 SLIST_REMOVE(&knl->kl_list, kn, knote, kn_selnext);
1616 kn->kn_knlist = NULL;
1617 if (!knlislocked)
1618 knl->kl_unlock(knl->kl_lockarg);
1619 if (!kqislocked)
(kgdb)


mail# dovecot -n
# 1.1.7: /usr/local/etc/dovecot.conf
# OS: FreeBSD 7.0-RELEASE-p6 i386
ssl_cert_file: /etc/ssl/dovecot.pem
ssl_key_file: /etc/ssl/dovecot.pem
login_dir: /var/run/dovecot/login
login_executable: /usr/local/libexec/dovecot/imap-login
login_process_per_connection: no
login_processes_count: 20
login_max_processes_count: 256
login_max_connections: 512
max_mail_processes: 1024
verbose_proctitle: yes
first_valid_uid: 89
last_valid_uid: 89
first_valid_gid: 89
last_valid_gid: 89
mail_privileged_group: mail
imap_client_workarounds: delay-newmail outlook-idle netscape-eoh
tb-extra-mailbox-sep
auth default:
   passdb:
     driver: vpopmail
   userdb:
     driver: vpopmail