[LAU] jackd core dumps in duplex mode

[Gerhard Zintel]

Hi list,

I have been running jackd successfully for years now but since some 
time, I can either playback using 
$ /usr/bin/jackd -dalsa -dhw:0 -r44100 -p512 -n2 -P

or capture using
$ /usr/bin/jackd -dalsa -dhw:0 -r44100 -p512 -n2 -C

but trying to use duplex mode
$ /usr/bin/jackd -dalsa -dhw:0 -r44100 -p512 -n2

jackd gives me:
======== snip ==========
jackd 0.122.0
Copyright 2001-2009 Paul Davis, Stephane Letz, Jack O'Quinn, Torben 
Hohn and oth
jackd comes with ABSOLUTELY NO WARRANTY
This is free software, and you are welcome to redistribute it
under certain conditions; see the file COPYING for details

JACK compiled with System V SHM support.
loading driver ..
apparent rate = 44100
creating alsa driver ... hw:0|hw:0|512|2|44100|0|0|nomon|swmeter|-|
32bit
control device hw:0
configuring for 44100Hz, period = 512 frames (11.6 ms), buffer = 2 
periods
ALSA: final selected sample format for capture: 32bit integer 
little-endian
ALSA: use 2 periods for capture
ALSA: final selected sample format for playback: 32bit integer 
little-endian
ALSA: use 2 periods for playback
jackd watchdog: timeout - killing jackd
Aborted (core dumped)
======== snip ==========

in verbose mode I get additionally:
======== snip ==========
new buffer size 512
resizing port buffer segment for type 0, one buffer = 2048 bytes
resizing port buffer segment for type 1, one buffer = 2048 bytes
registered port system:capture_1, offset = 2048
registered port system:capture_2, offset = 4096
registered port system:playback_1, offset = 0
registered port system:playback_2, offset = 0
registered port system:playback_3, offset = 0
registered port system:playback_4, offset = 0
registered port system:playback_5, offset = 0
registered port system:playback_6, offset = 0
++ jack_sort_graph
++ jack_rechain_graph():
-- jack_rechain_graph()
-- jack_sort_graph
346 waiting for signals
======== snip ==========


I have no idea how to proceed from here to find the reason. Any hint 
will be most appreciated.

Gerhard

Further infos:
Audio device: Intel Corporation 7 Series/C210 Series Chipset Family 
High Definition Audio Controller (rev 04)

cat /proc/asound/version
Advanced Linux Sound Architecture Driver Version k3.8.0-35-generic.

cat /proc/asound/cards
gerbil:$ cat /proc/asound/cards
 0 [PCH            ]: HDA-Intel - HDA Intel PCH
                      HDA Intel PCH at 0xf7f10000 irq 44
 1 [Loopback       ]: Loopback - Loopback
                      Loopback 1

cat /proc/version
Linux version 3.8.0-35-generic (buildd at allspice) (gcc version 4.7.3 
(Ubuntu/Linaro 4.7.3-1ubuntu1) ) #50-Ubuntu SMP Tue Dec 3 01:25:33 
UTC 2013

What more on information should I provide?