[LAU] jackd core dumps in duplex mode

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@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?