rfcomm does not release its devices sometimes

[Sergei (Nolar) Vasilyev]

I use rfcomm to connect to bluetooth GPS receiver. /etc/bluetooth/rfcomm.conf is configured to bind four devices (rfcomm0..3) to the same bt-addr and channel. There are these four devices in /dev/. Sometimes it works perfectly: cat /dev/rfcomm0 connects to gps-device and prints data. Also 'gpsbabel' is used to download mtk-log via this serial port.

But sometimes something inside the system locks this device. And since then it is impossible to connect to rfcomm0. It says:
  cat: /dev/rfcomm0: Connection timed out
OR, less often, silently exits with no error message (and no data being transfered). Using rfcomm1, rfcomm2, rfcomm3 solves the problem for a while, until they will be locked too. These devices never unlock on their own. Only rebooting helps.

During device being locked, `lsof` says nothing on them. After releasing all rfcomms (`sudo rfcomm release all`) and ensuring all of them really were released (`rfcomm -a`), `lsmod` says module rfcomm is still used 2-4 times with no dependencies. Number of dependencies seems to always be even (2,4,6), never odd. Removing module rfcomm or bluetooth or any other from bluez stack is impossible (they are being "used").

I suggest, this is some kind of kernel-side locking; maybe because the device is not released properly or something like that.
There is no any strict way to reproduce this behavior. Only intensive using (opening-closing) sometimes makes rfcomm devices
"used to death".

Ubuntu Intrepid 8.10 (updated from 8.04) with all up-to-date updates.

$ lsb_release -rd
Description: Ubuntu 8.10
Release: 8.10

$ uname -a
Linux Nolar-XPS 2.6.27-9-generic #1 SMP Thu Nov 20 21:57:00 UTC 2008 i686 GNU/Linux

$ dpkg-query -l | grep bluez
ii bluez 4.12-0ubuntu5 Bluetooth tools and daemons
ii bluez-alsa 4.12-0ubuntu5 Bluetooth audio support
rc bluez-audio 3.36-1ubuntu2 Bluetooth audio support
ii bluez-btsco 1:0.50-0ubuntu3 Bluez Bluetooth SCO tool
ii bluez-cups 4.12-0ubuntu5 Bluetooth printer driver for CUPS
ii bluez-gnome 1.8-0ubuntu1 Bluetooth utilities for GNOME
ii bluez-gstreamer 4.12-0ubuntu5 Bluetooth gstreamer support
ii bluez-hcidump 1.42-1build1 Analyses Bluetooth HCI packets
rc bluez-network 3.36-1ubuntu2 Bluetooth network support
ii bluez-utils 4.12-0ubuntu5 Transitional package
ii python-bluez 0.15-1build1 Python wrappers around BlueZ for rapid bluet

Write what to check if you need more info.

[Baptiste Mille-Mathias (bmillemathias)]

Hi Sergei,

Does the bug still happen in new release of ubuntu?

Regards

[Baptiste Mille-Mathias (bmillemathias)]

Sergei,

If it still happens I suggest you to ask directly on the linux-bluetooth mailing list where the developers will be able to provide you help. If you can forward here the information relative to his bug that'd be great.

Thanks.

[Konrad Zapałowicz (kzapalowicz)]

This is reported against an old version of Ubuntu and many things has changed since then. Because of that we won't fix this issue however if this behavior repeats on a modern version please fill a bug report against it and we will take it from there.