Debian Bug report logs - #426412
python-dbus: system_bus.remove_signal_receiver() freezes

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Message #5 received at submit@bugs.debian.org (full text, mbox, reply):

From: Tony Houghton <h@realh.co.uk>

To: Debian Bug Tracking System <submit@bugs.debian.org>

Subject: python-dbus: system_bus.remove_signal_receiver() freezes

Date: Mon, 28 May 2007 16:44:47 +0100

Package: python-dbus
Version: 0.81.0-1
Severity: normal


hal-device-manager and an experimental device manager applet for the ROX
desktop called DevTray keep freezing on me when a device is removed or
when I quit DevTray. I tracked it down to this call in DevTray:

system_bus.remove_signal_receiver(item._property_modified,
                                  'PropertyModified',
                                  'org.freedesktop.Hal.Device',
                                  'org.freedesktop.Hal',
                                   udi)

I haven't checked exactly where hal-device-manager is freezing, but I
notice that its code does contain a very similar call.

-- System Information:
Debian Release: lenny/sid
  APT prefers unstable
  APT policy: (500, 'unstable'), (1, 'experimental')
Architecture: amd64 (x86_64)

Kernel: Linux 2.6.21.1
Locale: LANG=en_GB.UTF-8, LC_CTYPE=en_GB.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/bash

Versions of packages python-dbus depends on:
ii  libc6                         2.5-9      GNU C Library: Shared libraries
ii  libdbus-1-3                   1.0.2-5    simple interprocess messaging syst
ii  libdbus-glib-1-2              0.73-2     simple interprocess messaging syst
ii  libglib2.0-0                  2.12.12-1  The GLib library of C routines
ii  python                        2.4.4-6    An interactive high-level object-o
ii  python-support                0.6.4      automated rebuilding support for p

Versions of packages python-dbus recommends:
ii  python-gobject                2.12.3-2   Python bindings for the GObject li

-- no debconf information

Message #10 received at 426412@bugs.debian.org (full text, mbox, reply):

From: Simon McVittie <smcv@ianadd.pseudorandom.co.uk>

To: Tony Houghton <h@realh.co.uk>, 426412@bugs.debian.org

Subject: Re: [Pkg-utopia-maintainers] Bug#426412: python-dbus: system_bus.remove_signal_receiver() freezes

Date: Mon, 28 May 2007 18:43:46 +0100

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On Mon, 28 May 2007 at 16:44:47 +0100, Tony Houghton wrote:
> I tracked it down to this call in DevTray:
> 
> system_bus.remove_signal_receiver(item._property_modified,
>                                   'PropertyModified',
>                                   'org.freedesktop.Hal.Device',
>                                   'org.freedesktop.Hal',
>                                    udi)

remove_signal_receiver() takes and releases a lock (which protects the
signal-match tree from concurrent modification when dbus-python is used
multi-threaded). I'll check other places where this lock is used -
there's probably some code path where it's not being released properly.

Regards,
	Simon
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Message #15 received at 426412@bugs.debian.org (full text, mbox, reply):

From: Tony Houghton <h@realh.co.uk>

To: Simon McVittie <smcv@ianadd.pseudorandom.co.uk>

Cc: 426412@bugs.debian.org

Subject: Re: [Pkg-utopia-maintainers] Bug#426412: python-dbus: system_bus.remove_signal_receiver() freezes

Date: Mon, 28 May 2007 20:22:21 +0100

In <20070528174346.GA30779@celebrin.pseudorandom.co.uk>, you wrote:

> remove_signal_receiver() takes and releases a lock (which protects the
> signal-match tree from concurrent modification when dbus-python is used
> multi-threaded). I'll check other places where this lock is used -
> there's probably some code path where it's not being released properly.

FWIW after I read this I thought perhaps it's a reentrancy problem,
caused by the application trying to call remove_signal_receiver() from a
signal receiver. So I made DevTray defer the calls with
gobject.idle_add() but it still froze. So I was on the wrong track :-(.

-- 
TH * http://www.realh.co.uk

Message #20 received at 426412@bugs.debian.org (full text, mbox, reply):

From: Simon McVittie <smcv@ianadd.pseudorandom.co.uk>

To: Tony Houghton <h@realh.co.uk>, 426412@bugs.debian.org

Subject: Re: [Pkg-utopia-maintainers] Bug#426412: Bug#426412: python-dbus: system_bus.remove_signal_receiver() freezes

Date: Mon, 28 May 2007 19:53:52 +0100

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On Mon, 28 May 2007 at 20:22:21 +0100, Tony Houghton wrote:
> In <20070528174346.GA30779@celebrin.pseudorandom.co.uk>, you wrote:
> 
> > remove_signal_receiver() takes and releases a lock (which protects the
> > signal-match tree from concurrent modification when dbus-python is used
> > multi-threaded). I'll check other places where this lock is used -
> > there's probably some code path where it's not being released properly.
> 
> FWIW after I read this I thought perhaps it's a reentrancy problem,
> caused by the application trying to call remove_signal_receiver() from a
> signal receiver. So I made DevTray defer the calls with
> gobject.idle_add() but it still froze. So I was on the wrong track :-(.

No, it's a different sort of reentrancy problem - in a proxy that tracks
name-owner changes, remove_signal_receiver() can trigger a recursive call
to itself (internally, a match on NameOwnerChanged is removed too) which
attempts to re-take the lock.

I've sent a patch for review upstream; there should be a 0.81.1 in a day or
so.

	Simon
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Message #25 received at 426412-close@bugs.debian.org (full text, mbox, reply):

From: Simon McVittie <smcv@ianadd.pseudorandom.co.uk>

To: 426412-close@bugs.debian.org

Subject: Bug#426412: fixed in dbus-python 0.81.1-1

Date: Tue, 05 Jun 2007 16:17:02 +0000

Source: dbus-python
Source-Version: 0.81.1-1

We believe that the bug you reported is fixed in the latest version of
dbus-python, which is due to be installed in the Debian FTP archive:

dbus-python_0.81.1-1.diff.gz
  to pool/main/d/dbus-python/dbus-python_0.81.1-1.diff.gz
dbus-python_0.81.1-1.dsc
  to pool/main/d/dbus-python/dbus-python_0.81.1-1.dsc
dbus-python_0.81.1.orig.tar.gz
  to pool/main/d/dbus-python/dbus-python_0.81.1.orig.tar.gz
python-dbus_0.81.1-1_i386.deb
  to pool/main/d/dbus-python/python-dbus_0.81.1-1_i386.deb



A summary of the changes between this version and the previous one is
attached.

Thank you for reporting the bug, which will now be closed.  If you
have further comments please address them to 426412@bugs.debian.org,
and the maintainer will reopen the bug report if appropriate.

Debian distribution maintenance software
pp.
Simon McVittie <smcv@ianadd.pseudorandom.co.uk> (supplier of updated dbus-python package)

(This message was generated automatically at their request; if you
believe that there is a problem with it please contact the archive
administrators by mailing ftpmaster@debian.org)


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Format: 1.7
Date: Mon, 04 Jun 2007 14:27:22 +0100
Source: dbus-python
Binary: python-dbus
Architecture: source i386
Version: 0.81.1-1
Distribution: unstable
Urgency: low
Maintainer: Utopia Maintenance Team <pkg-utopia-maintainers@lists.alioth.debian.org>
Changed-By: Simon McVittie <smcv@ianadd.pseudorandom.co.uk>
Description: 
 python-dbus - simple interprocess messaging system (Python interface)
Closes: 368286 408372 409754 416714 426412
Changes: 
 dbus-python (0.81.1-1) unstable; urgency=low
 .
   * New upstream release.
     - Fixes deadlock in remove_signal_receiver() when following name-owner
       changes (Closes: #426412)
   * Package examples, including those referenced by the tutorial
     (Closes: #416714, #368286)
   * Include the Academic Free License version 2.1, not 2.0, in
     debian/copyright, since that's what the dual license includes.
     Closes: #408372 - the duplicated lines in the GPL header also mentioned
     in that bug have already been fixed upstream.
   * python-defaults now includes 2.5 as a supported version, so this upload
     also Closes: #409754.
Files: 
 1abe5013304b52cbb566d157dd7a0b6b 881 devel optional dbus-python_0.81.1-1.dsc
 fc295fa11fe97f19db4841d9bd6d47ab 477052 devel optional dbus-python_0.81.1.orig.tar.gz
 1e89fe24a0488500670b05abbdeb044d 16505 devel optional dbus-python_0.81.1-1.diff.gz
 e4f8f5b685b65ab53b25d1e1ea788ff8 245296 python optional python-dbus_0.81.1-1_i386.deb

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