libX11/XCB problems in Hardy

[Chris Cheney]

I still haven't been able to reproduce the libx11/xcb problems with
openoffice.org myself but I have seen lots of reports about this
problem. There should be plenty of affected users in the 185311
duplicates with this problem on openoffice.org to test out potential
fixes though.

Chris

On Fri, 2008-06-20 at 19:33 -0700, Bryce Harrington wrote:
> A couple fairly subtle but serious issues have come to light in Hardy
> relating to XCB-enablement in libX11, and I wanted to send this note
> to notify of a pending change we'll push out once we have a bit more
> verification.
> 
> 
> 185311  locking assertion failure, xorg/libsdl (13 dupes)
>         Particularly afflicting OpenOffice.org users
>         
> 
> 232364  dbus-launch hangs at session start waiting on socket output in libxcb
>         Particularly afflicting Xubuntu users
> 
> 
> Both issues have seemingly been traced to be related to and/or due to
> the enablement of XCB in libx11.  While we're not 100% certain libxcb is
> at fault here, in contacting XCB upstream it seems that locking issues
> are a known issue with the current version and re-architecting work is
> underway to resolve them.
> 
> In the interim, for Hardy I'm considering that we should revert XCB in
> libx11.  I've prepared libx11 debs with XCB disabled for testing
> purposes at the above bug id's.  If we can get this verified as
> resolving the issue (and causing no other notable regression), we can
> decide on putting an SRU through on it.
> 
> I'm guessing that the new libxcb will not be appropriate for a Hardy
> SRU, but we should certainly include it for testing in Intrepid.
> 
> Thanks go to Calc and Cody for their frontline work on the respective
> issues.
> 
> Bryce
> 
> ----- Forwarded message from Barton C Massey <bart at cs.pdx.edu> -----
> 
> Date: Fri, 20 Jun 2008 18:06:23 -0700
> From: Barton C Massey <bart at cs.pdx.edu>
> To: Bryce Harrington <bryce at canonical.com>
> cc: cody-somerville at ubuntu.com, jamey at cs.pdx.edu, tripletj at cs.pdx.edu
> Subject: Re: (X)Ubuntu hang with XCB / dbus-launch 
> X-Spam-Status: No, score=0.5 required=5.0 tests=AWL,EMPTY_MESSAGE autolearn=no
> 	version=3.2.4
> 
> Hi Bryce!  Going well.  I've Cc-ed Jamey and Josh, who
> are the canonical designees for this stuff.  Jamey is biking
> for a week in the San Juans, and thus completely
> uncontactable.  I called Josh and we had a long and
> informative conversation about the state of things.
> 
> This is almost surely a bug in libXCB or Xlib: calling
> XOpenDisplay() arguably should never hang you.
> 
> Jamey and Josh are finishing up "connection handoff" code
> that completely re-architectes the Xlib / XCB interaction,
> and may solve this problem and a bunch of others.  They're
> close to finishing cleaning up this code and shipping it as
> the next release of Xlib/XCB.
> 
> In the meantime, Josh will look at this bug and let you know
> if he sees anything obvious; also, he may ask you to ship
> experimental bits to some users with the problem and see if
> things get all better for them.
> 
> Thanks much for the note.
> 
> 	Bart
> 
> In message <20080620215012.GV9928 at bryceharrington.org> you wrote:
> > We've got a bit of an XCB-related deadlocking problem I'm trying to help
> > Cody with.  Cody is the lead maintainer of Xubuntu, and this particular
> > bug is afflicting a huge proportion of the Xubuntu users.  I'm hoping
> > you could either give us some pointers on debugging this, or introduce
> > us to someone who can help figure it out?
> > 
> > The issue is that during dbus-launch start up, there is a hang following
> > the select() call in _xcb_in_read_block().  I've filed a bug in fdo
> > bugzilla here:
> > 
> >   https://bugs.freedesktop.org/show_bug.cgi?id=16420
> > 
> > We're not certain that it's a libxcb bug, or an underlying bug that
> > libxcb just exposes in this particular environment.  Do you have any
> > advice on what we could do to chase this down (and/or work around it)?
> 
> ----- End forwarded message -----
>