[X2Go-Dev] Segfault issue with x2goserver.

Mike Gabriel mike.gabriel at das-netzwerkteam.de
Thu May 31 23:43:31 CEST 2012


Hi,

On Do 31 Mai 2012 22:55:48 CEST Nable 80 wrote:

> Good daytime for everyone.
>
> Since 2010 I've been using nxserver (freenx-0.7.3 + nxserver-3.4.0,
> installed into /opt/NX ) on my Debian6 32-bit server ( currently
> kernel 2.6.32-45, here is my /etc/apt/sources.list:
> http://pastebin.ca/2156639 ).
> I didn't use is for about 2-3 months and today I found that when I try
> to connect to my server, it draws some initial graphics and then
> connection interrupts.
> In dmesg i see:
> [4573539.498493] nxagent[5736]: segfault at 0 ip 080e3f03 sp bf9e6900
> error 4 in nxagent[8048000+438000]
> [4573581.591042] nxagent[6371]: segfault at 0 ip 080e3f03 sp bf9a1d90
> error 4 in nxagent[8048000+438000]
> ... (same EIP each time)
>
> I've thought that some update of X11 libs lead it to broke and
> remembered that some some time ago in Debian repos appeared some NX
> libs, so i've looked what depends on them. So, i've found x2goserver.
> I've installed it ( as it described here:
> http://wiki.x2go.org/doku.php/wiki:x2go-repository-debian ), installed
> x2goclient on my Win32 notebook but when i try to connect, i see the
> same thing: X client application (i use openbox+lxpanel there) do some
> requests, in ~/.xsession-errors i can see smth like:
> XIO:  fatal IO error 11 (Resource temporarily unavailable) on X server ":0.0"
>       after 1070 requests (1070 known processed) with 0 events remaining.
> and then no data comes to client. In dmesg i see:
> [4578741.547603] x2goagent[18222]: segfault at 0 ip 080e87b1 sp
> bfe1afd0 error 4 in nxagent[8048000+460000]
> [4578947.507016] x2goagent[20046]: segfault at 0 ip 080e87b1 sp
> bfbf80c0 error 4 in nxagent[8048000+460000]
> ... (same EIP each time)
>
> I've used objdump and found that there program tries to read byte from
> pointer (and doesn't check that it's not NULL) but there are no
> debugging symbols, so i even don't catch what function is it.
>
> Then i've tried installing x2goserver to my new Debian6 64bit server
> (it's almost pure Debian installation) but when i try to connect to
> it, the only application that works is fluxbox, if I try to start
> anything like lxterminal, x2goagent fails at the code that looks very
> similar to 32bit variant:
> [794878.270330] x2goagent[29210]: segfault at 0 ip 00000000004a9bb0 sp
> 00007fff41ee6f60 error 4 in nxagent[400000+4f7000]
> [795053.995418] x2goagent[30256]: segfault at 0 ip 00000000004a9bb0 sp
> 00007fff8ae42160 error 4 in nxagent[400000+4f7000]
>
> If anyone cares, i'll try to send as much additional info as I can,
> just tell what are you interested in. I can even try to debug it but i
> still haven't understood how to build x2go utils from sources.

The issue is known and also NoMachine is heavily working on that. It  
relates to an upgrade of libcairo (1.12.x) that is very commonly used  
in many GTK applications.

There is a maintenance release of nxagent from NoMachine (3.5.0-9)  
that addresses this issue. We have incorporated nxagent-3.5.0-9 in  
nx-libs.git (the NX base we ship with X2Go):
http://code.x2go.org/gitweb?p=nx-libs.git;a=commitdiff;h=222a4a22214608b7f89691eee1c57873c2631705

However, the fix drew in two other problems:

   0. good thing: with nxagent 3.5.0-9 from NoMachine the crashes are gone
   1. BUT: sessions do not resume properly if
   2. BUT: since libcairo 1.10.x (I think) many GTK based applications
      have become so slow!!! Amongst others: gnome-terminal (scrolling!!!)
      and firefox/iceweasel and thunderbird/icedove

Whereas NoMachine has taken notice of (1.), we (that is: Alex) is  
currently investigating the sluggishness described in (2.).

To circumvent the crashes (but have the problems under (1.) and (2.)  
you can install nx-libs (x2goagent, nxagent, libnx-x11) from this URL:

deb http://packages.x2go.org/debian wheezy heuler

(The word ,,heuler'' stands for a baby seal which is the logo of X2Go  
and means that the packages there are fresh out of the oven / nightly  
built).

Greets,
Mike

-- 

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