Segfault in nxagent and screen flickering when maximizing x2go session window #161

HolySephi · 2016-06-27T12:27:12Z

Server O/S: Ubuntu 14.04

x2goserver version: 4.1.0.0-0~~1315~~ubuntu14.04.1
nxagent version: 3.5.99.0-0~git20160625.1249+t

Client O/S: Windows 10
X2Goclient Version: 4.0.5.1

maybe related to #162

Steps to reproduce:

Connect to the server as a normal window (800x600)
Maximize the x2goclient window of the session

I now get a very flickering screen because the resolution of the maximized window gets set multiple times per second:

...
Info: Screen [0] resized to geometry [1920x1027] fullscreen [0].
Info: Screen [0] resized to geometry [1920x1027] fullscreen [0].
Info: Screen [0] resized to geometry [1920x1027] fullscreen [0].
Info: Screen [0] resized to geometry [1920x1027] fullscreen [0].
Info: Screen [0] resized to geometry [1920x1027] fullscreen [0].
Info: Screen [0] resized to geometry [1920x1027] fullscreen [0].
Info: Screen [0] resized to geometry [1920x1027] fullscreen [0].
...

After an undefined amount of time the process segfaults:

x2goagent[733]: segfault at 8 ip 000000000042a263 sp 00007fff95bcec60 error 4 in nxagent[400000+4f0000]

uli42 · 2016-06-27T12:40:04Z

Is this new? Does it also happen with last week's version before the Event patches?

Vom Smartphone gesendet.

----- Ursprüngliche Nachricht -----
Von: "Florian Wicke" [email protected]
Gesendet: ‎27.‎06.‎2016 14:27
An: "ArcticaProject/nx-libs" [email protected]
Betreff: [ArcticaProject/nx-libs] Segfault in nxagent and screen flickeringwhen maximizing x2go session window (#161)

Server O/S: Ubuntu 14.04
x2goserver version: 4.1.0.0-0~~1315~~ubuntu14.04.1
nxagent version: 3.5.99.0-0~git20160625.1249+t
Client O/S: Windows 10
X2Goclient Version: 4.0.5.1
Steps to reproduce:
Connect to the server as a normal window (800x600)
Maximize the x2goclient window of the session
I now get a very flickering screen because the resolution of the maximized window gets set multiple times per second:
...
Info: Screen [0] resized to geometry [1920x1027] fullscreen [0].
Info: Screen [0] resized to geometry [1920x1027] fullscreen [0].
Info: Screen [0] resized to geometry [1920x1027] fullscreen [0].
Info: Screen [0] resized to geometry [1920x1027] fullscreen [0].
Info: Screen [0] resized to geometry [1920x1027] fullscreen [0].
Info: Screen [0] resized to geometry [1920x1027] fullscreen [0].
Info: Screen [0] resized to geometry [1920x1027] fullscreen [0].
...
After an undefined amount of time the process segfaults:
x2goagent[733]: segfault at 8 ip 000000000042a263 sp 00007fff95bcec60 error 4 in nxagent[400000+4f0000]
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HolySephi · 2016-06-27T12:50:41Z

Unfortunately i don't know - i ran into this while debugging #162 but as this segfaults in another location i created a seperate bug and #162 might not be new - i might remember some reports from my first tests with 3.6.0 (3.5.99) when i ran into the segfault from #118 but did not dug any deeper into this issue. We might have multiple things in resolution changing/setting that run into segfaults and not only on session-resume as fixed in #118

uli42 · 2016-06-27T13:18:48Z

Hmm does it also happen with -rrxinerama?

Vom Smartphone gesendet.

----- Ursprüngliche Nachricht -----
Von: "Florian Wicke" [email protected]
Gesendet: ‎27.‎06.‎2016 14:50
An: "ArcticaProject/nx-libs" [email protected]
Cc: "Ulrich Sibiller" [email protected]; "Comment" [email protected]
Betreff: Re: [ArcticaProject/nx-libs] Segfault in nxagent and screenflickering when maximizing x2go session window (#161)

Unfortunately i don't know - i ran into this while debugging #162 but as this segfaults in another location i created a seperate bug and #162 might not be new - i might remember some reports from my first tests with 3.6.0 (3.5.99) when i ran into the segfault from #118 but did not dug any deeper into this issue. We might have multiple things in resolution changing/setting that run into segfaults and not only on session-resume as fixed in #118
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HolySephi · 2016-06-27T14:18:56Z

Using "-rrxinerama" as X2GO_NXAGENT_DEFAULT_OPTIONS xinerama is no longer working as expected. The "flickering" of setting the resolution a few times per second on maximizing is still present and the segfault is still occuring ~~but i'm unable to trigger the segfault in libX11 from #162~~

Sorry, #162 is still happening even with -rrxinerama

uli42 · 2016-06-27T14:28:41Z

So just to get this straight:

it happens with the current source from today
it has not been seen before
it is unsure if it happens since my events fix
there are no SIGHUPs involved

Is that correct?

Do you have coredumps you can examine?

HolySephi · 2016-06-27T14:53:11Z

this is happening with the current nightly packages from the ubuntu repo
http://packages.arctica-project.org/ubuntu-nightly
this and libX11 segfault when resizing x2go session window #162 do not occur on 3.5.0
It could have occured before our fix for nxagent segfaults on session resume #118 but i did not test against this until now
there are no SIGHUPs involved - just screen resizing and sometimes even right after starting the session (might be where the screen size gets set) - the new screen size gets set before the segfault (the taskbar and desktop background image fit the new screen size) correctly
bonus round: this also happens with -rrxinerama as x2goagent parameter

Unfortunately i'm not familiar with creating core dumps from aldready running processes. Since this segfault does not appear if i start nxagent manually i'm unable to use the method i used in #118 to debug the process.

uli42 · 2016-06-27T20:09:43Z

I tried to setup an LXDE session using the nightly arctica build on Ubuntu 14.04. It crashed after some seconds with a coredump. Here's the backtrace:

Core was generated by `/usr/lib/nx/../x2go/bin/x2goagent +extension XFIXES +xinerama -nolisten tcp -no'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0  0x00007fa54f9a8dbb in _XSend () from /usr/lib/x86_64-linux-gnu/libX11.so.6
(gdb) bt
#0  0x00007fa54f9a8dbb in _XSend () from /usr/lib/x86_64-linux-gnu/libX11.so.6
#1  0x00007fa54f9a9265 in _XFlush () from /usr/lib/x86_64-linux-gnu/libX11.so.6
#2  0x00007fa54f9abc75 in _XGetRequest () from /usr/lib/x86_64-linux-gnu/libX11.so.6
#3  0x00007fa550cb0041 in XRenderComposite () from /usr/lib/x86_64-linux-gnu/libXrender.so.1
#4  0x00000000004b392e in ?? ()
#5  0x0000000000437312 in ?? ()
#6  0x0000000000432c59 in ?? ()
#7  0x00000000004314d2 in ?? ()
#8  0x000000000040ea5b in ?? ()
#9  0x00007fa54fec7ec5 in __libc_start_main (main=0x40e680, argc=16, argv=0x7ffd57655e98, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, 
    stack_end=0x7ffd57655e88) at libc-start.c:287
#10 0x000000000040ef38 in ?? ()

I am wondering about the output. Why is it using _XSend from libX11 instead of libNX_X11? @sunweaver: can you please check the build?

uli42 · 2016-06-27T20:35:28Z

I can get the crash by running x2goagent -ac :55 and then DISPLAY=:55 startlxde. Resizing the window immediately produces this segfault:

Program received signal SIGSEGV, Segmentation fault.
0x00007ffff5177dbb in _XSend () from /usr/lib/x86_64-linux-gnu/libX11.so.6
(gdb) bt
#0  0x00007ffff5177dbb in _XSend () from /usr/lib/x86_64-linux-gnu/libX11.so.6
#1  0x00007ffff5178265 in _XFlush () from /usr/lib/x86_64-linux-gnu/libX11.so.6
#2  0x00007ffff517ac75 in _XGetRequest ()
   from /usr/lib/x86_64-linux-gnu/libX11.so.6
#3  0x00007ffff6480d8d in XRenderCompositeText8 ()
   from /usr/lib/x86_64-linux-gnu/libXrender.so.1
#4  0x00000000004b3fb0 in ?? ()
#5  0x0000000000436fbb in ?? ()
#6  0x0000000000432c59 in ?? ()
#7  0x00000000004314d2 in ?? ()
#8  0x000000000040ea5b in ?? ()
#9  0x00007ffff5696ec5 in __libc_start_main (main=0x40e680, argc=3, 
    argv=0x7fffffffdfa8, init=<optimized out>, fini=<optimized out>, 
    rtld_fini=<optimized out>, stack_end=0x7fffffffdf98) at libc-start.c:287
#10 0x000000000040ef38 in ?? ()

When there's no LXDE running resizing works fine without crash (tested empty x2goagent and xterm with and without fvwm running). It works when I add -norender

uli42 · 2016-06-27T22:33:45Z

A self compiled nxagent reveals some more info:

Program received signal SIGSEGV, Segmentation fault.
0x00007ffff5169dbb in _XSend () from /usr/lib/x86_64-linux-gnu/libX11.so.6
(gdb) bt
#0  0x00007ffff5169dbb in _XSend () from /usr/lib/x86_64-linux-gnu/libX11.so.6
#1  0x00007ffff516a265 in _XFlush () from /usr/lib/x86_64-linux-gnu/libX11.so.6
#2  0x00007ffff516cc75 in _XGetRequest () from /usr/lib/x86_64-linux-gnu/libX11.so.6
#3  0x00007ffff6472d8d in XRenderCompositeText8 () from /usr/lib/x86_64-linux-gnu/libXrender.so.1
#4  0x00000000004b7250 in nxagentGlyphs (op=<optimized out>, pSrc=pSrc@entry=0xd50bd0, pDst=0xd87a30, maskFormat=<optimized out>, 
    xSrc=<optimized out>, ySrc=<optimized out>, nlists=nlists@entry=1, elts=0xd86ef0, sizeID=1, glyphsBase=glyphsBase@entry=0x7fffffffcf40)
    at Render.c:1516
#5  0x0000000000436ebb in ProcRenderCompositeGlyphs (client=<optimized out>) at NXrender.c:1787
#6  0x00000000004318d9 in ProcRenderDispatch (client=<optimized out>) at NXrender.c:2522
#7  0x0000000000430a82 in Dispatch () at NXdispatch.c:749
#8  0x000000000040ea5b in main (argc=4, argv=0x7fffffffdd68, envp=<optimized out>) at main.c:437

So I suppose there something wrong with xrender

sunweaver · 2016-06-28T09:58:41Z

11:55 < sunweaver> Sephi: about #161 and #162...
11:57 < sunweaver> do you have anything in /usr/lib/nx/X11/Xinerama on the server?
11:57 < sunweaver> and... is $LD_LIBRARY_PATH set to that path in your X2Go sessions?
11:57 < sunweaver> (the LD_LIBRARY_PATH is probably set, but the dir should not exist).
11:58 < sunweaver> it is old school stuff from nx-libs 3.5.x

sunweaver · 2016-06-28T09:59:20Z

@HolySephi: Can you please provide output of

ldd /usr/lib/nx/bin/nxagent

? Thanks.

HolySephi · 2016-06-28T10:20:11Z

root@LTS-SRV ~ # ldd /usr/lib/nx/bin/nxagent
linux-vdso.so.1 => (0x00007ffe55de1000)
libNX_Xext.so.6 => /usr/lib/x86_64-linux-gnu/libNX_Xext.so.6 (0x00007fcb56265000)
libNX_X11.so.6 => /usr/lib/x86_64-linux-gnu/libNX_X11.so.6 (0x00007fcb55f46000)
libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007fcb55c3f000)
libXpm.so.4 => /usr/lib/x86_64-linux-gnu/libXpm.so.4 (0x00007fcb55a2d000)
libxml2.so.2 => /usr/lib/x86_64-linux-gnu/libxml2.so.2 (0x00007fcb556c6000)
libpixman-1.so.0 => /usr/lib/x86_64-linux-gnu/libpixman-1.so.0 (0x00007fcb5541d000)
libXcomp.so.3 => /usr/lib/x86_64-linux-gnu/libXcomp.so.3 (0x00007fcb5513b000)
libXcompext.so.3 => /usr/lib/x86_64-linux-gnu/libXcompext.so.3 (0x00007fcb54f29000)
libXcompshad.so.3 => /usr/lib/x86_64-linux-gnu/libXcompshad.so.3 (0x00007fcb54d1d000)
libXrender.so.1 => /usr/lib/x86_64-linux-gnu/libXrender.so.1 (0x00007fcb54b13000)
libXfixes.so.3 => /usr/lib/x86_64-linux-gnu/libXfixes.so.3 (0x00007fcb5490d000)
libXfont.so.1 => /usr/lib/x86_64-linux-gnu/libXfont.so.1 (0x00007fcb546db000)
libXcomposite.so.1 => /usr/lib/x86_64-linux-gnu/libXcomposite.so.1 (0x00007fcb544d8000)
libXinerama.so.1 => /usr/lib/x86_64-linux-gnu/libXinerama.so.1 (0x00007fcb542d5000)
libXdmcp.so.6 => /usr/lib/x86_64-linux-gnu/libXdmcp.so.6 (0x00007fcb540ce000)
libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007fcb53d09000)
libdl.so.2 => /lib/x86_64-linux-gnu/libdl.so.2 (0x00007fcb53b05000)
libX11.so.6 => /usr/lib/x86_64-linux-gnu/libX11.so.6 (0x00007fcb537cf000)
libz.so.1 => /lib/x86_64-linux-gnu/libz.so.1 (0x00007fcb535b6000)
liblzma.so.5 => /lib/x86_64-linux-gnu/liblzma.so.5 (0x00007fcb53394000)
/lib64/ld-linux-x86-64.so.2 (0x0000558f1ffb5000)
libpng12.so.0 => /lib/x86_64-linux-gnu/libpng12.so.0 (0x00007fcb5316d000)
libjpeg.so.8 => /usr/lib/x86_64-linux-gnu/libjpeg.so.8 (0x00007fcb52f18000)
libstdc++.so.6 => /usr/lib/x86_64-linux-gnu/libstdc++.so.6 (0x00007fcb52c14000)
libXtst.so.6 => /usr/lib/x86_64-linux-gnu/libXtst.so.6 (0x00007fcb52a0d000)
libXrandr.so.2 => /usr/lib/x86_64-linux-gnu/libXrandr.so.2 (0x00007fcb52803000)
libXdamage.so.1 => /usr/lib/x86_64-linux-gnu/libXdamage.so.1 (0x00007fcb52600000)
libgcc_s.so.1 => /lib/x86_64-linux-gnu/libgcc_s.so.1 (0x00007fcb523e9000)
libfreetype.so.6 => /usr/lib/x86_64-linux-gnu/libfreetype.so.6 (0x00007fcb52146000)
libbz2.so.1.0 => /lib/x86_64-linux-gnu/libbz2.so.1.0 (0x00007fcb51f36000)
libfontenc.so.1 => /usr/lib/x86_64-linux-gnu/libfontenc.so.1 (0x00007fcb51d2d000)
libXext.so.6 => /usr/lib/x86_64-linux-gnu/libXext.so.6 (0x00007fcb51b1b000)
libxcb.so.1 => /usr/lib/x86_64-linux-gnu/libxcb.so.1 (0x00007fcb518fb000)
libXau.so.6 => /usr/lib/x86_64-linux-gnu/libXau.so.6 (0x00007fcb516f7000)

removing the old Xinerama folder does not change the segfaulting behaviour.

HolySephi · 2016-06-28T10:24:29Z

LD_LIBRARY_PATH is directing to:

/usr/lib/nx/X11/Xinerama:/usr/lib/nx/X11

X11 is empty because i deleted Xinerama as mentioned before.

HolySephi · 2016-06-28T10:28:25Z

Adding "-norender" to X2GO_NXAGENT_DEFAULT_OPTIONS does not change anything regarding the segfaults or the "screen flickering" when maximizing the window.

sunweaver · 2016-06-28T10:45:00Z

gcc -m32 -o nxagent -g -O3 -std=c99 -Wall -Wpointer-arith -Wundef    -Wl,-Bsymbolic-functions -Wl,-z,relro -L../../exports/lib   hw/nxagent/miinitext.o                   hw/nxagent/NXwindow.o                    hw/nxagent/NXevents.o                    hw/nxagent/NXproperty.o                  hw/nxagent/NXdixfonts.o                  hw/nxagent/NXglyphcurs.o                 hw/nxagent/NXdispatch.o                  hw/nxagent/NXrender.o                    hw/nxagent/NXglyph.o                     hw/nxagent/NXpicture.o                   hw/nxagent/NXextension.o                 hw/nxagent/NXglxext.o                    hw/nxagent/NXxvdisp.o                    hw/nxagent/NXmiglyph.o                   hw/nxagent/NXmiexpose.o                  hw/nxagent/NXresource.o                  hw/nxagent/NXdamage.o           dix/libdix.a os/libos.a   hw/nxagent/libnxagent.a fb/libfb.a composite/libcomposite.a damageext/libdamage.a  xfixes/libxfixes.a miext/cw/libcw.a         Xext/libext.a xkb/libxkb.a os/libos.a  Xi/libxinput.a                   dbe/libdbe.a record/librecord.a  GL/glx/libglx.a                GL/mesa/GLcore/libGLcore.a randr/librandr.a render/librender.a  mi/libmi.a composite/libcomposite.a damageext/libdamage.a  xfixes/libxfixes.a miext/cw/libcw.a          Xext/libext.a xkb/libxkb.a os/libos.a  Xi/libxinput.a                   dbe/libdbe.a record/librecord.a  GL/glx/libglx.a                GL/mesa/GLcore/libGLcore.a randr/librandr.a render/librender.a hw/nxagent/libnxagent.a mi/libmi.a      -L../../exports/lib   -lNX_Xext -lNX_X11  -lm               -lXpm `pkg-config --libs libxml-2.0` `pkg-config --libs pixman-1` -L ../../../nxcomp -L ../../../nxcompext -L ../../../nxcompshad                 -lXcomp -lXcompext -lXcompshad -lXrender -lNX_X11 -lNX_Xext -lXfixes -lXfont                 -L../../../nx-X11/exports/lib -lXcomposite -lXinerama -lXdmcp -Wl,-rpath-link,../../exports/lib

The above is the linker command as taken from jenkins's last trusty build job for nx-libs.

Some files are duplicated in this cmdline.

sunweaver · 2016-06-28T11:09:56Z

Damn it... another Ubuntu issue that does not exist in Debian.

uli42 · 2016-06-28T11:29:02Z

BTW: it also happens in my self compiled version on Ubuntu

sunweaver · 2016-06-28T11:48:09Z

sunweaver@fd1af6d

HolySephi · 2016-06-30T17:05:43Z

Update: Setting the resolution a few times per second after maximizing the window stops after about one minute and the session behaves normally then

uli42 · 2016-08-21T11:47:10Z

@HolySephi Is this working now?

HolySephi · 2016-08-22T14:46:27Z

No - but there isn't any new version available - still nxagent 3.5.99.0-0.1~git20160707.1403+14.04.nightly.1

tested with the new August-build ofthe windows x2goclient

uli42 · 2016-08-24T12:17:21Z

I have been trying (and failing) to see that with a linux client (I do not have windows at hand). I am unsure what exactly you mean with "Connect to the server as a normal window (800x600)". So you run any desktop environment in there? What environment? Second, "Maximize the x2goclient window of the session" is also not very specific. Are you using the maxinimize button of the window? Or are you pressing Ctrl-Alt-F? Or anything else? Uli

HolySephi · 2016-08-24T14:50:19Z

Just as i said. session setting is set to "window 800x600" and i'm pressing the "maximize window"-button on the top right corner of the window - i created a video file for you:

https://cloud.sephi.de/f/7b813481ba/ (valid for 14 days)

uli42 · 2016-08-24T17:19:26Z

On Wed, Aug 24, 2016 at 4:50 PM, Florian Wicke [email protected] wrote:

Just as i said. session setting is set to "window 800x600" and i'm pressing
the "maximize window"-button on the top right corner of the window - i
created a video file for you:

This could be caused by your desktop inside the session, that is
why I am asking what you are running there. It looks like a Gnome
desktop, but just to be sure...

And in the video I cannow see how you trigger the window
maximization (by clicking the symbol in the window border, not by
other means). This was unclear before.

One further question: Do you have xinerama enabled in that session?

Uli

HolySephi · 2016-08-24T18:54:21Z

XFCE is used as DE and yes, xinerama is enabled.
This does not happen with nxagent 3.5.0 and i'm able to reproduce this on different servers and on the same server while down- and upgrading back and forth between nxagent 3.5.0 and 3.5.99

uli42 · 2016-08-24T19:22:29Z

Ok, thanks. This works for me with the Linux client.

Can you please retry with 3.5.99 with disabled xinerama and the
following /etc/x2go/x2goagent.options:

$ cat /etc/x2go/x2goagent.options
X2GO_NXAGENT_DEFAULT_OPTIONS=""
X2GO_NXAGENT_DEFAULT_OPTIONS+=" +extension XFIXES +xinerama"

For everyone else: don't touch the line below!!!

X2GO_NXAGENT_DEFAULT_OPTIONS+=" -nolisten tcp"

Uli

On Wed, Aug 24, 2016 at 8:54 PM, Florian Wicke [email protected] wrote:

XFCE is used as DE and yes, xinerama is enabled.
This does not happen with nxagent 3.5.0 and i'm able to reproduce this on
different servers and on the same server while down- and upgrading back and
forth between nxagent 3.5.0 and 3.5.99

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HolySephi · 2016-08-25T08:01:13Z

No change in behaviour. Xinerama is disabled in the client and the x2goserver.options are set to your settings (+extension XFIXES instead of -extension)

uli42 · 2016-08-25T08:19:13Z

Hmm, I have no idea of the reason. You could try enabling debugging output by defining TEST and DEBUG in Screen.c (somewhere at the top is a section, where these are undefed currently.). and build a new nxagent. Copy it to the same location your nxagent currently resides at. When starting the session a new session dir in /tmp/.x2go-<username> will be created. Please send me the session.log.

HolySephi · 2016-08-25T10:39:01Z

session.zip

Window resizing starts on line 95

looks like a functions is sending a false return code:
117 nxagentChangeScreenConfig: return 1

uli42 · 2016-08-26T11:29:50Z

Your log shows that there are requests to change the size to same values again and again. I suppose I should add a better check and do nothing then.

There are new nightlies now, please test with those.

HolySephi · 2016-08-29T09:01:33Z

Sorry, it's still the same. The maximised resolution still gets set a few times per second in the session.log:

Info: Screen [0] resized to geometry [784x561] fullscreen [0].
Info: Screen [0] resized to geometry [1920x1027] fullscreen [0].
Info: Screen [0] resized to geometry [1920x1027] fullscreen [0].
Info: Screen [0] resized to geometry [1920x1027] fullscreen [0].
....
Info: Screen [0] resized to geometry [1920x1027] fullscreen [0].
Info: Screen [0] resized to geometry [1920x1027] fullscreen [0].
Info: Screen [0] resized to geometry [1920x1027] fullscreen [0].
Info: Screen [0] resized to geometry [784x561] fullscreen [0].

HolySephi · 2016-12-01T14:52:11Z

So the process isn't segfaulting anymore but the rapid repeated setting of the screen size is still occuring

uli42 · 2016-12-05T12:51:31Z

Hmm, can you please try this:

In Screen.c change line 3685 from

if (nxagentGrabServerInfo.grabstate == SERVER_GRABBED && nxagentGrabServerInfo.client != NULL)

to

if (nxagentGrabServerInfo.grabstate == SERVER_GRABBED)

and recompile. Please also enable DEBUG and TEST in Screen.c.

Does it still happen then?

h31 · 2018-03-05T20:08:27Z

Any news on this issue? Still happens with x2go server 4.1.0.0.

uli42 · 2018-03-05T21:50:29Z

No, sorry. I still cannot reproduce that because I don't use Windows.

Muschelpuster · 2018-03-13T08:55:33Z

We used X2Go for 1 year at Mint XFCE with Windows-Clients and had no problems. Now we have the same issue since 1 week at all clients. I can't reproduce whats happend, but I guess it was triggerd by a Mint-Update. But not on full-screen, only on maximized screen. Full-screen is very unsatisfying, because it's reloading the complete screen on every change between local and remote screen.
I tried to use Mate and it's a little bit better. It's flickering for some times after resizing (15) and then the screen is stable. But on changing between windows at Windows I have to resize the X2Go-Session manually to stop flickering.
According to this thread it's interessint for me to see in sessions.log, that the resolution is not matching with my real screen resolution. In the log I see 1280x697 in full-screen, my physical resolution is 2560x1440. It's 50%, a little bit lower in hight. OK, in the hight I loose the window-frame...
So I calculated 2560x1394 as pre-settings for my client but it does not fixed the problem.

valeryvdr · 2018-03-19T15:38:01Z

Same flickering started few days ago for me. I connect from Windows 10 x2go Client to Debian Stretch x2go server. The issue started right away after I installed updates on Debian. The Debian runs MATE desktop. Besides flickering there is another symptom, I run Windows client off a laptop with a display extended to an external monitor, so the x2go cleint window opens on laptops monitor, if I drug the window to the external monitor, the session crashes, saying that the network connection was closed.

uli42 · 2018-03-19T16:21:54Z

Please update again, the crash is fixed in nx-libs 3.5.99.15. Regarding the flickering see #600 (no fix yet, I am still analyzing) valeryvdr <[email protected]> schrieb am Mo., 19. März 2018, 16:38:

…

Same flickering started few days ago for me. I connect from Windows 10 x2go Client to Debian Stretch x2go server. The issue started right away after I installed updates on Debian. The Debian runs MATE desktop. Besides flickering there is another symptom, I run Windows client off a laptop with a display extended to an external monitor, so the x2go cleint window opens on laptops monitor, if I drug the window to the external monitor, the session crashes, saying that the network connection was closed. — You are receiving this because you commented. Reply to this email directly, view it on GitHub <#161 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AGBw5MKv2VKw1e6kjDuwaf0sdwrSrbIwks5tf9DagaJpZM4I_Cqj> .

valeryvdr · 2018-03-19T17:12:25Z

Confirm, updated Debian just now and the crush does not happen anymore, thanks! Waiting eagerly for the solution for flickering, in a mean time instead of maximising I just resize the window manually to the desktop size, which works fine.

mirco1000 · 2018-03-21T23:47:34Z

Same issue x2go server on debian 9 and x2go client win10 please waiting for your help !
thank you

MattWeatherford · 2018-03-29T21:18:35Z

We are also seeing this, but only on higher latency connections... connections from on campus to campus servers dont seem to have the problem. Off campus connections from home ISP's see it more

We are on Debian 9 with all latest everything:

root@nori:~# uname -a
Linux nori 4.9.0-6-amd64 #1 SMP Debian 4.9.82-1+deb9u2 (2018-02-21) x86_64 GNU/Linux

root@nori:~# apt-show-versions | grep -iE '(nx|x2go)'

libnx-x11-6:amd64/stretch 2:3.5.99.16-1+git20180317.2985+9.main.1 uptodate
libx2go-log-perl:all/stretch 4.1.0.0-0x2go1.2+git20180302.1517+9.main.1 uptodate
libx2go-server-db-perl:amd64/stretch 4.1.0.0-0x2go1.2+git20180302.1517+9.main.1 uptodate
libx2go-server-perl:all/stretch 4.1.0.0-0x2go1.2+git20180302.1517+9.main.1 uptodate
nx-x11-common:all/stretch 2:3.5.99.16-1+git20180317.2985+9.main.1 uptodate
nxagent:amd64/stretch 2:3.5.99.16-1+git20180317.2985+9.main.1 uptodate
x2go-keyring:all/stretch 2012.07.23+git20170305.17+9.main.1 uptodate
x2goserver:amd64/stretch 4.1.0.0-0x2go1.2+git20180302.1517+9.main.1 uptodate
x2goserver-common:amd64/stretch 4.1.0.0-0x2go1.2+git20180302.1517+9.main.1 uptodate
x2goserver-extensions:all/stretch 4.1.0.0-0x2go1.2+git20180302.1517+9.main.1 uptodate
x2goserver-x2goagent:all/stretch 4.1.0.0-0x2go1.2+git20180302.1517+9.main.1 uptodate
x2goserver-xsession:all/stretch 4.1.0.0-0x2go1.2+git20180302.1517+9.main.1 uptodate
root@nori:~#

Original user report:

I have been using X2Go for some time to connect to unix servers. Of late, the screen has started to flicker > and become unresponsive (like does not register clicks). I am not sure why this occurs. I tried to adjust

my connection speed, DPI, and resolution settings but it didn't work. Is it a known issue and would you
be able to provide a solution? It is often observed when I connect through my home connection
(comcast) rather than when on campus.

mbajam · 2018-04-04T02:33:21Z

so I made it up - having same issue (Debian 8 / XP) right after we update our PCs so installed new x2go from reps.. signed there NoMachine label appears in upper left corner instead of x2go (lol guys) and all these happened.. now made purge remove the server, added Saimaa ESR links instead, and it works as should, and without NoMachine label too.. wanted to ask - is there any way to roll back / install old version of server if further needs as above?

sunweaver · 2018-04-20T13:02:48Z

Thus, closing. The issue is not an nx-libs issue, but burried in old versions of VcXsrv. Please upgrade VcXsrv to vcxsrv 1.19.6.4 or newer, if you encounter this issue.

sunweaver · 2018-04-20T13:03:13Z

... see #600, for more info...

HolySephi mentioned this issue Jun 27, 2016

libX11 segfault when resizing x2go session window #162

Closed

sunweaver mentioned this issue Jun 29, 2016

backport _XGetRequest() and _XEatDataWords() #169

Closed

sunweaver self-assigned this Mar 2, 2017

sunweaver added the bug label Mar 2, 2017

sunweaver added this to the 3.6.1.0 milestone Mar 2, 2017

sunweaver closed this as completed Apr 20, 2018

Segfault in nxagent and screen flickering when maximizing x2go session window #161

Segfault in nxagent and screen flickering when maximizing x2go session window #161

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