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Bug 2052720

Summary:	[RHEL 8.4] Xorg experiencing hanging when resizing/moving mwm windows over x0vncserver (:0.0 and 0.1)
Product:	Red Hat Enterprise Linux 8	Reporter:	Brandon Clark <brclark>
Component:	motif	Assignee:	Carlos Soriano <csoriano>
Status:	CLOSED NOTABUG	QA Contact:	Tomas Pelka <tpelka>
Severity:	medium	Docs Contact:
Priority:	low
Version:	8.4	CC:	alanm, amike, brclark, casantos, jwright, kemyers, mkielian, mkolbas, mpenttil, ndegraef, ofourdan, sbarcomb, tpelka, vikpatil
Target Milestone:	rc	Keywords:	OtherQA, Regression, Triaged
Target Release:	---	Flags:	kemyers: needinfo- pm-rhel: mirror+
Hardware:	Unspecified
OS:	Unspecified
Whiteboard:
Fixed In Version:		Doc Type:	If docs needed, set a value
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2022-07-27 12:41:41 UTC	Type:	Bug
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description Brandon Clark 2022-02-09 21:00:19 UTC

Description of problem:
When using a dual-monitor setup for x0vncserver (a server each on :0.0 and 0.1), Xorg/mwm hangs when resizing/moving windows. Clicking the mouse at the local console of the system clears the hang, but not clicking in the x0vncserver.

Version-Release number of selected component (if applicable):
motif-2.3.4-16.el8.x86_64
tigervnc-server-1.11.0-6.el8.x86_64
tigervnc-server-minimal-1.11.0-6.el8.x86_64
xorg-x11-server-Xorg-1.20.10-1.el8.x86_64

How reproducible:
Customer was able to reproduce consistently.

Steps to Reproduce:
1.Start two x0vncserver instances as follows:

$ export DISPLAY=:0.0; x0vncserver -rfbport=5900 -PasswordFile=/repos/vnc/passwd &
$ export DISPLAY=:0.1; x0vncserver -rfbport=5901 -PasswordFile=/repos/vnc/passwd &

2.Open each display in respective VNC client instance.
3.Attempt to move or resize window

Actual results:
x0vncserver display hangs, requiring input on local console to unhang display.

Expected results:
x0vncserver displays do not hang when moving windows around.

Additional info:
In case listing was opened for, they are using the following card:

NVidia NVS 310 with the GLX 390.144 driver

I personally was unable to properly reproduce the issue due to issue regarding getting display :0.1 working properly.

Comment 49 Kevin Myers 2022-07-27 12:41:41 UTC

This issue occurs when using x0vncserver and mwm as both of these are X11 clients to the same Xserver.

When a window is moved or resized in mwm, the default settings perform an XGrabServer() blocking other X11 clients from the Xserver.  This prevents those X11 clients from drawing the updates on the respective screen.  (The issue does not occur with Xvnc as it creates a virtual display becoming a single client of the X server).

Using the mwm option to disable the 'freezeOnConfig' setting will prevent this from occurring

example:
  $ mwm -xrm "Mwm*freezeOnConfig: False"