Xvnc goes into loop - taking up 98% CPU, window freezes

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Environment

SUSE Linux Enterprise Server 12 SP5
SUSE Linux Enterprise Server 12 SP4

Situation

Once a vnc window has been created and authenticated, Xvnc goes into a spinning loop on the VNC server , taking up >98% CPU time.
It does appear to be establishing a connection but the window freezes.

Resolution

The Security Update for tigervnc (xorg-x11-Xvnc package), released June 25/2020, includes the patch.

If the problem happens during installation (on zSeries or ppc64le) the xorg-x11-Xvnc RPM can be downloaded to an internal location.
The location and name of the RPM can then be passed to the boot command line via dud parameter:

dud=ftp|http://<internal_location>/xorg-x11-Xvnc-1.6.0-22.14.1.s390x.rpm
or
dud=ftp|http://<internal_location>/xorg-x11-Xvnc-1.6.0-22.14.1.ppc64le.rpm

Note:
On zSeries (s390x) installations it is possible, only using the DUD parameter doesn't help.
In that case remove or uncomment the "manual=1" option in the parm file or kernel command line.
In manual mode linuxrc does not apply driver updates, as manual mode was intended as fallback, when normal work does not work.

Cause

The way how the "SocketServer::processSocketEvent()" was handling the connection needed to be changed.

Disclaimer

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