Re: GDM whacks display

[George <jirka 5z com>]

On Wed, Aug 25, 2004 at 04:13:40AM +0200, Alban Crequy wrote:
> Hello,
> 
> I'm using GDM with old xterminals. They have 32MB of RAM. Sometimes, the
> X server is killed, and the GDM server keep some logs about this:
> 
> "Ping to 10.0.0.11:0 failed, whacking display!"
> 
> This message is generated by the function gdm_slave_alrm_handler in
> daemon/slave.c, line 4466. This seems to be related to the setting
> PingIntervalSeconds.
> 
> Can you explain me what happened and how to resolve the problem?
> 
> This seems not to be a real ping but a ping inside the X connexion,
> isn't it?
> 
> Does GDM kill the X server?
> 
> What is the purpose of this feature?

Sorry about the late reply.  But I have an excuse: it's summer and my inbox
is huge :)

Anyway, unless GDM actually runs the X server binary itself it can't kill it.
What the ping does is that it tryes to communicate with the X server and if
the X server isn't responding in a timely fashion, the process running the
session is killed.  This is to for example handle the situation of the
xterminal box crashing, being turned off, rebooted or perhaps the network
severed.  There is no way for the gdm running on the server to find out that
the x terminal is no longer there, other then yelling at it and seeing if it
responds.  That's what the PingIntervalSeconds does.  Every so many seconds
it talks to the X server and if by the next time it tries to talk to the X
server, it doesn't respond, it assumes the xterminal is no longer there and
just kills anything connected with that X server (xterminal).

I know the "server" terminology is confusing since the "X server" is the
application running on the xterminal and I refer as "server" to the main
computer which runs GDM and to which people log in.  Oh well ...

George

-- 
George <jirka 5z com>
   Man will occasionally stumble over the truth, 
   but most times he will pick himself up and carry on.
                       -- Winston Churchill