On 23-Jul-99 Stefan van den Oord wrote:
> On Fri, 23 Jul 1999, Bjoern.Kahl wrote:
>>  I can't give you a line of code, but I know, it is *not*
>>  kpanel (or kde) specific.
>>  
>>  I think it is the windowmanager, because (under fvwm2) a
>>  restart of the windowmanager (via keyboard, mouse moves around,
>>  but doesn't do anything) *or* killing the app brings things
>>  back to live. 
>> 
>>  *Note* : I have *never* seen this on modern, fast maschines. 
>>  Only on my good old 486 @ 66 , 32 MB RAM, slow VLB-gfx-card.
> 
> I have: P150S, 64MB, slow gfx-card.
> 
>>  May be a race condition somewhere.
> 
> I agree it may be a race condition. But I wonder if your hypothesis
> about the reason is true. Note that I cannot even kill X windows with
> CTRL-ALT-BACKSPACE! The system does not react to any event anymore.
> 
> But I have a few other observations that I think may be important:
> - I wrote I was playing MP3s. When the system hung, xmms continued to
>   play, UNTIL THE CURRENT SONG WAS FINISHED. It stopped after that.
> - Also, when I killed KPanel and everything came back to life, all
>   the mouse-clicks I did when it hung were handled, so they were still
>   in the event queue. (The CTRL-ALT-BACKSPACE was not handled by the
>   way, but that may not be a normal X event.)

> This leads to the hypothesis that there is a deadlock, perhaps in
> event processing. If that is true, KPanel was one part of the
> deadlock, because killing it solved the deadlock.

> What do you think?

 I am not sure if I tried to use "ctrl-alt-bs". But couldn't type in
 anything. When I moved around, I havn't seen focus-changes or anything
 else. Keyboard-shortcut for windowactions etc. doesn't worked, but apps
 like xclock or xosview still workt well IIRC. I wondered my self, why
 keyboard-shortcut for restart still worked, but all other didn't :-(

 (I am not at home now, so I can't retry now.)


 I agree to your hypothesis that it is a deadlock in event processing. But
 I still believe it is also a race condition.

 Could somebody with more knowledge about windowmanger give a short
 overview on how eventprocessing (and focusmanagement!) is supposed 
 to work ? Is there a (legal) way for an app to stop event-delivery
 for some time ? What about "GrabKeyboard", "GrabMouse" (don't remember
 exact names).


 Bjoern

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