F11: xorg decision to disable Ctrl-Alt-Backspace

[Ralf Corsepius]

Anders Rayner-Karlsson wrote:
> * Giancarlo Niccolai <gc at falconpl.org> [20090331 12:20]:
>> it may be educated enough to try it. But it is not like that an X  
>> session hang so bad that you have to ctrl-alt-bs it will allow you to  
>> CAF1-6 at all, or will let you to do anything meaningful with it (i.e.  
>> bash may not be able to get the resources to start). When you HAVE to  
>> CABs, it's because you CAN'T CAF1-6.
>>
>> (There was my two cents, so don't expect me to join in this convo; I  
>> just wanted to correct your assumption that you may CAF1-6 away a  
>> situation in which you have to CABs, which is wrong, as another poster  
>> pointed out).
> 
> IIRC, and I believe that was pointed out in this thread as well, is
> that these keypresses are handled in the same way by the same part of
> the X server. If C-A-Bs works, so will C-A-F2 to drop you at a vc.
Not quite. It does so often, but not always, because when C-A-Fn is 
pressed, some memory ( ... file descriptors, inodes etc.) needs to be 
allocated and be swapped around to launch a console.

In case of heavy "memory-hog races", this can easily fail or it may take 
a long time.

> Through past experience, I have never found an instance (since moving
> from XFree86 to Xorg) where the Xserver was wedged in a way that
> switching to a vc did not work, but C-A-Bs did.
I've been in such situations many times ;)

> I have seen plenty of
> X lockups (Xorg intel driver issues in F10) in the last few months and
> not a single one of those were resolvable by C-A-Bs.
Try a classical multi-user workstation-pools setup with "C-A-F<N>" 
disabled - Then, there is no C-A-Fn to press, while a C-A-BS would 
simply kill the user's logging and bring him back to his login.

Another case where this does't work is when switching from "x-terminal" 
to console leaves the console in some unusable state (e.g. when pressing 
C-A-Fn come up with a "black screen" or with a "fly-dirt screen" because 
of some bugs some where).

Ralf