> > AFAIK there is a lot more to EvStack than multiheading stuff.
> > That isn't even the main point, really. The main point is extending to
> > all console IO devices a generic layered message passing system.
> > Multiheading is just a good example of what EvStack can do easily.
>
> No. Somebody invented a new mechanism for something we already had, and I
> still don't see the reason.
Ok, I'll try to enlighten you.
> The thing we already had and that everybody is already using is called a
> "tty".
There's problem with tty. Big problem: Raw keyboard does not suit well
there. To exploit: Run X on tty9. (X use raw keyboard). Now switch to
tty1. Hold down Alt, press F9. Leave alt pressed, type ABC. Will X see
ABC or Alt-A Alt-B Alt-C? They will see the first one. BUG BUG BUG.
And now: Imagine system with two input streams: keyboard and
mouse. (Again, this is X). Overload system so it swaps heavily (fairly
normal, system should work in such conditions). Move mouse to window 1,
type abc, move mouse to window 2 type def. What will happen? As events
do not have times attached, it is possible that window 1 will receive
abcdef, it is possible that other really weird things will happen. BUG
BUG BUG.
Other problem: Lets' have overloaded system. X's are swapped out. Now
press Ctrl-Alt-F1 abcdef. What will happen? X will receive (after few
seconds of swapping) Ctrl-Alt-F1. But because keyboard was in raw
mode, abcdef will be also interpreted in raw mode, and X has only
option to discard them. But console 1 should receive that keys. You
have just lost my keypresses! BUG BUG BUG.
Pavel
PS: This are just few examples. On sufficiently overloaded system with
fast screen swapping, you'll see few more examples soon.
-- I'm really pavel@atrey.karlin.mff.cuni.cz. Pavel Look at http://atrey.karlin.mff.cuni.cz/~pavel/ ;-).- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.rutgers.edu