Bug 26568

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* This PR is closely related to another PR:
*
* "Mouse driver will not properly restart if it dies or the mouse gets unplugged."
*
* These two PR's were prepared at the same time, hence the lack of reference
* numbers.
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Holding ALT, Shift, or probably any other key while moving the mouse around 
will cause the pointer to freeze, and the driver will stop working.  This 
happens at the console, as well as under X 4.0.3 (but *not* 3.3.6)

Once the driver stops, both X and the console are affected.

I can narrow this down to post-4.2-Release at least.  This problem did NOT 
occur with 4.2-Release if I remember right, and definitely doesn't occur 
prior to that.

In fact, another machine I have available, a Compaq Presario 425 (486 DX/4
at 132 MHz, 16 MB RAM, stock Compaq mouse) which runs a GENERIC 4.2-Release
(with only a few config tweaks, no recompiles), does not seem to be
affected by this problem.

How-To-Repeat: 
Move the mouse around, either under X 4.0.3, or in the console, while 
holding another key such as ALT or SHIFT.  The driver should die fairly 
quickly.

Specifically, try ALT + Button 3 + move around.  This is a common binding
to move a window around (fvwm 1.54 default, I set sawfish to mimic it) and
is where I first noticed the problem within X, when I was trying to move a 
window from one viewport to another, adjacent viewport.

Simple mouse clicks with keys pressed don't seem to cause a problem, 

In the case of the console, I noticed it because of a habit of holding
shift while selecting text for cut & paste (in an Xterm, Links and Pine
need Shift + Button1 + Move to select text)

In the case of X 3.3.6, the problem doesn't seem to happen when X is
visible, only when the FreeBSD console is visible.  Once the bug occurs,
however, X is also affected - the pointer freezes and the mouse driver dies.

A Reboot is required to regain mouse operation.  Attempting to sigHUP 
moused, or completely terminate and restart it, does not work.