Sporadic keyboard stalls and repeats with libinput in Xorg

[Ken Moffat]

On Mon, Jun 25, 2018 at 01:40:58PM +1000, Peter Hutterer wrote:
> On Sun, Jun 24, 2018 at 10:07:23PM +0100, Ken Moffat wrote:
> > This is weird - *most* of the time libinput (Beyond
> > Linuxfromscratch, recent builds) works fine on my (desktop, running
> > Xorg, usually icewm) machines.  And then from time to time - like
> > this evening, after I awakened this machine from suspend - I starts
> > stalling.  Usually characters will disappear while I am editing in a
> > term, and then eventually appear if I wait.  Sometimes characters
> > seem to get totally lost.  Other times, the last character repeats
> > many times.
> 
> check the journal if you get any "timer offset is negative" warnings. If so,
> the problem is the xserver not polling events quickly enough. but unless you
> have tapping or something else that's timer-sensitive enabled, you may not
> see this message, so absence of it is not a signal that everything is fine..
> 

Hi Peter, thanks for the reply, but I think I've misdiagnosed the
problem.  Two of my machines share a PS/2 keyboard via a KVM switch,
and I now think it was (only) those two which were affected in the
past few weeks.

A few hours ago I tried switching to evdev because things had got so
bad, but the problem continued.  A couple of times, the keyboard
decided to only generate shifted values (!"£$ etc for digits) - on
one occasion I ended up rebooting, the next time I used
Ctrl-Alt-Backspace to kill X, and found that the keyboard was
working unshifted in the tty.

I'd also put in a 4.17.0 kernel, just in case.  On one of the
reboots I got four beeps when the BIOS/EFI prompts appeared, and it
hung, rebooting again was fine.

But I'm also seeing _some_ problems in ttys, although not as many.
I now suspect that the keyboard is starting to fail.

[...]
> 
> the libinput debug-events output has the event node number prefixed for
> every event. But generally you don't need to pass anything other than
> --verbose unless you have e.g. tapping enabled (--enable-tap, see the man
> page for other options).
> 
> I recommend piping the output to a file, that way at least you don't lose
> the data. The verbose output will have various states included such as when
> disable-while-typing enables/disables, it may be useful to track things down
> further.
> 

I managed to screw up writing it to a file, but when I was using
evdev and e problem showed up ( had xev open - typing in that showed
a delay, some characters, and then a stream of repeats for the last
character ).  So, almost certainly not libinput's problem.

Thanks for your time.

ĸen
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