[ltp] ThinkPad X1E4 and P1G5 losing keystrokes under Linux

[Daniel Lezcano]

On 13/04/2023 12:07, Thilo-Alexander Ginkel wrote:
> Hi there,
> 
> I have been using a ThinkPad X1 Extreme Edition Gen 4 and later a P1
> Gen 5 since late 2021. One issue that is driving me nuts is that under
> certain (yet unknown) conditions the ThinkPad seems to be sporadically
> losing keystrokes when running Linux. I reported the issue to Lenovo a
> long time ago, but no solution is in sight.
> 
> Has anyone also observed this behavior with a modern ThinkPad? To be
> able to measure the issue I crafted a little Python script that
> measures the interval between (monotonic) keystrokes and can thus
> pretty easily detect when keystrokes are lost:
> https://github.com/ginkel/thinkfail
> 
> I am also seeing the issue when booting my Laptop from a Kubuntu 22.04
> Live USB image, so I'd rule out any specifics related to my personal
> setup/configuration.
> 
> Any input is much appreciated!

It could be related to an interrupt storm. May be a driver/firmware is 
not handling correctly an interrupt (eg. missing ack) and then the 
kernel is constantly processing the interrupt which may have a higher 
priority than the keyboard interrupt.

You can spot it with irqtop or see if there is a very high number of 
occurrences in /proc/interrupts

I saw a similar problem on another X variant where the touchpad was 
buggy and constantly firing interrupts. The processing of the interrupt 
forced the CPU to run at a higher frequency.

It is sad to see Lenovo paying less and less attention to the Linux 
support :(

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