RE: [PATCH] x86/mce: Restore MCA polling interval halving

[Luck, Tony]

> One aspect remained unanswered:
>
> mce_notify_irq -> mce_work_trigger -> schedule_work(&mce_trigger_work); ->
> mce_do_trigger ->
>
>       call_usermodehelper(mce_helper, mce_helper_argv, NULL, UMH_NO_WAIT);
>
> Is that thing still used?
>
> If so, what is the use case? Is per-chance that mce_helper the userspace
> mcelog tool which the kernel calls here on a MCE?
>
> Or?
>
> Do we need that still?
>
> If not, ripping that out would be a nice, additional simplification.

It is documented here: https://github.com/andikleen/mcelog?tab=readme-ov-file#readme

Three ways to invoke mcelog (cron job, trigger, daemon). That doc describes
trigger as "a newer method", but git blame shows that is part of the original version of the
README,md from 2016. So "new" some time more than 10 years ago.

That doc recommends daemon mode. Also, there's a geologically slow trend moving
from mcelog to rasdaemon.

Maybe we can drop it, but with the caveat that we'd need to revert if anyone ever
complains about breakage to user interface (to avoid the wrath of Torvalds).

I could update the mcelog document to say trigger mode supported in kernel version
<= 7.0

-Tony