Same. Is this on macOS? I'm hoping this problem doesn't exist on Linux. I don't use aggressive-indent-mode, but I've noticed this happens when moving around and editing a clojure buffer which could trigger font locking

yep, it's macOS and doom-emacs (if that's relevant)

Is it unresponsive even to receiving a SIGUSR2?

(I had encountered lsp-mode freezing when combined with clojure-mode lately, but nothing the usr signal would not interrupt)

I'm not using clojure-lsp, but thanks @U9TGHG3LP - I was not aware of SIGUSR2; (I was just forcing quit via Activity Monitor (which I assume does a pkill -9 ).

Next time I get it to reproduce (and manage to rescue it via SIGUSR2), is there anything I can run to help debug what was hogging the UI?

Usually usr2 will cause emacs to enter the debugger, so that you should be able to pinpoint at least some execution point related to the problem.

I’ve had this same issue/symptom too… It happens quite frequently, but not enough to easily debug it. Also on macos M-x emacs-version

GNU Emacs 27.1 (build 1, x86_64-apple-darwin18.7.0, NS appkit-1671.60 Version 10.14.6 (Build 18G95))
 of 2020-08-12

It's happening less frequently now (I think), but unfortunately in my setup pkill -SIGUSR2 just exits emacs (without putting it in a debugger state). This maybe something with the way doom-emacs is configured by default, but I had not investigated further yet.

GNU Emacs 27.1.50 (build 1, x86_64-apple-darwin18.7.0, NS appkit-1671.60 Version 10.14.6 (Build 18G6042)) of 2020-11-17

This just happened to me again. Looks like it had something to do with the modeline, telephone line specifically

Interesting, @U0P7ZBZCK what makes you think that? FWIW I’m running doom-modeline (but my own emacs config)

That’s what came up in the debugger. I didn’t see anything that looked incorrect though. Could have just been a coincidence that’s where emacs was at the time when I sent USR2. I’ll see what happens next time. Hopefully there’s at least a consistency to this problem

FYI I disabled doom-modeline out of interest yesterday, and so far I’ve not seen emacs crash — so could be promising, but too early to say for sure

thanks everyone for contributing data points to this thread!