Eli Zaretskii <eliz@gnu.org> writes:

> Please attach a debugger and show the backtrace.  The file etc/DEBUG
> explains how to look for a place that infloops, perhaps you could
> follow that and provide a more detailed information.

There's an infinite loop somewhere in exec_byte_code.  I've attached the
backtrace at the point.  Moreover, sending emacs a SIGUSR2 does invoke
the lisp debugger with the following message:

Debugger entered--entering a function:
* #[0 "\301\300\302\"\207" [(0 1) set-match-data evaporate] 3 "\n\n(fn)"]()
* funcall(#[0 "\301\300\302\"\207" [(0 1) set-match-data evaporate] 3 "\n\n(fn)"])
  jit-lock-fontify-now(1111 1611)
  jit-lock-function(1111)
  redisplay_internal\ \(C\ function\)()

If this is not enough, I can try to look into it more later.