bug#34235: 27.0.50; lisp profiler does not work

[Eli Zaretskii]

> Date: Wed, 30 Jan 2019 16:15:21 +0000
> Cc: 34235@debbugs.gnu.org
> From: Alan Mackenzie <acm@muc.de>
> 
> It seems to be a Linux problem, at least at my end.
> 
> I see the bug with kernel versions 4.19.17 and 4.19.13.
> I don't see the bug with versions 4.18.19 and 4.19.10.
> 
> It seems some incompatibility between Emacs and Linux was introduced in
> one of the kernels 4.19.1[123].

Maybe some problems with the SIGPROF signal?  Does the signal handler
(handle_profiler_signal) get called at all when you are profiling?

If the signal handler does get called, maybe it's the
backtrace_top_function function that fails?