Re: Emacs uses 100% cpu time

[Richard Stallman]

The way to find out where a program is running during a long operation is
to stop the program several times, making a backtrace each time.  When
you see a pattern start to emerge, then please report it.

Use plain `bt', NOT `bt full' (the latter produces a lot of clutter
which tends to obscure the pattern).

If the pattern you see involves lots of calls to Ffuncall, that means
it is running Lisp code.  In that case only, you need to use
`xbacktrace' in order to look at the Lisp-level backtrace.  You should
do this over and over until you see a pattern in which Lisp functions
are running.

Once you see the pattern, you should follow the instructions in etc/DEBUG
to figure out which of the frames is actually looping.

Of course, if people think this is a bug that is already fixed,
it is worth checking that first before you spend the time to do
the debugging described above.