bug#18684: 24.3; keystrokes come out of order

[Eli Zaretskii <eliz@gnu.org>]

> From: sampo-emacs14@zxid.org
> Date: Fri, 10 Oct 2014 22:41:36 +0000 (GMT)
> Cc: sampo-emacs14@zxid.org
> 
> When typing quickly, the charaters from keystrokes come out of order.
> For example typing 'f' 'o' 'r' 't' may come out as "ofrt" or sometimes
> fully inverse "trof" or some other combination.
> 
> Typing faster makes the problem more likely to reproduce, but even
> quite normal typing speed has problems.
> 
> Higher system load makes the problem more likely, but it manifests
> with load levels as low as 0.25.
> 
> The problem is more prominent in buffers that have onerous font-lock
> configurations. E.g. the default syntax highlighting of c-mode
> makes the problem 4 times as likely as fundamental-mode.
> 
> It seems to me that somehow the input queue processing is not
> strictly FIFO. Instead, the characters that pile up while other
> process is running, are all rendered in inverse order at some
> later time after some newer characters have already been rendered.

When this happens, does "C-h l" (that's the letter ell, not the digit
one) show the keys in the correct order or incorrect one?

Anyway, the Emacs input queue is a strict FIFO.  I suspect some
optional package you use produces this strange effect, as I never saw
anything even close to what you describe.

Try analyzing your ~/.emacs and site-init files for possible culprits.