Re: Concurrency, again

[Eli Zaretskii]

> From: Ken Raeburn <address@hidden>
> Date: Thu, 20 Oct 2016 02:08:14 -0400
> Cc: address@hidden
> 
> I just tried a test with a breakpoint in redisplay_internal; it can get 
> called from threads other than the main thread.  As far as I know, we can’t 
> have multiple threads in the redisplay code at the same time, though.

But redisplay_internal will return immediately without doing anything
if it's already running in some other thread.  (And this "running in
some other thread could only happen if that other thread somehow
succeeded to block or yield in the middle of redisplay, which I think
is only possible if it calls Lisp.)