bug#17753: Cygwin emacs-X11 core dump

[Eli Zaretskii]

> Date: Wed, 17 Sep 2014 11:17:24 -0400
> From: Ken Brown <kbrown@cornell.edu>
> CC: 17753@debbugs.gnu.org
> 
> On 9/17/2014 6:16 AM, Eli Zaretskii wrote:
> > Anyway, one thing that strikes me (and is consistent across all your
> > reports until now) is that atimer.c functions are run from a separate
> > thread, not the main thread (which is Thread 1).  Ken, is this normal
> > in the Cygwin-w32 build?
> 
> Timer functions in general are run in the main thread.

That's what I'd expect.

> I don't think the backtrace of Thread 2 can be trusted.

But if you look at all the backtraces posted in this bug, they all
tell the same story: thread 2 seems to run run_timers.  So before we
decide this is bogus data, I think we should explore the possibility
that GDB really tells the truth here.

> You can see the expected timer functions running in the main thread, but 
> I have no idea what's going on in Thread 2.  Is run_timers really being 
> called there, or is that just an artifact of a corrupt stack?

Hard to say.  But note that do_pending_atimers calls block_atimers
before it calls run_timers, and block_atimers calls pthread_sigmask.
Could this do something weird to the threads, like switch to another
thread?

> I think I should take this to the Cygwin list, unless you have other 
> suggestions of things to look at.

Discussing this on the Cygwin list is probably the best place.

Thanks.