Subject: bug#34618: 26.1.92; timerfd interface causes slowdown on Cygwin

From: Ken Brown <[email-masked]>
Date: Fri, 22 Feb 2019 15:08:33 +0000

Starting with cygwin-3.0.0, Cygwin has the timerfd functions.  But using
them causes Emacs to be very slow to respond to user input.  If I press
a key, there is a 1-2 second delay before Emacs responds.  I'm in the
process of trying to debug this
(http://www.cygwin.org/ml/cygwin/2019-02/msg00364.html).  In the
meantime, the attached patch disables the use of these functions.

OK for the emacs-26 branch (after filling in the bug number)?

Ken
From c0025015ac30ae3c61388eb98f39f495926fe5d1 Mon Sep 17 00:00:00 2001
From: Ken Brown <[email-masked]>
Date: Fri, 22 Feb 2019 09:53:52 -0500
Subject: [PATCH] Disable the timerfd interface on Cygwin

* configure.ac (emacs_cv_have_timerfd): Set to "no" on Cygwin.
---
 configure.ac | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/configure.ac b/configure.ac
index d5e802a961..0783b6455a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -4145,6 +4145,10 @@ AC_DEFUN
 AC_SUBST(TERMCAP_OBJ)
 
 # GNU/Linux-specific timer functions.
+# Bug #?????.
+if test "$opsys" = "cygwin"; then
+  emacs_cv_have_timerfd=no
+fi
 AC_CACHE_CHECK([for timerfd interface], [emacs_cv_have_timerfd],
   [AC_COMPILE_IFELSE(
      [AC_LANG_PROGRAM([[#include <sys/timerfd.h>
-- 
2.17.0