* xterm.c (x_make_frame_visible): Restore hack which is needed when

input polling is used.  This is still meaningful for Cygwin, see
http://lists.gnu.org/archive/html/emacs-devel/2013-12/msg00351.html.
* keyboard.c (poll_for_input_1, input_polling_used): Define
unconditionally.

3 files changed, 29 insertions, 5 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 89c640bd8c7..60258810fe2 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,11 @@
+2013-12-12  Dmitry Antipov  <dmantipov@yandex.ru>
+
+        * xterm.c (x_make_frame_visible): Restore hack which is needed when
+        input polling is used.  This is still meaningful for Cygwin, see
+        http://lists.gnu.org/archive/html/emacs-devel/2013-12/msg00351.html.
+        * keyboard.c (poll_for_input_1, input_polling_used): Define
+        unconditionally.
+
 2013-12-11  Ken Brown  <kbrown@cornell.edu>
 
         * dispextern.h (erase_phys_cursor):
diff --git a/src/keyboard.c b/src/keyboard.c
index 913a277ca79..915ce9dcf23 100644
--- a/src/keyboard.c
+++ b/src/keyboard.c
@@ -1954,7 +1954,6 @@ int poll_suppress_count;
 
 static struct atimer *poll_timer;
 
-#ifdef HAVE_NTGUI
 /* Poll for input, so that we catch a C-g if it comes in.  */
 void
 poll_for_input_1 (void)
@@ -1963,7 +1962,6 @@ poll_for_input_1 (void)
       && !waiting_for_input)
     gobble_input ();
 }
-#endif
 
 /* Timer callback function for poll_timer.  TIMER is equal to
    poll_timer.  */
@@ -2015,8 +2013,6 @@ start_polling (void)
 #endif
 }
 
-#ifdef HAVE_NTGUI
-
 /* True if we are using polling to handle input asynchronously.  */
 
 bool
@@ -2031,7 +2027,6 @@ input_polling_used (void)
   return 0;
 #endif
 }
-#endif
 
 /* Turn off polling.  */
 
diff --git a/src/xterm.c b/src/xterm.c
index 2c5c01baa84..8498382511b 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -8923,6 +8923,27 @@ x_make_frame_visible (struct frame *f)
       {
         /* Force processing of queued events.  */
         x_sync (f);
+
+        /* This hack is still in use at least for Cygwin.  See
+           http://lists.gnu.org/archive/html/emacs-devel/2013-12/msg00351.html.
+
+           Machines that do polling rather than SIGIO have been
+           observed to go into a busy-wait here.  So we'll fake an
+           alarm signal to let the handler know that there's something
+           to be read.  We used to raise a real alarm, but it seems
+           that the handler isn't always enabled here.  This is
+           probably a bug.  */
+        if (input_polling_used ())
+          {
+            /* It could be confusing if a real alarm arrives while
+               processing the fake one.  Turn it off and let the
+               handler reset it.  */
+            int old_poll_suppress_count = poll_suppress_count;
+            poll_suppress_count = 1;
+            poll_for_input_1 ();
+            poll_suppress_count = old_poll_suppress_count;
+          }
+
         if (XPending (FRAME_X_DISPLAY (f)))
           {
             XEvent xev;