Fix handling of pending signals in wait_reading_process_output (Bug#8869).

* process.c (wait_reading_process_output): Bypass select if
waiting for a cell while ignoring keyboard input, and input is
pending.  Suggested by Jan Djärv.

src/ChangeLog

+2011-06-26  Chong Yidong  <cyd@stupidchicken.com>
+
+	* process.c (wait_reading_process_output): Bypass select if
+	waiting for a cell while ignoring keyboard input, and input is
+	pending.  Suggested by Jan Djärv (Bug#8869).
+
 2011-06-25  Paul Eggert  <eggert@cs.ucla.edu>
 
 	Use gnulib's dup2 module instead of rolling our own.
@@ -351,7 +357,7 @@
 
 2011-06-22  Jim Meyering  <meyering@redhat.com>
 
-	don't leak an XBM-image-sized buffer
+	Don't leak an XBM-image-sized buffer
 	* image.c (xbm_load): Free the image buffer after using it.
 
 2011-06-21  Paul Eggert  <eggert@cs.ucla.edu>

src/process.c

@@ -4479,13 +4479,19 @@ wait_reading_process_output (int time_limit, int microsecs, int read_kbd,
 	    set_waiting_for_input (&timeout);
 	}
 
+      /* Skip the `select' call if input is available and we're
+	 waiting for keyboard input or a cell change (which can be
+	 triggered by processing X events).  In the latter case, set
+	 nfds to 1 to avoid breaking the loop.  */
       no_avail = 0;
-      if (read_kbd && detect_input_pending ())
+      if ((read_kbd || !NILP (wait_for_cell))
+	  && detect_input_pending ())
 	{
-	  nfds = 0;
+	  nfds = read_kbd ? 0 : 1;
 	  no_avail = 1;
 	}
-      else
+
+      if (!no_avail)
 	{
 
 #ifdef ADAPTIVE_READ_BUFFERING