Fix hang with large yanksemacs-24

Backport of master commit 0592cefd03f1de2f04b721d07a16e6e0a9e48f73.
This should fix the bug fixed by Mike Crowe's patch in:
https://lists.gnu.org/archive/html/emacs-devel/2015-07/msg00106.html
A problem in this area has been reported by several users; see
Bug#16737, Bug#17101, Bug#17026, Bug#17172, Bug#19320, Bug#20283.
This fix differs from Mike Crowe's patch in that it should avoid a
race condition that could lose SIGIO signals.  ignore_sigio dates
back to the 1980s when some platforms couldn't block signals, and
could only ignore them, which led to races when signals arrived
while being ignored.  We shouldn't have to worry about those old
platforms now.
* src/dispextern.h, src/sysdep.c (ignore_sigio): Remove.
* src/emacs.c (shut_down_emacs):
Don't call ignore_sigio; unrequest_sigio should suffice.
* src/keyboard.c (kbd_buffer_store_buffered_event):
Use unrequest_sigio, not ignore_sigio.
(kbd_buffer_get_event):
Call request_sigio when getting the ball rolling again.

4 files changed, 2 insertions, 13 deletions

diff --git a/src/dispextern.h b/src/dispextern.h
index 239c4425646..cf3d1ecaf9c 100644
--- a/src/dispextern.h
+++ b/src/dispextern.h
@@ -3349,7 +3349,6 @@ void unrequest_sigio (void);
 bool tabs_safe_p (int);
 void init_baud_rate (int);
 void init_sigio (int);
-void ignore_sigio (void);
 
 /* Defined in xfaces.c.  */
 
diff --git a/src/emacs.c b/src/emacs.c
index 9b78a70428e..b5d3ab46a00 100644
--- a/src/emacs.c
+++ b/src/emacs.c
@@ -2028,7 +2028,6 @@ shut_down_emacs (int sig, Lisp_Object stuff)
   /* There is a tendency for a SIGIO signal to arrive within exit,
      and cause a SIGHUP because the input descriptor is already closed.  */
   unrequest_sigio ();
-  ignore_sigio ();
 
   /* Do this only if terminating normally, we want glyph matrices
      etc. in a core dump.  */
diff --git a/src/keyboard.c b/src/keyboard.c
index 945019e8418..77af44a7d46 100644
--- a/src/keyboard.c
+++ b/src/keyboard.c
@@ -3663,8 +3663,7 @@ kbd_buffer_store_event_hold (register struct input_event *event,
           /* Don't read keyboard input until we have processed kbd_buffer.
              This happens when pasting text longer than KBD_BUFFER_SIZE/2.  */
           hold_keyboard_input ();
-          if (!noninteractive)
-            ignore_sigio ();
+          unrequest_sigio ();
           stop_polling ();
         }
 #endif  /* subprocesses */
@@ -3829,6 +3828,7 @@ kbd_buffer_get_event (KBOARD **kbp,
       /* Start reading input again because we have processed enough to
          be able to accept new events again.  */
       unhold_keyboard_input ();
+      request_sigio ();
       start_polling ();
     }
 #endif  /* subprocesses */
diff --git a/src/sysdep.c b/src/sysdep.c
index 01692c2d214..4b4801d58c9 100644
--- a/src/sysdep.c
+++ b/src/sysdep.c
@@ -649,15 +649,6 @@ unrequest_sigio (void)
   interrupts_deferred = 1;
 #endif
 }
-
-void
-ignore_sigio (void)
-{
-#ifdef USABLE_SIGIO
-  signal (SIGIO, SIG_IGN);
-#endif
-}
-
 
 /* Saving and restoring the process group of Emacs's terminal.  */