From 8e4e6cd9414e0ba301aad7ec24c3d01d67d391b7 Mon Sep 17 00:00:00 2001
From: Noam Postavsky <address@hidden>
Date: Sat, 10 Dec 2016 21:53:53 -0500
Subject: [PATCH v1] Clean up var watcher disabling on thread switching

* src/data.c (inhibit_variable_watchers): New variable.
(notify_variable_watchers): Don't notify watchers it's non-nil.
* src/eval.c (set_inhibit_variable_watchers): New function.
(rebind_for_thread_switch, unbind_for_thread_switch): Disable variable
watchers while setting variables to thread-local values.
---
 src/data.c |  4 ++++
 src/eval.c | 39 +++++++++++++++++++++------------------
 src/lisp.h |  1 +
 3 files changed, 26 insertions(+), 18 deletions(-)

diff --git a/src/data.c b/src/data.c
index 09d94f5..682a669 100644
--- a/src/data.c
+++ b/src/data.c
@@ -1513,12 +1513,16 @@ DEFUN ("get-variable-watchers", Fget_variable_watchers, Sget_variable_watchers,
     : Qnil;
 }
 
+bool inhibit_variable_watchers = false;
+
 void
 notify_variable_watchers (Lisp_Object symbol,
                           Lisp_Object newval,
                           Lisp_Object operation,
                           Lisp_Object where)
 {
+  if (inhibit_variable_watchers) return;
+
   symbol = Findirect_variable (symbol);
 
   ptrdiff_t count = SPECPDL_INDEX ();
diff --git a/src/eval.c b/src/eval.c
index f1e0ae7..15ef5ab 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -3343,30 +3343,34 @@ record_unwind_protect_void (void (*function) (void))
   grow_specpdl ();
 }
 
+static void
+set_inhibit_variable_watchers (int val)
+{
+  inhibit_variable_watchers = val;
+}
+
 void
 rebind_for_thread_switch (void)
 {
   union specbinding *bind;
 
+  ptrdiff_t count = SPECPDL_INDEX ();
+  record_unwind_protect_int (set_inhibit_variable_watchers,
+                             inhibit_variable_watchers);
+  /* Hide implementation of thread-local variables from Lisp code.  */
+  inhibit_variable_watchers = true;
+
   for (bind = specpdl; bind != specpdl_ptr; ++bind)
     {
       if (bind->kind >= SPECPDL_LET)
 	{
 	  Lisp_Object value = specpdl_saved_value (bind);
 	  Lisp_Object sym = specpdl_symbol (bind);
-	  bool was_trapped =
-	    SYMBOLP (sym)
-	    && XSYMBOL (sym)->trapped_write == SYMBOL_TRAPPED_WRITE;
-	  /* FIXME: This is not clean, and if do_specbind signals an
-	     error, the symbol will be left untrapped.  */
-	  if (was_trapped)
-	    XSYMBOL (sym)->trapped_write = SYMBOL_UNTRAPPED_WRITE;
 	  bind->let.saved_value = Qnil;
 	  do_specbind (XSYMBOL (sym), bind, value);
-	  if (was_trapped)
-	    XSYMBOL (sym)->trapped_write = SYMBOL_TRAPPED_WRITE;
 	}
     }
+  unbind_to (count, Qnil);
 }
 
 static void
@@ -3510,24 +3514,23 @@ unbind_for_thread_switch (struct thread_state *thr)
 {
   union specbinding *bind;
 
+  ptrdiff_t count = SPECPDL_INDEX ();
+  record_unwind_protect_int (set_inhibit_variable_watchers,
+                             inhibit_variable_watchers);
+  /* Hide implementation of thread-local variables from Lisp code.  */
+  inhibit_variable_watchers = true;
+
+
   for (bind = thr->m_specpdl_ptr; bind > thr->m_specpdl;)
     {
       if ((--bind)->kind >= SPECPDL_LET)
 	{
 	  Lisp_Object sym = specpdl_symbol (bind);
-	  bool was_trapped =
-	    SYMBOLP (sym)
-	    && XSYMBOL (sym)->trapped_write == SYMBOL_TRAPPED_WRITE;
 	  bind->let.saved_value = find_symbol_value (sym);
-	  /* FIXME: This is not clean, and if do_one_unbind signals an
-	     error, the symbol will be left untrapped.  */
-	  if (was_trapped)
-	    XSYMBOL (sym)->trapped_write = SYMBOL_UNTRAPPED_WRITE;
 	  do_one_unbind (bind, false);
-	  if (was_trapped)
-	    XSYMBOL (sym)->trapped_write = SYMBOL_TRAPPED_WRITE;
 	}
     }
+  unbind_to (count, Qnil);
 }
 
 DEFUN ("special-variable-p", Fspecial_variable_p, Sspecial_variable_p, 1, 1, 0,
diff --git a/src/lisp.h b/src/lisp.h
index 252707c..b16cada 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -605,6 +605,7 @@ INLINE bool (VECTORLIKEP) (Lisp_Object);
 /* Defined in data.c.  */
 extern _Noreturn void wrong_type_argument (Lisp_Object, Lisp_Object);
 extern _Noreturn void wrong_choice (Lisp_Object, Lisp_Object);
+extern bool inhibit_variable_watchers;
 extern void notify_variable_watchers (Lisp_Object symbol, Lisp_Object newval,
                                       Lisp_Object operation, Lisp_Object where);
 
-- 
2.9.3