gsignal: Perform signal unlocked handlers block, unblock and disconnect ops

We used to perform unneeded lock/unlock dances to perform block, unblock
and disconnect actions, and these were potentially unsafe because we
might have looped in data that could be potentially be changed by other
threads.

We could have also done the same by saving the handlers ids in a
temporary array and eventually remove them, but I don't see a reason for
that since we can just keep all locked without the risk of creating
deadlocks.

Coverity CID: #1474757, #1474771, #1474429

1 files changed, 68 insertions, 34 deletions

diff --git a/gobject/gsignal.c b/gobject/gsignal.c
index deaf66e47..8b4fbfea3 100644
--- a/gobject/gsignal.c
+++ b/gobject/gsignal.c
@@ -2618,6 +2618,10 @@ g_signal_connect_data (gpointer       instance,
   return handler_seq_no;
 }
 
+static void
+signal_handler_block_unlocked (gpointer instance,
+                               gulong   handler_id);
+
 /**
  * g_signal_handler_block:
  * @instance: (type GObject.Object): The instance to block the signal handler of.
@@ -2636,12 +2640,20 @@ void
 g_signal_handler_block (gpointer instance,
                         gulong   handler_id)
 {
-  Handler *handler;
-  
   g_return_if_fail (G_TYPE_CHECK_INSTANCE (instance));
   g_return_if_fail (handler_id > 0);
   
   SIGNAL_LOCK ();
+  signal_handler_block_unlocked (instance, handler_id);
+  SIGNAL_UNLOCK ();
+}
+
+static void
+signal_handler_block_unlocked (gpointer instance,
+                               gulong   handler_id)
+{
+  Handler *handler;
+
   handler = handler_lookup (instance, handler_id, NULL, NULL);
   if (handler)
     {
@@ -2653,9 +2665,12 @@ g_signal_handler_block (gpointer instance,
     }
   else
     g_warning ("%s: instance '%p' has no handler with id '%lu'", G_STRLOC, instance, handler_id);
-  SIGNAL_UNLOCK ();
 }
 
+static void
+signal_handler_unblock_unlocked (gpointer instance,
+                                 gulong   handler_id);
+
 /**
  * g_signal_handler_unblock:
  * @instance: (type GObject.Object): The instance to unblock the signal handler of.
@@ -2679,12 +2694,20 @@ void
 g_signal_handler_unblock (gpointer instance,
                           gulong   handler_id)
 {
-  Handler *handler;
-  
   g_return_if_fail (G_TYPE_CHECK_INSTANCE (instance));
   g_return_if_fail (handler_id > 0);
   
   SIGNAL_LOCK ();
+  signal_handler_unblock_unlocked (instance, handler_id);
+  SIGNAL_UNLOCK ();
+}
+
+static void
+signal_handler_unblock_unlocked (gpointer instance,
+                                 gulong   handler_id)
+{
+  Handler *handler;
+
   handler = handler_lookup (instance, handler_id, NULL, NULL);
   if (handler)
     {
@@ -2695,9 +2718,12 @@ g_signal_handler_unblock (gpointer instance,
     }
   else
     g_warning ("%s: instance '%p' has no handler with id '%lu'", G_STRLOC, instance, handler_id);
-  SIGNAL_UNLOCK ();
 }
 
+static void
+signal_handler_disconnect_unlocked (gpointer instance,
+                                    gulong   handler_id);
+
 /**
  * g_signal_handler_disconnect:
  * @instance: (type GObject.Object): The instance to remove the signal handler from.
@@ -2714,12 +2740,20 @@ void
 g_signal_handler_disconnect (gpointer instance,
                              gulong   handler_id)
 {
-  Handler *handler;
-  
   g_return_if_fail (G_TYPE_CHECK_INSTANCE (instance));
   g_return_if_fail (handler_id > 0);
   
   SIGNAL_LOCK ();
+  signal_handler_disconnect_unlocked (instance, handler_id);
+  SIGNAL_UNLOCK ();
+}
+
+static void
+signal_handler_disconnect_unlocked (gpointer instance,
+                                    gulong   handler_id)
+{
+  Handler *handler;
+
   handler = handler_lookup (instance, handler_id, 0, 0);
   if (handler)
     {
@@ -2731,7 +2765,6 @@ g_signal_handler_disconnect (gpointer instance,
     }
   else
     g_warning ("%s: instance '%p' has no handler with id '%lu'", G_STRLOC, instance, handler_id);
-  SIGNAL_UNLOCK ();
 }
 
 /**
@@ -2862,33 +2895,31 @@ g_signal_handler_find (gpointer         instance,
   return handler_seq_no;
 }
 
+typedef void (*CallbackHandlerFunc) (gpointer instance, gulong handler_seq_no);
+
 static guint
-signal_handlers_foreach_matched_R (gpointer         instance,
-				   GSignalMatchType mask,
-				   guint            signal_id,
-				   GQuark           detail,
-				   GClosure        *closure,
-				   gpointer         func,
-				   gpointer         data,
-				   void		  (*callback) (gpointer instance,
-							       gulong   handler_seq_no))
+signal_handlers_foreach_matched_unlocked_R (gpointer             instance,
+                                            GSignalMatchType     mask,
+                                            guint                signal_id,
+                                            GQuark               detail,
+                                            GClosure            *closure,
+                                            gpointer             func,
+                                            gpointer             data,
+                                            CallbackHandlerFunc  callback)
 {
   HandlerMatch *mlist;
   guint n_handlers = 0;
-  
+
   mlist = handlers_find (instance, mask, signal_id, detail, closure, func, data, FALSE);
   while (mlist)
     {
       n_handlers++;
       if (mlist->handler->sequential_number)
-	{
-	  SIGNAL_UNLOCK ();
-	  callback (instance, mlist->handler->sequential_number);
-	  SIGNAL_LOCK ();
-	}
+        callback (instance, mlist->handler->sequential_number);
+
       mlist = handler_match_free1_R (mlist, instance);
     }
-  
+
   return n_handlers;
 }
 
@@ -2930,9 +2961,10 @@ g_signal_handlers_block_matched (gpointer         instance,
   if (mask & (G_SIGNAL_MATCH_CLOSURE | G_SIGNAL_MATCH_FUNC | G_SIGNAL_MATCH_DATA))
     {
       SIGNAL_LOCK ();
-      n_handlers = signal_handlers_foreach_matched_R (instance, mask, signal_id, detail,
-						      closure, func, data,
-						      g_signal_handler_block);
+      n_handlers =
+        signal_handlers_foreach_matched_unlocked_R (instance, mask, signal_id, detail,
+                                                    closure, func, data,
+                                                    signal_handler_block_unlocked);
       SIGNAL_UNLOCK ();
     }
   
@@ -2978,9 +3010,10 @@ g_signal_handlers_unblock_matched (gpointer         instance,
   if (mask & (G_SIGNAL_MATCH_CLOSURE | G_SIGNAL_MATCH_FUNC | G_SIGNAL_MATCH_DATA))
     {
       SIGNAL_LOCK ();
-      n_handlers = signal_handlers_foreach_matched_R (instance, mask, signal_id, detail,
-						      closure, func, data,
-						      g_signal_handler_unblock);
+      n_handlers =
+        signal_handlers_foreach_matched_unlocked_R (instance, mask, signal_id, detail,
+                                                    closure, func, data,
+                                                    signal_handler_unblock_unlocked);
       SIGNAL_UNLOCK ();
     }
   
@@ -3026,9 +3059,10 @@ g_signal_handlers_disconnect_matched (gpointer         instance,
   if (mask & (G_SIGNAL_MATCH_CLOSURE | G_SIGNAL_MATCH_FUNC | G_SIGNAL_MATCH_DATA))
     {
       SIGNAL_LOCK ();
-      n_handlers = signal_handlers_foreach_matched_R (instance, mask, signal_id, detail,
-						      closure, func, data,
-						      g_signal_handler_disconnect);
+      n_handlers =
+        signal_handlers_foreach_matched_unlocked_R (instance, mask, signal_id, detail,
+                                                    closure, func, data,
+                                                    signal_handler_disconnect_unlocked);
       SIGNAL_UNLOCK ();
     }