From 2bad3cb3bf8f0cc3f45057061f9a538ecf7742b6 Mon Sep 17 00:00:00 2001

From: =?UTF-8?q?Sebastian=20Dr=C3=B6ge?= <sebastian@centricular.com>

Date: Thu, 14 Feb 2019 17:46:33 +0200

Subject: [PATCH 1/5] Use atomic reference counting for GSource

If attached to a context already it would use a mutex instead but at

least before that the reference counting is not thread-safe currently.

---

 glib/gmain.c | 50 +++++++++++++++-----------------------------------

 1 file changed, 15 insertions(+), 35 deletions(-)

diff --git a/glib/gmain.c b/glib/gmain.c

index 26e68823d..5b91c3117 100644

--- a/glib/gmain.c

+++ b/glib/gmain.c

@@ -374,15 +374,6 @@ typedef struct _GSourceIter

 #define SOURCE_DESTROYED(source) (((source)->flags & G_HOOK_FLAG_ACTIVE) == 0)

 #define SOURCE_BLOCKED(source) (((source)->flags & G_SOURCE_BLOCKED) != 0)

-#define SOURCE_UNREF(source, context)                       \

-   G_STMT_START {                                           \

-    if ((source)->ref_count > 1)                            \

-      (source)->ref_count--;                                \

-    else                                                    \

-      g_source_unref_internal ((source), (context), TRUE);  \

-   } G_STMT_END

-

-

 /* Forward declarations */

 static void g_source_unref_internal             (GSource      *source,

@@ -977,10 +968,10 @@ g_source_iter_next (GSourceIter *iter, GSource **source)

    */

   if (iter->source && iter->may_modify)

-    SOURCE_UNREF (iter->source, iter->context);

+    g_source_unref_internal (iter->source, iter->context, TRUE);

   iter->source = next_source;

   if (iter->source && iter->may_modify)

-    iter->source->ref_count++;

+    g_source_ref (iter->source);

   *source = iter->source;

   return *source != NULL;

@@ -994,7 +985,7 @@ g_source_iter_clear (GSourceIter *iter)

 {

   if (iter->source && iter->may_modify)

     {

-      SOURCE_UNREF (iter->source, iter->context);

+      g_source_unref_internal (iter->source, iter->context, TRUE);

       iter->source = NULL;

     }

 }

@@ -1135,7 +1126,7 @@ g_source_attach_unlocked (GSource      *source,

   source->context = context;

   source->source_id = id;

-  source->ref_count++;

+  g_source_ref (source);

   g_hash_table_insert (context->sources, GUINT_TO_POINTER (id), source);

@@ -1675,7 +1666,7 @@ g_source_set_funcs (GSource     *source,

 {

   g_return_if_fail (source != NULL);

   g_return_if_fail (source->context == NULL);

-  g_return_if_fail (source->ref_count > 0);

+  g_return_if_fail (g_atomic_int_get (&source->ref_count) > 0);

   g_return_if_fail (funcs != NULL);

   source->source_funcs = funcs;

@@ -2050,19 +2041,9 @@ g_source_set_name_by_id (guint           tag,

 GSource *

 g_source_ref (GSource *source)

 {

-  GMainContext *context;

-  

   g_return_val_if_fail (source != NULL, NULL);

-  context = source->context;

-

-  if (context)

-    LOCK_CONTEXT (context);

-

-  source->ref_count++;

-

-  if (context)

-    UNLOCK_CONTEXT (context);

+  g_atomic_int_inc (&source->ref_count);

   return source;

 }

@@ -2078,12 +2059,11 @@ g_source_unref_internal (GSource      *source,

   GSourceCallbackFuncs *old_cb_funcs = NULL;

   g_return_if_fail (source != NULL);

-  

+

   if (!have_lock && context)

     LOCK_CONTEXT (context);

-  source->ref_count--;

-  if (source->ref_count == 0)

+  if (g_atomic_int_dec_and_test (&source->ref_count))

     {

       TRACE (GLIB_SOURCE_BEFORE_FREE (source, context,

                                       source->source_funcs->finalize));

@@ -2107,20 +2087,20 @@ g_source_unref_internal (GSource      *source,

 	{

           /* Temporarily increase the ref count again so that GSource methods

            * can be called from finalize(). */

-          source->ref_count++;

+          g_atomic_int_inc (&source->ref_count);

 	  if (context)

 	    UNLOCK_CONTEXT (context);

 	  source->source_funcs->finalize (source);

 	  if (context)

 	    LOCK_CONTEXT (context);

-          source->ref_count--;

+          g_atomic_int_add (&source->ref_count, -1);

 	}

       if (old_cb_funcs)

         {

           /* Temporarily increase the ref count again so that GSource methods

            * can be called from callback_funcs.unref(). */

-          source->ref_count++;

+          g_atomic_int_inc (&source->ref_count);

           if (context)

             UNLOCK_CONTEXT (context);

@@ -2128,7 +2108,7 @@ g_source_unref_internal (GSource      *source,

           if (context)

             LOCK_CONTEXT (context);

-          source->ref_count--;

+          g_atomic_int_add (&source->ref_count, -1);

         }

       g_free (source->name);

@@ -3201,7 +3181,7 @@ g_main_dispatch (GMainContext *context)

 	    }

 	}

-      SOURCE_UNREF (source, context);

+      g_source_unref_internal (source, context, TRUE);

     }

   g_ptr_array_set_size (context->pending_dispatches, 0);

@@ -3440,7 +3420,7 @@ g_main_context_prepare (GMainContext *context,

   for (i = 0; i < context->pending_dispatches->len; i++)

     {

       if (context->pending_dispatches->pdata[i])

-	SOURCE_UNREF ((GSource *)context->pending_dispatches->pdata[i], context);

+        g_source_unref_internal ((GSource *)context->pending_dispatches->pdata[i], context, TRUE);

     }

   g_ptr_array_set_size (context->pending_dispatches, 0);

@@ -3788,7 +3768,7 @@ g_main_context_check (GMainContext *context,

       if (source->flags & G_SOURCE_READY)

 	{

-	  source->ref_count++;

+          g_source_ref (source);

 	  g_ptr_array_add (context->pending_dispatches, source);

 	  n_ready++;

-- 

2.31.1