From 62be9365d9641073185c28c8f0a8fe06fb9a92e0 Mon Sep 17 00:00:00 2001
From: Ryan Lortie <desrt@desrt.ca>
Date: Thu, 13 Oct 2011 00:18:17 -0400
Subject: [PATCH] thread: simplify 'free' process

GThread is freed using some very slightly confusing logic: if the thread
was created 'joinable', then the structure is freed after the join()
call succeeds (since we know the thread has exited).  If the thread was
not created 'joinable' then the free is when the thread quits (since we
know 'join' will not be called later).

Move to a straight ref-counting system: 1 ref owned by the thread and 1
extra ref if the thread is joinable.  Both thread quit and joining will
decrease the refcount by 1.
---
 glib/gthread.c        | 42 +++++++++++++++++++-----------------------
 glib/gthreadprivate.h |  1 +
 2 files changed, 20 insertions(+), 23 deletions(-)

diff --git a/glib/gthread.c b/glib/gthread.c
index 210d1254a..29b102d95 100644
--- a/glib/gthread.c
+++ b/glib/gthread.c
@@ -666,24 +666,24 @@ void
 
 /* GThread {{{1 -------------------------------------------------------- */
 
+static void
+g_thread_unref (GThread *thread)
+{
+  GRealThread *real = (GRealThread *) thread;
+
+  if (g_atomic_int_dec_and_test (&real->ref_count))
+    {
+      if (real->ours)
+        g_system_thread_free (real);
+      else
+        g_slice_free (GRealThread, real);
+    }
+}
+
 static void
 g_thread_cleanup (gpointer data)
 {
-  if (data)
-    {
-      GRealThread* thread = data;
-
-      /* We only free the thread structure if it isn't joinable.
-       * If it is, the structure is freed in g_thread_join()
-       */
-      if (!thread->thread.joinable)
-        {
-          if (thread->ours)
-            g_system_thread_free (thread);
-          else
-            g_slice_free (GRealThread, thread);
-        }
-    }
+  g_thread_unref (data);
 }
 
 gpointer
@@ -812,6 +812,7 @@ g_thread_new_internal (const gchar   *name,
   thread = g_system_thread_new (proxy, stack_size, error);
   if (thread)
     {
+      thread->ref_count = joinable ? 2 : 1;
       thread->ours = TRUE;
       thread->thread.joinable = joinable;
       thread->thread.func = func;
@@ -888,14 +889,7 @@ g_thread_join (GThread *thread)
   /* Just to make sure, this isn't used any more */
   thread->joinable = 0;
 
-  /* the thread structure for non-joinable threads is freed upon
-   * thread end. We free the memory here. This will leave a loose end,
-   * if a joinable thread is not joined.
-   */
-  if (real->ours)
-    g_system_thread_free (real);
-  else
-    g_slice_free (GRealThread, real);
+  g_thread_unref (thread);
 
   return retval;
 }
@@ -920,6 +914,8 @@ g_thread_self (void)
        * that are not created by GLib.
        */
       thread = g_slice_new0 (GRealThread);
+      thread->ref_count = 1;
+
       g_private_set (&g_thread_specific_private, thread);
     }
 
diff --git a/glib/gthreadprivate.h b/glib/gthreadprivate.h
index bd634bd96..27c40f21f 100644
--- a/glib/gthreadprivate.h
+++ b/glib/gthreadprivate.h
@@ -59,6 +59,7 @@ struct  _GRealThread
 {
   GThread thread;
 
+  gint ref_count;
   gboolean ours;
   const gchar *name;
   gpointer retval;