[glib] thread: simplify 'free' process

[Ryan Lortie <ryanl src gnome org>]

commit 62be9365d9641073185c28c8f0a8fe06fb9a92e0
Author: Ryan Lortie <desrt desrt ca>
Date:   Thu Oct 13 00:18:17 2011 -0400

    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        |   40 ++++++++++++++++++----------------------
 glib/gthreadprivate.h |    1 +
 2 files changed, 19 insertions(+), 22 deletions(-)
---
diff --git a/glib/gthread.c b/glib/gthread.c
index 210d125..29b102d 100644
--- a/glib/gthread.c
+++ b/glib/gthread.c
@@ -667,25 +667,25 @@ void
 /* GThread {{{1 -------------------------------------------------------- */
 
 static void
-g_thread_cleanup (gpointer data)
+g_thread_unref (GThread *thread)
 {
-  if (data)
-    {
-      GRealThread* thread = data;
+  GRealThread *real = (GRealThread *) thread;
 
-      /* 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);
-        }
+  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)
+{
+  g_thread_unref (data);
+}
+
 gpointer
 g_thread_proxy (gpointer data)
 {
@@ -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 bd634bd..27c40f2 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;