[glib] deprecated threads: fix race in GStaticRecMutex

[Ryan Lortie <ryanl src gnome org>]

commit 265f265c677bc5399dbb1cfa449cb4b915a6459f
Author: Mark Janossy <janossy mark gmail com>
Date:   Fri Mar 9 09:54:23 2012 -0500

    deprecated threads: fix race in GStaticRecMutex
    
    The very last access to the 'depth' field of GStaticRecMutex in
    g_static_rec_mutex_unlock_full() was being performed after dropping the
    implementation mutex for the last time.
    
    This allowed the lock to be dropped an additional time if it was
    acquired in another thread right at that instant (which is somewhat
    likely, since another thread could have just been woken up by the lock
    being released).
    
    https://bugzilla.gnome.org/show_bug.cgi?id=670846

 glib/deprecated/gthread-deprecated.c |   13 ++++++++-----
 1 files changed, 8 insertions(+), 5 deletions(-)
---
diff --git a/glib/deprecated/gthread-deprecated.c b/glib/deprecated/gthread-deprecated.c
index 13cd188..a3cba18 100644
--- a/glib/deprecated/gthread-deprecated.c
+++ b/glib/deprecated/gthread-deprecated.c
@@ -807,14 +807,17 @@ g_static_rec_mutex_unlock_full (GStaticRecMutex *mutex)
 {
   GRecMutex *rm;
   gint depth;
+  gint i;
 
   rm = g_static_rec_mutex_get_rec_mutex_impl (mutex);
+
+  /* all access to mutex->depth done while still holding the lock */
   depth = mutex->depth;
-  while (mutex->depth)
-    {
-      mutex->depth--;
-      g_rec_mutex_unlock (rm);
-    }
+  i = mutex->depth;
+  mutex->depth = 0;
+
+  while (i--)
+    g_rec_mutex_unlock (rm);
 
   return depth;
 }