[glib/gobject-performance-2] Fix possible race in lookup_iface_entry_I

[Alexander Larsson <alexl src gnome org>]

commit 9233b07e27be3ffe89695aaa6fc083a36daa037a
Author: Alexander Larsson <alexl redhat com>
Date:   Fri Nov 27 16:53:44 2009 +0100

    Fix possible race in lookup_iface_entry_I
    
    entries can change at any time, since its from an atomicarray. So,
    when we've read entries->offset_index and checked it for the
    limits we need to make sure we use the read value and don't
    re-read the memory again.
    
    Also, to ensure the compiler doesn't do this anyway, make entries
    volatile.

 gobject/gtype.c |    8 +++++---
 1 files changed, 5 insertions(+), 3 deletions(-)
---
diff --git a/gobject/gtype.c b/gobject/gtype.c
index cdce8eb..b216ad8 100644
--- a/gobject/gtype.c
+++ b/gobject/gtype.c
@@ -531,10 +531,11 @@ type_node_new_W (TypeNode    *pnode,
 }
 
 static inline IFaceEntry*
-lookup_iface_entry_I (IFaceEntries *entries,
+lookup_iface_entry_I (volatile IFaceEntries *entries,
 		      TypeNode *iface_node)
 {
   guint8 *offsets;
+  guint offset_index;
   IFaceEntry *check;
   int index;
   IFaceEntry *entry;
@@ -547,10 +548,11 @@ lookup_iface_entry_I (IFaceEntries *entries,
 
      entry = NULL;
      offsets = transaction_data;
+     offset_index = entries->offset_index;
      if (offsets != NULL &&
-	 entries->offset_index < G_ATOMIC_ARRAY_DATA_SIZE(offsets))
+	 offset_index < G_ATOMIC_ARRAY_DATA_SIZE(offsets))
        {
-	 index = offsets[entries->offset_index];
+	 index = offsets[offset_index];
 	 if (index > 0)
 	   {
 	     /* zero means unset, subtract one to get real index */