Fix minor issues in clib_spinlock_unlock()

Change-Id: I20ce799c9dd57332c06003b466ee7c36169bce98
Signed-off-by: Dave Barach <dave@barachs.net>
diff --git a/src/vppinfra/lock.h b/src/vppinfra/lock.h
index 0cd2b4f..7d24167 100644
--- a/src/vppinfra/lock.h
+++ b/src/vppinfra/lock.h
@@ -71,12 +71,14 @@
 static_always_inline void
 clib_spinlock_unlock (clib_spinlock_t * p)
 {
-  (*p)->lock = 0;
 #if CLIB_DEBUG > 0
   (*p)->frame_address = 0;
   (*p)->pid = 0;
   (*p)->thread_index = 0;
 #endif
+  /* Make sure all writes are complete before releasing the lock */
+  CLIB_MEMORY_BARRIER ();
+  (*p)->lock = 0;
 }
 
 static_always_inline void