--- x/include/linux/mbcache.h
+++ y/include/linux/mbcache.h
@@ -51,8 +51,10 @@ static inline void mb_cache_entry_put(st
 	unsigned int cnt = atomic_dec_return(&entry->e_refcnt);
 
 	if (cnt > 0) {
-		if (cnt <= 2)
+		if (cnt <= 2) {
+			smp_mb();
 			wake_up_var(&entry->e_refcnt);
+		}
 		return;
 	}
 	__mb_cache_entry_free(cache, entry);