sql_update.cc:

  mysql_update(): Call handler::unlock_row()
  also in the first while loop.
  This patch is from Heikki,
  and it was approved by Sergei Golubchik.

sql/sql_update.cc

@@ -337,6 +337,8 @@ int mysql_update(THD *thd,
 	    break;
 	  }
 	}
+	else
+	  table->file->unlock_row();
       }
       if (thd->killed && !error)
 	error= 1;				// Aborted