branches/zip: Merge r2617:r2630 from branches/5.1:

bug#39483 InnoDB hang on adaptive hash because of out of order ::open()
call by MySQL

Forward port of r2629

Under some conditions MySQL calls ::open with search_latch leading
to a deadlock as we try to acquire dict_sys->mutex inside ::open
breaking the latching order. The fix is to release search_latch.

Reviewed by: Heikki

handler/ha_innodb.cc

@@ -2708,6 +2708,14 @@ ha_innobase::open(
 	UT_NOT_USED(test_if_locked);
 
 	thd = ha_thd();
+
+	/* Under some cases MySQL seems to call this function while
+	holding btr_search_latch. This breaks the latching order as
+	we acquire dict_sys->mutex below and leads to a deadlock. */
+	if (thd != NULL) {
+		innobase_release_temporary_latches(ht, thd);
+	}
+
 	normalize_table_name(norm_name, name);
 
 	user_thd = NULL;