MDEV-16664: Add deprecation warning for innodb_lock_schedule_algorith…

…m=VATS

The setting innodb_lock_schedule_algorithm=VATS that was introduced
in MDEV-11039 (commit 021212b)
causes conflicting exclusive locks to be incorrectly granted to
two transactions. Specifically, in lock_rec_insert_by_trx_age()
the predicate !lock_rec_has_to_wait_in_queue(in_lock) would hold even
though an active transaction is already holding an exclusive lock.
This was observed between two DELETE of the same clustered index record.
The HASH_DELETE invocation in lock_rec_enqueue_waiting() may be related.

Due to lack of progress in diagnosing the problem, we will deprecate the
option and issue a warning that using it may corrupt data. The unsafe
option was enabled between
commit 0c15d1a (MariaDB 10.2.3)
and the parent of
commit 1cc1d04 (MariaDB 10.2.17, 10.3.9).

storage/innobase/handler/ha_innodb.cc

@@ -3750,14 +3750,23 @@ innobase_init(
 		goto error;
 	}
 
+	if (innodb_lock_schedule_algorithm == INNODB_LOCK_SCHEDULE_ALGORITHM_VATS) {
+		ib::warn() << "The parameter innodb_lock_schedule_algorithm"
+			" is deprecated, and the setting"
+			" innodb_lock_schedule_algorithm=vats"
+			" may cause corruption. The parameter may be removed"
+			" in future releases.";
+
 #ifdef WITH_WSREP
-	/* Currently, Galera does not support VATS lock schedule algorithm. */
-	if (innodb_lock_schedule_algorithm == INNODB_LOCK_SCHEDULE_ALGORITHM_VATS
-	    && global_system_variables.wsrep_on) {
-		ib::info() << "For Galera, using innodb_lock_schedule_algorithm=fcfs";
-		innodb_lock_schedule_algorithm = INNODB_LOCK_SCHEDULE_ALGORITHM_FCFS;
+		/* Currently, Galera does not support VATS lock schedule algorithm. */
+		if (global_system_variables.wsrep_on) {
+			ib::info() << "For Galera, using innodb_lock_schedule_algorithm=fcfs";
+			innodb_lock_schedule_algorithm = INNODB_LOCK_SCHEDULE_ALGORITHM_FCFS;
+		}
+#endif /* WITH_WSREP */
 	}
 
+#ifdef WITH_WSREP
 	/* Print deprecation info if xtrabackup is used for SST method */
 	if (global_system_variables.wsrep_on
 	    && wsrep_sst_method