Comment 1 for bug 1281696

There is also IMHO wrong error when turning the desync to ON twice:

pxc2>show global variables like 'wsrep_desync';
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| wsrep_desync | OFF |
+---------------+-------+
1 row in set (0.00 sec)

pxc2>set global wsrep_desync=1;
Query OK, 0 rows affected (0.01 sec)

pxc2>set global wsrep_desync=1;
ERROR 1396 (HY000): Operation 'desync' failed for set global wsrep_desync=1

pxc2>show warnings;
+---------+------+---------------------------------------------------------+
| Level | Code | Message |
+---------+------+---------------------------------------------------------+
| Warning | 1231 | 'wsrep_desync' is already ON. |
| Error | 1396 | Operation 'desync' failed for set global wsrep_desync=1 |
+---------+------+---------------------------------------------------------+
2 rows in set (0.00 sec)

But:

pxc2>set global wsrep_desync=0;
Query OK, 0 rows affected (0.00 sec)

pxc2>set global wsrep_desync=0;
Query OK, 0 rows affected, 1 warning (0.00 sec)

pxc2>show warnings;
+---------+------+--------------------------------+
| Level | Code | Message |
+---------+------+--------------------------------+
| Warning | 1231 | 'wsrep_desync' is already OFF. |
+---------+------+--------------------------------+
1 row in set (0.00 sec)

Tested on both PXC 5.5 and 5.6.