MariaDB slave replication stopped after slave upgrade to 10.1.41

Question

After the recent MariaDB 10.1.41 update which happened on 01/Aug/2019, few of our slaves have stopped syncing relay logs from master which is on 10.1.40. Slaves which got automatically updated to 10.1.41 is now having the following status. Slave IO thread is in Preparing state and the logs are not getting written. I did a reset slave and initiated a change master with the positions again but still getting the same. The other slave servers which is in MariaDB 10.1.40, 10.1.33 etc are running as normal. These which got upgraded to 10.1.41 has issue?

Does anyone have any clue on this?

MariaDB [(none)]> show slave status\G
*************************** 1. row ***************************
               Slave_IO_State: NULL
                  Master_Host: a.b.c.d
                  Master_User: xxxxxxxx
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: xxxxxxxxxxxxxx-bin.001135
          Read_Master_Log_Pos: 262316421
               Relay_Log_File: xxxxxxxxxxxxxxxxxxxxx-bin.003410
                Relay_Log_Pos: 4
        Relay_Master_Log_File: xxxxxxxxx-bin.001135
             Slave_IO_Running: Preparing
            Slave_SQL_Running: Yes
              Replicate_Do_DB: xxxxxxxxx
          Replicate_Ignore_DB: 
           Replicate_Do_Table: 
       Replicate_Ignore_Table:
      Replicate_Wild_Do_Table: 
  Replicate_Wild_Ignore_Table: 
                   Last_Errno: 0
                   Last_Error: 
                 Skip_Counter: 0
          Exec_Master_Log_Pos: 262316421
                        Relay_Log_Space: 498
              Until_Condition: None
               Until_Log_File: 
                Until_Log_Pos: 0
           Master_SSL_Allowed: No
           Master_SSL_CA_File: 
           Master_SSL_CA_Path: 
              Master_SSL_Cert: 
            Master_SSL_Cipher: 
               Master_SSL_Key: 
        Seconds_Behind_Master: NULL
Master_SSL_Verify_Server_Cert: No
                Last_IO_Errno: 0
                Last_IO_Error: 
               Last_SQL_Errno: 0
               Last_SQL_Error: 
  Replicate_Ignore_Server_Ids: 
             Master_Server_Id: 111
               Master_SSL_Crl: 
           Master_SSL_Crlpath: 
                   Using_Gtid: No
                  Gtid_IO_Pos: 
      Replicate_Do_Domain_Ids: 
  Replicate_Ignore_Domain_Ids: 
                Parallel_Mode: conservative

Answer 1

Looks like this issue: https://jira.mariadb.org/browse/MDEV-20247

Body must be 30 characters.

Answer 2

The better workaround than downgrading is to set innodb_thread_concurrency to 0 or unset it (default is 0). That made the replication work on 10.1.41 and I did not need to downgrade.