MDEV-23328 Server hang due to Galera lock conflict resolution

Mutex order violation when wsrep bf thread kills a conflicting trx,
the stack is

          wsrep_thd_LOCK()
          wsrep_kill_victim()
          lock_rec_other_has_conflicting()
          lock_clust_rec_read_check_and_lock()
          row_search_mvcc()
          ha_innobase::index_read()
          ha_innobase::rnd_pos()
          handler::ha_rnd_pos()
          handler::rnd_pos_by_record()
          handler::ha_rnd_pos_by_record()
          Rows_log_event::find_row()
          Update_rows_log_event::do_exec_row()
          Rows_log_event::do_apply_event()
          Log_event::apply_event()
          wsrep_apply_events()

and mutexes are taken in the order

          lock_sys->mutex -> victim_trx->mutex -> victim_thread->LOCK_thd_data

When a normal KILL statement is executed, the stack is

          innobase_kill_query()
          kill_handlerton()
          plugin_foreach_with_mask()
          ha_kill_query()
          THD::awake()
          kill_one_thread()

        and mutexes are

          victim_thread->LOCK_thd_data -> lock_sys->mutex -> victim_trx->mutex

This patch is the plan D variant for fixing potetial mutex locking
order exercised by BF aborting and KILL command execution.

In this approach, KILL command is replicated as TOI operation.
This guarantees total isolation for the KILL command execution
in the first node: there is no concurrent replication applying
and no concurrent DDL executing. Therefore there is no risk of
BF aborting to happen in parallel with KILL command execution
either. Potential mutex deadlocks between the different mutex
access paths with KILL command execution and BF aborting cannot
therefore happen.

TOI replication is used, in this approach,  purely as means
to provide isolated KILL command execution in the first node.
KILL command should not (and must not) be applied in secondary
nodes. In this patch, we make this sure by skipping KILL
execution in secondary nodes, in applying phase, where we
bail out if applier thread is trying to execute KILL command.
This is effective, but skipping the applying of KILL command
could happen much earlier as well.

This also fixed unprotected calls to wsrep_thd_abort
that will use wsrep_abort_transaction. This is fixed
by holding THD::LOCK_thd_data while we abort transaction.

Reviewed-by: Jan Lindström <jan.lindstrom@mariadb.com>

1 files changed, 5 insertions, 18 deletions

diff --git a/storage/innobase/lock/lock0wait.cc b/storage/innobase/lock/lock0wait.cc
index 59405e4c1ad..5eb03f668b3 100644
--- a/storage/innobase/lock/lock0wait.cc
+++ b/storage/innobase/lock/lock0wait.cc
@@ -1,7 +1,7 @@
 /*****************************************************************************
 
 Copyright (c) 1996, 2016, Oracle and/or its affiliates. All Rights Reserved.
-Copyright (c) 2014, 2020, MariaDB Corporation.
+Copyright (c) 2014, 2021, MariaDB Corporation.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -184,13 +184,11 @@ lock_wait_table_reserve_slot(
 check if lock timeout was for priority thread,
 as a side effect trigger lock monitor
 @param[in]    trx    transaction owning the lock
-@param[in]    locked true if trx and lock_sys.mutex is ownd
 @return	false for regular lock timeout */
 static
 bool
 wsrep_is_BF_lock_timeout(
-	const trx_t*	trx,
-	bool		locked = true)
+	const trx_t*	trx)
 {
 	bool long_wait= (trx->error_state != DB_DEADLOCK &&
 			 trx->is_wsrep() &&
@@ -204,21 +202,10 @@ wsrep_is_BF_lock_timeout(
 		ib::info() << "WSREP: BF lock wait long for trx:" << trx->id
 			   << " query: " << wsrep_thd_query(trx->mysql_thd);
 
-		if (!locked)
-			lock_mutex_enter();
-
-		ut_ad(lock_mutex_own());
-
-		trx_print_latched(stderr, trx, 3000);
-		/* Note this will release lock_sys mutex */
-		lock_print_info_all_transactions(stderr);
-
-		if (locked)
-			lock_mutex_enter();
-
 		return was_wait;
-	} else
+	} else {
 		return false;
+	}
 }
 #endif /* WITH_WSREP */
 
@@ -404,7 +391,7 @@ lock_wait_suspend_thread(
 	    && wait_time > (double) lock_wait_timeout
 #ifdef WITH_WSREP
 	    && (!trx->is_wsrep()
-		|| (!wsrep_is_BF_lock_timeout(trx, false)
+		|| (!wsrep_is_BF_lock_timeout(trx)
 		    && trx->error_state != DB_DEADLOCK))
 #endif /* WITH_WSREP */
 	    ) {