MDEV-27317 wsrep_checkpoint order violation due to certification failure

With binlogs enabled, debug assertion ut_ad(xid_seqno > wsrep_seqno)
fired in trx_rseg_update_wsrep_checkpoint() when an applier thread
synced the seqno out of order for write set which had failed
certification. This was caused by releasing commit
order too early when binlogs were on, allowing group
commit to run in parallel and commit following transactions
too early.

Fixed by extending the commit order critical section to cover
call to wsrep_set_SE_checkpoint() also when binlogs are on.

Signed-off-by: Julius Goryavsky <julius.goryavsky@mariadb.com>

1 files changed, 8 insertions, 5 deletions

diff --git a/sql/wsrep_high_priority_service.cc b/sql/wsrep_high_priority_service.cc
index c396a9eeae5..96269481559 100644
--- a/sql/wsrep_high_priority_service.cc
+++ b/sql/wsrep_high_priority_service.cc
@@ -472,7 +472,13 @@ int Wsrep_high_priority_service::log_dummy_write_set(const wsrep::ws_handle& ws_
     if (!WSREP_EMULATE_BINLOG(m_thd))
     {
       wsrep_register_for_group_commit(m_thd);
-      ret = ret || cs.provider().commit_order_leave(ws_handle, ws_meta, err);
+      /* wait_for_prior_commit() ensures that all preceding transactions
+         have been committed and seqno has been synced into
+         storage engine. We don't release commit order here yet to
+         avoid following transactions to sync seqno before
+         wsrep_set_SE_checkpoint() below returns. This effectively pauses
+         group commit for the checkpoint operation, but is the only way to
+         ensure proper ordering. */
       m_thd->wait_for_prior_commit();
     }
 
@@ -482,10 +488,7 @@ int Wsrep_high_priority_service::log_dummy_write_set(const wsrep::ws_handle& ws_
     {
       wsrep_unregister_from_group_commit(m_thd);
     }
-    else
-    {
-      ret= ret || cs.provider().commit_order_leave(ws_handle, ws_meta, err);
-    }
+    ret= ret || cs.provider().commit_order_leave(ws_handle, ws_meta, err);
     cs.after_applying();
   }
   DBUG_RETURN(ret);