MDEV-17749 Kill during LOCK TABLE ; ALTER TABLE causes assert

The problem was that when LOCK TABLES where unwinded as part of
a killed connection, unlink_all_closed_tables() did not like that
there was uncommited transactions.
Fixed by doing a rollback of any open transaction in this particular case.

1 files changed, 10 insertions, 0 deletions

diff --git a/sql/sql_base.cc b/sql/sql_base.cc
index f793556cf62..e80a78ff802 100644
--- a/sql/sql_base.cc
+++ b/sql/sql_base.cc
@@ -2469,7 +2469,17 @@ unlink_all_closed_tables(THD *thd, MYSQL_LOCK *lock, size_t reopen_count)
 
   /* If no tables left, do an automatic UNLOCK TABLES */
   if (thd->lock && thd->lock->table_count == 0)
+  {
+    /*
+      We have to rollback any open transactions here.
+      This is required in the case where the server has been killed
+      but some transations are still open (as part of locked tables).
+      If we don't do this, we will get an assert in unlock_locked_tables().
+    */
+    ha_rollback_trans(thd, FALSE);
+    ha_rollback_trans(thd, TRUE);
     unlock_locked_tables(thd);
+  }
 }