From 58fe6b47d4e8580e370a094d8f5768d053aa52c1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marko=20M=C3=A4kel=C3=A4?= <marko.makela@mariadb.com>
Date: Tue, 26 Oct 2021 09:54:37 +0300
Subject: [PATCH] MDEV-26903: Assertion ctx->trx->state == TRX_STATE_ACTIVE on
 DROP INDEX

rollback_inplace_alter_table(): Tolerate a case where the transaction
is not in an active state. If ha_innobase::commit_inplace_alter_table()
failed with a deadlock, the transaction would already have been
rolled back. This omission of error handling was introduced in
commit 1bd681c8b3c5213ce1f7976940a7dc38b48a0d39 (MDEV-25506 part 3).

After commit c3c53926c467c95386ae98d61ada87294bd61478 (MDEV-26554)
it became easier to trigger DB_DEADLOCK during exclusive table lock
acquisition in ha_innobase::commit_inplace_alter_table().

lock_table_low(): Add DBUG injection "innodb_table_deadlock".
---
 mysql-test/suite/innodb/r/innodb-alter-debug.result | 10 ++++++++++
 mysql-test/suite/innodb/t/innodb-alter-debug.test   | 12 ++++++++++++
 storage/innobase/handler/handler0alter.cc           |  2 ++
 storage/innobase/lock/lock0lock.cc                  |  1 +
 4 files changed, 25 insertions(+)

diff --git a/mysql-test/suite/innodb/r/innodb-alter-debug.result b/mysql-test/suite/innodb/r/innodb-alter-debug.result
index 519283536d5..81fc67e55c7 100644
--- a/mysql-test/suite/innodb/r/innodb-alter-debug.result
+++ b/mysql-test/suite/innodb/r/innodb-alter-debug.result
@@ -132,4 +132,14 @@ ALTER TABLE t1 RENAME KEY idx TO idx1, ALGORITHM=COPY;
 disconnect con1;
 connection default;
 DROP TABLE t1;
+#
+# MDEV-26903 Assertion ctx->trx->state == TRX_STATE_ACTIVE on DROP INDEX
+#
+CREATE TABLE t1(a INT PRIMARY KEY, b INT, INDEX(b)) ENGINE=InnoDB;
+SET @save_dbug=@@debug_dbug;
+SET debug_dbug='+d,innodb_table_deadlock';
+ALTER TABLE t1 DROP INDEX b, ALGORITHM=INPLACE;
+ERROR 40001: Deadlock found when trying to get lock; try restarting transaction
+SET debug_dbug=@save_dbug;
+DROP TABLE t1;
 # End of 10.6 tests
diff --git a/mysql-test/suite/innodb/t/innodb-alter-debug.test b/mysql-test/suite/innodb/t/innodb-alter-debug.test
index 7af8e882724..1789ec294e4 100644
--- a/mysql-test/suite/innodb/t/innodb-alter-debug.test
+++ b/mysql-test/suite/innodb/t/innodb-alter-debug.test
@@ -177,6 +177,18 @@ disconnect con1;
 connection default;
 DROP TABLE t1;
 
+--echo #
+--echo # MDEV-26903 Assertion ctx->trx->state == TRX_STATE_ACTIVE on DROP INDEX
+--echo #
+
+CREATE TABLE t1(a INT PRIMARY KEY, b INT, INDEX(b)) ENGINE=InnoDB;
+SET @save_dbug=@@debug_dbug;
+SET debug_dbug='+d,innodb_table_deadlock';
+--error ER_LOCK_DEADLOCK
+ALTER TABLE t1 DROP INDEX b, ALGORITHM=INPLACE;
+SET debug_dbug=@save_dbug;
+DROP TABLE t1;
+
 --echo # End of 10.6 tests
 
 # Wait till all disconnects are completed
diff --git a/storage/innobase/handler/handler0alter.cc b/storage/innobase/handler/handler0alter.cc
index 4fc4751ff1c..adeaf87f7fe 100644
--- a/storage/innobase/handler/handler0alter.cc
+++ b/storage/innobase/handler/handler0alter.cc
@@ -8678,6 +8678,8 @@ inline bool rollback_inplace_alter_table(Alter_inplace_info *ha_alter_info,
     /* If we have not started a transaction yet,
     (almost) nothing has been or needs to be done. */
     dict_sys.lock(SRW_LOCK_CALL);
+  else if (ctx->trx->state == TRX_STATE_NOT_STARTED)
+    goto free_and_exit;
   else if (ctx->new_table)
   {
     ut_ad(ctx->trx->state == TRX_STATE_ACTIVE);
diff --git a/storage/innobase/lock/lock0lock.cc b/storage/innobase/lock/lock0lock.cc
index 234d215d1df..f088d0186bd 100644
--- a/storage/innobase/lock/lock0lock.cc
+++ b/storage/innobase/lock/lock0lock.cc
@@ -3433,6 +3433,7 @@ lock_table_other_has_incompatible(
 static dberr_t lock_table_low(dict_table_t *table, lock_mode mode,
                               que_thr_t *thr, trx_t *trx)
 {
+  DBUG_EXECUTE_IF("innodb_table_deadlock", return DB_DEADLOCK;);
   lock_t *wait_for=
     lock_table_other_has_incompatible(trx, LOCK_WAIT, table, mode);
   dberr_t err= DB_SUCCESS;