MDEV-11985 Make innodb_read_only shutdown more robust

If InnoDB is started in innodb_read_only mode such that
recovered incomplete transactions exist at startup
(but the redo logs are clean), an assertion will fail at shutdown,
because there would exist some non-prepared transactions.

logs_empty_and_mark_files_at_shutdown(): Do not wait for incomplete
transactions to finish if innodb_read_only or innodb_force_recovery>=3.
Wait for purge to finish in only one place.

trx_sys_close(): Relax the assertion that would fail first.

trx_free_prepared(): Also free recovered TRX_STATE_ACTIVE transactions
if innodb_read_only or innodb_force_recovery>=3.

Also, revert my earlier fix to MySQL 5.7 because this fix is more generic:

Bug#20874411 INNODB SHUTDOWN HANGS IF INNODB_FORCE_RECOVERY>=3
SKIPPED ANY ROLLBACK

trx_undo_fake_prepared(): Remove.

trx_sys_any_active_transactions(): Revert the changes.

1 files changed, 36 insertions, 0 deletions

diff --git a/mysql-test/suite/innodb/r/read_only_recovery.result b/mysql-test/suite/innodb/r/read_only_recovery.result
new file mode 100644
index 00000000000..7fcbfddf33e
--- /dev/null
+++ b/mysql-test/suite/innodb/r/read_only_recovery.result
@@ -0,0 +1,36 @@
+connect con1, localhost, root;
+CREATE TABLE t(a INT PRIMARY KEY) ENGINE=InnoDB;
+BEGIN;
+INSERT INTO t VALUES(1),(2);
+DELETE FROM t WHERE a=2;
+connection default;
+# Normal MariaDB shutdown would roll back the above transaction.
+# We want the transaction to remain open, so we will kill the server
+# after ensuring that any non-transactional files are clean.
+FLUSH TABLES;
+# Ensure that the above incomplete transaction becomes durable.
+SET GLOBAL innodb_flush_log_at_trx_commit=1;
+BEGIN;
+INSERT INTO t VALUES(0);
+ROLLBACK;
+# Kill and restart: --innodb-force-recovery=3
+disconnect con1;
+SELECT * FROM t;
+a
+SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;
+SELECT * FROM t;
+a
+1
+# Starting with MariaDB 10.2, innodb_read_only implies READ UNCOMMITTED.
+# In earlier versions, this would return the last committed version
+# (empty table)!
+SELECT * FROM t;
+a
+1
+SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED;
+SELECT * FROM t;
+a
+1
+SELECT * FROM t;
+a
+DROP TABLE t;