Bug#41110: crash with handler command when used concurrently with alter table

Bug#41112: crash in mysql_ha_close_table/get_lock_data with alter table

The problem is that the server wasn't handling robustly failures
to re-open a table during a HANDLER .. READ statement. If the
table needed to be re-opened due to it's storage engine being
altered to one that doesn't support HANDLER, a reference (dangling
pointer) to a closed table could be left in place and accessed in
later attempts to fetch from the table using the handler. Also,
if the server failed to set a error message if the re-open
failed. These problems could lead to server crashes or hangs.

The solution is to remove any references to a closed table and
to set a error if reopening a table during a HANDLER .. READ
statement fails.

mysql-test/include/handler.inc:
  Add test case for Bug#41110 and Bug#41112
mysql-test/r/handler_innodb.result:
  Add test case result for Bug#41110 and Bug#41112
mysql-test/r/handler_myisam.result:
  Add test case result for Bug#41110 and Bug#41112
sql/sql_handler.cc:
  Remove redundant reopen check.
  Set errors even if reopening table.
  Reset TABLE_LIST::table reference when the table is closed.

1 files changed, 26 insertions, 0 deletions

diff --git a/mysql-test/include/handler.inc b/mysql-test/include/handler.inc
index 485b2e881d3..04f4cac831d 100644
--- a/mysql-test/include/handler.inc
+++ b/mysql-test/include/handler.inc
@@ -692,3 +692,29 @@ unlock tables;
 drop table t1;
 --error ER_UNKNOWN_TABLE
 handler t1 read a next;
+
+#
+# Bug#41110: crash with handler command when used concurrently with alter table
+# Bug#41112: crash in mysql_ha_close_table/get_lock_data with alter table
+#
+
+--disable_warnings
+drop table if exists t1;
+--enable_warnings
+create table t1 (a int);
+insert into t1 values (1);
+handler t1 open;
+connect(con1,localhost,root,,);
+send alter table t1 engine=memory;
+connection default;
+let $wait_condition=
+  select count(*) = 1 from information_schema.processlist
+  where state = "rename result table" and info = "alter table t1 engine=memory";
+--source include/wait_condition.inc
+--error ER_ILLEGAL_HA
+handler t1 read a next;
+handler t1 close;
+connection con1;
+--reap
+drop table t1;
+connection default;