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Fixed deadlock with LOCK TABLES and ALTER TABLE

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MDEV-21398 Deadlock (server hang) or assertion failure in
Diagnostics_area::set_error_status upon ALTER under lock

This failure could only happen if one locked the same table
multiple times and then did an ALTER TABLE on the table.

Major change is to change all instances of
table->m_needs_reopen= true;
to
table->mark_table_for_reopen();

The main fix for the problem was to ensure that we mark all
instances of the table in the locked_table_list and when we
reopen the tables, we first close all tables before reopening
and locking them.

Other things:
- Don't call thd->locked_tables_list.reopen_tables if there
  are no tables marked for reopen. (performance)
This commit is contained in:
Monty
2020-05-22 18:02:24 +03:00
parent 6462af1c2e
commit be647ff14d
15 changed files with 136 additions and 35 deletions
Download Patch File Download Diff File Expand all files Collapse all files

10
sql/sql_class.h
View File

@ -1823,20 +1823,23 @@ private:
TABLE_LIST *m_locked_tables;
TABLE_LIST **m_locked_tables_last;
/** An auxiliary array used only in reopen_tables(). */
TABLE **m_reopen_array;
TABLE_LIST **m_reopen_array;
/**
Count the number of tables in m_locked_tables list. We can't
rely on thd->lock->table_count because it excludes
non-transactional temporary tables. We need to know
an exact number of TABLE objects.
*/
size_t m_locked_tables_count;
uint m_locked_tables_count;
public:
bool some_table_marked_for_reopen;
Locked_tables_list()
:m_locked_tables(NULL),
m_locked_tables_last(&m_locked_tables),
m_reopen_array(NULL),
m_locked_tables_count(0)
m_locked_tables_count(0),
some_table_marked_for_reopen(0)
{
init_sql_alloc(&m_locked_tables_root, MEM_ROOT_BLOCK_SIZE, 0,
MYF(MY_THREAD_SPECIFIC));
@ -1859,6 +1862,7 @@ public:
bool restore_lock(THD *thd, TABLE_LIST *dst_table_list, TABLE *table,
MYSQL_LOCK *lock);
void add_back_last_deleted_lock(TABLE_LIST *dst_table_list);
void mark_table_for_reopen(THD *thd, TABLE *table);
};