Macros
#define	GET_LOCK_UNLOCK 1

#define	GET_LOCK_STORE_LOCKS 2

Functions
static MYSQL_LOCK *	get_lock_data (THD thd, TABLE *table_ptr, size_t count, uint flags)
	Get lock structures from table structs and initialize locks. More...

static int	lock_external (THD thd, TABLE *table, uint count)

static int	unlock_external (THD thd, TABLE *table, uint count)
	Unlock a set of external. More...

static void	print_lock_error (int error, const char *)

static int	lock_tables_check (THD thd, TABLE *tables, size_t count, uint flags)
	Perform semantic checks for mysql_lock_tables. More...

static void	reset_lock_data (MYSQL_LOCK *sql_lock)
	Reset lock type in lock data. More...

static void	track_table_access (THD thd, TABLE *tables, size_t count)
	Scan array of tables for access types; update transaction tracker accordingly. More...

static void	reset_lock_data_and_free (MYSQL_LOCK **mysql_lock)
	Reset lock type in lock data and free. More...

MYSQL_LOCK *	mysql_lock_tables (THD thd, TABLE *tables, size_t count, uint flags)
	Lock tables. More...

void	mysql_unlock_tables (THD thd, MYSQL_LOCK sql_lock)

void	mysql_unlock_some_tables (THD thd, TABLE *table, uint count)
	Unlock some of the tables locked by mysql_lock_tables. More...

void	mysql_unlock_read_tables (THD thd, MYSQL_LOCK sql_lock)
	unlock all tables locked for read. More...

void	mysql_lock_remove (THD thd, MYSQL_LOCK locked, TABLE *table)
	Try to find the table in the list of locked tables. More...

void	mysql_lock_abort_for_thread (THD thd, TABLE table)
	Abort one thread / table combination. More...

MYSQL_LOCK *	mysql_lock_merge (MYSQL_LOCK a, MYSQL_LOCK b)

bool	lock_schema_name (THD thd, const char db)
	Obtain an exclusive metadata lock on a schema name. More...

bool	lock_tablespace_names (THD thd, Tablespace_hash_set tablespace_set, ulong lock_wait_timeout, MEM_ROOT *mem_root)
	Acquire IX MDL lock each tablespace name from the given set. More...

bool	lock_object_name (THD thd, MDL_key::enum_mdl_namespace mdl_type, const char db, const char *name)
	Obtain an exclusive metadata lock on an object name. More...

bool	acquire_shared_global_read_lock (THD *thd, unsigned long lock_wait_timeout)
	Acquire protection against the global read lock. More...

bool	Global_read_lock::lock_global_read_lock (THD *thd)
	Take global read lock, wait if there is protection against lock. More...

void	Global_read_lock::unlock_global_read_lock (THD *thd)
	Unlock global read lock. More...

bool	Global_read_lock::make_global_read_lock_block_commit (THD *thd)
	Make global read lock also block commits. More...

void	Global_read_lock::set_explicit_lock_duration (THD *thd)
	Set explicit duration for metadata locks which are used to implement GRL. More...

Variables
static int	thr_lock_errno_to_mysql []

static std::atomic< int32 >	Global_read_lock::m_atomic_active_requests

Detailed Description

Macro Definition Documentation

◆ GET_LOCK_STORE_LOCKS

#define GET_LOCK_STORE_LOCKS 2

◆ GET_LOCK_UNLOCK

#define GET_LOCK_UNLOCK 1

Function Documentation

◆ acquire_shared_global_read_lock()

bool acquire_shared_global_read_lock	(	THD *	thd,
		unsigned long	lock_wait_timeout
	)

Acquire protection against the global read lock.

Acquire an intention exclusive lock to protect against others setting the global read lock. We follow the naming used by the backup lock help functions when naming this function.

Parameters

thd	Thread context.
lock_wait_timeout	Time to wait for lock acquisition.

Return values

false	No error, meta data lock acquired.
true	Error, meta data lock not acquired.

◆ get_lock_data()

static MYSQL_LOCK * get_lock_data	(	THD *	thd,
		TABLE **	table_ptr,
		size_t	count,
		uint	flags
	)

static

Get lock structures from table structs and initialize locks.

Parameters

thd	Thread handler
table_ptr	Pointer to tables that should be locks
count	Number of tables
flags	One of: GET_LOCK_UNLOCK : If we should send TL_IGNORE to store lock GET_LOCK_STORE_LOCKS : Store lock info in TABLE

◆ lock_external()

static int lock_external	(	THD *	thd,
		TABLE **	table,
		uint	count
	)

static

◆ lock_global_read_lock()

bool Global_read_lock::lock_global_read_lock ( THD * thd )

Take global read lock, wait if there is protection against lock.

If the global read lock is already taken by this thread, then nothing is done.

See also "Handling of global read locks" above.

Parameters

thd	Reference to thread.

Return values

False	Success, global read lock set, commits are NOT blocked.
True	Failure, thread was killed.

◆ lock_object_name()

bool lock_object_name	(	THD *	thd,
		MDL_key::enum_mdl_namespace	mdl_type,
		const char *	db,
		const char *	name
	)

Obtain an exclusive metadata lock on an object name.

Parameters

thd	Thread handle.
mdl_type	Object type (currently functions, procedures and events can be name-locked).
db	The schema the object belongs to.
name	Object name in the schema.

This function cannot be called while holding LOCK_open_mutex. This invariant is enforced by asserts in MDL_context::acquire_locks. To avoid deadlocks, we do not try to obtain exclusive metadata locks in LOCK TABLES mode, since in this mode there may be other metadata locks already taken by the current connection, and we must not wait for MDL locks while holding locks.

Note: name is converted to lowercase before the lock is acquired since stored routine and event names are case insensitive.

Return values

false	Success.
true	Failure: we're in LOCK TABLES mode, or out of memory, or this connection was killed.

◆ lock_schema_name()

bool lock_schema_name	(	THD *	thd,
		const char *	db
	)

Obtain an exclusive metadata lock on a schema name.

Parameters

thd	Thread handle.
db	The database name.

This function cannot be called while holding LOCK_open mutex. To avoid deadlocks, we do not try to obtain exclusive metadata locks in LOCK TABLES mode, since in this mode there may be other metadata locks already taken by the current connection, and we must not wait for MDL locks while holding locks.

Return values

false	Success.
true	Failure: we're in LOCK TABLES mode, or out of memory, or this connection was killed.

◆ lock_tables_check()

static int lock_tables_check	(	THD *	thd,
		TABLE **	tables,
		size_t	count,
		uint	flags
	)

static

Perform semantic checks for mysql_lock_tables.

Parameters

thd	The current thread
tables	The tables to lock
count	The number of tables to lock
flags	Lock flags

Returns: 0 if all the check passed, non zero if a check failed.

◆ lock_tablespace_names()

bool lock_tablespace_names	(	THD *	thd,
		Tablespace_hash_set *	tablespace_set,
		ulong	lock_wait_timeout,
		MEM_ROOT *	mem_root
	)

Acquire IX MDL lock each tablespace name from the given set.

Parameters

thd	- Thread invoking this function.
tablespace_set	- Set of tablespace names to be lock.
lock_wait_timeout	- Lock timeout.
mem_root	- Memory root on which MDL_request objects can be allocated.

Returns: true - On failure; false - On Success.

◆ make_global_read_lock_block_commit()

bool Global_read_lock::make_global_read_lock_block_commit ( THD * thd )

Make global read lock also block commits.

The scenario is:

This thread has the global read lock.
Global read lock blocking of commits is not set.

See also "Handling of global read locks" above.

Parameters

thd	Reference to thread.

Return values

False	Success, global read lock set, commits are blocked.
True	Failure, thread was killed.

◆ mysql_lock_abort_for_thread()

void mysql_lock_abort_for_thread	(	THD *	thd,
		TABLE *	table
	)

Abort one thread / table combination.

Parameters

thd	Thread handler
table	Table that should be removed from lock queue

◆ mysql_lock_merge()

MYSQL_LOCK * mysql_lock_merge	(	MYSQL_LOCK *	a,
		MYSQL_LOCK *	b
	)

◆ mysql_lock_remove()

void mysql_lock_remove	(	THD *	thd,
		MYSQL_LOCK *	locked,
		TABLE *	table
	)

Try to find the table in the list of locked tables.

In case of success, unlock the table and remove it from this list. If a table has more than one lock instance, removes them all.

Parameters

thd	thread context
locked	list of locked tables
table	the table to unlock

◆ mysql_lock_tables()

MYSQL_LOCK * mysql_lock_tables	(	THD *	thd,
		TABLE **	tables,
		size_t	count,
		uint	flags
	)

Lock tables.

Parameters

thd	The current thread.
tables	An array of pointers to the tables to lock.
count	The number of tables to lock.
flags	Options: MYSQL_LOCK_IGNORE_GLOBAL_READ_ONLY Ignore SET GLOBAL READ_ONLY MYSQL_LOCK_IGNORE_TIMEOUT Use maximum timeout value.

Return values

A	lock structure pointer on success.
NULL	if an error or if wait on a lock was killed.

◆ mysql_unlock_read_tables()

void mysql_unlock_read_tables	(	THD *	thd,
		MYSQL_LOCK *	sql_lock
	)

unlock all tables locked for read.

◆ mysql_unlock_some_tables()

void mysql_unlock_some_tables	(	THD *	thd,
		TABLE **	table,
		uint	count
	)

Unlock some of the tables locked by mysql_lock_tables.

This will work even if get_lock_data fails (next unlock will free all)

◆ mysql_unlock_tables()

void mysql_unlock_tables	(	THD *	thd,
		MYSQL_LOCK *	sql_lock
	)

◆ print_lock_error()

static void print_lock_error	(	int	error,
		const char *	table
	)

static

◆ reset_lock_data()

static void reset_lock_data ( MYSQL_LOCK * sql_lock )

static

Reset lock type in lock data.

Parameters

sql_lock Lock structures to reset.

Note

After a locking error we want to quit the locking of the table(s). The test case in the bug report for Bug #18544 has the following cases: 1. Locking error in lock_external() due to InnoDB timeout.

Locking error in get_lock_data() due to missing write permission.
Locking error in wait_if_global_read_lock() due to lock conflict.

In all these cases we have already set the lock type into the lock data of the open table(s). If the table(s) are in the open table cache, they could be reused with the non-zero lock type set. This could lead to ignoring a different lock type with the next lock.

Clear the lock type of all lock data. This ensures that the next lock request will set its lock type properly.

◆ reset_lock_data_and_free()

static void reset_lock_data_and_free ( MYSQL_LOCK ** mysql_lock )

static

Reset lock type in lock data and free.

Parameters

mysql_lock Lock structures to reset.

◆ set_explicit_lock_duration()

void Global_read_lock::set_explicit_lock_duration ( THD * thd )

Set explicit duration for metadata locks which are used to implement GRL.

Parameters

thd	Reference to thread.

◆ track_table_access()

static void track_table_access	(	THD *	thd,
		TABLE **	tables,
		size_t	count
	)

static

Scan array of tables for access types; update transaction tracker accordingly.

Parameters

thd	The current thread.
tables	An array of pointers to the tables to lock.
count	The number of tables to lock.

◆ unlock_external()

static int unlock_external	(	THD *	thd,
		TABLE **	table,
		uint	count
	)

static

Unlock a set of external.

◆ unlock_global_read_lock()

void Global_read_lock::unlock_global_read_lock ( THD * thd )

Unlock global read lock.

Commits may or may not be blocked when this function is called.

See also "Handling of global read locks" above.

Parameters

thd	Reference to thread.

Variable Documentation

◆ m_atomic_active_requests

std::atomic< int32 > Global_read_lock::m_atomic_active_requests

staticprivate

◆ thr_lock_errno_to_mysql

int thr_lock_errno_to_mysql[]

static

Initial value:

= {0, ER_LOCK_ABORTED,

ER_LOCK_WAIT_TIMEOUT, ER_LOCK_DEADLOCK}

Macros

Functions

Variables

Detailed Description

Macro Definition Documentation

◆ GET_LOCK_STORE_LOCKS

◆ GET_LOCK_UNLOCK

Function Documentation

◆ acquire_shared_global_read_lock()

◆ get_lock_data()

◆ lock_external()

◆ lock_global_read_lock()

◆ lock_object_name()

◆ lock_schema_name()

◆ lock_tables_check()

◆ lock_tablespace_names()

◆ make_global_read_lock_block_commit()

◆ mysql_lock_abort_for_thread()

◆ mysql_lock_merge()

◆ mysql_lock_remove()

◆ mysql_lock_tables()

◆ mysql_unlock_read_tables()

◆ mysql_unlock_some_tables()

◆ mysql_unlock_tables()

◆ print_lock_error()

◆ reset_lock_data()

◆ reset_lock_data_and_free()

◆ set_explicit_lock_duration()

◆ track_table_access()

◆ unlock_external()

◆ unlock_global_read_lock()

Variable Documentation

◆ m_atomic_active_requests

◆ thr_lock_errno_to_mysql