An interface to separate the MDL module from the THD, and the rest of the server code. More...

#include <mdl.h>

Inheritance diagram for MDL_context_owner:

Public Member Functions
virtual	~MDL_context_owner ()=default

virtual void	enter_cond (mysql_cond_t cond, mysql_mutex_t mutex, const PSI_stage_info stage, PSI_stage_info old_stage, const char src_function, const char src_file, int src_line)=0
	Enter a condition wait. More...

virtual void	exit_cond (const PSI_stage_info stage, const char src_function, const char *src_file, int src_line)=0
	End a wait on a condition. More...

virtual int	is_killed () const =0
	Has the owner thread been killed? More...

virtual bool	is_connected (bool=false)=0
	Does the owner still have connection to the client? More...

virtual bool	might_have_commit_order_waiters () const =0
	Indicates that owner thread might have some commit order (non-MDL) waits for it which are still taken into account by MDL deadlock detection, even in cases when it doesn't have any MDL locks acquired and therefore can't have any MDL waiters. More...

virtual THD *	get_thd ()=0
	Within MDL subsystem this one is only used for DEBUG_SYNC. More...

virtual void	notify_shared_lock (MDL_context_owner *in_use, bool needs_thr_lock_abort)=0

virtual bool	notify_hton_pre_acquire_exclusive (const MDL_key mdl_key, bool victimized)=0
	Notify/get permission from interested storage engines before acquiring exclusive lock for the key. More...

virtual void	notify_hton_post_release_exclusive (const MDL_key *mdl_key)=0
	Notify interested storage engines that we have just released exclusive lock for the key. More...

virtual uint	get_rand_seed () const =0
	Get random seed specific to this THD to be used for initialization of PRNG for the MDL_context. More...

Detailed Description

An interface to separate the MDL module from the THD, and the rest of the server code.

Constructor & Destructor Documentation

◆ ~MDL_context_owner()

virtual MDL_context_owner::~MDL_context_owner ( )

virtualdefault

Member Function Documentation

◆ enter_cond()

virtual void MDL_context_owner::enter_cond	(	mysql_cond_t *	cond,
		mysql_mutex_t *	mutex,
		const PSI_stage_info *	stage,
		PSI_stage_info *	old_stage,
		const char *	src_function,
		const char *	src_file,
		int	src_line
	)

pure virtual

Enter a condition wait.

For enter_cond() / exit_cond() to work the mutex must be held before enter_cond(); this mutex must then be released before exit_cond(). Usage must be: lock mutex; enter_cond(); your code; unlock mutex; exit_cond().

Parameters

	cond	the condition to wait on
	mutex	the associated mutex
[in]	stage	the stage to enter, or NULL
[out]	old_stage	the previous stage, or NULL
	src_function	function name of the caller
	src_file	file name of the caller
	src_line	line number of the caller

See also: ENTER_COND(), THD::enter_cond(); EXIT_COND(), THD::exit_cond()

Implemented in MDL_context_backup_manager::MDL_context_backup, and THD.

◆ exit_cond()

virtual void MDL_context_owner::exit_cond	(	const PSI_stage_info *	stage,
		const char *	src_function,
		const char *	src_file,
		int	src_line
	)

pure virtual

End a wait on a condition.

Parameters

[in]	stage	the new stage to enter
	src_function	function name of the caller
	src_file	file name of the caller
	src_line	line number of the caller

See also: ENTER_COND(), THD::enter_cond(); EXIT_COND(), THD::exit_cond()

Implemented in MDL_context_backup_manager::MDL_context_backup, and THD.

◆ get_rand_seed()

virtual uint MDL_context_owner::get_rand_seed ( ) const

pure virtual

Get random seed specific to this THD to be used for initialization of PRNG for the MDL_context.

Implemented in MDL_context_backup_manager::MDL_context_backup, and THD.

◆ get_thd()

virtual THD * MDL_context_owner::get_thd ( )

pure virtual

Within MDL subsystem this one is only used for DEBUG_SYNC.

Do not use it to peek/poke into other parts of THD from MDL. However it is OK to use this method in callbacks provided by SQL-layer to MDL subsystem (since SQL-layer has full access to THD anyway).

Warning: For some derived classes implementation of this method can return nullptr. Calling side must be ready to handle this case.

Implemented in MDL_context_backup_manager::MDL_context_backup, and THD.

◆ is_connected()

virtual bool MDL_context_owner::is_connected ( bool = false )

pure virtual

Does the owner still have connection to the client?

Implemented in THD, and MDL_context_backup_manager::MDL_context_backup.

◆ is_killed()

virtual int MDL_context_owner::is_killed ( ) const

pure virtual

Has the owner thread been killed?

Implemented in THD, and MDL_context_backup_manager::MDL_context_backup.

◆ might_have_commit_order_waiters()

virtual bool MDL_context_owner::might_have_commit_order_waiters ( ) const

pure virtual

Indicates that owner thread might have some commit order (non-MDL) waits for it which are still taken into account by MDL deadlock detection, even in cases when it doesn't have any MDL locks acquired and therefore can't have any MDL waiters.

Note: It is important for this check to be non-racy and quick (perhaps at expense of being pretty pessimistic), so it can be used to make decisions reliably about whether we can skip deadlock detection in some cases.

Implemented in MDL_context_backup_manager::MDL_context_backup, and THD.

◆ notify_hton_post_release_exclusive()

virtual void MDL_context_owner::notify_hton_post_release_exclusive ( const MDL_key * mdl_key )

pure virtual

Notify interested storage engines that we have just released exclusive lock for the key.

Implemented in MDL_context_backup_manager::MDL_context_backup, and THD.

◆ notify_hton_pre_acquire_exclusive()

virtual bool MDL_context_owner::notify_hton_pre_acquire_exclusive	(	const MDL_key *	mdl_key,
		bool *	victimized
	)

pure virtual

Notify/get permission from interested storage engines before acquiring exclusive lock for the key.

The returned argument 'victimized' specify reason for lock not granted. If 'true', lock was refused in an attempt to resolve a possible MDL->GSL deadlock. Locking may then be retried.

Returns: False if notification was successful and it is OK to acquire lock, True if one of SEs asks to abort lock acquisition.

Implemented in MDL_context_backup_manager::MDL_context_backup, and THD.

◆ notify_shared_lock()

virtual void MDL_context_owner::notify_shared_lock	(	MDL_context_owner *	in_use,
		bool	needs_thr_lock_abort
	)

pure virtual

See also: THD::notify_shared_lock()

Implemented in MDL_context_backup_manager::MDL_context_backup, and THD.

The documentation for this class was generated from the following file:

sql/mdl.h

Public Member Functions

Detailed Description

Constructor & Destructor Documentation

◆ ~MDL_context_owner()

Member Function Documentation

◆ enter_cond()

◆ exit_cond()

◆ get_rand_seed()

◆ get_thd()

◆ is_connected()

◆ is_killed()

◆ might_have_commit_order_waiters()

◆ notify_hton_post_release_exclusive()

◆ notify_hton_pre_acquire_exclusive()

◆ notify_shared_lock()