mdl.cc File Reference

#include "sql/mdl.h"
#include <time.h>
#include <algorithm>
#include <atomic>
#include <functional>
#include "lf.h"
#include "my_dbug.h"
#include "my_macros.h"
#include "my_murmur3.h"
#include "my_sharedlib.h"
#include "my_sys.h"
#include "my_systime.h"
#include "my_thread.h"
#include "mysql/components/services/bits/psi_bits.h"
#include "mysql/components/services/bits/psi_cond_bits.h"
#include "mysql/components/services/bits/psi_memory_bits.h"
#include "mysql/components/services/bits/psi_mutex_bits.h"
#include "mysql/components/services/bits/psi_rwlock_bits.h"
#include "mysql/psi/mysql_cond.h"
#include "mysql/psi/mysql_mdl.h"
#include "mysql/psi/mysql_memory.h"
#include "mysql/psi/mysql_mutex.h"
#include "mysql/psi/mysql_stage.h"
#include "mysql/psi/psi_mdl.h"
#include "mysql/service_thd_wait.h"
#include "mysql/strings/m_ctype.h"
#include "mysqld_error.h"
#include "prealloced_array.h"
#include "sql/debug_sync.h"
#include "sql/thr_malloc.h"

Classes
class	MDL_map
	A collection of all MDL locks. More...
class	Deadlock_detection_visitor
	A context of the recursive traversal through all contexts in all sessions in search for deadlock. More...
class	MDL_lock
	The lock context. More...
class	MDL_lock::Ticket_list
struct	MDL_lock::MDL_lock_strategy
	Helper struct which defines how different types of locks are handled for a specific MDL_lock. More...
class	MDL_request_cmp

Macros
#define	MDL_BIT(A)   static_cast<MDL_lock::bitmap_t>(1U << A)
	Get a bit corresponding to enum_mdl_type value in a granted/waiting bitmaps and compatibility matrices. More...

Functions
static void	init_mdl_psi_keys (void)
	Initialise all the performance schema instrumentation points used by the MDL subsystem. More...
static const uchar *	mdl_locks_key (const uchar *record, size_t *length)
void	mdl_init ()
	Initialize the metadata locking subsystem. More...
void	mdl_destroy ()
	Release resources of metadata locking subsystem. More...
int32	mdl_get_unused_locks_count ()
	Get number of unused MDL_lock objects in MDL_map cache. More...
static void	mdl_lock_cons (uchar *arg)
static void	mdl_lock_dtor (uchar *arg)
static void	mdl_lock_reinit (uchar *dst_arg, const uchar *src_arg)
static uint	murmur3_adapter (const LF_HASH *, const uchar *key, size_t length)
	Adapter function which allows to use murmur3 with LF_HASH implementation. More...
static int	mdl_lock_match_unused (const uchar *arg, void *match_arg)
	Helper function which allows to check if MDL_lock object stored in LF_HASH is unused - i.e. More...
bool	equivalent (const MDL_ticket *a, const MDL_ticket *b, enum_mdl_duration target_duration)

Variables
MYSQL_PLUGIN_IMPORT CHARSET_INFO *	system_charset_info
static PSI_memory_key	key_memory_MDL_context_acquire_locks
static PSI_mutex_key	key_MDL_wait_LOCK_wait_status
static PSI_mutex_info	all_mdl_mutexes []
static PSI_rwlock_key	key_MDL_lock_rwlock
static PSI_rwlock_key	key_MDL_context_LOCK_waiting_for
static PSI_rwlock_info	all_mdl_rwlocks []
static PSI_cond_key	key_MDL_wait_COND_wait_status
static PSI_cond_info	all_mdl_conds []
static PSI_memory_info	all_mdl_memory []
static bool	mdl_initialized = false
int32	mdl_locks_unused_locks_low_water
	Threshold for number of unused MDL_lock objects. More...
static MDL_map	mdl_locks

Macro Definition Documentation

MDL_BIT

#define MDL_BIT

(

A

)

static_cast<MDL_lock::bitmap_t>(1U << A)

Get a bit corresponding to enum_mdl_type value in a granted/waiting bitmaps and compatibility matrices.

Function Documentation

equivalent()

bool equivalent	(	const MDL_ticket *	a,
		const MDL_ticket *	b,
		enum_mdl_duration	target_duration
	)

init_mdl_psi_keys()

static void init_mdl_psi_keys ( void  )

static

Initialise all the performance schema instrumentation points used by the MDL subsystem.

mdl_destroy()

void mdl_destroy

(

)

Release resources of metadata locking subsystem.

Destroys the global mutex and the condition variable. Called at server shutdown.

mdl_get_unused_locks_count()

int32 mdl_get_unused_locks_count

(

)

Get number of unused MDL_lock objects in MDL_map cache.

Mostly needed for unit-testing.

mdl_init()

void mdl_init

(

)

Initialize the metadata locking subsystem.

This function is called at server startup.

In particular, initializes the new global mutex and the associated condition variable: LOCK_mdl and COND_mdl. These locking primitives are implementation details of the MDL subsystem and are private to it.

mdl_lock_cons()

static void mdl_lock_cons ( uchar *  arg )

static

mdl_lock_dtor()

static void mdl_lock_dtor ( uchar *  arg )

static

mdl_lock_match_unused()

static int mdl_lock_match_unused ( const uchar *  arg, void *  match_arg  )

static

Helper function which allows to check if MDL_lock object stored in LF_HASH is unused - i.e.

doesn't have any locks on both "fast" and "slow" paths and is not marked as deleted.

mdl_lock_reinit()

static void mdl_lock_reinit ( uchar *  dst_arg, const uchar *  src_arg  )

static

mdl_locks_key()

static const uchar * mdl_locks_key ( const uchar *  record, size_t *  length  )

static

murmur3_adapter()

static uint murmur3_adapter ( const LF_HASH *  , const uchar *  key, size_t  length  )

static

Adapter function which allows to use murmur3 with LF_HASH implementation.

Variable Documentation

all_mdl_conds

PSI_cond_info all_mdl_conds[]

static

Initial value:

= {{&key_MDL_wait_COND_wait_status,
                                         "MDL_context::COND_wait_status", 0, 0,
                                         PSI_DOCUMENT_ME}}

all_mdl_memory

PSI_memory_info all_mdl_memory[]

static

Initial value:

= {
    {&key_memory_MDL_context_acquire_locks, "MDL_context::acquire_locks", 0, 0,
     "Buffer for sorting lock requests."}}

all_mdl_mutexes

PSI_mutex_info all_mdl_mutexes[]

static

Initial value:

= {{&key_MDL_wait_LOCK_wait_status,
                                            "MDL_wait::LOCK_wait_status", 0, 0,
                                            PSI_DOCUMENT_ME}}

all_mdl_rwlocks

PSI_rwlock_info all_mdl_rwlocks[]

static

Initial value:

= {
    {&key_MDL_lock_rwlock, "MDL_lock::rwlock", PSI_FLAG_RWLOCK_PR, 0,
     PSI_DOCUMENT_ME},
    {&key_MDL_context_LOCK_waiting_for, "MDL_context::LOCK_waiting_for",
     PSI_FLAG_RWLOCK_PR, 0, PSI_DOCUMENT_ME}}

key_MDL_context_LOCK_waiting_for

PSI_rwlock_key key_MDL_context_LOCK_waiting_for

static

key_MDL_lock_rwlock

PSI_rwlock_key key_MDL_lock_rwlock

static

key_MDL_wait_COND_wait_status

PSI_cond_key key_MDL_wait_COND_wait_status

static

key_MDL_wait_LOCK_wait_status

PSI_mutex_key key_MDL_wait_LOCK_wait_status

static

key_memory_MDL_context_acquire_locks

PSI_memory_key key_memory_MDL_context_acquire_locks

static

mdl_initialized

bool mdl_initialized = false

static

mdl_locks

MDL_map mdl_locks

static

mdl_locks_unused_locks_low_water

int32 mdl_locks_unused_locks_low_water

Initial value:

=
    MDL_LOCKS_UNUSED_LOCKS_LOW_WATER_DEFAULT

Threshold for number of unused MDL_lock objects.

We will start considering freeing some unused objects only after exceeding this value and if unused/total objects ratio is high enough.

Normally this threshold is constant. It is exposed outside of MDL subsystem as a variable only in order to simplify unit testing.

system_charset_info

MYSQL_PLUGIN_IMPORT CHARSET_INFO* system_charset_info

extern