lock_queue_t Class Reference

A lock queue to hold granted and waiting lock requests (lock_queue_entry_t's) for a given lock. More...

#include <lock_bucket.h>

Classes
struct	check_grant_result

Public Member Functions
	lock_queue_t (uint32_t hash)
	~lock_queue_t ()
uint32_t	hash () const
uint32_t	hit_count () const

Private Member Functions
void	increase_hit_count ()
lock_queue_t *	next ()
void	set_next (lock_queue_t *new_next)
const lsn_t &	x_lock_tag () const
void	update_x_lock_tag (const lsn_t &new_tag)
lock_queue_entry_t *	find_request (const xct_lock_info_t *li)
void	append_request (lock_queue_entry_t *myreq)
void	detach_request (lock_queue_entry_t *myreq)
bool	grant_request (lock_queue_entry_t *myreq, lsn_t &observed)
void	check_can_grant (lock_queue_entry_t *myreq, check_grant_result &result)
bool	_check_compatible (const okvl_mode &granted_mode, const okvl_mode &requested_mode, lock_queue_entry_t *other_request, bool proceeds_me, lsn_t &observed)
void	wakeup_waiters (const okvl_mode &released_requested)

Static Private Member Functions
static lock_queue_t *	allocate_lock_queue (uint32_t hash)
static void	deallocate_lock_queue (lock_queue_t *obj)

Private Attributes
const uint32_t	_hash
	precise hash for this lock queue. More...
uint32_t	_hit_counts
uint64_t	_release_version
	Monotonically increasing counter that is incremented when some xct releases some lock in this queue. More...
lock_queue_t *	_next
srwlock_t	_requests_latch
lsn_t	_x_lock_tag
lock_queue_entry_t *	_head
lock_queue_entry_t *	_tail

Friends
class	bucket_t
class	lock_core_m

Detailed Description

A lock queue to hold granted and waiting lock requests (lock_queue_entry_t's) for a given lock.

NOTE objects of this class are created via the container of this object (bucket_t) calling allocate_lock_queue / deallocate_lock_queue.

WARNING: lock_queue_t's are currently only deleted at shutdown. There is no mechanism presently to prevent one thread from deleting a lock_queue_t out from under another thread. FIXME?

Constructor & Destructor Documentation

lock_queue_t()

lock_queue_t::lock_queue_t ( uint32_t  hash )

inline

~lock_queue_t()

lock_queue_t::~lock_queue_t ( )

inline

Member Function Documentation

_check_compatible()

bool lock_queue_t::_check_compatible ( const okvl_mode &  granted_mode, const okvl_mode &  requested_mode, lock_queue_entry_t *  other_request, bool  proceeds_me, lsn_t &  observed  )

inlineprivate

allocate_lock_queue()

static lock_queue_t* lock_queue_t::allocate_lock_queue ( uint32_t  hash )

staticprivate

Allocate a new queue object. Uses TLS cache in lock_core.cpp.

append_request()

void lock_queue_t::append_request ( lock_queue_entry_t *  myreq )

private

check_can_grant()

void lock_queue_t::check_can_grant ( lock_queue_entry_t *  myreq, check_grant_result &  result  )

private

Checkif my request can be granted, and also check deadlocks.

deallocate_lock_queue()

static void lock_queue_t::deallocate_lock_queue ( lock_queue_t *  obj )

staticprivate

Deallocate a new queue object. Uses TLS cache in lock_core.cpp. Shutdown time only.

detach_request()

void lock_queue_t::detach_request ( lock_queue_entry_t *  myreq )

private

find_request()

lock_queue_entry_t* lock_queue_t::find_request ( const xct_lock_info_t *  li )

private

grant_request()

bool lock_queue_t::grant_request ( lock_queue_entry_t *  myreq, lsn_t &  observed  )

private

try getting a lock.

Returns

if it really succeeded to get the lock. Requires current thread is myreq->_thr

hash()

uint32_t lock_queue_t::hash ( ) const

inline

hit_count()

uint32_t lock_queue_t::hit_count ( ) const

inline

increase_hit_count()

void lock_queue_t::increase_hit_count ( )

inlineprivate

next()

lock_queue_t* lock_queue_t::next ( )

inlineprivate

Requires read access for the bucket containing us if any's _queue_latch.

set_next()

void lock_queue_t::set_next ( lock_queue_t *  new_next )

inlineprivate

Requires write access for the bucket containing us if any's _queue_latch.

update_x_lock_tag()

void lock_queue_t::update_x_lock_tag ( const lsn_t &  new_tag )

inlineprivate

Requires write access for _request_latch, new_tag may be lsn_t::null.

wakeup_waiters()

void lock_queue_t::wakeup_waiters ( const okvl_mode &  released_requested )

private

opportunistically wake up waiters. called when some lock is released.

x_lock_tag()

const lsn_t& lock_queue_t::x_lock_tag ( ) const

inlineprivate

Requires read access for _request_latch.

Friends And Related Function Documentation

bucket_t

friend class bucket_t

friend

lock_core_m

friend class lock_core_m

friend

Member Data Documentation

_hash

const uint32_t lock_queue_t::_hash

private

precise hash for this lock queue.

_head

lock_queue_entry_t* lock_queue_t::_head

private

The first entry in this queue or NULL if queue empty; protected by _requests_latch.

_hit_counts

uint32_t lock_queue_t::_hit_counts

private

How popular this lock is (approximately, so, no protection). Intended for background cleanup to save memory, but not currently used. Someday, the queue may be revoked in background cleanup. FIXME

NOTE this is NOT a pin-count that is precisely incremented/decremented to control when deletion could occur.

_next

lock_queue_t* lock_queue_t::_next

private

Forms a singly-linked list for other queues in the same bucket as us; protected by the bucket containing us's _queue_latch if any.

_release_version

uint64_t lock_queue_t::_release_version

private

Monotonically increasing counter that is incremented when some xct releases some lock in this queue.

This is NOT protected by latch because it is used only for quick check to opportunistically prevent false deadlock detection. This counter was previously just a true/false flag (_wait_map_obsolete flag) in waitmap, but turns out that a granular checking prevents false deadlock detections more precisely and efficiently.

_requests_latch

srwlock_t lock_queue_t::_requests_latch

private

R/W latch to protect remaining fields as well as our lock_queue_entry_t's fields.

_tail

lock_queue_entry_t* lock_queue_t::_tail

private

The last entry in this queue or NULL if queue empty; protected by _requests_latch.

_x_lock_tag

lsn_t lock_queue_t::_x_lock_tag

private

Stores the commit timestamp of the latest transaction that released an X lock on this queue; holds lsn_t::null if no such transaction exists; protected by _requests_latch.

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

• src/sm/lock_bucket.h