latch_t Class Reference

A short-term hold (exclusive or shared) on a page. More...

#include <latch.h>

Public Member Functions
	latch_t ()
	Create a latch. More...
	~latch_t ()
ostream &	print (ostream &) const
const void *	id () const
void	setname (const char *const desc)
	Change the name of the latch. More...
w_rc_t	latch_acquire (latch_mode_t m, int timeout=timeout_t::WAIT_FOREVER)
	Acquire the latch in given mode. More...
w_rc_t	upgrade_if_not_block (bool &would_block)
	Upgrade from SH to EX if it can be done w/o blocking. More...
void	downgrade ()
	Convert atomically an EX latch into an SH latch. More...
int	latch_release ()
	release the latch. More...
bool	is_latched () const
	Unreliable, but helpful for some debugging. More...
int	latch_cnt () const
	Number of acquires. A thread may hold more than once. More...
int	num_holders () const
	How many threads hold the R/W lock. More...
bool	is_mine () const
	True iff held in EX mode. More...
int	held_by_me () const
	True iff held in EX or SH mode. Actually, it returns the. More...
latch_mode_t	mode () const
	EX, SH, or NL (if not held at all). More...

Static Public Member Functions
static void	on_thread_destroy ()
	Destroy TLS structures. More...

Static Public Attributes
static const char *const	latch_mode_str [4] = {"NL", "Q", "SH", "EX"}
	string names of modes. More...

Private Member Functions
w_rc_t	_acquire (latch_mode_t m, int timeout_in_ms, latch_holder_t *me)
int	_release (latch_holder_t *me)
void	_downgrade (latch_holder_t *me)
	latch_t (const latch_t &)
latch_t &	operator= (const latch_t &)

Private Attributes
srwlock_t	_lock
uint32_t	_total_count

Detailed Description

A short-term hold (exclusive or shared) on a page.

A latch may be acquire()d multiple times by a single thread. The mode of subsequent acquire()s must be at or above the level of the currently held latch. Each of these individual locks must be released.

See also

latch_holder_t

Constructor & Destructor Documentation

latch_t() [1/2]

latch_t::latch_t

(

)

Create a latch.

~latch_t()

latch_t::~latch_t

(

)

latch_t() [2/2]

latch_t::latch_t ( const latch_t &  )

private

Member Function Documentation

_acquire()

w_rc_t latch_t::_acquire ( latch_mode_t  m, int  timeout_in_ms, latch_holder_t *  me  )

private

_downgrade()

void latch_t::_downgrade ( latch_holder_t *  me )

private

_release()

int latch_t::_release ( latch_holder_t *  me )

private

downgrade()

void latch_t::downgrade

(

)

Convert atomically an EX latch into an SH latch.

Does not decrement the latch count.

held_by_me()

int latch_t::held_by_me

(

)

const

True iff held in EX or SH mode. Actually, it returns the.

id()

const void* latch_t::id ( ) const

inline

is_latched()

bool latch_t::is_latched ( ) const

inline

Unreliable, but helpful for some debugging.

is_mine()

bool latch_t::is_mine

(

)

const

True iff held in EX mode.

latch_acquire()

w_rc_t latch_t::latch_acquire	(	latch_mode_t	m,
		int	timeout = timeout_t::WAIT_FOREVER
	)

Acquire the latch in given mode.

See also

timeout_t.

latch_cnt()

int latch_t::latch_cnt ( ) const

inline

Number of acquires. A thread may hold more than once.

latch_release()

int latch_t::latch_release

(

)

release the latch.

Decrements the latch count and releases only when it hits 0. Returns the resulting latch count.

mode()

latch_mode_t latch_t::mode ( ) const

inline

EX, SH, or NL (if not held at all).

num_holders()

int latch_t::num_holders ( ) const

inline

How many threads hold the R/W lock.

on_thread_destroy()

void latch_t::on_thread_destroy ( )

static

Destroy TLS structures.

operator=()

latch_t& latch_t::operator= ( const latch_t &  )

private

print()

std::ostream & latch_t::print

(

std::ostream &

out

)

const

setname()

void latch_t::setname ( const char *const  desc )

inline

Change the name of the latch.

upgrade_if_not_block()

w_rc_t latch_t::upgrade_if_not_block

(

bool &

would_block

)

Upgrade from SH to EX if it can be done w/o blocking.

Returns bool indicating if it would have blocked, in which case the upgrade did not occur. If it didn't have to block, the upgrade did occur.

Note

Does not increment the count.

Member Data Documentation

_lock

srwlock_t latch_t::_lock

mutableprivate

_total_count

uint32_t latch_t::_total_count

private

latch_mode_str

const char *const latch_t::latch_mode_str = {"NL", "Q", "SH", "EX"}

static

string names of modes.

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

• src/sm/latch.h
• src/sm/latch.cpp