os_event Struct Reference

InnoDB condition variable. More...

Public Member Functions
	os_event () 1
	Constructor. More...
	~os_event () 1
	Destructor. More...
void	destroy () 1
	Destroys a condition variable. More...
void	set () 1
	Set the event. More...
bool	try_set () 1
int64_t	reset () 1
void	wait_low (int64_t reset_sig_count) 1
	Waits for an event object until it is in the signaled state. More...
ulint	wait_time_low (std::chrono::microseconds timeout, int64_t reset_sig_count) 1
	Waits for an event object until it is in the signaled state or a timeout is exceeded. More...
bool	is_set () const 1

Protected Member Functions
	os_event (const os_event &)
os_event &	operator= (const os_event &)

Private Member Functions
void	init () 1
	Initialize a condition variable. More...
void	wait () 1
	Wait on condition variable. More...
void	broadcast () 1
	Wakes all threads waiting for condition variable. More...
void	signal () 1
	Wakes one thread waiting for condition variable. More...
bool	timed_wait (const timespec *abstime)
	Do a timed wait on condition variable. More...
struct timespec	get_wait_timelimit (std::chrono::microseconds timeout)
	Returns absolute time until which we should wait if we wanted to wait for timeout since now. More...

Private Attributes
bool	m_set
	this is true when the event is in the signaled state, i.e., a thread does not stop if it tries to wait for this event More...
int64_t	signal_count
	this is incremented each time the event becomes signaled More...
EventMutex	mutex
	this mutex protects the next fields More...
os_cond_t	cond_var
	condition variable is used in waiting for the event More...

Static Private Attributes
static pthread_condattr_t	cond_attr
	Attributes object passed to pthread_cond_* functions. More...
static bool	cond_attr_has_monotonic_clock {false}
	True iff usage of the monotonic clock has been successfully enabled for the cond_attr object. More...
static bool	global_initialized {false}
static std::atomic_size_t	n_objects_alive {0}

Friends
void	os_event_global_init ()
	Initializes support for os_event objects. More...
void	os_event_global_destroy ()
	Deinitializes support for os_event objects. More...

Detailed Description

InnoDB condition variable.

Constructor & Destructor Documentation

os_event() [1/2]

os_event::os_event

(

)

Constructor.

~os_event()

os_event::~os_event

(

)

Destructor.

os_event() [2/2]

os_event::os_event ( const os_event &  )

protected

Member Function Documentation

broadcast()

void os_event::broadcast ( )

inlineprivate

Wakes all threads waiting for condition variable.

destroy()

void os_event::destroy ( )

inline

Destroys a condition variable.

get_wait_timelimit()

struct timespec os_event::get_wait_timelimit ( std::chrono::microseconds  timeout )

private

Returns absolute time until which we should wait if we wanted to wait for timeout since now.

This method could be removed if we switched to the usage of std::condition_variable.

init()

void os_event::init ( void  )

inlineprivate

Initialize a condition variable.

is_set()

bool os_event::is_set ( ) const

inline

Returns

true if the event is in the signalled state.

operator=()

os_event & os_event::operator= ( const os_event &  )

protected

reset()

int64_t os_event::reset ( void  )

inline

set()

void os_event::set ( )

inline

Set the event.

signal()

void os_event::signal ( )

inlineprivate

Wakes one thread waiting for condition variable.

timed_wait()

bool os_event::timed_wait ( const timespec *  abstime )

private

Do a timed wait on condition variable.

Returns

true if timed out, false otherwise

Parameters

abstime

Timeout.

try_set()

bool os_event::try_set ( )

inline

wait()

void os_event::wait ( )

inlineprivate

Wait on condition variable.

wait_low()

void os_event::wait_low

(

int64_t

reset_sig_count

)

Waits for an event object until it is in the signaled state.

Typically, if the event has been signalled after the os_event_reset() we'll return immediately because event->m_set == true. There are, however, situations (e.g.: sync_array code) where we may lose this information. For example:

thread A calls os_event_reset() thread B calls os_event_set() [event->m_set == true] thread C calls os_event_reset() [event->m_set == false] thread A calls os_event_wait() [infinite wait!] thread C calls os_event_wait() [infinite wait!]

Where such a scenario is possible, to avoid infinite wait, the value returned by reset() should be passed in as reset_sig_count.

wait_time_low()

ulint os_event::wait_time_low	(	std::chrono::microseconds	timeout,
		int64_t	reset_sig_count
	)

Waits for an event object until it is in the signaled state or a timeout is exceeded.

Parameters

timeout	Timeout in microseconds, or std::chrono::microseconds::max()
reset_sig_count	Zero or the value returned by previous call of os_event_reset().

Returns

0 if success, OS_SYNC_TIME_EXCEEDED if timeout was exceeded

Friends And Related Function Documentation

os_event_global_destroy

void os_event_global_destroy ( void  )

friend

Deinitializes support for os_event objects.

Must be called once, and after all os_event objects are destroyed. After it is called, no new os_event is allowed to be created.

os_event_global_init

void os_event_global_init ( void  )

friend

Initializes support for os_event objects.

Must be called once, and before any os_event object is created.

Member Data Documentation

cond_attr

pthread_condattr_t os_event::cond_attr

staticprivate

Attributes object passed to pthread_cond_* functions.

Defines usage of the monotonic clock if it's available. Initialized once, in the os_event::global_init(), and destroyed in the os_event::global_destroy().

cond_attr_has_monotonic_clock

bool os_event::cond_attr_has_monotonic_clock {false}

staticprivate

True iff usage of the monotonic clock has been successfully enabled for the cond_attr object.

cond_var

os_cond_t os_event::cond_var

private

condition variable is used in waiting for the event

global_initialized

bool os_event::global_initialized {false}

staticprivate

m_set

bool os_event::m_set

private

this is true when the event is in the signaled state, i.e., a thread does not stop if it tries to wait for this event

mutex

EventMutex os_event::mutex

private

this mutex protects the next fields

n_objects_alive

std::atomic_size_t os_event::n_objects_alive {0}

staticprivate

signal_count

int64_t os_event::signal_count

private

this is incremented each time the event becomes signaled

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

• storage/innobase/os/os0event.cc