os0event.cc File Reference

The interface to the operating system condition variables. More...

#include "os0event.h"
#include <errno.h>
#include <time.h>
#include "ha_prototypes.h"
#include "ut0mutex.h"
#include "ut0new.h"

Classes
struct	os_event
	InnoDB condition variable. More...

Typedefs
typedef pthread_cond_t	os_cond_t
	Native condition variable. More...

Functions
os_event_t	os_event_create ()
	Creates an event semaphore, i.e., a semaphore which may just have two states: signaled and nonsignaled. More...
bool	os_event_is_set (const os_event_t event)
	Check if the event is set. More...
void	os_event_set (os_event_t event)
	Sets an event semaphore to the signaled state: lets waiting threads proceed. More...
bool	os_event_try_set (os_event_t event)
int64_t	os_event_reset (os_event_t event)
	Resets an event semaphore to the nonsignaled state. More...
ulint	os_event_wait_time_low (os_event_t event, 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. More...
void	os_event_wait_low (os_event_t event, int64_t reset_sig_count)
	Waits for an event object until it is in the signaled state. More...
void	os_event_destroy (os_event_t &event)
	Frees an event object. More...
void	os_event_global_init (void)
	Initializes support for os_event objects. More...
void	os_event_global_destroy (void)
	Deinitializes support for os_event objects. More...

Variables
static const uint64_t	MICROSECS_IN_A_SECOND = 1000000
	The number of microseconds in a second. More...
static const uint64_t	NANOSECS_IN_A_SECOND
	The number of nanoseconds in a second. More...

Detailed Description

The interface to the operating system condition variables.

Created 2012-09-23 Sunny Bains

Typedef Documentation

os_cond_t

typedef pthread_cond_t os_cond_t

Native condition variable.

Function Documentation

os_event_create()

os_event_t os_event_create

(

)

Creates an event semaphore, i.e., a semaphore which may just have two states: signaled and nonsignaled.

The created event is manual reset: it must be reset explicitly by calling sync_os_reset_event.

Returns

the event handle

On SuSE Linux we get spurious EBUSY from pthread_mutex_destroy() unless we grab and release the mutex here. Current OS version: openSUSE Leap 15.0 Linux xxx 4.12.14-lp150.12.25-default #1 SMP Thu Nov 1 06:14:23 UTC 2018 (3fcf457) x86_64 x86_64 x86_64 GNU/Linux

os_event_destroy()

void os_event_destroy

(

os_event_t &

event

)

Frees an event object.

in/own: event to free

Parameters

event

in/own: event to free

os_event_global_destroy()

void os_event_global_destroy

(

void

)

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

)

Initializes support for os_event objects.

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

os_event_is_set()

bool os_event_is_set

(

const os_event_t

event

)

Check if the event is set.

Returns

true if set

Parameters

event

in: event to test

os_event_reset()

int64_t os_event_reset

(

os_event_t

event

)

Resets an event semaphore to the nonsignaled state.

Resets an event semaphore to the non-signaled state.

Waiting threads will stop to wait for the event. The return value should be passed to os_even_wait_low() if it is desired that this thread should not wait in case of an intervening call to os_event_set() between this os_event_reset() and the os_event_wait_low() call. See comments for os_event_wait_low().

Returns

current signal_count.

Parameters

event

in/out: event to reset

os_event_set()

void os_event_set

(

os_event_t

event

)

Sets an event semaphore to the signaled state: lets waiting threads proceed.

in/out: event to set

Parameters

event

in/out: event to set

os_event_try_set()

bool os_event_try_set

(

os_event_t

event

)

os_event_wait_low()

void os_event_wait_low	(	os_event_t	event,
		int64_t	reset_sig_count
	)

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

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

Parameters

event	in: event to wait
reset_sig_count	in: zero or the value returned by previous call of os_event_reset().

os_event_wait_time_low()

ulint os_event_wait_time_low	(	os_event_t	event,
		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.

In Unix the timeout is always infinite.

Parameters

[in,out]	event	Event to wait for.
[in]	timeout	Timeout, or std::chrono::microseconds::max().
[in]	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

Variable Documentation

MICROSECS_IN_A_SECOND

const uint64_t MICROSECS_IN_A_SECOND = 1000000

static

The number of microseconds in a second.

NANOSECS_IN_A_SECOND

const uint64_t NANOSECS_IN_A_SECOND

static

Initial value:

=
    1000 * MICROSECS_IN_A_SECOND

The number of nanoseconds in a second.