Timers

Kernel internals providing services of delayed and periodic execution. More...

Data Structures
struct	TimerEntry_t
	Description of one sleep request. More...
struct	TimerQueueEntry_t
	Entry for sorting sleep requests. More...

Macros
#define	SLEEPER_KEY_TYPE_SHIFT   24
#define	SLEEPER_KEY(_type, _thread)   (((_type) << SLEEPER_KEY_TYPE_SHIFT) | (_thread))
#define	TIMER_INVALID_ID   0xFF

Enumerations
enum	eSleepType { TIMER_SLEEP = 0 , TIMER_TIMEOUT , TIMER_PERIODIC , TIMER_INTERVAL = TIMER_PERIODIC }

Functions
static bool	is_periodic (struct TimerEntry_t *entry)
	Determine if interval in sleep entry is periodic or not.
int	os_find_timer_slot (Thread_t owner, enum eSleepType type)
int	os_find_timer_queue (int timer_slot_id)
void	os_dequeue_timed_event (unsigned queue_offs)
void	os_enqueue_timed_event (unsigned sleeper_id, uint32_t next_resume)
static int	do_set_timed_event (Txn_t txn, const unsigned slot, const unsigned interval, const enum eSleepType type)
	Perform heavy lifting of setting timers This routine will store timed event into list of timed events.
int	os_set_timed_event (unsigned microseconds, enum eSleepType type)
	Find a slot for timed event and store it.
int	os_find_timer (Thread_t owner, enum eSleepType type)
	Find a timer slot matching owner thread and timer type.
int	os_cancel_timed_event (Thread_t owner, enum eSleepType type)
	Cancels existing timed event.
int	os_cancel_sleeper (unsigned sleeper_queue_id)
	Cancel existing sleeper.
static void	delay_us (uint32_t period_us)
	Perform short busy wait.
int	os_usleep (unsigned microseconds)
	Kernel implementation of usleep() syscall.
int	os_setitimer (unsigned microseconds)
	Kernel implementation of setitimer() syscall.
void	os_timer_init (void)
	This routine initializes kernel scheduling subsystem.
bool	os_schedule_timer (unsigned *delay)
	Provide information on next scheduled event.
void	os_sleeper_reschedule (unsigned sleeper_queue_id)
void	os_run_timer (uint32_t start_microtime, uint32_t interval)
	Fire scheduled events.
uint32_t	os_cpu_freq_get (void)
	Get current CPU frequency.

Variables
struct TimerEntry_t	sleepers [SLEEPERS_MAX]
	List of all delays requested from kernel.
struct TimerQueueEntry_t	sleeper_queue [SLEEPERS_MAX]
unsigned	sleeper_queue_size
unsigned	sleeper_queue_cursor

Detailed Description

Kernel internals providing services of delayed and periodic execution.

Macro Definition Documentation

SLEEPER_KEY

#define SLEEPER_KEY	(		_type,
			_thread
	)		(((_type) << SLEEPER_KEY_TYPE_SHIFT) | (_thread))

SLEEPER_KEY_TYPE_SHIFT

#define SLEEPER_KEY_TYPE_SHIFT   24

TIMER_INVALID_ID

#define TIMER_INVALID_ID   0xFF

Enumeration Type Documentation

eSleepType

enum eSleepType

Enumerator
TIMER_SLEEP
TIMER_TIMEOUT
TIMER_PERIODIC
TIMER_INTERVAL

Function Documentation

delay_us()

static void delay_us ( uint32_t  period_us )

static

Perform short busy wait.

This will perform busywait in the context of current thread. Useful to do short waits for I/O.

Parameters

period_us

how long the wait should take

do_set_timed_event()

static int do_set_timed_event ( Txn_t  txn, const unsigned  slot, const unsigned  interval, const enum eSleepType  type  )

static

Perform heavy lifting of setting timers This routine will store timed event into list of timed events.

If event is not periodic, it will also stop thread (os_usleep semantics).

Parameters

txn	transaction used to modify the table
slot	number of slot in sleepers list
interval	amount of us for which thread should sleep
type	type of timer to set up

Returns

0 if timer was set up properly

is_periodic()

static bool is_periodic ( struct TimerEntry_t *  entry )

static

Determine if interval in sleep entry is periodic or not.

Returns

1 if interval is periodic, 0 if interval is one-shot.

os_cancel_sleeper()

int os_cancel_sleeper

(

unsigned

sleeper_queue_id

)

Cancel existing sleeper.

This function will cancel existing sleeper. It is useful for cases where you already know the identity of the sleeper in advance.

Parameters

sleeper_queue_id

ID of the item in sorted key array

Returns

0 is operation performed successfully

os_cancel_timed_event()

int os_cancel_timed_event	(	Thread_t	owner,
		enum eSleepType	type
	)

Cancels existing timed event.

This function is only accessible for periodic timers externally. It allows cancelling of interval timers set previously.

Parameters

owner	thread which shall own the interval timer
type	type of the event to be cancelled

Returns

0 if operation performed successfully.

os_cpu_freq_get()

uint32_t os_cpu_freq_get

(

void

)

Get current CPU frequency.

Will return the current CPU frequency (if known and/or available).

Returns

CPU frequency in Hz, 0 if value is not known.

os_dequeue_timed_event()

void os_dequeue_timed_event

(

unsigned

queue_offs

)

os_enqueue_timed_event()

void os_enqueue_timed_event	(	unsigned	sleeper_id,
		uint32_t	next_resume
	)

os_find_timer()

int os_find_timer	(	Thread_t	owner,
		enum eSleepType	type
	)

Find a timer slot matching owner thread and timer type.

This will find a slot which bears the timer of given type for given thread.

Parameters

[in]	owner	thread ID which should own the timer
[in]	type	type of the timer.

Returns

offset of entry in timer queue or TIMER_INVALID_ID if no such timer was found.

os_find_timer_queue()

int os_find_timer_queue

(

int

timer_slot_id

)

os_find_timer_slot()

int os_find_timer_slot	(	Thread_t	owner,
		enum eSleepType	type
	)

os_run_timer()

void os_run_timer	(	uint32_t	start_microtime,
		uint32_t	interval
	)

Fire scheduled events.

Will find and run all scheduled events in given time interval.

Parameters

microtime	starting processor time in microseconds of interval to run
interval	lenght of the interval events should be fired

os_schedule_timer()

bool os_schedule_timer

(

unsigned *

delay

)

Provide information on next scheduled event.

This function informs caller about delay until next scheduled event. Next scheduled event may be either wake-up of sleeped thread, or interval timer.

Parameters

[out]

delay

address of buffer, where delay to next scheduled event will be written

Returns

true if there is any scheduled event known and at address pointed to by delay value was written. Returns false if there is no known scheduled event. In such case content of memory pointed to by delay is undefined.

os_set_timed_event()

int os_set_timed_event	(	unsigned	microseconds,
		enum eSleepType	type
	)

Find a slot for timed event and store it.

This is actual execution core for both os_usleep and os_setitimer functions. It will find free slot or slot already occupied by calling thread and will set / update timeout values.

Parameters

microseconds	time for which thread should sleep / wait for event
type	type of timed event to set up

Returns

error status. 0 means no error.

os_setitimer()

int os_setitimer

(

unsigned

microseconds

)

Kernel implementation of setitimer() syscall.

See setitimer for details on arguments.

os_sleeper_reschedule()

void os_sleeper_reschedule

(

unsigned

sleeper_queue_id

)

os_timer_init()

void os_timer_init

(

void

)

This routine initializes kernel scheduling subsystem.

It is necessary to call this routine before first call to either timer syscalls, or os_run_timer otherwise things will go wrong.

os_usleep()

int os_usleep

(

unsigned

microseconds

)

Kernel implementation of usleep() syscall.

See usleep for details on arguments.

Variable Documentation

sleeper_queue

struct TimerQueueEntry_t sleeper_queue[SLEEPERS_MAX]

sleeper_queue_cursor

unsigned sleeper_queue_cursor

sleeper_queue_size

unsigned sleeper_queue_size

sleepers

struct TimerEntry_t sleepers[SLEEPERS_MAX]

List of all delays requested from kernel.

This structure contains all scheduled sleeps requested by all threads. Every thread can technically request one periodic timer and one one-shot delay.