Data Structures | Macros | Functions | Variables
timers.c File Reference
#include "orconfig.h"
#include "lib/evloop/compat_libevent.h"
#include "lib/evloop/timers.h"
#include "lib/intmath/muldiv.h"
#include "lib/log/log.h"
#include "lib/log/util_bug.h"
#include "lib/malloc/malloc.h"
#include "lib/time/compat_time.h"
#include "ext/timeouts/timeout.c"

Go to the source code of this file.

Data Structures

struct  timeout_cb


#define TIMEOUT_PUBLIC   static
#define WHEEL_NUM   5
#define USEC_PER_TICK   100
#define USEC_PER_SEC   1000000
#define MIN_CHECK_SECONDS   3600
#define MIN_CHECK_TICKS   (((timeout_t)MIN_CHECK_SECONDS) * (1000000 / USEC_PER_TICK))


static timeout_t tv_to_timeout (const struct timeval *tv)
static void timeout_to_tv (timeout_t t, struct timeval *tv_out)
static void timer_advance_to_cur_time (const monotime_t *now)
static void libevent_timer_reschedule (void)
STATIC void timers_run_pending (void)
static void libevent_timer_callback (mainloop_event_t *ev, void *arg)
void timers_initialize (void)
void timers_shutdown (void)
tor_timer_t * timer_new (timer_cb_fn_t cb, void *arg)
void timer_free_ (tor_timer_t *t)
void timer_set_cb (tor_timer_t *t, timer_cb_fn_t cb, void *arg)
void timer_get_cb (const tor_timer_t *t, timer_cb_fn_t *cb_out, void **arg_out)
void timer_schedule (tor_timer_t *t, const struct timeval *tv)
void timer_disable (tor_timer_t *t)


static struct timeouts * global_timeouts = NULL
static struct mainloop_event_tglobal_timer_event = NULL
static monotime_t start_of_time

Detailed Description

Wrapper around William Ahern's fast hierarchical timer wheel implementation, to tie it in with a libevent backend.

Only use these functions from the main thread.

The main advantage of tor_timer_t over using libevent's timers is that they're way more efficient if we need to have thousands or millions of them. For more information, see

Periodic timers are available in the backend, but I've turned them off. We can turn them back on if needed.

Definition in file timers.c.

Macro Definition Documentation


#define MIN_CHECK_SECONDS   3600

Check at least once every N seconds.

Definition at line 105 of file timers.c.


#define MIN_CHECK_TICKS   (((timeout_t)MIN_CHECK_SECONDS) * (1000000 / USEC_PER_TICK))

Check at least once every N ticks.

Definition at line 108 of file timers.c.


#define USEC_PER_SEC   1000000

One million microseconds in a second

Definition at line 102 of file timers.c.

Referenced by timeout_to_tv(), and tv_to_timeout().


#define USEC_PER_TICK   100

We need to choose this value carefully. Because we're using timer wheels, it actually costs us to have extra resolution we don't use. So for now, I'm going to define our resolution as .1 msec, and hope that's good enough.

Note that two of the most popular libevent backends (epoll without timerfd, and windows select), simply can't support sub-millisecond resolution, do this is optimistic for a lot of users.

Definition at line 99 of file timers.c.

Referenced by timeout_to_tv(), and tv_to_timeout().

Function Documentation

◆ libevent_timer_callback()

static void libevent_timer_callback ( mainloop_event_t ev,
void *  arg 

Invoked when the libevent timer has expired: see which tor_timer_t events have fired, activate their callbacks, and reschedule the libevent timer.

Definition at line 188 of file timers.c.

References libevent_timer_reschedule(), and timers_run_pending().

◆ libevent_timer_reschedule()

static void libevent_timer_reschedule ( void  )

Adjust the time at which the libevent timer should fire based on the next-expiring time in global_timeouts

Definition at line 153 of file timers.c.

References monotime_get(), and timer_advance_to_cur_time().

Referenced by libevent_timer_callback().

◆ timeout_to_tv()

static void timeout_to_tv ( timeout_t  t,
struct timeval tv_out 

Convert the timeout in t to a timeval in tv_out. Only use this for delays, not absolute times.

Definition at line 130 of file timers.c.


◆ timer_advance_to_cur_time()

static void timer_advance_to_cur_time ( const monotime_t now)

Update the timer tv to the current time in tv.

Definition at line 141 of file timers.c.

Referenced by libevent_timer_reschedule(), timer_schedule(), and timers_run_pending().

◆ timer_disable()

void timer_disable ( tor_timer_t *  t)

Cancel the timer t if it is currently scheduled. (It's okay to call this on an unscheduled timer.

Definition at line 324 of file timers.c.

◆ timer_free_()

void timer_free_ ( tor_timer_t *  t)

Release all storage held by t, and unschedule it if was already scheduled.

Definition at line 261 of file timers.c.

◆ timer_get_cb()

void timer_get_cb ( const tor_timer_t *  t,
timer_cb_fn_t *  cb_out,
void **  arg_out 

Set *cb_out (if provided) to this timer's callback function, and *arg_out (if provided) to this timer's callback argument.

Definition at line 285 of file timers.c.

◆ timer_new()

tor_timer_t* timer_new ( timer_cb_fn_t  cb,
void *  arg 

Allocate and return a new timer, with given callback and argument.

Definition at line 248 of file timers.c.

◆ timer_schedule()

void timer_schedule ( tor_timer_t *  t,
const struct timeval tv 

Schedule the timer t to fire at the current time plus a delay of delay microseconds. All times are relative to monotime_get().

Definition at line 299 of file timers.c.

References monotime_get(), timer_advance_to_cur_time(), and tv_to_timeout().

◆ timer_set_cb()

void timer_set_cb ( tor_timer_t *  t,
timer_cb_fn_t  cb,
void *  arg 

Change the callback and argument associated with a timer t.

Definition at line 274 of file timers.c.

◆ timers_initialize()

void timers_initialize ( void  )

Initialize the timers subsystem. Requires that libevent has already been initialized.

Definition at line 203 of file timers.c.

◆ timers_run_pending()

STATIC void timers_run_pending ( void  )

Run the callback of every timer that has expired, based on the current output of monotime_get().

Definition at line 171 of file timers.c.

References monotime_get(), and timer_advance_to_cur_time().

Referenced by libevent_timer_callback().

◆ timers_shutdown()

void timers_shutdown ( void  )

Release all storage held in the timers subsystem. Does not fire timers.

Definition at line 232 of file timers.c.

◆ tv_to_timeout()

static timeout_t tv_to_timeout ( const struct timeval tv)

Convert the timeval in tv to a timeout_t, and return it.

The output resolution is set by USEC_PER_TICK. Only use this to convert delays to number of ticks; the time represented by 0 is undefined.

Definition at line 118 of file timers.c.


Referenced by timer_schedule().