commit dcf948da0652ca13f5b44f0e15e062f1ff3f8993 Author: Nick Mathewson <nickm@torproject.org> Date: Wed Apr 13 11:11:35 2016 -0400 Add wrappers to tie the new timeouts into libevent. --- src/common/include.am | 2 + src/common/timers.c | 276 ++++++++++++++++++++++++++++++++++++++++++++++++++ src/common/timers.h | 22 ++++ src/ext/include.am | 12 +-- 4 files changed, 306 insertions(+), 6 deletions(-) diff --git a/src/common/include.am b/src/common/include.am index e61ed68..0450268 100644 --- a/src/common/include.am +++ b/src/common/include.am @@ -97,6 +97,7 @@ LIBOR_CRYPTO_A_SOURCES = \ LIBOR_EVENT_A_SOURCES = \ src/common/compat_libevent.c \ src/common/procmon.c \ + src/common/timers.c \ src/ext/timeouts/timeout.c src_common_libor_a_SOURCES = $(LIBOR_A_SOURCES) @@ -136,6 +137,7 @@ COMMONHEADERS = \ src/common/procmon.h \ src/common/sandbox.h \ src/common/testsupport.h \ + src/common/timers.h \ src/common/torgzip.h \ src/common/torint.h \ src/common/torlog.h \ diff --git a/src/common/timers.c b/src/common/timers.c new file mode 100644 index 0000000..5f42cd4 --- /dev/null +++ b/src/common/timers.c @@ -0,0 +1,276 @@ +/* Copyright (c) 2016, The Tor Project, Inc. */ +/* See LICENSE for licensing information */ + +/** + * \file timers.c + * \brief 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 + * http://www.25thandclement.com/~william/projects/timeout.c.html + * + * Periodic timers are available in the backend, but I've turned them off. + * We can turn them back on if needed. + */ + +/* Notes: + * + * The use of tor_gettimeofday_cached_monotonic() is kind of ugly. It would + * be neat to fix it. + * + * Having a way to free all timers on shutdown would free people from the + * need to track them. Not sure if that's clever though. + * + * In an ideal world, Libevent would just switch to use this backend, and we + * could throw this file away. But even if Libevent does switch, we'll be + * stuck with legacy libevents for some time. + */ + +#include "orconfig.h" + +#include "compat.h" +#include "compat_libevent.h" +#include "timers.h" +#include "torlog.h" +#include "util.h" + +#ifdef HAVE_EVENT2_EVENT_H +#include <event2/event.h> +#else +#include <event.h> +#endif + +struct timeout_cb { + timer_cb_fn_t cb; + void *arg; +}; + +/* + * These definitions are for timeouts.c and timeouts.h. + */ +#ifdef __GNUC__ +/* We're not exposing any of the functions outside this file. */ +#define TIMEOUT_PUBLIC __attribute__((__unused__)) static +#else +/* We're not exposing any of the functions outside this file. */ +#define TIMEOUT_PUBLIC static +#endif +/* We're not using periodic events. */ +#define TIMEOUT_DISABLE_INTERVALS +/* We always know the global_timeouts object, so we don't need each timeout + * to keep a pointer to it. */ +#define TIMEOUT_DISABLE_RELATIVE_ACCESS +/* We're providing our own struct timeout_cb. */ +#define TIMEOUT_CB_OVERRIDE +/* We're going to support timers that are pretty far out in advance. Making + * this big can be inefficient, but having a significant number of timers + * above TIMEOUT_MAX can also be super-inefficent. Choosing 5 here sets + * timeout_max to 2^30 ticks, or 29 hours with our value for USEC_PER_TICK */ +#define WHEEL_NUM 5 +#include "src/ext/timeouts/timeout.c" + +static struct timeouts *global_timeouts = NULL; +static struct event *global_timer_event = NULL; + +/** 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. + */ +#define USEC_PER_TICK 100 + +/** One million microseconds in a second */ +#define USEC_PER_SEC 1000000 + +/** + * Convert the timeval in <b>tv</b> to a timeout_t, and return it. + * + * The output resolution is set by USEC_PER_TICK, and the time corresponding + * to 0 is the same as the time corresponding to 0 from + * tor_gettimeofday_cached_monotonic(). + */ +static timeout_t +tv_to_timeout(const struct timeval *tv) +{ + uint64_t usec = tv->tv_usec; + usec += ((uint64_t)USEC_PER_SEC) * tv->tv_sec; + return usec / USEC_PER_TICK; +} + +/** + * Convert the timeout in <b>t</b> to a timeval in <b>tv_out</b> + */ +static void +timeout_to_tv(timeout_t t, struct timeval *tv_out) +{ + t *= USEC_PER_TICK; + tv_out->tv_usec = (int)(t % USEC_PER_SEC); + tv_out->tv_sec = (time_t)(t / USEC_PER_SEC); +} + +/** + * Update the timer <b>tv</b> to the current time in <b>tv</b>. + */ +static void +timer_advance_to_cur_time(const struct timeval *tv) +{ + timeout_t cur_tick = tv_to_timeout(tv); + if (BUG(cur_tick < timeouts_get_curtime(global_timeouts))) { + cur_tick = timeouts_get_curtime(global_timeouts); // LCOV_EXCL_LINE + } + timeouts_update(global_timeouts, cur_tick); +} + +/** + * Adjust the time at which the libevent timer should fire based on + * the next-expiring time in <b>global_timeouts</b> + */ +static void +libevent_timer_reschedule(void) +{ + struct timeval now; + tor_gettimeofday_cached_monotonic(&now); + timer_advance_to_cur_time(&now); + + const timeout_t delay = timeouts_timeout(global_timeouts); + struct timeval d; + timeout_to_tv(delay, &d); + event_add(global_timer_event, &d); +} + +/** + * Invoked when the libevent timer has expired: see which tor_timer_t events + * have fired, activate their callbacks, and reschedule the libevent timer. + */ +static void +libevent_timer_callback(evutil_socket_t fd, short what, void *arg) +{ + (void)fd; + (void)what; + (void)arg; + + struct timeval now; + tor_gettimeofday_cached_monotonic(&now); + timer_advance_to_cur_time(&now); + + tor_timer_t *t; + while ((t = timeouts_get(global_timeouts))) { + t->callback.cb(t, t->callback.arg, &now); + } + + tor_gettimeofday_cache_clear(); + libevent_timer_reschedule(); +} + +/** + * Initialize the timers subsystem. Requires that libevent has already been + * initialized. + */ +void +timers_initialize(void) +{ + if (global_timeouts) + return; + + timeout_error_t err; + global_timeouts = timeouts_open(0, &err); + if (!global_timeouts) { + log_err(LD_BUG, "Unable to open timer backend: %s", strerror(err)); + tor_assert(0); + } + + struct event *timer_event; + timer_event = tor_event_new(tor_libevent_get_base(), + -1, 0, libevent_timer_callback, NULL); + tor_assert(timer_event); + global_timer_event = timer_event; +} + +/** + * Release all storage held in the timers subsystem. Does not fire timers. + */ +void +timers_shutdown(void) +{ + if (global_timer_event) { + tor_event_free(global_timer_event); + global_timer_event = NULL; + } + if (global_timeouts) { + timeouts_close(global_timeouts); + global_timeouts = NULL; + } +} + +/** + * Allocate and return a new timer, with given callback and argument. + */ +tor_timer_t * +timer_new(timer_cb_fn_t cb, void *arg) +{ + tor_timer_t *t = tor_malloc(sizeof(tor_timer_t)); + timeout_init(t, 0); + timer_set_cb(t, cb, arg); + return t; +} + +/** + * Release all storage held by <b>t</b>, and unschedule it if was already + * scheduled. + */ +void +timer_free(tor_timer_t *t) +{ + if (! t) + return; + + timeouts_del(global_timeouts, t); + tor_free(t); +} + +/** + * Change the callback and argument associated with a timer <b>t</b>. + */ +void +timer_set_cb(tor_timer_t *t, timer_cb_fn_t cb, void *arg) +{ + t->callback.cb = cb; + t->callback.arg = arg; +} + +/** + * Schedule the timer t to fire at the current time plus a delay of <b>tv</b>. + * All times are relative to tor_gettimeofday_cached_monotonic. + */ +void +timer_schedule(tor_timer_t *t, const struct timeval *tv) +{ + const timeout_t when = tv_to_timeout(tv); + struct timeval now; + tor_gettimeofday_cached_monotonic(&now); + timer_advance_to_cur_time(&now); + + timeouts_add(global_timeouts, t, when); + + /* Should we update the libevent timer? */ + if (to <= when) { + return; /* we're already going to fire before this timer would trigger. */ + + libevent_timer_reschedule(); +} + +/** + * Cancel the timer <b>t</b> if it is currently scheduled. (It's okay to call + * this on an unscheduled timer. + */ +void +timer_disable(tor_timer_t *t) +{ + timeouts_del(global_timeouts, t); + /* We don't reschedule the libevent timer here, since it's okay if it fires + * early. */ +} + diff --git a/src/common/timers.h b/src/common/timers.h new file mode 100644 index 0000000..594cf38 --- /dev/null +++ b/src/common/timers.h @@ -0,0 +1,22 @@ +/* Copyright (c) 2016, The Tor Project, Inc. */ +/* See LICENSE for licensing information */ + +#ifndef TOR_TIMERS_H +#define TOR_TIMERS_H + +#include "orconfig.h" +#include "testsupport.h" + +typedef struct timeout tor_timer_t; +typedef void (*timer_cb_fn_t)(tor_timer_t *, void *, const struct timeval *); +tor_timer_t *timer_new(timer_cb_fn_t cb, void *arg); +void timer_set_cb(tor_timer_t *t, timer_cb_fn_t cb, void *arg); +void timer_schedule(tor_timer_t *t, const struct timeval *delay); +void timer_disable(tor_timer_t *t); +void timer_free(tor_timer_t *t); + +void timers_initialize(void); +void timers_shutdown(void); + +#endif + diff --git a/src/ext/include.am b/src/ext/include.am index 42a38f1..d1a3b47 100644 --- a/src/ext/include.am +++ b/src/ext/include.am @@ -10,11 +10,13 @@ EXTHEADERS = \ src/ext/tor_readpassphrase.h \ src/ext/strlcat.c \ src/ext/strlcpy.c \ - src/ext/timeouts/timeout.h \ - src/ext/timeouts/timeout-debug.h \ src/ext/tinytest_macros.h \ src/ext/tor_queue.h \ - src/ext/siphash.h + src/ext/siphash.h \ + src/ext/timeouts/timeout.h \ + src/ext/timeouts/timeout-debug.h \ + src/ext/timeouts/timeout-bitops.c \ + src/ext/timeouts/timeout.c noinst_HEADERS+= $(EXTHEADERS) @@ -166,7 +168,5 @@ EXTRA_DIST += \ timeouts/lua/timeout-lua.c \ timeouts/Makefile \ timeouts/Rules.shrc \ - timeouts/test-timeout.c \ - timeouts/timeout-bitops.c - + timeouts/test-timeout.c