res_timing_pthread.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 2008, Digium, Inc.
 *
 * Russell Bryant <[email protected]>
 *
 * See http://www.asterisk.org for more information about
 * the Asterisk project. Please do not directly contact
 * any of the maintainers of this project for assistance;
 * the project provides a web site, mailing lists and IRC
 * channels for your use.
 *
 * This program is free software, distributed under the terms of
 * the GNU General Public License Version 2. See the LICENSE file
 * at the top of the source tree.
 */

/*!
 * \file
 * \author Russell Bryant <[email protected]>
 *
 * \brief pthread timing interface
 */

/*** MODULEINFO
 <support_level>extended</support_level>
 ***/

#include "asterisk.h"

#include <stdbool.h>
#include <math.h>
#include <unistd.h>
#include <fcntl.h>

#include "asterisk/module.h"
#include "asterisk/timing.h"
#include "asterisk/utils.h"
#include "asterisk/astobj2.h"
#include "asterisk/time.h"
#include "asterisk/lock.h"

static void *timing_funcs_handle;

static void *pthread_timer_open(void);
static void pthread_timer_close(void *data);
static int pthread_timer_set_rate(void *data, unsigned int rate);
static int pthread_timer_ack(void *data, unsigned int quantity);
static int pthread_timer_enable_continuous(void *data);
static int pthread_timer_disable_continuous(void *data);
static enum ast_timer_event pthread_timer_get_event(void *data);
static unsigned int pthread_timer_get_max_rate(void *data);
static int pthread_timer_fd(void *data);

static struct ast_timing_interface pthread_timing = {
 .name = "pthread",
 .priority = 0, /* use this as a last resort */
 .timer_open = pthread_timer_open,
 .timer_close = pthread_timer_close,
 .timer_set_rate = pthread_timer_set_rate,
 .timer_ack = pthread_timer_ack,
 .timer_enable_continuous = pthread_timer_enable_continuous,
 .timer_disable_continuous = pthread_timer_disable_continuous,
 .timer_get_event = pthread_timer_get_event,
 .timer_get_max_rate = pthread_timer_get_max_rate,
 .timer_fd = pthread_timer_fd,
};

/* 1 tick / 10 ms */
#define MAX_RATE 100

static struct ao2_container *pthread_timers;
#define PTHREAD_TIMER_BUCKETS 563

enum {
 PIPE_READ = 0,
 PIPE_WRITE = 1
};

enum pthread_timer_state {
 TIMER_STATE_IDLE,
 TIMER_STATE_TICKING,
};

struct pthread_timer {
 int pipe[2];
 enum pthread_timer_state state;
 unsigned int rate;
 /*! Interval in ms for current rate */
 unsigned int interval;
 unsigned int tick_count;
 unsigned int pending_ticks;
 struct timeval start;
 bool continuous:1;
 bool pipe_signaled:1;
};

static void pthread_timer_destructor(void *obj);
static void signal_pipe(struct pthread_timer *timer);
static void unsignal_pipe(struct pthread_timer *timer);
static void ack_ticks(struct pthread_timer *timer, unsigned int num);

/*!
 * \brief Data for the timing thread
 */
static struct {
 pthread_t thread;
 ast_mutex_t lock;
 ast_cond_t cond;
 unsigned int stop:1;
} timing_thread;

static void *pthread_timer_open(void)
{
 struct pthread_timer *timer;

 if (!(timer = ao2_alloc(sizeof(*timer), pthread_timer_destructor))) {
 errno = ENOMEM;
 return NULL;
 }

 timer->pipe[PIPE_READ] = timer->pipe[PIPE_WRITE] = -1;
 timer->state = TIMER_STATE_IDLE;

 if (ast_pipe_nonblock(timer->pipe)) {
 ao2_ref(timer, -1);
 return NULL;
 }

 ao2_lock(pthread_timers);
 if (!ao2_container_count(pthread_timers)) {
 ast_mutex_lock(&timing_thread.lock);
 ast_cond_signal(&timing_thread.cond);
 ast_mutex_unlock(&timing_thread.lock);
 }
 ao2_link_flags(pthread_timers, timer, OBJ_NOLOCK);
 ao2_unlock(pthread_timers);

 return timer;
}

static void pthread_timer_close(void *data)
{
 struct pthread_timer *timer = data;

 ao2_unlink(pthread_timers, timer);
 ao2_ref(timer, -1);
}

static int pthread_timer_set_rate(void *data, unsigned int rate)
{
 struct pthread_timer *timer = data;

 if (rate > MAX_RATE) {
 ast_log(LOG_ERROR, "res_timing_pthread only supports timers at a "
 "max rate of %d / sec\n", MAX_RATE);
 errno = EINVAL;
 return -1;
 }

 ao2_lock(timer);

 if ((timer->rate = rate)) {
 timer->interval = roundf(1000.0 / ((float) rate));
 timer->start = ast_tvnow();
 timer->state = TIMER_STATE_TICKING;
 } else {
 timer->interval = 0;
 timer->start = ast_tv(0, 0);
 timer->state = TIMER_STATE_IDLE;
 }
 timer->tick_count = 0;

 ao2_unlock(timer);

 return 0;
}

static int pthread_timer_ack(void *data, unsigned int quantity)
{
 struct pthread_timer *timer = data;

 ast_assert(quantity > 0);

 ao2_lock(timer);
 ack_ticks(timer, quantity);
 ao2_unlock(timer);

 return 0;
}

static int pthread_timer_enable_continuous(void *data)
{
 struct pthread_timer *timer = data;

 ao2_lock(timer);
 if (!timer->continuous) {
 timer->continuous = true;
 signal_pipe(timer);
 }
 ao2_unlock(timer);

 return 0;
}

static int pthread_timer_disable_continuous(void *data)
{
 struct pthread_timer *timer = data;

 ao2_lock(timer);
 if (timer->continuous) {
 timer->continuous = false;
 unsignal_pipe(timer);
 }
 ao2_unlock(timer);

 return 0;
}

static enum ast_timer_event pthread_timer_get_event(void *data)
{
 struct pthread_timer *timer = data;
 enum ast_timer_event res = AST_TIMING_EVENT_EXPIRED;

 ao2_lock(timer);
 if (timer->continuous) {
 res = AST_TIMING_EVENT_CONTINUOUS;
 }
 ao2_unlock(timer);

 return res;
}

static unsigned int pthread_timer_get_max_rate(void *data)
{
 return MAX_RATE;
}

static int pthread_timer_fd(void *data)
{
 struct pthread_timer *timer = data;

 return timer->pipe[PIPE_READ];
}

static void pthread_timer_destructor(void *obj)
{
 struct pthread_timer *timer = obj;

 if (timer->pipe[PIPE_READ] > -1) {
 close(timer->pipe[PIPE_READ]);
 timer->pipe[PIPE_READ] = -1;
 }

 if (timer->pipe[PIPE_WRITE] > -1) {
 close(timer->pipe[PIPE_WRITE]);
 timer->pipe[PIPE_WRITE] = -1;
 }
}

/*!
 * \note only PIPE_READ is guaranteed valid
 */
static int pthread_timer_hash(const void *obj, const int flags)
{
 const struct pthread_timer *timer = obj;

 return timer->pipe[PIPE_READ];
}

/*!
 * \note only PIPE_READ is guaranteed valid
 */
static int pthread_timer_cmp(void *obj, void *arg, int flags)
{
 struct pthread_timer *timer1 = obj, *timer2 = arg;

 return (timer1->pipe[PIPE_READ] == timer2->pipe[PIPE_READ]) ? CMP_MATCH | CMP_STOP : 0;
}

/*!
 * \retval 0 no timer tick needed
 * \retval non-zero write to the timing pipe needed
 */
static int check_timer(struct pthread_timer *timer)
{
 struct timeval now;

 if (timer->state == TIMER_STATE_IDLE) {
 return 0;
 }

 now = ast_tvnow();

 if (timer->tick_count < (ast_tvdiff_ms(now, timer->start) / timer->interval)) {
 timer->tick_count++;
 if (!timer->tick_count) {
 /* Handle overflow. */
 timer->start = now;
 }
 return 1;
 }

 return 0;
}

/*!
 * \internal
 * \pre timer is locked
 */
static void ack_ticks(struct pthread_timer *timer, unsigned int quantity)
{
 int pending_ticks = timer->pending_ticks;

 ast_assert(quantity);

 if (quantity > pending_ticks) {
 quantity = pending_ticks;
 }

 if (!quantity) {
 return;
 }

 timer->pending_ticks -= quantity;

 if ((0 == timer->pending_ticks) && !timer->continuous) {
 unsignal_pipe(timer);
 }
}

/*!
 * \internal
 * \pre timer is locked
 */
static void signal_pipe(struct pthread_timer *timer)
{
 ssize_t res;
 unsigned char x = 42;

 if (timer->pipe_signaled) {
 return;
 }

 res = write(timer->pipe[PIPE_WRITE], &x, 1);
 if (-1 == res) {
 ast_log(LOG_ERROR, "Error writing to timing pipe: %s\n",
 strerror(errno));
 } else {
 timer->pipe_signaled = true;
 }
}

/*!
 * \internal
 * \pre timer is locked
 */
static void unsignal_pipe(struct pthread_timer *timer)
{
 ssize_t res;
 unsigned long buffer;

 if (!timer->pipe_signaled) {
 return;
 }

 res = read(timer->pipe[PIPE_READ], &buffer, sizeof(buffer));
 if (-1 == res) {
 ast_log(LOG_ERROR, "Error reading from pipe: %s\n",
 strerror(errno));
 } else {
 timer->pipe_signaled = false;
 }
}

static int run_timer(void *obj, void *arg, int flags)
{
 struct pthread_timer *timer = obj;

 if (timer->state == TIMER_STATE_IDLE) {
 return 0;
 }

 ao2_lock(timer);
 if (check_timer(timer)) {
 timer->pending_ticks++;
 signal_pipe(timer);
 }
 ao2_unlock(timer);

 return 0;
}

static void *do_timing(void *arg)
{
 struct timeval next_wakeup = ast_tvnow();

 while (!timing_thread.stop) {
 struct timespec ts = { 0, };

 ao2_callback(pthread_timers, OBJ_NODATA, run_timer, NULL);

 next_wakeup = ast_tvadd(next_wakeup, ast_tv(0, 5000));

 ts.tv_sec = next_wakeup.tv_sec;
 ts.tv_nsec = next_wakeup.tv_usec * 1000;

 ast_mutex_lock(&timing_thread.lock);
 if (!timing_thread.stop) {
 if (ao2_container_count(pthread_timers)) {
 ast_cond_timedwait(&timing_thread.cond, &timing_thread.lock, &ts);
 } else {
 ast_cond_wait(&timing_thread.cond, &timing_thread.lock);
 }
 }
 ast_mutex_unlock(&timing_thread.lock);
 }

 return NULL;
}

static int init_timing_thread(void)
{
 ast_mutex_init(&timing_thread.lock);
 ast_cond_init(&timing_thread.cond, NULL);

 if (ast_pthread_create_background(&timing_thread.thread, NULL, do_timing, NULL)) {
 ast_log(LOG_ERROR, "Unable to start timing thread.\n");
 return -1;
 }

 return 0;
}

static int load_module(void)
{
 pthread_timers = ao2_container_alloc_hash(AO2_ALLOC_OPT_LOCK_MUTEX, 0,
 PTHREAD_TIMER_BUCKETS, pthread_timer_hash, NULL, pthread_timer_cmp);
 if (!pthread_timers) {
 return AST_MODULE_LOAD_DECLINE;
 }

 if (init_timing_thread()) {
 ao2_ref(pthread_timers, -1);
 pthread_timers = NULL;
 return AST_MODULE_LOAD_DECLINE;
 }

 return (timing_funcs_handle = ast_register_timing_interface(&pthread_timing)) ?
 AST_MODULE_LOAD_SUCCESS : AST_MODULE_LOAD_DECLINE;
}

static int unload_module(void)
{
 int res;

 ast_mutex_lock(&timing_thread.lock);
 timing_thread.stop = 1;
 ast_cond_signal(&timing_thread.cond);
 ast_mutex_unlock(&timing_thread.lock);
 pthread_join(timing_thread.thread, NULL);

 if (!(res = ast_unregister_timing_interface(timing_funcs_handle))) {
 ao2_ref(pthread_timers, -1);
 pthread_timers = NULL;
 }

 return res;
}
AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_LOAD_ORDER, "pthread Timing Interface",
 .support_level = AST_MODULE_SUPPORT_EXTENDED,
 .load = load_module,
 .unload = unload_module,
 .load_pri = AST_MODPRI_TIMING,
);