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,
);