res_timing_timerfd.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 2008, Digium, Inc.
 *
 * Mark Michelson <[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 Mark Michelson <[email protected]>
 *
 * \brief timerfd timing interface
 */

/*** MODULEINFO
   <depend>timerfd</depend>
   <support_level>core</support_level>
 ***/

#include "asterisk.h"

#include <sys/timerfd.h>

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

static void *timing_funcs_handle;

static void *timerfd_timer_open(void);
static void timerfd_timer_close(void *data);
static int timerfd_timer_set_rate(void *data, unsigned int rate);
static int timerfd_timer_ack(void *data, unsigned int quantity);
static int timerfd_timer_enable_continuous(void *data);
static int timerfd_timer_disable_continuous(void *data);
static enum ast_timer_event timerfd_timer_get_event(void *data);
static unsigned int timerfd_timer_get_max_rate(void *data);
static int timerfd_timer_fd(void *data);

static struct ast_timing_interface timerfd_timing = {
   .name = "timerfd",
   .priority = 200,
   .timer_open = timerfd_timer_open,
   .timer_close = timerfd_timer_close,
   .timer_set_rate = timerfd_timer_set_rate,
   .timer_ack = timerfd_timer_ack,
   .timer_enable_continuous = timerfd_timer_enable_continuous,
   .timer_disable_continuous = timerfd_timer_disable_continuous,
   .timer_get_event = timerfd_timer_get_event,
   .timer_get_max_rate = timerfd_timer_get_max_rate,
   .timer_fd = timerfd_timer_fd,
};

#define TIMERFD_MAX_RATE 1000

struct timerfd_timer {
   int fd;
   struct itimerspec saved_timer;
   unsigned int is_continuous:1;
};

static void timer_destroy(void *obj)
{
   struct timerfd_timer *timer = obj;
   if (timer->fd > -1) {
      close(timer->fd);
   }
}

static void *timerfd_timer_open(void)
{
   struct timerfd_timer *timer;

   if (!(timer = ao2_alloc(sizeof(*timer), timer_destroy))) {
      ast_log(LOG_ERROR, "Could not allocate memory for timerfd_timer structure\n");
      return NULL;
   }
   if ((timer->fd = timerfd_create(CLOCK_MONOTONIC, 0)) < 0) {
      ast_log(LOG_ERROR, "Failed to create timerfd timer: %s\n", strerror(errno));
      ao2_ref(timer, -1);
      return NULL;
   }

   return timer;
}

static void timerfd_timer_close(void *data)
{
   ao2_ref(data, -1);
}

static int timerfd_timer_set_rate(void *data, unsigned int rate)
{
   struct timerfd_timer *timer = data;
   int res = 0;

   ao2_lock(timer);

   timer->saved_timer.it_value.tv_sec = 0;
   timer->saved_timer.it_value.tv_nsec = rate ? (long) (1000000000 / rate) : 0L;
   timer->saved_timer.it_interval.tv_sec = timer->saved_timer.it_value.tv_sec;
   timer->saved_timer.it_interval.tv_nsec = timer->saved_timer.it_value.tv_nsec;

   if (!timer->is_continuous) {
      res = timerfd_settime(timer->fd, 0, &timer->saved_timer, NULL);
   }

   ao2_unlock(timer);

   return res;
}

static int timerfd_timer_ack(void *data, unsigned int quantity)
{
   struct timerfd_timer *timer = data;
   uint64_t expirations;
   int read_result = 0;
   int res = 0;

   ao2_lock(timer);

   do {
      struct itimerspec timer_status;

      if (timerfd_gettime(timer->fd, &timer_status)) {
         ast_log(LOG_ERROR, "Call to timerfd_gettime() using handle %d error: %s\n", timer->fd, strerror(errno));
         expirations = 0;
         res = -1;
         break;
      }

      if (timer_status.it_value.tv_sec == 0 && timer_status.it_value.tv_nsec == 0) {
         ast_debug(1, "Avoiding read on disarmed timerfd %d\n", timer->fd);
         expirations = 0;
         break;
      }

      read_result = read(timer->fd, &expirations, sizeof(expirations));
      if (read_result == -1) {
         if (errno == EINTR || errno == EAGAIN) {
            continue;
         } else {
            ast_log(LOG_ERROR, "Read error: %s\n", strerror(errno));
            res = -1;
            break;
         }
      }
   } while (read_result != sizeof(expirations));

   ao2_unlock(timer);

   if (expirations != quantity) {
      ast_debug(2, "Expected to acknowledge %u ticks but got %llu instead\n", quantity, (unsigned long long) expirations);
   }

   return res;
}

static int timerfd_timer_enable_continuous(void *data)
{
   struct timerfd_timer *timer = data;
   int res;
   static const struct itimerspec continuous_timer = {
      .it_value.tv_nsec = 1L,
   };

   ao2_lock(timer);

   if (timer->is_continuous) {
      /*It's already in continous mode, no need to do
       * anything further
       */
      ao2_unlock(timer);
      return 0;
   }

   res = timerfd_settime(timer->fd, 0, &continuous_timer, &timer->saved_timer);
   timer->is_continuous = 1;
   ao2_unlock(timer);

   return res;
}

static int timerfd_timer_disable_continuous(void *data)
{
   struct timerfd_timer *timer = data;
   int res;

   ao2_lock(timer);

   if (!timer->is_continuous) {
      /* No reason to do anything if we're not
       * in continuous mode
       */
      ao2_unlock(timer);
      return 0;
   }

   res = timerfd_settime(timer->fd, 0, &timer->saved_timer, NULL);
   timer->is_continuous = 0;
   memset(&timer->saved_timer, 0, sizeof(timer->saved_timer));
   ao2_unlock(timer);

   return res;
}

static enum ast_timer_event timerfd_timer_get_event(void *data)
{
   struct timerfd_timer *timer = data;
   enum ast_timer_event res;

   ao2_lock(timer);

   if (timer->is_continuous) {
      res = AST_TIMING_EVENT_CONTINUOUS;
   } else {
      res = AST_TIMING_EVENT_EXPIRED;
   }

   ao2_unlock(timer);

   return res;
}

static unsigned int timerfd_timer_get_max_rate(void *data)
{
   return TIMERFD_MAX_RATE;
}

static int timerfd_timer_fd(void *data)
{
   struct timerfd_timer *timer = data;

   return timer->fd;
}

static int load_module(void)
{
   int fd;

   /* Make sure we support the necessary clock type */
   if ((fd = timerfd_create(CLOCK_MONOTONIC, 0)) < 0) {
      ast_log(LOG_ERROR, "timerfd_create() not supported by the kernel.  Not loading.\n");
      return AST_MODULE_LOAD_DECLINE;
   }

   close(fd);

   if (!(timing_funcs_handle = ast_register_timing_interface(&timerfd_timing))) {
      return AST_MODULE_LOAD_DECLINE;
   }

   return AST_MODULE_LOAD_SUCCESS;
}

static int unload_module(void)
{
   return ast_unregister_timing_interface(timing_funcs_handle);
}

AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_LOAD_ORDER, "Timerfd Timing Interface",
   .support_level = AST_MODULE_SUPPORT_CORE,
   .load = load_module,
   .unload = unload_module,
   .load_pri = AST_MODPRI_TIMING,
);