res_timing_timerfd.c

Go to the documentation of this file.

/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 2008, Digium, Inc.
 *
 * Mark Michelson <mmichelson@digium.com>
 *
 * 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 <mmichelson@digium.com>
 *
 * \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,
);