res_timing_pthread.c

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