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sched.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 1999 - 2005, Digium, Inc.
 *
 * Mark Spencer <markster@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
 *
 * \brief Scheduler Routines (from cheops-NG)
 *
 * \author Mark Spencer <markster@digium.com>
 */

#include "asterisk.h"

ASTERISK_FILE_VERSION(__FILE__, "$Revision: 44253 $")

#ifdef DEBUG_SCHEDULER
#define DEBUG(a) do { \
   if (option_debug) \
      DEBUG_M(a) \
   } while (0)
#else
#define DEBUG(a) 
#endif

#include <stdio.h>
#include <stdlib.h>
#include <sys/time.h>
#include <unistd.h>
#include <string.h>

#include "asterisk/sched.h"
#include "asterisk/logger.h"
#include "asterisk/channel.h"
#include "asterisk/lock.h"
#include "asterisk/utils.h"
#include "asterisk/linkedlists.h"
#include "asterisk/options.h"

struct sched {
   AST_LIST_ENTRY(sched) list;
   int id;                       /*!< ID number of event */
   struct timeval when;          /*!< Absolute time event should take place */
   int resched;                  /*!< When to reschedule */
   int variable;                 /*!< Use return value from callback to reschedule */
   void *data;                   /*!< Data */
   ast_sched_cb callback;        /*!< Callback */
};

struct sched_context {
   ast_mutex_t lock;
   unsigned int eventcnt;                  /*!< Number of events processed */
   unsigned int schedcnt;                  /*!< Number of outstanding schedule events */
   AST_LIST_HEAD_NOLOCK(, sched) schedq;   /*!< Schedule entry and main queue */

#ifdef SCHED_MAX_CACHE
   AST_LIST_HEAD_NOLOCK(, sched) schedc;   /*!< Cache of unused schedule structures and how many */
   unsigned int schedccnt;
#endif
};

struct sched_context *sched_context_create(void)
{
   struct sched_context *tmp;

   if (!(tmp = ast_calloc(1, sizeof(*tmp))))
      return NULL;

   ast_mutex_init(&tmp->lock);
   tmp->eventcnt = 1;
   
   return tmp;
}

void sched_context_destroy(struct sched_context *con)
{
   struct sched *s;

   ast_mutex_lock(&con->lock);

#ifdef SCHED_MAX_CACHE
   /* Eliminate the cache */
   while ((s = AST_LIST_REMOVE_HEAD(&con->schedc, list)))
      free(s);
#endif

   /* And the queue */
   while ((s = AST_LIST_REMOVE_HEAD(&con->schedq, list)))
      free(s);
   
   /* And the context */
   ast_mutex_unlock(&con->lock);
   ast_mutex_destroy(&con->lock);
   free(con);
}

static struct sched *sched_alloc(struct sched_context *con)
{
   struct sched *tmp;

   /*
    * We keep a small cache of schedule entries
    * to minimize the number of necessary malloc()'s
    */
#ifdef SCHED_MAX_CACHE
   if ((tmp = AST_LIST_REMOVE_HEAD(&con->schedc, list)))
      con->schedccnt--;
   else
#endif
      tmp = ast_calloc(1, sizeof(*tmp));

   return tmp;
}

static void sched_release(struct sched_context *con, struct sched *tmp)
{
   /*
    * Add to the cache, or just free() if we
    * already have too many cache entries
    */

#ifdef SCHED_MAX_CACHE   
   if (con->schedccnt < SCHED_MAX_CACHE) {
      AST_LIST_INSERT_HEAD(&con->schedc, tmp, list);
      con->schedccnt++;
   } else
#endif
      free(tmp);
}

/*! \brief
 * Return the number of milliseconds 
 * until the next scheduled event
 */
int ast_sched_wait(struct sched_context *con)
{
   int ms;

   DEBUG(ast_log(LOG_DEBUG, "ast_sched_wait()\n"));

   ast_mutex_lock(&con->lock);
   if (AST_LIST_EMPTY(&con->schedq)) {
      ms = -1;
   } else {
      ms = ast_tvdiff_ms(AST_LIST_FIRST(&con->schedq)->when, ast_tvnow());
      if (ms < 0)
         ms = 0;
   }
   ast_mutex_unlock(&con->lock);

   return ms;
}


/*! \brief
 * Take a sched structure and put it in the
 * queue, such that the soonest event is
 * first in the list. 
 */
static void schedule(struct sched_context *con, struct sched *s)
{
    
   struct sched *cur = NULL;
   
   AST_LIST_TRAVERSE_SAFE_BEGIN(&con->schedq, cur, list) {
      if (ast_tvcmp(s->when, cur->when) == -1) {
         AST_LIST_INSERT_BEFORE_CURRENT(&con->schedq, s, list);
         break;
      }
   }
   AST_LIST_TRAVERSE_SAFE_END
   if (!cur)
      AST_LIST_INSERT_TAIL(&con->schedq, s, list);
   
   con->schedcnt++;
}

/*! \brief
 * given the last event *tv and the offset in milliseconds 'when',
 * computes the next value,
 */
static int sched_settime(struct timeval *tv, int when)
{
   struct timeval now = ast_tvnow();

   /*ast_log(LOG_DEBUG, "TV -> %lu,%lu\n", tv->tv_sec, tv->tv_usec);*/
   if (ast_tvzero(*tv)) /* not supplied, default to now */
      *tv = now;
   *tv = ast_tvadd(*tv, ast_samp2tv(when, 1000));
   if (ast_tvcmp(*tv, now) < 0) {
      if (option_debug)
         ast_log(LOG_DEBUG, "Request to schedule in the past?!?!\n");
      *tv = now;
   }
   return 0;
}


/*! \brief
 * Schedule callback(data) to happen when ms into the future
 */
int ast_sched_add_variable(struct sched_context *con, int when, ast_sched_cb callback, void *data, int variable)
{
   struct sched *tmp;
   int res = -1;
   DEBUG(ast_log(LOG_DEBUG, "ast_sched_add()\n"));
   if (!when) {
      ast_log(LOG_NOTICE, "Scheduled event in 0 ms?\n");
      return -1;
   }
   ast_mutex_lock(&con->lock);
   if ((tmp = sched_alloc(con))) {
      tmp->id = con->eventcnt++;
      tmp->callback = callback;
      tmp->data = data;
      tmp->resched = when;
      tmp->variable = variable;
      tmp->when = ast_tv(0, 0);
      if (sched_settime(&tmp->when, when)) {
         sched_release(con, tmp);
      } else {
         schedule(con, tmp);
         res = tmp->id;
      }
   }
#ifdef DUMP_SCHEDULER
   /* Dump contents of the context while we have the lock so nothing gets screwed up by accident. */
   if (option_debug)
      ast_sched_dump(con);
#endif
   ast_mutex_unlock(&con->lock);
   return res;
}

int ast_sched_add(struct sched_context *con, int when, ast_sched_cb callback, void *data)
{
   return ast_sched_add_variable(con, when, callback, data, 0);
}

/*! \brief
 * Delete the schedule entry with number
 * "id".  It's nearly impossible that there
 * would be two or more in the list with that
 * id.
 */
int ast_sched_del(struct sched_context *con, int id)
{
   struct sched *s;

   DEBUG(ast_log(LOG_DEBUG, "ast_sched_del()\n"));
   
   ast_mutex_lock(&con->lock);
   AST_LIST_TRAVERSE_SAFE_BEGIN(&con->schedq, s, list) {
      if (s->id == id) {
         AST_LIST_REMOVE_CURRENT(&con->schedq, list);
         con->schedcnt--;
         sched_release(con, s);
         break;
      }
   }
   AST_LIST_TRAVERSE_SAFE_END

#ifdef DUMP_SCHEDULER
   /* Dump contents of the context while we have the lock so nothing gets screwed up by accident. */
   if (option_debug)
      ast_sched_dump(con);
#endif
   ast_mutex_unlock(&con->lock);

   if (!s) {
      ast_log(LOG_NOTICE, "Attempted to delete nonexistent schedule entry %d!\n", id);
#ifdef DO_CRASH
      CRASH;
#endif
      return -1;
   }
   
   return 0;
}

/*! \brief Dump the contents of the scheduler to LOG_DEBUG */
void ast_sched_dump(const struct sched_context *con)
{
   struct sched *q;
   struct timeval tv = ast_tvnow();
#ifdef SCHED_MAX_CACHE
   if (option_debug)
      ast_log(LOG_DEBUG, "Asterisk Schedule Dump (%d in Q, %d Total, %d Cache)\n", con->schedcnt, con->eventcnt - 1, con->schedccnt);
#else
   if (option_debug)
      ast_log(LOG_DEBUG, "Asterisk Schedule Dump (%d in Q, %d Total)\n", con->schedcnt, con->eventcnt - 1);
#endif

   if (option_debug) {
   ast_log(LOG_DEBUG, "=============================================================\n");
   ast_log(LOG_DEBUG, "|ID    Callback          Data              Time  (sec:ms)   |\n");
   ast_log(LOG_DEBUG, "+-----+-----------------+-----------------+-----------------+\n");
      AST_LIST_TRAVERSE(&con->schedq, q, list) {
         struct timeval delta = ast_tvsub(q->when, tv);

         ast_log(LOG_DEBUG, "|%.4d | %-15p | %-15p | %.6ld : %.6ld |\n", 
            q->id,
            q->callback,
            q->data,
            delta.tv_sec,
            (long int)delta.tv_usec);
      }
      ast_log(LOG_DEBUG, "=============================================================\n");
   }
}

/*! \brief
 * Launch all events which need to be run at this time.
 */
int ast_sched_runq(struct sched_context *con)
{
   struct sched *current;
   struct timeval tv;
   int numevents;
   int res;

   DEBUG(ast_log(LOG_DEBUG, "ast_sched_runq()\n"));
      
   ast_mutex_lock(&con->lock);

   for (numevents = 0; !AST_LIST_EMPTY(&con->schedq); numevents++) {
      /* schedule all events which are going to expire within 1ms.
       * We only care about millisecond accuracy anyway, so this will
       * help us get more than one event at one time if they are very
       * close together.
       */
      tv = ast_tvadd(ast_tvnow(), ast_tv(0, 1000));
      if (ast_tvcmp(AST_LIST_FIRST(&con->schedq)->when, tv) != -1)
         break;
      
      current = AST_LIST_REMOVE_HEAD(&con->schedq, list);
      con->schedcnt--;

      /*
       * At this point, the schedule queue is still intact.  We
       * have removed the first event and the rest is still there,
       * so it's permissible for the callback to add new events, but
       * trying to delete itself won't work because it isn't in
       * the schedule queue.  If that's what it wants to do, it 
       * should return 0.
       */
         
      ast_mutex_unlock(&con->lock);
      res = current->callback(current->data);
      ast_mutex_lock(&con->lock);
         
      if (res) {
         /*
          * If they return non-zero, we should schedule them to be
          * run again.
          */
         if (sched_settime(&current->when, current->variable? res : current->resched)) {
            sched_release(con, current);
         } else
            schedule(con, current);
      } else {
         /* No longer needed, so release it */
         sched_release(con, current);
      }
   }

   ast_mutex_unlock(&con->lock);
   
   return numevents;
}

long ast_sched_when(struct sched_context *con,int id)
{
   struct sched *s;
   long secs = -1;
   DEBUG(ast_log(LOG_DEBUG, "ast_sched_when()\n"));

   ast_mutex_lock(&con->lock);
   AST_LIST_TRAVERSE(&con->schedq, s, list) {
      if (s->id == id)
         break;
   }
   if (s) {
      struct timeval now = ast_tvnow();
      secs = s->when.tv_sec - now.tv_sec;
   }
   ast_mutex_unlock(&con->lock);
   
   return secs;
}

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