Sat Aug 6 00:39:32 2011

Asterisk developer's documentation


sched.c

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00001 /*
00002  * Asterisk -- An open source telephony toolkit.
00003  *
00004  * Copyright (C) 1999 - 2005, Digium, Inc.
00005  *
00006  * Mark Spencer <markster@digium.com>
00007  *
00008  * See http://www.asterisk.org for more information about
00009  * the Asterisk project. Please do not directly contact
00010  * any of the maintainers of this project for assistance;
00011  * the project provides a web site, mailing lists and IRC
00012  * channels for your use.
00013  *
00014  * This program is free software, distributed under the terms of
00015  * the GNU General Public License Version 2. See the LICENSE file
00016  * at the top of the source tree.
00017  */
00018 
00019 /*! \file
00020  *
00021  * \brief Scheduler Routines (from cheops-NG)
00022  *
00023  * \author Mark Spencer <markster@digium.com>
00024  */
00025 
00026 #include "asterisk.h"
00027 
00028 ASTERISK_FILE_VERSION(__FILE__, "$Revision: 253631 $")
00029 
00030 #ifdef DEBUG_SCHEDULER
00031 #define DEBUG(a) do { \
00032    if (option_debug) \
00033       DEBUG_M(a) \
00034    } while (0)
00035 #else
00036 #define DEBUG(a) 
00037 #endif
00038 
00039 #include <stdio.h>
00040 #include <stdlib.h>
00041 #include <sys/time.h>
00042 #include <unistd.h>
00043 #include <string.h>
00044 
00045 #include "asterisk/sched.h"
00046 #include "asterisk/logger.h"
00047 #include "asterisk/channel.h"
00048 #include "asterisk/lock.h"
00049 #include "asterisk/utils.h"
00050 #include "asterisk/linkedlists.h"
00051 #include "asterisk/options.h"
00052 
00053 struct sched {
00054    AST_LIST_ENTRY(sched) list;
00055    int id;                       /*!< ID number of event */
00056    struct timeval when;          /*!< Absolute time event should take place */
00057    int resched;                  /*!< When to reschedule */
00058    int variable;                 /*!< Use return value from callback to reschedule */
00059    const void *data;             /*!< Data */
00060    ast_sched_cb callback;        /*!< Callback */
00061 };
00062 
00063 struct sched_context {
00064    ast_mutex_t lock;
00065    unsigned int eventcnt;                  /*!< Number of events processed */
00066    unsigned int schedcnt;                  /*!< Number of outstanding schedule events */
00067    AST_LIST_HEAD_NOLOCK(, sched) schedq;   /*!< Schedule entry and main queue */
00068 
00069 #ifdef SCHED_MAX_CACHE
00070    AST_LIST_HEAD_NOLOCK(, sched) schedc;   /*!< Cache of unused schedule structures and how many */
00071    unsigned int schedccnt;
00072 #endif
00073 };
00074 
00075 struct sched_context *sched_context_create(void)
00076 {
00077    struct sched_context *tmp;
00078 
00079    if (!(tmp = ast_calloc(1, sizeof(*tmp))))
00080       return NULL;
00081 
00082    ast_mutex_init(&tmp->lock);
00083    tmp->eventcnt = 1;
00084    
00085    return tmp;
00086 }
00087 
00088 void sched_context_destroy(struct sched_context *con)
00089 {
00090    struct sched *s;
00091 
00092    ast_mutex_lock(&con->lock);
00093 
00094 #ifdef SCHED_MAX_CACHE
00095    /* Eliminate the cache */
00096    while ((s = AST_LIST_REMOVE_HEAD(&con->schedc, list)))
00097       free(s);
00098 #endif
00099 
00100    /* And the queue */
00101    while ((s = AST_LIST_REMOVE_HEAD(&con->schedq, list)))
00102       free(s);
00103    
00104    /* And the context */
00105    ast_mutex_unlock(&con->lock);
00106    ast_mutex_destroy(&con->lock);
00107    free(con);
00108 }
00109 
00110 static struct sched *sched_alloc(struct sched_context *con)
00111 {
00112    struct sched *tmp;
00113 
00114    /*
00115     * We keep a small cache of schedule entries
00116     * to minimize the number of necessary malloc()'s
00117     */
00118 #ifdef SCHED_MAX_CACHE
00119    if ((tmp = AST_LIST_REMOVE_HEAD(&con->schedc, list)))
00120       con->schedccnt--;
00121    else
00122 #endif
00123       tmp = ast_calloc(1, sizeof(*tmp));
00124 
00125    return tmp;
00126 }
00127 
00128 static void sched_release(struct sched_context *con, struct sched *tmp)
00129 {
00130    /*
00131     * Add to the cache, or just free() if we
00132     * already have too many cache entries
00133     */
00134 
00135 #ifdef SCHED_MAX_CACHE   
00136    if (con->schedccnt < SCHED_MAX_CACHE) {
00137       AST_LIST_INSERT_HEAD(&con->schedc, tmp, list);
00138       con->schedccnt++;
00139    } else
00140 #endif
00141       free(tmp);
00142 }
00143 
00144 /*! \brief
00145  * Return the number of milliseconds 
00146  * until the next scheduled event
00147  */
00148 int ast_sched_wait(struct sched_context *con)
00149 {
00150    int ms;
00151 
00152    DEBUG(ast_log(LOG_DEBUG, "ast_sched_wait()\n"));
00153 
00154    ast_mutex_lock(&con->lock);
00155    if (AST_LIST_EMPTY(&con->schedq)) {
00156       ms = -1;
00157    } else {
00158       ms = ast_tvdiff_ms(AST_LIST_FIRST(&con->schedq)->when, ast_tvnow());
00159       if (ms < 0)
00160          ms = 0;
00161    }
00162    ast_mutex_unlock(&con->lock);
00163 
00164    return ms;
00165 }
00166 
00167 
00168 /*! \brief
00169  * Take a sched structure and put it in the
00170  * queue, such that the soonest event is
00171  * first in the list. 
00172  */
00173 static void schedule(struct sched_context *con, struct sched *s)
00174 {
00175     
00176    struct sched *cur = NULL;
00177    
00178    AST_LIST_TRAVERSE_SAFE_BEGIN(&con->schedq, cur, list) {
00179       if (ast_tvcmp(s->when, cur->when) == -1) {
00180          AST_LIST_INSERT_BEFORE_CURRENT(&con->schedq, s, list);
00181          break;
00182       }
00183    }
00184    AST_LIST_TRAVERSE_SAFE_END
00185    if (!cur)
00186       AST_LIST_INSERT_TAIL(&con->schedq, s, list);
00187    
00188    con->schedcnt++;
00189 }
00190 
00191 /*! \brief
00192  * given the last event *tv and the offset in milliseconds 'when',
00193  * computes the next value,
00194  */
00195 static int sched_settime(struct timeval *tv, int when)
00196 {
00197    struct timeval now = ast_tvnow();
00198 
00199    /*ast_log(LOG_DEBUG, "TV -> %lu,%lu\n", tv->tv_sec, tv->tv_usec);*/
00200    if (ast_tvzero(*tv)) /* not supplied, default to now */
00201       *tv = now;
00202    *tv = ast_tvadd(*tv, ast_samp2tv(when, 1000));
00203    if (ast_tvcmp(*tv, now) < 0) {
00204       *tv = now;
00205    }
00206    return 0;
00207 }
00208 
00209 
00210 /*! \brief
00211  * Schedule callback(data) to happen when ms into the future
00212  */
00213 int ast_sched_add_variable(struct sched_context *con, int when, ast_sched_cb callback, const void *data, int variable)
00214 {
00215    struct sched *tmp;
00216    int res = -1;
00217 
00218    DEBUG(ast_log(LOG_DEBUG, "ast_sched_add()\n"));
00219 
00220    ast_mutex_lock(&con->lock);
00221    if ((tmp = sched_alloc(con))) {
00222       tmp->id = con->eventcnt++;
00223       tmp->callback = callback;
00224       tmp->data = data;
00225       tmp->resched = when;
00226       tmp->variable = variable;
00227       tmp->when = ast_tv(0, 0);
00228       if (sched_settime(&tmp->when, when)) {
00229          sched_release(con, tmp);
00230       } else {
00231          schedule(con, tmp);
00232          res = tmp->id;
00233       }
00234    }
00235 #ifdef DUMP_SCHEDULER
00236    /* Dump contents of the context while we have the lock so nothing gets screwed up by accident. */
00237    if (option_debug)
00238       ast_sched_dump(con);
00239 #endif
00240    ast_mutex_unlock(&con->lock);
00241 
00242    return res;
00243 }
00244 
00245 int ast_sched_add(struct sched_context *con, int when, ast_sched_cb callback, const void *data)
00246 {
00247    return ast_sched_add_variable(con, when, callback, data, 0);
00248 }
00249 
00250 /*! \brief
00251  * Delete the schedule entry with number
00252  * "id".  It's nearly impossible that there
00253  * would be two or more in the list with that
00254  * id.
00255  */
00256 #ifndef AST_DEVMODE
00257 int ast_sched_del(struct sched_context *con, int id)
00258 #else
00259 int _ast_sched_del(struct sched_context *con, int id, const char *file, int line, const char *function)
00260 #endif
00261 {
00262    struct sched *s;
00263 
00264    DEBUG(ast_log(LOG_DEBUG, "ast_sched_del()\n"));
00265    
00266    ast_mutex_lock(&con->lock);
00267    AST_LIST_TRAVERSE_SAFE_BEGIN(&con->schedq, s, list) {
00268       if (s->id == id) {
00269          AST_LIST_REMOVE_CURRENT(&con->schedq, list);
00270          con->schedcnt--;
00271          sched_release(con, s);
00272          break;
00273       }
00274    }
00275    AST_LIST_TRAVERSE_SAFE_END
00276 
00277 #ifdef DUMP_SCHEDULER
00278    /* Dump contents of the context while we have the lock so nothing gets screwed up by accident. */
00279    if (option_debug)
00280       ast_sched_dump(con);
00281 #endif
00282    ast_mutex_unlock(&con->lock);
00283 
00284    if (!s) {
00285       if (option_debug)
00286          ast_log(LOG_DEBUG, "Attempted to delete nonexistent schedule entry %d!\n", id);
00287 #ifndef AST_DEVMODE
00288       ast_assert(s != NULL);
00289 #else
00290       _ast_assert(0, "s != NULL", file, line, function);
00291 #endif
00292       return -1;
00293    }
00294    
00295    return 0;
00296 }
00297 
00298 /*! \brief Dump the contents of the scheduler to LOG_DEBUG */
00299 void ast_sched_dump(const struct sched_context *con)
00300 {
00301    struct sched *q;
00302    struct timeval tv = ast_tvnow();
00303 #ifdef SCHED_MAX_CACHE
00304    ast_log(LOG_DEBUG, "Asterisk Schedule Dump (%d in Q, %d Total, %d Cache)\n", con->schedcnt, con->eventcnt - 1, con->schedccnt);
00305 #else
00306    ast_log(LOG_DEBUG, "Asterisk Schedule Dump (%d in Q, %d Total)\n", con->schedcnt, con->eventcnt - 1);
00307 #endif
00308 
00309    ast_log(LOG_DEBUG, "=============================================================\n");
00310    ast_log(LOG_DEBUG, "|ID    Callback          Data              Time  (sec:ms)   |\n");
00311    ast_log(LOG_DEBUG, "+-----+-----------------+-----------------+-----------------+\n");
00312    AST_LIST_TRAVERSE(&con->schedq, q, list) {
00313       struct timeval delta = ast_tvsub(q->when, tv);
00314 
00315       ast_log(LOG_DEBUG, "|%.4d | %-15p | %-15p | %.6ld : %.6ld |\n", 
00316          q->id,
00317          q->callback,
00318          q->data,
00319          (long) delta.tv_sec,
00320          (long int)delta.tv_usec);
00321    }
00322    ast_log(LOG_DEBUG, "=============================================================\n");
00323    
00324 }
00325 
00326 /*! \brief
00327  * Launch all events which need to be run at this time.
00328  */
00329 int ast_sched_runq(struct sched_context *con)
00330 {
00331    struct sched *current;
00332    struct timeval tv;
00333    int numevents;
00334    int res;
00335 
00336    DEBUG(ast_log(LOG_DEBUG, "ast_sched_runq()\n"));
00337       
00338    ast_mutex_lock(&con->lock);
00339 
00340    for (numevents = 0; !AST_LIST_EMPTY(&con->schedq); numevents++) {
00341       /* schedule all events which are going to expire within 1ms.
00342        * We only care about millisecond accuracy anyway, so this will
00343        * help us get more than one event at one time if they are very
00344        * close together.
00345        */
00346       tv = ast_tvadd(ast_tvnow(), ast_tv(0, 1000));
00347       if (ast_tvcmp(AST_LIST_FIRST(&con->schedq)->when, tv) != -1)
00348          break;
00349       
00350       current = AST_LIST_REMOVE_HEAD(&con->schedq, list);
00351       con->schedcnt--;
00352 
00353       /*
00354        * At this point, the schedule queue is still intact.  We
00355        * have removed the first event and the rest is still there,
00356        * so it's permissible for the callback to add new events, but
00357        * trying to delete itself won't work because it isn't in
00358        * the schedule queue.  If that's what it wants to do, it 
00359        * should return 0.
00360        */
00361          
00362       ast_mutex_unlock(&con->lock);
00363       res = current->callback(current->data);
00364       ast_mutex_lock(&con->lock);
00365          
00366       if (res) {
00367          /*
00368           * If they return non-zero, we should schedule them to be
00369           * run again.
00370           */
00371          if (sched_settime(&current->when, current->variable? res : current->resched)) {
00372             sched_release(con, current);
00373          } else
00374             schedule(con, current);
00375       } else {
00376          /* No longer needed, so release it */
00377          sched_release(con, current);
00378       }
00379    }
00380 
00381    ast_mutex_unlock(&con->lock);
00382    
00383    return numevents;
00384 }
00385 
00386 long ast_sched_when(struct sched_context *con,int id)
00387 {
00388    struct sched *s;
00389    long secs = -1;
00390    DEBUG(ast_log(LOG_DEBUG, "ast_sched_when()\n"));
00391 
00392    ast_mutex_lock(&con->lock);
00393    AST_LIST_TRAVERSE(&con->schedq, s, list) {
00394       if (s->id == id)
00395          break;
00396    }
00397    if (s) {
00398       struct timeval now = ast_tvnow();
00399       secs = s->when.tv_sec - now.tv_sec;
00400    }
00401    ast_mutex_unlock(&con->lock);
00402    
00403    return secs;
00404 }

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