Thu Jul 9 13:40:41 2009

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: 142356 $")
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 <sys/time.h>
00040 
00041 #include "asterisk/sched.h"
00042 #include "asterisk/channel.h"
00043 #include "asterisk/lock.h"
00044 #include "asterisk/utils.h"
00045 #include "asterisk/linkedlists.h"
00046 
00047 struct sched {
00048    AST_LIST_ENTRY(sched) list;
00049    int id;                       /*!< ID number of event */
00050    struct timeval when;          /*!< Absolute time event should take place */
00051    int resched;                  /*!< When to reschedule */
00052    int variable;                 /*!< Use return value from callback to reschedule */
00053    const void *data;             /*!< Data */
00054    ast_sched_cb callback;        /*!< Callback */
00055 };
00056 
00057 struct sched_context {
00058    ast_mutex_t lock;
00059    unsigned int eventcnt;                  /*!< Number of events processed */
00060    unsigned int schedcnt;                  /*!< Number of outstanding schedule events */
00061    AST_LIST_HEAD_NOLOCK(, sched) schedq;   /*!< Schedule entry and main queue */
00062 
00063 #ifdef SCHED_MAX_CACHE
00064    AST_LIST_HEAD_NOLOCK(, sched) schedc;   /*!< Cache of unused schedule structures and how many */
00065    unsigned int schedccnt;
00066 #endif
00067 };
00068 
00069 struct sched_context *sched_context_create(void)
00070 {
00071    struct sched_context *tmp;
00072 
00073    if (!(tmp = ast_calloc(1, sizeof(*tmp))))
00074       return NULL;
00075 
00076    ast_mutex_init(&tmp->lock);
00077    tmp->eventcnt = 1;
00078    
00079    return tmp;
00080 }
00081 
00082 void sched_context_destroy(struct sched_context *con)
00083 {
00084    struct sched *s;
00085 
00086    ast_mutex_lock(&con->lock);
00087 
00088 #ifdef SCHED_MAX_CACHE
00089    /* Eliminate the cache */
00090    while ((s = AST_LIST_REMOVE_HEAD(&con->schedc, list)))
00091       ast_free(s);
00092 #endif
00093 
00094    /* And the queue */
00095    while ((s = AST_LIST_REMOVE_HEAD(&con->schedq, list)))
00096       ast_free(s);
00097    
00098    /* And the context */
00099    ast_mutex_unlock(&con->lock);
00100    ast_mutex_destroy(&con->lock);
00101    ast_free(con);
00102 }
00103 
00104 static struct sched *sched_alloc(struct sched_context *con)
00105 {
00106    struct sched *tmp;
00107 
00108    /*
00109     * We keep a small cache of schedule entries
00110     * to minimize the number of necessary malloc()'s
00111     */
00112 #ifdef SCHED_MAX_CACHE
00113    if ((tmp = AST_LIST_REMOVE_HEAD(&con->schedc, list)))
00114       con->schedccnt--;
00115    else
00116 #endif
00117       tmp = ast_calloc(1, sizeof(*tmp));
00118 
00119    return tmp;
00120 }
00121 
00122 static void sched_release(struct sched_context *con, struct sched *tmp)
00123 {
00124    /*
00125     * Add to the cache, or just free() if we
00126     * already have too many cache entries
00127     */
00128 
00129 #ifdef SCHED_MAX_CACHE   
00130    if (con->schedccnt < SCHED_MAX_CACHE) {
00131       AST_LIST_INSERT_HEAD(&con->schedc, tmp, list);
00132       con->schedccnt++;
00133    } else
00134 #endif
00135       ast_free(tmp);
00136 }
00137 
00138 /*! \brief
00139  * Return the number of milliseconds 
00140  * until the next scheduled event
00141  */
00142 int ast_sched_wait(struct sched_context *con)
00143 {
00144    int ms;
00145 
00146    DEBUG(ast_debug(1, "ast_sched_wait()\n"));
00147 
00148    ast_mutex_lock(&con->lock);
00149    if (AST_LIST_EMPTY(&con->schedq)) {
00150       ms = -1;
00151    } else {
00152       ms = ast_tvdiff_ms(AST_LIST_FIRST(&con->schedq)->when, ast_tvnow());
00153       if (ms < 0)
00154          ms = 0;
00155    }
00156    ast_mutex_unlock(&con->lock);
00157 
00158    return ms;
00159 }
00160 
00161 
00162 /*! \brief
00163  * Take a sched structure and put it in the
00164  * queue, such that the soonest event is
00165  * first in the list. 
00166  */
00167 static void schedule(struct sched_context *con, struct sched *s)
00168 {
00169     
00170    struct sched *cur = NULL;
00171    
00172    AST_LIST_TRAVERSE_SAFE_BEGIN(&con->schedq, cur, list) {
00173       if (ast_tvcmp(s->when, cur->when) == -1) {
00174          AST_LIST_INSERT_BEFORE_CURRENT(s, list);
00175          break;
00176       }
00177    }
00178    AST_LIST_TRAVERSE_SAFE_END;
00179    if (!cur)
00180       AST_LIST_INSERT_TAIL(&con->schedq, s, list);
00181    
00182    con->schedcnt++;
00183 }
00184 
00185 /*! \brief
00186  * given the last event *tv and the offset in milliseconds 'when',
00187  * computes the next value,
00188  */
00189 static int sched_settime(struct timeval *tv, int when)
00190 {
00191    struct timeval now = ast_tvnow();
00192 
00193    /*ast_debug(1, "TV -> %lu,%lu\n", tv->tv_sec, tv->tv_usec);*/
00194    if (ast_tvzero(*tv)) /* not supplied, default to now */
00195       *tv = now;
00196    *tv = ast_tvadd(*tv, ast_samp2tv(when, 1000));
00197    if (ast_tvcmp(*tv, now) < 0) {
00198       *tv = now;
00199    }
00200    return 0;
00201 }
00202 
00203 int ast_sched_replace_variable(int old_id, struct sched_context *con, int when, ast_sched_cb callback, const void *data, int variable)
00204 {
00205    /* 0 means the schedule item is new; do not delete */
00206    if (old_id > 0)
00207       ast_sched_del(con, old_id);
00208    return ast_sched_add_variable(con, when, callback, data, variable);
00209 }
00210 
00211 /*! \brief
00212  * Schedule callback(data) to happen when ms into the future
00213  */
00214 int ast_sched_add_variable(struct sched_context *con, int when, ast_sched_cb callback, const void *data, int variable)
00215 {
00216    struct sched *tmp;
00217    int res = -1;
00218 
00219    DEBUG(ast_debug(1, "ast_sched_add()\n"));
00220 
00221    ast_mutex_lock(&con->lock);
00222    if ((tmp = sched_alloc(con))) {
00223       tmp->id = con->eventcnt++;
00224       tmp->callback = callback;
00225       tmp->data = data;
00226       tmp->resched = when;
00227       tmp->variable = variable;
00228       tmp->when = ast_tv(0, 0);
00229       if (sched_settime(&tmp->when, when)) {
00230          sched_release(con, tmp);
00231       } else {
00232          schedule(con, tmp);
00233          res = tmp->id;
00234       }
00235    }
00236 #ifdef DUMP_SCHEDULER
00237    /* Dump contents of the context while we have the lock so nothing gets screwed up by accident. */
00238    if (option_debug)
00239       ast_sched_dump(con);
00240 #endif
00241    ast_mutex_unlock(&con->lock);
00242 
00243    return res;
00244 }
00245 
00246 int ast_sched_replace(int old_id, struct sched_context *con, int when, ast_sched_cb callback, const void *data)
00247 {
00248    if (old_id > -1)
00249       ast_sched_del(con, old_id);
00250    return ast_sched_add(con, when, callback, data);
00251 }
00252 
00253 int ast_sched_add(struct sched_context *con, int when, ast_sched_cb callback, const void *data)
00254 {
00255    return ast_sched_add_variable(con, when, callback, data, 0);
00256 }
00257 
00258 /*! \brief
00259  * Delete the schedule entry with number
00260  * "id".  It's nearly impossible that there
00261  * would be two or more in the list with that
00262  * id.
00263  */
00264 #ifndef AST_DEVMODE
00265 int ast_sched_del(struct sched_context *con, int id)
00266 #else
00267 int _ast_sched_del(struct sched_context *con, int id, const char *file, int line, const char *function)
00268 #endif
00269 {
00270    struct sched *s;
00271 
00272    DEBUG(ast_debug(1, "ast_sched_del()\n"));
00273    
00274    ast_mutex_lock(&con->lock);
00275    AST_LIST_TRAVERSE_SAFE_BEGIN(&con->schedq, s, list) {
00276       if (s->id == id) {
00277          AST_LIST_REMOVE_CURRENT(list);
00278          con->schedcnt--;
00279          sched_release(con, s);
00280          break;
00281       }
00282    }
00283    AST_LIST_TRAVERSE_SAFE_END;
00284 
00285 #ifdef DUMP_SCHEDULER
00286    /* Dump contents of the context while we have the lock so nothing gets screwed up by accident. */
00287    if (option_debug)
00288       ast_sched_dump(con);
00289 #endif
00290    ast_mutex_unlock(&con->lock);
00291 
00292    if (!s) {
00293       ast_debug(1, "Attempted to delete nonexistent schedule entry %d!\n", id);
00294 #ifndef AST_DEVMODE
00295       ast_assert(s != NULL);
00296 #else
00297       _ast_assert(0, "s != NULL", file, line, function);
00298 #endif
00299       return -1;
00300    }
00301    
00302    return 0;
00303 }
00304 
00305 /*! \brief Dump the contents of the scheduler to LOG_DEBUG */
00306 void ast_sched_dump(const struct sched_context *con)
00307 {
00308    struct sched *q;
00309    struct timeval tv = ast_tvnow();
00310 #ifdef SCHED_MAX_CACHE
00311    ast_debug(1, "Asterisk Schedule Dump (%d in Q, %d Total, %d Cache)\n", con->schedcnt, con->eventcnt - 1, con->schedccnt);
00312 #else
00313    ast_debug(1, "Asterisk Schedule Dump (%d in Q, %d Total)\n", con->schedcnt, con->eventcnt - 1);
00314 #endif
00315 
00316    ast_debug(1, "=============================================================\n");
00317    ast_debug(1, "|ID    Callback          Data              Time  (sec:ms)   |\n");
00318    ast_debug(1, "+-----+-----------------+-----------------+-----------------+\n");
00319    AST_LIST_TRAVERSE(&con->schedq, q, list) {
00320       struct timeval delta = ast_tvsub(q->when, tv);
00321 
00322       ast_debug(1, "|%.4d | %-15p | %-15p | %.6ld : %.6ld |\n", 
00323          q->id,
00324          q->callback,
00325          q->data,
00326          delta.tv_sec,
00327          (long int)delta.tv_usec);
00328    }
00329    ast_debug(1, "=============================================================\n");
00330 }
00331 
00332 /*! \brief
00333  * Launch all events which need to be run at this time.
00334  */
00335 int ast_sched_runq(struct sched_context *con)
00336 {
00337    struct sched *current;
00338    struct timeval tv;
00339    int numevents;
00340    int res;
00341 
00342    DEBUG(ast_debug(1, "ast_sched_runq()\n"));
00343       
00344    ast_mutex_lock(&con->lock);
00345 
00346    for (numevents = 0; !AST_LIST_EMPTY(&con->schedq); numevents++) {
00347       /* schedule all events which are going to expire within 1ms.
00348        * We only care about millisecond accuracy anyway, so this will
00349        * help us get more than one event at one time if they are very
00350        * close together.
00351        */
00352       tv = ast_tvadd(ast_tvnow(), ast_tv(0, 1000));
00353       if (ast_tvcmp(AST_LIST_FIRST(&con->schedq)->when, tv) != -1)
00354          break;
00355       
00356       current = AST_LIST_REMOVE_HEAD(&con->schedq, list);
00357       con->schedcnt--;
00358 
00359       /*
00360        * At this point, the schedule queue is still intact.  We
00361        * have removed the first event and the rest is still there,
00362        * so it's permissible for the callback to add new events, but
00363        * trying to delete itself won't work because it isn't in
00364        * the schedule queue.  If that's what it wants to do, it 
00365        * should return 0.
00366        */
00367          
00368       ast_mutex_unlock(&con->lock);
00369       res = current->callback(current->data);
00370       ast_mutex_lock(&con->lock);
00371          
00372       if (res) {
00373          /*
00374           * If they return non-zero, we should schedule them to be
00375           * run again.
00376           */
00377          if (sched_settime(&current->when, current->variable? res : current->resched)) {
00378             sched_release(con, current);
00379          } else
00380             schedule(con, current);
00381       } else {
00382          /* No longer needed, so release it */
00383          sched_release(con, current);
00384       }
00385    }
00386 
00387    ast_mutex_unlock(&con->lock);
00388    
00389    return numevents;
00390 }
00391 
00392 long ast_sched_when(struct sched_context *con,int id)
00393 {
00394    struct sched *s;
00395    long secs = -1;
00396    DEBUG(ast_debug(1, "ast_sched_when()\n"));
00397 
00398    ast_mutex_lock(&con->lock);
00399    AST_LIST_TRAVERSE(&con->schedq, s, list) {
00400       if (s->id == id)
00401          break;
00402    }
00403    if (s) {
00404       struct timeval now = ast_tvnow();
00405       secs = s->when.tv_sec - now.tv_sec;
00406    }
00407    ast_mutex_unlock(&con->lock);
00408    
00409    return secs;
00410 }

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