Tue Aug 20 16:35:04 2013

Asterisk developer's documentation


func_lock.c File Reference

Dialplan mutexes. More...

#include "asterisk.h"
#include <signal.h>
#include "asterisk/lock.h"
#include "asterisk/file.h"
#include "asterisk/channel.h"
#include "asterisk/pbx.h"
#include "asterisk/module.h"
#include "asterisk/linkedlists.h"
#include "asterisk/astobj2.h"
#include "asterisk/utils.h"

Go to the source code of this file.

Data Structures

struct  channel_lock_frame
struct  lock_frame

Functions

static int ast_channel_cmp_cb (void *obj, void *arg, int flags)
static int ast_channel_hash_cb (const void *obj, const int flags)
static AST_LIST_HEAD_STATIC (locklist, lock_frame)
 AST_MODULE_INFO_STANDARD (ASTERISK_GPL_KEY,"Dialplan mutexes")
static int get_lock (struct ast_channel *chan, char *lockname, int trylock)
static int load_module (void)
static void * lock_broker (void *unused)
static void lock_fixup (void *data, struct ast_channel *oldchan, struct ast_channel *newchan)
static void lock_free (void *data)
static int lock_read (struct ast_channel *chan, const char *cmd, char *data, char *buf, size_t len)
static int trylock_read (struct ast_channel *chan, const char *cmd, char *data, char *buf, size_t len)
static int unload_module (void)
static int unlock_read (struct ast_channel *chan, const char *cmd, char *data, char *buf, size_t len)

Variables

static pthread_t broker_tid = AST_PTHREADT_NULL
static struct ast_custom_function lock_function
static struct ast_datastore_info lock_info
static struct ast_custom_function trylock_function
static int unloading = 0
static struct ast_custom_function unlock_function

Detailed Description

Dialplan mutexes.

Author:
Tilghman Lesher <func_lock_2007@the-tilghman.com>

Definition in file func_lock.c.


Function Documentation

static int ast_channel_cmp_cb ( void *  obj,
void *  arg,
int  flags 
) [static]

Definition at line 211 of file func_lock.c.

References CMP_MATCH.

Referenced by get_lock().

00212 {
00213    struct ast_channel *chan = obj, *cmp_args = arg;
00214    return strcasecmp(chan->name, cmp_args->name) ? 0 : CMP_MATCH;
00215 }

static int ast_channel_hash_cb ( const void *  obj,
const int  flags 
) [static]

Definition at line 205 of file func_lock.c.

References ast_str_case_hash().

Referenced by get_lock().

00206 {
00207    const struct ast_channel *chan = obj;
00208    return ast_str_case_hash(chan->name);
00209 }

static AST_LIST_HEAD_STATIC ( locklist  ,
lock_frame   
) [static]
AST_MODULE_INFO_STANDARD ( ASTERISK_GPL_KEY  ,
"Dialplan mutexes"   
)
static int get_lock ( struct ast_channel chan,
char *  lockname,
int  trylock 
) [static]

Definition at line 217 of file func_lock.c.

References ao2_container_alloc, ao2_link, ao2_unlink, ast_calloc, ast_channel_cmp_cb(), ast_channel_datastore_add(), ast_channel_datastore_find(), ast_channel_hash_cb(), ast_cond_destroy, ast_cond_init, ast_cond_timedwait, ast_datastore_alloc, ast_datastore_free(), ast_debug, ast_free, AST_LIST_HEAD, AST_LIST_HEAD_INIT, AST_LIST_INSERT_TAIL, AST_LIST_LOCK, AST_LIST_TRAVERSE, AST_LIST_UNLOCK, ast_log(), ast_mutex_destroy, ast_mutex_init, ast_mutex_lock, ast_mutex_unlock, ast_tvnow(), ast_datastore::data, and LOG_ERROR.

Referenced by lock_read(), and trylock_read().

00218 {
00219    struct ast_datastore *lock_store = ast_channel_datastore_find(chan, &lock_info, NULL);
00220    struct lock_frame *current;
00221    struct channel_lock_frame *clframe = NULL;
00222    AST_LIST_HEAD(, channel_lock_frame) *list;
00223    int res = 0;
00224    struct timespec timeout = { 0, };
00225    struct timeval now;
00226 
00227    if (!lock_store) {
00228       ast_debug(1, "Channel %s has no lock datastore, so we're allocating one.\n", chan->name);
00229       lock_store = ast_datastore_alloc(&lock_info, NULL);
00230       if (!lock_store) {
00231          ast_log(LOG_ERROR, "Unable to allocate new datastore.  No locks will be obtained.\n");
00232          return -1;
00233       }
00234 
00235       list = ast_calloc(1, sizeof(*list));
00236       if (!list) {
00237          ast_log(LOG_ERROR,
00238             "Unable to allocate datastore list head.  %sLOCK will fail.\n",
00239             trylock ? "TRY" : "");
00240          ast_datastore_free(lock_store);
00241          return -1;
00242       }
00243 
00244       lock_store->data = list;
00245       AST_LIST_HEAD_INIT(list);
00246       ast_channel_datastore_add(chan, lock_store);
00247    } else
00248       list = lock_store->data;
00249 
00250    /* Lock already exists? */
00251    AST_LIST_LOCK(&locklist);
00252    AST_LIST_TRAVERSE(&locklist, current, entries) {
00253       if (strcmp(current->name, lockname) == 0) {
00254          break;
00255       }
00256    }
00257 
00258    if (!current) {
00259       if (unloading) {
00260          /* Don't bother */
00261          AST_LIST_UNLOCK(&locklist);
00262          return -1;
00263       }
00264 
00265       /* Create new lock entry */
00266       current = ast_calloc(1, sizeof(*current) + strlen(lockname) + 1);
00267       if (!current) {
00268          AST_LIST_UNLOCK(&locklist);
00269          return -1;
00270       }
00271 
00272       strcpy(current->name, lockname); /* SAFE */
00273       if ((res = ast_mutex_init(&current->mutex))) {
00274          ast_log(LOG_ERROR, "Unable to initialize mutex: %s\n", strerror(res));
00275          ast_free(current);
00276          AST_LIST_UNLOCK(&locklist);
00277          return -1;
00278       }
00279       if ((res = ast_cond_init(&current->cond, NULL))) {
00280          ast_log(LOG_ERROR, "Unable to initialize condition variable: %s\n", strerror(res));
00281          ast_mutex_destroy(&current->mutex);
00282          ast_free(current);
00283          AST_LIST_UNLOCK(&locklist);
00284          return -1;
00285       }
00286       if (!(current->requesters = ao2_container_alloc(1, ast_channel_hash_cb, ast_channel_cmp_cb))) {
00287          ast_mutex_destroy(&current->mutex);
00288          ast_cond_destroy(&current->cond);
00289          ast_free(current);
00290          AST_LIST_UNLOCK(&locklist);
00291          return -1;
00292       }
00293       AST_LIST_INSERT_TAIL(&locklist, current, entries);
00294    }
00295    AST_LIST_UNLOCK(&locklist);
00296 
00297    /* Found lock or created one - now find or create the corresponding link in the channel */
00298    AST_LIST_LOCK(list);
00299    AST_LIST_TRAVERSE(list, clframe, list) {
00300       if (clframe->lock_frame == current) {
00301          break;
00302       }
00303    }
00304 
00305    if (!clframe) {
00306       if (unloading) {
00307          /* Don't bother */
00308          AST_LIST_UNLOCK(list);
00309          return -1;
00310       }
00311 
00312       if (!(clframe = ast_calloc(1, sizeof(*clframe)))) {
00313          ast_log(LOG_ERROR,
00314             "Unable to allocate channel lock frame.  %sLOCK will fail.\n",
00315             trylock ? "TRY" : "");
00316          AST_LIST_UNLOCK(list);
00317          return -1;
00318       }
00319 
00320       clframe->lock_frame = current;
00321       clframe->channel = chan;
00322       AST_LIST_INSERT_TAIL(list, clframe, list);
00323    }
00324    AST_LIST_UNLOCK(list);
00325 
00326    /* If we already own the lock, then we're being called recursively.
00327     * Keep track of how many times that is, because we need to unlock
00328     * the same amount, before we'll release this one.
00329     */
00330    if (current->owner == chan) {
00331       current->count++;
00332       return 0;
00333    }
00334 
00335    /* Okay, we have both frames, so now we need to try to lock.
00336     *
00337     * Locking order: always lock locklist first.  We need the
00338     * locklist lock because the broker thread counts whether
00339     * there are requesters with the locklist lock held, and we
00340     * need to hold it, so that when we send our signal, below,
00341     * to wake up the broker thread, it definitely will see that
00342     * a requester exists at that point in time.  Otherwise, we
00343     * could add to the requesters after it has already seen that
00344     * that lock is unoccupied and wait forever for another signal.
00345     */
00346    AST_LIST_LOCK(&locklist);
00347    ast_mutex_lock(&current->mutex);
00348    /* Add to requester list */
00349    ao2_link(current->requesters, chan);
00350    pthread_kill(broker_tid, SIGURG);
00351    AST_LIST_UNLOCK(&locklist);
00352 
00353    /* Wait up to three seconds from now for LOCK. */
00354    now = ast_tvnow();
00355    timeout.tv_sec = now.tv_sec + 3;
00356    timeout.tv_nsec = now.tv_usec * 1000;
00357 
00358    if (!current->owner
00359       || (!trylock
00360          && !(res = ast_cond_timedwait(&current->cond, &current->mutex, &timeout)))) {
00361       res = 0;
00362       current->owner = chan;
00363       current->count++;
00364    } else {
00365       res = -1;
00366    }
00367    /* Remove from requester list */
00368    ao2_unlink(current->requesters, chan);
00369    ast_mutex_unlock(&current->mutex);
00370 
00371    return res;
00372 }

static int load_module ( void   )  [static]

Definition at line 503 of file func_lock.c.

References ast_custom_function_register, ast_log(), AST_MODULE_LOAD_DECLINE, ast_pthread_create_background, AST_PTHREADT_NULL, lock_broker(), LOG_ERROR, and unload_module.

00504 {
00505    int res = ast_custom_function_register(&lock_function);
00506    res |= ast_custom_function_register(&trylock_function);
00507    res |= ast_custom_function_register(&unlock_function);
00508 
00509    if (ast_pthread_create_background(&broker_tid, NULL, lock_broker, NULL)) {
00510       ast_log(LOG_ERROR, "Failed to start lock broker thread. Unloading func_lock module.\n");
00511       broker_tid = AST_PTHREADT_NULL;
00512       unload_module();
00513       return AST_MODULE_LOAD_DECLINE;
00514    }
00515 
00516    return res;
00517 }

static void* lock_broker ( void *  unused  )  [static]

Definition at line 169 of file func_lock.c.

References ao2_container_count(), ast_cond_signal, AST_LIST_LOCK, AST_LIST_TRAVERSE, AST_LIST_UNLOCK, ast_mutex_lock, and ast_mutex_unlock.

Referenced by load_module().

00170 {
00171    struct lock_frame *frame;
00172    struct timespec forever = { 1000000, 0 };
00173    for (;;) {
00174       int found_requester = 0;
00175 
00176       /* Test for cancel outside of the lock */
00177       pthread_testcancel();
00178       AST_LIST_LOCK(&locklist);
00179 
00180       AST_LIST_TRAVERSE(&locklist, frame, entries) {
00181          if (ao2_container_count(frame->requesters)) {
00182             found_requester++;
00183             ast_mutex_lock(&frame->mutex);
00184             if (!frame->owner) {
00185                ast_cond_signal(&frame->cond);
00186             }
00187             ast_mutex_unlock(&frame->mutex);
00188          }
00189       }
00190 
00191       AST_LIST_UNLOCK(&locklist);
00192       pthread_testcancel();
00193 
00194       /* If there are no requesters, then wait for a signal */
00195       if (!found_requester) {
00196          nanosleep(&forever, NULL);
00197       } else {
00198          sched_yield();
00199       }
00200    }
00201    /* Not reached */
00202    return NULL;
00203 }

static void lock_fixup ( void *  data,
struct ast_channel oldchan,
struct ast_channel newchan 
) [static]

Definition at line 147 of file func_lock.c.

References ast_channel_datastore_find(), AST_LIST_HEAD, AST_LIST_LOCK, AST_LIST_TRAVERSE, AST_LIST_UNLOCK, and ast_datastore::data.

00148 {
00149    struct ast_datastore *lock_store = ast_channel_datastore_find(oldchan, &lock_info, NULL);
00150    AST_LIST_HEAD(, channel_lock_frame) *list;
00151    struct channel_lock_frame *clframe = NULL;
00152 
00153    if (!lock_store) {
00154       return;
00155    }
00156    list = lock_store->data;
00157 
00158    AST_LIST_LOCK(list);
00159    AST_LIST_TRAVERSE(list, clframe, list) {
00160       if (clframe->lock_frame->owner == oldchan) {
00161          clframe->lock_frame->owner = newchan;
00162       }
00163       /* We don't move requesters, because the thread stack is different */
00164       clframe->channel = newchan;
00165    }
00166    AST_LIST_UNLOCK(list);
00167 }

static void lock_free ( void *  data  )  [static]

Definition at line 129 of file func_lock.c.

References ast_free, AST_LIST_HEAD, AST_LIST_HEAD_DESTROY, AST_LIST_LOCK, AST_LIST_REMOVE_HEAD, and AST_LIST_UNLOCK.

00130 {
00131    AST_LIST_HEAD(, channel_lock_frame) *oldlist = data;
00132    struct channel_lock_frame *clframe;
00133    AST_LIST_LOCK(oldlist);
00134    while ((clframe = AST_LIST_REMOVE_HEAD(oldlist, list))) {
00135       /* Only unlock if we own the lock */
00136       if (clframe->channel == clframe->lock_frame->owner) {
00137          clframe->lock_frame->count = 0;
00138          clframe->lock_frame->owner = NULL;
00139       }
00140       ast_free(clframe);
00141    }
00142    AST_LIST_UNLOCK(oldlist);
00143    AST_LIST_HEAD_DESTROY(oldlist);
00144    ast_free(oldlist);
00145 }

static int lock_read ( struct ast_channel chan,
const char *  cmd,
char *  data,
char *  buf,
size_t  len 
) [static]

Definition at line 423 of file func_lock.c.

References ast_autoservice_start(), ast_autoservice_stop(), ast_copy_string(), and get_lock().

00424 {
00425    if (!chan) {
00426       return -1;
00427    }
00428    ast_autoservice_start(chan);
00429    ast_copy_string(buf, get_lock(chan, data, 0) ? "0" : "1", len);
00430    ast_autoservice_stop(chan);
00431 
00432    return 0;
00433 }

static int trylock_read ( struct ast_channel chan,
const char *  cmd,
char *  data,
char *  buf,
size_t  len 
) [static]

Definition at line 435 of file func_lock.c.

References ast_autoservice_start(), ast_autoservice_stop(), ast_copy_string(), and get_lock().

00436 {
00437    if (!chan) {
00438       return -1;
00439    }
00440    ast_autoservice_start(chan);
00441    ast_copy_string(buf, get_lock(chan, data, 1) ? "0" : "1", len);
00442    ast_autoservice_stop(chan);
00443 
00444    return 0;
00445 }

static int unload_module ( void   )  [static]

Definition at line 465 of file func_lock.c.

References ao2_container_count(), ao2_ref, ast_custom_function_unregister(), ast_free, AST_LIST_INSERT_HEAD, AST_LIST_LOCK, AST_LIST_REMOVE_HEAD, AST_LIST_UNLOCK, ast_mutex_destroy, and AST_PTHREADT_NULL.

00466 {
00467    struct lock_frame *current;
00468 
00469    /* Module flag */
00470    unloading = 1;
00471 
00472    AST_LIST_LOCK(&locklist);
00473    while ((current = AST_LIST_REMOVE_HEAD(&locklist, entries))) {
00474       /* If any locks are currently in use, then we cannot unload this module */
00475       if (current->owner || ao2_container_count(current->requesters)) {
00476          /* Put it back */
00477          AST_LIST_INSERT_HEAD(&locklist, current, entries);
00478          AST_LIST_UNLOCK(&locklist);
00479          unloading = 0;
00480          return -1;
00481       }
00482       ast_mutex_destroy(&current->mutex);
00483       ao2_ref(current->requesters, -1);
00484       ast_free(current);
00485    }
00486 
00487    /* No locks left, unregister functions */
00488    ast_custom_function_unregister(&lock_function);
00489    ast_custom_function_unregister(&trylock_function);
00490    ast_custom_function_unregister(&unlock_function);
00491 
00492    if (broker_tid != AST_PTHREADT_NULL) {
00493       pthread_cancel(broker_tid);
00494       pthread_kill(broker_tid, SIGURG);
00495       pthread_join(broker_tid, NULL);
00496    }
00497 
00498    AST_LIST_UNLOCK(&locklist);
00499 
00500    return 0;
00501 }

static int unlock_read ( struct ast_channel chan,
const char *  cmd,
char *  data,
char *  buf,
size_t  len 
) [static]

Definition at line 374 of file func_lock.c.

References ast_channel_datastore_find(), ast_copy_string(), ast_debug, AST_LIST_HEAD, AST_LIST_LOCK, AST_LIST_TRAVERSE, AST_LIST_UNLOCK, ast_log(), ast_datastore::data, and LOG_WARNING.

00375 {
00376    struct ast_datastore *lock_store;
00377    struct channel_lock_frame *clframe;
00378    AST_LIST_HEAD(, channel_lock_frame) *list;
00379 
00380    if (!chan) {
00381       return -1;
00382    }
00383 
00384    lock_store = ast_channel_datastore_find(chan, &lock_info, NULL);
00385    if (!lock_store) {
00386       ast_log(LOG_WARNING, "No datastore for dialplan locks.  Nothing was ever locked!\n");
00387       ast_copy_string(buf, "0", len);
00388       return 0;
00389    }
00390 
00391    if (!(list = lock_store->data)) {
00392       ast_debug(1, "This should NEVER happen\n");
00393       ast_copy_string(buf, "0", len);
00394       return 0;
00395    }
00396 
00397    /* Find item in the channel list */
00398    AST_LIST_LOCK(list);
00399    AST_LIST_TRAVERSE(list, clframe, list) {
00400       if (clframe->lock_frame && clframe->lock_frame->owner == chan && strcmp(clframe->lock_frame->name, data) == 0) {
00401          break;
00402       }
00403    }
00404    /* We never destroy anything until channel destruction, which will never
00405     * happen while this routine is executing, so we don't need to hold the
00406     * lock beyond this point. */
00407    AST_LIST_UNLOCK(list);
00408 
00409    if (!clframe) {
00410       /* We didn't have this lock in the first place */
00411       ast_copy_string(buf, "0", len);
00412       return 0;
00413    }
00414 
00415    if (--clframe->lock_frame->count == 0) {
00416       clframe->lock_frame->owner = NULL;
00417    }
00418 
00419    ast_copy_string(buf, "1", len);
00420    return 0;
00421 }


Variable Documentation

pthread_t broker_tid = AST_PTHREADT_NULL [static]

Definition at line 100 of file func_lock.c.

Initial value:
 {
   .name = "LOCK",
   .read = lock_read,
   .read_max = 2,
}

Definition at line 447 of file func_lock.c.

struct ast_datastore_info lock_info [static]
Initial value:
 {
   .type = "MUTEX",
   .destroy = lock_free,
   .chan_fixup = lock_fixup,
}

Definition at line 102 of file func_lock.c.

Initial value:
 {
   .name = "TRYLOCK",
   .read = trylock_read,
   .read_max = 2,
}

Definition at line 453 of file func_lock.c.

int unloading = 0 [static]

Definition at line 99 of file func_lock.c.

Initial value:
 {
   .name = "UNLOCK",
   .read = unlock_read,
   .read_max = 2,
}

Definition at line 459 of file func_lock.c.


Generated on 20 Aug 2013 for Asterisk - The Open Source Telephony Project by  doxygen 1.6.1