248 lines
6.5 KiB
C
248 lines
6.5 KiB
C
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/*
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* Asterisk -- An open source telephony toolkit.
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*
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* Copyright (C) 2007, Tilghman Lesher
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*
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* Tilghman Lesher <func_lock_2007@the-tilghman.com>
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*
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* See http://www.asterisk.org for more information about
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* the Asterisk project. Please do not directly contact
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* any of the maintainers of this project for assistance;
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* the project provides a web site, mailing lists and IRC
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* channels for your use.
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*
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* This program is free software, distributed under the terms of
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* the GNU General Public License Version 2. See the LICENSE file
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* at the top of the source tree.
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*/
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/*! \file
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*
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* \brief Dialplan mutexes
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*
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* \author Tilghman Lesher <func_lock_2007@the-tilghman.com>
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*
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* \ingroup functions
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*
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*/
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#include "asterisk.h"
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ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
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#include <stdlib.h>
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#include <stdio.h>
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#include <string.h>
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#include "asterisk/lock.h"
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#include "asterisk/file.h"
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#include "asterisk/logger.h"
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#include "asterisk/options.h"
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#include "asterisk/channel.h"
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#include "asterisk/pbx.h"
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#include "asterisk/module.h"
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#include "asterisk/options.h"
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#include "asterisk/linkedlists.h"
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AST_LIST_HEAD_STATIC(locklist, lock_frame);
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static void lock_free(void *data);
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static int unloading = 0;
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static struct ast_datastore_info lock_info = {
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.type = "MUTEX",
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.destroy = lock_free,
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};
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struct lock_frame {
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AST_LIST_ENTRY(lock_frame) entries;
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ast_mutex_t mutex;
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struct ast_channel *channel;
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char name[0];
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};
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static void lock_free(void *data)
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{
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struct lock_frame *frame = data;
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if (!frame)
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return;
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frame->channel = NULL;
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ast_mutex_unlock(&frame->mutex);
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}
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static int get_lock(struct ast_channel *chan, char *lockname, int try)
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{
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struct ast_datastore *lock_store = ast_channel_datastore_find(chan, &lock_info, NULL);
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struct lock_frame *current;
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int res;
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if (!lock_store) {
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ast_debug(1, "Channel %s has no lock datastore, so we're allocating one.\n", chan->name);
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lock_store = ast_channel_datastore_alloc(&lock_info, NULL);
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if (!lock_store) {
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ast_log(LOG_ERROR, "Unable to allocate new datastore. No locks will be obtained.\n");
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return -1;
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}
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ast_channel_datastore_add(chan, lock_store);
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}
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/* If the channel already has a lock, then free the existing lock */
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if (lock_store->data) {
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struct lock_frame *old = lock_store->data;
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old->channel = NULL;
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ast_mutex_unlock(&old->mutex);
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}
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/* Lock already exist? */
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AST_LIST_LOCK(&locklist);
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AST_LIST_TRAVERSE(&locklist, current, entries) {
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if (strcmp(current->name, lockname) == 0) {
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break;
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}
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}
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if (!current) {
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if (unloading) {
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/* Don't bother */
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AST_LIST_UNLOCK(&locklist);
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return -1;
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}
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/* Create new lock entry */
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current = ast_calloc(1, sizeof(*current) + strlen(lockname) + 1);
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if (!current) {
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AST_LIST_UNLOCK(&locklist);
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return -1;
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}
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strcpy((char *)current + sizeof(*current), lockname);
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ast_mutex_init(¤t->mutex);
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AST_LIST_INSERT_TAIL(&locklist, current, entries);
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}
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res = try ? ast_mutex_trylock(¤t->mutex) : ast_mutex_lock(¤t->mutex);
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if (res == 0) {
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lock_store->data = current;
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current->channel = chan;
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}
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AST_LIST_UNLOCK(&locklist);
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return res;
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}
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static int unlock_read(struct ast_channel *chan, const char *cmd, char *data, char *buf, size_t len)
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{
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struct ast_datastore *lock_store = ast_channel_datastore_find(chan, &lock_info, NULL);
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struct lock_frame *current;
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if (!lock_store) {
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ast_log(LOG_WARNING, "No datastore for dialplan locks. Nothing was ever locked!\n");
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ast_copy_string(buf, "0", len);
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return 0;
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}
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current = lock_store->data;
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if (!current) {
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ast_copy_string(buf, "0", len);
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return 0;
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}
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current->channel = NULL;
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ast_mutex_unlock(¤t->mutex);
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ast_copy_string(buf, "1", len);
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return 0;
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}
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static int lock_read(struct ast_channel *chan, const char *cmd, char *data, char *buf, size_t len)
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{
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ast_copy_string(buf, get_lock(chan, data, 0) ? "0" : "1", len);
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return 0;
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}
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static int trylock_read(struct ast_channel *chan, const char *cmd, char *data, char *buf, size_t len)
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{
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ast_copy_string(buf, get_lock(chan, data, 1) ? "0" : "1", len);
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return 0;
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}
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static struct ast_custom_function lock_function = {
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.name = "LOCK",
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.synopsis = "Attempt to obtain a named mutex",
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.desc =
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"Attempts to grab a named lock exclusively, and prevents other channels\n"
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"from obtaining the same lock. LOCK will wait for the lock to become\n"
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"available. Returns 1 if the lock was obtained or 0 on error.\n\n"
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"Note: to avoid the possibility of a deadlock, LOCK will only attempt to\n"
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"grab a single lock. If you have a lock already and you attempt to lock\n"
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"another name, LOCK will unlock the first name before attempting to lock\n"
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"the second name.\n",
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.syntax = "LOCK(<lockname>)",
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.read = lock_read,
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};
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static struct ast_custom_function trylock_function = {
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.name = "TRYLOCK",
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.synopsis = "Attempt to obtain a named mutex",
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.desc =
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"Attempts to grab a named lock exclusively, and prevents other channels\n"
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"from obtaining the same lock. Returns 1 if the lock was available or 0\n"
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"otherwise.\n\n"
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"Note: to avoid the possibility of a deadlock, TRYLOCK will only attempt to\n"
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"grab a single lock. If you have a lock already and you attempt to lock\n"
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"another name, TRYLOCK will unlock the first name before attempting to lock\n"
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"the second name.\n",
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.syntax = "TRYLOCK(<lockname>)",
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.read = trylock_read,
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};
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static struct ast_custom_function unlock_function = {
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.name = "UNLOCK",
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.synopsis = "Unlocks a named mutex",
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.desc =
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"Unlocks a previously locked mutex. Returns 1 if the channel had a lock\n"
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"or 0 otherwise.\n",
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.syntax = "UNLOCK()",
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.read = unlock_read,
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};
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static int unload_module(void)
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{
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struct lock_frame *current;
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/* Module flag */
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unloading = 1;
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AST_LIST_LOCK(&locklist);
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while ((current = AST_LIST_REMOVE_HEAD(&locklist, entries))) {
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/* If any locks are currently in use, then we cannot unload this module */
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if (current->channel) {
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/* Put it back */
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AST_LIST_INSERT_HEAD(&locklist, current, entries);
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AST_LIST_UNLOCK(&locklist);
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unloading = 0;
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return -1;
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}
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ast_mutex_destroy(¤t->mutex);
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ast_free(current);
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}
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/* No locks left, unregister functions */
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ast_custom_function_unregister(&lock_function);
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ast_custom_function_unregister(&trylock_function);
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ast_custom_function_unregister(&unlock_function);
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AST_LIST_UNLOCK(&locklist);
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return 0;
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}
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static int load_module(void)
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{
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int res = ast_custom_function_register(&lock_function);
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res |= ast_custom_function_register(&trylock_function);
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res |= ast_custom_function_register(&unlock_function);
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return res;
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}
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AST_MODULE_INFO_STANDARD(ASTERISK_GPL_KEY, "Dialplan mutexes");
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