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-rw-r--r--trunk/funcs/func_lock.c350
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diff --git a/trunk/funcs/func_lock.c b/trunk/funcs/func_lock.c
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+/*
+ * Asterisk -- An open source telephony toolkit.
+ *
+ * Copyright (C) 2007, Tilghman Lesher
+ *
+ * Tilghman Lesher <func_lock_2007@the-tilghman.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 Dialplan mutexes
+ *
+ * \author Tilghman Lesher <func_lock_2007@the-tilghman.com>
+ *
+ * \ingroup functions
+ *
+ */
+
+#include "asterisk.h"
+
+ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
+
+#include "asterisk/lock.h"
+#include "asterisk/file.h"
+#include "asterisk/channel.h"
+#include "asterisk/pbx.h"
+#include "asterisk/module.h"
+#include "asterisk/linkedlists.h"
+
+AST_LIST_HEAD_STATIC(locklist, lock_frame);
+
+static void lock_free(void *data);
+static int unloading = 0;
+
+static struct ast_datastore_info lock_info = {
+ .type = "MUTEX",
+ .destroy = lock_free,
+};
+
+struct lock_frame {
+ AST_LIST_ENTRY(lock_frame) entries;
+ ast_mutex_t mutex;
+ /*! count is needed so if a recursive mutex exits early, we know how many times to unlock it. */
+ unsigned int count;
+ /*! who owns us */
+ struct ast_channel *channel;
+ /*! name of the lock */
+ char name[0];
+};
+
+struct channel_lock_frame {
+ AST_LIST_ENTRY(channel_lock_frame) list;
+ /*! Need to save channel pointer here, because during destruction, we won't have it. */
+ struct ast_channel *channel;
+ struct lock_frame *lock_frame;
+};
+
+static void lock_free(void *data)
+{
+ AST_LIST_HEAD(, channel_lock_frame) *oldlist = data;
+ struct channel_lock_frame *clframe;
+ AST_LIST_LOCK(oldlist);
+ while ((clframe = AST_LIST_REMOVE_HEAD(oldlist, list))) {
+ /* Only unlock if we own the lock */
+ if (clframe->channel == clframe->lock_frame->channel) {
+ clframe->lock_frame->channel = NULL;
+ while (clframe->lock_frame->count > 0) {
+ clframe->lock_frame->count--;
+ ast_mutex_unlock(&clframe->lock_frame->mutex);
+ }
+ }
+ ast_free(clframe);
+ }
+ AST_LIST_UNLOCK(oldlist);
+ AST_LIST_HEAD_DESTROY(oldlist);
+ ast_free(oldlist);
+}
+
+static int get_lock(struct ast_channel *chan, char *lockname, int try)
+{
+ struct ast_datastore *lock_store = ast_channel_datastore_find(chan, &lock_info, NULL);
+ struct lock_frame *current;
+ struct channel_lock_frame *clframe = NULL, *save_clframe = NULL;
+ AST_LIST_HEAD(, channel_lock_frame) *list;
+ int res, count_channel_locks = 0;
+
+ if (!lock_store) {
+ ast_debug(1, "Channel %s has no lock datastore, so we're allocating one.\n", chan->name);
+ lock_store = ast_channel_datastore_alloc(&lock_info, NULL);
+ if (!lock_store) {
+ ast_log(LOG_ERROR, "Unable to allocate new datastore. No locks will be obtained.\n");
+ return -1;
+ }
+
+ list = ast_calloc(1, sizeof(*list));
+ if (!list) {
+ ast_log(LOG_ERROR, "Unable to allocate datastore list head. %sLOCK will fail.\n", try ? "TRY" : "");
+ ast_channel_datastore_free(lock_store);
+ return -1;
+ }
+
+ lock_store->data = list;
+ AST_LIST_HEAD_INIT(list);
+ ast_channel_datastore_add(chan, lock_store);
+ } else
+ list = lock_store->data;
+
+ /* Lock already exists? */
+ AST_LIST_LOCK(&locklist);
+ AST_LIST_TRAVERSE(&locklist, current, entries) {
+ if (strcmp(current->name, lockname) == 0) {
+ break;
+ }
+ }
+
+ if (!current) {
+ if (unloading) {
+ /* Don't bother */
+ AST_LIST_UNLOCK(&locklist);
+ return -1;
+ }
+
+ /* Create new lock entry */
+ current = ast_calloc(1, sizeof(*current) + strlen(lockname) + 1);
+ if (!current) {
+ AST_LIST_UNLOCK(&locklist);
+ return -1;
+ }
+
+ strcpy((char *)current + sizeof(*current), lockname);
+ ast_mutex_init(&current->mutex);
+ AST_LIST_INSERT_TAIL(&locklist, current, entries);
+ }
+ AST_LIST_UNLOCK(&locklist);
+
+ /* Found lock or created one - now find or create the corresponding link in the channel */
+ AST_LIST_LOCK(list);
+ AST_LIST_TRAVERSE(list, clframe, list) {
+ if (clframe->lock_frame == current)
+ save_clframe = clframe;
+
+ /* Only count mutexes that we currently hold */
+ if (clframe->lock_frame->channel == chan)
+ count_channel_locks++;
+ }
+
+ if (save_clframe) {
+ clframe = save_clframe;
+ } else {
+ if (unloading) {
+ /* Don't bother */
+ AST_LIST_UNLOCK(list);
+ return -1;
+ }
+
+ clframe = ast_calloc(1, sizeof(*clframe));
+ if (!clframe) {
+ ast_log(LOG_ERROR, "Unable to allocate channel lock frame. %sLOCK will fail.\n", try ? "TRY" : "");
+ AST_LIST_UNLOCK(list);
+ return -1;
+ }
+
+ clframe->lock_frame = current;
+ clframe->channel = chan;
+ /* Count the lock just created */
+ count_channel_locks++;
+ AST_LIST_INSERT_TAIL(list, clframe, list);
+ }
+ AST_LIST_UNLOCK(list);
+
+ /* Okay, we have both frames, so now we need to try to lock the mutex. */
+ if (count_channel_locks > 1) {
+ struct timeval start = ast_tvnow();
+ for (;;) {
+ if ((res = ast_mutex_trylock(&current->mutex)) == 0)
+ break;
+ if (ast_tvdiff_ms(ast_tvnow(), start) > 3000)
+ break; /* bail after 3 seconds of waiting */
+ usleep(1);
+ }
+ } else {
+ /* If the channel doesn't have any locks so far, then there's no possible deadlock. */
+ res = try ? ast_mutex_trylock(&current->mutex) : ast_mutex_lock(&current->mutex);
+ }
+
+ if (res == 0) {
+ current->count++;
+ current->channel = chan;
+ }
+
+ return res;
+}
+
+static int unlock_read(struct ast_channel *chan, const char *cmd, char *data, char *buf, size_t len)
+{
+ struct ast_datastore *lock_store = ast_channel_datastore_find(chan, &lock_info, NULL);
+ struct channel_lock_frame *clframe;
+ AST_LIST_HEAD(, channel_lock_frame) *list;
+
+ if (!lock_store) {
+ ast_log(LOG_WARNING, "No datastore for dialplan locks. Nothing was ever locked!\n");
+ ast_copy_string(buf, "0", len);
+ return 0;
+ }
+
+ if (!(list = lock_store->data)) {
+ ast_debug(1, "This should NEVER happen\n");
+ ast_copy_string(buf, "0", len);
+ return 0;
+ }
+
+ /* Find item in the channel list */
+ AST_LIST_LOCK(list);
+ AST_LIST_TRAVERSE(list, clframe, list) {
+ if (clframe->lock_frame && clframe->lock_frame->channel == chan && strcmp(clframe->lock_frame->name, data) == 0) {
+ break;
+ }
+ }
+ /* We never destroy anything until channel destruction, which will never
+ * happen while this routine is executing, so we don't need to hold the
+ * lock beyond this point. */
+ AST_LIST_UNLOCK(list);
+
+ if (!clframe) {
+ /* We didn't have this lock in the first place */
+ ast_copy_string(buf, "0", len);
+ return 0;
+ }
+
+ /* Decrement before we release, because if a channel is waiting on the
+ * mutex, there's otherwise a race to alter count. */
+ clframe->lock_frame->count--;
+ /* If we get another lock, this one shouldn't count against us for deadlock avoidance. */
+ clframe->lock_frame->channel = NULL;
+ ast_mutex_unlock(&clframe->lock_frame->mutex);
+
+ ast_copy_string(buf, "1", len);
+ return 0;
+}
+
+static int lock_read(struct ast_channel *chan, const char *cmd, char *data, char *buf, size_t len)
+{
+ if (chan)
+ ast_autoservice_start(chan);
+
+ ast_copy_string(buf, get_lock(chan, data, 0) ? "0" : "1", len);
+
+ if (chan)
+ ast_autoservice_stop(chan);
+
+ return 0;
+}
+
+static int trylock_read(struct ast_channel *chan, const char *cmd, char *data, char *buf, size_t len)
+{
+ if (chan)
+ ast_autoservice_start(chan);
+
+ ast_copy_string(buf, get_lock(chan, data, 1) ? "0" : "1", len);
+
+ if (chan)
+ ast_autoservice_stop(chan);
+
+ return 0;
+}
+
+static struct ast_custom_function lock_function = {
+ .name = "LOCK",
+ .synopsis = "Attempt to obtain a named mutex",
+ .desc =
+"Attempts to grab a named lock exclusively, and prevents other channels from\n"
+"obtaining the same lock. LOCK will wait for the lock to become available.\n"
+"Returns 1 if the lock was obtained or 0 on error.\n\n"
+"Note: to avoid the possibility of a deadlock, LOCK will only attempt to\n"
+"obtain the lock for 3 seconds if the channel already has another lock.\n",
+ .syntax = "LOCK(<lockname>)",
+ .read = lock_read,
+};
+
+static struct ast_custom_function trylock_function = {
+ .name = "TRYLOCK",
+ .synopsis = "Attempt to obtain a named mutex",
+ .desc =
+"Attempts to grab a named lock exclusively, and prevents other channels\n"
+"from obtaining the same lock. Returns 1 if the lock was available or 0\n"
+"otherwise.\n",
+ .syntax = "TRYLOCK(<lockname>)",
+ .read = trylock_read,
+};
+
+static struct ast_custom_function unlock_function = {
+ .name = "UNLOCK",
+ .synopsis = "Unlocks a named mutex",
+ .desc =
+"Unlocks a previously locked mutex. Note that it is generally unnecessary to\n"
+"unlock in a hangup routine, as any locks held are automatically freed when the\n"
+"channel is destroyed. Returns 1 if the channel had a lock or 0 otherwise.\n",
+ .syntax = "UNLOCK(<lockname>)",
+ .read = unlock_read,
+};
+
+static int unload_module(void)
+{
+ struct lock_frame *current;
+
+ /* Module flag */
+ unloading = 1;
+
+ AST_LIST_LOCK(&locklist);
+ while ((current = AST_LIST_REMOVE_HEAD(&locklist, entries))) {
+ /* If any locks are currently in use, then we cannot unload this module */
+ if (current->channel) {
+ /* Put it back */
+ AST_LIST_INSERT_HEAD(&locklist, current, entries);
+ AST_LIST_UNLOCK(&locklist);
+ unloading = 0;
+ return -1;
+ }
+ ast_mutex_destroy(&current->mutex);
+ ast_free(current);
+ }
+
+ /* No locks left, unregister functions */
+ ast_custom_function_unregister(&lock_function);
+ ast_custom_function_unregister(&trylock_function);
+ ast_custom_function_unregister(&unlock_function);
+
+ AST_LIST_UNLOCK(&locklist);
+ return 0;
+}
+
+static int load_module(void)
+{
+ int res = ast_custom_function_register(&lock_function);
+ res |= ast_custom_function_register(&trylock_function);
+ res |= ast_custom_function_register(&unlock_function);
+ return res;
+}
+
+AST_MODULE_INFO_STANDARD(ASTERISK_GPL_KEY, "Dialplan mutexes");