asterisk/funcs/func_lock.c

543 lines
15 KiB
C

/*
* 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
*
*/
/*** MODULEINFO
<support_level>core</support_level>
***/
#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"
#include "asterisk/cli.h"
/*** DOCUMENTATION
<function name="LOCK" language="en_US">
<synopsis>
Attempt to obtain a named mutex.
</synopsis>
<syntax>
<parameter name="lockname" required="true" />
</syntax>
<description>
<para>Attempts to grab a named lock exclusively, and prevents other channels from
obtaining the same lock. LOCK will wait for the lock to become available.
Returns <literal>1</literal> if the lock was obtained or <literal>0</literal> on error.</para>
<note><para>To avoid the possibility of a deadlock, LOCK will only attempt to
obtain the lock for 3 seconds if the channel already has another lock.</para></note>
<note>
<para>If <literal>live_dangerously</literal> in <literal>asterisk.conf</literal>
is set to <literal>no</literal>, this function can only be executed from the
dialplan, and not directly from external protocols.</para>
</note>
</description>
</function>
<function name="TRYLOCK" language="en_US">
<synopsis>
Attempt to obtain a named mutex.
</synopsis>
<syntax>
<parameter name="lockname" required="true" />
</syntax>
<description>
<para>Attempts to grab a named lock exclusively, and prevents other channels
from obtaining the same lock. Returns <literal>1</literal> if the lock was
available or <literal>0</literal> otherwise.</para>
<note>
<para>If <literal>live_dangerously</literal> in <literal>asterisk.conf</literal>
is set to <literal>no</literal>, this function can only be executed from the
dialplan, and not directly from external protocols.</para>
</note>
</description>
</function>
<function name="UNLOCK" language="en_US">
<synopsis>
Unlocks a named mutex.
</synopsis>
<syntax>
<parameter name="lockname" required="true" />
</syntax>
<description>
<para>Unlocks a previously locked mutex. Returns <literal>1</literal> if the channel
had a lock or <literal>0</literal> otherwise.</para>
<note><para>It is generally unnecessary to unlock in a hangup routine, as any locks
held are automatically freed when the channel is destroyed.</para></note>
<note>
<para>If <literal>live_dangerously</literal> in <literal>asterisk.conf</literal>
is set to <literal>no</literal>, this function can only be executed from the
dialplan, and not directly from external protocols.</para>
</note>
</description>
</function>
***/
static AST_LIST_HEAD_STATIC(locklist, lock_frame);
static void lock_free(void *data);
static void lock_fixup(void *data, struct ast_channel *oldchan, struct ast_channel *newchan);
static int unloading = 0;
static const struct ast_datastore_info lock_info = {
.type = "MUTEX",
.destroy = lock_free,
.chan_fixup = lock_fixup,
};
struct lock_frame {
AST_LIST_ENTRY(lock_frame) entries;
ast_mutex_t mutex;
ast_cond_t cond;
/*! count is needed so if a recursive mutex exits early, we know how many times to unlock it. */
unsigned int count;
/*! Count of waiting of requesters for the named lock */
unsigned int requesters;
/*! who owns us */
struct ast_channel *owner;
/*! 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->owner) {
ast_mutex_lock(&clframe->lock_frame->mutex);
clframe->lock_frame->count = 0;
clframe->lock_frame->owner = NULL;
ast_cond_signal(&clframe->lock_frame->cond);
ast_mutex_unlock(&clframe->lock_frame->mutex);
}
ast_free(clframe);
}
AST_LIST_UNLOCK(oldlist);
AST_LIST_HEAD_DESTROY(oldlist);
ast_free(oldlist);
ast_module_unref(ast_module_info->self);
}
static void lock_fixup(void *data, struct ast_channel *oldchan, struct ast_channel *newchan)
{
struct ast_datastore *lock_store = ast_channel_datastore_find(oldchan, &lock_info, NULL);
AST_LIST_HEAD(, channel_lock_frame) *list;
struct channel_lock_frame *clframe = NULL;
if (!lock_store) {
return;
}
list = lock_store->data;
AST_LIST_LOCK(list);
AST_LIST_TRAVERSE(list, clframe, list) {
if (clframe->lock_frame->owner == oldchan) {
clframe->lock_frame->owner = newchan;
}
clframe->channel = newchan;
}
AST_LIST_UNLOCK(list);
}
static int get_lock(struct ast_channel *chan, char *lockname, int trylock)
{
struct ast_datastore *lock_store = ast_channel_datastore_find(chan, &lock_info, NULL);
struct lock_frame *current;
struct channel_lock_frame *clframe = NULL;
AST_LIST_HEAD(, channel_lock_frame) *list;
int res = 0;
struct timespec timeout = { 0, };
struct timeval now;
if (!lock_store) {
if (unloading) {
ast_log(LOG_ERROR, "%sLOCK has no datastore and func_lock is unloading, failing.\n",
trylock ? "TRY" : "");
return -1;
}
lock_store = ast_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",
trylock ? "TRY" : "");
ast_datastore_free(lock_store);
return -1;
}
lock_store->data = list;
AST_LIST_HEAD_INIT(list);
ast_channel_datastore_add(chan, lock_store);
/* We cannot unload until this channel has released the lock_store */
ast_module_ref(ast_module_info->self);
} 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) {
ast_log(LOG_ERROR,
"Lock doesn't exist whilst unloading. %sLOCK will fail.\n",
trylock ? "TRY" : "");
/* 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(current->name, lockname); /* SAFE */
if ((res = ast_mutex_init(&current->mutex))) {
ast_log(LOG_ERROR, "Unable to initialize mutex: %s\n", strerror(res));
ast_free(current);
AST_LIST_UNLOCK(&locklist);
return -1;
}
if ((res = ast_cond_init(&current->cond, NULL))) {
ast_log(LOG_ERROR, "Unable to initialize condition variable: %s\n", strerror(res));
ast_mutex_destroy(&current->mutex);
ast_free(current);
AST_LIST_UNLOCK(&locklist);
return -1;
}
AST_LIST_INSERT_TAIL(&locklist, current, entries);
}
/* Add to requester list */
ast_mutex_lock(&current->mutex);
current->requesters++;
ast_mutex_unlock(&current->mutex);
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) {
break;
}
}
if (!clframe) {
if (unloading) {
ast_log(LOG_ERROR,
"Busy unloading. %sLOCK will fail.\n",
trylock ? "TRY" : "");
/* Don't bother */
ast_mutex_lock(&current->mutex);
current->requesters--;
ast_mutex_unlock(&current->mutex);
AST_LIST_UNLOCK(list);
return -1;
}
if (!(clframe = ast_calloc(1, sizeof(*clframe)))) {
ast_log(LOG_ERROR,
"Unable to allocate channel lock frame. %sLOCK will fail.\n",
trylock ? "TRY" : "");
ast_mutex_lock(&current->mutex);
current->requesters--;
ast_mutex_unlock(&current->mutex);
AST_LIST_UNLOCK(list);
return -1;
}
clframe->lock_frame = current;
clframe->channel = chan;
AST_LIST_INSERT_TAIL(list, clframe, list);
}
AST_LIST_UNLOCK(list);
/* If we already own the lock, then we're being called recursively.
* Keep track of how many times that is, because we need to unlock
* the same amount, before we'll release this one.
*/
if (current->owner == chan) {
/* We're not a requester, we already have it */
ast_mutex_lock(&current->mutex);
current->requesters--;
ast_mutex_unlock(&current->mutex);
current->count++;
return 0;
}
/* Wait up to three seconds from now for LOCK. */
now = ast_tvnow();
timeout.tv_sec = now.tv_sec + 3;
timeout.tv_nsec = now.tv_usec * 1000;
ast_mutex_lock(&current->mutex);
res = 0;
while (!trylock && !res && current->owner) {
res = ast_cond_timedwait(&current->cond, &current->mutex, &timeout);
}
if (current->owner) {
/* timeout;
* trylock; or
* cond_timedwait failed.
*
* either way, we fail to obtain the lock.
*/
res = -1;
} else {
current->owner = chan;
current->count++;
res = 0;
}
/* Remove from requester list */
current->requesters--;
if (res && unloading)
ast_cond_signal(&current->cond);
ast_mutex_unlock(&current->mutex);
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;
struct channel_lock_frame *clframe;
AST_LIST_HEAD(, channel_lock_frame) *list;
if (!chan) {
return -1;
}
lock_store = ast_channel_datastore_find(chan, &lock_info, NULL);
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->owner == 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;
}
if (--clframe->lock_frame->count == 0) {
ast_mutex_lock(&clframe->lock_frame->mutex);
clframe->lock_frame->owner = NULL;
ast_cond_signal(&clframe->lock_frame->cond);
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) {
return -1;
}
ast_autoservice_start(chan);
ast_copy_string(buf, get_lock(chan, data, 0) ? "0" : "1", len);
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) {
return -1;
}
ast_autoservice_start(chan);
ast_copy_string(buf, get_lock(chan, data, 1) ? "0" : "1", len);
ast_autoservice_stop(chan);
return 0;
}
static char *handle_cli_locks_show(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a)
{
int c = 0;
struct lock_frame* current;
switch (cmd) {
case CLI_INIT:
e->command = "dialplan locks show";
e->usage =
"Usage: dialplan locks show\n"
" List all locks known to func_lock, along with their current status.\n";
return NULL;
case CLI_GENERATE:
return NULL;
}
ast_cli(a->fd, "func_lock locks:\n");
ast_cli(a->fd, "%-40s Requesters Owner\n", "Name");
AST_LIST_LOCK(&locklist);
AST_LIST_TRAVERSE(&locklist, current, entries) {
ast_mutex_lock(&current->mutex);
ast_cli(a->fd, "%-40s %-10d %s\n", current->name, current->requesters,
current->owner ? ast_channel_name(current->owner) : "(unlocked)");
ast_mutex_unlock(&current->mutex);
c++;
}
AST_LIST_UNLOCK(&locklist);
ast_cli(a->fd, "%d total locks listed.\n", c);
return 0;
}
static struct ast_custom_function lock_function = {
.name = "LOCK",
.read = lock_read,
.read_max = 2,
};
static struct ast_custom_function trylock_function = {
.name = "TRYLOCK",
.read = trylock_read,
.read_max = 2,
};
static struct ast_custom_function unlock_function = {
.name = "UNLOCK",
.read = unlock_read,
.read_max = 2,
};
static struct ast_cli_entry cli_locks_show = AST_CLI_DEFINE(handle_cli_locks_show, "List func_lock locks.");
static int unload_module(void)
{
struct lock_frame *current;
/* Module flag */
unloading = 1;
/* Make it impossible for new requesters to be added
* NOTE: channels could already be in get_lock() */
ast_custom_function_unregister(&lock_function);
ast_custom_function_unregister(&trylock_function);
ast_cli_unregister(&cli_locks_show);
AST_LIST_LOCK(&locklist);
while ((current = AST_LIST_REMOVE_HEAD(&locklist, entries))) {
int warned = 0;
ast_mutex_lock(&current->mutex);
while (current->owner || current->requesters) {
if (!warned) {
ast_log(LOG_WARNING, "Waiting for %d requesters for %s lock %s.\n",
current->requesters, current->owner ? "locked" : "unlocked",
current->name);
warned = 1;
}
/* either the mutex is locked, or other parties are currently in get_lock,
* we need to wait for all of those to clear first */
ast_cond_wait(&current->cond, &current->mutex);
}
ast_mutex_unlock(&current->mutex);
/* At this point we know:
* 1. the lock has been released,
* 2. there are no requesters (nor should any be able to sneak in).
*/
ast_mutex_destroy(&current->mutex);
ast_cond_destroy(&current->cond);
ast_free(current);
}
AST_LIST_UNLOCK(&locklist);
AST_LIST_HEAD_DESTROY(&locklist);
/* At this point we can safely stop access to UNLOCK */
ast_custom_function_unregister(&unlock_function);
return 0;
}
static int load_module(void)
{
int res = ast_custom_function_register_escalating(&lock_function, AST_CFE_READ);
res |= ast_custom_function_register_escalating(&trylock_function, AST_CFE_READ);
res |= ast_custom_function_register_escalating(&unlock_function, AST_CFE_READ);
res |= ast_cli_register(&cli_locks_show);
return res;
}
AST_MODULE_INFO_STANDARD(ASTERISK_GPL_KEY, "Dialplan mutexes");