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"
#include "asterisk/cli.h"

Include dependency graph for func_lock.c:

Go to the source code of this file.

Data Structures
struct	channel_lock_frame
struct	lock_frame
struct	locklist

Functions
static void	__reg_module (void)
static void	__unreg_module (void)
struct ast_module *	AST_MODULE_SELF_SYM (void)
static int	get_lock (struct ast_channel *chan, char *lockname, int trylock)
static char *	handle_cli_locks_show (struct ast_cli_entry *e, int cmd, struct ast_cli_args *a)
static int	load_module (void)
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 struct ast_module_info	__mod_info = { .name = AST_MODULE, .flags = AST_MODFLAG_LOAD_ORDER , .description = "Dialplan mutexes" , .key = ASTERISK_GPL_KEY , .buildopt_sum = AST_BUILDOPT_SUM, .load = load_module, .unload = unload_module, .load_pri = AST_MODPRI_DEFAULT, .support_level = AST_MODULE_SUPPORT_CORE, }
static const struct ast_module_info *	ast_module_info = &__mod_info
static struct ast_cli_entry	cli_locks_show = { .handler = handle_cli_locks_show , .summary = "List func_lock locks." ,}
static struct ast_custom_function	lock_function
static const struct ast_datastore_info	lock_info
static struct locklist	locklist = AST_LIST_HEAD_INIT_VALUE
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_.nosp@m.lock.nosp@m._2007.nosp@m.@the.nosp@m.-tilg.nosp@m.hman.nosp@m..com

Definition in file func_lock.c.

Function Documentation

__reg_module()

static void __reg_module ( void  )

static

Definition at line 563 of file func_lock.c.

__unreg_module()

static void __unreg_module ( void  )

static

Definition at line 563 of file func_lock.c.

AST_MODULE_SELF_SYM()

struct ast_module * AST_MODULE_SELF_SYM

(

void

)

Definition at line 563 of file func_lock.c.

get_lock()

static int get_lock ( struct ast_channel *  chan, char *  lockname, int  trylock  )

static

Definition at line 207 of file func_lock.c.

{
    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;
}

References ast_calloc, ast_channel_datastore_add(), ast_channel_datastore_find(), ast_cond_init, ast_cond_signal, ast_cond_timedwait, ast_datastore_alloc, ast_datastore_free(), 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_module_ref, ast_mutex_destroy, ast_mutex_init, ast_mutex_lock, ast_mutex_unlock, ast_tvnow(), channel_lock_frame::channel, current, ast_datastore::data, channel_lock_frame::list, channel_lock_frame::lock_frame, lock_info, LOG_ERROR, NULL, ast_module_info::self, and unloading.

Referenced by lock_read(), and trylock_read().

handle_cli_locks_show()

static char * handle_cli_locks_show ( struct ast_cli_entry *  e, int  cmd, struct ast_cli_args *  a  )

static

Definition at line 455 of file func_lock.c.

{
    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;
}

References a, ast_channel_name(), ast_cli(), AST_LIST_LOCK, AST_LIST_TRAVERSE, AST_LIST_UNLOCK, ast_mutex_lock, ast_mutex_unlock, c, CLI_GENERATE, CLI_INIT, ast_cli_entry::command, current, lock_frame::entries, test_val::name, NULL, and ast_cli_entry::usage.

load_module()

static int load_module ( void  )

static

Definition at line 553 of file func_lock.c.

{
    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;
}

References AST_CFE_READ, ast_cli_register, ast_custom_function_register_escalating, cli_locks_show, lock_function, trylock_function, and unlock_function.

lock_fixup()

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

static

Definition at line 186 of file func_lock.c.

{
    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);
}

References ast_channel_datastore_find(), AST_LIST_HEAD, AST_LIST_LOCK, AST_LIST_TRAVERSE, AST_LIST_UNLOCK, channel_lock_frame::channel, ast_datastore::data, channel_lock_frame::list, channel_lock_frame::lock_frame, lock_info, NULL, and lock_frame::owner.

lock_free()

static void lock_free ( void *  data )

static

Definition at line 163 of file func_lock.c.

{
    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);
}

References ast_cond_signal, ast_free, AST_LIST_HEAD, AST_LIST_HEAD_DESTROY, AST_LIST_LOCK, AST_LIST_REMOVE_HEAD, AST_LIST_UNLOCK, ast_module_unref, ast_mutex_lock, ast_mutex_unlock, channel_lock_frame::channel, lock_frame::cond, lock_frame::count, channel_lock_frame::list, channel_lock_frame::lock_frame, lock_frame::mutex, NULL, lock_frame::owner, and ast_module_info::self.

lock_read()

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

static

Definition at line 431 of file func_lock.c.

{
    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;
}

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

trylock_read()

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

static

Definition at line 443 of file func_lock.c.

{
    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;
}

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

unload_module()

static int unload_module ( void  )

static

Definition at line 506 of file func_lock.c.

{
    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;
}

References ast_cli_unregister(), ast_cond_destroy, ast_cond_wait, ast_custom_function_unregister(), ast_free, AST_LIST_HEAD_DESTROY, AST_LIST_LOCK, AST_LIST_REMOVE_HEAD, AST_LIST_UNLOCK, ast_log, ast_mutex_destroy, ast_mutex_lock, ast_mutex_unlock, cli_locks_show, current, lock_frame::entries, lock_function, LOG_WARNING, trylock_function, unloading, and unlock_function.

unlock_read()

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

static

Definition at line 379 of file func_lock.c.

{
    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;
}

References ast_channel_datastore_find(), ast_cond_signal, ast_copy_string(), ast_debug, AST_LIST_HEAD, AST_LIST_LOCK, AST_LIST_TRAVERSE, AST_LIST_UNLOCK, ast_log, ast_mutex_lock, ast_mutex_unlock, buf, lock_frame::cond, lock_frame::count, ast_datastore::data, len(), channel_lock_frame::list, channel_lock_frame::lock_frame, lock_info, LOG_WARNING, lock_frame::mutex, lock_frame::name, NULL, and lock_frame::owner.

Variable Documentation

__mod_info

struct ast_module_info __mod_info = { .name = AST_MODULE, .flags = AST_MODFLAG_LOAD_ORDER , .description = "Dialplan mutexes" , .key = ASTERISK_GPL_KEY , .buildopt_sum = AST_BUILDOPT_SUM, .load = load_module, .unload = unload_module, .load_pri = AST_MODPRI_DEFAULT, .support_level = AST_MODULE_SUPPORT_CORE, }

static

Definition at line 563 of file func_lock.c.

ast_module_info

const struct ast_module_info* ast_module_info = &__mod_info

static

Definition at line 563 of file func_lock.c.

cli_locks_show

struct ast_cli_entry cli_locks_show = { .handler = handle_cli_locks_show , .summary = "List func_lock locks." ,}

static

Definition at line 504 of file func_lock.c.

Referenced by load_module(), and unload_module().

lock_function

struct ast_custom_function lock_function

static

Initial value:

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

Definition at line 486 of file func_lock.c.

                                                  {
    .name = "LOCK",
    .read = lock_read,
    .read_max = 2,
};

Referenced by load_module(), and unload_module().

lock_info

const struct ast_datastore_info lock_info

static

Initial value:

= {
    .type = "MUTEX",
    .destroy = lock_free,
    .chan_fixup = lock_fixup,
}

Definition at line 136 of file func_lock.c.

                                                   {
    .type = "MUTEX",
    .destroy = lock_free,
    .chan_fixup = lock_fixup,
};

Referenced by dummy_start(), get_lock(), lock_fixup(), and unlock_read().

locklist

struct locklist locklist = AST_LIST_HEAD_INIT_VALUE

static

trylock_function

struct ast_custom_function trylock_function

static

Initial value:

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

Definition at line 492 of file func_lock.c.

                                                     {
    .name = "TRYLOCK",
    .read = trylock_read,
    .read_max = 2,
};

Referenced by load_module(), and unload_module().

unloading

int unloading = 0

static

Definition at line 134 of file func_lock.c.

Referenced by get_lock(), and unload_module().

unlock_function

struct ast_custom_function unlock_function

static

Initial value:

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

Definition at line 498 of file func_lock.c.

                                                    {
    .name = "UNLOCK",
    .read = unlock_read,
    .read_max = 2,
};

Referenced by load_module(), and unload_module().