taskprocessor.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 2007-2013, Digium, Inc.
 *
 * Dwayne M. Hubbard <[email protected]>
 *
 * 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 Maintain a container of uniquely-named taskprocessor threads that can be shared across modules.
 *
 * \author Dwayne Hubbard <[email protected]>
 */

/*** MODULEINFO
   <support_level>core</support_level>
 ***/

#include "asterisk.h"

#include "asterisk/_private.h"
#include "asterisk/module.h"
#include "asterisk/time.h"
#include "asterisk/astobj2.h"
#include "asterisk/cli.h"
#include "asterisk/taskprocessor.h"
#include "asterisk/sem.h"

/*!
 * \brief tps_task structure is queued to a taskprocessor
 *
 * tps_tasks are processed in FIFO order and freed by the taskprocessing
 * thread after the task handler returns.  The callback function that is assigned
 * to the execute() function pointer is responsible for releasing datap resources if necessary.
 */
struct tps_task {
   /*! \brief The execute() task callback function pointer */
   union {
      int (*execute)(void *datap);
      int (*execute_local)(struct ast_taskprocessor_local *local);
   } callback;
   /*! \brief The data pointer for the task execute() function */
   void *datap;
   /*! \brief AST_LIST_ENTRY overhead */
   AST_LIST_ENTRY(tps_task) list;
   unsigned int wants_local:1;
};

/*! \brief tps_taskprocessor_stats maintain statistics for a taskprocessor. */
struct tps_taskprocessor_stats {
   /*! \brief This is the maximum number of tasks queued at any one time */
   unsigned long max_qsize;
   /*! \brief This is the current number of tasks processed */
   unsigned long _tasks_processed_count;
};

/*! \brief A ast_taskprocessor structure is a singleton by name */
struct ast_taskprocessor {
   /*! \brief Taskprocessor statistics */
   struct tps_taskprocessor_stats stats;
   void *local_data;
   /*! \brief Taskprocessor current queue size */
   long tps_queue_size;
   /*! \brief Taskprocessor low water clear alert level */
   long tps_queue_low;
   /*! \brief Taskprocessor high water alert trigger level */
   long tps_queue_high;
   /*! \brief Taskprocessor queue */
   AST_LIST_HEAD_NOLOCK(tps_queue, tps_task) tps_queue;
   struct ast_taskprocessor_listener *listener;
   /*! Current thread executing the tasks */
   pthread_t thread;
   /*! Indicates if the taskprocessor is currently executing a task */
   unsigned int executing:1;
   /*! Indicates that a high water warning has been issued on this task processor */
   unsigned int high_water_warned:1;
   /*! Indicates that a high water alert is active on this taskprocessor */
   unsigned int high_water_alert:1;
   /*! Indicates if the taskprocessor is currently suspended */
   unsigned int suspended:1;
   /*! \brief Anything before the first '/' in the name (if there is one) */
   char *subsystem;
   /*! \brief Friendly name of the taskprocessor.
    * Subsystem is appended after the name's NULL terminator.
    */
   char name[0];
};

/*!
 * \brief A listener for taskprocessors
 *
 * \since 12.0.0
 *
 * When a taskprocessor's state changes, the listener
 * is notified of the change. This allows for tasks
 * to be addressed in whatever way is appropriate for
 * the module using the taskprocessor.
 */
struct ast_taskprocessor_listener {
   /*! The callbacks the taskprocessor calls into to notify of state changes */
   const struct ast_taskprocessor_listener_callbacks *callbacks;
   /*! The taskprocessor that the listener is listening to */
   struct ast_taskprocessor *tps;
   /*! Data private to the listener */
   void *user_data;
};

/*!
 * Keep track of which subsystems are in alert
 * and how many of their taskprocessors are overloaded.
 */
struct subsystem_alert {
   unsigned int alert_count;
   char subsystem[0];
};
static AST_VECTOR_RW(subsystem_alert_vector, struct subsystem_alert *) overloaded_subsystems;

#ifdef LOW_MEMORY
#define TPS_MAX_BUCKETS 61
#else
/*! \brief Number of buckets in the tps_singletons container. */
#define TPS_MAX_BUCKETS 1567
#endif

/*! \brief tps_singletons is the astobj2 container for taskprocessor singletons */
static struct ao2_container *tps_singletons;

/*! \brief CLI <example>taskprocessor ping &lt;blah&gt;</example> operation requires a ping condition */
static ast_cond_t cli_ping_cond;

/*! \brief CLI <example>taskprocessor ping &lt;blah&gt;</example> operation requires a ping condition lock */
AST_MUTEX_DEFINE_STATIC(cli_ping_cond_lock);

/*! \brief The astobj2 hash callback for taskprocessors */
static int tps_hash_cb(const void *obj, const int flags);
/*! \brief The astobj2 compare callback for taskprocessors */
static int tps_cmp_cb(void *obj, void *arg, int flags);

/*! \brief CLI <example>taskprocessor ping &lt;blah&gt;</example> handler function */
static int tps_ping_handler(void *datap);

static char *cli_tps_ping(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a);
static char *cli_tps_report(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a);
static char *cli_subsystem_alert_report(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a);
static char *cli_tps_reset_stats(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a);
static char *cli_tps_reset_stats_all(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a);

static struct ast_cli_entry taskprocessor_clis[] = {
   AST_CLI_DEFINE(cli_tps_ping, "Ping a named task processor"),
   AST_CLI_DEFINE(cli_tps_report, "List instantiated task processors and statistics"),
   AST_CLI_DEFINE(cli_subsystem_alert_report, "List task processor subsystems in alert"),
   AST_CLI_DEFINE(cli_tps_reset_stats, "Reset a named task processor's stats"),
   AST_CLI_DEFINE(cli_tps_reset_stats_all, "Reset all task processors' stats"),
};

struct default_taskprocessor_listener_pvt {
   pthread_t poll_thread;
   int dead;
   struct ast_sem sem;
};

static void default_listener_pvt_destroy(struct default_taskprocessor_listener_pvt *pvt)
{
   ast_assert(pvt->dead);
   ast_sem_destroy(&pvt->sem);
   ast_free(pvt);
}

static void default_listener_pvt_dtor(struct ast_taskprocessor_listener *listener)
{
   struct default_taskprocessor_listener_pvt *pvt = listener->user_data;

   default_listener_pvt_destroy(pvt);

   listener->user_data = NULL;
}

/*!
 * \brief Function that processes tasks in the taskprocessor
 * \internal
 */
static void *default_tps_processing_function(void *data)
{
   struct ast_taskprocessor_listener *listener = data;
   struct ast_taskprocessor *tps = listener->tps;
   struct default_taskprocessor_listener_pvt *pvt = listener->user_data;
   int sem_value;
   int res;

   while (!pvt->dead) {
      res = ast_sem_wait(&pvt->sem);
      if (res != 0 && errno != EINTR) {
         ast_log(LOG_ERROR, "ast_sem_wait(): %s\n",
            strerror(errno));
         /* Just give up */
         break;
      }
      ast_taskprocessor_execute(tps);
   }

   /* No posting to a dead taskprocessor! */
   res = ast_sem_getvalue(&pvt->sem, &sem_value);
   ast_assert(res == 0 && sem_value == 0);

   /* Free the shutdown reference (see default_listener_shutdown) */
   ao2_t_ref(listener->tps, -1, "tps-shutdown");

   return NULL;
}

static int default_listener_start(struct ast_taskprocessor_listener *listener)
{
   struct default_taskprocessor_listener_pvt *pvt = listener->user_data;

   if (ast_pthread_create(&pvt->poll_thread, NULL, default_tps_processing_function, listener)) {
      return -1;
   }

   return 0;
}

static void default_task_pushed(struct ast_taskprocessor_listener *listener, int was_empty)
{
   struct default_taskprocessor_listener_pvt *pvt = listener->user_data;

   if (ast_sem_post(&pvt->sem) != 0) {
      ast_log(LOG_ERROR, "Failed to notify of enqueued task: %s\n",
         strerror(errno));
   }
}

static int default_listener_die(void *data)
{
   struct default_taskprocessor_listener_pvt *pvt = data;
   pvt->dead = 1;
   return 0;
}

static void default_listener_shutdown(struct ast_taskprocessor_listener *listener)
{
   struct default_taskprocessor_listener_pvt *pvt = listener->user_data;
   int res;

   /* Hold a reference during shutdown */
   ao2_t_ref(listener->tps, +1, "tps-shutdown");

   if (ast_taskprocessor_push(listener->tps, default_listener_die, pvt)) {
      /* This will cause the thread to exit early without completing tasks already
       * in the queue.  This is probably the least bad option in this situation. */
      default_listener_die(pvt);
   }

   ast_assert(pvt->poll_thread != AST_PTHREADT_NULL);

   if (pthread_equal(pthread_self(), pvt->poll_thread)) {
      res = pthread_detach(pvt->poll_thread);
      if (res != 0) {
         ast_log(LOG_ERROR, "pthread_detach(): %s\n", strerror(errno));
      }
   } else {
      res = pthread_join(pvt->poll_thread, NULL);
      if (res != 0) {
         ast_log(LOG_ERROR, "pthread_join(): %s\n", strerror(errno));
      }
   }
   pvt->poll_thread = AST_PTHREADT_NULL;
}

static const struct ast_taskprocessor_listener_callbacks default_listener_callbacks = {
   .start = default_listener_start,
   .task_pushed = default_task_pushed,
   .shutdown = default_listener_shutdown,
   .dtor = default_listener_pvt_dtor,
};

/*!
 * \internal
 * \brief Clean up resources on Asterisk shutdown
 */
static void tps_shutdown(void)
{
   ast_cli_unregister_multiple(taskprocessor_clis, ARRAY_LEN(taskprocessor_clis));
   AST_VECTOR_CALLBACK_VOID(&overloaded_subsystems, ast_free);
   AST_VECTOR_RW_FREE(&overloaded_subsystems);
   ao2_t_ref(tps_singletons, -1, "Unref tps_singletons in shutdown");
   tps_singletons = NULL;
}

/* initialize the taskprocessor container and register CLI operations */
int ast_tps_init(void)
{
   tps_singletons = ao2_container_alloc_hash(AO2_ALLOC_OPT_LOCK_MUTEX, 0,
      TPS_MAX_BUCKETS, tps_hash_cb, NULL, tps_cmp_cb);
   if (!tps_singletons) {
      ast_log(LOG_ERROR, "taskprocessor container failed to initialize!\n");
      return -1;
   }

   if (AST_VECTOR_RW_INIT(&overloaded_subsystems, 10)) {
      ao2_ref(tps_singletons, -1);
      ast_log(LOG_ERROR, "taskprocessor subsystems vector failed to initialize!\n");
      return -1;
   }

   ast_cond_init(&cli_ping_cond, NULL);

   ast_cli_register_multiple(taskprocessor_clis, ARRAY_LEN(taskprocessor_clis));

   ast_register_cleanup(tps_shutdown);

   return 0;
}

/* allocate resources for the task */
static struct tps_task *tps_task_alloc(int (*task_exe)(void *datap), void *datap)
{
   struct tps_task *t;
   if (!task_exe) {
      ast_log(LOG_ERROR, "task_exe is NULL!\n");
      return NULL;
   }

   t = ast_calloc(1, sizeof(*t));
   if (!t) {
      ast_log(LOG_ERROR, "failed to allocate task!\n");
      return NULL;
   }

   t->callback.execute = task_exe;
   t->datap = datap;

   return t;
}

static struct tps_task *tps_task_alloc_local(int (*task_exe)(struct ast_taskprocessor_local *local), void *datap)
{
   struct tps_task *t;
   if (!task_exe) {
      ast_log(LOG_ERROR, "task_exe is NULL!\n");
      return NULL;
   }

   t = ast_calloc(1, sizeof(*t));
   if (!t) {
      ast_log(LOG_ERROR, "failed to allocate task!\n");
      return NULL;
   }

   t->callback.execute_local = task_exe;
   t->datap = datap;
   t->wants_local = 1;

   return t;
}

/* release task resources */
static void *tps_task_free(struct tps_task *task)
{
   ast_free(task);
   return NULL;
}

/* Taskprocessor tab completion.
 *
 * The caller of this function is responsible for argument
 * position checks prior to calling.
 */
static char *tps_taskprocessor_tab_complete(struct ast_cli_args *a)
{
   int tklen;
   struct ast_taskprocessor *p;
   struct ao2_iterator i;

   tklen = strlen(a->word);
   i = ao2_iterator_init(tps_singletons, 0);
   while ((p = ao2_iterator_next(&i))) {
      if (!strncasecmp(a->word, p->name, tklen)) {
         if (ast_cli_completion_add(ast_strdup(p->name))) {
            ast_taskprocessor_unreference(p);
            break;
         }
      }
      ast_taskprocessor_unreference(p);
   }
   ao2_iterator_destroy(&i);

   return NULL;
}

/* ping task handling function */
static int tps_ping_handler(void *datap)
{
   ast_mutex_lock(&cli_ping_cond_lock);
   ast_cond_signal(&cli_ping_cond);
   ast_mutex_unlock(&cli_ping_cond_lock);
   return 0;
}

/* ping the specified taskprocessor and display the ping time on the CLI */
static char *cli_tps_ping(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a)
{
   struct timeval begin, end, delta;
   const char *name;
   struct timeval when;
   struct timespec ts;
   struct ast_taskprocessor *tps;

   switch (cmd) {
   case CLI_INIT:
      e->command = "core ping taskprocessor";
      e->usage =
         "Usage: core ping taskprocessor <taskprocessor>\n"
         "  Displays the time required for a task to be processed\n";
      return NULL;
   case CLI_GENERATE:
      if (a->pos == 3) {
         return tps_taskprocessor_tab_complete(a);
      } else {
         return NULL;
      }
   }

   if (a->argc != 4)
      return CLI_SHOWUSAGE;

   name = a->argv[3];
   if (!(tps = ast_taskprocessor_get(name, TPS_REF_IF_EXISTS))) {
      ast_cli(a->fd, "\nping failed: %s not found\n\n", name);
      return CLI_SUCCESS;
   }
   ast_cli(a->fd, "\npinging %s ...", name);

   /*
    * Wait up to 5 seconds for a ping reply.
    *
    * On a very busy system it could take awhile to get a
    * ping response from some taskprocessors.
    */
   begin = ast_tvnow();
   when = ast_tvadd(begin, ast_samp2tv(5000, 1000));
   ts.tv_sec = when.tv_sec;
   ts.tv_nsec = when.tv_usec * 1000;

   ast_mutex_lock(&cli_ping_cond_lock);
   if (ast_taskprocessor_push(tps, tps_ping_handler, 0) < 0) {
      ast_mutex_unlock(&cli_ping_cond_lock);
      ast_cli(a->fd, "\nping failed: could not push task to %s\n\n", name);
      ast_taskprocessor_unreference(tps);
      return CLI_FAILURE;
   }
   ast_cond_timedwait(&cli_ping_cond, &cli_ping_cond_lock, &ts);
   ast_mutex_unlock(&cli_ping_cond_lock);

   end = ast_tvnow();
   delta = ast_tvsub(end, begin);
   ast_cli(a->fd, "\n\t%24s ping time: %.1ld.%.6ld sec\n\n", name, (long)delta.tv_sec, (long int)delta.tv_usec);
   ast_taskprocessor_unreference(tps);
   return CLI_SUCCESS;
}

/*!
 * \internal
 * \brief Taskprocessor ao2 container sort function.
 * \since 13.8.0
 *
 * \param obj_left pointer to the (user-defined part) of an object.
 * \param obj_right pointer to the (user-defined part) of an object.
 * \param flags flags from ao2_callback()
 *   OBJ_SEARCH_OBJECT - if set, 'obj_right', is an object.
 *   OBJ_SEARCH_KEY - if set, 'obj_right', is a search key item that is not an object.
 *   OBJ_SEARCH_PARTIAL_KEY - if set, 'obj_right', is a partial search key item that is not an object.
 *
 * \retval <0 if obj_left < obj_right
 * \retval =0 if obj_left == obj_right
 * \retval >0 if obj_left > obj_right
 */
static int tps_sort_cb(const void *obj_left, const void *obj_right, int flags)
{
   const struct ast_taskprocessor *tps_left = obj_left;
   const struct ast_taskprocessor *tps_right = obj_right;
   const char *right_key = obj_right;
   int cmp;

   switch (flags & OBJ_SEARCH_MASK) {
   default:
   case OBJ_SEARCH_OBJECT:
      right_key = tps_right->name;
      /* Fall through */
   case OBJ_SEARCH_KEY:
      cmp = strcasecmp(tps_left->name, right_key);
      break;
   case OBJ_SEARCH_PARTIAL_KEY:
      cmp = strncasecmp(tps_left->name, right_key, strlen(right_key));
      break;
   }
   return cmp;
}

#define FMT_HEADERS     "%-70s %10s %10s %10s %10s %10s\n"
#define FMT_FIELDS      "%-70s %10lu %10lu %10lu %10lu %10lu\n"

/*!
 * \internal
 * \brief Print taskprocessor information to CLI.
 * \since 13.30.0
 *
 * \param fd the file descriptor
 * \param tps the taskprocessor
 */
static void tps_report_taskprocessor_list_helper(int fd, struct ast_taskprocessor *tps)
{
   ast_cli(fd, FMT_FIELDS, tps->name, tps->stats._tasks_processed_count,
      tps->tps_queue_size, tps->stats.max_qsize, tps->tps_queue_low,
      tps->tps_queue_high);
}

/*!
 * \internal
 * \brief Prints an optionally narrowed down list of taskprocessors to the CLI.
 * \since 13.30.0
 *
 * \param fd the file descriptor
 * \param like the string we are matching on
 *
 * \retval number of taskprocessors on success
 * \retval 0 otherwise
 */
static int tps_report_taskprocessor_list(int fd, const char *like)
{
   int tps_count = 0;
   int word_len;
   struct ao2_container *sorted_tps;
   struct ast_taskprocessor *tps;
   struct ao2_iterator iter;

   sorted_tps = ao2_container_alloc_rbtree(AO2_ALLOC_OPT_LOCK_NOLOCK, 0, tps_sort_cb,
      NULL);
   if (!sorted_tps
      || ao2_container_dup(sorted_tps, tps_singletons, 0)) {
      ast_debug(1, "Failed to retrieve sorted taskprocessors\n");
      ao2_cleanup(sorted_tps);
      return 0;
   }

   word_len = strlen(like);
   iter = ao2_iterator_init(sorted_tps, AO2_ITERATOR_UNLINK);
   while ((tps = ao2_iterator_next(&iter))) {
      if (like) {
         if (!strncasecmp(like, tps->name, word_len)) {
            tps_report_taskprocessor_list_helper(fd, tps);
            tps_count++;
         }
      } else {
         tps_report_taskprocessor_list_helper(fd, tps);
         tps_count++;
      }
      ast_taskprocessor_unreference(tps);
   }
   ao2_iterator_destroy(&iter);
   ao2_ref(sorted_tps, -1);

   return tps_count;
}

static char *cli_tps_report(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a)
{
   const char *like;

   switch (cmd) {
   case CLI_INIT:
      e->command = "core show taskprocessors [like]";
      e->usage =
         "Usage: core show taskprocessors [like keyword]\n"
         "  Shows a list of instantiated task processors and their statistics\n";
      return NULL;
   case CLI_GENERATE:
      if (a->pos == e->args) {
         return tps_taskprocessor_tab_complete(a);
      } else {
         return NULL;
      }
   }

   if (a->argc == e->args - 1) {
      like = "";
   } else if (a->argc == e->args + 1 && !strcasecmp(a->argv[e->args-1], "like")) {
      like = a->argv[e->args];
   } else {
      return CLI_SHOWUSAGE;
   }

   ast_cli(a->fd, "\n" FMT_HEADERS, "Processor", "Processed", "In Queue", "Max Depth", "Low water", "High water");
   ast_cli(a->fd, "\n%d taskprocessors\n\n", tps_report_taskprocessor_list(a->fd, like));

   return CLI_SUCCESS;
}

/* hash callback for astobj2 */
static int tps_hash_cb(const void *obj, const int flags)
{
   const struct ast_taskprocessor *tps = obj;
   const char *name = flags & OBJ_KEY ? obj : tps->name;

   return ast_str_case_hash(name);
}

/* compare callback for astobj2 */
static int tps_cmp_cb(void *obj, void *arg, int flags)
{
   struct ast_taskprocessor *lhs = obj, *rhs = arg;
   const char *rhsname = flags & OBJ_KEY ? arg : rhs->name;

   return !strcasecmp(lhs->name, rhsname) ? CMP_MATCH | CMP_STOP : 0;
}

static int subsystem_match(struct subsystem_alert *alert, const char *subsystem)
{
   return !strcmp(alert->subsystem, subsystem);
}

static int subsystem_cmp(struct subsystem_alert *a, struct subsystem_alert *b)
{
   return strcmp(a->subsystem, b->subsystem);
}

unsigned int ast_taskprocessor_get_subsystem_alert(const char *subsystem)
{
   struct subsystem_alert *alert;
   unsigned int count = 0;
   int idx;

   AST_VECTOR_RW_RDLOCK(&overloaded_subsystems);
   idx = AST_VECTOR_GET_INDEX(&overloaded_subsystems, subsystem, subsystem_match);
   if (idx >= 0) {
      alert = AST_VECTOR_GET(&overloaded_subsystems, idx);
      count = alert->alert_count;
   }
   AST_VECTOR_RW_UNLOCK(&overloaded_subsystems);

   return count;
}

static void subsystem_alert_increment(const char *subsystem)
{
   struct subsystem_alert *alert;
   int idx;

   if (ast_strlen_zero(subsystem)) {
      return;
   }

   AST_VECTOR_RW_WRLOCK(&overloaded_subsystems);
   idx = AST_VECTOR_GET_INDEX(&overloaded_subsystems, subsystem, subsystem_match);
   if (idx >= 0) {
      alert = AST_VECTOR_GET(&overloaded_subsystems, idx);
      alert->alert_count++;
      AST_VECTOR_RW_UNLOCK(&overloaded_subsystems);
      return;
   }

   alert = ast_malloc(sizeof(*alert) + strlen(subsystem) + 1);
   if (!alert) {
      AST_VECTOR_RW_UNLOCK(&overloaded_subsystems);
      return;
   }
   alert->alert_count = 1;
   strcpy(alert->subsystem, subsystem); /* Safe */

   if (AST_VECTOR_APPEND(&overloaded_subsystems, alert)) {
      ast_free(alert);
   }
   AST_VECTOR_RW_UNLOCK(&overloaded_subsystems);
}

static void subsystem_alert_decrement(const char *subsystem)
{
   struct subsystem_alert *alert;
   int idx;

   if (ast_strlen_zero(subsystem)) {
      return;
   }

   AST_VECTOR_RW_WRLOCK(&overloaded_subsystems);
   idx = AST_VECTOR_GET_INDEX(&overloaded_subsystems, subsystem, subsystem_match);
   if (idx < 0) {
      ast_log(LOG_ERROR,
         "Can't decrement alert count for subsystem '%s' as it wasn't in alert\n", subsystem);
      AST_VECTOR_RW_UNLOCK(&overloaded_subsystems);
      return;
   }
   alert = AST_VECTOR_GET(&overloaded_subsystems, idx);

   alert->alert_count--;
   if (alert->alert_count <= 0) {
      AST_VECTOR_REMOVE(&overloaded_subsystems, idx, 0);
      ast_free(alert);
   }

   AST_VECTOR_RW_UNLOCK(&overloaded_subsystems);
}

static void subsystem_copy(struct subsystem_alert *alert,
   struct subsystem_alert_vector *vector)
{
   struct subsystem_alert *alert_copy;
   alert_copy = ast_malloc(sizeof(*alert_copy) + strlen(alert->subsystem) + 1);
   if (!alert_copy) {
      return;
   }
   alert_copy->alert_count = alert->alert_count;
   strcpy(alert_copy->subsystem, alert->subsystem); /* Safe */
   if (AST_VECTOR_ADD_SORTED(vector, alert_copy, subsystem_cmp)) {
      ast_free(alert_copy);
   }
}

static char *cli_subsystem_alert_report(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a)
{
   struct subsystem_alert_vector sorted_subsystems;
   int i;

#define FMT_HEADERS_SUBSYSTEM    "%-32s %12s\n"
#define FMT_FIELDS_SUBSYSTEM     "%-32s %12u\n"

   switch (cmd) {
   case CLI_INIT:
      e->command = "core show taskprocessor alerted subsystems";
      e->usage =
         "Usage: core show taskprocessor alerted subsystems\n"
         "  Shows a list of task processor subsystems that are currently alerted\n";
      return NULL;
   case CLI_GENERATE:
      return NULL;
   }

   if (a->argc != e->args) {
      return CLI_SHOWUSAGE;
   }

   if (AST_VECTOR_INIT(&sorted_subsystems, AST_VECTOR_SIZE(&overloaded_subsystems))) {
      return CLI_FAILURE;
   }

   AST_VECTOR_RW_RDLOCK(&overloaded_subsystems);
   for (i = 0; i < AST_VECTOR_SIZE(&overloaded_subsystems); i++) {
      subsystem_copy(AST_VECTOR_GET(&overloaded_subsystems, i), &sorted_subsystems);
   }
   AST_VECTOR_RW_UNLOCK(&overloaded_subsystems);

   ast_cli(a->fd, "\n" FMT_HEADERS_SUBSYSTEM, "Subsystem", "Alert Count");

   for (i = 0; i < AST_VECTOR_SIZE(&sorted_subsystems); i++) {
      struct subsystem_alert *alert = AST_VECTOR_GET(&sorted_subsystems, i);
      ast_cli(a->fd, FMT_FIELDS_SUBSYSTEM, alert->subsystem, alert->alert_count);
   }

   ast_cli(a->fd, "\n%zu subsystems\n\n", AST_VECTOR_SIZE(&sorted_subsystems));

   AST_VECTOR_CALLBACK_VOID(&sorted_subsystems, ast_free);
   AST_VECTOR_FREE(&sorted_subsystems);

   return CLI_SUCCESS;
}


/*! Count of the number of taskprocessors in high water alert. */
static unsigned int tps_alert_count;

/*! Access protection for tps_alert_count */
AST_RWLOCK_DEFINE_STATIC(tps_alert_lock);

/*!
 * \internal
 * \brief Add a delta to tps_alert_count with protection.
 * \since 13.10.0
 *
 * \param tps Taskprocessor updating queue water mark alert trigger.
 * \param delta The amount to add to tps_alert_count.
 *
 * \return Nothing
 */
static void tps_alert_add(struct ast_taskprocessor *tps, int delta)
{
   unsigned int old;

   ast_rwlock_wrlock(&tps_alert_lock);
   old = tps_alert_count;
   tps_alert_count += delta;
   if (DEBUG_ATLEAST(3)
      /* and tps_alert_count becomes zero or non-zero */
      && !old != !tps_alert_count) {
      ast_log(LOG_DEBUG, "Taskprocessor '%s' %s the high water alert.\n",
         tps->name, tps_alert_count ? "triggered" : "cleared");
   }

   if (tps->subsystem[0] != '\0') {
      if (delta > 0) {
         subsystem_alert_increment(tps->subsystem);
      } else {
         subsystem_alert_decrement(tps->subsystem);
      }
   }

   ast_rwlock_unlock(&tps_alert_lock);
}

unsigned int ast_taskprocessor_alert_get(void)
{
   unsigned int count;

   ast_rwlock_rdlock(&tps_alert_lock);
   count = tps_alert_count;
   ast_rwlock_unlock(&tps_alert_lock);

   return count;
}

int ast_taskprocessor_alert_set_levels(struct ast_taskprocessor *tps, long low_water, long high_water)
{
   if (!tps || high_water < 0 || high_water < low_water) {
      return -1;
   }

   if (low_water < 0) {
      /* Set low water level to 90% of high water level */
      low_water = (high_water * 9) / 10;
   }

   ao2_lock(tps);

   tps->tps_queue_low = low_water;
   tps->tps_queue_high = high_water;

   if (tps->high_water_alert) {
      if (!tps->tps_queue_size || tps->tps_queue_size < low_water) {
         /* Update water mark alert immediately */
         tps->high_water_alert = 0;
         tps_alert_add(tps, -1);
      }
   } else {
      if (high_water < tps->tps_queue_size) {
         /* Update water mark alert immediately */
         tps->high_water_alert = 1;
         tps_alert_add(tps, +1);
      }
   }

   ao2_unlock(tps);

   return 0;
}

/* destroy the taskprocessor */
static void tps_taskprocessor_dtor(void *tps)
{
   struct ast_taskprocessor *t = tps;
   struct tps_task *task;

   while ((task = AST_LIST_REMOVE_HEAD(&t->tps_queue, list))) {
      tps_task_free(task);
   }
   t->tps_queue_size = 0;

   if (t->high_water_alert) {
      t->high_water_alert = 0;
      tps_alert_add(t, -1);
   }

   ao2_cleanup(t->listener);
   t->listener = NULL;
}

/* pop the front task and return it */
static struct tps_task *tps_taskprocessor_pop(struct ast_taskprocessor *tps)
{
   struct tps_task *task;

   if ((task = AST_LIST_REMOVE_HEAD(&tps->tps_queue, list))) {
      --tps->tps_queue_size;
      if (tps->high_water_alert && tps->tps_queue_size <= tps->tps_queue_low) {
         tps->high_water_alert = 0;
         tps_alert_add(tps, -1);
      }
   }
   return task;
}

long ast_taskprocessor_size(struct ast_taskprocessor *tps)
{
   return (tps) ? tps->tps_queue_size : -1;
}

/* taskprocessor name accessor */
const char *ast_taskprocessor_name(struct ast_taskprocessor *tps)
{
   if (!tps) {
      ast_log(LOG_ERROR, "no taskprocessor specified!\n");
      return NULL;
   }
   return tps->name;
}

static void listener_shutdown(struct ast_taskprocessor_listener *listener)
{
   listener->callbacks->shutdown(listener);
   ao2_ref(listener->tps, -1);
}

static void taskprocessor_listener_dtor(void *obj)
{
   struct ast_taskprocessor_listener *listener = obj;

   if (listener->callbacks->dtor) {
      listener->callbacks->dtor(listener);
   }
}

struct ast_taskprocessor_listener *ast_taskprocessor_listener_alloc(const struct ast_taskprocessor_listener_callbacks *callbacks, void *user_data)
{
   struct ast_taskprocessor_listener *listener;

   listener = ao2_alloc(sizeof(*listener), taskprocessor_listener_dtor);
   if (!listener) {
      return NULL;
   }
   listener->callbacks = callbacks;
   listener->user_data = user_data;

   return listener;
}

struct ast_taskprocessor *ast_taskprocessor_listener_get_tps(const struct ast_taskprocessor_listener *listener)
{
   ao2_ref(listener->tps, +1);
   return listener->tps;
}

void *ast_taskprocessor_listener_get_user_data(const struct ast_taskprocessor_listener *listener)
{
   return listener->user_data;
}

static void *default_listener_pvt_alloc(void)
{
   struct default_taskprocessor_listener_pvt *pvt;

   pvt = ast_calloc(1, sizeof(*pvt));
   if (!pvt) {
      return NULL;
   }
   pvt->poll_thread = AST_PTHREADT_NULL;
   if (ast_sem_init(&pvt->sem, 0, 0) != 0) {
      ast_log(LOG_ERROR, "ast_sem_init(): %s\n", strerror(errno));
      ast_free(pvt);
      return NULL;
   }
   return pvt;
}

/*!
 * \internal
 * \brief Allocate a task processor structure
 *
 * \param name Name of the task processor.
 * \param listener Listener to associate with the task processor.
 *
 * \return The newly allocated task processor.
 *
 * \pre tps_singletons must be locked by the caller.
 */
static struct ast_taskprocessor *__allocate_taskprocessor(const char *name, struct ast_taskprocessor_listener *listener)
{
   struct ast_taskprocessor *p;
   char *subsystem_separator;
   size_t subsystem_length = 0;
   size_t name_length;

   name_length = strlen(name);
   subsystem_separator = strchr(name, '/');
   if (subsystem_separator) {
      subsystem_length = subsystem_separator - name;
   }

   p = ao2_alloc(sizeof(*p) + name_length + subsystem_length + 2, tps_taskprocessor_dtor);
   if (!p) {
      ast_log(LOG_WARNING, "failed to create taskprocessor '%s'\n", name);
      return NULL;
   }

   /* Set default congestion water level alert triggers. */
   p->tps_queue_low = (AST_TASKPROCESSOR_HIGH_WATER_LEVEL * 9) / 10;
   p->tps_queue_high = AST_TASKPROCESSOR_HIGH_WATER_LEVEL;

   strcpy(p->name, name); /* Safe */
   p->subsystem = p->name + name_length + 1;
   ast_copy_string(p->subsystem, name, subsystem_length + 1);

   ao2_ref(listener, +1);
   p->listener = listener;

   p->thread = AST_PTHREADT_NULL;

   ao2_ref(p, +1);
   listener->tps = p;

   if (!(ao2_link_flags(tps_singletons, p, OBJ_NOLOCK))) {
      ast_log(LOG_ERROR, "Failed to add taskprocessor '%s' to container\n", p->name);
      listener->tps = NULL;
      ao2_ref(p, -2);
      return NULL;
   }

   return p;
}

static struct ast_taskprocessor *__start_taskprocessor(struct ast_taskprocessor *p)
{
   if (p && p->listener->callbacks->start(p->listener)) {
      ast_log(LOG_ERROR, "Unable to start taskprocessor listener for taskprocessor %s\n",
         p->name);
      ast_taskprocessor_unreference(p);

      return NULL;
   }

   return p;
}

/* Provide a reference to a taskprocessor.  Create the taskprocessor if necessary, but don't
 * create the taskprocessor if we were told via ast_tps_options to return a reference only
 * if it already exists */
struct ast_taskprocessor *ast_taskprocessor_get(const char *name, enum ast_tps_options create)
{
   struct ast_taskprocessor *p;
   struct ast_taskprocessor_listener *listener;
   struct default_taskprocessor_listener_pvt *pvt;

   if (ast_strlen_zero(name)) {
      ast_log(LOG_ERROR, "requesting a nameless taskprocessor!!!\n");
      return NULL;
   }
   ao2_lock(tps_singletons);
   p = ao2_find(tps_singletons, name, OBJ_KEY | OBJ_NOLOCK);
   if (p || (create & TPS_REF_IF_EXISTS)) {
      /* calling function does not want a new taskprocessor to be created if it doesn't already exist */
      ao2_unlock(tps_singletons);
      return p;
   }

   /* Create a new taskprocessor. Start by creating a default listener */
   pvt = default_listener_pvt_alloc();
   if (!pvt) {
      ao2_unlock(tps_singletons);
      return NULL;
   }
   listener = ast_taskprocessor_listener_alloc(&default_listener_callbacks, pvt);
   if (!listener) {
      ao2_unlock(tps_singletons);
      default_listener_pvt_destroy(pvt);
      return NULL;
   }

   p = __allocate_taskprocessor(name, listener);
   ao2_unlock(tps_singletons);
   p = __start_taskprocessor(p);
   ao2_ref(listener, -1);

   return p;
}

struct ast_taskprocessor *ast_taskprocessor_create_with_listener(const char *name, struct ast_taskprocessor_listener *listener)
{
   struct ast_taskprocessor *p;

   ao2_lock(tps_singletons);
   p = ao2_find(tps_singletons, name, OBJ_KEY | OBJ_NOLOCK);
   if (p) {
      ao2_unlock(tps_singletons);
      ast_taskprocessor_unreference(p);
      return NULL;
   }

   p = __allocate_taskprocessor(name, listener);
   ao2_unlock(tps_singletons);

   return __start_taskprocessor(p);
}

void ast_taskprocessor_set_local(struct ast_taskprocessor *tps,
   void *local_data)
{
   SCOPED_AO2LOCK(lock, tps);
   tps->local_data = local_data;
}

/* decrement the taskprocessor reference count and unlink from the container if necessary */
void *ast_taskprocessor_unreference(struct ast_taskprocessor *tps)
{
   if (!tps) {
      return NULL;
   }

   /* To prevent another thread from finding and getting a reference to this
    * taskprocessor we hold the singletons lock. If we didn't do this then
    * they may acquire it and find that the listener has been shut down.
    */
   ao2_lock(tps_singletons);

   if (ao2_ref(tps, -1) > 3) {
      ao2_unlock(tps_singletons);
      return NULL;
   }

   /* If we're down to 3 references, then those must be:
    * 1. The reference we just got rid of
    * 2. The container
    * 3. The listener
    */
   ao2_unlink_flags(tps_singletons, tps, OBJ_NOLOCK);
   ao2_unlock(tps_singletons);

   listener_shutdown(tps->listener);
   return NULL;
}

/* push the task into the taskprocessor queue */
static int taskprocessor_push(struct ast_taskprocessor *tps, struct tps_task *t)
{
   int previous_size;
   int was_empty;

   if (!tps) {
      ast_log(LOG_ERROR, "tps is NULL!\n");
      return -1;
   }

   if (!t) {
      ast_log(LOG_ERROR, "t is NULL!\n");
      return -1;
   }

   ao2_lock(tps);
   AST_LIST_INSERT_TAIL(&tps->tps_queue, t, list);
   previous_size = tps->tps_queue_size++;

   if (tps->tps_queue_high <= tps->tps_queue_size) {
      if (!tps->high_water_alert) {
         ast_log(LOG_WARNING, "The '%s' task processor queue reached %ld scheduled tasks%s.\n",
            tps->name, tps->tps_queue_size, tps->high_water_warned ? " again" : "");
         tps->high_water_warned = 1;
         tps->high_water_alert = 1;
         tps_alert_add(tps, +1);
      }
   }

   /* The currently executing task counts as still in queue */
   was_empty = tps->executing ? 0 : previous_size == 0;
   ao2_unlock(tps);
   tps->listener->callbacks->task_pushed(tps->listener, was_empty);
   return 0;
}

int ast_taskprocessor_push(struct ast_taskprocessor *tps, int (*task_exe)(void *datap), void *datap)
{
   return taskprocessor_push(tps, tps_task_alloc(task_exe, datap));
}

int ast_taskprocessor_push_local(struct ast_taskprocessor *tps, int (*task_exe)(struct ast_taskprocessor_local *datap), void *datap)
{
   return taskprocessor_push(tps, tps_task_alloc_local(task_exe, datap));
}

int ast_taskprocessor_suspend(struct ast_taskprocessor *tps)
{
   if (tps) {
      ao2_lock(tps);
      tps->suspended = 1;
      ao2_unlock(tps);
      return 0;
   }
   return -1;
}

int ast_taskprocessor_unsuspend(struct ast_taskprocessor *tps)
{
   if (tps) {
      ao2_lock(tps);
      tps->suspended = 0;
      ao2_unlock(tps);
      return 0;
   }
   return -1;
}

int ast_taskprocessor_is_suspended(struct ast_taskprocessor *tps)
{
   return tps ? tps->suspended : -1;
}

int ast_taskprocessor_execute(struct ast_taskprocessor *tps)
{
   struct ast_taskprocessor_local local;
   struct tps_task *t;
   long size;

   ao2_lock(tps);
   t = tps_taskprocessor_pop(tps);
   if (!t) {
      ao2_unlock(tps);
      return 0;
   }

   tps->thread = pthread_self();
   tps->executing = 1;

   if (t->wants_local) {
      local.local_data = tps->local_data;
      local.data = t->datap;
   }
   ao2_unlock(tps);

   if (t->wants_local) {
      t->callback.execute_local(&local);
   } else {
      t->callback.execute(t->datap);
   }
   tps_task_free(t);

   ao2_lock(tps);
   tps->thread = AST_PTHREADT_NULL;
   /* We need to check size in the same critical section where we reset the
    * executing bit. Avoids a race condition where a task is pushed right
    * after we pop an empty stack.
    */
   tps->executing = 0;
   size = ast_taskprocessor_size(tps);

   /* Update the stats */
   ++tps->stats._tasks_processed_count;

   /* Include the task we just executed as part of the queue size. */
   if (size >= tps->stats.max_qsize) {
      tps->stats.max_qsize = size + 1;
   }
   ao2_unlock(tps);

   /* If we executed a task, check for the transition to empty */
   if (size == 0 && tps->listener->callbacks->emptied) {
      tps->listener->callbacks->emptied(tps->listener);
   }
   return size > 0;
}

int ast_taskprocessor_is_task(struct ast_taskprocessor *tps)
{
   int is_task;

   ao2_lock(tps);
   is_task = pthread_equal(tps->thread, pthread_self());
   ao2_unlock(tps);
   return is_task;
}

unsigned int ast_taskprocessor_seq_num(void)
{
   static int seq_num;

   return (unsigned int) ast_atomic_fetchadd_int(&seq_num, +1);
}

#define SEQ_STR_SIZE (1 + 8 + 1) /* Dash plus 8 hex digits plus null terminator */

void ast_taskprocessor_name_append(char *buf, unsigned int size, const char *name)
{
   int final_size = strlen(name) + SEQ_STR_SIZE;

   ast_assert(buf != NULL && name != NULL);
   ast_assert(final_size <= size);

   snprintf(buf, final_size, "%s-%08x", name, ast_taskprocessor_seq_num());
}

void ast_taskprocessor_build_name(char *buf, unsigned int size, const char *format, ...)
{
   va_list ap;
   int user_size;

   ast_assert(buf != NULL);
   ast_assert(SEQ_STR_SIZE <= size);

   va_start(ap, format);
   user_size = vsnprintf(buf, size - (SEQ_STR_SIZE - 1), format, ap);
   va_end(ap);
   if (user_size < 0) {
      /*
       * Wow!  We got an output error to a memory buffer.
       * Assume no user part of name written.
       */
      user_size = 0;
   } else if (size < user_size + SEQ_STR_SIZE) {
      /* Truncate user part of name to make sequence number fit. */
      user_size = size - SEQ_STR_SIZE;
   }

   /* Append sequence number to end of user name. */
   snprintf(buf + user_size, SEQ_STR_SIZE, "-%08x", ast_taskprocessor_seq_num());
}

static void tps_reset_stats(struct ast_taskprocessor *tps)
{
   ao2_lock(tps);
   tps->stats._tasks_processed_count = 0;
   tps->stats.max_qsize = 0;
   ao2_unlock(tps);
}

static char *cli_tps_reset_stats(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a)
{
   const char *name;
   struct ast_taskprocessor *tps;

   switch (cmd) {
   case CLI_INIT:
      e->command = "core reset taskprocessor";
      e->usage =
         "Usage: core reset taskprocessor <taskprocessor>\n"
         "    Resets stats for the specified taskprocessor\n";
      return NULL;
   case CLI_GENERATE:
      return tps_taskprocessor_tab_complete(a);
   }

   if (a->argc != 4) {
      return CLI_SHOWUSAGE;
   }

   name = a->argv[3];
   if (!(tps = ast_taskprocessor_get(name, TPS_REF_IF_EXISTS))) {
      ast_cli(a->fd, "\nReset failed: %s not found\n\n", name);
      return CLI_SUCCESS;
   }
   ast_cli(a->fd, "\nResetting %s\n\n", name);

   tps_reset_stats(tps);

   ast_taskprocessor_unreference(tps);

   return CLI_SUCCESS;
}

static char *cli_tps_reset_stats_all(struct ast_cli_entry *e, int cmd, struct ast_cli_args *a)
{
   struct ast_taskprocessor *tps;
   struct ao2_iterator iter;

   switch (cmd) {
   case CLI_INIT:
      e->command = "core reset taskprocessors";
      e->usage =
         "Usage: core reset taskprocessors\n"
         "    Resets stats for all taskprocessors\n";
      return NULL;
   case CLI_GENERATE:
      return NULL;
   }

   if (a->argc != e->args) {
      return CLI_SHOWUSAGE;
   }

   ast_cli(a->fd, "\nResetting stats for all taskprocessors\n\n");

   iter = ao2_iterator_init(tps_singletons, 0);
   while ((tps = ao2_iterator_next(&iter))) {
      tps_reset_stats(tps);
      ast_taskprocessor_unreference(tps);
   }
   ao2_iterator_destroy(&iter);

   return CLI_SUCCESS;
}