schedule.c

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/*
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU General Public License as published by
 *   the Free Software Foundation; either version 2 of the License, or
 *   (at your option) any later version.
 *
 *   This program is distributed in the hope that it will be useful,
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details.
 *
 *   You should have received a copy of the GNU General Public License
 *   along with this program; if not, write to the Free Software
 *   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
 */
 
/**
 * $Id: c5fd2abb57a44689e0e1e4bfd2a25affaf5a587c $
 *
 * @brief Network / worker thread scheduling
 * @file io/schedule.c
 *
 * @copyright 2016 Alan DeKok (aland@freeradius.org)
 */
RCSID("$Id: c5fd2abb57a44689e0e1e4bfd2a25affaf5a587c $")
 
#define LOG_DST sc->log
 
#include <freeradius-devel/autoconf.h>
 
#include <freeradius-devel/io/schedule.h>
#include <freeradius-devel/util/dlist.h>
#include <freeradius-devel/util/rb.h>
#include <freeradius-devel/util/syserror.h>
#include <freeradius-devel/server/trigger.h>
 
#include <pthread.h>
 
/*
 *      Other OS's have sem_init, OS X doesn't.
 */
#ifdef HAVE_SEMAPHORE_H
#include <semaphore.h>
#endif
 
#define SEMAPHORE_LOCKED        (0)
 
#ifdef __APPLE__
#include <mach/task.h>
#include <mach/mach_init.h>
#include <mach/semaphore.h>
 
#undef sem_t
#define sem_t semaphore_t
#undef sem_init
#define sem_init(s,p,c) semaphore_create(mach_task_self(),s,SYNC_POLICY_FIFO,c)
#undef sem_wait
#define sem_wait(s) semaphore_wait(*s)
#undef sem_post
#define sem_post(s) semaphore_signal(*s)
#undef sem_destroy
#define sem_destroy(s) semaphore_destroy(mach_task_self(),*s)
#endif  /* __APPLE__ */
 
#define SEM_WAIT_INTR(_x) do {if (sem_wait(_x) == 0) break;} while (errno == EINTR)
 
/**
 *  Track the child thread status.
 */
typedef enum fr_schedule_child_status_t {
        FR_CHILD_FREE = 0,                      //!< child is free
        FR_CHILD_INITIALIZING,                  //!< initialized, but not running
        FR_CHILD_RUNNING,                       //!< running, and in the running queue
        FR_CHILD_EXITED,                        //!< exited, and in the exited queue
        FR_CHILD_FAIL                           //!< failed, and in the exited queue
} fr_schedule_child_status_t;
 
/** Scheduler specific information for worker threads
 *
 * Wraps a fr_worker_t, tracking additional information that
 * the scheduler uses.
 */
typedef struct {
        TALLOC_CTX      *ctx;                   //!< our allocation ctx
        fr_event_list_t *el;                    //!< our event list
        pthread_t       pthread_id;             //!< the thread of this worker
 
        unsigned int    id;                     //!< a unique ID
        int             uses;                   //!< how many network threads are using it
        fr_time_t       cpu_time;               //!< how much CPU time this worker has used
 
        fr_dlist_t      entry;                  //!< our entry into the linked list of workers
 
        fr_schedule_t   *sc;                    //!< the scheduler we are running under
 
        fr_schedule_child_status_t status;      //!< status of the worker
        fr_worker_t     *worker;                //!< the worker data structure
} fr_schedule_worker_t;
 
/** Scheduler specific information for network threads
 *
 * Wraps a fr_network_t, tracking additional information that
 * the scheduler uses.
 */
typedef struct {
        TALLOC_CTX      *ctx;                   //!< our allocation ctx
        pthread_t       pthread_id;             //!< the thread of this network
 
        unsigned int    id;                     //!< a unique ID
 
        fr_dlist_t      entry;                  //!< our entry into the linked list of networks
 
        fr_schedule_t   *sc;                    //!< the scheduler we are running under
 
        fr_schedule_child_status_t status;      //!< status of the worker
        fr_network_t    *nr;                    //!< the receive data structure
 
        fr_timer_t      *ev;            //!< timer for stats_interval
} fr_schedule_network_t;
 
 
/**
 *  The scheduler
 */
struct fr_schedule_s {
        bool            running;                //!< is the scheduler running?
 
        CONF_SECTION    *cs;                    //!< thread pool configuration section
        fr_event_list_t *el;                    //!< event list for single-threaded mode.
 
        fr_log_t        *log;                   //!< log destination
        fr_log_lvl_t    lvl;                    //!< log level
 
        fr_schedule_config_t *config;           //!< configuration
 
        unsigned int    num_workers_exited;     //!< number of exited workers
 
        sem_t           worker_sem;             //!< for inter-thread signaling
        sem_t           network_sem;            //!< for inter-thread signaling
 
        fr_schedule_thread_instantiate_t        worker_thread_instantiate;      //!< thread instantiation callback
        fr_schedule_thread_detach_t             worker_thread_detach;
 
        fr_dlist_head_t workers;                //!< list of workers
        fr_dlist_head_t networks;               //!< list of networks
 
        fr_network_t    *single_network;        //!< for single-threaded mode
        fr_worker_t     *single_worker;         //!< for single-threaded mode
};
 
static _Thread_local int worker_id;             //!< Internal ID of the current worker thread.
 
/** Return the worker id for the current thread
 *
 * @return worker ID
 */
int fr_schedule_worker_id(void)
{
        return worker_id;
}
 
/** Entry point for worker threads
 *
 * @param[in] arg       the fr_schedule_worker_t
 * @return NULL
 */
static void *fr_schedule_worker_thread(void *arg)
{
        TALLOC_CTX                      *ctx;
        fr_schedule_worker_t            *sw = talloc_get_type_abort(arg, fr_schedule_worker_t);
        fr_schedule_t                   *sc = sw->sc;
        fr_schedule_child_status_t      status = FR_CHILD_FAIL;
        fr_schedule_network_t           *sn;
        char                            worker_name[32];
 
#ifndef __APPLE__
        /*
         * This ifdef is because macOS doesn't use pthread_signmask in its
         * setcontext function, and seems to apply the signal mask of the thread
         * to the entire process when setcontext is called.
         *
         *  * frame #0: 0x00000001934118b0 libsystem_kernel.dylib`sigprocmask
         *  frame #1: 0x0000000193481f3c libsystem_platform.dylib`setcontext + 44
         *  frame #2: 0x0000000100f27298 libcrypto.3.dylib`async_fibre_swapcontext + 52
         *  frame #3: 0x0000000100f274a0 libcrypto.3.dylib`ASYNC_start_job + 496
         *  frame #4: 0x0000000100b17884 libssl.3.dylib`ssl_start_async_job + 116
         *  frame #5: 0x0000000100b17804 libssl.3.dylib`ssl_read_internal + 356
         *  frame #6: 0x0000000100b17a0c libssl.3.dylib`SSL_read + 28
         *  frame #7: 0x00000001004f5b94 libfreeradius-tls.dylib`tls_session_async_handshake_cont(p_result=0x0000000112815c7c, priority=0x0000000112815edc, request=0x0000000112815a80, uctx=0x0000000139160060) at session.c:1366:26
         */
        sigset_t                        sigset;
 
        sigfillset(&sigset);
 
        /*
         *      Ensure workers aren't interrupted by signals.
         *      The main thread, and main event loop are mostly
         *      idle, so they can handle signals.
         */
        pthread_sigmask(SIG_BLOCK, &sigset, NULL);
#endif
 
        worker_id = sw->id;             /* Store the current worker ID */
 
        snprintf(worker_name, sizeof(worker_name), "Worker %d", sw->id);
 
        sw->ctx = ctx = talloc_init("%s", worker_name);
        if (!ctx) {
                ERROR("%s - Failed allocating memory", worker_name);
                goto fail;
        }
 
        INFO("%s - Starting", worker_name);
 
        sw->el = fr_event_list_alloc(ctx, NULL, NULL);
        if (!sw->el) {
                PERROR("%s - Failed creating event list", worker_name);
                goto fail;
        }
 
 
        sw->worker = fr_worker_alloc(ctx, sw->el, worker_name, sc->log, sc->lvl, &sc->config->worker);
        if (!sw->worker) {
                PERROR("%s - Failed creating worker", worker_name);
                goto fail;
        }
 
        /*
         *      @todo make this a registry
         */
        if (sc->worker_thread_instantiate) {
                CONF_SECTION    *cs;
                char            section_name[32];
 
                snprintf(section_name, sizeof(section_name), "%u", sw->id);
 
                cs = cf_section_find(sc->cs, "worker", section_name);
                if (!cs) cs = cf_section_find(sc->cs, "worker", NULL);
 
                if (sc->worker_thread_instantiate(sw->ctx, sw->el, cs) < 0) {
                        PERROR("%s - Worker thread instantiation failed", worker_name);
                        goto fail;
                }
        }
 
        sw->status = FR_CHILD_RUNNING;
 
        /*
         *      Add this worker to all network threads.
         */
        for (sn = fr_dlist_head(&sc->networks);
             sn != NULL;
             sn = fr_dlist_next(&sc->networks, sn)) {
                if (unlikely(fr_network_worker_add(sn->nr, sw->worker) < 0)) {
                        PERROR("%s - Failed adding worker to network %u", worker_name, sn->id);
                        goto fail;      /* FIXME - Should maybe try to undo partial adds? */
                }
        }
 
        DEBUG3("%s - Started", worker_name);
 
        /*
         *      Tell the originator that the thread has started.
         */
        sem_post(&sc->worker_sem);
 
        /*
         *      Do all of the work.
         */
        fr_worker(sw->worker);
 
        status = FR_CHILD_EXITED;
 
fail:
        sw->status = status;
 
        if (sw->worker) {
                fr_worker_destroy(sw->worker);
                sw->worker = NULL;
        }
 
        INFO("%s - Exiting", worker_name);
 
        if (sc->worker_thread_detach) sc->worker_thread_detach(NULL);   /* Fixme once we figure out what uctx should be */
 
        /*
         *      Not looping at this point, but may catch timer/fd
         *      insertions being done after the thread should have
         *      exited.
         */
        if (sw->el) fr_event_loop_exit(sw->el, 1);
 
        /*
         *      Tell the scheduler we're done.
         */
        sem_post(&sc->worker_sem);
 
        talloc_free(ctx);
 
        return NULL;
}
 
 
static void stats_timer(fr_timer_list_t *tl, fr_time_t now, void *uctx)
{
        fr_schedule_network_t           *sn = talloc_get_type_abort(uctx, fr_schedule_network_t);
 
        fr_network_stats_log(sn->nr, sn->sc->log);
 
        (void) fr_timer_at(sn, tl, &sn->ev, fr_time_add(now, sn->sc->config->stats_interval), false, stats_timer, sn);
}
 
/** Initialize and run the network thread.
 *
 * @param[in] arg the fr_schedule_network_t
 * @return NULL
 */
static void *fr_schedule_network_thread(void *arg)
{
        TALLOC_CTX                      *ctx;
        fr_schedule_network_t           *sn = talloc_get_type_abort(arg, fr_schedule_network_t);
        fr_schedule_t                   *sc = sn->sc;
        fr_schedule_child_status_t      status = FR_CHILD_FAIL;
        fr_event_list_t                 *el;
        char                            network_name[32];
 
#ifndef __APPLE__
        /*
         * This ifdef is because macOS doesn't use pthread_signmask in its
         * setcontext function, and seems to apply the signal mask of the thread
         * to the entire process when setcontext is called.
         *
         *  * frame #0: 0x00000001934118b0 libsystem_kernel.dylib`sigprocmask
         *  frame #1: 0x0000000193481f3c libsystem_platform.dylib`setcontext + 44
         *  frame #2: 0x0000000100f27298 libcrypto.3.dylib`async_fibre_swapcontext + 52
         *  frame #3: 0x0000000100f274a0 libcrypto.3.dylib`ASYNC_start_job + 496
         *  frame #4: 0x0000000100b17884 libssl.3.dylib`ssl_start_async_job + 116
         *  frame #5: 0x0000000100b17804 libssl.3.dylib`ssl_read_internal + 356
         *  frame #6: 0x0000000100b17a0c libssl.3.dylib`SSL_read + 28
         *  frame #7: 0x00000001004f5b94 libfreeradius-tls.dylib`tls_session_async_handshake_cont(p_result=0x0000000112815c7c, priority=0x0000000112815edc, request=0x0000000112815a80, uctx=0x0000000139160060) at session.c:1366:26
         */
        sigset_t                        sigset;
 
        sigfillset(&sigset);
 
        /*
         *      Ensure workers aren't interrupted by signals.
         *      The main thread, and main event loop are mostly
         *      idle, so they can handle signals.
         */
        pthread_sigmask(SIG_BLOCK, &sigset, NULL);
#endif
 
        snprintf(network_name, sizeof(network_name), "Network %d", sn->id);
 
        INFO("%s - Starting", network_name);
 
        sn->ctx = ctx = talloc_init("%s", network_name);
        if (!ctx) {
                ERROR("%s - Failed allocating memory", network_name);
                goto fail;
        }
 
        el = fr_event_list_alloc(ctx, NULL, NULL);
        if (!el) {
                PERROR("%s - Failed creating event list", network_name);
                goto fail;
        }
 
        sn->nr = fr_network_create(ctx, el, network_name, sc->log, sc->lvl, &sc->config->network);
        if (!sn->nr) {
                PERROR("%s - Failed creating network", network_name);
                goto fail;
        }
 
        sn->status = FR_CHILD_RUNNING;
 
        /*
         *      Tell the originator that the thread has started.
         */
        sem_post(&sc->network_sem);
 
        DEBUG3("%s - Started", network_name);
 
        /*
         *      Print out statistics for this network IO handler.
         */
        if (fr_time_delta_ispos(sc->config->stats_interval)) {
                (void) fr_timer_in(sn, el->tl, &sn->ev, sn->sc->config->stats_interval, false, stats_timer, sn);
        }
        /*
         *      Call the main event processing loop of the network
         *      thread Will not return until the worker is about
         *      to exit.
         */
        fr_network(sn->nr);
 
        status = FR_CHILD_EXITED;
 
fail:
        sn->status = status;
 
        INFO("%s - Exiting", network_name);
 
        /*
         *      Tell the scheduler we're done.
         */
        sem_post(&sc->network_sem);
 
        talloc_free(ctx);
 
        return NULL;
}
 
/** Creates a new thread using our standard set of options
 *
 * New threads are:
 * - Joinable, i.e. you can call pthread_join on them to confirm they've exited
 * - Immune to catchable signals.
 *
 * @param[out] thread           handled that was created by pthread_create.
 * @param[in] func              entry point for the thread.
 * @param[in] arg               Argument to pass to func.
 * @return
 *      - 0 on success.
 *      - -1 on failure.
 */
int fr_schedule_pthread_create(pthread_t *thread, void *(*func)(void *), void *arg)
{
        pthread_attr_t                  attr;
        int                             ret;
 
        /*
         *      Set the thread to wait around after it's exited
         *      so it can be joined.  This is more of a useful
         *      mechanism for the parent to determine if all
         *      the threads have exited so it can continue with
         *      a graceful shutdown.
         */
        pthread_attr_init(&attr);
        pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_JOINABLE);
 
        ret = pthread_create(thread, &attr, func, arg);
        if (ret != 0) {
                fr_strerror_printf("Failed creating thread: %s", fr_syserror(ret));
                return -1;
        }
 
        return 0;
}
 
/** Create a scheduler and spawn the child threads.
 *
 * @param[in] ctx                               talloc context.
 * @param[in] el                                event list, only for single-threaded mode.
 * @param[in] logger                            destination for all logging messages.
 * @param[in] lvl                               log level.
 * @param[in] worker_thread_instantiate         callback for new worker threads.
 * @param[in] worker_thread_detach              callback to destroy resources
 *                                              allocated by worker_thread_instantiate.
 * @param[in] config                            configuration for the scheduler
 * @return
 *      - NULL on error
 *      - fr_schedule_t new scheduler
 */
fr_schedule_t *fr_schedule_create(TALLOC_CTX *ctx, fr_event_list_t *el,
                                  fr_log_t *logger, fr_log_lvl_t lvl,
                                  fr_schedule_thread_instantiate_t worker_thread_instantiate,
                                  fr_schedule_thread_detach_t worker_thread_detach,
                                  fr_schedule_config_t *config)
{
        unsigned int i;
        fr_schedule_worker_t *sw, *next_sw;
        fr_schedule_network_t *sn, *next_sn;
        fr_schedule_t *sc;
 
        sc = talloc_zero(ctx, fr_schedule_t);
        if (!sc) {
                fr_strerror_const("Failed allocating memory");
                return NULL;
        }
 
        sc->config = config;
        sc->el = el;
        sc->log = logger;
        sc->lvl = lvl;
 
        sc->worker_thread_instantiate = worker_thread_instantiate;
        sc->worker_thread_detach = worker_thread_detach;
        sc->running = true;
 
        /*
         *      If we're single-threaded, create network / worker, and insert them into the event loop.
         */
        if (el) {
                sc->single_network = fr_network_create(sc, el, "Network", sc->log, sc->lvl, &sc->config->network);
                if (!sc->single_network) {
                        PERROR("Failed creating network");
                pre_instantiate_st_fail:
                        talloc_free(sc);
                        return NULL;
                }
 
                sc->single_worker = fr_worker_alloc(sc, el, "Worker", sc->log, sc->lvl, &sc->config->worker);
                if (!sc->single_worker) {
                        PERROR("Failed creating worker");
                        if (unlikely(fr_network_destroy(sc->single_network) < 0)) {
                                PERROR("Failed destroying network");
                        }
                        goto pre_instantiate_st_fail;
                }
 
                /*
                 *      Parent thread-specific data from the single_worker
                 */
                if (sc->worker_thread_instantiate) {
                        CONF_SECTION *subcs;
 
                        subcs = cf_section_find(sc->cs, "worker", "0");
                        if (!subcs) subcs = cf_section_find(sc->cs, "worker", NULL);
 
                        if (sc->worker_thread_instantiate(sc->single_worker, el, subcs) < 0) {
                                PERROR("Worker thread instantiation failed");
                        destroy_both:
                                if (unlikely(fr_network_destroy(sc->single_network) < 0)) {
                                        PERROR("Failed destroying network");
                                }
                                fr_worker_destroy(sc->single_worker);
                                goto pre_instantiate_st_fail;
                        }
                }
 
                if (fr_command_register_hook(NULL, "0", sc->single_worker, cmd_worker_table) < 0) {
                        PERROR("Failed adding worker commands");
                st_fail:
                        if (sc->worker_thread_detach) sc->worker_thread_detach(NULL);
                        goto destroy_both;
                }
 
                if (fr_command_register_hook(NULL, "0", sc->single_network, cmd_network_table) < 0) {
                        PERROR("Failed adding network commands");
                        goto st_fail;
                }
 
                /*
                 *      Register the worker with the network, so
                 *      things like fr_network_send_request() work.
                 */
                fr_network_worker_add_self(sc->single_network, sc->single_worker);
                DEBUG("Scheduler created in single-threaded mode");
 
                if (fr_event_pre_insert(el, fr_worker_pre_event, sc->single_worker) < 0) {
                        fr_strerror_const("Failed adding pre-check to event list");
                        goto st_fail;
                }
 
                /*
                 *      Add the event which processes request_t packets.
                 */
                if (fr_event_post_insert(el, fr_worker_post_event, sc->single_worker) < 0) {
                        fr_strerror_const("Failed inserting post-processing event");
                        goto st_fail;
                }
 
                return sc;
        }
 
        /*
         *      Parse any scheduler-specific configuration.
         */
        if (!config) {
                MEM(sc->config = talloc_zero(sc, fr_schedule_config_t));
                sc->config->max_networks = 1;
                sc->config->max_workers = 4;
        } else {
                sc->config = config;
 
                if (sc->config->max_networks < 1) sc->config->max_networks = 1;
                if (sc->config->max_networks > 64) sc->config->max_networks = 64;
                if (sc->config->max_workers < 1) sc->config->max_workers = 1;
                if (sc->config->max_workers > 64) sc->config->max_workers = 64;
        }
 
        /*
         *      Create the lists which hold the workers and networks.
         */
        fr_dlist_init(&sc->workers, fr_schedule_worker_t, entry);
        fr_dlist_init(&sc->networks, fr_schedule_network_t, entry);
 
        memset(&sc->network_sem, 0, sizeof(sc->network_sem));
        if (sem_init(&sc->network_sem, 0, SEMAPHORE_LOCKED) != 0) {
                ERROR("Failed creating semaphore: %s", fr_syserror(errno));
                talloc_free(sc);
                return NULL;
        }
 
        memset(&sc->worker_sem, 0, sizeof(sc->worker_sem));
        if (sem_init(&sc->worker_sem, 0, SEMAPHORE_LOCKED) != 0) {
                ERROR("Failed creating semaphore: %s", fr_syserror(errno));
                talloc_free(sc);
                return NULL;
        }
 
        /*
         *      Create the network threads first.
         */
        for (i = 0; i < sc->config->max_networks; i++) {
                DEBUG3("Creating %u/%u networks", i + 1, sc->config->max_networks);
 
                /*
                 *      Create a worker "glue" structure
                 */
                sn = talloc_zero(sc, fr_schedule_network_t);
                if (!sn) {
                        ERROR("Network %u - Failed allocating memory", i);
                        break;
                }
 
                sn->id = i;
                sn->sc = sc;
                sn->status = FR_CHILD_INITIALIZING;
                fr_dlist_insert_head(&sc->networks, sn);
 
                if (fr_schedule_pthread_create(&sn->pthread_id, fr_schedule_network_thread, sn) < 0) {
                        PERROR("Failed creating network %u", i);
                        break;
                }
        }
 
        /*
         *      Wait for all of the networks to signal us that either
         *      they've started, OR there's been a problem and they
         *      can't start.
         */
        for (i = 0; i < (unsigned int)fr_dlist_num_elements(&sc->networks); i++) {
                DEBUG3("Waiting for semaphore from network %u/%u",
                       i + 1, (unsigned int)fr_dlist_num_elements(&sc->networks));
                SEM_WAIT_INTR(&sc->network_sem);
        }
 
        /*
         *      See if all of the networks have started.
         */
        for (sn = fr_dlist_head(&sc->networks);
             sn != NULL;
             sn = next_sn) {
                next_sn = fr_dlist_next(&sc->networks, sn);
 
                if (sn->status != FR_CHILD_RUNNING) {
                        fr_dlist_remove(&sc->networks, sn);
                        continue;
                }
        }
 
        /*
         *      Failed to start some workers, refuse to do anything!
         */
        if ((unsigned int)fr_dlist_num_elements(&sc->networks) < sc->config->max_networks) {
                fr_schedule_destroy(&sc);
                return NULL;
        }
 
        /*
         *      Create all of the workers.
         */
        for (i = 0; i < sc->config->max_workers; i++) {
                DEBUG3("Creating %u/%u workers", i + 1, sc->config->max_workers);
 
                /*
                 *      Create a worker "glue" structure
                 */
                sw = talloc_zero(sc, fr_schedule_worker_t);
                if (!sw) {
                        ERROR("Worker %u - Failed allocating memory", i);
                        break;
                }
 
                sw->id = i;
                sw->sc = sc;
                sw->status = FR_CHILD_INITIALIZING;
                fr_dlist_insert_head(&sc->workers, sw);
 
                if (fr_schedule_pthread_create(&sw->pthread_id, fr_schedule_worker_thread, sw) < 0) {
                        PERROR("Failed creating worker %u", i);
                        break;
                }
        }
 
        /*
         *      Wait for all of the workers to signal us that either
         *      they've started, OR there's been a problem and they
         *      can't start.
         */
        for (i = 0; i < (unsigned int)fr_dlist_num_elements(&sc->workers); i++) {
                DEBUG3("Waiting for semaphore from worker %u/%u",
                       i + 1, (unsigned int)fr_dlist_num_elements(&sc->workers));
                SEM_WAIT_INTR(&sc->worker_sem);
        }
 
        /*
         *      See if all of the workers have started.
         */
        for (sw = fr_dlist_head(&sc->workers);
             sw != NULL;
             sw = next_sw) {
 
                next_sw = fr_dlist_next(&sc->workers, sw);
 
                if (sw->status != FR_CHILD_RUNNING) {
                        fr_dlist_remove(&sc->workers, sw);
                        continue;
                }
        }
 
        /*
         *      Failed to start some workers, refuse to do anything!
         */
        if ((unsigned int)fr_dlist_num_elements(&sc->workers) < sc->config->max_workers) {
                fr_schedule_destroy(&sc);
                return NULL;
        }
 
        for (sw = fr_dlist_head(&sc->workers), i = 0;
             sw != NULL;
             sw = next_sw, i++) {
                char buffer[32];
 
                next_sw = fr_dlist_next(&sc->workers, sw);
 
                snprintf(buffer, sizeof(buffer), "%d", i);
                if (fr_command_register_hook(NULL, buffer, sw->worker, cmd_worker_table) < 0) {
                        PERROR("Failed adding worker commands");
                        goto st_fail;
                }
        }
 
        for (sn = fr_dlist_head(&sc->networks), i = 0;
             sn != NULL;
             sn = next_sn, i++) {
                char buffer[32];
 
                next_sn = fr_dlist_next(&sc->networks, sn);
 
                snprintf(buffer, sizeof(buffer), "%d", i);
                if (fr_command_register_hook(NULL, buffer, sn->nr, cmd_network_table) < 0) {
                        PERROR("Failed adding network commands");
                        goto st_fail;
                }
        }
 
        if (sc) INFO("Scheduler created successfully with %u networks and %u workers",
                     sc->config->max_networks, (unsigned int)fr_dlist_num_elements(&sc->workers));
 
        return sc;
}
 
/** Destroy a scheduler, and tell its child threads to exit.
 *
 * @note This may be called with no worker or network threads in the case of a
 *       instantiation error.  This function _should_ deal with that condition
 *       gracefully.
 *
 * @param[in] sc_to_free the scheduler
 * @return
 *      - <0 on error
 *      - 0 on success
 */
int fr_schedule_destroy(fr_schedule_t **sc_to_free)
{
        fr_schedule_t           *sc = *sc_to_free;
        unsigned int            i;
        fr_schedule_worker_t    *sw;
        fr_schedule_network_t   *sn;
        int                     ret;
 
        if (!sc) return 0;
 
        sc->running = false;
 
        /*
         *      Single threaded mode: kill the only network / worker we have.
         */
        if (sc->el) {
                /*
                 *      Destroy the network side first.  It tells the
                 *      workers to close.
                 */
                if (unlikely(fr_network_destroy(sc->single_network) < 0)) {
                        ERROR("Failed destroying network");
                }
                fr_worker_destroy(sc->single_worker);
                goto done;
        }
 
        /*
         *      Signal each network thread to exit.
         */
        for (sn = fr_dlist_head(&sc->networks);
             sn != NULL;
             sn = fr_dlist_next(&sc->networks, sn)) {
                if (fr_network_exit(sn->nr) < 0) {
                        PERROR("Failed signaling network %i to exit", sn->id);
                }
        }
 
        /*
         *      If the network threads are running, tell them to exit,
         *      and wait for them to do so.  Each network thread tells
         *      all of its worker threads that it's exiting.  It then
         *      closes the channels.  When the workers see that there
         *      are no input channels, they exit, too.
         */
        for (i = 0; i < (unsigned int)fr_dlist_num_elements(&sc->networks); i++) {
                DEBUG2("Scheduler - Waiting for semaphore indicating network exit %u/%u", i + 1,
                       (unsigned int)fr_dlist_num_elements(&sc->networks));
                SEM_WAIT_INTR(&sc->network_sem);
        }
        DEBUG2("Scheduler - All networks indicated exit complete");
 
        while ((sn = fr_dlist_head(&sc->networks)) != NULL) {
                fr_dlist_remove(&sc->networks, sn);
 
                /*
                 *      Ensure that the thread has exited before
                 *      cleaning up the context.
                 *
                 *      This also ensures that the child threads have
                 *      exited before the main thread cleans up the
                 *      module instances.
                 */
                if ((ret = pthread_join(sn->pthread_id, NULL)) != 0) {
                        ERROR("Failed joining network %i: %s", sn->id, fr_syserror(ret));
                } else {
                        DEBUG2("Network %i joined (cleaned up)", sn->id);
                }
        }
 
        /*
         *      Wait for all worker threads to finish.  THEN clean up
         *      modules.  Otherwise, the modules will be removed from
         *      underneath the workers!
         */
        for (i = 0; i < (unsigned int)fr_dlist_num_elements(&sc->workers); i++) {
                DEBUG2("Scheduler - Waiting for semaphore indicating worker exit %u/%u", i + 1,
                       (unsigned int)fr_dlist_num_elements(&sc->workers));
                SEM_WAIT_INTR(&sc->worker_sem);
        }
        DEBUG2("Scheduler - All workers indicated exit complete");
 
        /*
         *      Clean up the exited workers.
         */
        while ((sw = fr_dlist_head(&sc->workers)) != NULL) {
                fr_dlist_remove(&sc->workers, sw);
 
                /*
                 *      Ensure that the thread has exited before
                 *      cleaning up the context.
                 *
                 *      This also ensures that the child threads have
                 *      exited before the main thread cleans up the
                 *      module instances.
                 */
                if ((ret = pthread_join(sw->pthread_id, NULL)) != 0) {
                        ERROR("Failed joining worker %i: %s", sw->id, fr_syserror(ret));
                } else {
                        DEBUG2("Worker %i joined (cleaned up)", sw->id);
                }
        }
 
        sem_destroy(&sc->network_sem);
        sem_destroy(&sc->worker_sem);
done:
        /*
         *      Now that all of the workers are done, we can return to
         *      the caller, and have it dlclose() the modules.
         */
        talloc_free(sc);
        *sc_to_free = NULL;
 
        return 0;
}
 
/** Add a fr_listen_t to a scheduler.
 *
 * @param[in] sc the scheduler
 * @param[in] li the ctx and callbacks for the transport.
 * @return
 *      - NULL on error
 *      - the fr_network_t that the socket was added to.
 */
fr_network_t *fr_schedule_listen_add(fr_schedule_t *sc, fr_listen_t *li)
{
        fr_network_t *nr;
 
        (void) talloc_get_type_abort(sc, fr_schedule_t);
 
        if (sc->el) {
                nr = sc->single_network;
        } else {
                fr_schedule_network_t *sn;
 
                /*
                 *      @todo - round robin it among the listeners?
                 *      or maybe add it to the same parent thread?
                 */
                sn = fr_dlist_head(&sc->networks);
                nr = sn->nr;
        }
 
        if (fr_network_listen_add(nr, li) < 0) return NULL;
 
        return nr;
}
 
/** Add a directory NOTE_EXTEND to a scheduler.
 *
 * @param[in] sc the scheduler
 * @param[in] li the ctx and callbacks for the transport.
 * @return
 *      - NULL on error
 *      - the fr_network_t that the socket was added to.
 */
fr_network_t *fr_schedule_directory_add(fr_schedule_t *sc, fr_listen_t *li)
{
        fr_network_t *nr;
 
        (void) talloc_get_type_abort(sc, fr_schedule_t);
 
        if (sc->el) {
                nr = sc->single_network;
        } else {
                fr_schedule_network_t *sn;
 
                /*
                 *      @todo - round robin it among the listeners?
                 *      or maybe add it to the same parent thread?
                 */
                sn = fr_dlist_head(&sc->networks);
                nr = sn->nr;
        }
 
        if (fr_network_directory_add(nr, li) < 0) return NULL;
 
        return nr;
}