/*
 * SPDX-License-Identifier: BSD-3-Clause
 * Copyright 2015 Intel Corporation.
 * Copyright 2012 Hasan Alayli <halayli@gmail.com>
 */

#define RTE_MEM 1

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <stddef.h>
#include <limits.h>
#include <inttypes.h>
#include <unistd.h>
#include <pthread.h>
#include <fcntl.h>
#include <sys/time.h>
#include <sys/mman.h>
#include <sched.h>

#include <rte_prefetch.h>
#include <rte_per_lcore.h>
#include <rte_atomic.h>
#include <rte_atomic_64.h>
#include <rte_log.h>
#include <rte_common.h>
#include <rte_branch_prediction.h>

#include "lthread_api.h"
#include "lthread_int.h"
#include "lthread_sched.h"
#include "lthread_objcache.h"
#include "lthread_timer.h"
#include "lthread_mutex.h"
#include "lthread_cond.h"
#include "lthread_tls.h"
#include "lthread_diag.h"

/*
 * This file implements the lthread scheduler
 * The scheduler is the function lthread_run()
 * This must be run as the main loop of an EAL thread.
 *
 * Currently once a scheduler is created it cannot be destroyed
 * When a scheduler shuts down it is assumed that the application is terminating
 */

static rte_atomic16_t num_schedulers;
static rte_atomic16_t active_schedulers;

/* one scheduler per lcore */
RTE_DEFINE_PER_LCORE(struct lthread_sched *, this_sched) = NULL;

struct lthread_sched *schedcore[LTHREAD_MAX_LCORES];

diag_callback diag_cb;

uint64_t diag_mask;


/* constructor */
RTE_INIT(lthread_sched_ctor)
{
        memset(schedcore, 0, sizeof(schedcore));
        rte_atomic16_init(&num_schedulers);
        rte_atomic16_set(&num_schedulers, 1);
        rte_atomic16_init(&active_schedulers);
        rte_atomic16_set(&active_schedulers, 0);
        diag_cb = NULL;
}


enum sched_alloc_phase {
        SCHED_ALLOC_OK,
        SCHED_ALLOC_QNODE_POOL,
        SCHED_ALLOC_READY_QUEUE,
        SCHED_ALLOC_PREADY_QUEUE,
        SCHED_ALLOC_LTHREAD_CACHE,
        SCHED_ALLOC_STACK_CACHE,
        SCHED_ALLOC_PERLT_CACHE,
        SCHED_ALLOC_TLS_CACHE,
        SCHED_ALLOC_COND_CACHE,
        SCHED_ALLOC_MUTEX_CACHE,
};

static int
_lthread_sched_alloc_resources(struct lthread_sched *new_sched)
{
        int alloc_status;

        do {
                /* Initialize per scheduler queue node pool */
                alloc_status = SCHED_ALLOC_QNODE_POOL;
                new_sched->qnode_pool =
                        _qnode_pool_create("qnode pool", LTHREAD_PREALLOC);
                if (new_sched->qnode_pool == NULL)
                        break;

                /* Initialize per scheduler local ready queue */
                alloc_status = SCHED_ALLOC_READY_QUEUE;
                new_sched->ready = _lthread_queue_create("ready queue");
                if (new_sched->ready == NULL)
                        break;

                /* Initialize per scheduler local peer ready queue */
                alloc_status = SCHED_ALLOC_PREADY_QUEUE;
                new_sched->pready = _lthread_queue_create("pready queue");
                if (new_sched->pready == NULL)
                        break;

                /* Initialize per scheduler local free lthread cache */
                alloc_status = SCHED_ALLOC_LTHREAD_CACHE;
                new_sched->lthread_cache =
                        _lthread_objcache_create("lthread cache",
                                                sizeof(struct lthread),
                                                LTHREAD_PREALLOC);
                if (new_sched->lthread_cache == NULL)
                        break;

                /* Initialize per scheduler local free stack cache */
                alloc_status = SCHED_ALLOC_STACK_CACHE;
                new_sched->stack_cache =
                        _lthread_objcache_create("stack_cache",
                                                sizeof(struct lthread_stack),
                                                LTHREAD_PREALLOC);
                if (new_sched->stack_cache == NULL)
                        break;

                /* Initialize per scheduler local free per lthread data cache */
                alloc_status = SCHED_ALLOC_PERLT_CACHE;
                new_sched->per_lthread_cache =
                        _lthread_objcache_create("per_lt cache",
                                                RTE_PER_LTHREAD_SECTION_SIZE,
                                                LTHREAD_PREALLOC);
                if (new_sched->per_lthread_cache == NULL)
                        break;

                /* Initialize per scheduler local free tls cache */
                alloc_status = SCHED_ALLOC_TLS_CACHE;
                new_sched->tls_cache =
                        _lthread_objcache_create("TLS cache",
                                                sizeof(struct lthread_tls),
                                                LTHREAD_PREALLOC);
                if (new_sched->tls_cache == NULL)
                        break;

                /* Initialize per scheduler local free cond var cache */
                alloc_status = SCHED_ALLOC_COND_CACHE;
                new_sched->cond_cache =
                        _lthread_objcache_create("cond cache",
                                                sizeof(struct lthread_cond),
                                                LTHREAD_PREALLOC);
                if (new_sched->cond_cache == NULL)
                        break;

                /* Initialize per scheduler local free mutex cache */
                alloc_status = SCHED_ALLOC_MUTEX_CACHE;
                new_sched->mutex_cache =
                        _lthread_objcache_create("mutex cache",
                                                sizeof(struct lthread_mutex),
                                                LTHREAD_PREALLOC);
                if (new_sched->mutex_cache == NULL)
                        break;

                alloc_status = SCHED_ALLOC_OK;
        } while (0);

        /* roll back on any failure */
        switch (alloc_status) {
        case SCHED_ALLOC_MUTEX_CACHE:
                _lthread_objcache_destroy(new_sched->cond_cache);
                /* fall through */
        case SCHED_ALLOC_COND_CACHE:
                _lthread_objcache_destroy(new_sched->tls_cache);
                /* fall through */
        case SCHED_ALLOC_TLS_CACHE:
                _lthread_objcache_destroy(new_sched->per_lthread_cache);
                /* fall through */
        case SCHED_ALLOC_PERLT_CACHE:
                _lthread_objcache_destroy(new_sched->stack_cache);
                /* fall through */
        case SCHED_ALLOC_STACK_CACHE:
                _lthread_objcache_destroy(new_sched->lthread_cache);
                /* fall through */
        case SCHED_ALLOC_LTHREAD_CACHE:
                _lthread_queue_destroy(new_sched->pready);
                /* fall through */
        case SCHED_ALLOC_PREADY_QUEUE:
                _lthread_queue_destroy(new_sched->ready);
                /* fall through */
        case SCHED_ALLOC_READY_QUEUE:
                _qnode_pool_destroy(new_sched->qnode_pool);
                /* fall through */
        case SCHED_ALLOC_QNODE_POOL:
                /* fall through */
        case SCHED_ALLOC_OK:
                break;
        }
        return alloc_status;
}


/*
 * Create a scheduler on the current lcore
 */
struct lthread_sched *_lthread_sched_create(size_t stack_size)
{
        int status;
        struct lthread_sched *new_sched;
        unsigned lcoreid = rte_lcore_id();

        RTE_ASSERT(stack_size <= LTHREAD_MAX_STACK_SIZE);

        if (stack_size == 0)
                stack_size = LTHREAD_MAX_STACK_SIZE;

        new_sched =
             rte_calloc_socket(NULL, 1, sizeof(struct lthread_sched),
                                RTE_CACHE_LINE_SIZE,
                                rte_socket_id());
        if (new_sched == NULL) {
                RTE_LOG(CRIT, LTHREAD,
                        "Failed to allocate memory for scheduler\n");
                return NULL;
        }

        _lthread_key_pool_init();

        new_sched->stack_size = stack_size;
        new_sched->birth = rte_rdtsc();
        THIS_SCHED = new_sched;

        status = _lthread_sched_alloc_resources(new_sched);
        if (status != SCHED_ALLOC_OK) {
                RTE_LOG(CRIT, LTHREAD,
                        "Failed to allocate resources for scheduler code = %d\n",
                        status);
                rte_free(new_sched);
                return NULL;
        }

        bzero(&new_sched->ctx, sizeof(struct ctx));

        new_sched->lcore_id = lcoreid;

        schedcore[lcoreid] = new_sched;

        new_sched->run_flag = 1;

        DIAG_EVENT(new_sched, LT_DIAG_SCHED_CREATE, rte_lcore_id(), 0);

        rte_wmb();
        return new_sched;
}

/*
 * Set the number of schedulers in the system
 */
int lthread_num_schedulers_set(int num)
{
        rte_atomic16_set(&num_schedulers, num);
        return (int)rte_atomic16_read(&num_schedulers);
}

/*
 * Return the number of schedulers active
 */
int lthread_active_schedulers(void)
{
        return (int)rte_atomic16_read(&active_schedulers);
}


/**
 * shutdown the scheduler running on the specified lcore
 */
void lthread_scheduler_shutdown(unsigned lcoreid)
{
        uint64_t coreid = (uint64_t) lcoreid;

        if (coreid < LTHREAD_MAX_LCORES) {
                if (schedcore[coreid] != NULL)
                        schedcore[coreid]->run_flag = 0;
        }
}

/**
 * shutdown all schedulers
 */
void lthread_scheduler_shutdown_all(void)
{
        uint64_t i;

        /*
         * give time for all schedulers to have started
         * Note we use sched_yield() rather than pthread_yield() to allow
         * for the possibility of a pthread wrapper on lthread_yield(),
         * something that is not possible unless the scheduler is running.
         */
        while (rte_atomic16_read(&active_schedulers) <
               rte_atomic16_read(&num_schedulers))
                sched_yield();

        for (i = 0; i < LTHREAD_MAX_LCORES; i++) {
                if (schedcore[i] != NULL)
                        schedcore[i]->run_flag = 0;
        }
}

/*
 * Resume a suspended lthread
 */
static __rte_always_inline void
_lthread_resume(struct lthread *lt);
static inline void _lthread_resume(struct lthread *lt)
{
        struct lthread_sched *sched = THIS_SCHED;
        struct lthread_stack *s;
        uint64_t state = lt->state;
#if LTHREAD_DIAG
        int init = 0;
#endif

        sched->current_lthread = lt;

        if (state & (BIT(ST_LT_CANCELLED) | BIT(ST_LT_EXITED))) {
                /* if detached we can free the thread now */
                if (state & BIT(ST_LT_DETACH)) {
                        _lthread_free(lt);
                        sched->current_lthread = NULL;
                        return;
                }
        }

        if (state & BIT(ST_LT_INIT)) {
                /* first time this thread has been run */
                /* assign thread to this scheduler */
                lt->sched = THIS_SCHED;

                /* allocate stack */
                s = _stack_alloc();

                lt->stack_container = s;
                _lthread_set_stack(lt, s->stack, s->stack_size);

                /* allocate memory for TLS used by this thread */
                _lthread_tls_alloc(lt);

                lt->state = BIT(ST_LT_READY);
#if LTHREAD_DIAG
                init = 1;
#endif
        }

        DIAG_EVENT(lt, LT_DIAG_LTHREAD_RESUMED, init, lt);

        /* switch to the new thread */
        ctx_switch(&lt->ctx, &sched->ctx);

        /* If posting to a queue that could be read by another lcore
         * we defer the queue write till now to ensure the context has been
         * saved before the other core tries to resume it
         * This applies to blocking on mutex, cond, and to set_affinity
         */
        if (lt->pending_wr_queue != NULL) {
                struct lthread_queue *dest = lt->pending_wr_queue;

                lt->pending_wr_queue = NULL;

                /* queue the current thread to the specified queue */
                _lthread_queue_insert_mp(dest, lt);
        }

        sched->current_lthread = NULL;
}

/*
 * Handle sleep timer expiry
*/
void
_sched_timer_cb(struct rte_timer *tim, void *arg)
{
        struct lthread *lt = (struct lthread *) arg;
        uint64_t state = lt->state;

        DIAG_EVENT(lt, LT_DIAG_LTHREAD_TMR_EXPIRED, &lt->tim, 0);

        rte_timer_stop(tim);

        if (lt->state & BIT(ST_LT_CANCELLED))
                (THIS_SCHED)->nb_blocked_threads--;

        lt->state = state | BIT(ST_LT_EXPIRED);
        _lthread_resume(lt);
        lt->state = state & CLEARBIT(ST_LT_EXPIRED);
}



/*
 * Returns 0 if there is a pending job in scheduler or 1 if done and can exit.
 */
static inline int _lthread_sched_isdone(struct lthread_sched *sched)
{
        return (sched->run_flag == 0) &&
                        (_lthread_queue_empty(sched->ready)) &&
                        (_lthread_queue_empty(sched->pready)) &&
                        (sched->nb_blocked_threads == 0);
}

/*
 * Wait for all schedulers to start
 */
static inline void _lthread_schedulers_sync_start(void)
{
        rte_atomic16_inc(&active_schedulers);

        /* wait for lthread schedulers
         * Note we use sched_yield() rather than pthread_yield() to allow
         * for the possibility of a pthread wrapper on lthread_yield(),
         * something that is not possible unless the scheduler is running.
         */
        while (rte_atomic16_read(&active_schedulers) <
               rte_atomic16_read(&num_schedulers))
                sched_yield();

}

/*
 * Wait for all schedulers to stop
 */
static inline void _lthread_schedulers_sync_stop(void)
{
        rte_atomic16_dec(&active_schedulers);
        rte_atomic16_dec(&num_schedulers);

        /* wait for schedulers
         * Note we use sched_yield() rather than pthread_yield() to allow
         * for the possibility of a pthread wrapper on lthread_yield(),
         * something that is not possible unless the scheduler is running.
         */
        while (rte_atomic16_read(&active_schedulers) > 0)
                sched_yield();

}


/*
 * Run the lthread scheduler
 * This loop is the heart of the system
 */
void lthread_run(void)
{

        struct lthread_sched *sched = THIS_SCHED;
        struct lthread *lt = NULL;

        RTE_LOG(INFO, LTHREAD,
                "starting scheduler %p on lcore %u phys core %u\n",
                sched, rte_lcore_id(),
                rte_lcore_index(rte_lcore_id()));

        /* if more than one, wait for all schedulers to start */
        _lthread_schedulers_sync_start();


        /*
         * This is the main scheduling loop
         * So long as there are tasks in existence we run this loop.
         * We check for:-
         *   expired timers,
         *   the local ready queue,
         *   and the peer ready queue,
         *
         * and resume lthreads ad infinitum.
         */
        while (!_lthread_sched_isdone(sched)) {

                rte_timer_manage();

                lt = _lthread_queue_poll(sched->ready);
                if (lt != NULL)
                        _lthread_resume(lt);
                lt = _lthread_queue_poll(sched->pready);
                if (lt != NULL)
                        _lthread_resume(lt);
        }


        /* if more than one wait for all schedulers to stop */
        _lthread_schedulers_sync_stop();

        (THIS_SCHED) = NULL;

        RTE_LOG(INFO, LTHREAD,
                "stopping scheduler %p on lcore %u phys core %u\n",
                sched, rte_lcore_id(),
                rte_lcore_index(rte_lcore_id()));
        fflush(stdout);
}

/*
 * Return the scheduler for this lcore
 *
 */
struct lthread_sched *_lthread_sched_get(unsigned int lcore_id)
{
        struct lthread_sched *res = NULL;

        if (lcore_id < LTHREAD_MAX_LCORES)
                res = schedcore[lcore_id];

        return res;
}

/*
 * migrate the current thread to another scheduler running
 * on the specified lcore.
 */
int lthread_set_affinity(unsigned lcoreid)
{
        struct lthread *lt = THIS_LTHREAD;
        struct lthread_sched *dest_sched;

        if (unlikely(lcoreid >= LTHREAD_MAX_LCORES))
                return POSIX_ERRNO(EINVAL);

        DIAG_EVENT(lt, LT_DIAG_LTHREAD_AFFINITY, lcoreid, 0);

        dest_sched = schedcore[lcoreid];

        if (unlikely(dest_sched == NULL))
                return POSIX_ERRNO(EINVAL);

        if (likely(dest_sched != THIS_SCHED)) {
                lt->sched = dest_sched;
                lt->pending_wr_queue = dest_sched->pready;
                _affinitize();
                return 0;
        }
        return 0;
}