/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2005 David Xu <davidxu@freebsd.org>
 * Copyright (C) 2003 Daniel M. Eischen <deischen@freebsd.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice unmodified, this list of conditions, and the following
 *    disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <sys/types.h>
#include <sys/queue.h>

#include <machine/tls.h>

#include <stdlib.h>
#include <string.h>
#include <pthread.h>

#include "libc_private.h"
#include "thr_private.h"

/*#define DEBUG_THREAD_LIST */
#ifdef DEBUG_THREAD_LIST
#define DBG_MSG         stdout_debug
#else
#define DBG_MSG(x...)
#endif

#define MAX_THREADS             100000

/*
 * Define a high water mark for the maximum number of threads that
 * will be cached.  Once this level is reached, any extra threads
 * will be free()'d.
 */
#define MAX_CACHED_THREADS      100

/*
 * We've got to keep track of everything that is allocated, not only
 * to have a speedy free list, but also so they can be deallocated
 * after a fork().
 */
static TAILQ_HEAD(, pthread)    free_threadq;
static struct umutex            free_thread_lock = DEFAULT_UMUTEX;
static struct umutex            tcb_lock = DEFAULT_UMUTEX;
static int                      free_thread_count = 0;
static int                      inited = 0;
static int                      total_threads;

LIST_HEAD(thread_hash_head, pthread);
#define HASH_QUEUES     128
static struct thread_hash_head  thr_hashtable[HASH_QUEUES];
#define THREAD_HASH(thrd)       (((unsigned long)thrd >> 8) % HASH_QUEUES)

static void thr_destroy(struct pthread *curthread, struct pthread *thread);

void
_thr_list_init(void)
{
        int i;

        _gc_count = 0;
        total_threads = 1;
        _thr_urwlock_init(&_thr_list_lock);
        TAILQ_INIT(&_thread_list);
        TAILQ_INIT(&free_threadq);
        _thr_umutex_init(&free_thread_lock);
        _thr_umutex_init(&tcb_lock);
        if (inited) {
                for (i = 0; i < HASH_QUEUES; ++i)
                        LIST_INIT(&thr_hashtable[i]);
        }
        inited = 1;
}

void
_thr_gc(struct pthread *curthread)
{
        struct pthread *td, *td_next;
        TAILQ_HEAD(, pthread) worklist;

        TAILQ_INIT(&worklist);
        THREAD_LIST_WRLOCK(curthread);

        /* Check the threads waiting for GC. */
        TAILQ_FOREACH_SAFE(td, &_thread_gc_list, gcle, td_next) {
                if (td->tid != TID_TERMINATED) {
                        /* make sure we are not still in userland */
                        continue;
                }
                _thr_stack_free(&td->attr);
                THR_GCLIST_REMOVE(td);
                TAILQ_INSERT_HEAD(&worklist, td, gcle);
        }
        THREAD_LIST_UNLOCK(curthread);

        while ((td = TAILQ_FIRST(&worklist)) != NULL) {
                TAILQ_REMOVE(&worklist, td, gcle);
                /*
                 * XXX we don't free initial thread, because there might
                 * have some code referencing initial thread.
                 */
                if (td == _thr_initial) {
                        DBG_MSG("Initial thread won't be freed\n");
                        continue;
                }

                _thr_free(curthread, td);
        }
}

struct pthread *
_thr_alloc(struct pthread *curthread)
{
        struct pthread  *thread = NULL;
        struct tcb      *tcb;

        if (curthread != NULL) {
                if (GC_NEEDED())
                        _thr_gc(curthread);
                if (free_thread_count > 0) {
                        THR_LOCK_ACQUIRE(curthread, &free_thread_lock);
                        if ((thread = TAILQ_FIRST(&free_threadq)) != NULL) {
                                TAILQ_REMOVE(&free_threadq, thread, tle);
                                free_thread_count--;
                        }
                        THR_LOCK_RELEASE(curthread, &free_thread_lock);
                }
        }
        if (thread == NULL) {
                if (total_threads > MAX_THREADS)
                        return (NULL);
                atomic_add_int(&total_threads, 1);
                thread = __thr_aligned_alloc_offset(_Alignof(struct pthread),
                    sizeof(struct pthread), 0);
                if (thread == NULL) {
                        atomic_add_int(&total_threads, -1);
                        return (NULL);
                }
                memset(thread, 0, sizeof(*thread));
                if ((thread->sleepqueue = _sleepq_alloc()) == NULL ||
                    (thread->wake_addr = _thr_alloc_wake_addr()) == NULL) {
                        thr_destroy(curthread, thread);
                        atomic_add_int(&total_threads, -1);
                        return (NULL);
                }
        } else {
                bzero(&thread->_pthread_startzero, 
                        __rangeof(struct pthread, _pthread_startzero, _pthread_endzero));
        }
        if (curthread != NULL) {
                THR_LOCK_ACQUIRE(curthread, &tcb_lock);
                tcb = _tcb_ctor(thread, 0 /* not initial tls */);
                THR_LOCK_RELEASE(curthread, &tcb_lock);
        } else {
                tcb = _tcb_ctor(thread, 1 /* initial tls */);
        }
        if (tcb != NULL) {
                thread->tcb = tcb;
        } else {
                thr_destroy(curthread, thread);
                atomic_add_int(&total_threads, -1);
                thread = NULL;
        }
        return (thread);
}

void
_thr_free(struct pthread *curthread, struct pthread *thread)
{
        DBG_MSG("Freeing thread %p\n", thread);

        /*
         * Always free tcb, as we only know it is part of RTLD TLS
         * block, but don't know its detail and can not assume how
         * it works, so better to avoid caching it here.
         */
        if (curthread != NULL) {
                THR_LOCK_ACQUIRE(curthread, &tcb_lock);
                _tcb_dtor(thread->tcb);
                THR_LOCK_RELEASE(curthread, &tcb_lock);
        } else {
                _tcb_dtor(thread->tcb);
        }
        thread->tcb = NULL;
        if ((curthread == NULL) || (free_thread_count >= MAX_CACHED_THREADS)) {
                thr_destroy(curthread, thread);
                atomic_add_int(&total_threads, -1);
        } else {
                /*
                 * Add the thread to the free thread list, this also avoids
                 * pthread id is reused too quickly, may help some buggy apps.
                 */
                THR_LOCK_ACQUIRE(curthread, &free_thread_lock);
                TAILQ_INSERT_TAIL(&free_threadq, thread, tle);
                free_thread_count++;
                THR_LOCK_RELEASE(curthread, &free_thread_lock);
        }
}

static void
thr_destroy(struct pthread *curthread __unused, struct pthread *thread)
{
        if (thread->sleepqueue != NULL)
                _sleepq_free(thread->sleepqueue);
        if (thread->wake_addr != NULL)
                _thr_release_wake_addr(thread->wake_addr);
        __thr_free(thread);
}

/*
 * Add the thread to the list of all threads and increment
 * number of active threads.
 */
void
_thr_link(struct pthread *curthread, struct pthread *thread)
{
        THREAD_LIST_WRLOCK(curthread);
        THR_LIST_ADD(thread);
        THREAD_LIST_UNLOCK(curthread);
        atomic_add_int(&_thread_active_threads, 1);
}

/*
 * Remove an active thread.
 */
void
_thr_unlink(struct pthread *curthread, struct pthread *thread)
{
        THREAD_LIST_WRLOCK(curthread);
        THR_LIST_REMOVE(thread);
        THREAD_LIST_UNLOCK(curthread);
        atomic_add_int(&_thread_active_threads, -1);
}

void
_thr_hash_add(struct pthread *thread)
{
        struct thread_hash_head *head;

        head = &thr_hashtable[THREAD_HASH(thread)];
        LIST_INSERT_HEAD(head, thread, hle);
}

void
_thr_hash_remove(struct pthread *thread)
{
        LIST_REMOVE(thread, hle);
}

struct pthread *
_thr_hash_find(struct pthread *thread)
{
        struct pthread *td;
        struct thread_hash_head *head;

        head = &thr_hashtable[THREAD_HASH(thread)];
        LIST_FOREACH(td, head, hle) {
                if (td == thread)
                        return (thread);
        }
        return (NULL);
}

/*
 * Find a thread in the linked list of active threads and add a reference
 * to it.  Threads with positive reference counts will not be deallocated
 * until all references are released.
 */
int
_thr_ref_add(struct pthread *curthread, struct pthread *thread,
    int include_dead)
{
        int ret;

        if (thread == NULL)
                /* Invalid thread: */
                return (EINVAL);

        if ((ret = _thr_find_thread(curthread, thread, include_dead)) == 0) {
                thread->refcount++;
                THR_CRITICAL_ENTER(curthread);
                THR_THREAD_UNLOCK(curthread, thread);
        }

        /* Return zero if the thread exists: */
        return (ret);
}

void
_thr_ref_delete(struct pthread *curthread, struct pthread *thread)
{
        THR_THREAD_LOCK(curthread, thread);
        thread->refcount--;
        _thr_try_gc(curthread, thread);
        THR_CRITICAL_LEAVE(curthread);
}

/* entered with thread lock held, exit with thread lock released */
void
_thr_try_gc(struct pthread *curthread, struct pthread *thread)
{
        if (THR_SHOULD_GC(thread)) {
                THR_REF_ADD(curthread, thread);
                THR_THREAD_UNLOCK(curthread, thread);
                THREAD_LIST_WRLOCK(curthread);
                THR_THREAD_LOCK(curthread, thread);
                THR_REF_DEL(curthread, thread);
                if (THR_SHOULD_GC(thread)) {
                        THR_LIST_REMOVE(thread);
                        THR_GCLIST_ADD(thread);
                }
                THR_THREAD_UNLOCK(curthread, thread);
                THREAD_LIST_UNLOCK(curthread);
        } else {
                THR_THREAD_UNLOCK(curthread, thread);
        }
}

/* return with thread lock held if thread is found */
int
_thr_find_thread(struct pthread *curthread, struct pthread *thread,
    int include_dead)
{
        struct pthread *pthread;
        int ret;

        if (thread == NULL)
                return (EINVAL);

        ret = 0;
        THREAD_LIST_RDLOCK(curthread);
        pthread = _thr_hash_find(thread);
        if (pthread) {
                THR_THREAD_LOCK(curthread, pthread);
                if (include_dead == 0 && pthread->state == PS_DEAD) {
                        THR_THREAD_UNLOCK(curthread, pthread);
                        ret = ESRCH;
                }
        } else {
                ret = ESRCH;
        }
        THREAD_LIST_UNLOCK(curthread);
        return (ret);
}