/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2005 David Xu <davidxu@freebsd.org>
 * Copyright (c) 2015 The FreeBSD Foundation
 * All rights reserved.
 *
 * Portions of this software were developed by Konstantin Belousov
 * under sponsorship from the FreeBSD Foundation.
 *
 * 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 "namespace.h"
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <pthread.h>
#include <limits.h>
#include "un-namespace.h"

#include "thr_private.h"

_Static_assert(sizeof(struct pthread_cond) <= THR_PAGE_SIZE_MIN,
    "pthread_cond too large");

/*
 * Prototypes
 */
int     __pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex,
                       const struct timespec * abstime);
static int cond_init(pthread_cond_t *cond, const pthread_condattr_t *attr);
static int cond_wait_common(pthread_cond_t *cond, pthread_mutex_t *mutex,
                    const struct timespec *abstime, int cancel);
static int cond_signal_common(pthread_cond_t *cond);
static int cond_broadcast_common(pthread_cond_t *cond);

/*
 * Double underscore versions are cancellation points.  Single underscore
 * versions are not and are provided for libc internal usage (which
 * shouldn't introduce cancellation points).
 */
__weak_reference(__thr_cond_wait, pthread_cond_wait);
__weak_reference(__thr_cond_wait, __pthread_cond_wait);
__weak_reference(_thr_cond_wait, _pthread_cond_wait);
__weak_reference(__pthread_cond_timedwait, pthread_cond_timedwait);
__weak_reference(_thr_cond_timedwait, _pthread_cond_timedwait);
__weak_reference(_thr_cond_init, pthread_cond_init);
__weak_reference(_thr_cond_init, _pthread_cond_init);
__weak_reference(_thr_cond_destroy, pthread_cond_destroy);
__weak_reference(_thr_cond_destroy, _pthread_cond_destroy);
__weak_reference(_thr_cond_signal, pthread_cond_signal);
__weak_reference(_thr_cond_signal, _pthread_cond_signal);
__weak_reference(_thr_cond_broadcast, pthread_cond_broadcast);
__weak_reference(_thr_cond_broadcast, _pthread_cond_broadcast);

#define CV_PSHARED(cvp) (((cvp)->kcond.c_flags & USYNC_PROCESS_SHARED) != 0)

static void
cond_init_body(struct pthread_cond *cvp, const struct pthread_cond_attr *cattr)
{

        if (cattr == NULL) {
                cvp->kcond.c_clockid = CLOCK_REALTIME;
        } else {
                if (cattr->c_pshared)
                        cvp->kcond.c_flags |= USYNC_PROCESS_SHARED;
                cvp->kcond.c_clockid = cattr->c_clockid;
        }
}

static int
cond_init(pthread_cond_t *cond, const pthread_condattr_t *cond_attr)
{
        struct pthread_cond *cvp;
        const struct pthread_cond_attr *cattr;
        int pshared;

        cattr = cond_attr != NULL ? *cond_attr : NULL;
        if (cattr == NULL || cattr->c_pshared == PTHREAD_PROCESS_PRIVATE) {
                pshared = 0;
                cvp = calloc(1, sizeof(struct pthread_cond));
                if (cvp == NULL)
                        return (ENOMEM);
        } else {
                pshared = 1;
                cvp = __thr_pshared_offpage(cond, 1);
                if (cvp == NULL)
                        return (EFAULT);
        }

        /*
         * Initialise the condition variable structure:
         */
        cond_init_body(cvp, cattr);
        *cond = pshared ? THR_PSHARED_PTR : cvp;
        return (0);
}

static int
init_static(struct pthread *thread, pthread_cond_t *cond)
{
        int ret;

        THR_LOCK_ACQUIRE(thread, &_cond_static_lock);

        if (*cond == NULL)
                ret = cond_init(cond, NULL);
        else
                ret = 0;

        THR_LOCK_RELEASE(thread, &_cond_static_lock);

        return (ret);
}

#define CHECK_AND_INIT_COND                                                     \
        if (*cond == THR_PSHARED_PTR) {                                         \
                cvp = __thr_pshared_offpage(cond, 0);                           \
                if (cvp == NULL)                                                \
                        return (EINVAL);                                        \
        } else if (__predict_false((cvp = (*cond)) <= THR_COND_DESTROYED)) {    \
                if (cvp == THR_COND_INITIALIZER) {                              \
                        int ret;                                                \
                        ret = init_static(_get_curthread(), cond);              \
                        if (ret)                                                \
                                return (ret);                                   \
                } else if (cvp == THR_COND_DESTROYED) {                         \
                        return (EINVAL);                                        \
                }                                                               \
                cvp = *cond;                                                    \
        }

int
_thr_cond_init(pthread_cond_t * __restrict cond,
    const pthread_condattr_t * __restrict cond_attr)
{

        *cond = NULL;
        return (cond_init(cond, cond_attr));
}

int
_thr_cond_destroy(pthread_cond_t *cond)
{
        struct pthread_cond *cvp;
        int error;

        error = 0;
        if (*cond == THR_PSHARED_PTR) {
                cvp = __thr_pshared_offpage(cond, 0);
                if (cvp != NULL) {
                        if (cvp->kcond.c_has_waiters)
                                error = EBUSY;
                        else
                                __thr_pshared_destroy(cond);
                }
                if (error == 0)
                        *cond = THR_COND_DESTROYED;
        } else if ((cvp = *cond) == THR_COND_INITIALIZER) {
                /* nothing */
        } else if (cvp == THR_COND_DESTROYED) {
                error = EINVAL;
        } else {
                cvp = *cond;
                if (cvp->__has_user_waiters || cvp->kcond.c_has_waiters)
                        error = EBUSY;
                else {
                        *cond = THR_COND_DESTROYED;
                        free(cvp);
                }
        }
        return (error);
}

/*
 * Cancellation behavior:
 *   Thread may be canceled at start, if thread is canceled, it means it
 *   did not get a wakeup from pthread_cond_signal(), otherwise, it is
 *   not canceled.
 *   Thread cancellation never cause wakeup from pthread_cond_signal()
 *   to be lost.
 */
static int
cond_wait_kernel(struct pthread_cond *cvp, struct pthread_mutex *mp,
    const struct timespec *abstime, int cancel)
{
        struct pthread *curthread;
        int error, error2, recurse, robust;

        curthread = _get_curthread();
        robust = _mutex_enter_robust(curthread, mp);

        error = _mutex_cv_detach(mp, &recurse);
        if (error != 0) {
                if (robust)
                        _mutex_leave_robust(curthread, mp);
                return (error);
        }

        if (cancel)
                _thr_cancel_enter2(curthread, 0);
        error = _thr_ucond_wait(&cvp->kcond, &mp->m_lock, abstime,
            CVWAIT_ABSTIME | CVWAIT_CLOCKID);
        if (cancel)
                _thr_cancel_leave(curthread, 0);

        /*
         * Note that PP mutex and ROBUST mutex may return
         * interesting error codes.
         */
        if (error == 0) {
                error2 = _mutex_cv_lock(mp, recurse, true);
        } else if (error == EINTR || error == ETIMEDOUT) {
                error2 = _mutex_cv_lock(mp, recurse, true);
                /*
                 * Do not do cancellation on EOWNERDEAD there.  The
                 * cancellation cleanup handler will use the protected
                 * state and unlock the mutex without making the state
                 * consistent and the state will be unrecoverable.
                 */
                if (error2 == 0 && cancel) {
                        if (robust) {
                                _mutex_leave_robust(curthread, mp);
                                robust = false;
                        }
                        _thr_testcancel(curthread);
                }

                if (error == EINTR)
                        error = 0;
        } else {
                /* We know that it didn't unlock the mutex. */
                _mutex_cv_attach(mp, recurse);
                if (cancel) {
                        if (robust) {
                                _mutex_leave_robust(curthread, mp);
                                robust = false;
                        }
                        _thr_testcancel(curthread);
                }
                error2 = 0;
        }
        if (robust)
                _mutex_leave_robust(curthread, mp);
        return (error2 != 0 ? error2 : error);
}

/*
 * Thread waits in userland queue whenever possible, when thread
 * is signaled or broadcasted, it is removed from the queue, and
 * is saved in curthread's defer_waiters[] buffer, but won't be
 * woken up until mutex is unlocked.
 */

static int
cond_wait_user(struct pthread_cond *cvp, struct pthread_mutex *mp,
    const struct timespec *abstime, int cancel)
{
        struct pthread *curthread;
        struct sleepqueue *sq;
        int deferred, error, error2, recurse;

        curthread = _get_curthread();
        if (curthread->wchan != NULL)
                PANIC("thread %p was already on queue.", curthread);

        if (cancel)
                _thr_testcancel(curthread);

        _sleepq_lock(cvp);
        /*
         * set __has_user_waiters before unlocking mutex, this allows
         * us to check it without locking in pthread_cond_signal().
         */
        cvp->__has_user_waiters = 1; 
        deferred = 0;
        (void)_mutex_cv_unlock(mp, &recurse, &deferred);
        curthread->mutex_obj = mp;
        _sleepq_add(cvp, curthread);
        for(;;) {
                _thr_clear_wake(curthread);
                _sleepq_unlock(cvp);
                if (deferred) {
                        deferred = 0;
                        if ((mp->m_lock.m_owner & UMUTEX_CONTESTED) == 0)
                                (void)_umtx_op_err(&mp->m_lock,
                                    UMTX_OP_MUTEX_WAKE2, mp->m_lock.m_flags,
                                    0, 0);
                }
                if (curthread->nwaiter_defer > 0) {
                        _thr_wake_all(curthread->defer_waiters,
                            curthread->nwaiter_defer);
                        curthread->nwaiter_defer = 0;
                }

                if (cancel)
                        _thr_cancel_enter2(curthread, 0);
                error = _thr_sleep(curthread, cvp->kcond.c_clockid, abstime);
                if (cancel)
                        _thr_cancel_leave(curthread, 0);

                _sleepq_lock(cvp);
                if (curthread->wchan == NULL) {
                        error = 0;
                        break;
                } else if (cancel && SHOULD_CANCEL(curthread)) {
                        sq = _sleepq_lookup(cvp);
                        cvp->__has_user_waiters = _sleepq_remove(sq, curthread);
                        _sleepq_unlock(cvp);
                        curthread->mutex_obj = NULL;
                        error2 = _mutex_cv_lock(mp, recurse, false);
                        if (!THR_IN_CRITICAL(curthread))
                                _pthread_exit(PTHREAD_CANCELED);
                        else /* this should not happen */
                                return (error2);
                } else if (error == ETIMEDOUT) {
                        sq = _sleepq_lookup(cvp);
                        cvp->__has_user_waiters =
                            _sleepq_remove(sq, curthread);
                        break;
                }
        }
        _sleepq_unlock(cvp);
        curthread->mutex_obj = NULL;
        error2 = _mutex_cv_lock(mp, recurse, false);
        if (error == 0)
                error = error2;
        return (error);
}

static int
cond_wait_common(pthread_cond_t *cond, pthread_mutex_t *mutex,
        const struct timespec *abstime, int cancel)
{
        struct pthread  *curthread = _get_curthread();
        struct pthread_cond *cvp;
        struct pthread_mutex *mp;
        int     error;

        CHECK_AND_INIT_COND

        if (*mutex == THR_PSHARED_PTR) {
                mp = __thr_pshared_offpage(mutex, 0);
                if (mp == NULL)
                        return (EINVAL);
        } else {
                mp = *mutex;
        }

        if ((error = _mutex_owned(curthread, mp)) != 0)
                return (error);

        if (curthread->attr.sched_policy != SCHED_OTHER ||
            (mp->m_lock.m_flags & (UMUTEX_PRIO_PROTECT | UMUTEX_PRIO_INHERIT |
            USYNC_PROCESS_SHARED)) != 0 || CV_PSHARED(cvp))
                return (cond_wait_kernel(cvp, mp, abstime, cancel));
        else
                return (cond_wait_user(cvp, mp, abstime, cancel));
}

int
_thr_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
{

        return (cond_wait_common(cond, mutex, NULL, 0));
}

int
__thr_cond_wait(pthread_cond_t * __restrict cond,
    pthread_mutex_t * __restrict mutex)
{

        return (cond_wait_common(cond, mutex, NULL, 1));
}

int
_thr_cond_timedwait(pthread_cond_t * __restrict cond,
    pthread_mutex_t * __restrict mutex,
    const struct timespec * __restrict abstime)
{

        if (abstime == NULL || abstime->tv_sec < 0 || abstime->tv_nsec < 0 ||
            abstime->tv_nsec >= 1000000000)
                return (EINVAL);

        return (cond_wait_common(cond, mutex, abstime, 0));
}

int
__pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex,
                       const struct timespec *abstime)
{

        if (abstime == NULL || abstime->tv_sec < 0 || abstime->tv_nsec < 0 ||
            abstime->tv_nsec >= 1000000000)
                return (EINVAL);

        return (cond_wait_common(cond, mutex, abstime, 1));
}

static int
cond_signal_common(pthread_cond_t *cond)
{
        struct pthread  *curthread = _get_curthread();
        struct pthread *td;
        struct pthread_cond *cvp;
        struct pthread_mutex *mp;
        struct sleepqueue *sq;
        int     *waddr;
        int     pshared;

        /*
         * If the condition variable is statically initialized, perform dynamic
         * initialization.
         */
        CHECK_AND_INIT_COND

        pshared = CV_PSHARED(cvp);

        _thr_ucond_signal(&cvp->kcond);

        if (pshared || cvp->__has_user_waiters == 0)
                return (0);

        curthread = _get_curthread();
        waddr = NULL;
        _sleepq_lock(cvp);
        sq = _sleepq_lookup(cvp);
        if (sq == NULL) {
                _sleepq_unlock(cvp);
                return (0);
        }

        td = _sleepq_first(sq);
        mp = td->mutex_obj;
        cvp->__has_user_waiters = _sleepq_remove(sq, td);
        if (PMUTEX_OWNER_ID(mp) == TID(curthread)) {
                if (curthread->nwaiter_defer >= MAX_DEFER_WAITERS) {
                        _thr_wake_all(curthread->defer_waiters,
                            curthread->nwaiter_defer);
                        curthread->nwaiter_defer = 0;
                }
                curthread->defer_waiters[curthread->nwaiter_defer++] =
                    &td->wake_addr->value;
                mp->m_flags |= PMUTEX_FLAG_DEFERRED;
        } else {
                waddr = &td->wake_addr->value;
        }
        _sleepq_unlock(cvp);
        if (waddr != NULL)
                _thr_set_wake(waddr);
        return (0);
}

struct broadcast_arg {
        struct pthread *curthread;
        unsigned int *waddrs[MAX_DEFER_WAITERS];
        int count;
};

static void
drop_cb(struct pthread *td, void *arg)
{
        struct broadcast_arg *ba = arg;
        struct pthread_mutex *mp;
        struct pthread *curthread = ba->curthread;

        mp = td->mutex_obj;
        if (PMUTEX_OWNER_ID(mp) == TID(curthread)) {
                if (curthread->nwaiter_defer >= MAX_DEFER_WAITERS) {
                        _thr_wake_all(curthread->defer_waiters,
                            curthread->nwaiter_defer);
                        curthread->nwaiter_defer = 0;
                }
                curthread->defer_waiters[curthread->nwaiter_defer++] =
                    &td->wake_addr->value;
                mp->m_flags |= PMUTEX_FLAG_DEFERRED;
        } else {
                if (ba->count >= MAX_DEFER_WAITERS) {
                        _thr_wake_all(ba->waddrs, ba->count);
                        ba->count = 0;
                }
                ba->waddrs[ba->count++] = &td->wake_addr->value;
        }
}

static int
cond_broadcast_common(pthread_cond_t *cond)
{
        int    pshared;
        struct pthread_cond *cvp;
        struct sleepqueue *sq;
        struct broadcast_arg ba;

        /*
         * If the condition variable is statically initialized, perform dynamic
         * initialization.
         */
        CHECK_AND_INIT_COND

        pshared = CV_PSHARED(cvp);

        _thr_ucond_broadcast(&cvp->kcond);

        if (pshared || cvp->__has_user_waiters == 0)
                return (0);

        ba.curthread = _get_curthread();
        ba.count = 0;
        
        _sleepq_lock(cvp);
        sq = _sleepq_lookup(cvp);
        if (sq == NULL) {
                _sleepq_unlock(cvp);
                return (0);
        }
        _sleepq_drop(sq, drop_cb, &ba);
        cvp->__has_user_waiters = 0;
        _sleepq_unlock(cvp);
        if (ba.count > 0)
                _thr_wake_all(ba.waddrs, ba.count);
        return (0);
}

int
_thr_cond_signal(pthread_cond_t * cond)
{

        return (cond_signal_common(cond));
}

int
_thr_cond_broadcast(pthread_cond_t * cond)
{

        return (cond_broadcast_common(cond));
}