/*      $NetBSD: pthread_cond.c,v 1.79 2026/05/06 09:03:49 yamt Exp $   */

/*-
 * Copyright (c) 2001, 2006, 2007, 2008, 2020 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Nathan J. Williams and Andrew Doran.
 *
 * 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, 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 NETBSD FOUNDATION, INC. AND CONTRIBUTORS
 * ``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 FOUNDATION OR CONTRIBUTORS
 * 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/cdefs.h>
__RCSID("$NetBSD: pthread_cond.c,v 1.79 2026/05/06 09:03:49 yamt Exp $");

/* Need to use libc-private names for atomic operations. */
#include "../../common/lib/libc/atomic/atomic_op_namespace.h"

#include <stdatomic.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/time.h>
#include <sys/types.h>

#include "pthread.h"
#include "pthread_int.h"
#include "reentrant.h"

#define atomic_load_relaxed(p)                                                \
        atomic_load_explicit(p, memory_order_relaxed)

int     _sys___nanosleep50(const struct timespec *, struct timespec *);

int     _pthread_cond_has_waiters_np(pthread_cond_t *);

__weak_alias(pthread_cond_has_waiters_np,_pthread_cond_has_waiters_np)

__strong_alias(__libc_cond_init,pthread_cond_init)
__strong_alias(__libc_cond_signal,pthread_cond_signal)
__strong_alias(__libc_cond_broadcast,pthread_cond_broadcast)
__strong_alias(__libc_cond_wait,pthread_cond_wait)
__strong_alias(__libc_cond_timedwait,pthread_cond_timedwait)
__strong_alias(__libc_cond_destroy,pthread_cond_destroy)

/*
 * A dummy waiter that's used to flag that pthread_cond_signal() is in
 * progress and nobody else should try to modify the waiter list until
 * it completes.
 */
#define pthread__cond_dummy_ptr ((struct pthread__waiter *)1)

static clockid_t
pthread_cond_getclock(const pthread_cond_t *cond)
{

        pthread__error(EINVAL, "Invalid condition variable",
            cond->ptc_magic == _PT_COND_MAGIC);

        return cond->ptc_private ?
            *(clockid_t *)cond->ptc_private : CLOCK_REALTIME;
}

int
pthread_cond_init(pthread_cond_t *cond, const pthread_condattr_t *attr)
{
        if (__predict_false(__uselibcstub))
                return __libc_cond_init_stub(cond, attr);

        pthread__error(EINVAL, "Invalid condition variable attribute",
            (attr == NULL) || (attr->ptca_magic == _PT_CONDATTR_MAGIC));

        cond->ptc_magic = _PT_COND_MAGIC;
        cond->ptc_waiters = NULL;
        cond->ptc_mutex = NULL;
        if (attr && attr->ptca_private) {
                cond->ptc_private = malloc(sizeof(clockid_t));
                if (cond->ptc_private == NULL)
                        return errno;
                *(clockid_t *)cond->ptc_private =
                    *(clockid_t *)attr->ptca_private;
        } else
                cond->ptc_private = NULL;

        return 0;
}


int
pthread_cond_destroy(pthread_cond_t *cond)
{
        if (__predict_false(__uselibcstub))
                return __libc_cond_destroy_stub(cond);

        pthread__error(EINVAL, "Invalid condition variable",
            cond->ptc_magic == _PT_COND_MAGIC);
        pthread__error(EBUSY, "Destroying condition variable in use",
            cond->ptc_waiters == NULL);

        cond->ptc_magic = _PT_COND_DEAD;
        free(cond->ptc_private);

        return 0;
}

int
pthread_cond_timedwait(pthread_cond_t *cond, pthread_mutex_t *mutex,
                       const struct timespec *abstime)
{
        struct pthread__waiter waiter, *next, *head;
        pthread_t self;
        int error, cancel;
        clockid_t clkid = pthread_cond_getclock(cond);

        if (__predict_false(__uselibcstub))
                return __libc_cond_timedwait_stub(cond, mutex, abstime);

        pthread__error(EINVAL, "Invalid condition variable",
            cond->ptc_magic == _PT_COND_MAGIC);
        pthread__error(EINVAL, "Invalid mutex",
            mutex->ptm_magic == _PT_MUTEX_MAGIC);
        pthread__error(EPERM, "Mutex not locked in condition wait",
            mutex->ptm_owner != NULL);

        self = pthread__self();
        pthread__assert(self->pt_lid != 0);

        if (__predict_false(atomic_load_relaxed(&self->pt_cancel) &
                PT_CANCEL_CANCELLED)) {
                membar_acquire();
                pthread__cancelled();
        }

        /* Note this thread as waiting on the CV. */
        cond->ptc_mutex = mutex;
        for (head = cond->ptc_waiters;; head = next) {
                /* Wait while pthread_cond_signal() in progress. */
                if (__predict_false(head == pthread__cond_dummy_ptr)) {
                        sched_yield();
                        next = cond->ptc_waiters;
                        continue;
                }
                waiter.lid = self->pt_lid;
                waiter.next = head;
#ifndef PTHREAD__ATOMIC_IS_MEMBAR
                membar_producer();
#endif
                next = atomic_cas_ptr(&cond->ptc_waiters, head, &waiter);
                if (__predict_true(next == head)) {
                        break;
                }
        }

        /* Drop the interlock and wait. */
        error = 0;
        pthread_mutex_unlock(mutex);
        while (waiter.lid &&
            !(cancel = atomic_load_relaxed(&self->pt_cancel) &
                PT_CANCEL_CANCELLED)) {
                int rv = _lwp_park(clkid, TIMER_ABSTIME, __UNCONST(abstime),
                    0, NULL, NULL);
                if (rv == 0) {
                        continue;
                }
                if (errno != EINTR && errno != EALREADY) {
                        error = errno;
                        break;
                }
        }
        pthread_mutex_lock(mutex);

        /*
         * If this thread absorbed a wakeup from pthread_cond_signal() and
         * cannot take the wakeup, we should ensure that another thread does.
         *
         * And if awoken early, we may still be on the waiter list and must
         * remove self.
         */
        if (__predict_false(cancel | error)) {
                pthread_cond_broadcast(cond);

                /*
                 * Might have raced with another thread to do the wakeup.
                 * Wait until released, otherwise "waiter" is still globally
                 * visible.
                 */
                pthread_mutex_unlock(mutex);
                while (__predict_false(waiter.lid)) {
                        (void)_lwp_park(CLOCK_MONOTONIC, 0, NULL, 0, NULL,
                            NULL);
                }
                pthread_mutex_lock(mutex);
        } else {
                pthread__assert(!waiter.lid);
        }

        /*
         * If cancelled then exit.  POSIX dictates that the mutex must be
         * held if this happens.
         */
        if (cancel) {
                membar_acquire();
                pthread__cancelled();
        }

        return error;
}

int
pthread_cond_wait(pthread_cond_t *cond, pthread_mutex_t *mutex)
{
        if (__predict_false(__uselibcstub))
                return __libc_cond_wait_stub(cond, mutex);

        return pthread_cond_timedwait(cond, mutex, NULL);
}

int
pthread_cond_signal(pthread_cond_t *cond)
{
        struct pthread__waiter *head, *next;
        pthread_mutex_t *mutex;
        pthread_t self;

        if (__predict_false(__uselibcstub))
                return __libc_cond_signal_stub(cond);

        pthread__error(EINVAL, "Invalid condition variable",
            cond->ptc_magic == _PT_COND_MAGIC);

        /* Take ownership of one waiter. */
        self = pthread_self();
        mutex = cond->ptc_mutex;
        for (head = cond->ptc_waiters;; head = next) {
                /* Wait while pthread_cond_signal() in progress. */
                if (__predict_false(head == pthread__cond_dummy_ptr)) {
                        sched_yield();
                        next = cond->ptc_waiters;
                        continue;
                }
                if (head == NULL) {
                        return 0;
                }
                /* Block concurrent access to the waiter list. */
                next = atomic_cas_ptr(&cond->ptc_waiters, head,
                    pthread__cond_dummy_ptr);
                if (__predict_true(next == head)) {
                        break;
                }
        }

        /* Now that list is locked, read pointer to next and then unlock. */
        membar_enter();
        cond->ptc_waiters = head->next;
        membar_producer();
        head->next = NULL;

        /* Now transfer waiter to the mutex. */
        pthread__mutex_deferwake(self, mutex, head);
        return 0;
}

int
pthread_cond_broadcast(pthread_cond_t *cond)
{
        struct pthread__waiter *head, *next;
        pthread_mutex_t *mutex;
        pthread_t self;

        if (__predict_false(__uselibcstub))
                return __libc_cond_broadcast_stub(cond);

        pthread__error(EINVAL, "Invalid condition variable",
            cond->ptc_magic == _PT_COND_MAGIC);

        if (cond->ptc_waiters == NULL)
                return 0;

        /* Take ownership of current set of waiters. */
        self = pthread_self();
        mutex = cond->ptc_mutex;
        for (head = cond->ptc_waiters;; head = next) {
                /* Wait while pthread_cond_signal() in progress. */
                if (__predict_false(head == pthread__cond_dummy_ptr)) {
                        sched_yield();
                        next = cond->ptc_waiters;
                        continue;
                }
                if (head == NULL) {
                        return 0;
                }
                next = atomic_cas_ptr(&cond->ptc_waiters, head, NULL);
                if (__predict_true(next == head)) {
                        break;
                }
        }
        membar_enter();

        /* Now transfer waiters to the mutex. */
        pthread__mutex_deferwake(self, mutex, head);
        return 0;
}

int
_pthread_cond_has_waiters_np(pthread_cond_t *cond)
{

        return cond->ptc_waiters != NULL;
}

int
pthread_condattr_init(pthread_condattr_t *attr)
{

        attr->ptca_magic = _PT_CONDATTR_MAGIC;
        attr->ptca_private = NULL;

        return 0;
}

int
pthread_condattr_setclock(pthread_condattr_t *attr, clockid_t clck)
{

        pthread__error(EINVAL, "Invalid condition variable attribute",
            attr->ptca_magic == _PT_CONDATTR_MAGIC);

        switch (clck) {
        case CLOCK_MONOTONIC:
        case CLOCK_REALTIME:
                if (attr->ptca_private == NULL)
                        attr->ptca_private = malloc(sizeof(clockid_t));
                if (attr->ptca_private == NULL)
                        return errno;
                *(clockid_t *)attr->ptca_private = clck;
                return 0;
        default:
                return EINVAL;
        }
}

int
pthread_condattr_getclock(const pthread_condattr_t *__restrict attr,
    clockid_t *__restrict clock_id)
{

        pthread__error(EINVAL, "Invalid condition variable attribute",
            attr->ptca_magic == _PT_CONDATTR_MAGIC);

        if (attr == NULL || attr->ptca_private == NULL)
                return EINVAL;
        *clock_id = *(clockid_t *)attr->ptca_private;
        return 0;
}

int
pthread_condattr_destroy(pthread_condattr_t *attr)
{

        pthread__error(EINVAL, "Invalid condition variable attribute",
            attr->ptca_magic == _PT_CONDATTR_MAGIC);

        attr->ptca_magic = _PT_CONDATTR_DEAD;
        free(attr->ptca_private);

        return 0;
}

#ifdef _PTHREAD_PSHARED
int
pthread_condattr_getpshared(const pthread_condattr_t * __restrict attr,
    int * __restrict pshared)
{

        pthread__error(EINVAL, "Invalid condition variable attribute",
            attr->ptca_magic == _PT_CONDATTR_MAGIC);

        *pshared = PTHREAD_PROCESS_PRIVATE;
        return 0;
}

int
pthread_condattr_setpshared(pthread_condattr_t *attr, int pshared)
{

        pthread__error(EINVAL, "Invalid condition variable attribute",
            attr->ptca_magic == _PT_CONDATTR_MAGIC);

        switch(pshared) {
        case PTHREAD_PROCESS_PRIVATE:
                return 0;
        case PTHREAD_PROCESS_SHARED:
                return ENOSYS;
        }
        return EINVAL;
}
#endif