/*-
 * Copyright (c) 2017 Mark Johnston <markj@FreeBSD.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conds
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice unmodified, this list of conds, and the following
 *    disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conds 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/param.h>
#include <sys/systm.h>
#include <sys/proc.h>
#include <sys/signalvar.h>
#include <sys/sleepqueue.h>

#include <linux/delay.h>
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/sched.h>
#include <linux/spinlock.h>
#include <linux/wait.h>

/*
 * Convert a relative time in jiffies to a tick count, suitable for use with
 * native FreeBSD interfaces (callouts, sleepqueues, etc.).
 */
static int
linux_jiffies_timeout_to_ticks(long timeout)
{
        if (timeout < 1)
                return (1);
        else if (timeout == MAX_SCHEDULE_TIMEOUT)
                return (0);
        else if (timeout > INT_MAX)
                return (INT_MAX);
        else
                return (timeout);
}

static int
linux_add_to_sleepqueue(void *wchan, struct task_struct *task,
    const char *wmesg, long timeout, int state)
{
        int flags, ret, stimeout;

        MPASS((state & ~(TASK_PARKED | TASK_NORMAL)) == 0);

        flags = SLEEPQ_SLEEP | ((state & TASK_INTERRUPTIBLE) != 0 ?
            SLEEPQ_INTERRUPTIBLE : 0);
        stimeout = linux_jiffies_timeout_to_ticks(timeout);

        sleepq_add(wchan, NULL, wmesg, flags, 0);
        if (stimeout != 0)
                sleepq_set_timeout(wchan, stimeout);

        DROP_GIANT();
        if ((state & TASK_INTERRUPTIBLE) != 0) {
                if (stimeout == 0)
                        ret = -sleepq_wait_sig(wchan, 0);
                else
                        ret = -sleepq_timedwait_sig(wchan, 0);
        } else {
                if (stimeout == 0) {
                        sleepq_wait(wchan, 0);
                        ret = 0;
                } else
                        ret = -sleepq_timedwait(wchan, 0);
        }
        PICKUP_GIANT();

        /* filter return value */
        if (ret != 0 && ret != -EWOULDBLOCK) {
                linux_schedule_save_interrupt_value(task, ret);
                ret = -ERESTARTSYS;
        }
        return (ret);
}

unsigned int
linux_msleep_interruptible(unsigned int ms)
{
        int ret;

        /* guard against invalid values */
        if (ms == 0)
                ms = 1;
        ret = -pause_sbt("lnxsleep", mstosbt(ms), 0, C_HARDCLOCK | C_CATCH);

        switch (ret) {
        case -EWOULDBLOCK:
                return (0);
        default:
                linux_schedule_save_interrupt_value(current, ret);
                return (ms);
        }
}

static int
wake_up_task(struct task_struct *task, unsigned int state)
{
        int ret;

        ret = 0;
        sleepq_lock(task);
        if ((atomic_read(&task->state) & state) != 0) {
                set_task_state(task, TASK_WAKING);
                sleepq_signal(task, SLEEPQ_SLEEP, 0, 0);
                ret = 1;
        }
        sleepq_release(task);
        return (ret);
}

bool
linux_signal_pending(struct task_struct *task)
{
        struct thread *td;
        sigset_t pending;

        td = task->task_thread;
        PROC_LOCK(td->td_proc);
        pending = td->td_siglist;
        SIGSETOR(pending, td->td_proc->p_siglist);
        SIGSETNAND(pending, td->td_sigmask);
        PROC_UNLOCK(td->td_proc);
        return (!SIGISEMPTY(pending));
}

bool
linux_fatal_signal_pending(struct task_struct *task)
{
        struct thread *td;
        bool ret;

        td = task->task_thread;
        PROC_LOCK(td->td_proc);
        ret = SIGISMEMBER(td->td_siglist, SIGKILL) ||
            SIGISMEMBER(td->td_proc->p_siglist, SIGKILL);
        PROC_UNLOCK(td->td_proc);
        return (ret);
}

bool
linux_signal_pending_state(long state, struct task_struct *task)
{

        MPASS((state & ~TASK_NORMAL) == 0);

        if ((state & TASK_INTERRUPTIBLE) == 0)
                return (false);
        return (linux_signal_pending(task));
}

void
linux_send_sig(int signo, struct task_struct *task)
{
        struct thread *td;

        td = task->task_thread;
        PROC_LOCK(td->td_proc);
        tdsignal(td, signo);
        PROC_UNLOCK(td->td_proc);
}

int
autoremove_wake_function(wait_queue_t *wq, unsigned int state, int flags,
    void *key __unused)
{
        struct task_struct *task;
        int ret;

        task = wq->private;
        if ((ret = wake_up_task(task, state)) != 0)
                list_del_init(&wq->task_list);
        return (ret);
}

int
default_wake_function(wait_queue_t *wq, unsigned int state, int flags,
    void *key __unused)
{
        return (wake_up_task(wq->private, state));
}

long
linux_wait_woken(wait_queue_t *wq, unsigned state, long timeout)
{
        void *wchan;
        struct task_struct *task;
        int ret;
        int remainder;

        task = current;
        wchan = wq->private;

        remainder = jiffies + timeout;

        set_task_state(task, state);

        sleepq_lock(wchan);
        if (!(wq->flags & WQ_FLAG_WOKEN)) {
                ret = linux_add_to_sleepqueue(wchan, task, "woken",
                    timeout, state);
        } else {
                sleepq_release(wchan);
                ret = 0;
        }

        set_task_state(task, TASK_RUNNING);
        wq->flags &= ~WQ_FLAG_WOKEN;

        if (timeout == MAX_SCHEDULE_TIMEOUT)
                return (MAX_SCHEDULE_TIMEOUT);

        /* range check return value */
        remainder -= jiffies;

        /* range check return value */
        if (ret == -ERESTARTSYS && remainder < 1)
                remainder = 1;
        else if (remainder < 0)
                remainder = 0;
        else if (remainder > timeout)
                remainder = timeout;
        return (remainder);
}

int
woken_wake_function(wait_queue_t *wq, unsigned int state,
    int flags __unused, void *key __unused)
{
        void *wchan;

        wchan = wq->private;

        sleepq_lock(wchan);
        wq->flags |= WQ_FLAG_WOKEN;
        sleepq_signal(wchan, SLEEPQ_SLEEP, 0, 0);
        sleepq_release(wchan);

        return (1);
}

void
linux_init_wait_entry(wait_queue_t *wq, int flags)
{

        memset(wq, 0, sizeof(*wq));
        wq->flags = flags;
        wq->private = current;
        wq->func = autoremove_wake_function;
        INIT_LIST_HEAD(&wq->task_list);
}

void
linux_wake_up(wait_queue_head_t *wqh, unsigned int state, int nr, bool locked)
{
        wait_queue_t *pos, *next;

        if (!locked)
                spin_lock(&wqh->lock);
        list_for_each_entry_safe(pos, next, &wqh->task_list, task_list) {
                if (pos->func == NULL) {
                        if (wake_up_task(pos->private, state) != 0 && --nr == 0)
                                break;
                } else {
                        if (pos->func(pos, state, 0, NULL) != 0 && --nr == 0)
                                break;
                }
        }
        if (!locked)
                spin_unlock(&wqh->lock);
}

void
linux_prepare_to_wait(wait_queue_head_t *wqh, wait_queue_t *wq, int state)
{

        spin_lock(&wqh->lock);
        if (list_empty(&wq->task_list))
                __add_wait_queue(wqh, wq);
        set_task_state(current, state);
        spin_unlock(&wqh->lock);
}

void
linux_finish_wait(wait_queue_head_t *wqh, wait_queue_t *wq)
{

        spin_lock(&wqh->lock);
        set_task_state(current, TASK_RUNNING);
        if (!list_empty(&wq->task_list)) {
                __remove_wait_queue(wqh, wq);
                INIT_LIST_HEAD(&wq->task_list);
        }
        spin_unlock(&wqh->lock);
}

bool
linux_waitqueue_active(wait_queue_head_t *wqh)
{
        bool ret;

        spin_lock(&wqh->lock);
        ret = !list_empty(&wqh->task_list);
        spin_unlock(&wqh->lock);
        return (ret);
}

int
linux_wait_event_common(wait_queue_head_t *wqh, wait_queue_t *wq, long timeout,
    unsigned int state, spinlock_t *lock)
{
        struct task_struct *task;
        int ret;

        if (lock != NULL)
                spin_unlock_irq(lock);

        task = current;

        sleepq_lock(task);
        if (atomic_read(&task->state) != TASK_WAKING) {
                ret = linux_add_to_sleepqueue(task, task, "wevent", timeout,
                    state);
        } else {
                sleepq_release(task);
                ret = 0;
        }

        if (lock != NULL)
                spin_lock_irq(lock);
        return (ret);
}

long
linux_schedule_timeout(long timeout)
{
        struct task_struct *task;
        long remainder;
        int ret, state;

        task = current;

        remainder = jiffies + timeout;

        sleepq_lock(task);
        state = atomic_read(&task->state);
        if (state != TASK_WAKING) {
                ret = linux_add_to_sleepqueue(task, task, "sched", timeout,
                    state);
        } else {
                sleepq_release(task);
                ret = 0;
        }
        set_task_state(task, TASK_RUNNING);

        if (timeout == MAX_SCHEDULE_TIMEOUT)
                return (MAX_SCHEDULE_TIMEOUT);

        /* range check return value */
        remainder -= jiffies;

        /* range check return value */
        if (ret == -ERESTARTSYS && remainder < 1)
                remainder = 1;
        else if (remainder < 0)
                remainder = 0;
        else if (remainder > timeout)
                remainder = timeout;
        return (remainder);
}

static void
wake_up_sleepers(void *wchan)
{
        sleepq_lock(wchan);
        sleepq_signal(wchan, SLEEPQ_SLEEP, 0, 0);
        sleepq_release(wchan);
}

#define bit_to_wchan(word, bit) ((void *)(((uintptr_t)(word) << 6) | (bit)))

void
linux_wake_up_bit(void *word, int bit)
{

        wake_up_sleepers(bit_to_wchan(word, bit));
}

int
linux_wait_on_bit_timeout(unsigned long *word, int bit, unsigned int state,
    long timeout)
{
        struct task_struct *task;
        void *wchan;
        int ret;

        task = current;
        wchan = bit_to_wchan(word, bit);
        for (;;) {
                sleepq_lock(wchan);
                if ((*word & (1 << bit)) == 0) {
                        sleepq_release(wchan);
                        ret = 0;
                        break;
                }
                set_task_state(task, state);
                ret = linux_add_to_sleepqueue(wchan, task, "wbit", timeout,
                    state);
                if (ret != 0)
                        break;
        }
        set_task_state(task, TASK_RUNNING);

        return (ret);
}

void
linux_wake_up_atomic_t(atomic_t *a)
{

        wake_up_sleepers(a);
}

int
linux_wait_on_atomic_t(atomic_t *a, unsigned int state)
{
        struct task_struct *task;
        void *wchan;
        int ret;

        task = current;
        wchan = a;
        for (;;) {
                sleepq_lock(wchan);
                if (atomic_read(a) == 0) {
                        sleepq_release(wchan);
                        ret = 0;
                        break;
                }
                set_task_state(task, state);
                ret = linux_add_to_sleepqueue(wchan, task, "watomic", 0, state);
                if (ret != 0)
                        break;
        }
        set_task_state(task, TASK_RUNNING);

        return (ret);
}

bool
linux_wake_up_state(struct task_struct *task, unsigned int state)
{

        return (wake_up_task(task, state) != 0);
}