/**************************************************************************
 *
 * Copyright (c) 2007-2009 VMware, Inc., Palo Alto, CA., USA
 * All Rights Reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a
 * copy of this software and associated documentation files (the
 * "Software"), to deal in the Software without restriction, including
 * without limitation the rights to use, copy, modify, merge, publish,
 * distribute, sub license, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so, subject to
 * the following conditions:
 *
 * The above copyright notice and this permission notice (including the
 * next paragraph) shall be included in all copies or substantial portions
 * of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO EVENT SHALL
 * THE COPYRIGHT HOLDERS, AUTHORS AND/OR ITS SUPPLIERS BE LIABLE FOR ANY CLAIM,
 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
 * OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
 * USE OR OTHER DEALINGS IN THE SOFTWARE.
 *
 **************************************************************************/
/*
 * Authors: Thomas Hellstrom <thellstrom-at-vmware-dot-com>
 */

#include "ttm/ttm_lock.h"
#include "ttm/ttm_module.h"
#include <linux/atomic.h>
#include <linux/errno.h>
#include <linux/wait.h>
#include <linux/sched.h>
#include <linux/module.h>

#define TTM_WRITE_LOCK_PENDING    (1 << 0)
#define TTM_VT_LOCK_PENDING       (1 << 1)
#define TTM_SUSPEND_LOCK_PENDING  (1 << 2)
#define TTM_VT_LOCK               (1 << 3)
#define TTM_SUSPEND_LOCK          (1 << 4)

void ttm_lock_init(struct ttm_lock *lock)
{
        spin_lock_init(&lock->lock);
        init_waitqueue_head(&lock->queue);
        lock->rw = 0;
        lock->flags = 0;
        lock->kill_takers = false;
        lock->signal = SIGKILL;
}
EXPORT_SYMBOL(ttm_lock_init);

void ttm_read_unlock(struct ttm_lock *lock)
{
        spin_lock(&lock->lock);
        if (--lock->rw == 0)
                wake_up_all(&lock->queue);
        spin_unlock(&lock->lock);
}
EXPORT_SYMBOL(ttm_read_unlock);

static bool __ttm_read_lock(struct ttm_lock *lock)
{
        bool locked = false;

        spin_lock(&lock->lock);
        if (unlikely(lock->kill_takers)) {
                send_sig(lock->signal, current, 0);
                spin_unlock(&lock->lock);
                return false;
        }
        if (lock->rw >= 0 && lock->flags == 0) {
                ++lock->rw;
                locked = true;
        }
        spin_unlock(&lock->lock);
        return locked;
}

int ttm_read_lock(struct ttm_lock *lock, bool interruptible)
{
        int ret = 0;

        if (interruptible)
                ret = wait_event_interruptible(lock->queue,
                                               __ttm_read_lock(lock));
        else
                wait_event(lock->queue, __ttm_read_lock(lock));
        return ret;
}
EXPORT_SYMBOL(ttm_read_lock);

static bool __ttm_read_trylock(struct ttm_lock *lock, bool *locked)
{
        bool block = true;

        *locked = false;

        spin_lock(&lock->lock);
        if (unlikely(lock->kill_takers)) {
                send_sig(lock->signal, current, 0);
                spin_unlock(&lock->lock);
                return false;
        }
        if (lock->rw >= 0 && lock->flags == 0) {
                ++lock->rw;
                block = false;
                *locked = true;
        } else if (lock->flags == 0) {
                block = false;
        }
        spin_unlock(&lock->lock);

        return !block;
}

int ttm_read_trylock(struct ttm_lock *lock, bool interruptible)
{
        int ret = 0;
        bool locked;

        if (interruptible)
                ret = wait_event_interruptible
                        (lock->queue, __ttm_read_trylock(lock, &locked));
        else
                wait_event(lock->queue, __ttm_read_trylock(lock, &locked));

        if (unlikely(ret != 0)) {
                BUG_ON(locked);
                return ret;
        }

        return (locked) ? 0 : -EBUSY;
}

void ttm_write_unlock(struct ttm_lock *lock)
{
        spin_lock(&lock->lock);
        lock->rw = 0;
        wake_up_all(&lock->queue);
        spin_unlock(&lock->lock);
}
EXPORT_SYMBOL(ttm_write_unlock);

static bool __ttm_write_lock(struct ttm_lock *lock)
{
        bool locked = false;

        spin_lock(&lock->lock);
        if (unlikely(lock->kill_takers)) {
                send_sig(lock->signal, current, 0);
                spin_unlock(&lock->lock);
                return false;
        }
        if (lock->rw == 0 && ((lock->flags & ~TTM_WRITE_LOCK_PENDING) == 0)) {
                lock->rw = -1;
                lock->flags &= ~TTM_WRITE_LOCK_PENDING;
                locked = true;
        } else {
                lock->flags |= TTM_WRITE_LOCK_PENDING;
        }
        spin_unlock(&lock->lock);
        return locked;
}

int ttm_write_lock(struct ttm_lock *lock, bool interruptible)
{
        int ret = 0;

        if (interruptible) {
                ret = wait_event_interruptible(lock->queue,
                                               __ttm_write_lock(lock));
                if (unlikely(ret != 0)) {
                        spin_lock(&lock->lock);
                        lock->flags &= ~TTM_WRITE_LOCK_PENDING;
                        wake_up_all(&lock->queue);
                        spin_unlock(&lock->lock);
                }
        } else
                wait_event(lock->queue, __ttm_read_lock(lock));

        return ret;
}
EXPORT_SYMBOL(ttm_write_lock);

void ttm_write_lock_downgrade(struct ttm_lock *lock)
{
        spin_lock(&lock->lock);
        lock->rw = 1;
        wake_up_all(&lock->queue);
        spin_unlock(&lock->lock);
}

static int __ttm_vt_unlock(struct ttm_lock *lock)
{
        int ret = 0;

        spin_lock(&lock->lock);
        if (unlikely(!(lock->flags & TTM_VT_LOCK)))
                ret = -EINVAL;
        lock->flags &= ~TTM_VT_LOCK;
        wake_up_all(&lock->queue);
        spin_unlock(&lock->lock);

        return ret;
}

static void ttm_vt_lock_remove(struct ttm_base_object **p_base)
{
        struct ttm_base_object *base = *p_base;
        struct ttm_lock *lock = container_of(base, struct ttm_lock, base);
        int ret;

        *p_base = NULL;
        ret = __ttm_vt_unlock(lock);
        BUG_ON(ret != 0);
}

static bool __ttm_vt_lock(struct ttm_lock *lock)
{
        bool locked = false;

        spin_lock(&lock->lock);
        if (lock->rw == 0) {
                lock->flags &= ~TTM_VT_LOCK_PENDING;
                lock->flags |= TTM_VT_LOCK;
                locked = true;
        } else {
                lock->flags |= TTM_VT_LOCK_PENDING;
        }
        spin_unlock(&lock->lock);
        return locked;
}

int ttm_vt_lock(struct ttm_lock *lock,
                bool interruptible,
                struct ttm_object_file *tfile)
{
        int ret = 0;

        if (interruptible) {
                ret = wait_event_interruptible(lock->queue,
                                               __ttm_vt_lock(lock));
                if (unlikely(ret != 0)) {
                        spin_lock(&lock->lock);
                        lock->flags &= ~TTM_VT_LOCK_PENDING;
                        wake_up_all(&lock->queue);
                        spin_unlock(&lock->lock);
                        return ret;
                }
        } else
                wait_event(lock->queue, __ttm_vt_lock(lock));

        /*
         * Add a base-object, the destructor of which will
         * make sure the lock is released if the client dies
         * while holding it.
         */

        ret = ttm_base_object_init(tfile, &lock->base, false,
                                   ttm_lock_type, &ttm_vt_lock_remove, NULL);
        if (ret)
                (void)__ttm_vt_unlock(lock);
        else
                lock->vt_holder = tfile;

        return ret;
}
EXPORT_SYMBOL(ttm_vt_lock);

int ttm_vt_unlock(struct ttm_lock *lock)
{
        return ttm_ref_object_base_unref(lock->vt_holder,
                                         lock->base.hash.key, TTM_REF_USAGE);
}
EXPORT_SYMBOL(ttm_vt_unlock);

void ttm_suspend_unlock(struct ttm_lock *lock)
{
        spin_lock(&lock->lock);
        lock->flags &= ~TTM_SUSPEND_LOCK;
        wake_up_all(&lock->queue);
        spin_unlock(&lock->lock);
}
EXPORT_SYMBOL(ttm_suspend_unlock);

static bool __ttm_suspend_lock(struct ttm_lock *lock)
{
        bool locked = false;

        spin_lock(&lock->lock);
        if (lock->rw == 0) {
                lock->flags &= ~TTM_SUSPEND_LOCK_PENDING;
                lock->flags |= TTM_SUSPEND_LOCK;
                locked = true;
        } else {
                lock->flags |= TTM_SUSPEND_LOCK_PENDING;
        }
        spin_unlock(&lock->lock);
        return locked;
}

void ttm_suspend_lock(struct ttm_lock *lock)
{
        wait_event(lock->queue, __ttm_suspend_lock(lock));
}
EXPORT_SYMBOL(ttm_suspend_lock);