/* -*- mode: c; c-basic-offset: 4; indent-tabs-mode: nil; -*-
 * vim:expandtab:shiftwidth=4:tabstop=4:
 *
 *  Copyright (c) 2004 Cluster File Systems, Inc.
 *
 *   This file is part of Lustre, http://www.lustre.org.
 *
 *   Lustre is free software; you can redistribute it and/or modify it under
 *   the terms of version 2 of the GNU General Public License as published by
 *   the Free Software Foundation. Lustre is distributed in the hope that it
 *   will be useful, but WITHOUT ANY WARRANTY; without even the implied
 *   warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *   GNU General Public License for more details. You should have received a
 *   copy of the GNU General Public License along with Lustre; if not, write
 *   to the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139,
 *   USA.
 */

#define DEBUG_SUBSYSTEM S_LIBCFS

#include <libcfs/libcfs.h>
#include <libcfs/kp30.h>


/*
 * Wait queue routines
 */

/*
 * cfs_waitq_init
 *   To initialize the wait queue
 *
 * Arguments:
 *   waitq:  pointer to the cfs_waitq_t structure
 *
 * Return Value:
 *   N/A
 *
 * Notes: 
 *   N/A
 */

void cfs_waitq_init(cfs_waitq_t *waitq)
{
    waitq->magic = CFS_WAITQ_MAGIC;
    waitq->flags = 0;
    INIT_LIST_HEAD(&(waitq->waiters));
    spin_lock_init(&(waitq->guard));
}

/*
 * cfs_waitlink_init
 *   To initialize the wake link node
 *
 * Arguments:
 *   link:  pointer to the cfs_waitlink_t structure
 *
 * Return Value:
 *   N/A
 *
 * Notes: 
 *   N/A
 */

void cfs_waitlink_init(cfs_waitlink_t *link)
{
    cfs_task_t * task = cfs_current();
    PTASK_SLOT   slot = NULL;

    if (!task) {
        /* should bugchk here */
        cfs_enter_debugger();
        return;
    }

    slot = CONTAINING_RECORD(task, TASK_SLOT, task);
    cfs_assert(slot->Magic == TASKSLT_MAGIC);

    memset(link, 0, sizeof(cfs_waitlink_t));

    link->magic = CFS_WAITLINK_MAGIC;
    link->flags = 0;

    link->event = &(slot->Event);
    link->hits  = &(slot->hits);

    atomic_inc(&slot->count);

    INIT_LIST_HEAD(&(link->waitq[0].link));
    INIT_LIST_HEAD(&(link->waitq[1].link));

    link->waitq[0].waitl = link->waitq[1].waitl = link;
}


/*
 * cfs_waitlink_fini
 *   To finilize the wake link node
 *
 * Arguments:
 *   link:  pointer to the cfs_waitlink_t structure
 *
 * Return Value:
 *   N/A
 *
 * Notes: 
 *   N/A
 */

void cfs_waitlink_fini(cfs_waitlink_t *link)
{
    cfs_task_t * task = cfs_current();
    PTASK_SLOT   slot = NULL;

    if (!task) {
        /* should bugchk here */
        cfs_enter_debugger();
        return;
    }

    slot = CONTAINING_RECORD(task, TASK_SLOT, task);
    cfs_assert(slot->Magic == TASKSLT_MAGIC);
    cfs_assert(link->magic == CFS_WAITLINK_MAGIC);
    cfs_assert(link->waitq[0].waitq == NULL);
    cfs_assert(link->waitq[1].waitq == NULL);

    atomic_dec(&slot->count);
}


/*
 * cfs_waitq_add_internal
 *   To queue the wait link node to the wait queue
 *
 * Arguments:
 *   waitq:  pointer to the cfs_waitq_t structure
 *   link:   pointer to the cfs_waitlink_t structure
 *   int:    queue no (Normal or Forward waitq)
 *
 * Return Value:
 *   N/A
 *
 * Notes: 
 *   N/A
 */

void cfs_waitq_add_internal(cfs_waitq_t *waitq,
                            cfs_waitlink_t *link,
                            __u32 waitqid )
{ 
    LASSERT(waitq != NULL);
    LASSERT(link != NULL);
    LASSERT(waitq->magic == CFS_WAITQ_MAGIC);
    LASSERT(link->magic == CFS_WAITLINK_MAGIC);
    LASSERT(waitqid < CFS_WAITQ_CHANNELS);

    spin_lock(&(waitq->guard));
    LASSERT(link->waitq[waitqid].waitq == NULL);
    link->waitq[waitqid].waitq = waitq;
    if (link->flags & CFS_WAITQ_EXCLUSIVE) {
        list_add_tail(&link->waitq[waitqid].link, &waitq->waiters);
    } else {
        list_add(&link->waitq[waitqid].link, &waitq->waiters);
    }
    spin_unlock(&(waitq->guard));
}
/*
 * cfs_waitq_add
 *   To queue the wait link node to the wait queue
 *
 * Arguments:
 *   waitq:  pointer to the cfs_waitq_t structure
 *   link:  pointer to the cfs_waitlink_t structure
 *
 * Return Value:
 *   N/A
 *
 * Notes: 
 *   N/A
 */

void cfs_waitq_add(cfs_waitq_t *waitq,
                   cfs_waitlink_t *link)
{ 
    cfs_waitq_add_internal(waitq, link, CFS_WAITQ_CHAN_NORMAL);
}

/*
 * cfs_waitq_add_exclusive
 *   To set the wait link node to exclusive mode
 *   and queue it to the wait queue
 *
 * Arguments:
 *   waitq:  pointer to the cfs_waitq_t structure
 *   link:  pointer to the cfs_wait_link structure
 *
 * Return Value:
 *   N/A
 *
 * Notes: 
 *   N/A
 */

void cfs_waitq_add_exclusive( cfs_waitq_t *waitq,
                              cfs_waitlink_t *link)
{
    LASSERT(waitq != NULL);
    LASSERT(link != NULL);
    LASSERT(waitq->magic == CFS_WAITQ_MAGIC);
    LASSERT(link->magic == CFS_WAITLINK_MAGIC);

	link->flags |= CFS_WAITQ_EXCLUSIVE;
    cfs_waitq_add(waitq, link);
}

/*
 * cfs_waitq_forward
 *   To be determinated.
 *
 * Arguments:
 *   waitq:  pointer to the cfs_waitq_t structure
 *   link:  pointer to the cfs_waitlink_t structure
 *
 * Return Value:
 *   N/A
 *
 * Notes: 
 *   N/A
 */

void cfs_waitq_forward( cfs_waitlink_t *link,
                        cfs_waitq_t *waitq)
{
    cfs_waitq_add_internal(waitq, link, CFS_WAITQ_CHAN_FORWARD);
}

/*
 * cfs_waitq_del
 *   To remove the wait link node from the waitq
 *
 * Arguments:
 *   waitq:  pointer to the cfs_ waitq_t structure
 *   link:  pointer to the cfs_waitlink_t structure
 *
 * Return Value:
 *   N/A
 *
 * Notes: 
 *   N/A
 */

void cfs_waitq_del( cfs_waitq_t *waitq,
                    cfs_waitlink_t *link)
{
    int i = 0;

    LASSERT(waitq != NULL);
    LASSERT(link != NULL);

    LASSERT(waitq->magic == CFS_WAITQ_MAGIC);
    LASSERT(link->magic == CFS_WAITLINK_MAGIC);

    spin_lock(&(waitq->guard));

    for (i=0; i < CFS_WAITQ_CHANNELS; i++) {
        if (link->waitq[i].waitq == waitq)
            break;
    }

    if (i < CFS_WAITQ_CHANNELS) {
        link->waitq[i].waitq = NULL;
        list_del_init(&link->waitq[i].link);
    } else {
        cfs_enter_debugger();
    }

    spin_unlock(&(waitq->guard));
}

/*
 * cfs_waitq_active
 *   Is the waitq active (not empty) ?
 *
 * Arguments:
 *   waitq:  pointer to the cfs_ waitq_t structure
 *
 * Return Value:
 *   Zero: the waitq is empty
 *   Non-Zero: the waitq is active
 *
 * Notes: 
 *   We always returns TRUE here, the same to Darwin.
 */

int cfs_waitq_active(cfs_waitq_t *waitq)
{
    LASSERT(waitq != NULL);
    LASSERT(waitq->magic == CFS_WAITQ_MAGIC);

	return (1);
}

/*
 * cfs_waitq_signal_nr
 *   To wake up all the non-exclusive tasks plus nr exclusive
 *   ones in the waitq
 *
 * Arguments:
 *   waitq:  pointer to the cfs_waitq_t structure
 *   nr:    number of exclusive tasks to be woken up
 *
 * Return Value:
 *   N/A
 *
 * Notes: 
 *   N/A
 */


void cfs_waitq_signal_nr(cfs_waitq_t *waitq, int nr)
{
    int     result;
    cfs_waitlink_channel_t * scan;

    LASSERT(waitq != NULL);
    LASSERT(waitq->magic == CFS_WAITQ_MAGIC);

    spin_lock(&waitq->guard);

    list_for_each_entry(scan, &waitq->waiters, cfs_waitlink_channel_t, link) {

        cfs_waitlink_t *waitl = scan->waitl;

        result = cfs_wake_event(waitl->event);
        LASSERT( result == FALSE || result == TRUE );

        if (result) {
            atomic_inc(waitl->hits);
        }

        if ((waitl->flags & CFS_WAITQ_EXCLUSIVE) && --nr == 0)
            break;
    }

    spin_unlock(&waitq->guard);
    return;
}

/*
 * cfs_waitq_signal
 *   To wake up all the non-exclusive tasks and 1 exclusive
 *
 * Arguments:
 *   waitq:  pointer to the cfs_waitq_t structure
 *
 * Return Value:
 *   N/A
 *
 * Notes: 
 *   N/A
 */

void cfs_waitq_signal(cfs_waitq_t *waitq)
{
    cfs_waitq_signal_nr(waitq, 1);
}


/*
 * cfs_waitq_broadcast
 *   To wake up all the tasks in the waitq
 *
 * Arguments:
 *   waitq:  pointer to the cfs_waitq_t structure
 *
 * Return Value:
 *   N/A
 *
 * Notes: 
 *   N/A
 */

void cfs_waitq_broadcast(cfs_waitq_t *waitq)
{
    LASSERT(waitq != NULL);
    LASSERT(waitq->magic ==CFS_WAITQ_MAGIC);

	cfs_waitq_signal_nr(waitq, 0);
}

/*
 * cfs_waitq_wait
 *   To wait on the link node until it is signaled.
 *
 * Arguments:
 *   link:  pointer to the cfs_waitlink_t structure
 *
 * Return Value:
 *   N/A
 *
 * Notes: 
 *   N/A
 */

void cfs_waitq_wait(cfs_waitlink_t *link, cfs_task_state_t state)
{ 
    LASSERT(link != NULL);
    LASSERT(link->magic == CFS_WAITLINK_MAGIC);

    if (atomic_read(link->hits) > 0) {
        atomic_dec(link->hits);
        LASSERT((__u32)atomic_read(link->hits) < (__u32)0xFFFFFF00);
    } else {
        cfs_wait_event(link->event, 0);
    }
}

/*
 * cfs_waitq_timedwait
 *   To wait the link node to be signaled with a timeout limit
 *
 * Arguments:
 *   link:   pointer to the cfs_waitlink_t structure
 *   timeout: the timeout limitation
 *
 * Return Value:
 *   Woken up: return the difference of the current time and
 *             the timeout
 *   Timeout:  return 0
 *
 * Notes: 
 *   What if it happens to be woken up at the just timeout time !?
 */

cfs_duration_t cfs_waitq_timedwait( cfs_waitlink_t *link,
                                    cfs_task_state_t state,
                                    cfs_duration_t timeout)
{ 

    if (atomic_read(link->hits) > 0) {
        atomic_dec(link->hits);
        LASSERT((__u32)atomic_read(link->hits) < (__u32)0xFFFFFF00);
        return TRUE;
    }

    return (cfs_duration_t)cfs_wait_event(link->event, timeout);
}