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/*

 * Copyright (c) 2006 Ondrej Palkovsky

 * All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without

 * modification, are permitted provided that the following conditions

 * are met:

 *

 * - Redistributions of source code must retain the above copyright

 *   notice, this list of conditions and the following disclaimer.

 * - 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.

 * - The name of the author may not be used to endorse or promote products

 *   derived from this software without specific prior written permission.

 *

 * 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.

 */

/** @addtogroup libc

 * @{

 */

/** @file

 */

#include <libadt/list.h>

#include <psthread.h>

#include <malloc.h>

#include <unistd.h>

#include <thread.h>

#include <stdio.h>

#include <libarch/faddr.h>

#include <futex.h>

#include <assert.h>

#include <async.h>

#ifndef PSTHREAD_INITIAL_STACK_PAGES_NO

#define PSTHREAD_INITIAL_STACK_PAGES_NO 1

#endif

static LIST_INITIALIZE(ready_list);

static LIST_INITIALIZE(serialized_list);

static LIST_INITIALIZE(manager_list);

static void psthread_main(void);

static atomic_t psthread_futex = FUTEX_INITIALIZER;

/** Count of real threads that are in async_serialized mode */

static int serialized_threads; /* Protected by async_futex */

/** Thread-local count of serialization. If >0, we must not preempt */

static __thread int serialization_count;

/** Counter of threads residing in async_manager */

static int threads_in_manager;

/** Setup psthread information into TCB structure */

psthread_data_t * psthread_setup()

{

    psthread_data_t *pt;

    tcb_t *tcb;

    tcb = __make_tls();

    if (!tcb)

        return NULL;

    pt = malloc(sizeof(*pt));

    if (!pt) {

        __free_tls(tcb);

        return NULL;

    }

    tcb->pst_data = pt;

    pt->tcb = tcb;

    return pt;

}

void psthread_teardown(psthread_data_t *pt)

{

    __free_tls(pt->tcb);

    free(pt);

}

/** Function that is called on entry to new pseudo thread */

void psthread_main(void)

{

    psthread_data_t *pt = __tcb_get()->pst_data;

    pt->retval = pt->func(pt->arg);

    pt->finished = 1;

    if (pt->waiter)

        list_append(&pt->waiter->link, &ready_list);

    psthread_schedule_next_adv(PS_FROM_DEAD);

}

/** Schedule next userspace pseudo thread.

 *

 * If calling with PS_TO_MANAGER parameter, the async_futex should be

 * held.

 *

 * @param ctype Type of switch.

 * @return 0 if there is no ready pseudo thread, 1 otherwise.

 */

int psthread_schedule_next_adv(pschange_type ctype)

{

    psthread_data_t *srcpt, *dstpt;

    int retval = 0;

    futex_down(&psthread_futex);

    if (ctype == PS_PREEMPT && list_empty(&ready_list))

        goto ret_0;

    if (ctype == PS_FROM_MANAGER) {

        if (list_empty(&ready_list) && list_empty(&serialized_list))

            goto ret_0;

        /* Do not preempt if there is not sufficient count of thread managers */

        if (list_empty(&serialized_list) && threads_in_manager <= serialized_threads) {

            goto ret_0;

        }

    }

    /* If we are going to manager and none exists, create it */

    if (ctype == PS_TO_MANAGER || ctype == PS_FROM_DEAD) {

        while (list_empty(&manager_list)) {

            futex_up(&psthread_futex);

            async_create_manager();

            futex_down(&psthread_futex);

        }

    }

    if (ctype != PS_FROM_DEAD) {

        /* Save current state */

        srcpt = __tcb_get()->pst_data;

        if (!context_save(&srcpt->ctx)) {

            if (serialization_count)

                srcpt->flags &= ~PSTHREAD_SERIALIZED;

            return 1; // futex_up already done here

        }

        /* Save myself to correct run list */

        if (ctype == PS_PREEMPT)

            list_append(&srcpt->link, &ready_list);

        else if (ctype == PS_FROM_MANAGER) {

            list_append(&srcpt->link, &manager_list);

            threads_in_manager--;

        } /* If ctype == PS_TO_MANAGER, don't save ourselves to any list, we should

           * already be somewhere, or we will be lost */

    } else

        srcpt = NULL; /* Avoid GCC warning, if ctype == PS_FROM_DEAD, srcpt is not used */

    /* Choose new thread to run */

    if (ctype == PS_TO_MANAGER || ctype == PS_FROM_DEAD) {

        dstpt = list_get_instance(manager_list.next,psthread_data_t, link);

        if (serialization_count && ctype == PS_TO_MANAGER) {

            serialized_threads++;

            srcpt->flags |= PSTHREAD_SERIALIZED;

        }

        threads_in_manager++;

    } else {

        if (!list_empty(&serialized_list)) {

            dstpt = list_get_instance(serialized_list.next, psthread_data_t, link);

            serialized_threads--;

        } else

            dstpt = list_get_instance(ready_list.next, psthread_data_t, link);

    }

    list_remove(&dstpt->link);

    futex_up(&psthread_futex);

    context_restore(&dstpt->ctx);

ret_0:

    futex_up(&psthread_futex);

    return retval;

}

/** Wait for uspace pseudo thread to finish.

 *

 * @param psthrid Pseudo thread to wait for.

 *

 * @return Value returned by the finished thread.

 */

int psthread_join(pstid_t psthrid)

{

    volatile psthread_data_t *pt;

    volatile int retval;

    /* Handle psthrid = Kernel address -> it is wait for call */

    pt = (psthread_data_t *) psthrid;

    /* TODO */

    printf("join unsupported\n");

    _exit(1);

    retval = pt->retval;

    free(pt->stack);

    psthread_teardown((void *)pt);

    return retval;

}

/** Create a userspace pseudo thread.

 *

 * @param func Pseudo thread function.

 * @param arg Argument to pass to func.

 *

 * @return 0 on failure, TLS of the new pseudo thread.

 */

pstid_t psthread_create(int (*func)(void *), void *arg)

{

    psthread_data_t *pt;

    pt = psthread_setup();

    if (!pt)

        return 0;

    pt->stack = (char *) malloc(PSTHREAD_INITIAL_STACK_PAGES_NO*getpagesize());

    if (!pt->stack) {

        psthread_teardown(pt);

        return 0;

    }

    pt->arg= arg;

    pt->func = func;

    pt->finished = 0;

    pt->waiter = NULL;

    pt->flags = 0;

    context_save(&pt->ctx);

    context_set(&pt->ctx, FADDR(psthread_main), pt->stack, PSTHREAD_INITIAL_STACK_PAGES_NO*getpagesize(), pt->tcb);

    return (pstid_t )pt;

}

/** Add a thread to ready list */

void psthread_add_ready(pstid_t psthrid)

{

    psthread_data_t *pt;

    pt = (psthread_data_t *) psthrid;

    futex_down(&psthread_futex);

    if ((pt->flags & PSTHREAD_SERIALIZED))

        list_append(&pt->link, &serialized_list);

    else

        list_append(&pt->link, &ready_list);

    futex_up(&psthread_futex);

}

/** Add a thread to manager list */

void psthread_add_manager(pstid_t psthrid)

{

    psthread_data_t *pt;

    pt = (psthread_data_t *) psthrid;

    futex_down(&psthread_futex);

    list_append(&pt->link, &manager_list);

    futex_up(&psthread_futex);

}

/** Remove one manager from manager list */

void psthread_remove_manager()

{

    futex_down(&psthread_futex);

    if (list_empty(&manager_list)) {

        futex_up(&psthread_futex);

        return;

    }

    list_remove(manager_list.next);

    futex_up(&psthread_futex);

}

/** Return thread id of current running thread */

pstid_t psthread_get_id(void)

{

    return (pstid_t)__tcb_get()->pst_data;

}

/** Disable preemption

 *

 * If the thread wants to send several message in row and does not want

 * to be preempted, it should start async_serialize_start() in the beginning

 * of communication and async_serialize_end() in the end. If it is a

 * true multithreaded application, it should protect the communication channel

 * by a futex as well. Interrupt messages will can still be preempted.

 */

void psthread_inc_sercount(void)

{

    serialization_count++;

}

void psthread_dec_sercount(void)

{

    serialization_count--;

}

/** @}

 */