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/*

 * Copyright (c) 2006 Ondrej Palkovsky

 * Copyright (c) 2007 Jakub Jermar

 * 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(void)

{

    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 spans the whole life-cycle of a pseudo thread.

 *

 * Each pseudo thread begins execution in this function.

 * Then the function implementing the pseudo thread logic is called.

 * After its return, the return value is saved for a potentional

 * joiner. If the joiner exists, it is woken up. The pseudo thread

 * then switches to another pseudo thread, which cleans up after it.

 */

void psthread_main(void)

{

    psthread_data_t *pt = __tcb_get()->pst_data;

    pt->retval = pt->func(pt->arg);

    /*

     * If there is a joiner, wake it up and save our return value.

     */

    if (pt->joiner) {

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

        pt->joiner->joinee_retval = pt->retval;

    }

    psthread_schedule_next_adv(PS_FROM_DEAD);

    /* not reached */

}

/** Schedule next userspace pseudo thread.

 *

 * If calling with PS_TO_MANAGER parameter, the async_futex should be

 * held.

 *

 * @param ctype     One of PS_SLEEP, PS_PREEMPT, PS_TO_MANAGER,

 *          PS_FROM_MANAGER, PS_FROM_DEAD. The parameter describes

 *          the circumstances of the switch.

 * @return      Return 0 if there is no ready pseudo thread,

 *          return 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_SLEEP) {

        if (list_empty(&ready_list) && list_empty(&serialized_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);

        }

    }

    srcpt = __tcb_get()->pst_data;

    if (ctype != PS_FROM_DEAD) {

        /* Save current state */

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

            if (serialization_count)

                srcpt->flags &= ~PSTHREAD_SERIALIZED;

            if (srcpt->clean_after_me) {

                /*

                 * Cleanup after the dead pseudo thread from

                 * which we restored context here.

                 */

                free(srcpt->clean_after_me->stack);

                psthread_teardown(srcpt->clean_after_me);

                srcpt->clean_after_me = NULL;

            }

            return 1;   /* futex_up already done here */

        }

        /* Save myself to the 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--;

        } else {   

            /*

             * If ctype == PS_TO_MANAGER, don't save ourselves to

             * any list, we should already be somewhere, or we will

             * be lost.

             *

             * The ctype == PS_SLEEP case is similar. The pseudo

             * thread has an external refernce which can be used to

             * wake it up once that time has come.

             */

        }

    }

    /* 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++;

        if (ctype == PS_FROM_DEAD)

            dstpt->clean_after_me = srcpt;

    } 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);

    /* not reached */

ret_0:

    futex_up(&psthread_futex);

    return retval;

}

/** Wait for uspace pseudo thread to finish.

 *

 * Each pseudo thread can be only joined by one other pseudo thread. Moreover,

 * the joiner must be from the same thread as the joinee.

 *

 * @param psthrid   Pseudo thread to join.

 *

 * @return      Value returned by the finished thread.

 */

int psthread_join(pstid_t psthrid)

{

    psthread_data_t *pt;

    psthread_data_t *cur;

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

    pt = (psthread_data_t *) psthrid;

    /*

     * The joiner is running so the joinee isn't.

     */

    cur = __tcb_get()->pst_data;

    pt->joiner = cur;

    psthread_schedule_next_adv(PS_SLEEP);

    /*

     * The joinee fills in the return value.

     */

    return cur->joinee_retval;

}

/** Create a userspace pseudo thread.

 *

 * @param func      Pseudo thread function.

 * @param arg       Argument to pass to func.

 *

 * @return      Return 0 on failure or 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->clean_after_me = NULL;

    pt->joiner = NULL;

    pt->joinee_retval = 0;

    pt->retval = 0;

    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 the ready list.

 *

 * @param psthrid       Pinter to the pseudo thread structure of the

 *              pseudo thread to be added.

 */

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 pseudo thread to the manager list.

 *

 * @param psthrid       Pinter to the pseudo thread structure of the

 *              pseudo thread to be added.

 */

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(void)

{

    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 the currently running thread.

 *

 * @return      Pseudo thread ID of the currently running pseudo 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 a 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 can still be preempted.

 */

void psthread_inc_sercount(void)

{

    serialization_count++;

}

/** Restore the preemption counter to the previous state. */

void psthread_dec_sercount(void)

{

    serialization_count--;

}

/** @}

 */