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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 <adt/list.h>

#include <fibril.h>

#include <thread.h>

#include <tls.h>

#include <malloc.h>

#include <unistd.h>

#include <stdio.h>

#include <libarch/faddr.h>

#include <futex.h>

#include <assert.h>

#include <async.h>

#ifndef FIBRIL_INITIAL_STACK_PAGES_NO

#define FIBRIL_INITIAL_STACK_PAGES_NO   1

#endif

/**

 * This futex serializes access to ready_list, serialized_list and manager_list.

 */

static atomic_t fibril_futex = FUTEX_INITIALIZER;

static LIST_INITIALIZE(ready_list);

static LIST_INITIALIZE(serialized_list);

static LIST_INITIALIZE(manager_list);

static void fibril_main(void);

/** Number of threads that are executing a manager fibril. */

static int threads_in_manager;

/** Number of threads that are executing a manager fibril and are serialized. */

static int serialized_threads;  /* Protected by async_futex */

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

static fibril_local int serialization_count;

/** Setup fibril information into TCB structure */

fibril_t *fibril_setup(void)

{

    fibril_t *f;

    tcb_t *tcb;

    tcb = __make_tls();

    if (!tcb)

        return NULL;

    f = malloc(sizeof(fibril_t));

    if (!f) {

        __free_tls(tcb);

        return NULL;

    }

    tcb->fibril_data = f;

    f->tcb = tcb;

    f->func = NULL;

    f->arg = NULL;

    f->stack = NULL;

    f->clean_after_me = NULL;

    f->retval = 0;

    f->flags = 0;

    return f;

}

void fibril_teardown(fibril_t *f)

{

    __free_tls(f->tcb);

    free(f);

}

/** Function that spans the whole life-cycle of a fibril.

 *

 * Each fibril begins execution in this function. Then the function implementing

 * the fibril logic is called.  After its return, the return value is saved.

 * The fibril then switches to another fibril, which cleans up after it.

 */

void fibril_main(void)

{

    fibril_t *f = __tcb_get()->fibril_data;

    /* Call the implementing function. */

    f->retval = f->func(f->arg);

    fibril_switch(FIBRIL_FROM_DEAD);

    /* not reached */

}

/** Switch from the current fibril.

 *

 * If calling with FIBRIL_TO_MANAGER parameter, the async_futex should be

 * held.

 *

 * @param stype     Switch type. One of FIBRIL_PREEMPT, FIBRIL_TO_MANAGER,

 *          FIBRIL_FROM_MANAGER, FIBRIL_FROM_DEAD. The parameter

 *          describes the circumstances of the switch.

 * @return      Return 0 if there is no ready fibril,

 *          return 1 otherwise.

 */

int fibril_switch(fibril_switch_type_t stype)

{

    fibril_t *srcf, *dstf;

    int retval = 0;

    futex_down(&fibril_futex);

    if (stype == FIBRIL_PREEMPT && list_empty(&ready_list))

        goto ret_0;

    if (stype == FIBRIL_FROM_MANAGER) {

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

            goto ret_0;

        /*

         * Do not preempt if there is not enough threads to run the

         * ready fibrils which are not serialized.

         */

        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 (stype == FIBRIL_TO_MANAGER || stype == FIBRIL_FROM_DEAD) {

        while (list_empty(&manager_list)) {

            futex_up(&fibril_futex);

            async_create_manager();

            futex_down(&fibril_futex);

        }

    }

    srcf = __tcb_get()->fibril_data;

    if (stype != FIBRIL_FROM_DEAD) {

        /* Save current state */

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

            if (serialization_count)

                srcf->flags &= ~FIBRIL_SERIALIZED;

            if (srcf->clean_after_me) {

                /*

                 * Cleanup after the dead fibril from which we

                 * restored context here.

                 */

                void *stack = srcf->clean_after_me->stack;

                if (stack) {

                    /*

                     * This check is necessary because a

                     * thread could have exited like a

                     * normal fibril using the

                     * FIBRIL_FROM_DEAD switch type. In that

                     * case, its fibril will not have the

                     * stack member filled.

                     */

                    free(stack);

                }

                fibril_teardown(srcf->clean_after_me);

                srcf->clean_after_me = NULL;

            }

            return 1;   /* futex_up already done here */

        }

        /* Save myself to the correct run list */

        if (stype == FIBRIL_PREEMPT)

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

        else if (stype == FIBRIL_FROM_MANAGER) {

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

            threads_in_manager--;

        } else {   

            /*

             * If stype == FIBRIL_TO_MANAGER, don't put ourselves to

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

             * be lost.

             */

        }

    }

    /* Choose a new fibril to run */

    if (stype == FIBRIL_TO_MANAGER || stype == FIBRIL_FROM_DEAD) {

        dstf = list_get_instance(manager_list.next, fibril_t, link);

        if (serialization_count && stype == FIBRIL_TO_MANAGER) {

            serialized_threads++;

            srcf->flags |= FIBRIL_SERIALIZED;

        }

        threads_in_manager++;

        if (stype == FIBRIL_FROM_DEAD)

            dstf->clean_after_me = srcf;

    } else {

        if (!list_empty(&serialized_list)) {

            dstf = list_get_instance(serialized_list.next, fibril_t,

                link);

            serialized_threads--;

        } else {

            dstf = list_get_instance(ready_list.next, fibril_t,

                link);

        }

    }

    list_remove(&dstf->link);

    futex_up(&fibril_futex);

    context_restore(&dstf->ctx);

    /* not reached */

ret_0:

    futex_up(&fibril_futex);

    return retval;

}

/** Create a new fibril.

 *

 * @param func      Implementing function of the new fibril.

 * @param arg       Argument to pass to func.

 *

 * @return      Return 0 on failure or TLS of the new fibril.

 */

fid_t fibril_create(int (*func)(void *), void *arg)

{

    fibril_t *f;

    f = fibril_setup();

    if (!f)

        return 0;

    f->stack = (char *) malloc(FIBRIL_INITIAL_STACK_PAGES_NO *

        getpagesize());

    if (!f->stack) {

        fibril_teardown(f);

        return 0;

    }

    f->func = func;

    f->arg = arg;

    context_save(&f->ctx);

    context_set(&f->ctx, FADDR(fibril_main), f->stack,

        FIBRIL_INITIAL_STACK_PAGES_NO * getpagesize(), f->tcb);

    return (fid_t) f;

}

/** Add a fibril to the ready list.

 *

 * @param fid       Pointer to the fibril structure of the fibril to be

 *          added.

 */

void fibril_add_ready(fid_t fid)

{

    fibril_t *f;

    f = (fibril_t *) fid;

    futex_down(&fibril_futex);

    if ((f->flags & FIBRIL_SERIALIZED))

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

    else

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

    futex_up(&fibril_futex);

}

/** Add a fibril to the manager list.

 *

 * @param fid       Pointer to the fibril structure of the fibril to be

 *          added.

 */

void fibril_add_manager(fid_t fid)

{

    fibril_t *f;

    f = (fibril_t *) fid;

    futex_down(&fibril_futex);

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

    futex_up(&fibril_futex);

}

/** Remove one manager from the manager list. */

void fibril_remove_manager(void)

{

    futex_down(&fibril_futex);

    if (list_empty(&manager_list)) {

        futex_up(&fibril_futex);

        return;

    }

    list_remove(manager_list.next);

    futex_up(&fibril_futex);

}

/** Return fibril id of the currently running fibril.

 *

 * @return fibril ID of the currently running fibril.

 *

 */

fid_t fibril_get_id(void)

{

    return (fid_t) __tcb_get()->fibril_data;

}

/** Disable preemption

 *

 * If the fibril 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.

 *

 */

void fibril_inc_sercount(void)

{

    serialization_count++;

}

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

void fibril_dec_sercount(void)

{

    serialization_count--;

}

/** @}

 */