/*
 * 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 <stack.h>
#include <tls.h>
#include <stdlib.h>
#include <abi/mm/as.h>
#include <as.h>
#include <stdio.h>
#include <libarch/barrier.h>
#include <context.h>
#include <futex.h>
#include <assert.h>
#include <async.h>

#ifdef FUTEX_UPGRADABLE
#include <rcu.h>
#endif

/**
 * This futex serializes access to ready_list,
 * manager_list and fibril_list.
 */
static futex_t fibril_futex = FUTEX_INITIALIZER;

static LIST_INITIALIZE(ready_list);
static LIST_INITIALIZE(manager_list);
static LIST_INITIALIZE(fibril_list);

/** 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.
 *
 */
static void fibril_main(void)
{
	fibril_t *fibril = __tcb_get()->fibril_data;

#ifdef FUTEX_UPGRADABLE
	rcu_register_fibril();
#endif

	/* Call the implementing function. */
	fibril->retval = fibril->func(fibril->arg);

	futex_down(&async_futex);
	fibril_switch(FIBRIL_FROM_DEAD);
	/* Not reached */
}

/** Setup fibril information into TCB structure
 *
 */
fibril_t *fibril_setup(void)
{
	tcb_t *tcb = tls_make();
	if (!tcb)
		return NULL;

	fibril_t *fibril = malloc(sizeof(fibril_t));
	if (!fibril) {
		tls_free(tcb);
		return NULL;
	}

	tcb->fibril_data = fibril;
	fibril->tcb = tcb;

	fibril->func = NULL;
	fibril->arg = NULL;
	fibril->stack = NULL;
	fibril->clean_after_me = NULL;
	fibril->retval = 0;
	fibril->flags = 0;

	fibril->waits_for = NULL;

	fibril->switches = 0;

	/*
	 * We are called before __tcb_set(), so we need to use
	 * futex_down/up() instead of futex_lock/unlock() that
	 * may attempt to access TLS.
	 */
	futex_down(&fibril_futex);
	list_append(&fibril->all_link, &fibril_list);
	futex_up(&fibril_futex);

	return fibril;
}

void fibril_teardown(fibril_t *fibril, bool locked)
{
	if (!locked)
		futex_lock(&fibril_futex);
	list_remove(&fibril->all_link);
	if (!locked)
		futex_unlock(&fibril_futex);
	tls_free(fibril->tcb);
	free(fibril);
}

/** Switch from the current fibril.
 *
 * If stype is FIBRIL_TO_MANAGER or FIBRIL_FROM_DEAD, the async_futex must
 * 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 0 if there is no ready fibril,
 * @return 1 otherwise.
 *
 */
int fibril_switch(fibril_switch_type_t stype)
{
	futex_lock(&fibril_futex);

	fibril_t *srcf = __tcb_get()->fibril_data;
	fibril_t *dstf = NULL;

	/* Choose a new fibril to run */
	switch (stype) {
	case FIBRIL_TO_MANAGER:
	case FIBRIL_FROM_DEAD:
		/* Make sure the async_futex is held. */
		assert((atomic_signed_t) async_futex.val.count <= 0);

		/* If we are going to manager and none exists, create it */
		while (list_empty(&manager_list)) {
			futex_unlock(&fibril_futex);
			async_create_manager();
			futex_lock(&fibril_futex);
		}

		dstf = list_get_instance(list_first(&manager_list),
		    fibril_t, link);

		if (stype == FIBRIL_FROM_DEAD)
			dstf->clean_after_me = srcf;
		break;
	case FIBRIL_PREEMPT:
	case FIBRIL_FROM_MANAGER:
		if (list_empty(&ready_list)) {
			futex_unlock(&fibril_futex);
			return 0;
		}

		dstf = list_get_instance(list_first(&ready_list), fibril_t,
		    link);
		break;
	}
	list_remove(&dstf->link);

	/* Put the current fibril into the correct run list */
	switch (stype) {
	case FIBRIL_PREEMPT:
		list_append(&srcf->link, &ready_list);
		break;
	case FIBRIL_FROM_MANAGER:
		list_append(&srcf->link, &manager_list);
		break;
	case FIBRIL_FROM_DEAD:
		// Nothing.
		break;
	case FIBRIL_TO_MANAGER:
		srcf->switches++;
		/*
		 * Don't put the current fibril into any list, it should
		 * already be somewhere, or it will be lost.
		 */
		break;
	}

	futex_unlock(&fibril_futex);

#ifdef FUTEX_UPGRADABLE
	if (stype == FIBRIL_FROM_DEAD) {
		rcu_deregister_fibril();
	}
#endif

	/* Swap to the next fibril. */
	context_swap(&srcf->ctx, &dstf->ctx);

	/* Restored by another fibril! */

	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.
			 */
			as_area_destroy(stack);
		}
		fibril_teardown(srcf->clean_after_me, true);
		srcf->clean_after_me = NULL;
	}

	return 1;
}

/** Create a new fibril.
 *
 * @param func Implementing function of the new fibril.
 * @param arg Argument to pass to func.
 * @param stksz Stack size in bytes.
 *
 * @return 0 on failure or TLS of the new fibril.
 *
 */
fid_t fibril_create_generic(errno_t (*func)(void *), void *arg, size_t stksz)
{
	fibril_t *fibril;

	fibril = fibril_setup();
	if (fibril == NULL)
		return 0;

	size_t stack_size = (stksz == FIBRIL_DFLT_STK_SIZE) ?
	    stack_size_get() : stksz;
	fibril->stack = as_area_create(AS_AREA_ANY, stack_size,
	    AS_AREA_READ | AS_AREA_WRITE | AS_AREA_CACHEABLE | AS_AREA_GUARD |
	    AS_AREA_LATE_RESERVE, AS_AREA_UNPAGED);
	if (fibril->stack == (void *) -1) {
		fibril_teardown(fibril, false);
		return 0;
	}

	fibril->func = func;
	fibril->arg = arg;

	context_create_t sctx = {
		.fn = fibril_main,
		.stack_base = fibril->stack,
		.stack_size = stack_size,
		.tls = fibril->tcb,
	};

	context_create(&fibril->ctx, &sctx);
	return (fid_t) fibril;
}

/** Delete a fibril that has never run.
 *
 * Free resources of a fibril that has been created with fibril_create()
 * but never readied using fibril_add_ready().
 *
 * @param fid Pointer to the fibril structure of the fibril to be
 *            added.
 */
void fibril_destroy(fid_t fid)
{
	fibril_t *fibril = (fibril_t *) fid;

	as_area_destroy(fibril->stack);
	fibril_teardown(fibril, false);
}

/** 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 *fibril = (fibril_t *) fid;

	futex_lock(&fibril_futex);
	list_append(&fibril->link, &ready_list);
	futex_unlock(&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 *fibril = (fibril_t *) fid;

	futex_lock(&fibril_futex);
	list_append(&fibril->link, &manager_list);
	futex_unlock(&fibril_futex);
}

/** Remove one manager from the manager list. */
void fibril_remove_manager(void)
{
	futex_lock(&fibril_futex);
	if (!list_empty(&manager_list))
		list_remove(list_first(&manager_list));
	futex_unlock(&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;
}

/** @}
 */