/*
 * Copyright (c) 2009 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 <fibril_sync.h>
#include <fibril.h>
#include <async.h>
#include <async_priv.h>
#include <adt/list.h>
#include <futex.h>
#include <sys/time.h>
#include <errno.h>
#include <assert.h>

static void optimize_execution_power(void)
{
	/*
	 * When waking up a worker fibril previously blocked in fibril
	 * synchronization, chances are that there is an idle manager fibril
	 * waiting for IPC, that could start executing the awakened worker
	 * fibril right away. We try to detect this and bring the manager
	 * fibril back to fruitful work.
	 */
	if (atomic_get(&threads_in_ipc_wait) > 0)
		ipc_poke();
}

void fibril_mutex_initialize(fibril_mutex_t *fm)
{
	fm->counter = 1;
	list_initialize(&fm->waiters);
}

void fibril_mutex_lock(fibril_mutex_t *fm)
{
	futex_down(&async_futex);
	if (fm->counter-- <= 0) {
		fibril_t *f = (fibril_t *) fibril_get_id();
		list_append(&f->link, &fm->waiters);
		fibril_switch(FIBRIL_TO_MANAGER);
	} else {
		futex_up(&async_futex);
	}
}

bool fibril_mutex_trylock(fibril_mutex_t *fm)
{
	bool locked = false;
	
	futex_down(&async_futex);
	if (fm->counter > 0) {
		fm->counter--;
		locked = true;
	}
	futex_up(&async_futex);
	
	return locked;
}

static void _fibril_mutex_unlock_unsafe(fibril_mutex_t *fm)
{
	assert(fm->counter <= 0);
	if (fm->counter++ < 0) {
		link_t *tmp;
		fibril_t *f;
	
		assert(!list_empty(&fm->waiters));
		tmp = fm->waiters.next;
		f = list_get_instance(tmp, fibril_t, link);
		list_remove(&f->link);
		fibril_add_ready((fid_t) f);
		optimize_execution_power();
	}
}

void fibril_mutex_unlock(fibril_mutex_t *fm)
{
	futex_down(&async_futex);
	_fibril_mutex_unlock_unsafe(fm);
	futex_up(&async_futex);
}

void fibril_rwlock_initialize(fibril_rwlock_t *frw)
{
	frw->writers = 0;
	frw->readers = 0;
	list_initialize(&frw->waiters);
}

void fibril_rwlock_read_lock(fibril_rwlock_t *frw)
{
	futex_down(&async_futex);
	if (frw->writers) {
		fibril_t *f = (fibril_t *) fibril_get_id();
		f->flags &= ~FIBRIL_WRITER;
		list_append(&f->link, &frw->waiters);
		fibril_switch(FIBRIL_TO_MANAGER);
	} else {
		frw->readers++;
		futex_up(&async_futex);
	}
}

void fibril_rwlock_write_lock(fibril_rwlock_t *frw)
{
	futex_down(&async_futex);
	if (frw->writers || frw->readers) {
		fibril_t *f = (fibril_t *) fibril_get_id();
		f->flags |= FIBRIL_WRITER;
		list_append(&f->link, &frw->waiters);
		fibril_switch(FIBRIL_TO_MANAGER);
	} else {
		frw->writers++;
		futex_up(&async_futex);
	}
}

static void _fibril_rwlock_common_unlock(fibril_rwlock_t *frw)
{
	futex_down(&async_futex);
	assert(frw->readers || (frw->writers == 1));
	if (frw->readers) {
		if (--frw->readers)
			goto out;
	} else {
		frw->writers--;
	}
	
	assert(!frw->readers && !frw->writers);
	
	while (!list_empty(&frw->waiters)) {
		link_t *tmp = frw->waiters.next;
		fibril_t *f = list_get_instance(tmp, fibril_t, link);
		
		if (f->flags & FIBRIL_WRITER) {
			if (frw->readers)
				break;
			list_remove(&f->link);
			fibril_add_ready((fid_t) f);
			frw->writers++;
			optimize_execution_power();
			break;
		} else {
			list_remove(&f->link);
			fibril_add_ready((fid_t) f);
			frw->readers++;
			optimize_execution_power();
		}
	}
out:
	futex_up(&async_futex);
}

void fibril_rwlock_read_unlock(fibril_rwlock_t *frw)
{
	_fibril_rwlock_common_unlock(frw);
}

void fibril_rwlock_write_unlock(fibril_rwlock_t *frw)
{
	_fibril_rwlock_common_unlock(frw);
}

void fibril_condvar_initialize(fibril_condvar_t *fcv)
{
	list_initialize(&fcv->waiters);
}

int
fibril_condvar_wait_timeout(fibril_condvar_t *fcv, fibril_mutex_t *fm,
    suseconds_t timeout)
{
	awaiter_t wdata;

	if (timeout < 0)
		return ETIMEOUT;

	wdata.fid = fibril_get_id();
	wdata.active = false;
	
	wdata.to_event.inlist = timeout > 0;
	wdata.to_event.occurred = false;
	link_initialize(&wdata.to_event.link);

	wdata.wu_event.inlist = true;
	link_initialize(&wdata.wu_event.link);

	futex_down(&async_futex);
	if (timeout) {
		gettimeofday(&wdata.to_event.expires, NULL);
		tv_add(&wdata.to_event.expires, timeout);
		async_insert_timeout(&wdata);
	}
	list_append(&wdata.wu_event.link, &fcv->waiters);
	_fibril_mutex_unlock_unsafe(fm);
	fibril_switch(FIBRIL_TO_MANAGER);
	fibril_mutex_lock(fm);

	/* async_futex not held after fibril_switch() */
	futex_down(&async_futex);
	if (wdata.to_event.inlist)
		list_remove(&wdata.to_event.link);
	if (wdata.wu_event.inlist)
		list_remove(&wdata.wu_event.link);
	futex_up(&async_futex);
	
	return wdata.to_event.occurred ? ETIMEOUT : EOK;
}

void fibril_condvar_wait(fibril_condvar_t *fcv, fibril_mutex_t *fm)
{
	int rc;

	rc = fibril_condvar_wait_timeout(fcv, fm, 0);
	assert(rc == EOK);
}

static void _fibril_condvar_wakeup_common(fibril_condvar_t *fcv, bool once)
{
	link_t *tmp;
	awaiter_t *wdp;

	futex_down(&async_futex);
	while (!list_empty(&fcv->waiters)) {
		tmp = fcv->waiters.next;
		wdp = list_get_instance(tmp, awaiter_t, wu_event.link);
		list_remove(&wdp->wu_event.link);
		wdp->wu_event.inlist = false;
		if (!wdp->active) {
			wdp->active = true;
			fibril_add_ready(wdp->fid);
			optimize_execution_power();
			if (once)
				break;
		}
	}
	futex_up(&async_futex);
}

void fibril_condvar_signal(fibril_condvar_t *fcv)
{
	_fibril_condvar_wakeup_common(fcv, true);
}

void fibril_condvar_broadcast(fibril_condvar_t *fcv)
{
	_fibril_condvar_wakeup_common(fcv, false);
}

/** @}
 */