/*-
 * Copyright (c) 2005 David Xu <davidxu@freebsd.org>
 * Copyright (c) 2005 Matthew Dillon <dillon@backplane.com>
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``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 OR CONTRIBUTORS 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.
 */

#include <assert.h>
#include <errno.h>
#include <unistd.h>
#include <sys/time.h>

#include "sysvipc_lock_generic.h"

/*
 * This function is used to acquire a contested lock.
 */
int
__sysv_umtx_lock(volatile umtx_t *mtx, int timo)
{
	int v, errval, ret = 0;

	/* contested */
	do {
		v = *mtx;
		if (v == 2 || atomic_cmpset_acq_int(mtx, 1, 2)) {
			if (timo == 0)
				umtx_sleep(mtx, 2, timo);
			else if ( (errval = umtx_sleep(mtx, 2, timo)) > 0) {
				if (errval == EAGAIN) {
					if (atomic_cmpset_acq_int(mtx, 0, 2))
						ret = 0;
					else
						ret = ETIMEDOUT;
					break;
				}
			}
		}
	} while (!atomic_cmpset_acq_int(mtx, 0, 2));

	return (ret);
}

void
__sysv_umtx_unlock(volatile umtx_t *mtx)
{
	int v;

	for (;;) {
		v = *mtx;
		if (atomic_cmpset_acq_int(mtx, v, v-1)) {
			if (v != 1) {
				*mtx = 0;
				umtx_wakeup(mtx, 1);
			}
			break;
		}
	}
}