source: mainline/uspace/lib/c/generic/futex.c@ b188002

/*
 * Copyright (c) 2008 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 <futex.h>
#include <atomic.h>


/** Initialize futex counter.
 *
 * @param futex Futex.
 * @param val   Initialization value.
 *
 */
void futex_initialize(futex_t *futex, int val)
{
        atomic_set(&futex->val, val);
}


#ifdef FUTEX_UPGRADABLE

int _upgrade_futexes = 0;
static futex_t upg_and_wait_futex = FUTEX_INITIALIZER;

void futex_upgrade_all_and_wait(void)
{
        futex_down(&upg_and_wait_futex);
        
        if (!_upgrade_futexes) {
                rcu_assign(_upgrade_futexes, 1);
                _rcu_synchronize(BM_BLOCK_THREAD);
        }
        
        futex_up(&upg_and_wait_futex);
}

#endif

/** @}
 */