[userspace-rcu.git] / compat_futex.c

/*
 * compat_futex.c
 *
 * Userspace RCU library - sys_futex compatibility code
 *
 * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include <stdio.h>
#include <pthread.h>
#include <signal.h>
#include <assert.h>
#include <errno.h>
#include <poll.h>

#include <urcu/arch.h>
#include <urcu/futex.h>

static pthread_mutex_t compat_futex_lock = PTHREAD_MUTEX_INITIALIZER;
static pthread_cond_t compat_futex_cond = PTHREAD_COND_INITIALIZER;

/*
 * _NOT SIGNAL-SAFE_. pthread_cond is not signal-safe anyway. Though.
 * For now, timeout, uaddr2 and val3 are unused.
 * Waiter will relinquish the CPU until woken up.
 */

int compat_futex_noasync(int *uaddr, int op, int val,
	const struct timespec *timeout, int *uaddr2, int val3)
{
	int ret, i, gret = 0;

	/*
	 * Check if NULL. Don't let users expect that they are taken into
	 * account. 
	 */
	assert(!timeout);
	assert(!uaddr2);
	assert(!val3);

	/*
	 * memory barriers to serialize with the previous uaddr modification.
	 */
	cmm_smp_mb();

	ret = pthread_mutex_lock(&compat_futex_lock);
	assert(!ret);
	switch (op) {
	case FUTEX_WAIT:
		if (*uaddr != val)
			goto end;
		pthread_cond_wait(&compat_futex_cond, &compat_futex_lock);
		break;
	case FUTEX_WAKE:
		for (i = 0; i < val; i++)
			pthread_cond_signal(&compat_futex_cond);
		break;
	default:
		gret = -EINVAL;
	}
end:
	ret = pthread_mutex_unlock(&compat_futex_lock);
	assert(!ret);
	return gret;
}

/*
 * _ASYNC SIGNAL-SAFE_.
 * For now, timeout, uaddr2 and val3 are unused.
 * Waiter will busy-loop trying to read the condition.
 */

int compat_futex_async(int *uaddr, int op, int val,
	const struct timespec *timeout, int *uaddr2, int val3)
{
	int ret, i;

	/*
	 * Check if NULL. Don't let users expect that they are taken into
	 * account. 
	 */
	assert(!timeout);
	assert(!uaddr2);
	assert(!val3);

	/*
	 * Ensure previous memory operations on uaddr have completed.
	 */
	cmm_smp_mb();

	switch (op) {
	case FUTEX_WAIT:
		while (*uaddr == val)
			poll(NULL, 0, 10);
		break;
	case FUTEX_WAKE:
		break;
	default:
		return -EINVAL;
	}
}
Commit	Line	Data
	1	/*
	2	* compat_futex.c
	3	*
	4	* Userspace RCU library - sys_futex compatibility code
	5	*
	6	* Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
	7	*
	8	* This library is free software; you can redistribute it and/or
	9	* modify it under the terms of the GNU Lesser General Public
	10	* License as published by the Free Software Foundation; either
	11	* version 2.1 of the License, or (at your option) any later version.
	12	*
	13	* This library is distributed in the hope that it will be useful,
	14	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	15	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
	16	* Lesser General Public License for more details.
	17	*
	18	* You should have received a copy of the GNU Lesser General Public
	19	* License along with this library; if not, write to the Free Software
	20	* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
	21	*/
	22
	23	#include <stdio.h>
	24	#include <pthread.h>
	25	#include <signal.h>
	26	#include <assert.h>
	27	#include <errno.h>
	28	#include <poll.h>
	29
	30	#include <urcu/arch.h>
	31	#include <urcu/futex.h>
	32
	33	static pthread_mutex_t compat_futex_lock = PTHREAD_MUTEX_INITIALIZER;
	34	static pthread_cond_t compat_futex_cond = PTHREAD_COND_INITIALIZER;
	35
	36	/*
	37	* _NOT SIGNAL-SAFE_. pthread_cond is not signal-safe anyway. Though.
	38	* For now, timeout, uaddr2 and val3 are unused.
	39	* Waiter will relinquish the CPU until woken up.
	40	*/
	41
	42	int compat_futex_noasync(int *uaddr, int op, int val,
	43	const struct timespec timeout, int uaddr2, int val3)
	44	{
	45	int ret, i, gret = 0;
	46
	47	/*
	48	* Check if NULL. Don't let users expect that they are taken into
	49	* account.
	50	*/
	51	assert(!timeout);
	52	assert(!uaddr2);
	53	assert(!val3);
	54
	55	/*
	56	* memory barriers to serialize with the previous uaddr modification.
	57	*/
	58	cmm_smp_mb();
	59
	60	ret = pthread_mutex_lock(&compat_futex_lock);
	61	assert(!ret);
	62	switch (op) {
	63	case FUTEX_WAIT:
	64	if (*uaddr != val)
	65	goto end;
	66	pthread_cond_wait(&compat_futex_cond, &compat_futex_lock);
	67	break;
	68	case FUTEX_WAKE:
	69	for (i = 0; i < val; i++)
	70	pthread_cond_signal(&compat_futex_cond);
	71	break;
	72	default:
	73	gret = -EINVAL;
	74	}
	75	end:
	76	ret = pthread_mutex_unlock(&compat_futex_lock);
	77	assert(!ret);
	78	return gret;
	79	}
	80
	81	/*
	82	* _ASYNC SIGNAL-SAFE_.
	83	* For now, timeout, uaddr2 and val3 are unused.
	84	* Waiter will busy-loop trying to read the condition.
	85	*/
	86
	87	int compat_futex_async(int *uaddr, int op, int val,
	88	const struct timespec timeout, int uaddr2, int val3)
	89	{
	90	int ret, i;
	91
	92	/*
	93	* Check if NULL. Don't let users expect that they are taken into
	94	* account.
	95	*/
	96	assert(!timeout);
	97	assert(!uaddr2);
	98	assert(!val3);
	99
	100	/*
	101	* Ensure previous memory operations on uaddr have completed.
	102	*/
	103	cmm_smp_mb();
	104
	105	switch (op) {
	106	case FUTEX_WAIT:
	107	while (*uaddr == val)
	108	poll(NULL, 0, 10);
	109	break;
	110	case FUTEX_WAKE:
	111	break;
	112	default:
	113	return -EINVAL;
	114	}
	115	}