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/*
* 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 <stdint.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(int32_t *uaddr, int op, int32_t val,
const struct timespec *timeout, int32_t *uaddr2, int32_t 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(int32_t *uaddr, int op, int32_t val,
const struct timespec *timeout, int32_t *uaddr2, int32_t val3)
{
/*
* 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;
}
return 0;
}
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