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/*
* Copyright (C) 2008 The Android Open Source Project
* 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.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS 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
* COPYRIGHT OWNER 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 <semaphore.h>
#include <errno.h>
#include <sys/time.h>
#include <sys/atomics.h>
#include <time.h>
int sem_init(sem_t *sem, int pshared, unsigned int value)
{
if (sem == NULL) {
errno = EINVAL;
return -1;
}
if (pshared != 0) {
errno = ENOSYS;
return -1;
}
sem->count = value;
return 0;
}
int sem_destroy(sem_t *sem)
{
if (sem == NULL) {
errno = EINVAL;
return -1;
}
if (sem->count == 0) {
errno = EBUSY;
return -1;
}
return 0;
}
sem_t *sem_open(const char *name, int oflag, ...)
{
name=name;
oflag=oflag;
errno = ENOSYS;
return SEM_FAILED;
}
int sem_close(sem_t *sem)
{
if (sem == NULL) {
errno = EINVAL;
return -1;
}
errno = ENOSYS;
return -1;
}
int sem_unlink(const char * name)
{
errno = ENOSYS;
return -1;
}
static int
__atomic_dec_if_positive( volatile unsigned int* pvalue )
{
unsigned int old;
do {
old = *pvalue;
}
while ( old != 0 && __atomic_cmpxchg( (int)old, (int)old-1, (volatile int*)pvalue ) != 0 );
return old;
}
int sem_wait(sem_t *sem)
{
if (sem == NULL) {
errno = EINVAL;
return -1;
}
for (;;) {
if (__atomic_dec_if_positive(&sem->count))
break;
__futex_wait(&sem->count, 0, 0);
}
return 0;
}
int sem_timedwait(sem_t *sem, const struct timespec *abs_timeout)
{
int ret;
if (sem == NULL) {
errno = EINVAL;
return -1;
}
/* POSIX says we need to try to decrement the semaphore
* before checking the timeout value */
if (__atomic_dec_if_positive(&sem->count))
return 0;
/* check it as per Posix */
if (abs_timeout == NULL ||
abs_timeout->tv_sec < 0 ||
abs_timeout->tv_nsec < 0 ||
abs_timeout->tv_nsec >= 1000000000)
{
errno = EINVAL;
return -1;
}
for (;;) {
struct timespec ts;
int ret;
/* Posix mandates CLOCK_REALTIME here */
clock_gettime( CLOCK_REALTIME, &ts );
ts.tv_sec = abs_timeout->tv_sec - ts.tv_sec;
ts.tv_nsec = abs_timeout->tv_nsec - ts.tv_nsec;
if (ts.tv_nsec < 0) {
ts.tv_nsec += 1000000000;
ts.tv_sec -= 1;
}
if (ts.tv_sec < 0 || ts.tv_nsec < 0) {
errno = ETIMEDOUT;
return -1;
}
ret = __futex_wait(&sem->count, 0, &ts);
/* return in case of timeout or interrupt */
if (ret == -ETIMEDOUT || ret == -EINTR) {
errno = -ret;
return -1;
}
if (__atomic_dec_if_positive(&sem->count))
break;
}
return 0;
}
int sem_post(sem_t *sem)
{
if (sem == NULL)
return EINVAL;
if (__atomic_inc((volatile int*)&sem->count) == 0)
__futex_wake(&sem->count, 1);
return 0;
}
int sem_trywait(sem_t *sem)
{
if (sem == NULL) {
errno = EINVAL;
return -1;
}
if (__atomic_dec_if_positive(&sem->count) > 0) {
return 0;
} else {
return EAGAIN;
}
}
int sem_getvalue(sem_t *sem, int *sval)
{
if (sem == NULL || sval == NULL) {
errno = EINVAL;
return -1;
}
*sval = sem->count;
return 0;
}
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