auto import from //depot/cupcake/@135843
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The Android Open Source Project
212
libc/bionic/semaphore.c
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212
libc/bionic/semaphore.c
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/*
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* Copyright (C) 2008 The Android Open Source Project
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <semaphore.h>
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#include <errno.h>
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#include <sys/time.h>
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#include <sys/atomics.h>
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#include <time.h>
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int sem_init(sem_t *sem, int pshared, unsigned int value)
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{
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if (sem == NULL) {
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errno = EINVAL;
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return -1;
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}
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if (pshared != 0) {
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errno = ENOSYS;
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return -1;
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}
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sem->count = value;
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return 0;
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}
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int sem_destroy(sem_t *sem)
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{
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if (sem == NULL) {
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errno = EINVAL;
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return -1;
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}
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if (sem->count == 0) {
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errno = EBUSY;
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return -1;
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}
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return 0;
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}
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sem_t *sem_open(const char *name, int oflag, ...)
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{
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name=name;
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oflag=oflag;
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errno = ENOSYS;
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return SEM_FAILED;
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}
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int sem_close(sem_t *sem)
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{
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if (sem == NULL) {
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errno = EINVAL;
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return -1;
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}
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errno = ENOSYS;
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return -1;
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}
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int sem_unlink(const char * name)
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{
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errno = ENOSYS;
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return -1;
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}
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static int
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__atomic_dec_if_positive( volatile unsigned int* pvalue )
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{
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unsigned int old;
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do {
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old = *pvalue;
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}
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while ( old != 0 && __atomic_cmpxchg( (int)old, (int)old-1, (volatile int*)pvalue ) != 0 );
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return old;
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}
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int sem_wait(sem_t *sem)
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{
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if (sem == NULL) {
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errno = EINVAL;
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return -1;
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}
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for (;;) {
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if (__atomic_dec_if_positive(&sem->count))
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break;
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__futex_wait(&sem->count, 0, 0);
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}
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return 0;
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}
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int sem_timedwait(sem_t *sem, const struct timespec *abs_timeout)
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{
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int ret;
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if (sem == NULL) {
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errno = EINVAL;
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return -1;
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}
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/* POSIX says we need to try to decrement the semaphore
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* before checking the timeout value */
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if (__atomic_dec_if_positive(&sem->count))
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return 0;
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/* check it as per Posix */
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if (abs_timeout == NULL ||
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abs_timeout->tv_sec < 0 ||
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abs_timeout->tv_nsec < 0 ||
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abs_timeout->tv_nsec >= 1000000000)
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{
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errno = EINVAL;
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return -1;
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}
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for (;;) {
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struct timespec ts;
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int ret;
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/* Posix mandates CLOCK_REALTIME here */
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clock_gettime( CLOCK_REALTIME, &ts );
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ts.tv_sec = abs_timeout->tv_sec - ts.tv_sec;
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ts.tv_nsec = abs_timeout->tv_nsec - ts.tv_nsec;
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if (ts.tv_nsec < 0) {
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ts.tv_nsec += 1000000000;
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ts.tv_sec -= 1;
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}
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if (ts.tv_sec < 0 || ts.tv_nsec < 0) {
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errno = ETIMEDOUT;
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return -1;
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}
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ret = __futex_wait(&sem->count, 0, &ts);
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/* return in case of timeout or interrupt */
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if (ret == -ETIMEDOUT || ret == -EINTR) {
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errno = -ret;
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return -1;
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}
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if (__atomic_dec_if_positive(&sem->count))
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break;
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}
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return 0;
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}
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int sem_post(sem_t *sem)
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{
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if (sem == NULL)
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return EINVAL;
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if (__atomic_inc((volatile int*)&sem->count) == 0)
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__futex_wake(&sem->count, 1);
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return 0;
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}
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int sem_trywait(sem_t *sem)
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{
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if (sem == NULL) {
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errno = EINVAL;
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return -1;
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}
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if (__atomic_dec_if_positive(&sem->count) > 0) {
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return 0;
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} else {
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return EAGAIN;
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}
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}
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int sem_getvalue(sem_t *sem, int *sval)
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{
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if (sem == NULL || sval == NULL) {
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errno = EINVAL;
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return -1;
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}
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*sval = sem->count;
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return 0;
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}
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