freebsd-dev/lib/libc/sys/sem.c
2002-10-04 21:32:00 +00:00

355 lines
7.0 KiB
C

/*
* Copyright (C) 2000 Jason Evans <jasone@freebsd.org>.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice(s), this list of conditions and the following disclaimer as
* the first lines of this file unmodified other than the possible
* addition of one or more copyright notices.
* 2. Redistributions in binary form must reproduce the above copyright
* notice(s), 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 HOLDER(S) ``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 HOLDER(S) 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.
*
* $FreeBSD$
*/
#include <stdlib.h>
#include <errno.h>
#include <fcntl.h>
#include <semaphore.h>
#include <stdarg.h>
#include <pthread.h>
#include <sys/queue.h>
#include <_semaphore.h>
#define _SEM_CHECK_VALIDITY(sem) \
if ((*(sem))->magic != SEM_MAGIC) { \
errno = EINVAL; \
retval = -1; \
goto RETURN; \
}
static sem_t sem_alloc(unsigned int value, semid_t semid, int system_sem);
static void sem_free(sem_t sem);
static LIST_HEAD(, sem) named_sems = LIST_HEAD_INITIALIZER(&named_sems);
static pthread_mutex_t named_sems_mtx = PTHREAD_MUTEX_INITIALIZER;
static void
sem_free(sem_t sem)
{
_pthread_mutex_destroy(&sem->lock);
_pthread_cond_destroy(&sem->gtzero);
sem->magic = 0;
free(sem);
}
static sem_t
sem_alloc(unsigned int value, semid_t semid, int system_sem)
{
sem_t sem;
if (value > SEM_VALUE_MAX) {
errno = EINVAL;
return (NULL);
}
sem = (sem_t)malloc(sizeof(struct sem));
if (sem == NULL) {
errno = ENOSPC;
return (NULL);
}
/*
* Initialize the semaphore.
*/
if (_pthread_mutex_init(&sem->lock, NULL) != 0) {
free(sem);
errno = ENOSPC;
return (NULL);
}
if (_pthread_cond_init(&sem->gtzero, NULL) != 0) {
_pthread_mutex_destroy(&sem->lock);
free(sem);
errno = ENOSPC;
return (NULL);
}
sem->count = (u_int32_t)value;
sem->nwaiters = 0;
sem->magic = SEM_MAGIC;
sem->semid = semid;
sem->syssem = system_sem;
return (sem);
}
int
sem_init(sem_t *sem, int pshared, unsigned int value)
{
int retval, got_system_sem;
semid_t semid;
got_system_sem = 0;
semid = SEM_USER;
/*
* Range check the arguments.
*/
if (pshared != 0) {
retval = ksem_init(&semid, value);
if (retval == -1)
goto RETURN;
got_system_sem = 1;
}
(*sem) = sem_alloc(value, semid, got_system_sem);
if ((*sem) == NULL)
retval = -1;
else
retval = 0;
RETURN:
if (retval != 0 && got_system_sem)
ksem_destroy(semid);
return retval;
}
int
sem_destroy(sem_t *sem)
{
int retval;
_SEM_CHECK_VALIDITY(sem);
_pthread_mutex_lock(&(*sem)->lock);
/*
* If this is a system semaphore let the kernel track it otherwise
* make sure there are no waiters.
*/
if ((*sem)->syssem != 0) {
retval = ksem_destroy((*sem)->semid);
if (retval == -1) {
_pthread_mutex_unlock(&(*sem)->lock);
goto RETURN;
}
} else if ((*sem)->nwaiters > 0) {
_pthread_mutex_unlock(&(*sem)->lock);
errno = EBUSY;
retval = -1;
goto RETURN;
}
_pthread_mutex_unlock(&(*sem)->lock);
sem_free(*sem);
retval = 0;
RETURN:
return retval;
}
sem_t *
sem_open(const char *name, int oflag, ...)
{
sem_t *sem;
sem_t s;
semid_t semid;
mode_t mode;
unsigned int value;
mode = 0;
value = 0;
if ((oflag & O_CREAT) != 0) {
va_list ap;
va_start(ap, oflag);
mode = va_arg(ap, int);
value = va_arg(ap, unsigned int);
va_end(ap);
}
/*
* we can be lazy and let the kernel handle the "oflag",
* we'll just merge duplicate IDs into our list.
*/
if (ksem_open(&semid, name, oflag, mode, value) == -1)
return (SEM_FAILED);
/*
* search for a duplicate ID, we must return the same sem_t *
* if we locate one.
*/
_pthread_mutex_lock(&named_sems_mtx);
LIST_FOREACH(s, &named_sems, entry) {
if (s->semid == semid) {
_pthread_mutex_unlock(&named_sems_mtx);
return (s->backpointer);
}
}
sem = (sem_t *)malloc(sizeof(*sem));
if (sem == NULL)
goto err;
*sem = sem_alloc(value, semid, 1);
if ((*sem) == NULL)
goto err;
_pthread_mutex_unlock(&named_sems_mtx);
(*sem)->backpointer = sem;
return (sem);
err:
_pthread_mutex_unlock(&named_sems_mtx);
ksem_close(semid);
if (sem != NULL) {
if (*sem != NULL)
sem_free(*sem);
else
errno = ENOSPC;
free(sem);
} else {
errno = ENOSPC;
}
return (SEM_FAILED);
}
int
sem_close(sem_t *sem)
{
if ((*sem)->syssem == 0) {
errno = EINVAL;
return (-1);
}
_pthread_mutex_lock(&named_sems_mtx);
if (ksem_close((*sem)->semid) == -1) {
_pthread_mutex_unlock(&named_sems_mtx);
return (-1);
}
LIST_REMOVE((*sem), entry);
_pthread_mutex_unlock(&named_sems_mtx);
sem_free(*sem);
free(sem);
return (0);
}
int
sem_unlink(const char *name)
{
return (ksem_unlink(name));
}
int
sem_wait(sem_t *sem)
{
int retval;
_SEM_CHECK_VALIDITY(sem);
if ((*sem)->syssem != 0) {
retval = ksem_wait((*sem)->semid);
goto RETURN;
}
_pthread_mutex_lock(&(*sem)->lock);
while ((*sem)->count == 0) {
(*sem)->nwaiters++;
_pthread_cond_wait(&(*sem)->gtzero, &(*sem)->lock);
(*sem)->nwaiters--;
}
(*sem)->count--;
_pthread_mutex_unlock(&(*sem)->lock);
retval = 0;
RETURN:
return retval;
}
int
sem_trywait(sem_t *sem)
{
int retval;
_SEM_CHECK_VALIDITY(sem);
if ((*sem)->syssem != 0) {
retval = ksem_trywait((*sem)->semid);
goto RETURN;
}
_pthread_mutex_lock(&(*sem)->lock);
if ((*sem)->count > 0) {
(*sem)->count--;
retval = 0;
} else {
errno = EAGAIN;
retval = -1;
}
_pthread_mutex_unlock(&(*sem)->lock);
RETURN:
return retval;
}
int
sem_post(sem_t *sem)
{
int retval;
_SEM_CHECK_VALIDITY(sem);
if ((*sem)->syssem != 0) {
retval = ksem_post((*sem)->semid);
goto RETURN;
}
_pthread_mutex_lock(&(*sem)->lock);
(*sem)->count++;
if ((*sem)->nwaiters > 0)
_pthread_cond_signal(&(*sem)->gtzero);
_pthread_mutex_unlock(&(*sem)->lock);
retval = 0;
RETURN:
return retval;
}
int
sem_getvalue(sem_t * __restrict sem, int * __restrict sval)
{
int retval;
_SEM_CHECK_VALIDITY(sem);
if ((*sem)->syssem != 0) {
retval = ksem_getvalue((*sem)->semid, sval);
goto RETURN;
}
_pthread_mutex_lock(&(*sem)->lock);
*sval = (int)(*sem)->count;
_pthread_mutex_unlock(&(*sem)->lock);
retval = 0;
RETURN:
return retval;
}