freebsd-dev/lib/libthr/thread/thr_sem.c
2008-04-29 03:58:18 +00:00

292 lines
6.7 KiB
C

/*
* Copyright (C) 2005 David Xu <davidxu@freebsd.org>.
* 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 "namespace.h"
#include <sys/types.h>
#include <sys/queue.h>
#include <errno.h>
#include <fcntl.h>
#include <pthread.h>
#include <semaphore.h>
#include <stdlib.h>
#include <time.h>
#include <_semaphore.h>
#include "un-namespace.h"
#include "thr_private.h"
__weak_reference(_sem_init, sem_init);
__weak_reference(_sem_destroy, sem_destroy);
__weak_reference(_sem_getvalue, sem_getvalue);
__weak_reference(_sem_trywait, sem_trywait);
__weak_reference(_sem_wait, sem_wait);
__weak_reference(_sem_timedwait, sem_timedwait);
__weak_reference(_sem_post, sem_post);
static inline int
sem_check_validity(sem_t *sem)
{
if ((sem != NULL) && ((*sem)->magic == SEM_MAGIC))
return (0);
else {
errno = EINVAL;
return (-1);
}
}
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);
}
bzero(sem, sizeof(*sem));
/*
* Fortunatly count and nwaiters are adjacency, so we can
* use umtx_wait to wait on it, umtx_wait needs an address
* can be accessed as a long interger.
*/
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)
{
semid_t semid;
semid = (semid_t)SEM_USER;
if ((pshared != 0) && (ksem_init(&semid, value) != 0))
return (-1);
(*sem) = sem_alloc(value, semid, pshared);
if ((*sem) == NULL) {
if (pshared != 0)
ksem_destroy(semid);
return (-1);
}
return (0);
}
int
_sem_destroy(sem_t *sem)
{
int retval;
if (sem_check_validity(sem) != 0)
return (-1);
/*
* 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);
else {
retval = 0;
(*sem)->magic = 0;
}
if (retval == 0)
free(*sem);
return (retval);
}
int
_sem_getvalue(sem_t * __restrict sem, int * __restrict sval)
{
int retval;
if (sem_check_validity(sem) != 0)
return (-1);
if ((*sem)->syssem != 0)
retval = ksem_getvalue((*sem)->semid, sval);
else {
*sval = (int)(*sem)->count;
retval = 0;
}
return (retval);
}
int
_sem_trywait(sem_t *sem)
{
int val;
if (sem_check_validity(sem) != 0)
return (-1);
if ((*sem)->syssem != 0)
return (ksem_trywait((*sem)->semid));
while ((val = (*sem)->count) > 0) {
if (atomic_cmpset_acq_int(&(*sem)->count, val, val - 1))
return (0);
}
errno = EAGAIN;
return (-1);
}
static void
sem_cancel_handler(void *arg)
{
sem_t *sem = arg;
atomic_add_int(&(*sem)->nwaiters, -1);
if ((*sem)->nwaiters && (*sem)->count)
_thr_umtx_wake(&(*sem)->count, 1, 0);
}
int
_sem_wait(sem_t *sem)
{
struct pthread *curthread;
int val, retval;
if (sem_check_validity(sem) != 0)
return (-1);
curthread = _get_curthread();
if ((*sem)->syssem != 0) {
_thr_cancel_enter(curthread);
retval = ksem_wait((*sem)->semid);
_thr_cancel_leave(curthread);
return (retval);
}
_pthread_testcancel();
do {
while ((val = (*sem)->count) > 0) {
if (atomic_cmpset_acq_int(&(*sem)->count, val, val - 1))
return (0);
}
atomic_add_int(&(*sem)->nwaiters, 1);
THR_CLEANUP_PUSH(curthread, sem_cancel_handler, sem);
_thr_cancel_enter(curthread);
retval = _thr_umtx_wait_uint(&(*sem)->count, 0, NULL, 0);
_thr_cancel_leave(curthread);
THR_CLEANUP_POP(curthread, 0);
atomic_add_int(&(*sem)->nwaiters, -1);
} while (retval == 0);
errno = retval;
return (-1);
}
int
_sem_timedwait(sem_t * __restrict sem,
const struct timespec * __restrict abstime)
{
struct timespec ts, ts2;
struct pthread *curthread;
int val, retval;
if (sem_check_validity(sem) != 0)
return (-1);
curthread = _get_curthread();
if ((*sem)->syssem != 0) {
_thr_cancel_enter(curthread);
retval = ksem_timedwait((*sem)->semid, abstime);
_thr_cancel_leave(curthread);
return (retval);
}
/*
* The timeout argument is only supposed to
* be checked if the thread would have blocked.
*/
_pthread_testcancel();
do {
while ((val = (*sem)->count) > 0) {
if (atomic_cmpset_acq_int(&(*sem)->count, val, val - 1))
return (0);
}
if (abstime == NULL) {
errno = EINVAL;
return (-1);
}
clock_gettime(CLOCK_REALTIME, &ts);
TIMESPEC_SUB(&ts2, abstime, &ts);
atomic_add_int(&(*sem)->nwaiters, 1);
THR_CLEANUP_PUSH(curthread, sem_cancel_handler, sem);
_thr_cancel_enter(curthread);
retval = _thr_umtx_wait_uint((uint32_t*)&(*sem)->count, 0, &ts2, 0);
_thr_cancel_leave(curthread);
THR_CLEANUP_POP(curthread, 0);
atomic_add_int(&(*sem)->nwaiters, -1);
} while (retval == 0);
errno = retval;
return (-1);
}
/*
* sem_post() is required to be safe to call from within
* signal handlers, these code should work as that.
*/
int
_sem_post(sem_t *sem)
{
int retval = 0;
if (sem_check_validity(sem) != 0)
return (-1);
if ((*sem)->syssem != 0)
return (ksem_post((*sem)->semid));
atomic_add_rel_int(&(*sem)->count, 1);
if ((*sem)->nwaiters) {
retval = _thr_umtx_wake(&(*sem)->count, 1, 0);
if (retval != 0)
retval = -1;
}
return (retval);
}