freebsd-dev/lib/libc/gen/sem_new.c
David Xu df1f1bae9e In revision 231989, we pass a 16-bit clock ID into kernel, however
according to POSIX document, the clock ID may be dynamically allocated,
it unlikely will be in 64K forever. To make it future compatible, we
pack all timeout information into a new structure called _umtx_time, and
use fourth argument as a size indication, a zero means it is old code
using timespec as timeout value, but the new structure also includes flags
and a clock ID, so the size argument is different than before, and it is
non-zero. With this change, it is possible that a thread can sleep
on any supported clock, though current kernel code does not have such a
POSIX clock driver system.
2012-02-25 02:12:17 +00:00

448 lines
9.4 KiB
C

/*
* Copyright (C) 2010 David Xu <davidxu@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 <sys/mman.h>
#include <sys/stat.h>
#include <errno.h>
#include <machine/atomic.h>
#include <sys/umtx.h>
#include <limits.h>
#include <fcntl.h>
#include <pthread.h>
#include <stdarg.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <semaphore.h>
#include <unistd.h>
#include "un-namespace.h"
#include "libc_private.h"
__weak_reference(_sem_close, sem_close);
__weak_reference(_sem_destroy, sem_destroy);
__weak_reference(_sem_getvalue, sem_getvalue);
__weak_reference(_sem_init, sem_init);
__weak_reference(_sem_open, sem_open);
__weak_reference(_sem_post, sem_post);
__weak_reference(_sem_timedwait, sem_timedwait);
__weak_reference(_sem_trywait, sem_trywait);
__weak_reference(_sem_unlink, sem_unlink);
__weak_reference(_sem_wait, sem_wait);
#define SEM_PREFIX "/tmp/SEMD"
#define SEM_MAGIC ((u_int32_t)0x73656d31)
struct sem_nameinfo {
int open_count;
char *name;
sem_t *sem;
LIST_ENTRY(sem_nameinfo) next;
};
static pthread_once_t once = PTHREAD_ONCE_INIT;
static pthread_mutex_t sem_llock;
static LIST_HEAD(,sem_nameinfo) sem_list = LIST_HEAD_INITIALIZER(sem_list);
static void
sem_prefork()
{
_pthread_mutex_lock(&sem_llock);
}
static void
sem_postfork()
{
_pthread_mutex_unlock(&sem_llock);
}
static void
sem_child_postfork()
{
_pthread_mutex_unlock(&sem_llock);
}
static void
sem_module_init(void)
{
pthread_mutexattr_t ma;
_pthread_mutexattr_init(&ma);
_pthread_mutexattr_settype(&ma, PTHREAD_MUTEX_RECURSIVE);
_pthread_mutex_init(&sem_llock, &ma);
_pthread_mutexattr_destroy(&ma);
_pthread_atfork(sem_prefork, sem_postfork, sem_child_postfork);
}
static inline int
sem_check_validity(sem_t *sem)
{
if (sem->_magic == SEM_MAGIC)
return (0);
else {
errno = EINVAL;
return (-1);
}
}
int
_sem_init(sem_t *sem, int pshared, unsigned int value)
{
if (value > SEM_VALUE_MAX) {
errno = EINVAL;
return (-1);
}
bzero(sem, sizeof(sem_t));
sem->_magic = SEM_MAGIC;
sem->_kern._count = (u_int32_t)value;
sem->_kern._has_waiters = 0;
sem->_kern._flags = pshared ? USYNC_PROCESS_SHARED : 0;
return (0);
}
sem_t *
_sem_open(const char *name, int flags, ...)
{
char path[PATH_MAX];
struct stat sb;
va_list ap;
struct sem_nameinfo *ni = NULL;
sem_t *sem = NULL;
int fd = -1, mode, len, errsave;
int value = 0;
if (name[0] != '/') {
errno = EINVAL;
return (SEM_FAILED);
}
name++;
if (flags & ~(O_CREAT|O_EXCL)) {
errno = EINVAL;
return (SEM_FAILED);
}
_pthread_once(&once, sem_module_init);
_pthread_mutex_lock(&sem_llock);
LIST_FOREACH(ni, &sem_list, next) {
if (strcmp(name, ni->name) == 0) {
ni->open_count++;
sem = ni->sem;
_pthread_mutex_unlock(&sem_llock);
return (sem);
}
}
if (flags & O_CREAT) {
va_start(ap, flags);
mode = va_arg(ap, int);
value = va_arg(ap, int);
va_end(ap);
}
len = sizeof(*ni) + strlen(name) + 1;
ni = (struct sem_nameinfo *)malloc(len);
if (ni == NULL) {
errno = ENOSPC;
goto error;
}
ni->name = (char *)(ni+1);
strcpy(ni->name, name);
strcpy(path, SEM_PREFIX);
if (strlcat(path, name, sizeof(path)) >= sizeof(path)) {
errno = ENAMETOOLONG;
goto error;
}
fd = _open(path, flags|O_RDWR, mode);
if (fd == -1)
goto error;
if (flock(fd, LOCK_EX) == -1)
goto error;
if (_fstat(fd, &sb)) {
flock(fd, LOCK_UN);
goto error;
}
if (sb.st_size < sizeof(sem_t)) {
sem_t tmp;
tmp._magic = SEM_MAGIC;
tmp._kern._has_waiters = 0;
tmp._kern._count = value;
tmp._kern._flags = USYNC_PROCESS_SHARED | SEM_NAMED;
if (_write(fd, &tmp, sizeof(tmp)) != sizeof(tmp)) {
flock(fd, LOCK_UN);
goto error;
}
}
flock(fd, LOCK_UN);
sem = (sem_t *)mmap(NULL, sizeof(sem_t), PROT_READ|PROT_WRITE,
MAP_SHARED|MAP_NOSYNC, fd, 0);
if (sem == MAP_FAILED) {
sem = NULL;
if (errno == ENOMEM)
errno = ENOSPC;
goto error;
}
if (sem->_magic != SEM_MAGIC) {
errno = EINVAL;
goto error;
}
ni->open_count = 1;
ni->sem = sem;
LIST_INSERT_HEAD(&sem_list, ni, next);
_pthread_mutex_unlock(&sem_llock);
_close(fd);
return (sem);
error:
errsave = errno;
_pthread_mutex_unlock(&sem_llock);
if (fd != -1)
_close(fd);
if (sem != NULL)
munmap(sem, sizeof(sem_t));
free(ni);
errno = errsave;
return (SEM_FAILED);
}
int
_sem_close(sem_t *sem)
{
struct sem_nameinfo *ni;
if (sem_check_validity(sem) != 0)
return (-1);
if (!(sem->_kern._flags & SEM_NAMED)) {
errno = EINVAL;
return (-1);
}
_pthread_once(&once, sem_module_init);
_pthread_mutex_lock(&sem_llock);
LIST_FOREACH(ni, &sem_list, next) {
if (sem == ni->sem) {
if (--ni->open_count > 0) {
_pthread_mutex_unlock(&sem_llock);
return (0);
}
else
break;
}
}
if (ni) {
LIST_REMOVE(ni, next);
_pthread_mutex_unlock(&sem_llock);
munmap(sem, sizeof(*sem));
free(ni);
return (0);
}
_pthread_mutex_unlock(&sem_llock);
errno = EINVAL;
return (-1);
}
int
_sem_unlink(const char *name)
{
char path[PATH_MAX];
if (name[0] != '/') {
errno = ENOENT;
return -1;
}
name++;
strcpy(path, SEM_PREFIX);
if (strlcat(path, name, sizeof(path)) >= sizeof(path)) {
errno = ENAMETOOLONG;
return (-1);
}
return unlink(path);
}
int
_sem_destroy(sem_t *sem)
{
if (sem_check_validity(sem) != 0)
return (-1);
if (sem->_kern._flags & SEM_NAMED) {
errno = EINVAL;
return (-1);
}
sem->_magic = 0;
return (0);
}
int
_sem_getvalue(sem_t * __restrict sem, int * __restrict sval)
{
if (sem_check_validity(sem) != 0)
return (-1);
*sval = (int)sem->_kern._count;
return (0);
}
static __inline int
usem_wake(struct _usem *sem)
{
rmb();
if (!sem->_has_waiters)
return (0);
return _umtx_op(sem, UMTX_OP_SEM_WAKE, 0, NULL, NULL);
}
static __inline int
usem_wait(struct _usem *sem, const struct timespec *abstime)
{
struct _umtx_time *tm_p, timeout;
size_t tm_size;
if (abstime == NULL) {
tm_p = NULL;
tm_size = 0;
} else {
timeout._clockid = CLOCK_REALTIME;
timeout._flags = UMTX_ABSTIME;
timeout._timeout = *abstime;
tm_p = &timeout;
tm_size = sizeof(timeout);
}
return _umtx_op(sem, UMTX_OP_SEM_WAIT, 0,
(void *)tm_size, __DECONST(void*, tm_p));
}
int
_sem_trywait(sem_t *sem)
{
int val;
if (sem_check_validity(sem) != 0)
return (-1);
while ((val = sem->_kern._count) > 0) {
if (atomic_cmpset_acq_int(&sem->_kern._count, val, val - 1))
return (0);
}
errno = EAGAIN;
return (-1);
}
#define TIMESPEC_SUB(dst, src, val) \
do { \
(dst)->tv_sec = (src)->tv_sec - (val)->tv_sec; \
(dst)->tv_nsec = (src)->tv_nsec - (val)->tv_nsec; \
if ((dst)->tv_nsec < 0) { \
(dst)->tv_sec--; \
(dst)->tv_nsec += 1000000000; \
} \
} while (0)
int
_sem_timedwait(sem_t * __restrict sem,
const struct timespec * __restrict abstime)
{
int val, retval;
if (sem_check_validity(sem) != 0)
return (-1);
retval = 0;
for (;;) {
while ((val = sem->_kern._count) > 0) {
if (atomic_cmpset_acq_int(&sem->_kern._count, val, val - 1))
return (0);
}
if (retval) {
_pthread_testcancel();
break;
}
/*
* The timeout argument is only supposed to
* be checked if the thread would have blocked.
*/
if (abstime != NULL) {
if (abstime->tv_nsec >= 1000000000 || abstime->tv_nsec < 0) {
errno = EINVAL;
return (-1);
}
}
_pthread_cancel_enter(1);
retval = usem_wait(&sem->_kern, abstime);
_pthread_cancel_leave(0);
}
return (retval);
}
int
_sem_wait(sem_t *sem)
{
return _sem_timedwait(sem, NULL);
}
/*
* POSIX:
* The sem_post() interface is reentrant with respect to signals and may be
* invoked from a signal-catching function.
* The implementation does not use lock, so it should be safe.
*/
int
_sem_post(sem_t *sem)
{
if (sem_check_validity(sem) != 0)
return (-1);
atomic_add_rel_int(&sem->_kern._count, 1);
return usem_wake(&sem->_kern);
}