246 lines
7.3 KiB
C
246 lines
7.3 KiB
C
/*
|
|
* This file contains the old semaphore code that we need to
|
|
* preserve for glibc-2.0 backwards compatibility. Port to glibc 2.1
|
|
* done by Cristian Gafton.
|
|
*/
|
|
|
|
/* Linuxthreads - a simple clone()-based implementation of Posix */
|
|
/* threads for Linux. */
|
|
/* Copyright (C) 1996 Xavier Leroy (Xavier.Leroy@inria.fr) */
|
|
/* */
|
|
/* This program is free software; you can redistribute it and/or */
|
|
/* modify it under the terms of the GNU Library General Public License */
|
|
/* as published by the Free Software Foundation; either version 2 */
|
|
/* of the License, or (at your option) any later version. */
|
|
/* */
|
|
/* This program is distributed in the hope that it will be useful, */
|
|
/* but WITHOUT ANY WARRANTY; without even the implied warranty of */
|
|
/* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the */
|
|
/* GNU Library General Public License for more details. */
|
|
|
|
/* Semaphores a la POSIX 1003.1b */
|
|
#include <shlib-compat.h>
|
|
#if SHLIB_COMPAT(libpthread, GLIBC_2_0, GLIBC_2_1)
|
|
|
|
#include <errno.h>
|
|
#include "pthread.h"
|
|
#include "internals.h"
|
|
#include "spinlock.h"
|
|
#include "restart.h"
|
|
#include "queue.h"
|
|
|
|
typedef struct {
|
|
long int sem_status;
|
|
int sem_spinlock;
|
|
} old_sem_t;
|
|
|
|
extern int __old_sem_init (old_sem_t *__sem, int __pshared, unsigned int __value);
|
|
extern int __old_sem_wait (old_sem_t *__sem);
|
|
extern int __old_sem_trywait (old_sem_t *__sem);
|
|
extern int __old_sem_post (old_sem_t *__sem);
|
|
extern int __old_sem_getvalue (old_sem_t *__sem, int *__sval);
|
|
extern int __old_sem_destroy (old_sem_t *__sem);
|
|
|
|
|
|
/* Maximum value the semaphore can have. */
|
|
#define SEM_VALUE_MAX ((int) ((~0u) >> 1))
|
|
|
|
static inline int sem_compare_and_swap(old_sem_t *sem, long oldval, long newval)
|
|
{
|
|
return compare_and_swap(&sem->sem_status, oldval, newval, &sem->sem_spinlock);
|
|
}
|
|
|
|
/* The state of a semaphore is represented by a long int encoding
|
|
either the semaphore count if >= 0 and no thread is waiting on it,
|
|
or the head of the list of threads waiting for the semaphore.
|
|
To distinguish the two cases, we encode the semaphore count N
|
|
as 2N+1, so that it has the lowest bit set.
|
|
|
|
A sequence of sem_wait operations on a semaphore initialized to N
|
|
result in the following successive states:
|
|
2N+1, 2N-1, ..., 3, 1, &first_waiting_thread, &second_waiting_thread, ...
|
|
*/
|
|
|
|
static void sem_restart_list(pthread_descr waiting);
|
|
|
|
int __old_sem_init(old_sem_t *sem, int pshared, unsigned int value)
|
|
{
|
|
if (value > SEM_VALUE_MAX) {
|
|
errno = EINVAL;
|
|
return -1;
|
|
}
|
|
if (pshared) {
|
|
errno = ENOSYS;
|
|
return -1;
|
|
}
|
|
sem->sem_spinlock = __LT_SPINLOCK_INIT;
|
|
sem->sem_status = ((long)value << 1) + 1;
|
|
return 0;
|
|
}
|
|
|
|
/* Function called by pthread_cancel to remove the thread from
|
|
waiting inside __old_sem_wait. Here we simply unconditionally
|
|
indicate that the thread is to be woken, by returning 1. */
|
|
|
|
static int old_sem_extricate_func(void *obj, pthread_descr th)
|
|
{
|
|
return 1;
|
|
}
|
|
|
|
int __old_sem_wait(old_sem_t * sem)
|
|
{
|
|
long oldstatus, newstatus;
|
|
volatile pthread_descr self = thread_self();
|
|
pthread_descr * th;
|
|
pthread_extricate_if extr;
|
|
|
|
/* Set up extrication interface */
|
|
extr.pu_object = 0;
|
|
extr.pu_extricate_func = old_sem_extricate_func;
|
|
|
|
while (1) {
|
|
/* Register extrication interface */
|
|
__pthread_set_own_extricate_if(self, &extr);
|
|
do {
|
|
oldstatus = sem->sem_status;
|
|
if ((oldstatus & 1) && (oldstatus != 1))
|
|
newstatus = oldstatus - 2;
|
|
else {
|
|
newstatus = (long) self;
|
|
self->p_nextwaiting = (pthread_descr) oldstatus;
|
|
}
|
|
}
|
|
while (! sem_compare_and_swap(sem, oldstatus, newstatus));
|
|
if (newstatus & 1) {
|
|
/* We got the semaphore. */
|
|
__pthread_set_own_extricate_if(self, 0);
|
|
self->p_nextwaiting = NULL;
|
|
return 0;
|
|
}
|
|
/* Wait for sem_post or cancellation */
|
|
suspend(self);
|
|
__pthread_set_own_extricate_if(self, 0);
|
|
|
|
/* This is a cancellation point */
|
|
if (self->p_canceled && self->p_cancelstate == PTHREAD_CANCEL_ENABLE) {
|
|
/* Remove ourselves from the waiting list if we're still on it */
|
|
/* First check if we're at the head of the list. */
|
|
do {
|
|
oldstatus = sem->sem_status;
|
|
if (oldstatus != (long) self) break;
|
|
newstatus = (long) self->p_nextwaiting;
|
|
}
|
|
while (! sem_compare_and_swap(sem, oldstatus, newstatus));
|
|
/* Now, check if we're somewhere in the list.
|
|
There's a race condition with sem_post here, but it does not matter:
|
|
the net result is that at the time pthread_exit is called,
|
|
self is no longer reachable from sem->sem_status. */
|
|
if (oldstatus != (long) self && (oldstatus & 1) == 0) {
|
|
for (th = &(((pthread_descr) oldstatus)->p_nextwaiting);
|
|
*th != NULL && *th != (pthread_descr) 1;
|
|
th = &((*th)->p_nextwaiting)) {
|
|
if (*th == self) {
|
|
*th = self->p_nextwaiting;
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
__pthread_do_exit(PTHREAD_CANCELED, CURRENT_STACK_FRAME);
|
|
}
|
|
}
|
|
}
|
|
|
|
int __old_sem_trywait(old_sem_t * sem)
|
|
{
|
|
long oldstatus, newstatus;
|
|
|
|
do {
|
|
oldstatus = sem->sem_status;
|
|
if ((oldstatus & 1) == 0 || (oldstatus == 1)) {
|
|
errno = EAGAIN;
|
|
return -1;
|
|
}
|
|
newstatus = oldstatus - 2;
|
|
}
|
|
while (! sem_compare_and_swap(sem, oldstatus, newstatus));
|
|
return 0;
|
|
}
|
|
|
|
int __old_sem_post(old_sem_t * sem)
|
|
{
|
|
long oldstatus, newstatus;
|
|
|
|
do {
|
|
oldstatus = sem->sem_status;
|
|
if ((oldstatus & 1) == 0)
|
|
newstatus = 3;
|
|
else {
|
|
if (oldstatus >= SEM_VALUE_MAX) {
|
|
/* Overflow */
|
|
errno = ERANGE;
|
|
return -1;
|
|
}
|
|
newstatus = oldstatus + 2;
|
|
}
|
|
}
|
|
while (! sem_compare_and_swap(sem, oldstatus, newstatus));
|
|
if ((oldstatus & 1) == 0)
|
|
sem_restart_list((pthread_descr) oldstatus);
|
|
return 0;
|
|
}
|
|
|
|
int __old_sem_getvalue(old_sem_t * sem, int * sval)
|
|
{
|
|
long status = sem->sem_status;
|
|
if (status & 1)
|
|
*sval = (int)((unsigned long) status >> 1);
|
|
else
|
|
*sval = 0;
|
|
return 0;
|
|
}
|
|
|
|
int __old_sem_destroy(old_sem_t * sem)
|
|
{
|
|
if ((sem->sem_status & 1) == 0) {
|
|
errno = EBUSY;
|
|
return -1;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
/* Auxiliary function for restarting all threads on a waiting list,
|
|
in priority order. */
|
|
|
|
static void sem_restart_list(pthread_descr waiting)
|
|
{
|
|
pthread_descr th, towake, *p;
|
|
|
|
/* Sort list of waiting threads by decreasing priority (insertion sort) */
|
|
towake = NULL;
|
|
while (waiting != (pthread_descr) 1) {
|
|
th = waiting;
|
|
waiting = waiting->p_nextwaiting;
|
|
p = &towake;
|
|
while (*p != NULL && th->p_priority < (*p)->p_priority)
|
|
p = &((*p)->p_nextwaiting);
|
|
th->p_nextwaiting = *p;
|
|
*p = th;
|
|
}
|
|
/* Wake up threads in priority order */
|
|
while (towake != NULL) {
|
|
th = towake;
|
|
towake = towake->p_nextwaiting;
|
|
th->p_nextwaiting = NULL;
|
|
restart(th);
|
|
}
|
|
}
|
|
|
|
compat_symbol (libpthread, __old_sem_init, sem_init, GLIBC_2_0);
|
|
compat_symbol (libpthread, __old_sem_wait, sem_wait, GLIBC_2_0);
|
|
compat_symbol (libpthread, __old_sem_trywait, sem_trywait, GLIBC_2_0);
|
|
compat_symbol (libpthread, __old_sem_post, sem_post, GLIBC_2_0);
|
|
compat_symbol (libpthread, __old_sem_getvalue, sem_getvalue, GLIBC_2_0);
|
|
compat_symbol (libpthread, __old_sem_destroy, sem_destroy, GLIBC_2_0);
|
|
|
|
#endif
|