/* 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. */
/* Mutexes */
#include <stddef.h>
#include "pthread.h"
#include "internals.h"
#include "spinlock.h"
#include "queue.h"
#include "restart.h"
int pthread_mutex_init(pthread_mutex_t * mutex,
const pthread_mutexattr_t * mutex_attr)
{
mutex->m_spinlock = 0;
mutex->m_count = 0;
mutex->m_owner = NULL;
mutex->m_kind =
mutex_attr == NULL ? PTHREAD_MUTEX_FAST_NP : mutex_attr->mutexkind;
queue_init(&mutex->m_waiting);
return 0;
}
int pthread_mutex_destroy(pthread_mutex_t * mutex)
{
int count;
acquire(&mutex->m_spinlock);
count = mutex->m_count;
release(&mutex->m_spinlock);
if (count > 0) return EBUSY;
return 0;
}
int pthread_mutex_trylock(pthread_mutex_t * mutex)
{
pthread_descr self;
acquire(&mutex->m_spinlock);
switch(mutex->m_kind) {
case PTHREAD_MUTEX_FAST_NP:
if (mutex->m_count == 0) {
mutex->m_count = 1;
release(&mutex->m_spinlock);
return 0;
}
break;
case PTHREAD_MUTEX_RECURSIVE_NP:
self = thread_self();
if (mutex->m_count == 0 || mutex->m_owner == self) {
mutex->m_count++;
mutex->m_owner = self;
release(&mutex->m_spinlock);
return 0;
}
break;
case PTHREAD_MUTEX_ERRORCHECK_NP:
self = thread_self();
if (mutex->m_count == 0) {
mutex->m_count = 1;
mutex->m_owner = self;
release(&mutex->m_spinlock);
return 0;
}
break;
default:
release(&mutex->m_spinlock);
return EINVAL;
}
release(&mutex->m_spinlock);
return EBUSY;
}
int pthread_mutex_lock(pthread_mutex_t * mutex)
{
pthread_descr self;
while(1) {
acquire(&mutex->m_spinlock);
switch(mutex->m_kind) {
case PTHREAD_MUTEX_FAST_NP:
if (mutex->m_count == 0) {
mutex->m_count = 1;
release(&mutex->m_spinlock);
return 0;
}
self = thread_self();
break;
case PTHREAD_MUTEX_RECURSIVE_NP:
self = thread_self();
if (mutex->m_count == 0 || mutex->m_owner == self) {
mutex->m_count++;
mutex->m_owner = self;
release(&mutex->m_spinlock);
return 0;
}
break;
case PTHREAD_MUTEX_ERRORCHECK_NP:
self = thread_self();
if (mutex->m_count == 0) {
mutex->m_count = 1;
mutex->m_owner = self;
release(&mutex->m_spinlock);
return 0;
} else if (mutex->m_owner == self) {
release(&mutex->m_spinlock);
return EDEADLK;
}
break;
default:
release(&mutex->m_spinlock);
return EINVAL;
}
/* Suspend ourselves, then try again */
enqueue(&mutex->m_waiting, self);
release(&mutex->m_spinlock);
suspend(self); /* This is not a cancellation point */
}
}
int pthread_mutex_unlock(pthread_mutex_t * mutex)
{
pthread_descr th;
acquire(&mutex->m_spinlock);
switch (mutex->m_kind) {
case PTHREAD_MUTEX_FAST_NP:
mutex->m_count = 0;
break;
case PTHREAD_MUTEX_RECURSIVE_NP:
mutex->m_count--;
if (mutex->m_count > 0) {
release(&mutex->m_spinlock);
return 0;
}
mutex->m_count = 0; /* so that excess unlocks do not break everything */
break;
case PTHREAD_MUTEX_ERRORCHECK_NP:
if (mutex->m_count == 0 || mutex->m_owner != thread_self()) {
release(&mutex->m_spinlock);
return EPERM;
}
mutex->m_count = 0;
break;
default:
release(&mutex->m_spinlock);
return EINVAL;
}
th = dequeue(&mutex->m_waiting);
release(&mutex->m_spinlock);
if (th != NULL) restart(th);
return 0;
}
int pthread_mutexattr_init(pthread_mutexattr_t *attr)
{
attr->mutexkind = PTHREAD_MUTEX_FAST_NP;
return 0;
}
int pthread_mutexattr_destroy(pthread_mutexattr_t *attr)
{
return 0;
}
int __pthread_mutexattr_setkind_np(pthread_mutexattr_t *attr, int kind)
{
if (kind != PTHREAD_MUTEX_FAST_NP
&& kind != PTHREAD_MUTEX_RECURSIVE_NP
&& kind != PTHREAD_MUTEX_ERRORCHECK_NP)
return EINVAL;
attr->mutexkind = kind;
return 0;
}
weak_alias(__pthread_mutexattr_setkind_np, pthread_mutexattr_setkind_np);
int __pthread_mutexattr_getkind_np(const pthread_mutexattr_t *attr, int *kind)
{
*kind = attr->mutexkind;
return 0;
}
weak_alias(__pthread_mutexattr_getkind_np, pthread_mutexattr_getkind_np);
/* Once-only execution */
static pthread_mutex_t once_masterlock = PTHREAD_MUTEX_INITIALIZER;
static pthread_cond_t once_finished = PTHREAD_COND_INITIALIZER;
enum { NEVER = 0, IN_PROGRESS = 1, DONE = 2 };
int pthread_once(pthread_once_t * once_control, void (*init_routine)(void))
{
/* Test without locking first for speed */
if (*once_control == DONE) return 0;
/* Lock and test again */
pthread_mutex_lock(&once_masterlock);
/* If init_routine is being called from another routine, wait until
it completes. */
while (*once_control == IN_PROGRESS) {
pthread_cond_wait(&once_finished, &once_masterlock);
}
/* Here *once_control is stable and either NEVER or DONE. */
if (*once_control == NEVER) {
*once_control = IN_PROGRESS;
pthread_mutex_unlock(&once_masterlock);
init_routine();
pthread_mutex_lock(&once_masterlock);
*once_control = DONE;
pthread_cond_broadcast(&once_finished);
}
pthread_mutex_unlock(&once_masterlock);
return 0;
}
/* Internal locks for libc 5.2.18 */
static pthread_mutex_t libc_libio_lock = PTHREAD_MUTEX_INITIALIZER;
static pthread_mutex_t libc_localtime_lock = PTHREAD_MUTEX_INITIALIZER;
static pthread_mutex_t libc_gmtime_lock = PTHREAD_MUTEX_INITIALIZER;
/* The variables below are defined as weak symbols in libc,
initialized to NULL pointers, and with dummy pthread_mutex_*
functions (weak symbols also) that do nothing. If we provide
our implementations of pthread_mutex_*, we must also provide
initialized pointers to mutexes for those variables. */
pthread_mutex_t * __libc_libio_lock = &libc_libio_lock;
pthread_mutex_t * __libc_localtime_lock = &libc_localtime_lock;
pthread_mutex_t * __libc_gmtime_lock = &libc_gmtime_lock;
Autor: Karol Goł±b