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/*
* Copyright (c) 1999 Richard Seaman, Jr.
* 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, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by Richard Seaman, Jr.
* 4. Neither the name of the author nor the names of any co-contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY RICHARD SEAMAN, Jr. AND CONTRIBUTORS ``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 REGENTS OR CONTRIBUTORS 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.
*
*/
#ifndef _THREAD_SAFE
#define _THREAD_SAFE
#endif
#include <dlfcn.h>
#include <errno.h>
#include <stdlib.h>
#include "pthread.h"
#include "internals.h"
typedef struct {
volatile long lock;
volatile int nreaders; /* -1 when a write lock is held. */
} rwlock_t;
#define _RWLOCK_PROTECT(l) _spinlock(&((l)->lock))
#define _RWLOCK_UNPROTECT(l) (l)->lock = 0
/*
* This is defined in lib/libc/stdlib/exit.c. It turns on thread safe behavior
* in libc if non-zero.
*/
extern int __isthreaded;
/*
* Optional. In case our code is dependant on the existence of
* the posix priority extentions kernel option.
*/
#include <sys/sysctl.h>
int _posix_priority_scheduling;
#if defined(NEWLIBC)
/*
* The following are needed if we're going to get thread safe behavior in the
* time functions in lib/libc/stdtime/localtime.c.
*/
static pthread_mutex_t _lcl_mutex = PTHREAD_MUTEX_INITIALIZER;
static pthread_mutex_t _gmt_mutex = PTHREAD_MUTEX_INITIALIZER;
static pthread_mutex_t _localtime_mutex = PTHREAD_MUTEX_INITIALIZER;
static pthread_mutex_t _gmtime_mutex = PTHREAD_MUTEX_INITIALIZER;
extern pthread_mutex_t *lcl_mutex;
extern pthread_mutex_t *gmt_mutex;
extern pthread_mutex_t *localtime_mutex;
extern pthread_mutex_t *gmtime_mutex;
#endif
/* Use the constructor attribute so this gets run before main does. */
static void _pthread_initialize(void) __attribute__((constructor));
/* Defined in _atomic_lock.S. */
long _atomic_lock(volatile long *);
void _spinlock(volatile long *lock);
void *lock_create (void *context);
void rlock_acquire (void *lock);
void wlock_acquire (void *lock);
void lock_release (void *lock);
void lock_destroy (void *lock);
static void _pthread_initialize(void)
{
int mib[2];
size_t len;
len = sizeof (_posix_priority_scheduling);
mib[0] = CTL_P1003_1B;
mib[1] = CTL_P1003_1B_PRIORITY_SCHEDULING;
if (-1 == sysctl (mib, 2, &_posix_priority_scheduling, &len, NULL, 0))
_posix_priority_scheduling = 0;
/* This turns on thread safe behaviour in libc when we link with it. */
__isthreaded = 1;
dllockinit (NULL,
lock_create,
rlock_acquire,
wlock_acquire,
lock_release,
lock_destroy,
NULL);
#if defined(NEWLIBC)
/* Set up pointers for lib/libc/stdtime/localtime.c. */
lcl_mutex = &_lcl_mutex;
gmt_mutex = &_gmt_mutex;
localtime_mutex = &_localtime_mutex;
gmtime_mutex = &_gmtime_mutex;
#endif
}
void
_spinlock(volatile long *lock)
{
while(_atomic_lock(lock)) {
/* Spin. */
}
}
/*
* Simple nested spinning reader/writer lock implementation. We can't use the
* normal library implementation for bootstrapping reasons. This implementation
* allows one writer or any number of concurrent readers. No lock grant
* ordering guarantees are made.
*/
void *
lock_create (void *context)
{
rwlock_t *retval;
retval = (rwlock_t *)malloc(sizeof(rwlock_t));
if (retval == NULL)
goto RETURN;
bzero(retval, sizeof(rwlock_t));
RETURN:
return ((void *)retval);
}
void
rlock_acquire (void *lock)
{
rwlock_t *rwlock = lock;
_RWLOCK_PROTECT(rwlock);
while (rwlock->nreaders < 0) {
_RWLOCK_UNPROTECT(rwlock);
_RWLOCK_PROTECT(rwlock);
}
rwlock->nreaders++;
_RWLOCK_UNPROTECT(rwlock);
}
void
wlock_acquire (void *lock)
{
rwlock_t *rwlock = lock;
_RWLOCK_PROTECT(rwlock);
while (rwlock->nreaders != 0) {
_RWLOCK_UNPROTECT(rwlock);
_RWLOCK_PROTECT(rwlock);
}
rwlock->nreaders--;
_RWLOCK_UNPROTECT(rwlock);
}
void
lock_release (void *lock)
{
rwlock_t *rwlock = lock;
_RWLOCK_PROTECT(rwlock);
if (rwlock->nreaders < 0)
rwlock->nreaders++;
else
rwlock->nreaders--;
_RWLOCK_UNPROTECT(rwlock);
}
void
lock_destroy (void *lock)
{
free(lock);
}
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