freebsd-skq/lib/libkse/thread/thr_rwlock.c
deischen cc69a08fbf Add compatibility symbol maps. libpthread (.so.1 and .so.2)
used LIBTHREAD_1_0 as its version definition, but now needs
to define its symbols in the same namespace used by libc.
The compatibility hooks allows you to use libraries and
binaries built and linked to libpthread before libc was
built with symbol versioning.  The shims can be removed if
libpthread is given a version bump.

Reviewed by:	davidxu
2006-03-13 00:59:51 +00:00

439 lines
11 KiB
C

/*-
* Copyright (c) 1998 Alex Nash
* 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.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
*
* $FreeBSD$
*/
#include <errno.h>
#include <limits.h>
#include <stdlib.h>
#include "namespace.h"
#include <pthread.h>
#include "un-namespace.h"
#include "thr_private.h"
/* maximum number of times a read lock may be obtained */
#define MAX_READ_LOCKS (INT_MAX - 1)
LT10_COMPAT_PRIVATE(_pthread_rwlock_destroy);
LT10_COMPAT_DEFAULT(pthread_rwlock_destroy);
LT10_COMPAT_PRIVATE(_pthread_rwlock_init);
LT10_COMPAT_DEFAULT(pthread_rwlock_init);
LT10_COMPAT_PRIVATE(_pthread_rwlock_rdlock);
LT10_COMPAT_DEFAULT(pthread_rwlock_rdlock);
LT10_COMPAT_PRIVATE(_pthread_rwlock_timedrdlock);
LT10_COMPAT_DEFAULT(pthread_rwlock_timedrdlock);
LT10_COMPAT_PRIVATE(_pthread_rwlock_tryrdlock);
LT10_COMPAT_DEFAULT(pthread_rwlock_tryrdlock);
LT10_COMPAT_PRIVATE(_pthread_rwlock_trywrlock);
LT10_COMPAT_DEFAULT(pthread_rwlock_trywrlock);
LT10_COMPAT_PRIVATE(_pthread_rwlock_unlock);
LT10_COMPAT_DEFAULT(pthread_rwlock_unlock);
LT10_COMPAT_PRIVATE(_pthread_rwlock_wrlock);
LT10_COMPAT_DEFAULT(pthread_rwlock_wrlock);
LT10_COMPAT_PRIVATE(_pthread_rwlock_timedwrlock);
LT10_COMPAT_DEFAULT(pthread_rwlock_timedwrlock);
__weak_reference(_pthread_rwlock_destroy, pthread_rwlock_destroy);
__weak_reference(_pthread_rwlock_init, pthread_rwlock_init);
__weak_reference(_pthread_rwlock_rdlock, pthread_rwlock_rdlock);
__weak_reference(_pthread_rwlock_timedrdlock, pthread_rwlock_timedrdlock);
__weak_reference(_pthread_rwlock_tryrdlock, pthread_rwlock_tryrdlock);
__weak_reference(_pthread_rwlock_trywrlock, pthread_rwlock_trywrlock);
__weak_reference(_pthread_rwlock_unlock, pthread_rwlock_unlock);
__weak_reference(_pthread_rwlock_wrlock, pthread_rwlock_wrlock);
__weak_reference(_pthread_rwlock_timedwrlock, pthread_rwlock_timedwrlock);
/*
* Prototypes
*/
static int init_static(pthread_rwlock_t *rwlock);
static int
init_static(pthread_rwlock_t *rwlock)
{
struct pthread *thread = _get_curthread();
int ret;
THR_LOCK_ACQUIRE(thread, &_rwlock_static_lock);
if (*rwlock == NULL)
ret = _pthread_rwlock_init(rwlock, NULL);
else
ret = 0;
THR_LOCK_RELEASE(thread, &_rwlock_static_lock);
return (ret);
}
int
_pthread_rwlock_destroy (pthread_rwlock_t *rwlock)
{
int ret;
if (rwlock == NULL)
ret = EINVAL;
else {
pthread_rwlock_t prwlock;
prwlock = *rwlock;
_pthread_mutex_destroy(&prwlock->lock);
_pthread_cond_destroy(&prwlock->read_signal);
_pthread_cond_destroy(&prwlock->write_signal);
free(prwlock);
*rwlock = NULL;
ret = 0;
}
return (ret);
}
int
_pthread_rwlock_init (pthread_rwlock_t *rwlock, const pthread_rwlockattr_t *attr)
{
pthread_rwlock_t prwlock;
int ret;
/* allocate rwlock object */
prwlock = (pthread_rwlock_t)malloc(sizeof(struct pthread_rwlock));
if (prwlock == NULL)
return (ENOMEM);
/* initialize the lock */
if ((ret = _pthread_mutex_init(&prwlock->lock, NULL)) != 0)
free(prwlock);
else {
/* initialize the read condition signal */
ret = _pthread_cond_init(&prwlock->read_signal, NULL);
if (ret != 0) {
_pthread_mutex_destroy(&prwlock->lock);
free(prwlock);
} else {
/* initialize the write condition signal */
ret = _pthread_cond_init(&prwlock->write_signal, NULL);
if (ret != 0) {
_pthread_cond_destroy(&prwlock->read_signal);
_pthread_mutex_destroy(&prwlock->lock);
free(prwlock);
} else {
/* success */
prwlock->state = 0;
prwlock->blocked_writers = 0;
*rwlock = prwlock;
}
}
}
return (ret);
}
static int
rwlock_rdlock_common (pthread_rwlock_t *rwlock, const struct timespec *abstime)
{
pthread_rwlock_t prwlock;
struct pthread *curthread;
int ret;
if (rwlock == NULL)
return (EINVAL);
prwlock = *rwlock;
/* check for static initialization */
if (prwlock == NULL) {
if ((ret = init_static(rwlock)) != 0)
return (ret);
prwlock = *rwlock;
}
/* grab the monitor lock */
if ((ret = _thr_mutex_lock(&prwlock->lock)) != 0)
return (ret);
/* check lock count */
if (prwlock->state == MAX_READ_LOCKS) {
_thr_mutex_unlock(&prwlock->lock);
return (EAGAIN);
}
curthread = _get_curthread();
if ((curthread->rdlock_count > 0) && (prwlock->state > 0)) {
/*
* To avoid having to track all the rdlocks held by
* a thread or all of the threads that hold a rdlock,
* we keep a simple count of all the rdlocks held by
* a thread. If a thread holds any rdlocks it is
* possible that it is attempting to take a recursive
* rdlock. If there are blocked writers and precedence
* is given to them, then that would result in the thread
* deadlocking. So allowing a thread to take the rdlock
* when it already has one or more rdlocks avoids the
* deadlock. I hope the reader can follow that logic ;-)
*/
; /* nothing needed */
} else {
/* give writers priority over readers */
while (prwlock->blocked_writers || prwlock->state < 0) {
if (abstime)
ret = _pthread_cond_timedwait
(&prwlock->read_signal,
&prwlock->lock, abstime);
else
ret = _thr_cond_wait(&prwlock->read_signal,
&prwlock->lock);
if (ret != 0) {
/* can't do a whole lot if this fails */
_thr_mutex_unlock(&prwlock->lock);
return (ret);
}
}
}
curthread->rdlock_count++;
prwlock->state++; /* indicate we are locked for reading */
/*
* Something is really wrong if this call fails. Returning
* error won't do because we've already obtained the read
* lock. Decrementing 'state' is no good because we probably
* don't have the monitor lock.
*/
_thr_mutex_unlock(&prwlock->lock);
return (ret);
}
int
_pthread_rwlock_rdlock (pthread_rwlock_t *rwlock)
{
return (rwlock_rdlock_common(rwlock, NULL));
}
__strong_reference(_pthread_rwlock_rdlock, _thr_rwlock_rdlock);
int
_pthread_rwlock_timedrdlock (pthread_rwlock_t *rwlock,
const struct timespec *abstime)
{
return (rwlock_rdlock_common(rwlock, abstime));
}
int
_pthread_rwlock_tryrdlock (pthread_rwlock_t *rwlock)
{
struct pthread *curthread;
pthread_rwlock_t prwlock;
int ret;
if (rwlock == NULL)
return (EINVAL);
prwlock = *rwlock;
/* check for static initialization */
if (prwlock == NULL) {
if ((ret = init_static(rwlock)) != 0)
return (ret);
prwlock = *rwlock;
}
/* grab the monitor lock */
if ((ret = _pthread_mutex_lock(&prwlock->lock)) != 0)
return (ret);
curthread = _get_curthread();
if (prwlock->state == MAX_READ_LOCKS)
ret = EAGAIN;
else if ((curthread->rdlock_count > 0) && (prwlock->state > 0)) {
/* see comment for pthread_rwlock_rdlock() */
curthread->rdlock_count++;
prwlock->state++;
}
/* give writers priority over readers */
else if (prwlock->blocked_writers || prwlock->state < 0)
ret = EBUSY;
else {
curthread->rdlock_count++;
prwlock->state++; /* indicate we are locked for reading */
}
/* see the comment on this in pthread_rwlock_rdlock */
_pthread_mutex_unlock(&prwlock->lock);
return (ret);
}
int
_pthread_rwlock_trywrlock (pthread_rwlock_t *rwlock)
{
pthread_rwlock_t prwlock;
int ret;
if (rwlock == NULL)
return (EINVAL);
prwlock = *rwlock;
/* check for static initialization */
if (prwlock == NULL) {
if ((ret = init_static(rwlock)) != 0)
return (ret);
prwlock = *rwlock;
}
/* grab the monitor lock */
if ((ret = _pthread_mutex_lock(&prwlock->lock)) != 0)
return (ret);
if (prwlock->state != 0)
ret = EBUSY;
else
/* indicate we are locked for writing */
prwlock->state = -1;
/* see the comment on this in pthread_rwlock_rdlock */
_pthread_mutex_unlock(&prwlock->lock);
return (ret);
}
int
_pthread_rwlock_unlock (pthread_rwlock_t *rwlock)
{
struct pthread *curthread;
pthread_rwlock_t prwlock;
int ret;
if (rwlock == NULL)
return (EINVAL);
prwlock = *rwlock;
if (prwlock == NULL)
return (EINVAL);
/* grab the monitor lock */
if ((ret = _thr_mutex_lock(&prwlock->lock)) != 0)
return (ret);
curthread = _get_curthread();
if (prwlock->state > 0) {
curthread->rdlock_count--;
prwlock->state--;
if (prwlock->state == 0 && prwlock->blocked_writers)
ret = _thr_cond_signal(&prwlock->write_signal);
} else if (prwlock->state < 0) {
prwlock->state = 0;
if (prwlock->blocked_writers)
ret = _thr_cond_signal(&prwlock->write_signal);
else
ret = _thr_cond_broadcast(&prwlock->read_signal);
} else
ret = EINVAL;
/* see the comment on this in pthread_rwlock_rdlock */
_thr_mutex_unlock(&prwlock->lock);
return (ret);
}
__strong_reference(_pthread_rwlock_unlock, _thr_rwlock_unlock);
static int
rwlock_wrlock_common (pthread_rwlock_t *rwlock, const struct timespec *abstime)
{
pthread_rwlock_t prwlock;
int ret;
if (rwlock == NULL)
return (EINVAL);
prwlock = *rwlock;
/* check for static initialization */
if (prwlock == NULL) {
if ((ret = init_static(rwlock)) != 0)
return (ret);
prwlock = *rwlock;
}
/* grab the monitor lock */
if ((ret = _thr_mutex_lock(&prwlock->lock)) != 0)
return (ret);
while (prwlock->state != 0) {
prwlock->blocked_writers++;
if (abstime != NULL)
ret = _pthread_cond_timedwait(&prwlock->write_signal,
&prwlock->lock, abstime);
else
ret = _thr_cond_wait(&prwlock->write_signal,
&prwlock->lock);
if (ret != 0) {
prwlock->blocked_writers--;
_thr_mutex_unlock(&prwlock->lock);
return (ret);
}
prwlock->blocked_writers--;
}
/* indicate we are locked for writing */
prwlock->state = -1;
/* see the comment on this in pthread_rwlock_rdlock */
_thr_mutex_unlock(&prwlock->lock);
return (ret);
}
int
_pthread_rwlock_wrlock (pthread_rwlock_t *rwlock)
{
return (rwlock_wrlock_common (rwlock, NULL));
}
__strong_reference(_pthread_rwlock_wrlock, _thr_rwlock_wrlock);
int
_pthread_rwlock_timedwrlock (pthread_rwlock_t *rwlock,
const struct timespec *abstime)
{
return (rwlock_wrlock_common (rwlock, abstime));
}