NetBSD/lib/libpthread/pthread_rwlock.c

506 lines
14 KiB
C

/* $NetBSD: pthread_rwlock.c,v 1.13 2005/10/19 02:15:03 chs Exp $ */
/*-
* Copyright (c) 2002 The NetBSD Foundation, Inc.
* All rights reserved.
*
* This code is derived from software contributed to The NetBSD Foundation
* by Nathan J. Williams.
*
* 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 the NetBSD
* Foundation, Inc. and its contributors.
* 4. Neither the name of The NetBSD Foundation nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. 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 FOUNDATION 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.
*/
#include <sys/cdefs.h>
__RCSID("$NetBSD: pthread_rwlock.c,v 1.13 2005/10/19 02:15:03 chs Exp $");
#include <errno.h>
#include "pthread.h"
#include "pthread_int.h"
static void pthread_rwlock__callback(void *);
__strong_alias(__libc_rwlock_init,pthread_rwlock_init)
__strong_alias(__libc_rwlock_rdlock,pthread_rwlock_rdlock)
__strong_alias(__libc_rwlock_wrlock,pthread_rwlock_wrlock)
__strong_alias(__libc_rwlock_tryrdlock,pthread_rwlock_tryrdlock)
__strong_alias(__libc_rwlock_trywrlock,pthread_rwlock_trywrlock)
__strong_alias(__libc_rwlock_unlock,pthread_rwlock_unlock)
__strong_alias(__libc_rwlock_destroy,pthread_rwlock_destroy)
int
pthread_rwlock_init(pthread_rwlock_t *rwlock,
const pthread_rwlockattr_t *attr)
{
#ifdef ERRORCHECK
if ((rwlock == NULL) ||
(attr && (attr->ptra_magic != _PT_RWLOCKATTR_MAGIC)))
return EINVAL;
#endif
rwlock->ptr_magic = _PT_RWLOCK_MAGIC;
pthread_lockinit(&rwlock->ptr_interlock);
PTQ_INIT(&rwlock->ptr_rblocked);
PTQ_INIT(&rwlock->ptr_wblocked);
rwlock->ptr_nreaders = 0;
rwlock->ptr_writer = NULL;
return 0;
}
int
pthread_rwlock_destroy(pthread_rwlock_t *rwlock)
{
#ifdef ERRORCHECK
if ((rwlock == NULL) ||
(rwlock->ptr_magic != _PT_RWLOCK_MAGIC) ||
(!PTQ_EMPTY(&rwlock->ptr_rblocked)) ||
(!PTQ_EMPTY(&rwlock->ptr_wblocked)) ||
(rwlock->ptr_nreaders != 0) ||
(rwlock->ptr_writer != NULL))
return EINVAL;
#endif
rwlock->ptr_magic = _PT_RWLOCK_DEAD;
return 0;
}
int
pthread_rwlock_rdlock(pthread_rwlock_t *rwlock)
{
pthread_t self;
#ifdef ERRORCHECK
if ((rwlock == NULL) || (rwlock->ptr_magic != _PT_RWLOCK_MAGIC))
return EINVAL;
#endif
self = pthread__self();
pthread_spinlock(self, &rwlock->ptr_interlock);
#ifdef ERRORCHECK
if (rwlock->ptr_writer == self) {
pthread_spinunlock(self, &rwlock->ptr_interlock);
return EDEADLK;
}
#endif
/*
* Don't get a readlock if there is a writer or if there are waiting
* writers; i.e. prefer writers to readers. This strategy is dictated
* by SUSv3.
*/
while ((rwlock->ptr_writer != NULL) ||
(!PTQ_EMPTY(&rwlock->ptr_wblocked))) {
PTQ_INSERT_TAIL(&rwlock->ptr_rblocked, self, pt_sleep);
/* Locking a rwlock is not a cancellation point; don't check */
pthread_spinlock(self, &self->pt_statelock);
self->pt_state = PT_STATE_BLOCKED_QUEUE;
self->pt_sleepobj = rwlock;
self->pt_sleepq = &rwlock->ptr_rblocked;
self->pt_sleeplock = &rwlock->ptr_interlock;
pthread_spinunlock(self, &self->pt_statelock);
pthread__block(self, &rwlock->ptr_interlock);
/* interlock is not held when we return */
pthread_spinlock(self, &rwlock->ptr_interlock);
}
rwlock->ptr_nreaders++;
pthread_spinunlock(self, &rwlock->ptr_interlock);
return 0;
}
int
pthread_rwlock_tryrdlock(pthread_rwlock_t *rwlock)
{
pthread_t self;
#ifdef ERRORCHECK
if ((rwlock == NULL) || (rwlock->ptr_magic != _PT_RWLOCK_MAGIC))
return EINVAL;
#endif
self = pthread__self();
pthread_spinlock(self, &rwlock->ptr_interlock);
/*
* Don't get a readlock if there is a writer or if there are waiting
* writers; i.e. prefer writers to readers. This strategy is dictated
* by SUSv3.
*/
if ((rwlock->ptr_writer != NULL) ||
(!PTQ_EMPTY(&rwlock->ptr_wblocked))) {
pthread_spinunlock(self, &rwlock->ptr_interlock);
return EBUSY;
}
rwlock->ptr_nreaders++;
pthread_spinunlock(self, &rwlock->ptr_interlock);
return 0;
}
int
pthread_rwlock_wrlock(pthread_rwlock_t *rwlock)
{
pthread_t self;
extern int pthread__started;
#ifdef ERRORCHECK
if ((rwlock == NULL) || (rwlock->ptr_magic != _PT_RWLOCK_MAGIC))
return EINVAL;
#endif
self = pthread__self();
pthread_spinlock(self, &rwlock->ptr_interlock);
#ifdef ERRORCHECK
if (rwlock->ptr_writer == self) {
pthread_spinunlock(self, &rwlock->ptr_interlock);
return EDEADLK;
}
#endif
/*
* Prefer writers to readers here; permit writers even if there are
* waiting readers.
*/
while ((rwlock->ptr_nreaders > 0) || (rwlock->ptr_writer != NULL)) {
#ifdef ERRORCHECK
if (pthread__started == 0) {
pthread_spinunlock(self, &rwlock->ptr_interlock);
return EDEADLK;
}
#endif
PTQ_INSERT_TAIL(&rwlock->ptr_wblocked, self, pt_sleep);
/* Locking a rwlock is not a cancellation point; don't check */
pthread_spinlock(self, &self->pt_statelock);
self->pt_state = PT_STATE_BLOCKED_QUEUE;
self->pt_sleepobj = rwlock;
self->pt_sleepq = &rwlock->ptr_wblocked;
self->pt_sleeplock = &rwlock->ptr_interlock;
pthread_spinunlock(self, &self->pt_statelock);
pthread__block(self, &rwlock->ptr_interlock);
/* interlock is not held when we return */
pthread_spinlock(self, &rwlock->ptr_interlock);
}
rwlock->ptr_writer = self;
pthread_spinunlock(self, &rwlock->ptr_interlock);
return 0;
}
int
pthread_rwlock_trywrlock(pthread_rwlock_t *rwlock)
{
pthread_t self;
#ifdef ERRORCHECK
if ((rwlock == NULL) || (rwlock->ptr_magic != _PT_RWLOCK_MAGIC))
return EINVAL;
#endif
self = pthread__self();
pthread_spinlock(self, &rwlock->ptr_interlock);
/*
* Prefer writers to readers here; permit writers even if there are
* waiting readers.
*/
if ((rwlock->ptr_nreaders > 0) || (rwlock->ptr_writer != NULL)) {
pthread_spinunlock(self, &rwlock->ptr_interlock);
return EBUSY;
}
rwlock->ptr_writer = self;
pthread_spinunlock(self, &rwlock->ptr_interlock);
return 0;
}
struct pthread_rwlock__waitarg {
pthread_t ptw_thread;
pthread_rwlock_t *ptw_rwlock;
struct pthread_queue_t *ptw_queue;
};
int
pthread_rwlock_timedrdlock(pthread_rwlock_t *rwlock,
const struct timespec *abs_timeout)
{
pthread_t self;
struct pthread_rwlock__waitarg wait;
struct pt_alarm_t alarm;
int retval;
#ifdef ERRORCHECK
if ((rwlock == NULL) || (rwlock->ptr_magic != _PT_RWLOCK_MAGIC))
return EINVAL;
if (abs_timeout == NULL)
return EINVAL;
#endif
if ((abs_timeout->tv_nsec >= 1000000000) ||
(abs_timeout->tv_nsec < 0) ||
(abs_timeout->tv_sec < 0))
return EINVAL;
self = pthread__self();
pthread_spinlock(self, &rwlock->ptr_interlock);
#ifdef ERRORCHECK
if (rwlock->ptr_writer == self) {
pthread_spinunlock(self, &rwlock->ptr_interlock);
return EDEADLK;
}
#endif
/*
* Don't get a readlock if there is a writer or if there are waiting
* writers; i.e. prefer writers to readers. This strategy is dictated
* by SUSv3.
*/
retval = 0;
while ((retval == 0) && ((rwlock->ptr_writer != NULL) ||
(!PTQ_EMPTY(&rwlock->ptr_wblocked)))) {
wait.ptw_thread = self;
wait.ptw_rwlock = rwlock;
wait.ptw_queue = &rwlock->ptr_rblocked;
pthread__alarm_add(self, &alarm, abs_timeout,
pthread_rwlock__callback, &wait);
PTQ_INSERT_TAIL(&rwlock->ptr_rblocked, self, pt_sleep);
/* Locking a rwlock is not a cancellation point; don't check */
pthread_spinlock(self, &self->pt_statelock);
self->pt_state = PT_STATE_BLOCKED_QUEUE;
self->pt_sleepobj = rwlock;
self->pt_sleepq = &rwlock->ptr_rblocked;
self->pt_sleeplock = &rwlock->ptr_interlock;
pthread_spinunlock(self, &self->pt_statelock);
pthread__block(self, &rwlock->ptr_interlock);
/* interlock is not held when we return */
pthread__alarm_del(self, &alarm);
if (pthread__alarm_fired(&alarm))
retval = ETIMEDOUT;
pthread_spinlock(self, &rwlock->ptr_interlock);
}
/* One last chance to get the lock, in case it was released between
the alarm firing and when this thread got rescheduled, or in case
a signal handler kept it busy */
if ((rwlock->ptr_writer == NULL) &&
(PTQ_EMPTY(&rwlock->ptr_wblocked))) {
rwlock->ptr_nreaders++;
retval = 0;
}
pthread_spinunlock(self, &rwlock->ptr_interlock);
return retval;
}
int
pthread_rwlock_timedwrlock(pthread_rwlock_t *rwlock,
const struct timespec *abs_timeout)
{
struct pthread_rwlock__waitarg wait;
struct pt_alarm_t alarm;
pthread_t self;
int retval;
extern int pthread__started;
#ifdef ERRORCHECK
if ((rwlock == NULL) || (rwlock->ptr_magic != _PT_RWLOCK_MAGIC))
return EINVAL;
if (abs_timeout == NULL)
return EINVAL;
#endif
if ((abs_timeout->tv_nsec >= 1000000000) ||
(abs_timeout->tv_nsec < 0) ||
(abs_timeout->tv_sec < 0))
return EINVAL;
self = pthread__self();
pthread_spinlock(self, &rwlock->ptr_interlock);
#ifdef ERRORCHECK
if (rwlock->ptr_writer == self) {
pthread_spinunlock(self, &rwlock->ptr_interlock);
return EDEADLK;
}
#endif
/*
* Prefer writers to readers here; permit writers even if there are
* waiting readers.
*/
retval = 0;
while (retval == 0 &&
((rwlock->ptr_nreaders > 0) || (rwlock->ptr_writer != NULL))) {
#ifdef ERRORCHECK
if (pthread__started == 0) {
pthread_spinunlock(self, &rwlock->ptr_interlock);
return EDEADLK;
}
#endif
wait.ptw_thread = self;
wait.ptw_rwlock = rwlock;
wait.ptw_queue = &rwlock->ptr_wblocked;
pthread__alarm_add(self, &alarm, abs_timeout,
pthread_rwlock__callback, &wait);
PTQ_INSERT_TAIL(&rwlock->ptr_wblocked, self, pt_sleep);
/* Locking a rwlock is not a cancellation point; don't check */
pthread_spinlock(self, &self->pt_statelock);
self->pt_state = PT_STATE_BLOCKED_QUEUE;
self->pt_sleepobj = rwlock;
self->pt_sleepq = &rwlock->ptr_wblocked;
self->pt_sleeplock = &rwlock->ptr_interlock;
pthread_spinunlock(self, &self->pt_statelock);
pthread__block(self, &rwlock->ptr_interlock);
/* interlock is not held when we return */
pthread__alarm_del(self, &alarm);
if (pthread__alarm_fired(&alarm))
retval = ETIMEDOUT;
pthread_spinlock(self, &rwlock->ptr_interlock);
}
if ((rwlock->ptr_nreaders == 0) && (rwlock->ptr_writer == NULL)) {
rwlock->ptr_writer = self;
retval = 0;
}
pthread_spinunlock(self, &rwlock->ptr_interlock);
return retval;
}
static void
pthread_rwlock__callback(void *arg)
{
struct pthread_rwlock__waitarg *a;
pthread_t self;
a = arg;
self = pthread__self();
pthread_spinlock(self, &a->ptw_rwlock->ptr_interlock);
/*
* Don't dequeue and schedule the thread if it's already been
* queued up by a signal or broadcast (but hasn't yet run as far
* as pthread__alarm_del(), or we wouldn't be here, and hence can't
* have become blocked on some *other* queue).
*/
if (a->ptw_thread->pt_state == PT_STATE_BLOCKED_QUEUE) {
PTQ_REMOVE(a->ptw_queue, a->ptw_thread, pt_sleep);
pthread__sched(self, a->ptw_thread);
}
pthread_spinunlock(self, &a->ptw_rwlock->ptr_interlock);
}
int
pthread_rwlock_unlock(pthread_rwlock_t *rwlock)
{
pthread_t self, writer;
struct pthread_queue_t blockedq;
#ifdef ERRORCHECK
if ((rwlock == NULL) || (rwlock->ptr_magic != _PT_RWLOCK_MAGIC))
return EINVAL;
#endif
writer = NULL;
PTQ_INIT(&blockedq);
self = pthread__self();
pthread_spinlock(self, &rwlock->ptr_interlock);
if (rwlock->ptr_writer != NULL) {
/* Releasing a write lock. */
#ifdef ERRORCHECK
if (rwlock->ptr_writer != self) {
pthread_spinunlock(self, &rwlock->ptr_interlock);
return EPERM;
}
#endif
rwlock->ptr_writer = NULL;
writer = PTQ_FIRST(&rwlock->ptr_wblocked);
if (writer != NULL) {
PTQ_REMOVE(&rwlock->ptr_wblocked, writer, pt_sleep);
} else {
blockedq = rwlock->ptr_rblocked;
PTQ_INIT(&rwlock->ptr_rblocked);
}
} else
#ifdef ERRORCHECK
if (rwlock->ptr_nreaders > 0)
#endif
{
/* Releasing a read lock. */
rwlock->ptr_nreaders--;
if (rwlock->ptr_nreaders == 0) {
writer = PTQ_FIRST(&rwlock->ptr_wblocked);
if (writer != NULL)
PTQ_REMOVE(&rwlock->ptr_wblocked, writer,
pt_sleep);
}
#ifdef ERRORCHECK
} else {
pthread_spinunlock(self, &rwlock->ptr_interlock);
return EPERM;
#endif
}
if (writer != NULL)
pthread__sched(self, writer);
else
pthread__sched_sleepers(self, &blockedq);
pthread_spinunlock(self, &rwlock->ptr_interlock);
return 0;
}
int
pthread_rwlockattr_init(pthread_rwlockattr_t *attr)
{
#ifdef ERRORCHECK
if (attr == NULL)
return EINVAL;
#endif
attr->ptra_magic = _PT_RWLOCKATTR_MAGIC;
return 0;
}
int
pthread_rwlockattr_destroy(pthread_rwlockattr_t *attr)
{
#ifdef ERRORCHECK
if ((attr == NULL) ||
(attr->ptra_magic != _PT_RWLOCKATTR_MAGIC))
return EINVAL;
#endif
attr->ptra_magic = _PT_RWLOCKATTR_DEAD;
return 0;
}