1 files changed, 419 insertions, 0 deletions
diff --git a/lib/libpthread/thread/thr_rwlock.c b/lib/libpthread/thread/thr_rwlock.c
new file mode 100644
index 0000000..ca8a081
--- /dev/null
+++ b/lib/libpthread/thread/thr_rwlock.c
@@ -0,0 +1,419 @@
+/*-
+ * 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)
+
+__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));
+}