Implement pthread read/write locks as defined by Version 2 of the Single

UNIX Specification.

As with our standard mutexes, process shared locks are not supported at
this time.

4 files changed, 445 insertions, 1 deletions

diff --git a/lib/libkse/thread/Makefile.inc b/lib/libkse/thread/Makefile.inc
index dc46af9..4fd3034 100644
--- a/lib/libkse/thread/Makefile.inc
+++ b/lib/libkse/thread/Makefile.inc
@@ -1,4 +1,4 @@
-#	$Id: Makefile.inc,v 1.12 1998/05/31 23:48:26 jb Exp $
+#	$Id: Makefile.inc,v 1.13 1998/06/01 02:14:34 jb Exp $
 
 # uthread sources
 .PATH: ${.CURDIR}/uthread
@@ -67,6 +67,8 @@ SRCS+= \
 	uthread_recvfrom.c \
 	uthread_recvmsg.c \
 	uthread_resume_np.c \
+	uthread_rwlock.c \
+	uthread_rwlockattr.c \
 	uthread_select.c \
 	uthread_self.c \
 	uthread_sendmsg.c \
diff --git a/lib/libkse/thread/thr_private.h b/lib/libkse/thread/thr_private.h
index 39ce14d..5b76a86 100644
--- a/lib/libkse/thread/thr_private.h
+++ b/lib/libkse/thread/thr_private.h
@@ -224,6 +224,18 @@ struct pthread_key {
 	void            (*destructor) ();
 };
 
+struct pthread_rwlockattr {
+	int		pshared;
+};
+
+struct pthread_rwlock {
+	pthread_mutex_t	lock;	/* monitor lock */
+	int		state;	/* 0 = idle  >0 = # of readers  -1 = writer */
+	pthread_cond_t	read_signal;
+	pthread_cond_t	write_signal;
+	int		blocked_writers;
+};
+
 /*
  * Thread states.
  */
diff --git a/lib/libkse/thread/thr_rwlock.c b/lib/libkse/thread/thr_rwlock.c
new file mode 100644
index 0000000..356eb29
--- /dev/null
+++ b/lib/libkse/thread/thr_rwlock.c
@@ -0,0 +1,333 @@
+/*-
+ * 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.
+ *
+ *	$Id$
+ */
+
+#ifdef _THREAD_SAFE
+#include <errno.h>
+#include <limits.h>
+#include <stdlib.h>
+
+#include <pthread.h>
+#include "pthread_private.h"
+
+/* maximum number of times a read lock may be obtained */
+#define	MAX_READ_LOCKS		(INT_MAX - 1)
+
+static int init_static (pthread_rwlock_t *rwlock);
+
+static spinlock_t static_init_lock = _SPINLOCK_INITIALIZER;
+
+static int
+init_static (pthread_rwlock_t *rwlock)
+{
+	int ret;
+
+	_SPINLOCK(&static_init_lock);
+
+	if (*rwlock == NULL)
+		ret = pthread_rwlock_init(rwlock, NULL);
+	else
+		ret = 0;
+
+	_SPINUNLOCK(&static_init_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;
+	}
+
+	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);
+}
+
+int
+pthread_rwlock_rdlock (pthread_rwlock_t *rwlock)
+{
+	pthread_rwlock_t 	prwlock;
+	int			ret = 0;
+
+	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);
+
+	/* give writers priority over readers */
+	while (prwlock->blocked_writers || prwlock->state < 0) {
+		ret = pthread_cond_wait(&prwlock->read_signal, &prwlock->lock);
+
+		if (ret != 0) {
+			/* can't do a whole lot if this fails */
+			pthread_mutex_unlock(&prwlock->lock);
+			return(ret);
+		}
+	}
+
+	/* check lock count */
+	if (prwlock->state == MAX_READ_LOCKS)
+		ret = EAGAIN;
+	else
+		++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.
+	 */
+	pthread_mutex_unlock(&prwlock->lock);
+
+	return(ret);
+}
+
+int
+pthread_rwlock_tryrdlock (pthread_rwlock_t *rwlock)
+{
+	pthread_rwlock_t 	prwlock;
+	int			ret = 0;
+
+	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);
+
+	/* give writers priority over readers */
+	if (prwlock->blocked_writers || prwlock->state < 0)
+		ret = EWOULDBLOCK;
+	else if (prwlock->state == MAX_READ_LOCKS)
+		ret = EAGAIN; /* too many read locks acquired */
+	else
+		++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 = 0;
+
+	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 = EWOULDBLOCK;
+	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)
+{
+	pthread_rwlock_t 	prwlock;
+	int			ret = 0;
+
+	if (rwlock == NULL)
+		return(EINVAL);
+
+	prwlock = *rwlock;
+
+	if (prwlock == NULL)
+		return(EINVAL);
+
+	/* grab the monitor lock */
+	if ((ret = pthread_mutex_lock(&prwlock->lock)) != 0)
+		return(ret);
+
+	if (prwlock->state > 0) {
+		if (--prwlock->state == 0 && prwlock->blocked_writers)
+			ret = pthread_cond_signal(&prwlock->write_signal);
+	} else if (prwlock->state < 0) {
+		prwlock->state = 0;
+
+		if (prwlock->blocked_writers)
+			ret = pthread_cond_signal(&prwlock->write_signal);
+		else
+			ret = pthread_cond_broadcast(&prwlock->read_signal);
+	} else
+		ret = EINVAL;
+
+	/* see the comment on this in pthread_rwlock_rdlock */
+	pthread_mutex_unlock(&prwlock->lock);
+
+	return(ret);
+}
+
+int
+pthread_rwlock_wrlock (pthread_rwlock_t *rwlock)
+{
+	pthread_rwlock_t 	prwlock;
+	int			ret = 0;
+
+	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);
+
+	while (prwlock->state != 0) {
+		++prwlock->blocked_writers;
+
+		ret = pthread_cond_wait(&prwlock->write_signal, &prwlock->lock);
+
+		if (ret != 0) {
+			--prwlock->blocked_writers;
+			pthread_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 */
+	pthread_mutex_unlock(&prwlock->lock);
+
+	return(ret);
+}
+
+#endif /* _THREAD_SAFE */
diff --git a/lib/libkse/thread/thr_rwlockattr.c b/lib/libkse/thread/thr_rwlockattr.c
new file mode 100644
index 0000000..a3683bc
--- /dev/null
+++ b/lib/libkse/thread/thr_rwlockattr.c
@@ -0,0 +1,97 @@
+/*-
+ * 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.
+ *
+ *	$Id$
+ */
+
+#ifdef _THREAD_SAFE
+#include <errno.h>
+
+#include <pthread.h>
+#include "pthread_private.h"
+
+int
+pthread_rwlockattr_destroy (pthread_rwlockattr_t *rwlockattr)
+{
+	pthread_rwlockattr_t prwlockattr;
+
+	if (rwlockattr == NULL)
+		return(EINVAL);
+
+	prwlockattr = *rwlockattr;
+
+	if (prwlockattr == NULL)
+		return(EINVAL);
+
+	free(prwlockattr);
+
+	return(0);
+}
+
+int
+pthread_rwlockattr_getpshared (const pthread_rwlockattr_t *rwlockattr,
+	int *pshared)
+{
+	*pshared = (*rwlockattr)->pshared;
+
+	return(0);
+}
+
+int
+pthread_rwlockattr_init (pthread_rwlockattr_t *rwlockattr)
+{
+	pthread_rwlockattr_t prwlockattr;
+
+	if (rwlockattr == NULL)
+		return(EINVAL);
+
+	prwlockattr = (pthread_rwlockattr_t)
+		malloc(sizeof(struct pthread_rwlockattr));
+
+	if (prwlockattr == NULL)
+		return(ENOMEM);
+
+	prwlockattr->pshared 	= PTHREAD_PROCESS_PRIVATE;
+	*rwlockattr		= prwlockattr;
+
+	return(0);
+}
+
+int
+pthread_rwlockattr_setpshared (pthread_rwlockattr_t *rwlockattr,
+	int *pshared)
+{
+	int ps = *pshared;
+
+	/* only PTHREAD_PROCESS_PRIVATE is supported */
+	if (ps != PTHREAD_PROCESS_PRIVATE)
+		return(EINVAL);
+
+	(*rwlockattr)->pshared = ps;
+
+	return(0);
+}
+
+#endif /* _THREAD_SAFE */