RWLOCK(9): Add reader/writer lock implementation

4 files changed, 749 insertions, 30 deletions

diff --git a/rtemsbsd/include/machine/rtems-bsd-rwlock.h b/rtemsbsd/include/machine/rtems-bsd-rwlock.h
new file mode 100644
index 00000000..51b41604
--- /dev/null
+++ b/rtemsbsd/include/machine/rtems-bsd-rwlock.h
@@ -0,0 +1,60 @@
+/**
+ * @file
+ *
+ * @ingroup rtems_bsd_machine
+ *
+ * @brief TODO.
+ */
+
+/*
+ * Copyright (c) 2017 embedded brains GmbH.  All rights reserved.
+ *
+ *  embedded brains GmbH
+ *  Dornierstr. 4
+ *  82178 Puchheim
+ *  Germany
+ *  <rtems@embedded-brains.de>
+ *
+ * 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.
+ */
+
+#ifndef _RTEMS_BSD_MACHINE_RTEMS_BSD_RWLOCK_H_
+#define _RTEMS_BSD_MACHINE_RTEMS_BSD_RWLOCK_H_
+
+#include <rtems/score/threadq.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif /* __cplusplus */
+
+typedef struct {
+	Thread_queue_Control	writer_queue;
+	Thread_queue_Control	reader_queue;
+	int			readers;
+	int			nest_level;
+} rtems_bsd_rwlock;
+
+#ifdef __cplusplus
+}
+#endif /* __cplusplus */
+
+#endif /* _RTEMS_BSD_MACHINE_RTEMS_BSD_RWLOCK_H_ */
diff --git a/rtemsbsd/include/machine/rtems-bsd-rwlockimpl.h b/rtemsbsd/include/machine/rtems-bsd-rwlockimpl.h
new file mode 100644
index 00000000..663e7000
--- /dev/null
+++ b/rtemsbsd/include/machine/rtems-bsd-rwlockimpl.h
@@ -0,0 +1,429 @@
+/**
+ * @file
+ *
+ * @ingroup rtems_bsd_machine
+ *
+ * @brief Implementation of a reader/writer lock with priority inheritance for
+ * exclusive owners (writer).
+ */
+
+/*
+ * Copyright (c) 2017 embedded brains GmbH.  All rights reserved.
+ *
+ *  embedded brains GmbH
+ *  Dornierstr. 4
+ *  82178 Puchheim
+ *  Germany
+ *  <rtems@embedded-brains.de>
+ *
+ * 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.
+ */
+
+#ifndef _RTEMS_BSD_MACHINE_RTEMS_BSD_RWLOCKIMPL_H_
+#define _RTEMS_BSD_MACHINE_RTEMS_BSD_RWLOCKIMPL_H_
+
+#include <machine/rtems-bsd-rwlock.h>
+#include <machine/rtems-bsd-support.h>
+
+#include <sys/types.h>
+#include <sys/lock.h>
+
+#include <rtems/score/threadimpl.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif /* __cplusplus */
+
+typedef struct {
+	Thread_queue_Context writer;
+	Thread_queue_Context reader;
+} rtems_bsd_rwlock_context;
+
+static inline void
+rtems_bsd_rwlock_context_init(rtems_bsd_rwlock_context *context)
+{
+
+	_Thread_queue_Context_initialize(&context->writer);
+}
+
+static inline void
+rtems_bsd_rwlock_init(struct lock_object *lock, rtems_bsd_rwlock *rw,
+    struct lock_class *class, const char *name, const char *type, int flags)
+{
+	_Thread_queue_Initialize(&rw->writer_queue, name);
+	_Thread_queue_Initialize(&rw->reader_queue, name);
+	rw->readers = 0;
+	rw->nest_level = 0;
+	lock_init(lock, class, name, type, flags);
+}
+
+void rtems_bsd_rwlock_wlock_more(const struct lock_object *lock,
+    rtems_bsd_rwlock *rw, Thread_Control *executing,
+    rtems_bsd_rwlock_context *context);
+
+void rtems_bsd_rwlock_wunlock_more(rtems_bsd_rwlock *rw,
+    Thread_Control *wowner, rtems_bsd_rwlock_context *context);
+
+void rtems_bsd_rwlock_rlock_more(rtems_bsd_rwlock *rw,
+    rtems_bsd_rwlock_context *context);
+
+void rtems_bsd_rwlock_runlock_more(rtems_bsd_rwlock *rw,
+    rtems_bsd_rwlock_context *context);
+
+void rtems_bsd_rwlock_ready_waiting_readers(rtems_bsd_rwlock *rw,
+    rtems_bsd_rwlock_context *context);
+
+#define	rtems_bsd_rwlock_isr_disable(isr_level, context)	\
+do {								\
+	_ISR_Local_disable(isr_level);				\
+	_ISR_lock_ISR_disable_profile(				\
+	      &(context)->writer.Lock_context.Lock_context)	\
+} while (0)
+
+static inline void
+rtems_bsd_rwlock_acquire_critical(rtems_bsd_rwlock *rw,
+    rtems_bsd_rwlock_context *context)
+{
+
+	_Thread_queue_Queue_acquire_critical(&rw->writer_queue.Queue,
+	    &rw->writer_queue.Lock_stats,
+	    &context->writer.Lock_context.Lock_context);
+#if defined(RTEMS_SMP) && defined(RTEMS_DEBUG)
+	rw->writer_queue.owner = _SMP_lock_Who_am_I();
+#endif
+}
+
+static inline void
+rtems_bsd_rwlock_release(rtems_bsd_rwlock *rw, ISR_Level isr_level,
+    rtems_bsd_rwlock_context *context)
+{
+
+#if defined(RTEMS_SMP) && defined(RTEMS_DEBUG)
+	_Assert( _Thread_queue_Is_lock_owner( &rw->writer_queue ) );
+	rw->writer_queue.owner = SMP_LOCK_NO_OWNER;
+#endif
+	_Thread_queue_Queue_release_critical(&rw->writer_queue.Queue,
+	    &context->writer.Lock_context.Lock_context);
+	_ISR_Local_enable(isr_level);
+}
+
+static inline void
+rtems_bsd_rwlock_set_isr_level(rtems_bsd_rwlock_context *context,
+    ISR_Level isr_level)
+{
+
+	_ISR_lock_Context_set_level(&context->writer.Lock_context.Lock_context,
+	    isr_level);
+}
+
+static inline Thread_Control *
+rtems_bsd_rwlock_wowner(const rtems_bsd_rwlock *rw)
+{
+
+	return (rw->writer_queue.Queue.owner);
+}
+
+static inline void
+rtems_bsd_rwlock_set_wowner(rtems_bsd_rwlock *rw, Thread_Control *wowner)
+{
+
+	rw->writer_queue.Queue.owner = wowner;
+}
+
+static inline void
+rtems_bsd_rwlock_wlock(struct lock_object *lock, rtems_bsd_rwlock *rw)
+{
+	ISR_Level isr_level;
+	rtems_bsd_rwlock_context context;
+	Thread_Control *executing;
+
+	rtems_bsd_rwlock_context_init(&context);
+	rtems_bsd_rwlock_isr_disable(isr_level, &context);
+	executing = _Thread_Executing;
+	rtems_bsd_rwlock_acquire_critical(rw, &context);
+
+	if (__predict_true(rtems_bsd_rwlock_wowner(rw) == NULL &&
+	    rw->readers == 0)) {
+		rtems_bsd_rwlock_set_wowner(rw, executing);
+		_Thread_Resource_count_increment(executing);
+		rtems_bsd_rwlock_release(rw, isr_level, &context);
+	} else {
+		rtems_bsd_rwlock_set_isr_level(&context, isr_level);
+		rtems_bsd_rwlock_wlock_more(lock, rw, executing,
+		    &context);
+	}
+}
+
+static inline int
+rtems_bsd_rwlock_try_wlock(struct lock_object *lock, rtems_bsd_rwlock *rw)
+{
+	int success;
+	ISR_Level isr_level;
+	rtems_bsd_rwlock_context context;
+	Thread_Control *executing;
+
+	rtems_bsd_rwlock_context_init(&context);
+	rtems_bsd_rwlock_isr_disable(isr_level, &context);
+	executing = _Thread_Executing;
+	rtems_bsd_rwlock_acquire_critical(rw, &context);
+
+	if (rw->readers == 0) {
+		Thread_Control *wowner;
+
+		wowner = rtems_bsd_rwlock_wowner(rw);
+
+		if (wowner == NULL) {
+			rtems_bsd_rwlock_set_wowner(rw, executing);
+			_Thread_Resource_count_increment(executing);
+			success = 1;
+		} else if (wowner == executing) {
+			BSD_ASSERT(lock->lo_flags & LO_RECURSABLE);
+			++rw->nest_level;
+			success = 1;
+		} else {
+			success = 0;
+		}
+	} else {
+		success = 0;
+	}
+
+	rtems_bsd_rwlock_release(rw, isr_level, &context);
+
+	return (success);
+}
+
+static inline void
+rtems_bsd_rwlock_wunlock(rtems_bsd_rwlock *rw)
+{
+	ISR_Level isr_level;
+	rtems_bsd_rwlock_context context;
+	Thread_Control *wowner;
+	int nest_level;
+
+	rtems_bsd_rwlock_context_init(&context);
+	rtems_bsd_rwlock_isr_disable(isr_level, &context);
+	rtems_bsd_rwlock_acquire_critical(rw, &context);
+
+	nest_level = rw->nest_level;
+	wowner = rtems_bsd_rwlock_wowner(rw);
+
+	BSD_ASSERT(wowner == _Thread_Executing);
+
+	if (__predict_true(nest_level == 0)) {
+		rtems_bsd_rwlock_set_wowner(rw, NULL);
+		_Thread_Resource_count_decrement(wowner);
+
+		if (__predict_true(
+		    _Thread_queue_Is_empty(&rw->writer_queue.Queue) &&
+		    _Thread_queue_Is_empty(&rw->reader_queue.Queue))) {
+			rtems_bsd_rwlock_release(rw, isr_level, &context);
+		} else {
+			rtems_bsd_rwlock_set_isr_level(&context,
+			    isr_level);
+			rtems_bsd_rwlock_wunlock_more(rw, wowner,
+			    &context);
+		}
+	} else {
+		rw->nest_level = nest_level - 1;
+		rtems_bsd_rwlock_release(rw, isr_level, &context);
+	}
+}
+
+static inline int
+rtems_bsd_rwlock_wowned(const rtems_bsd_rwlock *rw)
+{
+
+	return (rtems_bsd_rwlock_wowner(rw) == _Thread_Get_executing());
+}
+
+static inline int
+rtems_bsd_rwlock_recursed(const rtems_bsd_rwlock *rw)
+{
+
+	return (rw->nest_level != 0);
+}
+
+static inline void
+rtems_bsd_rwlock_rlock(struct lock_object *lock, rtems_bsd_rwlock *rw)
+{
+	ISR_Level isr_level;
+	rtems_bsd_rwlock_context context;
+
+	rtems_bsd_rwlock_context_init(&context);
+	rtems_bsd_rwlock_isr_disable(isr_level, &context);
+	rtems_bsd_rwlock_acquire_critical(rw, &context);
+
+	if (__predict_true(rtems_bsd_rwlock_wowner(rw) == NULL &&
+	   _Thread_queue_Is_empty(&rw->writer_queue.Queue))) {
+		++rw->readers;
+		_Thread_Resource_count_increment(_Thread_Executing);
+		rtems_bsd_rwlock_release(rw, isr_level, &context);
+	} else {
+		rtems_bsd_rwlock_set_isr_level(&context, isr_level);
+		rtems_bsd_rwlock_rlock_more(rw, &context);
+	}
+}
+
+static inline int
+rtems_bsd_rwlock_try_rlock(struct lock_object *lock, rtems_bsd_rwlock *rw)
+{
+	int success;
+	ISR_Level isr_level;
+	rtems_bsd_rwlock_context context;
+
+	rtems_bsd_rwlock_context_init(&context);
+	rtems_bsd_rwlock_isr_disable(isr_level, &context);
+	rtems_bsd_rwlock_acquire_critical(rw, &context);
+
+	if (__predict_true(rtems_bsd_rwlock_wowner(rw) == NULL &&
+	   _Thread_queue_Is_empty(&rw->writer_queue.Queue))) {
+		++rw->readers;
+		_Thread_Resource_count_increment(_Thread_Executing);
+		success = 1;
+	} else {
+		success = 0;
+	}
+
+	rtems_bsd_rwlock_release(rw, isr_level, &context);
+
+	return (success);
+}
+
+static inline void
+rtems_bsd_rwlock_runlock(rtems_bsd_rwlock *rw)
+{
+	ISR_Level isr_level;
+	rtems_bsd_rwlock_context context;
+	int readers;
+
+	rtems_bsd_rwlock_context_init(&context);
+	rtems_bsd_rwlock_isr_disable(isr_level, &context);
+	rtems_bsd_rwlock_acquire_critical(rw, &context);
+
+	readers = rw->readers;
+	_Thread_Resource_count_decrement(_Thread_Executing);
+
+	if (__predict_true(readers == 1)) {
+		rw->readers = 0;
+
+		if (__predict_true(
+		    _Thread_queue_Is_empty(&rw->writer_queue.Queue) &&
+		    _Thread_queue_Is_empty(&rw->reader_queue.Queue))) {
+			rtems_bsd_rwlock_release(rw, isr_level,
+			    &context);
+		} else {
+			rtems_bsd_rwlock_set_isr_level(&context,
+			    isr_level);
+			rtems_bsd_rwlock_runlock_more(rw, &context);
+		}
+	} else {
+		rw->readers = readers - 1;
+		rtems_bsd_rwlock_release(rw, isr_level, &context);
+	}
+}
+
+static inline int
+rtems_bsd_rwlock_try_upgrade(rtems_bsd_rwlock *rw)
+{
+	int success;
+	ISR_Level isr_level;
+	rtems_bsd_rwlock_context context;
+	Thread_Control *executing;
+	Thread_Control *wowner;
+
+	rtems_bsd_rwlock_context_init(&context);
+	rtems_bsd_rwlock_isr_disable(isr_level, &context);
+	executing = _Thread_Executing;
+	rtems_bsd_rwlock_acquire_critical(rw, &context);
+
+	wowner = rtems_bsd_rwlock_wowner(rw);
+	BSD_ASSERT(wowner == NULL);
+
+	if (rw->readers == 1) {
+		rw->readers = 0;
+		rtems_bsd_rwlock_set_wowner(rw, executing);
+		/* FIXME: priority inheritance */
+		success = 1;
+	} else {
+		success = 0;
+	}
+
+	rtems_bsd_rwlock_release(rw, isr_level, &context);
+
+	return (success);
+}
+
+static inline void
+rtems_bsd_rwlock_downgrade(rtems_bsd_rwlock *rw)
+{
+	ISR_Level isr_level;
+	rtems_bsd_rwlock_context context;
+	Thread_Control *wowner;
+
+	rtems_bsd_rwlock_context_init(&context);
+	rtems_bsd_rwlock_isr_disable(isr_level, &context);
+	rtems_bsd_rwlock_acquire_critical(rw, &context);
+
+	wowner = rtems_bsd_rwlock_wowner(rw);
+
+	BSD_ASSERT(wowner == _Thread_Executing);
+	BSD_ASSERT(rw->nest_level == 0);
+
+	rtems_bsd_rwlock_set_wowner(rw, NULL);
+	rw->readers = 1;
+
+	if (__predict_true(_Thread_queue_Is_empty(&rw->reader_queue.Queue))) {
+		rtems_bsd_rwlock_release(rw, isr_level, &context);
+	} else {
+		rtems_bsd_rwlock_set_isr_level(&context, isr_level);
+		rtems_bsd_rwlock_ready_waiting_readers(rw, &context);
+	}
+}
+
+static inline const char *
+rtems_bsd_rwlock_name(const rtems_bsd_rwlock *rw)
+{
+
+	return (rw->writer_queue.Queue.name);
+}
+
+static inline void
+rtems_bsd_rwlock_destroy(struct lock_object *lock, rtems_bsd_rwlock *rw)
+{
+	BSD_ASSERT(_Thread_queue_Is_empty(&rw->writer_queue.Queue));
+	BSD_ASSERT(_Thread_queue_Is_empty(&rw->reader_queue.Queue));
+
+	if (rtems_bsd_rwlock_wowned(rw)) {
+		rw->nest_level = 0;
+		rtems_bsd_rwlock_wunlock(rw);
+	}
+
+	_Thread_queue_Destroy(&rw->writer_queue);
+	_Thread_queue_Destroy(&rw->reader_queue);
+	lock_destroy(lock);
+}
+
+#ifdef __cplusplus
+}
+#endif /* __cplusplus */
+
+#endif /* _RTEMS_BSD_MACHINE_RTEMS_BSD_RWLOCKIMPL_H_ */
diff --git a/rtemsbsd/rtems/rtems-kernel-rwlock.c b/rtemsbsd/rtems/rtems-kernel-rwlock.c
index 80918f70..c2002e0e 100644
--- a/rtemsbsd/rtems/rtems-kernel-rwlock.c
+++ b/rtemsbsd/rtems/rtems-kernel-rwlock.c
@@ -15,7 +15,7 @@
  *  USA
  *  <kevin.kirspel@optimedical.com>
  *
- * Copyright (c) 2013-2015 embedded brains GmbH.  All rights reserved.
+ * Copyright (c) 2013, 2017 embedded brains GmbH.  All rights reserved.
  *
  *  embedded brains GmbH
  *  Dornierstr. 4
@@ -23,6 +23,9 @@
  *  Germany
  *  <rtems@embedded-brains.de>
  *
+ * Copyright (c) 2006 John Baldwin <jhb@FreeBSD.org>
+ * All rights reserved.
+ *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
@@ -46,7 +49,7 @@
  */
 
 #include <machine/rtems-bsd-kernel-space.h>
-#include <machine/rtems-bsd-muteximpl.h>
+#include <machine/rtems-bsd-rwlockimpl.h>
 
 #include <sys/param.h>
 #include <sys/types.h>
@@ -70,9 +73,9 @@ struct lock_class lock_class_rw = {
 	.lc_unlock = unlock_rw,
 };
 
-#define	rw_wowner(rw) rtems_bsd_mutex_owner(&(rw)->mutex)
+#define	rw_wowner(rw) rtems_bsd_rwlock_wowner(&(rw)->rwlock)
 
-#define	rw_recursed(rw) rtems_bsd_mutex_recursed(&(rw)->mutex)
+#define	rw_recursed(rw) rtems_bsd_rwlock_recursed(&(rw)->rwlock)
 
 void
 assert_rw(const struct lock_object *lock, int what)
@@ -84,16 +87,29 @@ assert_rw(const struct lock_object *lock, int what)
 void
 lock_rw(struct lock_object *lock, uintptr_t how)
 {
+	struct rwlock *rw;
 
-	rw_wlock((struct rwlock *)lock);
+	rw = (struct rwlock *)lock;
+	if (how)
+		rw_rlock(rw);
+	else
+		rw_wlock(rw);
 }
 
 uintptr_t
 unlock_rw(struct lock_object *lock)
 {
-
-	rw_unlock((struct rwlock *)lock);
-	return (0);
+	struct rwlock *rw;
+
+	rw = (struct rwlock *)lock;
+	rw_assert(rw, RA_LOCKED | LA_NOTRECURSED);
+	if (rw->rwlock.readers > 0) {
+		rw_runlock(rw);
+		return (1);
+	} else {
+		rw_wunlock(rw);
+		return (0);
+	}
 }
 
 void
@@ -105,7 +121,7 @@ rw_init_flags(struct rwlock *rw, const char *name, int opts)
 	if (opts & RW_RECURSE)
 		flags |= LO_RECURSABLE;
 
-	rtems_bsd_mutex_init(&rw->lock_object, &rw->mutex, &lock_class_rw,
+	rtems_bsd_rwlock_init(&rw->lock_object, &rw->rwlock, &lock_class_rw,
 	    name, NULL, flags);
 }
 
@@ -113,77 +129,87 @@ void
 rw_destroy(struct rwlock *rw)
 {
 
-	rtems_bsd_mutex_destroy(&rw->lock_object, &rw->mutex);
+	rtems_bsd_rwlock_destroy(&rw->lock_object, &rw->rwlock);
 }
 
 void
 rw_sysinit(void *arg)
 {
-  struct rw_args *args = arg;
+	struct rw_args *args = arg;
 
-  rw_init(args->ra_rw, args->ra_desc);
+	rw_init((struct rwlock *)args->ra_rw, args->ra_desc);
 }
 
 void
 rw_sysinit_flags(void *arg)
 {
-  struct rw_args_flags *args = arg;
+	struct rw_args_flags *args = arg;
 
-  rw_init_flags(args->ra_rw, args->ra_desc, args->ra_flags);
+	rw_init_flags((struct rwlock *)args->ra_rw, args->ra_desc,
+	    args->ra_flags);
 }
 
 int
 rw_wowned(struct rwlock *rw)
 {
-	return (rtems_bsd_mutex_owned(&rw->mutex));
+
+	return (rtems_bsd_rwlock_wowned(&rw->rwlock));
 }
 
 void
 _rw_wlock(struct rwlock *rw, const char *file, int line)
 {
-	rtems_bsd_mutex_lock(&rw->lock_object, &rw->mutex);
+
+	rtems_bsd_rwlock_wlock(&rw->lock_object, &rw->rwlock);
 }
 
 int
 _rw_try_wlock(struct rwlock *rw, const char *file, int line)
 {
-	return (rtems_bsd_mutex_trylock(&rw->lock_object, &rw->mutex));
+
+	return (rtems_bsd_rwlock_try_wlock(&rw->lock_object, &rw->rwlock));
 }
 
 void
 _rw_wunlock(struct rwlock *rw, const char *file, int line)
 {
-	rtems_bsd_mutex_unlock(&rw->mutex);
+
+	rtems_bsd_rwlock_wunlock(&rw->rwlock);
 }
 
 void
 _rw_rlock(struct rwlock *rw, const char *file, int line)
 {
-	rtems_bsd_mutex_lock(&rw->lock_object, &rw->mutex);
+
+	rtems_bsd_rwlock_rlock(&rw->lock_object, &rw->rwlock);
 }
 
 int
 _rw_try_rlock(struct rwlock *rw, const char *file, int line)
 {
-	return (rtems_bsd_mutex_trylock(&rw->lock_object, &rw->mutex));
+
+	return (rtems_bsd_rwlock_try_rlock(&rw->lock_object, &rw->rwlock));
 }
 
 void
 _rw_runlock(struct rwlock *rw, const char *file, int line)
 {
-	rtems_bsd_mutex_unlock(&rw->mutex);
+
+	rtems_bsd_rwlock_runlock(&rw->rwlock);
 }
 
 int
 _rw_try_upgrade(struct rwlock *rw, const char *file, int line)
 {
-	return (1);
+
+	return (rtems_bsd_rwlock_try_upgrade(&rw->rwlock));
 }
 
 void
 _rw_downgrade(struct rwlock *rw, const char *file, int line)
 {
-	/* Nothing to do */
+
+	rtems_bsd_rwlock_downgrade(&rw->rwlock);
 }
 
 #ifdef INVARIANT_SUPPORT
@@ -195,7 +221,7 @@ _rw_downgrade(struct rwlock *rw, const char *file, int line)
 void
 _rw_assert(const struct rwlock *rw, int what, const char *file, int line)
 {
-	const char *name = rtems_bsd_mutex_name(&rw->mutex);
+	const char *name = rtems_bsd_rwlock_name(&rw->rwlock);
 
 	switch (what) {
 	case RA_LOCKED:
@@ -204,6 +230,33 @@ _rw_assert(const struct rwlock *rw, int what, const char *file, int line)
 	case RA_RLOCKED:
 	case RA_RLOCKED | RA_RECURSED:
 	case RA_RLOCKED | RA_NOTRECURSED:
+#ifdef WITNESS
+		witness_assert(&rw->lock_object, what, file, line);
+#else
+		/*
+		 * If some other thread has a write lock or we have one
+		 * and are asserting a read lock, fail.  Also, if no one
+		 * has a lock at all, fail.
+		 */
+		if ((rw->rwlock.readers == 0 && rw_wowner(rw) == NULL) ||
+		    (rw->rwlock.readers == 0 && (what & RA_RLOCKED ||
+		    rw_wowner(rw) != _Thread_Get_executing())))
+			panic("Lock %s not %slocked @ %s:%d\n",
+			    name, (what & RA_RLOCKED) ?
+			    "read " : "", file, line);
+
+		if (rw->rwlock.readers == 0 && !(what & RA_RLOCKED)) {
+			if (rw_recursed(rw)) {
+				if (what & RA_NOTRECURSED)
+					panic("Lock %s recursed @ %s:%d\n",
+					    name, file,
+					    line);
+			} else if (what & RA_RECURSED)
+				panic("Lock %s not recursed @ %s:%d\n",
+				    name, file, line);
+		}
+#endif
+		break;
 	case RA_WLOCKED:
 	case RA_WLOCKED | RA_RECURSED:
 	case RA_WLOCKED | RA_NOTRECURSED:
@@ -212,11 +265,11 @@ _rw_assert(const struct rwlock *rw, int what, const char *file, int line)
 			    name, file, line);
 		if (rw_recursed(rw)) {
 			if (what & RA_NOTRECURSED)
-				panic("Lock %s recursed @ %s:%d\n", name, file,
-				    line);
+				panic("Lock %s recursed @ %s:%d\n",
+				    name, file, line);
 		} else if (what & RA_RECURSED)
-			panic("Lock %s not recursed @ %s:%d\n", name, file,
-			    line);
+			panic("Lock %s not recursed @ %s:%d\n",
+			    name, file, line);
 		break;
 	case RA_UNLOCKED:
 #ifdef WITNESS
@@ -227,8 +280,8 @@ _rw_assert(const struct rwlock *rw, int what, const char *file, int line)
 		 * to see if we hold a read lock or not.
 		 */
 		if (rw_wowner(rw) == _Thread_Get_executing())
-			panic("Lock %s exclusively locked @ %s:%d\n", name,
-			    file, line);
+			panic("Lock %s exclusively locked @ %s:%d\n",
+			    name, file, line);
 #endif
 		break;
 	default:
diff --git a/rtemsbsd/rtems/rtems-kernel-rwlockimpl.c b/rtemsbsd/rtems/rtems-kernel-rwlockimpl.c
new file mode 100644
index 00000000..2434e51d
--- /dev/null
+++ b/rtemsbsd/rtems/rtems-kernel-rwlockimpl.c
@@ -0,0 +1,177 @@
+/**
+ * @file
+ *
+ * @ingroup rtems_bsd_rtems
+ *
+ * @brief TODO.
+ */
+
+/*
+ * Copyright (c) 2017 embedded brains GmbH.  All rights reserved.
+ *
+ *  embedded brains GmbH
+ *  Dornierstr. 4
+ *  82178 Puchheim
+ *  Germany
+ *  <rtems@embedded-brains.de>
+ *
+ * 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.
+ */
+
+#include <machine/rtems-bsd-kernel-space.h>
+#include <machine/rtems-bsd-rwlockimpl.h>
+
+#include <rtems/score/schedulerimpl.h>
+
+void
+rtems_bsd_rwlock_wlock_more(const struct lock_object *lock,
+    rtems_bsd_rwlock *rw, Thread_Control *executing,
+    rtems_bsd_rwlock_context *context)
+{
+	Thread_Control *wowner;
+
+	wowner = rtems_bsd_rwlock_wowner(rw);
+
+	if (wowner == executing) {
+		BSD_ASSERT(lock->lo_flags & LO_RECURSABLE);
+		++rw->nest_level;
+
+		_Thread_queue_Release(&rw->writer_queue, &context->writer);
+	} else {
+		_Thread_queue_Context_set_thread_state(&context->writer,
+		    STATES_WAITING_FOR_RWLOCK);
+		_Thread_queue_Context_set_enqueue_do_nothing_extra(
+		    &context->writer);
+		_Thread_queue_Context_set_deadlock_callout(&context->writer,
+		    _Thread_queue_Deadlock_fatal);
+		_Thread_queue_Enqueue(&rw->writer_queue.Queue,
+		    &_Thread_queue_Operations_priority, executing,
+		    &context->writer);
+	}
+}
+
+static Thread_Control *
+rtems_bsd_rwlock_flush_reader_filter(Thread_Control *reader,
+    Thread_queue_Queue *queue, Thread_queue_Context *queue_context)
+{
+	rtems_bsd_rwlock *rw;
+
+	rw = RTEMS_CONTAINER_OF(queue, rtems_bsd_rwlock, reader_queue.Queue);
+	++rw->readers;
+	_Thread_Resource_count_increment(reader);
+	return (reader);
+}
+
+static void
+rtems_bsd_rwlock_flush_reader_post_release(Thread_queue_Queue *queue,
+    Thread_queue_Context *queue_context)
+{
+	rtems_bsd_rwlock *rw;
+	rtems_bsd_rwlock_context *context;
+
+	rw = RTEMS_CONTAINER_OF(queue, rtems_bsd_rwlock, reader_queue.Queue);
+	context = RTEMS_CONTAINER_OF(queue_context, rtems_bsd_rwlock_context,
+	    reader);
+	_Thread_queue_Release(&rw->writer_queue, &context->writer);
+}
+
+void
+rtems_bsd_rwlock_wunlock_more(rtems_bsd_rwlock *rw, Thread_Control *wowner,
+    rtems_bsd_rwlock_context *context)
+{
+
+	if (!_Thread_queue_Is_empty(&rw->reader_queue.Queue)) {
+		BSD_ASSERT(rw->readers == 0);
+		rtems_bsd_rwlock_ready_waiting_readers(rw, context);
+	} else {
+		BSD_ASSERT(!_Thread_queue_Is_empty(&rw->writer_queue.Queue));
+		_Thread_queue_Surrender(&rw->writer_queue.Queue,
+		    rw->writer_queue.Queue.heads, wowner, &context->writer,
+		    &_Thread_queue_Operations_priority);
+	}
+}
+
+static void
+rtems_bsd_rwlock_reader_enqueue(Thread_queue_Queue *queue,
+    Thread_Control *executing, Per_CPU_Control *cpu_self,
+    Thread_queue_Context *queue_context
+)
+{
+	rtems_bsd_rwlock *rw;
+	rtems_bsd_rwlock_context *context;
+
+	rw = RTEMS_CONTAINER_OF(queue, rtems_bsd_rwlock, reader_queue.Queue);
+	context = RTEMS_CONTAINER_OF(queue_context, rtems_bsd_rwlock_context,
+	    reader);
+	_Thread_queue_Release(&rw->writer_queue, &context->writer);
+}
+
+void
+rtems_bsd_rwlock_rlock_more(rtems_bsd_rwlock *rw,
+    rtems_bsd_rwlock_context *context)
+{
+	Thread_Control *executing;
+
+	executing = _Thread_Executing;
+
+	_Thread_queue_Context_initialize(&context->reader);
+	_Thread_queue_Context_set_thread_state(&context->reader,
+	    STATES_WAITING_FOR_RWLOCK);
+	_Thread_queue_Context_set_enqueue_callout(
+	    &context->reader, rtems_bsd_rwlock_reader_enqueue);
+	_Thread_queue_Context_set_deadlock_callout(&context->reader,
+	    _Thread_queue_Deadlock_fatal);
+	_Thread_queue_Acquire(&rw->reader_queue, &context->reader);
+	_Thread_queue_Enqueue(&rw->reader_queue.Queue,
+	    &_Thread_queue_Operations_FIFO, executing, &context->reader);
+}
+
+void
+rtems_bsd_rwlock_runlock_more(rtems_bsd_rwlock *rw,
+    rtems_bsd_rwlock_context *context)
+{
+
+	if (!_Thread_queue_Is_empty(&rw->writer_queue.Queue)) {
+		BSD_ASSERT(rw->readers == 0);
+
+		_Thread_queue_Surrender(&rw->writer_queue.Queue,
+		    rw->writer_queue.Queue.heads, NULL, &context->writer,
+		    &_Thread_queue_Operations_priority);
+	} else {
+		BSD_ASSERT(!_Thread_queue_Is_empty(&rw->reader_queue.Queue));
+		rtems_bsd_rwlock_ready_waiting_readers(rw, context);
+	}
+}
+
+void
+rtems_bsd_rwlock_ready_waiting_readers(rtems_bsd_rwlock *rw,
+    rtems_bsd_rwlock_context *context)
+{
+
+	_Thread_queue_Context_initialize(&context->reader);
+	_Thread_queue_Acquire(&rw->reader_queue, &context->reader);
+	_Thread_queue_Flush_critical(&rw->reader_queue.Queue,
+	    &_Thread_queue_Operations_FIFO,
+	    rtems_bsd_rwlock_flush_reader_filter,
+	    rtems_bsd_rwlock_flush_reader_post_release,
+	    &context->reader);
+}