Add some new functions for lock objects:

mutex_obj_refcnt(), mutex_obj_tryalloc()
rw_obj_refcnt(), rw_obj_tryalloc()

sys/kern/kern_mutex_obj.c

@@ -1,7 +1,7 @@
-/*	$NetBSD: kern_mutex_obj.c,v 1.6 2018/02/05 04:25:04 ozaki-r Exp $	*/
+/*	$NetBSD: kern_mutex_obj.c,v 1.7 2020/01/01 21:34:39 ad Exp $	*/
 
 /*-
- * Copyright (c) 2008 The NetBSD Foundation, Inc.
+ * Copyright (c) 2008, 2019 The NetBSD Foundation, Inc.
  * All rights reserved.
  *
  * This code is derived from software contributed to The NetBSD Foundation
@@ -30,7 +30,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_mutex_obj.c,v 1.6 2018/02/05 04:25:04 ozaki-r Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_mutex_obj.c,v 1.7 2020/01/01 21:34:39 ad Exp $");
 
 #include <sys/param.h>
 #include <sys/atomic.h>
@@ -81,7 +81,7 @@ mutex_obj_ctor(void *arg, void *obj, int flags)
 /*
  * mutex_obj_alloc:
  *
- *	Allocate a single lock object.
+ *	Allocate a single lock object, waiting for memory if needed.
  */
 kmutex_t *
 mutex_obj_alloc(kmutex_type_t type, int ipl)
@@ -97,6 +97,27 @@ mutex_obj_alloc(kmutex_type_t type, int ipl)
 	return (kmutex_t *)mo;
 }
 
+/*
+ * mutex_obj_alloc:
+ *
+ *	Allocate a single lock object, failing if no memory available.
+ */
+kmutex_t *
+mutex_obj_tryalloc(kmutex_type_t type, int ipl)
+{
+	struct kmutexobj *mo;
+	extern void _mutex_init(kmutex_t *, kmutex_type_t, int, uintptr_t);
+
+	mo = pool_cache_get(mutex_obj_cache, PR_NOWAIT);
+	if (__predict_true(mo != NULL)) {
+		_mutex_init(&mo->mo_lock, type, ipl,
+		    (uintptr_t)__builtin_return_address(0));
+		mo->mo_refcnt = 1;
+	}
+
+	return (kmutex_t *)mo;
+}
+
 /*
  * mutex_obj_hold:
  *
@@ -143,3 +164,16 @@ mutex_obj_free(kmutex_t *lock)
 	pool_cache_put(mutex_obj_cache, mo);
 	return true;
 }
+
+/*
+ * mutex_obj_refcnt:
+ *
+ *	Return the reference count on a lock object.
+ */
+u_int
+mutex_obj_refcnt(kmutex_t *lock)
+{
+	struct kmutexobj *mo = (struct kmutexobj *)lock;
+
+	return mo->mo_refcnt;
+}

sys/kern/kern_rwlock_obj.c

@@ -1,7 +1,7 @@
-/*	$NetBSD: kern_rwlock_obj.c,v 1.4 2018/02/05 04:25:04 ozaki-r Exp $	*/
+/*	$NetBSD: kern_rwlock_obj.c,v 1.5 2020/01/01 21:34:39 ad Exp $	*/
 
 /*-
- * Copyright (c) 2008, 2009 The NetBSD Foundation, Inc.
+ * Copyright (c) 2008, 2009, 2019 The NetBSD Foundation, Inc.
  * All rights reserved.
  *
  * This code is derived from software contributed to The NetBSD Foundation
@@ -30,7 +30,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_rwlock_obj.c,v 1.4 2018/02/05 04:25:04 ozaki-r Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_rwlock_obj.c,v 1.5 2020/01/01 21:34:39 ad Exp $");
 
 #include <sys/param.h>
 #include <sys/atomic.h>
@@ -81,7 +81,7 @@ rw_obj_ctor(void *arg, void *obj, int flags)
 /*
  * rw_obj_alloc:
  *
- *	Allocate a single lock object.
+ *	Allocate a single lock object, waiting for memory if needed.
  */
 krwlock_t *
 rw_obj_alloc(void)
@@ -96,6 +96,26 @@ rw_obj_alloc(void)
 	return (krwlock_t *)ro;
 }
 
+/*
+ * rw_obj_tryalloc:
+ *
+ *	Allocate a single lock object, but fail if no memory is available.
+ */
+krwlock_t *
+rw_obj_tryalloc(void)
+{
+	struct krwobj *ro;
+	extern void _rw_init(krwlock_t *, uintptr_t);
+
+	ro = pool_cache_get(rw_obj_cache, PR_NOWAIT);
+	if (__predict_true(ro != NULL)) {
+		_rw_init(&ro->ro_lock, (uintptr_t)__builtin_return_address(0));
+		ro->ro_refcnt = 1;
+	}
+
+	return (krwlock_t *)ro;
+}
+
 /*
  * rw_obj_hold:
  *
@@ -134,3 +154,16 @@ rw_obj_free(krwlock_t *lock)
 	pool_cache_put(rw_obj_cache, ro);
 	return true;
 }
+
+/*
+ * rw_obj_refcnt:
+ *
+ *	Return the reference count for a lock object.
+ */
+u_int
+rw_obj_refcnt(krwlock_t *lock)
+{
+	struct krwobj *ro = (struct krwobj *)lock;
+
+	return ro->ro_refcnt;
+}

sys/sys/mutex.h

@@ -1,4 +1,4 @@
-/*	$NetBSD: mutex.h,v 1.24 2019/12/09 21:08:56 ad Exp $	*/
+/*	$NetBSD: mutex.h,v 1.25 2020/01/01 21:34:39 ad Exp $	*/
 
 /*-
  * Copyright (c) 2002, 2006, 2007, 2008, 2009, 2019 The NetBSD Foundation, Inc.
@@ -205,6 +205,8 @@ void	mutex_obj_init(void);
 kmutex_t *mutex_obj_alloc(kmutex_type_t, int);
 void	mutex_obj_hold(kmutex_t *);
 bool	mutex_obj_free(kmutex_t *);
+u_int	mutex_obj_refcnt(kmutex_t *);
+kmutex_t *mutex_obj_tryalloc(kmutex_type_t, int);
 
 #endif /* _KERNEL */
 

sys/sys/rwlock.h

@@ -1,7 +1,7 @@
-/*	$NetBSD: rwlock.h,v 1.11 2019/11/29 20:04:54 riastradh Exp $	*/
+/*	$NetBSD: rwlock.h,v 1.12 2020/01/01 21:34:39 ad Exp $	*/
 
 /*-
- * Copyright (c) 2002, 2006, 2007, 2008 The NetBSD Foundation, Inc.
+ * Copyright (c) 2002, 2006, 2007, 2008, 2019 The NetBSD Foundation, Inc.
  * All rights reserved.
  *
  * This code is derived from software contributed to The NetBSD Foundation
@@ -117,6 +117,8 @@ void	rw_obj_init(void);
 krwlock_t *rw_obj_alloc(void);
 void	rw_obj_hold(krwlock_t *);
 bool	rw_obj_free(krwlock_t *);
+u_int	rw_obj_refcnt(krwlock_t *);
+krwlock_t *rw_obj_tryalloc(void);
 
 #endif	/* _KERNEL */