Index: sys/kern/subr_lock.c
===================================================================
--- sys/kern/subr_lock.c
+++ sys/kern/subr_lock.c
@@ -50,6 +50,7 @@
 #include <sys/sched.h>
 #include <sys/smp.h>
 #include <sys/sysctl.h>
+#include <sys/turnstile.h>
 
 #ifdef DDB
 #include <ddb/ddb.h>
@@ -93,6 +94,7 @@
 	/* Initialize the lock object. */
 	lock->lo_name = name;
 	lock->lo_flags |= flags | LO_INITIALIZED;
+	lock->lo_refcount = 0;
 	LOCK_LOG_INIT(lock, 0);
 	WITNESS_INIT(lock, (type != NULL) ? type : name);
 }
@@ -102,11 +104,58 @@
 {
 
 	KASSERT(lock_initialized(lock), ("lock %p is not initialized", lock));
+	KASSERT(lock->lo_refcount == 0, ("lock %p refcount is not zero", lock));
 	WITNESS_DESTROY(lock);
 	LOCK_LOG_DESTROY(lock, 0);
 	lock->lo_flags &= ~LO_INITIALIZED;
 }
 
+void
+lock_ref(struct lock_object *lock)
+{
+
+	atomic_add_32(&lock->lo_refcount, 1);
+}
+
+void
+lock_unref(struct lock_object *lock)
+{
+	volatile u_int *pref = &lock->lo_refcount;
+	struct turnstile *ts;
+
+	MPASS(*pref != 0);
+
+	if (atomic_fetchadd_32(pref, -1U) != 1)
+		return;
+	turnstile_chain_lock(lock);
+	ts = turnstile_lookup(lock);
+	MPASS(ts != NULL);
+	turnstile_broadcast(ts, TS_EXCLUSIVE_QUEUE);
+	turnstile_unpend(ts);
+	turnstile_chain_unlock(lock);
+}
+
+void
+lock_unref_and_wait(struct lock_object *lock)
+{
+	volatile u_int *pref = &lock->lo_refcount;
+	struct turnstile *ts;
+
+	MPASS(*pref != 0);
+
+	if (atomic_fetchadd_32(pref, -1U) == 1)
+		return;
+
+	while (1) {
+		ts = turnstile_trywait(lock);
+		if (*pref == 0) {
+			turnstile_cancel(ts);
+			break;
+		}
+		turnstile_wait(ts, NULL, TS_EXCLUSIVE_QUEUE);
+	}
+}
+
 static SYSCTL_NODE(_debug, OID_AUTO, lock, CTLFLAG_RD, NULL, "lock debugging");
 static SYSCTL_NODE(_debug_lock, OID_AUTO, delay, CTLFLAG_RD, NULL,
     "lock delay");
Index: sys/sys/_lock.h
===================================================================
--- sys/sys/_lock.h
+++ sys/sys/_lock.h
@@ -38,6 +38,7 @@
 	u_int	lo_flags;
 	u_int	lo_data;		/* General class specific data. */
 	struct	witness *lo_witness;	/* Data for witness. */
+	u_int	lo_refcount;		/* Lock refcount */
 };
 
 #ifdef _KERNEL
Index: sys/sys/lock.h
===================================================================
--- sys/sys/lock.h
+++ sys/sys/lock.h
@@ -219,6 +219,9 @@
 void	lock_destroy(struct lock_object *);
 void	lock_delay(struct lock_delay_arg *);
 void	lock_delay_default_init(struct lock_delay_config *);
+void	lock_ref(struct lock_object *);
+void	lock_unref(struct lock_object *);
+void	lock_unref_and_wait(struct lock_object *);
 void	spinlock_enter(void);
 void	spinlock_exit(void);
 void	witness_init(struct lock_object *, const char *);