commit f9838f091f891ccdb51a1bb0c0e6f899f04affda
Author: Ryota Ozaki <ozaki-r@iij.ad.jp>
Date:   Tue Jul 25 13:48:58 2017 +0900

    localcount debug

diff --git a/sys/kern/subr_localcount.c b/sys/kern/subr_localcount.c
index 064d5407f07..30d51a8cbbf 100644
--- a/sys/kern/subr_localcount.c
+++ b/sys/kern/subr_localcount.c
@@ -209,6 +209,9 @@ localcount_acquire(struct localcount *lc)
 
 	KASSERT(lc->lc_totalp == NULL);
 	localcount_adjust(lc, +1);
+#ifdef LOCKDEBUG
+	atomic_inc_32(&lc->lc_refcnt);
+#endif
 }
 
 /*
@@ -253,5 +256,26 @@ localcount_release(struct localcount *lc, kcondvar_t *cv, kmutex_t *interlock)
 	}
 
 	localcount_adjust(lc, -1);
+#ifdef LOCKDEBUG
+	if ((int32_t)atomic_dec_32_nv(&lc->lc_refcnt) < 0)
+		panic("counter underflow");
+#endif
  out:	kpreempt_enable();
 }
+
+/*
+ * localcount_debug_refcnt(lc)
+ *
+ *	Return a total reference count of lc.  It returns a correct value
+ *	only if LOCKDEBUG enabled.  Otherwise always return 0.
+ */
+int32_t
+localcount_debug_refcnt(const struct localcount *lc)
+{
+
+#ifdef LOCKDEBUG
+	return (int32_t)lc->lc_refcnt;
+#else
+	return 0;
+#endif
+}
diff --git a/sys/sys/localcount.h b/sys/sys/localcount.h
index 6a301197e95..5de28bf516b 100644
--- a/sys/sys/localcount.h
+++ b/sys/sys/localcount.h
@@ -37,6 +37,9 @@
 #endif
 
 #include <sys/types.h>
+#ifdef LOCKDEBUG
+#include <sys/atomic.h>
+#endif
 
 struct kcondvar;
 struct kmutex;
@@ -45,6 +48,9 @@ struct percpu;
 struct localcount {
 	int64_t		*lc_totalp;
 	struct percpu	*lc_percpu; /* int64_t */
+#ifdef LOCKDEBUG
+	uint32_t	lc_refcnt;
+#endif
 };
 
 void	localcount_init(struct localcount *);
@@ -55,4 +61,6 @@ void	localcount_acquire(struct localcount *);
 void	localcount_release(struct localcount *, struct kcondvar *,
 	    struct kmutex *);
 
+int32_t	localcount_debug_refcnt(const struct localcount *);
+
 #endif	/* _SYS_LOCALCOUNT_H */