commit d61eacede41f7e23b141c6f882f2efe63847a4c0
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..a132e6c7566 100644
--- a/sys/kern/subr_localcount.c
+++ b/sys/kern/subr_localcount.c
@@ -253,5 +253,36 @@ localcount_release(struct localcount *lc, kcondvar_t *cv, kmutex_t *interlock)
 	}
 
 	localcount_adjust(lc, -1);
+	KDASSERT(localcount_debug_refcnt(lc) >= 0);
  out:	kpreempt_enable();
 }
+
+static void
+localcount_debug_refcnt_cb(void *p, void *arg, struct cpu_info *ci __unused)
+{
+	int64_t *localp = p;
+	int64_t *total = arg;
+
+	*total += *localp;
+}
+
+/*
+ * localcount_debug_refcnt(lc)
+ *
+ *	Return a total reference count of lc.  It should be used only
+ *	for debugging purposes because the result isn't guaranteed to
+ *	be accurate and stable.
+ *
+ *	Can sleep.
+ */
+int64_t
+localcount_debug_refcnt(struct localcount *lc)
+{
+	int64_t total = 0;
+
+	ASSERT_SLEEPABLE();
+
+	percpu_foreach(lc->lc_percpu, localcount_debug_refcnt_cb, &total);
+
+	return total;
+}
diff --git a/sys/sys/localcount.h b/sys/sys/localcount.h
index 6a301197e95..a15eb4a315d 100644
--- a/sys/sys/localcount.h
+++ b/sys/sys/localcount.h
@@ -55,4 +55,6 @@ void	localcount_acquire(struct localcount *);
 void	localcount_release(struct localcount *, struct kcondvar *,
 	    struct kmutex *);
 
+int64_t	localcount_debug_refcnt(struct localcount *);
+
 #endif	/* _SYS_LOCALCOUNT_H */