Index: sys/kern/kern_umtx.c
===================================================================
--- sys/kern/kern_umtx.c
+++ sys/kern/kern_umtx.c
@@ -558,6 +558,31 @@
 	return (0);
 }
 
+/*
+ * Wake up threads waiting on an userland object by a bit mask.
+ */
+int
+umtxq_signal_mask(struct umtx_key *key, int n_wake, u_int bitset)
+{
+	struct umtxq_queue *uh;
+	struct umtx_q *uq;
+	int ret;
+
+	ret = 0;
+	UMTXQ_LOCKED_ASSERT(umtxq_getchain(key));
+	uh = umtxq_queue_lookup(key, UMTX_SHARED_QUEUE);
+	if (uh != NULL) {
+		while ((uq = TAILQ_FIRST(&uh->head)) != NULL &&
+		    (uq->uq_bitset & bitset) != 0) {
+			umtxq_remove_queue(uq, UMTX_SHARED_QUEUE);
+			wakeup_one(uq);
+			if (++ret >= n_wake)
+				return (ret);
+		}
+	}
+	return (ret);
+}
+
 /*
  * Wake up threads waiting on an userland object.
  */
Index: sys/sys/umtxvar.h
===================================================================
--- sys/sys/umtxvar.h
+++ sys/sys/umtxvar.h
@@ -120,6 +120,9 @@
 	int			uq_flags;
 #define UQF_UMTXQ	0x0001
 
+	/* Futex bitset mask */
+	u_int			uq_bitset;
+
 	/* The thread waits on. */
 	struct thread		*uq_thread;
 
@@ -207,6 +210,7 @@
 struct umtxq_chain *umtxq_getchain(struct umtx_key *);
 void umtxq_insert_queue(struct umtx_q *, int);
 void umtxq_remove_queue(struct umtx_q *, int);
+int umtxq_signal_mask(struct umtx_key *, int, u_int);
 int umtxq_sleep(struct umtx_q *, const char *,
     struct umtx_abs_timeout *);
 void umtxq_unbusy(struct umtx_key *);