Index: sys/kern/kern_umtx.c
===================================================================
--- sys/kern/kern_umtx.c
+++ sys/kern/kern_umtx.c
@@ -558,6 +558,32 @@
 	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, uint32_t bitset)
+{
+	struct umtxq_queue *uh;
+	struct umtx_q *uq, *uq_temp;
+	int ret;
+
+	ret = 0;
+	UMTXQ_LOCKED_ASSERT(umtxq_getchain(key));
+	uh = umtxq_queue_lookup(key, UMTX_SHARED_QUEUE);
+	if (uh == NULL)
+		return (0);
+	TAILQ_FOREACH_SAFE(uq, &uh->head, uq_link, uq_temp) {
+		if ((uq->uq_bitset & bitset) == 0)
+			continue;
+		umtxq_remove_queue(uq, UMTX_SHARED_QUEUE);
+		wakeup_one(uq);
+		if (++ret >= n_wake)
+			break;
+	}
+	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 */
+	uint32_t		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, uint32_t);
 int umtxq_sleep(struct umtx_q *, const char *,
     struct umtx_abs_timeout *);
 void umtxq_unbusy(struct umtx_key *);