Index: if_vmx.c
===================================================================
RCS file: /cvs/src/sys/dev/pci/if_vmx.c,v
retrieving revision 1.50
diff -u -p -r1.50 if_vmx.c
--- if_vmx.c	6 Aug 2019 10:54:40 -0000	1.50
+++ if_vmx.c	22 Oct 2019 08:06:43 -0000
@@ -71,6 +71,7 @@ struct vmxnet3_rxring {
 	bus_dmamap_t dmap[NRXDESC];
 	struct if_rxring rxr;
 	struct timeout refill;
+	struct mutex mtx;
 	struct vmxnet3_rxdesc *rxd;
 	u_int fill;
 	u_int8_t gen;
@@ -460,6 +461,7 @@ vmxnet3_alloc_rxring(struct vmxnet3_soft
 		ring = &rq->cmd_ring[i];
 		ring->sc = sc;
 		ring->rid = i;
+		mtx_init(&ring->mtx, IPL_NET);
 		timeout_set(&ring->refill, vmxnet3_rxfill, ring);
 		for (idx = 0; idx < NRXDESC; idx++) {
 			if (bus_dmamap_create(sc->sc_dmat, JUMBO_LEN, 1,
@@ -506,6 +508,9 @@ vmxnet3_rxfill(void *arg)
 	struct vmxnet3_softc *sc = ring->sc;
 	u_int slots;
 
+	if (!mtx_enter_try(&ring->mtx))
+		return;
+
 	for (slots = if_rxr_get(&ring->rxr, NRXDESC); slots > 0; slots--) {
 		if (vmxnet3_getbuf(sc, ring))
 			break;
@@ -514,6 +519,8 @@ vmxnet3_rxfill(void *arg)
 
 	if (if_rxr_inuse(&ring->rxr) == 0)
 		timeout_add(&ring->refill, 1);
+
+	mtx_leave(&ring->mtx);
 }
 
 void