Index: sys/kern/subr_smr.c
===================================================================
--- sys/kern/subr_smr.c
+++ sys/kern/subr_smr.c
@@ -487,6 +487,8 @@
 	/*
 	 * It is illegal to enter while in an smr section.
 	 */
+	KASSERT(goal != SMR_SEQ_INVALID,
+	    ("smr_poll: Invalid sequence number."));
 	KASSERT(!wait || !SMR_ENTERED(smr),
 	    ("smr_poll: Blocking not allowed in a SMR section."));
 	KASSERT(!wait || (zpcpu_get(smr)->c_flags & SMR_LAZY) == 0,
Index: sys/vm/uma_core.c
===================================================================
--- sys/vm/uma_core.c
+++ sys/vm/uma_core.c
@@ -668,6 +668,7 @@
 {
 	uma_bucket_t bucket;
 	int i;
+	smr_seq_t seq;
 	bool dtor = false;
 
 	ZDOM_LOCK_ASSERT(zdom);
@@ -683,7 +684,10 @@
 		bucket->ub_seq = SMR_SEQ_INVALID;
 		dtor = (zone->uz_dtor != NULL) || UMA_ALWAYS_CTORDTOR;
 		if (STAILQ_NEXT(bucket, ub_link) != NULL)
-			zdom->uzd_seq = STAILQ_NEXT(bucket, ub_link)->ub_seq;
+			seq = STAILQ_NEXT(bucket, ub_link)->ub_seq;
+		else
+			seq = SMR_SEQ_INVALID;
+		atomic_store_32(&zdom->uzd_seq, seq);
 	}
 	MPASS(zdom->uzd_nitems >= bucket->ub_cnt);
 	STAILQ_REMOVE_HEAD(&zdom->uzd_buckets, ub_link);
@@ -732,7 +736,7 @@
 		if (ws)
 			zone_domain_imax_set(zdom, zdom->uzd_nitems);
 		if (STAILQ_EMPTY(&zdom->uzd_buckets))
-			zdom->uzd_seq = bucket->ub_seq;
+			atomic_store_32(&zdom->uzd_seq, bucket->ub_seq);
 		STAILQ_INSERT_TAIL(&zdom->uzd_buckets, bucket, ub_link);
 		ZDOM_UNLOCK(zdom);
 		return;
@@ -890,6 +894,7 @@
 {
 	uma_zone_domain_t zdom;
 	uma_bucket_t bucket;
+	smr_seq_t seq;
 
 	/*
 	 * Avoid the lock if possible.
@@ -898,9 +903,12 @@
 	if (zdom->uzd_nitems == 0)
 		return (NULL);
 
-	if ((cache_uz_flags(cache) & UMA_ZONE_SMR) != 0 &&
-	    !smr_poll(zone->uz_smr, zdom->uzd_seq, false))
-		return (NULL);
+	if ((cache_uz_flags(cache) & UMA_ZONE_SMR) != 0) {
+		seq = atomic_load_32(&zdom->uzd_seq);
+		if (seq != SMR_SEQ_INVALID &&
+		    !smr_poll(zone->uz_smr, seq, false))
+			return (NULL);
+	}
 
 	/*
 	 * Check the zone's cache of buckets.
@@ -2570,6 +2578,7 @@
 		zdom = ZDOM_GET(zone, i);
 		ZDOM_LOCK_INIT(zone, zdom, (arg->flags & UMA_ZONE_MTXCLASS));
 		STAILQ_INIT(&zdom->uzd_buckets);
+		zdom->uzd_seq = SMR_SEQ_INVALID;
 	}
 
 #ifdef INVARIANTS