Index: sys/kern/subr_smr.c
===================================================================
--- sys/kern/subr_smr.c
+++ sys/kern/subr_smr.c
@@ -275,7 +275,7 @@
 		c = zpcpu_get_cpu(smr, i);
 		c_seq = SMR_SEQ_INVALID;
 		for (;;) {
-			c_seq = atomic_load_int(&c->c_seq);
+			c_seq = atomic_load_acq_int(&c->c_seq);
 			if (c_seq == SMR_SEQ_INVALID)
 				break;
 
@@ -323,6 +323,8 @@
 		if (c_seq != SMR_SEQ_INVALID && SMR_SEQ_GT(rd_seq, c_seq))
 			rd_seq = c_seq;
 	}
+	/* Same semantic for reads of c->c_seq above as in smr_enter(). */
+	atomic_thread_fence_acq();
 
 	/*
 	 * Advance the rd_seq as long as we observed the most recent one.
@@ -331,6 +333,7 @@
 	do {
 		if (SMR_SEQ_LEQ(rd_seq, s_rd_seq))
 			break;
+		atomic_thread_fence_rel();
 	} while (atomic_fcmpset_int(&s->s_rd_seq, &s_rd_seq, rd_seq) == 0);
 
 out: