Index: sys/net/mp_ring.c
===================================================================
--- sys/net/mp_ring.c
+++ sys/net/mp_ring.c
@@ -435,8 +435,10 @@
 	 * pidx_tail reaches the beginning of our reservation (pidx_start).
 	 */
 	while (ns.pidx_tail != pidx_start) {
+		critical_exit();
 		cpu_spinwait();
 		ns.state = r->state;
+		critical_enter();
 	}
 
 	/* Now it is our turn to fill up the area we reserved earlier. */