Index: sys/vm/vm_swapout.c
===================================================================
--- sys/vm/vm_swapout.c
+++ sys/vm/vm_swapout.c
@@ -159,6 +159,7 @@
 MTX_SYSINIT(vm_daemon, &vm_daemon_mtx, "vm daemon", MTX_DEF);
 
 static int swapped_cnt;
+static int swap_inprogress;	/* Current swap-ins done outside swapper. */
 
 static void swapclear(struct proc *);
 static int swapout(struct proc *);
@@ -634,6 +635,8 @@
 		sx_xlock(&allproc_lock);
 		MPASS(swapped_cnt > 0);
 		swapped_cnt--;
+		if (curthread != &thread0)
+			swap_inprogress++;
 		sx_xunlock(&allproc_lock);
 
 		/*
@@ -644,6 +647,12 @@
 		FOREACH_THREAD_IN_PROC(p, td)
 			vm_thread_swapin(td, oom_alloc);
 
+		if (curthread != &thread0) {
+			sx_xlock(&allproc_lock);
+			MPASS(swap_inprogress > 0);
+			swap_inprogress--;
+			sx_xunlock(&allproc_lock);
+		}
 		PROC_LOCK(p);
 		swapclear(p);
 		p->p_swtick = ticks;
@@ -721,6 +730,8 @@
 		}
 		PROC_UNLOCK(p);
 	}
+	if (swap_inprogress > 0)
+		res = NULL;
 	if (res != NULL)
 		PROC_LOCK(res);
 	return (res);