Handle recursive panic inside vt(4)

vt_core.patch

diff --git a/sys/dev/vt/vt_core.c b/sys/dev/vt/vt_core.c
index 267dd7bf2489..1a7a752d9a07 100644
--- a/sys/dev/vt/vt_core.c
+++ b/sys/dev/vt/vt_core.c
@@ -276,6 +276,8 @@ SYSINIT(vt_update_static, SI_SUB_KMEM, SI_ORDER_ANY, vt_update_static,
 SYSINIT(vt_early_cons, SI_SUB_INT_CONFIG_HOOKS, SI_ORDER_ANY, vt_upgrade,
     &vt_consdev);
 
+static bool inside_vtterm_done_in_panic = false;
+
 /* Initialize locks/mem depended members. */
 static void
 vt_update_static(void *dummy)
@@ -1464,7 +1466,13 @@ vtterm_done(struct terminal *tm)
 	struct vt_window *vw = tm->tm_softc;
 	struct vt_device *vd = vw->vw_device;
 
+	if (inside_vtterm_done_in_panic) {
+		return;
+	}
+
 	if (kdb_active || KERNEL_PANICKED()) {
+		inside_vtterm_done_in_panic = true;
+
 		/* Switch to the debugger. */
 		if (vd->vd_curwindow != vw) {
 			vd->vd_curwindow = vw;
@@ -1473,7 +1481,12 @@ vtterm_done(struct terminal *tm)
 				vd->vd_driver->vd_postswitch(vd);
 		}
 		vd->vd_flags &= ~VDF_SPLASH;
+
+		panic("vt");
+
 		vt_flush(vd);
+
+		inside_vtterm_done_in_panic = false;
 	} else if (!(vd->vd_flags & VDF_ASYNC)) {
 		vt_flush(vd);
 	}