[src/trunk]: src/sys/net Fix a deadlock (rt_free vs. route_intr ...

[ozaki-r <ozaki-r%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/7dbbb20ec62a
branches:  trunk
changeset: 318460:7dbbb20ec62a
user:      ozaki-r <ozaki-r%NetBSD.org@localhost>
date:      Wed Apr 25 03:49:57 2018 +0000
description:
Fix a deadlock (rt_free vs. route_intr on rt_so_mtx)

It occurs only if NET_MPSAFE is enabled.

diffstat:

 sys/net/rtsock.c |  18 ++++++++++++++----
 1 files changed, 14 insertions(+), 4 deletions(-)

diffs (40 lines):

diff -r 9b417b7f664a -r 7dbbb20ec62a sys/net/rtsock.c
--- a/sys/net/rtsock.c  Wed Apr 25 03:45:21 2018 +0000
+++ b/sys/net/rtsock.c  Wed Apr 25 03:49:57 2018 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: rtsock.c,v 1.240 2018/04/12 04:38:13 ozaki-r Exp $     */
+/*     $NetBSD: rtsock.c,v 1.241 2018/04/25 03:49:57 ozaki-r Exp $     */
 
 /*
  * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
@@ -61,7 +61,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: rtsock.c,v 1.240 2018/04/12 04:38:13 ozaki-r Exp $");
+__KERNEL_RCSID(0, "$NetBSD: rtsock.c,v 1.241 2018/04/25 03:49:57 ozaki-r Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_inet.h"
@@ -928,9 +928,19 @@
        if (old_rtm != NULL)
                Free(old_rtm);
        if (rt) {
-               if (do_rt_free)
+               if (do_rt_free) {
+#ifdef NET_MPSAFE
+                       /*
+                        * Release rt_so_mtx to avoid a deadlock with
+                        * route_intr.
+                        */
+                       mutex_exit(rt_so_mtx);
                        rt_free(rt);
-               else
+                       mutex_enter(rt_so_mtx);
+#else
+                       rt_free(rt);
+#endif
+               } else
                        rt_unref(rt);
        }
     {