[src/trunk]: src/sys/net Release rt_so_mtx on updating a rtentry to avoid a d...

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

details:   https://anonhg.NetBSD.org/src/rev/e57138958c29
branches:  trunk
changeset: 358835:e57138958c29
user:      ozaki-r <ozaki-r%NetBSD.org@localhost>
date:      Fri Jan 19 05:19:29 2018 +0000

description:
Release rt_so_mtx on updating a rtentry to avoid a deadlock with route_intr

The deadlock happened only if NET_MPSAFE on.

diffstat:

 sys/net/rtsock.c |  26 ++++++++++++++++++++++++--
 1 files changed, 24 insertions(+), 2 deletions(-)

diffs (73 lines):

diff -r 4355db7f93fd -r e57138958c29 sys/net/rtsock.c
--- a/sys/net/rtsock.c  Thu Jan 18 23:17:09 2018 +0000
+++ b/sys/net/rtsock.c  Fri Jan 19 05:19:29 2018 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: rtsock.c,v 1.236 2017/12/18 05:35:36 ozaki-r Exp $     */
+/*     $NetBSD: rtsock.c,v 1.237 2018/01/19 05:19:29 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 1.236 2017/12/18 05:35:36 ozaki-r Exp $");
+__KERNEL_RCSID(0, "$NetBSD: rtsock.c,v 1.237 2018/01/19 05:19:29 ozaki-r Exp $");
 
 #ifdef _KERNEL_OPT
 #include "opt_inet.h"
@@ -82,6 +82,7 @@
 #include <sys/kauth.h>
 #include <sys/kmem.h>
 #include <sys/intr.h>
+#include <sys/condvar.h>
 
 #include <net/if.h>
 #include <net/if_llatbl.h>
@@ -187,6 +188,9 @@
 static struct rawcbhead rt_rawcb;
 #ifdef NET_MPSAFE
 static kmutex_t *rt_so_mtx;
+
+static bool rt_updating = false;
+static kcondvar_t rt_update_cv;
 #endif
 
 static void
@@ -1007,11 +1011,27 @@
 
                case RTM_CHANGE:
 #ifdef NET_MPSAFE
+                       /*
+                        * Release rt_so_mtx to avoid a deadlock with route_intr
+                        * and also serialize updating routes to avoid another.
+                        */
+                       while (rt_updating) {
+                               error = cv_wait_sig(&rt_update_cv, rt_so_mtx);
+                               if (error != 0)
+                                       goto flush;
+                       }
+                       rt_updating = true;
+                       mutex_exit(rt_so_mtx);
+
                        error = rt_update_prepare(rt);
                        if (error == 0) {
                                error = route_output_change(rt, &info, rtm);
                                rt_update_finish(rt);
                        }
+
+                       mutex_enter(rt_so_mtx);
+                       rt_updating = false;
+                       cv_broadcast(&rt_update_cv);
 #else
                        error = route_output_change(rt, &info, rtm);
 #endif
@@ -2110,6 +2130,8 @@
 #endif
 #ifdef NET_MPSAFE
        rt_so_mtx = mutex_obj_alloc(MUTEX_DEFAULT, IPL_NONE);
+
+       cv_init(&rt_update_cv, "rtsock_cv");
 #endif
 
        sysctl_net_route_setup(NULL);