Do not try to grab the NET_LOCK() while holding an ifp reference.

Fix a deadlock with a thread trying to detach the corresponding interface.

ok sashan@, bluhm@

diff --git a/sys/net/if.c b/sys/net/if.c
index 8532743..d519ddc 100644 (file)
--- a/sys/net/if.c
+++ b/sys/net/if.c
@@ -1,4 +1,4 @@
-/*     $OpenBSD: if.c,v 1.499 2017/05/28 12:51:33 yasuoka Exp $        */
+/*     $OpenBSD: if.c,v 1.500 2017/05/29 06:08:21 mpi Exp $    */
 /*     $NetBSD: if.c,v 1.35 1996/05/07 05:26:04 thorpej Exp $  */
 
 /*
@@ -1559,15 +1559,14 @@ if_linkstate_task(void *xifidx)
        struct ifnet *ifp;
        int s;
 
-       ifp = if_get(ifidx);
-       if (ifp == NULL)
-               return;
-
        NET_LOCK(s);
-       if_linkstate(ifp);
-       NET_UNLOCK(s);
 
+       ifp = if_get(ifidx);
+       if (ifp != NULL)
+               if_linkstate(ifp);
        if_put(ifp);
+
+       NET_UNLOCK(s);
 }
 
 void