From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: open sockets preventing unregister_netdevice from completing in linux-next (next-20120724) Date: Thu, 26 Jul 2012 14:10:47 -0700 (PDT) Message-ID: <20120726.141047.1871303031596778701.davem@davemloft.net> References: <1343227128.2626.11157.camel@edumazet-glaptop> <20120725.151737.1807149851147342859.davem@davemloft.net> <1343322928.2626.11764.camel@edumazet-glaptop> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: bjorn@mork.no, netdev@vger.kernel.org To: eric.dumazet@gmail.com Return-path: Received: from shards.monkeyblade.net ([149.20.54.216]:55913 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752412Ab2GZVKx (ORCPT ); Thu, 26 Jul 2012 17:10:53 -0400 In-Reply-To: <1343322928.2626.11764.camel@edumazet-glaptop> Sender: netdev-owner@vger.kernel.org List-ID: From: Eric Dumazet Date: Thu, 26 Jul 2012 19:15:28 +0200 > On Wed, 2012-07-25 at 15:17 -0700, David Miller wrote: >> From: Eric Dumazet >> Date: Wed, 25 Jul 2012 16:38:48 +0200 >> >> > Yes, we miss what was done with rt_cache_flush() : find all cached >> > routes and release all dev references... >> >> We can fix this with a two-pronged approach: >> >> 1) Walk the FIB info nexthops and invalidate. >> >> 2) Entries not cached in the FIB info nexthops go into a >> per-netns list which is scanned as well. >> >> I'll try to work on this if nobody beats me to it. > > With your latest patch, I can "rmmod tg3" while sockets are active. > > Not sure we need all this now ? > > (the trick is probably in fib_semantics.c, when you changed > dst_release() to dst_free()) That's not the problem. Not all routes are cached in the FIB nexthop. Any route that doesn't resolve to a FIB info (255.255.255.255, etc.) or uses special features (tclassid, etc.) doesn't get cached. Therefore if a socket gets that kind of route, and then becomes inactive, we can hold onto the device references forever. The entity with the route has to call dst_ops->check() to see that the route has become invalid, but if the application is inactive, that will never happen. We have to put such non-cached routes into a special list or table of some kind, so that we can zap a netdevice if it wants to go down or unload before the final dst_release() happens.