From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hannes Frederic Sowa Subject: Re: [PATCH net] ipv6: fix RTNL assert fail in DAD Date: Tue, 18 Mar 2014 01:29:08 +0100 Message-ID: <20140318002908.GF12291@order.stressinduktion.org> References: <20140317161853.2e880469@nehalam.linuxnetplumber.net> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Cc: David Miller , netdev@vger.kernel.org To: Stephen Hemminger Return-path: Received: from order.stressinduktion.org ([87.106.68.36]:42245 "EHLO order.stressinduktion.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752042AbaCRA3K (ORCPT ); Mon, 17 Mar 2014 20:29:10 -0400 Content-Disposition: inline In-Reply-To: <20140317161853.2e880469@nehalam.linuxnetplumber.net> Sender: netdev-owner@vger.kernel.org List-ID: Hi! On Mon, Mar 17, 2014 at 04:18:53PM -0700, Stephen Hemminger wrote: > IPv6 duplicate address detection is triggering the following assertion > failure when using macvlan + vif + multicast. > RTNL: assertion failed at net/core/dev.c (4496) > > This happens because the DAD timer is adding a multicast address without > acquiring the RTNL mutex. In order to acquire the RTNL mutex, it must be > done in process context; therefore it must be in a workqueue. > > Full backtrace: > [ 541.030090] RTNL: assertion failed at net/core/dev.c (4496) > [ 541.031143] CPU: 0 PID: 0 Comm: swapper/0 Tainted: G O 3.10.33-1-amd64-vyatta #1 > [ 541.031145] Hardware name: Bochs Bochs, BIOS Bochs 01/01/2007 > [ 541.031146] ffffffff8148a9f0 000000000000002f ffffffff813c98c1 ffff88007c4451f8 > [ 541.031148] 0000000000000000 0000000000000000 ffffffff813d3540 ffff88007fc03d18 > [ 541.031150] 0000880000000006 ffff88007c445000 ffffffffa0194160 0000000000000000 > [ 541.031152] Call Trace: > [ 541.031153] [] ? dump_stack+0xd/0x17 > [ 541.031180] [] ? __dev_set_promiscuity+0x101/0x180 > [ 541.031183] [] ? __hw_addr_create_ex+0x60/0xc0 > [ 541.031185] [] ? __dev_set_rx_mode+0xaa/0xc0 > [ 541.031189] [] ? __dev_mc_add+0x61/0x90 > [ 541.031198] [] ? igmp6_group_added+0xfc/0x1a0 [ipv6] > [ 541.031208] [] ? kmem_cache_alloc+0xcb/0xd0 > [ 541.031212] [] ? ipv6_dev_mc_inc+0x267/0x300 [ipv6] > [ 541.031216] [] ? addrconf_join_solict+0x2e/0x40 [ipv6] > [ 541.031219] [] ? ipv6_dev_ac_inc+0x159/0x1f0 [ipv6] > [ 541.031223] [] ? addrconf_join_anycast+0x92/0xa0 [ipv6] > [ 541.031226] [] ? __ipv6_ifa_notify+0x11e/0x1e0 [ipv6] > [ 541.031229] [] ? ipv6_ifa_notify+0x33/0x50 [ipv6] This is the most often case but I fear there are more of them. addrconf_verify seems unsafe, too, when removing the last ipv6 address. So does addrconf_prefix_rcv if adding first address. I wonder if we should put the whole ipv6_ifa_notify infrastructure in a workqueue? I don't like that either and it could add subtile races. Those races also seem possible if we only defer addrconf_join_solict, addrconf_leave_solict, addrconf_join_anycast and addrconf_leave_anycast to workqueues. This change is certainly going into the right direction but I am not sure if we could generalize it. Greetings, Hannes