From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Denis V. Lunev" Subject: Re: cleanup in workq and dst_destroy Date: Fri, 16 Nov 2007 20:06:30 +0300 Message-ID: <473DCE16.8020809@sw.ru> References: <473DC604.9070601@fr.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <473DC604.9070601-NmTC/0ZBporQT0dZR+AlfA@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org Errors-To: containers-bounces-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org To: Daniel Lezcano Cc: Linux Containers , "Denis V. Lunev" , Benjamin Thery , "Eric W. Biederman" , Pavel Emelianov List-Id: containers.vger.kernel.org Daniel Lezcano wrote: > Hi all, > > while doing ipv6 namespace, we were faced to a problem with the loopback > and the dst_destroy function. > > When the network namespace exits, the cleanup function is called by > schedule_work and this function will browse the net ops list to call the > different exit methods for the registered subsystems. > > The different subsystems will shutdown their resources and in particular > addrconf subsystem will ifdown the loopback. This function will call > rt6_ifdown > -> fib6_clean_all > -> fib6_clean_node > -> fib6_clean_tree > -> fib6_clean_node > -> fib6_del > -> fib6_del_route > -> rt6_release > ->dst_free > -> __dst_free > > The __dst_free function will schedule_delayed_work the dst_gc_work > function. > > The dst_gc_work will call dst_destroy and finally this one will call > dst->ops->destroy ops function which is ip6_dst_destroy. > > The problem here is we have the workq blocked because we are running > inside the netns cleanup function. So the delayed work will not run > until we exits the cleanup function. But the loopback is still > referenced by the ip6 routes, the netdev_unregister will loop > indefinitly => dead lock. > > By the way, this bug appears with ipv6 but it is perhaps pending with ipv4. > > Benjamin as proposed to create a separate workq for the network > namespace, so in the worst case we have the unregister looping until the > ip6 route are shut downed. Is it an acceptable solution ? > we are doing this staff in the special thread. There are a lot of difficult things to perform like synchronize_net & netdev_run_todo inside Regards, Den