netdev - Re: unregister_netdevice: waiting for lo to become free. Usage count = 8

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Message-Id: <201104182348.05228.hans@schillstrom.com>
Date:	Mon, 18 Apr 2011 23:48:04 +0200
From:	Hans Schillstrom <hans@...illstrom.com>
To:	Julian Anastasov <ja@....bg>
Cc:	Simon Horman <horms@...ge.net.au>, netdev@...r.kernel.org,
	lvs-devel@...r.kernel.org,
	"Eric W. Biederman" <ebiederm@...ssion.com>
Subject: Re: unregister_netdevice: waiting for lo to become free. Usage count = 8

On Monday, April 18, 2011 23:12:27 Julian Anastasov wrote:
> 
> 	Hello,
> 
> On Mon, 18 Apr 2011, Hans Schillstrom wrote:
> 
> > Actually I forgot to tell there is a need for a
> > ip_vs_service_cleanup() due to above.
> > Do you see any drawbacks with it ?
> 
> 	May be ip_vs_service_cleanup() should call only
> ip_vs_flush(), under __ip_vs_mutex.

Hmm,  
I'm not sure if the IP_VS_WAIT_WHILE() in ip_vs_flush is a good idea in this case...
That was why I wrote ip_vs_service_cleanup()

> 
> > /*
> >  *	Delete service by {netns} in the service table.
> >  */
> > static void ip_vs_service_cleanup(struct net *net)
> > {
> > 	unsigned hash;
> > 	struct ip_vs_service *svc, *tmp;
> > 
> > 	EnterFunction(2);
> > 	/* Check for "full" addressed entries */
> > 	for (hash = 0; hash<IP_VS_SVC_TAB_SIZE; hash++) {
> > 		write_lock_bh(&__ip_vs_svc_lock);
> > 		list_for_each_entry_safe(svc, tmp, &ip_vs_svc_table[hash],
> > 					 s_list) {
> > 			if (net_eq(svc->net, net)) {
> > 				ip_vs_svc_unhash(svc);
> > 				__ip_vs_del_service(svc);
> > 			}
> > 		}
> > 		list_for_each_entry_safe(svc, tmp, &ip_vs_svc_fwm_table[hash],
> > 					 f_list) {
> > 			if (net_eq(svc->net, net)) {
> > 				ip_vs_svc_unhash(svc);
> > 				__ip_vs_del_service(svc);
> > 			}
> > 		}
> > 		write_unlock_bh(&__ip_vs_svc_lock);
> > 	}
> > 	LeaveFunction(2);
> > }
> > 
> > Called just after the __ip_vs_control_cleanup_sysctl()
> 
> 	Hm, no. ip_vs_service_cleanup() should be called
> by ip_vs_cleanup() before or after nf_unregister_hooks().
> The rule is that ip_vs_flush() should be called before
> ip_vs_conn_flush() because after ip_vs_flush() no more
> connections can be created and even if hooks are still
> registered the packets can not create conns in the netns. Then
> ip_vs_conn_flush() will remove all existing connections and
> ip_vs_control_cleanup() can remove all real servers with
> ip_vs_trash_cleanup(). I mean, per-netns calls.
> 
OK I will try to do that, both with and without throttle in ip_vs_in()

> 	Also, may be all code that was called in old
> kernels by ip_vs_cleanup() should be now called by
> __ip_vs_cleanup(net), i.e. we can preserve the needed order
> of all functions but now also per-netns. For example, for
> ip_vs_ctl.c ip_vs_control_init() can remain as global but it
> should not register ipvs_control_ops. Then we
> can rename __ip_vs_control_init to ip_vs_control_init_net()
> and to call it from __ip_vs_init(). I.e. all such files
> will have global function and also _init_net and
> _cleanup_net. Now there are many register_pernet_subsys()
> calls and I'm not sure we preserve the needed order for
> cleanup. Are the ->exit methods called in reverse order?

Yes

> I don't see it in ops_exit_list() and we can not rely
> on such registration order. I think, ip_vs_init() should
> call global functions as now but __ip_vs_init() and
> __ip_vs_cleanup() should call the _net methods in right
> order.

Exactly,
I have already done that in my next patch,  and some other small changes :-)
For the ip_vs.ko there is only one register/unregister now, the schedulers still have their own.
Hopefully the patch is ready to morrow

Regards
Hans
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