netdev - Re: [CFT][PATCH] net: Delay default_device_exit_batch until no devices are unregistering

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Message-Id: <20130917.192158.941189471705765317.davem@davemloft.net>
Date:	Tue, 17 Sep 2013 19:21:58 -0400 (EDT)
From:	David Miller <davem@...emloft.net>
To:	ebiederm@...ssion.com
Cc:	fruggeri@...stanetworks.com, edumazet@...gle.com, jiri@...nulli.us,
	alexander.h.duyck@...el.com, amwang@...hat.com,
	netdev@...r.kernel.org
Subject: Re: [CFT][PATCH] net: Delay default_device_exit_batch until no
 devices are unregistering

From: ebiederm@...ssion.com (Eric W. Biederman)
Date: Mon, 16 Sep 2013 20:49:31 -0700

>  /* Delayed registration/unregisteration */
>  static LIST_HEAD(net_todo_list);
> +static atomic_t netdev_unregistering = ATOMIC_INIT(0);
> +static DECLARE_WAIT_QUEUE_HEAD(netdev_unregistering_wait);

I think you don't need this atomic.

Something like this should work and seems much simpler:

1) Still use the netdev_unregistering_wait queue, that's fine.

2) In netdev_run_todo(), unconditionally wake it up at the end of
   the while() loop.

3) In default_device_exit_batch() use the same retry logic but
   your tests are on list_empty(&net_todo_list() rather than the
   new atomic count.

I think with this simplification I'm fine to apply this patch after
it has been tested properly.

Long term I'd like to see a per-namespace todo list, as seems to
have been suggested and discussed already.

Thanks.
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