netdev - Re: [PATCH 2/2] ipv4 igmp: use del_timer_sync instead of del_timer in ip_mc

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Message-ID: <CAO7SqHA4LJhy_NBkPLViJB3s7hM85qd88pmjy3hq-hCCuQstaA@mail.gmail.com>
Date:	Thu, 5 Sep 2013 10:22:53 -0700
From:	Salam Noureddine <noureddine@...stanetworks.com>
To:	Stephen Hemminger <stephen@...workplumber.org>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Alexey Kuznetsov <kuznet@....inr.ac.ru>,
	James Morris <jmorris@...ei.org>,
	Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
	Patrick McHardy <kaber@...sh.net>, netdev@...r.kernel.org
Subject: Re: [PATCH 2/2] ipv4 igmp: use del_timer_sync instead of del_timer in ip_mc_down

On Thu, Sep 5, 2013 at 8:43 AM, Stephen Hemminger
<stephen@...workplumber.org> wrote:
> On Wed,  4 Sep 2013 23:43:24 -0700
> Salam Noureddine <noureddine@...stanetworks.com> wrote:
>
>> Delete timers using del_timer_sync in ip_mc_down. Otherwise, it is
>> possible for the timer to be the last to release its reference to the
>> in_device and since __in_dev_put doesn't destroy the in_device we
>> would end up leaking a reference to the net_device and see messages
>> like the following,
>>
>> unregister_netdevice: waiting for eth0 to become free. Usage count = 1
>>
>> Tested on linux-3.4.43.
>>
>> Signed-off-by: Salam Noureddine <noureddine@...stanetworks.com>
>
> Why not just call in_dev_put instead which just proper cleanup.
> It is less risky of deadlock than del_timer_sync.

I was wondering if there was a reason behind using __in_dev_put since
the multicast code
is the only user of that function. I can test using in_dev_put
instead. Should __in_dev_put
be removed altogether in that case?

Thanks,

Salam
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