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Date:	Fri, 27 Sep 2013 16:04:00 -0700
From:	Salam Noureddine <>
To:	Stephen Hemminger <>
Cc:	"David S. Miller" <>,
	Alexey Kuznetsov <>,
	James Morris <>,
	Hideaki YOSHIFUJI <>,
	Patrick McHardy <>,
Subject: Re: [PATCH 2/2] ipv4 igmp: use del_timer_sync instead of del_timer in ip_mc_down

I tried using in_dev_put instead of __in_dev_put and it seems to work
fine in my testing on linux-3.4. I don't quite understand the reason
for having __in_dev_put decrement the refcnt without destroying the
in_device in case it reaches 0. If the timer handler assumes it cannot
be the last one to hold a reference then that would mean it doesn't
need the reference in the first place.

If this solution is preferable to using del_timer_sync I would go
ahead and submit a new patch.



On Thu, Sep 5, 2013 at 10:22 AM, Salam Noureddine
<> wrote:
> On Thu, Sep 5, 2013 at 8:43 AM, Stephen Hemminger
> <> wrote:
>> On Wed,  4 Sep 2013 23:43:24 -0700
>> Salam Noureddine <> 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 <>
>> 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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