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

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Date:	Thu, 5 Sep 2013 08:43:12 -0700
From:	Stephen Hemminger <stephen@...workplumber.org>
To:	Salam Noureddine <noureddine@...stanetworks.com>
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 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.
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