netdev - Re: loopback device reference count leakage

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Message-ID: <CO2PR17MB01057D980A6B7827B48BD7A7A1760@CO2PR17MB0105.namprd17.prod.outlook.com>
Date:   Fri, 27 Jan 2017 03:15:52 +0000
From:   Kaiwen Xu <kevin@...xu.net>
To:     Cong Wang <xiyou.wangcong@...il.com>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: loopback device reference count leakage

On Thu, Jan 26, 2017 at 05:01:38PM -0800, Cong Wang wrote:
> I'd suggest to you add some debugging printk's to the dst refcount functions,
> or maybe just inside dst_gc_task(). I think the last dst referring to
> the loopback
> dev is still being referred at that point, which prevents GC from destroying it.

Thanks for the suggestion! I will test it out.

> Meanwhile, if it would be also helpful if you can share how you managed to
> reproduce this reliably, I saw this bug in our data center before but never
> know how to reproduce it.

I used one of our applications to reproduce the issue, to be honest, I
haven't completely isolated which part of the code is triggering the
bug. However, the suspicion is that, since the application basically
acts as a web crawler, the bug is manifested after initiating a large
amount connections to a wide range of IP addresses in a short period of
time. Hope it somewhat helps.

Thanks,
Kaiwen