netdev - Re: [PATCH] [PATCH net] net: Do not hold the reference for the same sk_rx

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Message-ID: <87fuidv6ts.fsf@redhat.com>
Date:   Thu, 16 Mar 2017 11:45:03 +0100
From:   Jakub Sitnicki <jkbs@...hat.com>
To:     Kevin Xu <kaiwen.xu@...u.com>
Cc:     "davem\@davemloft.net" <davem@...emloft.net>,
        "netdev\@vger.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH] [PATCH net] net: Do not hold the reference for the same sk_rx_dst.

On Thu, Mar 16, 2017 at 10:12 AM GMT, Kevin Xu wrote:
> Do you mean the message looping endlessly?

No, the message is emitted just once. Around 100 seconds after
destroying a few namespaces. Occurs not so often, maybe once per ten
runs.

-Jakub

> If so, then I suppose it's a different bug.
>
> Kevin
>
>> On Mar 16, 2017, at 3:01 AM, Jakub Sitnicki <jkbs@...hat.com> wrote:
>>
>>> On Thu, Mar 16, 2017 at 08:08 AM GMT, Kevin Xu wrote:
>>> In some rare cases, inet_sk_rx_dst_set() may be called multiple times
>>> on the same dst, causing reference count leakage. Eventually, it
>>> prevents net_device to be destroyed. The bug then manifested as
>>>
>>> unregister_netdevice: waiting for lo to become free. Usage count = 1
>>>
>>> in the kernel log, preventing new network namespace creation.
>>>
>>> The patch works around the issue by checking whether the socket already
>>> has the same dst set.
>>>
>>> Signed-off-by: Kevin Xu <kaiwen.xu@...u.com>
>>> ---
>>
>> FWIW, with this patch applied I'm still sometimes seeing:
>>
>> [  125.928095] unregister_netdevice: waiting for lo to become free. Usage count = 1
>>
>> -Jakub