Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752477AbdHJBgn (ORCPT ); Wed, 9 Aug 2017 21:36:43 -0400 Received: from mail-vk0-f48.google.com ([209.85.213.48]:37830 "EHLO mail-vk0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752363AbdHJBgl (ORCPT ); Wed, 9 Aug 2017 21:36:41 -0400 MIME-Version: 1.0 In-Reply-To: References: From: Wei Wang Date: Wed, 9 Aug 2017 18:36:39 -0700 Message-ID: Subject: Re: unregister_netdevice: waiting for eth0 to become free. Usage count = 1 To: John Stultz Cc: Cong Wang , lkml , Network Development , Linux USB List , "David S. Miller" , Felipe Balbi Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3155 Lines: 76 On Wed, Aug 9, 2017 at 6:26 PM, John Stultz wrote: > On Wed, Aug 9, 2017 at 5:36 PM, Wei Wang wrote: >> On Wed, Aug 9, 2017 at 4:44 PM, John Stultz wrote: >>> On Wed, Aug 9, 2017 at 4:34 PM, Cong Wang wrote: >>>> (Cc'ing Wei whose commit was blamed) >>>> >>>> On Mon, Aug 7, 2017 at 2:15 PM, John Stultz wrote: >>>>> On Mon, Aug 7, 2017 at 2:05 PM, John Stultz wrote: >>>>>> So, with recent testing with my HiKey board, I've been noticing some >>>>>> quirky behavior with my USB eth adapter. >>>>>> >>>>>> Basically, pluging the usb eth adapter in and then removing it, when >>>>>> plugging it back in I often find that its not detected, and the system >>>>>> slowly spits out the following message over and over: >>>>>> unregister_netdevice: waiting for eth0 to become free. Usage count = 1 >>>>> >>>>> The other bit is that after this starts printing, the board will no >>>>> longer reboot (it hangs continuing to occasionally print the above >>>>> message), and I have to manually reset the device. >>>>> >>>> >>>> So this warning is not temporarily shown but lasts until a reboot, >>>> right? If so it is a dst refcnt leak. >>> >>> Correct, once I get into the state it lasts until a reboot. >>> >>>> How reproducible is it for you? From my reading, it seems always >>>> reproduced when you unplug and plug your usb eth interface? >>>> Is there anything else involved? For example, network namespace. >>> >>> So with 4.13-rc3/4 I seem to trigger it easily, often with the first >>> unplug of the USB eth adapter. >>> >>> But as I get back closer to 4.12, it seemingly becomes harder to >>> trigger, but sometimes still happens. >>> >>> So far, I've not been able to trigger it with 4.12. >>> >>> I don't think network namespaces are involved? Though its out of my >>> area, so AOSP may be using them these days. Is there a simple way to >>> check? >>> >>> I'll also do another bisection to see if the bad point moves back any further. > > So I went through another bisection around and got 9514528d92d4 ipv6: > call dst_dev_put() properly as the first bad commit again. > >> If you see the problem starts to happen on commit >> 9514528d92d4cbe086499322370155ed69f5d06c, could you try reverting all >> the following commits: >> (from new to old) >> 1eb04e7c9e63 net: reorder all the dst flags >> a4c2fd7f7891 net: remove DST_NOCACHE flag >> b2a9c0ed75a3 net: remove DST_NOGC flag >> 5b7c9a8ff828 net: remove dst gc related code >> db916649b5dd ipv6: get rid of icmp6 dst garbage collector >> 587fea741134 ipv6: mark DST_NOGC and remove the operation of dst_free() >> ad65a2f05695 ipv6: call dst_hold_safe() properly >> 9514528d92d4 ipv6: call dst_dev_put() properly > > > And reverting this set off of 4.13-rc4 seems to make the issue go away. > > Is there anything I can test to help narrow down the specific problem > with that patchset? > Thanks John for confirming. Let me spend some time on the commits and I will let you know if I have some debug image for you to try. Wei > thanks > -john