netdev - Re: [PATCH v4] net: sched: convert qdisc linked list to hashtable

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Date:	Sun, 31 Jul 2016 19:21:27 +0800
From:	Fengguang Wu <lkp@...el.com>
To:	Jiri Kosina <jikos@...nel.org>
Cc:	kbuild-all@...org, Eric Dumazet <eric.dumazet@...il.com>,
	Jamal Hadi Salim <jhs@...atatu.com>,
	Phil Sutter <phil@....cc>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, Cong Wang <xiyou.wangcong@...il.com>
Subject: Re: [PATCH v4] net: sched: convert qdisc linked list to hashtable

On Thu, Jul 28, 2016 at 08:53:12PM +0800, Fengguang Wu wrote:
>On Thu, Jul 28, 2016 at 01:18:27PM +0200, Jiri Kosina wrote:
>>On Thu, 28 Jul 2016, kbuild test robot wrote:
>>
>>> [auto build test ERROR on v4.7-rc7]
>>> [also build test ERROR on next-20160728]
>>> [cannot apply to net/master net-next/master ipsec-next/master]
>>> [if your patch is applied to the wrong git tree, please drop us a note to help improve the system]
>>>
>>> url:    https://github.com/0day-ci/linux/commits/Jiri-Kosina/net-sched-convert-qdisc-linked-list-to-hashtable/20160728-182303
>>> config: i386-randconfig-s0-201630 (attached as .config)
>>> compiler: gcc-6 (Debian 6.1.1-9) 6.1.1 20160705
>>> reproduce:
>>>         # save the attached .config to linux build tree
>>>         make ARCH=i386
>>>
>>> All errors (new ones prefixed by >>):
>>>
>>>    net/built-in.o: In function `dev_activate':
>>> >> (.text+0x37ccb): undefined reference to `qdisc_hash_add'
>>
>>Dear 0-day team,
>>
>>could you please check my question regarding this very build failure here?
>>
>>	lkml.kernel.org/r/alpine.LNX.2.00.1607141612560.24757@...bk.fhfr.pm
>
>Sorry I missed that. For your convenience, here is the answer to the
>original email:
>
>>This issue is be there even without my patch (but with qdisc_list_add
>>instead), isn't it?
>
>Yes it looks so, this number happens in a number of places:
>
>dns_query.c:(.text+0x39b84): undefined reference to `qdisc_hash_add'
>include/linux/netdevice.h:1935: undefined reference to `qdisc_hash_add'
>net/core/netevent.c:31: undefined reference to `qdisc_hash_add'
>net/sched/sch_generic.c:789: undefined reference to `qdisc_hash_add'
>sch_generic.c:(.text+0x33487): undefined reference to `qdisc_hash_add'
>switchdev.c:(.text+0x3bf58): undefined reference to `qdisc_hash_add'
>sysctl_net.c:(.text+0x31f70): undefined reference to `qdisc_hash_add'
>(.text.dev_activate+0x228): undefined reference to `qdisc_hash_add'
>(.text+0x37d0b): undefined reference to `qdisc_hash_add'
>wext-proc.c:(.text+0x390a8): undefined reference to `qdisc_hash_add'

Jiri, I just double checked and find no similar errors related to
qdisc_list_add(). The parent commit 95556a8838 ("dccp: avoid deadlock
in dccp_v4_ctl_send_reset") builds fine without error.

Thanks,
Fengguang

>>The problem is that sch_generic.c (where dev_activate() is) is being
>>compiled everytime CONFIG_NET is set, but sch_api.c (where
>>qdisc_list_add() is defined) only when CONFIG_NET_SCHED is set (and there
>>is no stub for !CONFIG_NET_SCHED case).
>
>So it looks like a more general problem than specific to this patch.
>
>Thanks,
>Fengguang