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

From: Fengguang Wu
Date: Thu Jul 28 2016 - 08:54:24 EST

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]

config: i386-randconfig-s0-201630 (attached as .config)
compiler: gcc-6 (Debian 6.1.1-9) 6.1.1 20160705
# 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?

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'

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.