netdev - Attempt to auto-load em_cmp.ko results in negative module refcnt

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Message-ID: <20150216105912.GA16798@zenon.in.qult.net>
Date:	Mon, 16 Feb 2015 11:59:12 +0100
From:	Ignacy Gawedzki <ignacy.gawedzki@...en-communications.fr>
To:	netdev@...r.kernel.org
Subject: Attempt to auto-load em_cmp.ko results in negative module refcnt

Hi,

This simple test case

  tc qdisc add dev eth0 root handle 1: htb
  tc class add dev eth0 root classid 1: htb rate 1Gbit
  tc class add dev eth0 parent 1: classid 1:1 htb rate 1Gbit
  tc filter add dev eth0 parent 1: basic match 'cmp(u8 at 0 eq 0)' classid 1:1

fails with the following

  RTNETLINK answers: No such file or directory
  We have an error talking to the kernel

if em_cmp.ko is not loaded beforehand.

After that, lsmod shows that em_cmp.ko is loaded indeed, but its usage count
is -1 and an attempd to unload the module results in a "BUG at
kernel/module.c:752".

This has been broken pretty recently, I'm currently attempting a git bisect on
this.

-- 
Ignacy Gawędzki
R&D Engineer
Green Communications
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