Re: [PATCH] mac80211: Fix deadlock in ieee80211_do_stop.

["Luis R. Rodriguez" <mcgrof@gmail.com>]

On Fri, Nov 19, 2010 at 12:55 PM, Ben Greear <greearb@candelatech.com> wrote:
> On 11/19/2010 09:57 AM, Johannes Berg wrote:
>>
>> On Fri, 2010-11-19 at 15:34 +0100, Tejun Heo wrote:
>>
>>> Awesome.  :-)
>>>
>>> Ben, if you have trouble generating full trace, please let me know if
>>> there's something I can buy which isn't too expensive to reproduce the
>>> problem.  I would be happy to track it down myself.
>>
>> Maybe you can try Ben's setup in kvm (or directly on your box if you
>> like) with mac80211_hwsim. From a mac80211 POV it should be almost
>> equivalent, although it'll do different memory allocation patterns etc.
>
> I tried manually backing out my patch, and now I can no longer reproduce
> the problem.  Maybe something in -rc2 fixed it, or maybe some changes
> to my environment just made it harder to hit.
>
> If you see no logical reason why calling flush_work with RTNL held
> would cause trouble, then I guess we can just leave the code as is
> for now.
>
> If you do want to play with this yourself, I think any ath5k type adapter
> with 64+ virtual stations configured would be a valid test case.  My
> application calls ifdown/ifup on them a few times after being created
> and then generates traffic (and gathers stats, calls 'iwconfig', etc).
> As configured in the original scenario that reproduced the problem,
> the STAs had no encryption and were all associating with a single AP.
> wpa_supplicant was not being used.

FWIW, I had to do similar tests before and Ben offered up a perl
script to do something similar to what his proprietary app does upon
device bring up. I've modified it just a bit and you can find it here:

http://www.kernel.org/pub/linux/kernel/people/mcgrof/scripts/poo.pl

  Luis

  Luis