Re: Status of 802.11s in wireless-testing?

[Javier Cardona <javier@cozybit.com>]

Hi Johannes,

On Wed, Aug 5, 2009 at 10:04 AM, Johannes Berg<johannes@sipsolutions.net> wrote:
> Right now, except from the stuff Luis had broken and fixed, the real
> problem is that there are a bunch of bugs that appear to have been in
> the code forever, just never noticed -- for instance the code can end up
> calling synchronize_rcu() in an atomic section.

I agree that there is a bug in that would cause a synchronize_rcu() in
an atomic section when the mpath table grows beyond a certain size.
The bug was there since the first submission of the mesh code, yes.

However, the "bunch of bugs that appear to have been in the code
forever" are, I believe, regressions.  In particular we've identified:
 - Airtime Link Metric broken (fix in progress)
 - Forwarding path broken (fixed here:
http://marc.info/?l=linux-wireless&m=124698982910794&w=2)
 - mpath pending queue broken (fixed here:
http://marc.info/?l=linux-wireless&m=124717648406661&w=2)
 - PREQ notification broken (fixed here:
http://marc.info/?l=linux-wireless&m=124752948320455&w=2)

We've been busy with those but the synchronize_rcu fix is next in our list.

> This is the reason for disabling it -- it can splatter all over the
> scheduler if that happens, and it's not clear to me that it cannot
> happen. It seems not to happen in _most_ scenarios, but I've certainly
> caused it to happen by not beaconing, for instance.

I also agree with your assessment of the severity of the bug.
Hopefully we'll get to fix it really soon so we can re-enable mesh
again.

Thanks,