Message-ID: <1340875996.4491.29.camel@jlt3.sipsolutions.net> (sfid-20120628_113322_586754_1877B532)
Subject: Re: mac80211 auth/assoc in multi-channel scenarios
From: Johannes Berg <johannes@sipsolutions.net>
To: Arik Nemtsov <arik@wizery.com>
Cc: Eliad Peller <eliad@wizery.com>,
	linux-wireless <linux-wireless@vger.kernel.org>
Date: Thu, 28 Jun 2012 11:33:16 +0200
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On Wed, 2012-06-27 at 20:05 +0300, Arik Nemtsov wrote:

> > Yeah, that was one of the other options I considered in my original
> > email ... but this call must be able to sleep, and the TX processing in
> > mac80211 cannot sleep, so unless we bypass all processing (which seems
> > wrong) that would be rather difficult to implement.
> 
> Good point. But another race to consider the the
> multi-channel/multi-vif scenario, where the driver already has a lot
> of packets queued up, so the time will expire before we get a chance
> to Tx. Again this is not a problem in practice (since it's the VO ac).

If the vif is on a different channel, the driver really should assign it
different queues and then there shouldn't be much queued up, right?
Also, if you really have >100ms latency on your queues, you have a major
problem anyway I'd think?

> How about somehow requiring a multi channel driver to give always
> Tx-ack? That will mean we can abandon the retry timers, and rely on
> the driver to give an answer within a reasonable time.

That doesn't mean we can abandon the retry timers though? Then again,
maybe it does, we could start the timer only when we get the status
information I guess?

I'm not sure I'd want to *require* this, but it sounds like a good thing
we could do to address this possible race for drivers that do support
reliable status reports?

johannes