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Date:      Thu, 2 Feb 2012 23:09:25 -0800
From:      Adrian Chadd <adrian@freebsd.org>
To:        lev@freebsd.org
Cc:        freebsd-wireless@freebsd.org
Subject:   Re: "ath0: device timeout" when environment is clear
Message-ID:  <CAJ-Vmo=4Hp7RChoTXD1GftTWDKFT6pq%2BjU=jinSgKN=OUgb8EA@mail.gmail.com>
In-Reply-To: <1167992329.20120203110304@serebryakov.spb.ru>
References:  <743722267.20120202195757@serebryakov.spb.ru> <CAJ-Vmo=js__O2YfPuRQTH0WfaDg1oo0LmugoCV5hi6HUtksprQ@mail.gmail.com> <1292923023.20120202232810@serebryakov.spb.ru> <CAJ-VmonApDTGUU0JgFWQApktHW0Xi6Fq2dbDNkP_Hu_Q29KL9g@mail.gmail.com> <208667374.20120203002726@serebryakov.spb.ru> <CAJ-Vmo=OuBC65ie7t2LeQof4mPngrEyNPwwuJuijk0W%2BVjGCDg@mail.gmail.com> <1167992329.20120203110304@serebryakov.spb.ru>

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Hi,

I'm not really able to suggest any specific diagnosis. I'd just be
debugging it and trying to figure out why exactly it's occuring.

There's only two places where TX "starts" - ath_start() and
ath_raw_xmit(). The watchdog timer is bumped there. The questions are:

* is it being bumped but no frame is being queued (eg because
aggregation is somehow hanging);
* is it being bumped but not cleared correctly;
* is it being bumped but the TX interrupt is being missed (which would
show up as frames in the TX queue, which you would've seen in previous
debugging);
* is there a race condition between ath_start( )/ath_raw_xmit() and
the TX completion task, which is causing it to be set whe nthere's no
frames queued (due to a lack of locking there..)

I'm still knee deep in work code (hi radars and DFS!) so I can't
really dedicate any further time to figuring this stuff out. But
there's a lot of weird and wonderful locking issues in ath and
net80211. Sigh.


Is this running on a multi-core/CPU box, or is it single-core?


Adrian



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