From: Sujith <Sujith.Manoharan@atheros.com>
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Message-ID: <18872.37875.417055.649869@gargle.gargle.HOWL> (sfid-20090312_055200_703560_2D7BFF62)
Date: Thu, 12 Mar 2009 10:17:47 +0530
To: Vladimir Senkov <hangup@gmail.com>
CC: "linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>
Subject: ath9k panic when connecting to 802.11n-enabled AP
In-Reply-To: <14df1c3e0903112141w645c716bu47e2309353527535@mail.gmail.com>
References: <14df1c3e0903112141w645c716bu47e2309353527535@mail.gmail.com>
Sender: linux-wireless-owner@vger.kernel.org

Vladimir Senkov wrote:
> My client machine (running wireless-testing kernel updated with git
> today) panics when connecting to a hostapd access point (also running
> ath9k) only when 802.11n is enabled on the access point.
> More specifically, here is the hostapd configuration that causes the
> client to crash:
> ieee80211n=0
> ht_capab=[HT40+][SHORT-GI-40][DSSS_CCK-40]

ieee80211n should be 1 to enable 11n.

> If I disable 802.11n on the access point everything works ok.
> Interesting enough, access point machine never crashes. At one point
> both access point and client machine ran identical code and client
> would always crash while the access point box would stay up. So
> upgraded client to the latest and greatest and tried a few versions in
> between, this panic has been very consistent. It always panics right
> after 1st attempt to associate.
> 
> I was able to narrow down the panic to this assert ath_rc_ratefind_ht() in rc.c:
>         ASSERT((rate_table->info[rate].valid && !ath_rc_priv->single_stream) ||
>                (rate_table->info[rate].valid_single_stream &&
>                 ath_rc_priv->single_stream));
> When I ifdef'ed this assert panic went away and everything sort of
> worked (haven't tested it heavily), but the performance dropped to
> about 700Kbps. I usually get 10x when 802.11n is off and there is no
> panic.
> 
> Has anyone else seen this?

A couple of bugs were fixed dealing with this issue, but looks like more
lurk around. Can you attach the hostapd.conf, hostapd logs (hostapd -d),
client side kernel logs [1] ?, from loading the driver to the point when you associate
and get the panic.

[1]: See http://wireless.kernel.org/en/users/Drivers/ath9k on how to enable debug.

Sujith