linux-kernel - Re: ath9k becon loss messages

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Date:	Mon, 6 Apr 2009 14:05:46 +0300
From:	Kalle Valo <kalle.valo@....fi>
To:	Helmut Schaa <helmut.schaa@...glemail.com>
Cc:	Michael Buesch <mb@...sch.de>,
	Jaswinder Singh Rajput <jaswinder@...nel.org>,
	Sujith <Sujith.Manoharan@...eros.com>,
	wireless <linux-wireless@...r.kernel.org>,
	David Miller <davem@...emloft.net>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: ath9k becon loss messages

On Mon, Apr 6, 2009 at 1:51 PM, Helmut Schaa
<helmut.schaa@...glemail.com> wrote:
> Am Montag, 6. April 2009 schrieb Kalle Valo:
>
>> But ath9k nor iwlwifi don't support beacon filtering and this is a
>> problem in mac80211. We need to disable the beacon loss check in
>> mac80211, most probably by stopping the associated timer whenever
>> scanning.
>
> Yeah, but the first execution of the timer will then also detect
> beacon loss:
>
> 1006   if (!((local->hw.flags & IEEE80211_HW_BEACON_FILTER) &&
> 1007         (local->hw.conf.flags & IEEE80211_CONF_PS)) &&
> 1008       time_after(jiffies,
> 1009            ifmgd->last_beacon + IEEE80211_MONITORING_INTERVAL)) {
>
> If the scan took longer then IEEE80211_MONITORING_INTERVAL (=2 sec) this
> condition will apply just after the scan finished.

Not if we do "mod_timer(&ifmgd->timer, jiffies +
IEEE80211_MONITORING_INTERVAL)" after the scan has finished. That way
there's enought time to receive beacons before the timer triggers.

> Maybe this issue could be
> avoided by making the beacon loss detection smarter then just checking if no
> beacon was received within the last two seconds.

Definitely the beacon loss logic should be smarter, but I think that
should be improved separately. I just have tried to do small changes
at a time to avoid regressions and I didn't even consider improving
the beacon loss logic.

Kalle
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