linux-kernel - Re: Bisected 3.9 regression for iwl4965 connection problem to 1672c0e3

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Message-ID: <20130522115908.GA22547@redhat.com>
Date:	Wed, 22 May 2013 13:59:08 +0200
From:	Stanislaw Gruszka <sgruszka@...hat.com>
To:	Johannes Berg <johannes@...solutions.net>
Cc:	Jake Edge <jake@....net>, linux-wireless@...r.kernel.org,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: Bisected 3.9 regression for iwl4965 connection problem to
 1672c0e3

On Tue, May 07, 2013 at 05:35:25PM +0200, Stanislaw Gruszka wrote:
> On Tue, May 07, 2013 at 03:53:30PM +0200, Johannes Berg wrote:
> > > I'm not sure if I like to add passive_no_rx to iwlegacy. Stopping queues
> > > and waiting for beacon looks sticky, what happen if beacon will not be
> > > received?
> > 
> > Good question, do we get stuck? I was assuming we'd time out, but maybe
> > that's not the case?
> 
> AFICT, we wake queues only if beacon arrives or mac80211 call drv_config
> with BSS_CHANGED_IDLE. I'm not sure if the latter prevent stuck. 

It should prevent stuck. When we fail to auth, drv_config() with BSS_CHANGED_IDLE
is called via:

ieee80211_destroy_auth_data ->
ieee80211_vif_release_channel ->
__ieee80211_vif_release_channel ->
ieee80211_unassign_vif_chanctx ->
ieee80211_bss_info_change_notify

But there is need to have ->vif.chanctx_conf valid in 
__ieee80211_vif_release_channel(), where is below condition:

        conf = rcu_dereference_protected(sdata->vif.chanctx_conf,
                                         lockdep_is_held(&local->chanctx_mtx));
        if (!conf)
                return;

I'm not sure if that always happen. Perhaps would be better to change
BSS_CHANGED_IDLE to BSS_CHANGED_BSSID, which is called directly from
ieee80211_destroy_auth_data() ?

Stanislaw

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