Re: [Make-wifi-fast] Fwd: [PATCH] mac80211: prevent skb/txq mismatch

[Dave Taht <dave.taht@gmail.com>]

If everybody could track their experiences here, that would help.

https://bugs.lede-project.org/index.php?do=details&task_id=368


On Wed, Jan 18, 2017 at 9:38 AM, Jon Pike <jonpike54@gmail.com> wrote:
> And,  it is probably worth mentioning that I also have IPV6 routing
> disabled, after what seemed like an issue with a local device being overly
> chatty.
>
> Have also reread a bit,  and see that Jan 3 or 4 seems to be the date of ATF
> removal, so I assume I still have it.
>
> On Jan 18, 2017 9:00 AM, <make-wifi-fast-request@lists.bufferbloat.net>
> wrote:
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>    1. Re: Fwd: [PATCH] mac80211: prevent skb/txq mismatch (Jon Pike)
>
>
>
> ---------- Forwarded message ----------
> From: Jon Pike <jonpike54@gmail.com>
> To: make-wifi-fast@lists.bufferbloat.net
> Cc:
> Date: Tue, 17 Jan 2017 22:58:30 -0800
> Subject: Re: [Make-wifi-fast] Fwd: [PATCH] mac80211: prevent skb/txq
> mismatch
> I'm pretty clueless on this,  but as a single data point, my Archer C7 has
> abt 21 days of uptime now, since my last update, as the single router in a 4
> person household.  I've been running cake/piece of cake the whole time.
>
> Standard disclaimers apply as to clueless user not knowing if his FW version
> has anything to do with the issue in question, or if its connected to other
> things like whatever is going on with the airtime fairness.  But the comment
> in the third paragraph sounded interesting in light of my lack of a crash
> and running a SQM method, FWIW.
>
> My last update was a sysupgrade to LEDE Reboot SNAPSHOT r2687-dc5f496 pretty
> sure date was 12-27-16.
>
>
> Today's Topics:
>
>    1. Fwd: [PATCH] mac80211: prevent skb/txq mismatch (Dave Taht)
>
>
> ---------- Forwarded message ----------
> From: Dave Taht <dave.taht@gmail.com>
> To: make-wifi-fast@lists.bufferbloat.net
> Cc:
> Date: Thu, 12 Jan 2017 10:44:12 -0800
> Subject: [Make-wifi-fast] Fwd: [PATCH] mac80211: prevent skb/txq mismatch
> yea! (I think)
>
>
> ---------- Forwarded message ----------
> From: Michal Kazior <michal.kazior@tieto.com>
> Date: Thu, Jan 12, 2017 at 6:28 AM
> Subject: [PATCH] mac80211: prevent skb/txq mismatch
> To: johannes@sipsolutions.net
> Cc: linux-wireless@vger.kernel.org, greearb@candelatech.com,
> mohammed@qti.qualcomm.com, Michal Kazior <michal.kazior@tieto.com>
>
>
> Station structure is considered as not uploaded
> (to driver) until drv_sta_state() finishes. This
> call is however done after the structure is
> attached to mac80211 internal lists and hashes.
> This means mac80211 can lookup (and use) station
> structure before it is uploaded to a driver.
>
> If this happens (structure exists, but
> sta->uploaded is false) fast_tx path can still be
> taken. Deep in the fastpath call the sta->uploaded
> is checked against to derive "pubsta" argument for
> ieee80211_get_txq(). If sta->uploaded is false
> (and sta is actually non-NULL) ieee80211_get_txq()
> effectively downgraded to vif->txq.
>
> At first glance this may look innocent but coerces
> mac80211 into a state that is almost guaranteed
> (codel may drop offending skb) to crash because a
> station-oriented skb gets queued up on
> vif-oriented txq. The ieee80211_tx_dequeue() ends
> up looking at info->control.flags and tries to use
> txq->sta which in the fail case is NULL.
> ..........
>
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-- 
Dave Täht
Let's go make home routers and wifi faster! With better software!
http://blog.cerowrt.org