From: Kan Yan <kyan@google.com>
To: Johannes Berg <johannes@sipsolutions.net>
Cc: "Toke Høiland-Jørgensen" <toke@redhat.com>,
linux-wireless@vger.kernel.org,
Make-Wifi-fast <make-wifi-fast@lists.bufferbloat.net>,
ath10k@lists.infradead.org, "John Crispin" <john@phrozen.org>,
"Lorenzo Bianconi" <lorenzo@kernel.org>,
"Felix Fietkau" <nbd@nbd.name>,
"Rajkumar Manoharan" <rmanohar@codeaurora.org>,
"Kevin Hayes" <kevinhayes@google.com>
Subject: Re: [Make-wifi-fast] [PATCH v6 3/4] mac80211: Implement Airtime-based Queue Limit (AQL)
Date: Fri, 8 Nov 2019 17:04:08 -0800 [thread overview]
Message-ID: <CA+iem5vOipcDbSiVgjeK+Rr2mK8nkMJABH=KuEhFo95RCPMAfQ@mail.gmail.com> (raw)
In-Reply-To: <300bf0146db6c0d5890699b3911d35174d28c9c0.camel@sipsolutions.net>
[-- Attachment #1: Type: text/plain, Size: 1118 bytes --]
It is most likely just insufficient locking. active_txq_lock is per AC,
can't protect local->aql_total_pending_airtime against racing conditions
On Fri, Nov 8, 2019 at 3:17 AM Johannes Berg <johannes@sipsolutions.net>
wrote:
> On Fri, 2019-11-08 at 12:10 +0100, Toke Høiland-Jørgensen wrote:
>
> > Right, bugger. I was thinking maybe there's a case where skbs can be
> > cloned (and retain the tx_time_est field) and then released twice?
>
> They could be cloned, but I don't see how that'd be while *inside* the
> stack and then they get reported twice - unless the driver did something
> like that?
>
> I mean, TCP surely does that for example, but it's before we even get to
> mac80211.
>
> > Or
> > maybe somewhere that steps on the skb->cb field in some other way?
> > Couldn't find anything obvious on a first perusal of the TX path code,
> > but maybe you could think of something?
>
> No, sorry. But I also didn't actually look at the driver at all.
>
> > Otherwise I guess we'll be forced to go and do some actual,
> > old-fashioned debugging ;)
>
> :)
>
> johannes
>
>
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next prev parent reply other threads:[~2019-11-09 1:04 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-23 9:58 [Make-wifi-fast] [PATCH v6 0/4] Add Airtime Queue Limits (AQL) to mac80211 Toke Høiland-Jørgensen
2019-10-23 9:59 ` [Make-wifi-fast] [PATCH v6 1/4] mac80211: Shrink the size of ack_frame_id to make room for tx_time_est Toke Høiland-Jørgensen
2019-11-08 10:03 ` Johannes Berg
2019-10-23 9:59 ` [Make-wifi-fast] [PATCH v6 2/4] mac80211: Import airtime calculation code from mt76 Toke Høiland-Jørgensen
2019-11-08 10:07 ` Johannes Berg
2019-11-08 10:55 ` Toke Høiland-Jørgensen
2019-11-08 10:57 ` Johannes Berg
2019-10-23 9:59 ` [Make-wifi-fast] [PATCH v6 3/4] mac80211: Implement Airtime-based Queue Limit (AQL) Toke Høiland-Jørgensen
2019-11-08 10:09 ` Johannes Berg
2019-11-08 10:56 ` Toke Høiland-Jørgensen
2019-11-08 10:59 ` Johannes Berg
2019-11-08 11:10 ` Toke Høiland-Jørgensen
2019-11-08 11:17 ` Johannes Berg
2019-11-09 1:04 ` Kan Yan [this message]
2019-11-09 1:22 ` Kan Yan
2019-11-09 11:22 ` Toke Høiland-Jørgensen
2019-10-23 9:59 ` [Make-wifi-fast] [PATCH v6 4/4] mac80211: Use Airtime-based Queue Limits (AQL) on packet dequeue Toke Høiland-Jørgensen
2019-11-08 10:17 ` Johannes Berg
2019-11-08 11:01 ` Toke Høiland-Jørgensen
2019-11-08 11:05 ` Johannes Berg
2019-11-07 6:14 ` [Make-wifi-fast] [PATCH v6 0/4] Add Airtime Queue Limits (AQL) to mac80211 Kan Yan
2019-11-07 10:55 ` Toke Høiland-Jørgensen
2019-11-07 21:24 ` Dave Taht
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