Return-path: Received: from mail-ea0-f182.google.com ([209.85.215.182]:34689 "EHLO mail-ea0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752663AbaAVQmX (ORCPT ); Wed, 22 Jan 2014 11:42:23 -0500 Received: by mail-ea0-f182.google.com with SMTP id r15so3948318ead.27 for ; Wed, 22 Jan 2014 08:42:22 -0800 (PST) Date: Wed, 22 Jan 2014 17:41:22 +0100 From: Karl Beldan To: Helmut Schaa , Johannes Berg Cc: linux-wireless , Karl Beldan Subject: Re: [PATCH] mac80211: send {add,del}ba on AC_VO like other mgmt frames, as per spec Message-ID: <20140122164122.GC18365@magnum.frso.rivierawaves.com> (sfid-20140122_174227_916322_02E4D0F9) References: <1390391564-18481-1-git-send-email-karl.beldan@gmail.com> <1390394079.4334.30.camel@jlt4.sipsolutions.net> <20140122130924.GA18365@magnum.frso.rivierawaves.com> <20140122152845.GB18365@magnum.frso.rivierawaves.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 In-Reply-To: Sender: linux-wireless-owner@vger.kernel.org List-ID: On Wed, Jan 22, 2014 at 04:36:14PM +0100, Helmut Schaa wrote: > On Wed, Jan 22, 2014 at 4:28 PM, Karl Beldan wrote: > > On Wed, Jan 22, 2014 at 02:33:14PM +0100, Helmut Schaa wrote: > >> On Wed, Jan 22, 2014 at 2:09 PM, Karl Beldan wrote: > >> > On Wed, Jan 22, 2014 at 01:34:39PM +0100, Johannes Berg wrote: > >> >> Hmm. I guess you're right about the spec, but I vaguely remember races > >> >> in this with the delBA going out too soon or so? > >> >> > >> > > >> > Indeed, this was intended by cf6bb79 ("Use appropriate TID for sending > >> > BAR, ADDBA and DELBA frames") and I overlooked it .. will look into it, > >> > thanks. > >> > I Cced Helmut who authored the said commit. > >> > >> You're right. There were some issues with that, but that was 2 years ago :) > >> > >> Sending ADDBA over AV_VO should be safe. > >> If a DELBA is sent as AC_VO it might get received before the last AMPDU > >> of the BlockAck session. So, the pending AMPDUs will get dropped at the > >> receiver. > >> > >> In theory this could also be avoided by properly flushing all pending AMPDUs > >> of the TID in question from the hw queues or by waiting for the tx status > >> of all pending AMPDUs. > >> > > > > I just looked at the code with your change in mind and couldn't find any > > issue caused by sending {add,del}ba on AC_VO. > > As of today, a delba is sent only after a driver has called 'purposely' > > ieee80211_stop_tx_ba_cb_irqsafe so I see no issue with the delba either, > > do you see one today ? > > If the driver does the right thing by flushing the right frames in the > hw tx queues > I think this should be ok. At least rt2x00 is not doing that, but > maybe that's just > an issue in rt2x00 :( > I see you are one of the maintainers of the ralink drivers, do you intend to fix it in those ? Callers of ieee80211_stop_tx_ba_cb_irqsafe are: ath9k ath9k_htc carl9170 wcn36xx brcm80211 iwlegacy iwlwifi mwl8k rt2x00 rtlwifi Johannes, what is your impression ? Karl