Return-path: Received: from mail-ie0-f173.google.com ([209.85.223.173]:53269 "EHLO mail-ie0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756024AbaAVPgP (ORCPT ); Wed, 22 Jan 2014 10:36:15 -0500 Received: by mail-ie0-f173.google.com with SMTP id e14so11736335iej.18 for ; Wed, 22 Jan 2014 07:36:15 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <20140122152845.GB18365@magnum.frso.rivierawaves.com> 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> Date: Wed, 22 Jan 2014 16:36:14 +0100 Message-ID: (sfid-20140122_163618_839337_E1F5D207) Subject: Re: [PATCH] mac80211: send {add,del}ba on AC_VO like other mgmt frames, as per spec From: Helmut Schaa To: Karl Beldan Cc: Johannes Berg , linux-wireless , Karl Beldan Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-wireless-owner@vger.kernel.org List-ID: 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 :( Helmut