Return-path: Received: from mail-ob0-f178.google.com ([209.85.214.178]:44345 "EHLO mail-ob0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750827AbaCXGhe convert rfc822-to-8bit (ORCPT ); Mon, 24 Mar 2014 02:37:34 -0400 Received: by mail-ob0-f178.google.com with SMTP id wp18so5220487obc.37 for ; Sun, 23 Mar 2014 23:37:33 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <1395414428.4164.16.camel@jlt4.sipsolutions.net> References: <1395410520-26939-1-git-send-email-michal.kazior@tieto.com> <1395411440.4164.15.camel@jlt4.sipsolutions.net> <1395414428.4164.16.camel@jlt4.sipsolutions.net> Date: Mon, 24 Mar 2014 07:37:33 +0100 Message-ID: (sfid-20140324_073737_822173_2E8BEE3C) Subject: Re: [PATCH] ath10k: dont call csa_finish more than once From: Michal Kazior To: Johannes Berg Cc: "ath10k@lists.infradead.org" , linux-wireless Content-Type: text/plain; charset=UTF-8 Sender: linux-wireless-owner@vger.kernel.org List-ID: On 21 March 2014 16:07, Johannes Berg wrote: > On Fri, 2014-03-21 at 15:58 +0100, Michal Kazior wrote: > >> > Didn't we have this discussion on the hwsim patch before? >> >> Oh. I'm not aware of the discussion. Probably missed it. > > Or I got it wrong :) > >> > I'd argue that if all drivers must track this, then the mac80211 API is >> > defective. >> >> I can make this a mac80211 patch then? > > Yeah I guess. What was the reason for this though? Here it's multi-vif? > Before I think we were talking about races? Before multi-vif if ieee80211_csa_finalize() failed and left csa_active==true driver could end up poking the csa_finalize_work() over and over again I guess? For multi-vif csa using reservation there are 2 reasons: a) channel switches across interfaces may not be tightly synchronized. I did tests where 2 long (cs_count=100) channel switches were a few seconds apart. In that case driver poked csa_finalize work quite a lot resulting in a mess. b) my current approach has the following flow: 1. reserve_chanctx() 2. (some time later) driver calls csa_finish, and csa_finalize calls use_reserved_chanctx() because reserved_chanctx is set 3. (possibly some time later, for multi-vif reservations) csa_finalize is called again but this time without reserved_chanctx, so it verifies if bss_conf.chandef is csa_chandef (after successful reservation it should be). This means if driver would poke csa_finalize() more than once then use_reserved_chanctx() would be called again and again as a result. Michał