Return-path: Received: from mail-bk0-f44.google.com ([209.85.214.44]:55962 "EHLO mail-bk0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753305AbaAWGlJ convert rfc822-to-8bit (ORCPT ); Thu, 23 Jan 2014 01:41:09 -0500 Received: by mail-bk0-f44.google.com with SMTP id mz12so204722bkb.17 for ; Wed, 22 Jan 2014 22:41:08 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <1390458664.4189.48.camel@porter.coelho.fi> References: <1390227670-19030-1-git-send-email-michal.kazior@tieto.com> <1390227670-19030-6-git-send-email-michal.kazior@tieto.com> <1390316761.6199.27.camel@jlt4.sipsolutions.net> <1390380726.4334.4.camel@jlt4.sipsolutions.net> <1390382020.4334.17.camel@jlt4.sipsolutions.net> <1390385995.4334.27.camel@jlt4.sipsolutions.net> <1390394166.4189.28.camel@porter.coelho.fi> <1390403432.4334.33.camel@jlt4.sipsolutions.net> <1390403634.4189.39.camel@porter.coelho.fi> <1390458664.4189.48.camel@porter.coelho.fi> Date: Thu, 23 Jan 2014 07:41:08 +0100 Message-ID: (sfid-20140123_074114_128616_86274C66) Subject: Re: [PATCH 5/7] mac80211: improve CSA locking From: Michal Kazior To: Luca Coelho Cc: Johannes Berg , linux-wireless Content-Type: text/plain; charset=UTF-8 Sender: linux-wireless-owner@vger.kernel.org List-ID: On 23 January 2014 07:31, Luca Coelho wrote: > On Thu, 2014-01-23 at 07:22 +0100, Michal Kazior wrote: >> On 22 January 2014 16:13, Luca Coelho wrote: >> > On Wed, 2014-01-22 at 16:10 +0100, Johannes Berg wrote: >> >> On Wed, 2014-01-22 at 14:36 +0200, Luca Coelho wrote: >> >> >> >> > I don't think we should try to merge the channel switches. We should >> >> > just perform them separately, especially because the exact time of the >> >> > switch will most likely not be the same (since the TBTTs are not in >> >> > sync). >> >> >> >> Do you mean that we shouldn't even have all that new API to switch >> >> multiple interfaces simultaneously? >> > >> > Right, I'm not really sure it's necessary. PErhaps with non-chanctx we >> > need something like that, but maybe it would still be better not to do >> > this in the nl80211 API, but sync/merge in cfg80211/mac80211? >> >> I was thinking about it. This should work, mostly, as long as you're >> able to submit CSA requests fast enough and you don't use count 0 or >> 1, in which case it becomes racy. > > CSA with count 0 or 1 are really tricky in many respects. But still I > don't see why it would get racy. The interfaces will switch > independently, making their own chanctx reservations and so on... You can't really switch multiple interfaces independently with a single-channel hardware. You'll either end up with some interfaces disconnected or dragged to a different channel forcefully. Michał