Return-path: Received: from emh02.mail.saunalahti.fi ([62.142.5.108]:51681 "EHLO emh02.mail.saunalahti.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932125AbaAWGfl (ORCPT ); Thu, 23 Jan 2014 01:35:41 -0500 Message-ID: <1390458939.4189.50.camel@porter.coelho.fi> (sfid-20140123_073558_671403_3AC7F355) Subject: Re: [PATCH 5/7] mac80211: improve CSA locking From: Luca Coelho To: Michal Kazior Cc: Johannes Berg , linux-wireless Date: Thu, 23 Jan 2014 08:35:39 +0200 In-Reply-To: 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> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Sender: linux-wireless-owner@vger.kernel.org List-ID: 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... -- Luca.