Return-path: Received: from he.sipsolutions.net ([78.46.109.217]:40844 "EHLO sipsolutions.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751887Ab0FIM1Z (ORCPT ); Wed, 9 Jun 2010 08:27:25 -0400 Subject: Re: [RFC PATCH 1/2] mac80211: make max_network_latency notifier atomic safe From: Johannes Berg To: Florian Mickler Cc: pm list , james.bottomley@suse.de, markgross@thegnar.org, mgross@linux.intel.com, "John W. Linville" , "David S. Miller" , Javier Cardona , Jouni Malinen , Rui Paulo , Kalle Valo , linux-wireless@vger.kernel.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, Thomas Gleixner In-Reply-To: <20100609141643.14e9aedc@schatten.dmk.lab> References: <1276074915-26879-1-git-send-email-florian@mickler.org> <1276076287.3727.15.camel@jlt3.sipsolutions.net> <20100609122050.1dd18132@schatten.dmk.lab> <1276080128.14580.5.camel@jlt3.sipsolutions.net> <20100609141643.14e9aedc@schatten.dmk.lab> Content-Type: text/plain; charset="UTF-8" Date: Wed, 09 Jun 2010 14:27:05 +0200 Message-ID: <1276086425.14580.14.camel@jlt3.sipsolutions.net> Mime-Version: 1.0 Sender: linux-wireless-owner@vger.kernel.org List-ID: On Wed, 2010-06-09 at 14:16 +0200, Florian Mickler wrote: > That was also my first idea, but then I thought about qos and thought > atomic notification are necessary. > Do you see any value in having atomic notification? > > I have the following situation before my eyes: > > Driver A gets an interrupt and needs (to service that > interrupt) the cpu to guarantee a latency of X because the > device is a bit icky. > > Now, in that situation, if we don't immediately (without scheduling in > between) notify the system to be in that latency-mode the driver won't > function properly. Is this a realistic scene? > > At the moment we only have process context notification and only 2 > listeners. > > I think providing for atomic as well as "relaxed" notification could be > useful. > > If atomic notification is deemed unnecessary, I have no > problems to just use schedule_work() in update request. > Anyway, it is probably best to split this. I.e. first make > update_request callable from atomic contexts with doing the > schedule_work in update_request and then > as an add on provide for constraints_objects with atomic notifications. Well I remember http://thread.gmane.org/gmane.linux.kernel/979935 where Mark renamed things to "request" which seems to imply to me more of a "please do this" than "I NEED IT NOW!!!!!". johannes