From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754762Ab3EMKgE (ORCPT ); Mon, 13 May 2013 06:36:04 -0400 Received: from www.linutronix.de ([62.245.132.108]:46976 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753327Ab3EMKgC (ORCPT ); Mon, 13 May 2013 06:36:02 -0400 Date: Mon, 13 May 2013 12:35:30 +0200 (CEST) From: Thomas Gleixner To: Viresh Kumar cc: Steven Rostedt , pjt@google.com, paul.mckenney@linaro.org, tj@kernel.org, mingo@redhat.com, peterz@infradead.org, Arvind.Chauhan@arm.com, linaro-dev@lists.linaro.org, patches@linaro.org, pdsw-power-team@arm.com, linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org, john stultz Subject: Re: [PATCH V2 Resend 4/4] timer: Migrate running timer In-Reply-To: Message-ID: References: <1354024039.6276.72.camel@gandalf.local.home> User-Agent: Alpine 2.02 (LFD 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 13 May 2013, Viresh Kumar wrote: > On 24 April 2013 16:52, Viresh Kumar wrote: > > On 9 April 2013 20:22, Viresh Kumar wrote: > >> [Steven replied to a personal Ping!!, including everybody again] > >> > >> On 9 April 2013 19:25, Steven Rostedt wrote: > >>> On Tue, 2013-04-09 at 14:05 +0530, Viresh Kumar wrote: > >>>> Ping!! > >>>> > >>> > >>> Remind me again. What problem are you trying to solve? > >> > >> I was trying to migrate a running timer which arms itself, so that we don't > >> keep a cpu busy just for servicing this timer. Which mechanism is migrating the timer away? > >>>> On 20 March 2013 20:43, Viresh Kumar wrote: > >>>> > > >>>> > Hi Steven/Thomas, > >>>> > > >>>> > I came back to this patch after completing some other stuff and posting > >>>> > wq part of this patchset separately. > >>>> > > >>>> > I got your point and understand how this would fail. > >>>> > > >>>> > @Thomas: I need your opinion first. Do you like this concept of migrating > >>>> > running timer or not? Or you see some basic problem with this concept? I have no objections to the functionality per se, but the proposed solution is not going to fly. Aside of bloating the data structure you're changing the semantics of __mod_timer(). No __mod_timer() caller can deal with -EBUSY. So you'd break the world and some more. Here is a list of questions: - Which mechanism migrates timers? - How is that mechanism triggered? - How does that deal with CPU bound timers? Thanks, tglx