Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752673AbcLFIfx (ORCPT ); Tue, 6 Dec 2016 03:35:53 -0500 Received: from bombadil.infradead.org ([198.137.202.9]:55946 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751609AbcLFIfv (ORCPT ); Tue, 6 Dec 2016 03:35:51 -0500 Date: Tue, 6 Dec 2016 09:35:01 +0100 From: Peter Zijlstra To: luca abeni Cc: Steven Rostedt , Daniel Bristot de Oliveira , linux-kernel@vger.kernel.org, Ingo Molnar , Juri Lelli , Claudio Scordino Subject: Re: [RFC v3 1/6] Track the active utilisation Message-ID: <20161206083501.GW3092@twins.programming.kicks-ass.net> References: <1477317998-7487-1-git-send-email-luca.abeni@unitn.it> <1477317998-7487-2-git-send-email-luca.abeni@unitn.it> <20161025112916.67eb245c@utopia> <20161025095811.50a5856a@gandalf.local.home> <20161118142359.GK3142@twins.programming.kicks-ass.net> <20161205233005.54275bd6@sweethome> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20161205233005.54275bd6@sweethome> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1476 Lines: 42 On Mon, Dec 05, 2016 at 11:30:05PM +0100, luca abeni wrote: > Hi Peter, > > On Fri, 18 Nov 2016 15:23:59 +0100 > Peter Zijlstra wrote: > [...] > > u64 running_bw; > > > > static void add_running_bw(struct sched_dl_entity *dl_se, struct > > dl_rq *dl_rq) { > > u64 old = dl_rq->running_bw; > > > > dl_rq->running_bw += dl_se->dl_bw; > > SCHED_WARN_ON(dl_rq->running_bw < old); /* overflow */ > > } > > > > static void sub_running_bw(struct sched_dl_entity *dl_se, struct > > dl_rq *dl_rq) { > > u64 old = dl_rq->running_bw; > > > > dl_rq->running_bw -= dl_se->dl_bw; > > SCHED_WARN_ON(dl_rq->running_bw > old); /* underflow */ > > } > > I wanted to change "SCHED_WARN_ON(dl_rq->running_bw > old); /* > underflow */" into "if (SCHED_WARN_ON(...)) dl_rq->running_bw = 0" (to > avoid using nonsensical "running_bw" values), but I see that > "SCHED_WARN_ON()" cannot be used inside an if (this seems to be a > difference respect to "SCHED_WARN()"). There's a SCHED_WARN? Did you mean to say WARN_ON()? And yes, mostly by accident I think, I'm not a big user of that pattern and neglected it when I did SCHED_WARN_ON(). > This is because of the definition used when CONFIG_SCHED_DEBUG is not > defined (I noticed the issue when testing with random kernel > configurations). I'm fine changing the definition, just find something that works. The current ((void)(x)) thing was to avoid unused complaints -- although I'm not sure there were any.