Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752960AbaBSIqZ (ORCPT ); Wed, 19 Feb 2014 03:46:25 -0500 Received: from merlin.infradead.org ([205.233.59.134]:49468 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752168AbaBSIqY (ORCPT ); Wed, 19 Feb 2014 03:46:24 -0500 Date: Wed, 19 Feb 2014 09:46:18 +0100 From: Peter Zijlstra To: Steven Rostedt Cc: Juri Lelli , LKML , Linus Torvalds , Ingo Molnar , Thomas Gleixner , Andrew Morton Subject: Re: [PATCH v3] sched/deadline: Fix bad accounting of nr_running Message-ID: <20140219084618.GF27965@twins.programming.kicks-ass.net> References: <20140214235946.60a89b65@gandalf.local.home> <53022F2D.8040301@gmail.com> <20140218215012.209059c0@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140218215012.209059c0@gandalf.local.home> User-Agent: Mutt/1.5.21 (2012-12-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 18, 2014 at 09:50:12PM -0500, Steven Rostedt wrote: > > > Rationale for this odd behavior is that, when a task is throttled, it > > is removed only from the dl_rq, but we keep it on_rq (as this is not > > a "full dequeue", that is the task is not actually sleeping). But, it > > is also true that, while throttled a task behaves like it is sleeping > > (e.g., its timer will fire on a new CPU if the old one is dead). So, > > Steven's fix sounds also semantically correct. > > Actually, it seems that I was hitting it again, but this time getting a > negative number. OK, after looking at the code a bit more, I think we > should update the runqueue nr_running only when the task is officially > enqueued and dequeued, and all accounting within, will not touch that > number. But if the task is throttled it should still very much decrement the number. There's places that very much rely on nr_running be exactly the number of runnable tasks. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/