From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752128AbbHJMOP (ORCPT ); Mon, 10 Aug 2015 08:14:15 -0400 Received: from casper.infradead.org ([85.118.1.10]:37761 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750965AbbHJMOK (ORCPT ); Mon, 10 Aug 2015 08:14:10 -0400 Date: Mon, 10 Aug 2015 14:14:07 +0200 From: Peter Zijlstra To: byungchul.park@lge.com Cc: mingo@kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] sched: ensure a task has a non-normalized vruntime when returning back to cfs Message-ID: <20150810121407.GB16853@twins.programming.kicks-ass.net> References: <1439197375-27927-1-git-send-email-byungchul.park@lge.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1439197375-27927-1-git-send-email-byungchul.park@lge.com> 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 Mon, Aug 10, 2015 at 06:02:55PM +0900, byungchul.park@lge.com wrote: > From: Byungchul Park > > current code ensures a task has a normalized vruntime when switching off > from fair class, but it does not ensure the task has a non-normalized > vruntime when switching back to the fair class. > > this is an example breaking this consistency. > > 1. a task is in fair class and !queue > 2. change its class to rt class (still !queue) > 3. change its class to fair class again (stll !queue) Just curious, did you manage to trigger this in practise or did you find it through code inspection only?