Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754133AbZIWGcv (ORCPT ); Wed, 23 Sep 2009 02:32:51 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753927AbZIWGcu (ORCPT ); Wed, 23 Sep 2009 02:32:50 -0400 Received: from viefep19-int.chello.at ([62.179.121.39]:58009 "EHLO viefep19-int.chello.at" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753787AbZIWGcu (ORCPT ); Wed, 23 Sep 2009 02:32:50 -0400 X-SourceIP: 213.93.53.227 Subject: Re: [PATCH] sched: Make sure task has correct sched_class after policy change From: Peter Zijlstra To: Peter Williams Cc: Ingo Molnar , Mike Galbraith , Linux Kernel Mailing In-Reply-To: References: Content-Type: text/plain Date: Wed, 23 Sep 2009 08:32:59 +0200 Message-Id: <1253687579.7695.89.camel@twins> Mime-Version: 1.0 X-Mailer: Evolution 2.26.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1729 Lines: 59 On Wed, 2009-09-23 at 02:21 +0000, Peter Williams wrote: > From the code in rt_mutex_setprio(), it is evident that the intention > is that task's with a RT 'prio' value as a consequence of receiving a PI > boost also have their 'sched_class' field set to '&rt_sched_class'. > However, the code in __setscheduler() could result in this intention > being frustrated. > > This patch fixes this problem. > > Signed-off-by: Peter Williams I think you're right, but the problem seems to be that it sets sched_class based on policy, which seems fragile in the face of PI. How about the alternative below? --- kernel/sched.c | 17 ++++------------- 1 files changed, 4 insertions(+), 13 deletions(-) diff --git a/kernel/sched.c b/kernel/sched.c index 91843ba..753a52c 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -6129,23 +6129,14 @@ __setscheduler(struct rq *rq, struct task_struct *p, int policy, int prio) { BUG_ON(p->se.on_rq); - p->policy = policy; - switch (p->policy) { - case SCHED_NORMAL: - case SCHED_BATCH: - case SCHED_IDLE: - p->sched_class = &fair_sched_class; - break; - case SCHED_FIFO: - case SCHED_RR: - p->sched_class = &rt_sched_class; - break; - } - p->rt_priority = prio; p->normal_prio = normal_prio(p); /* we are holding p->pi_lock already */ p->prio = rt_mutex_getprio(p); + if (rt_prio(p->prio)) + p->sched_class = &rt_sched_class; + else + p->sched_class = &fair_sched_class; set_load_weight(p); } -- 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/