From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753257AbYIJJPb (ORCPT ); Wed, 10 Sep 2008 05:15:31 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751584AbYIJJPX (ORCPT ); Wed, 10 Sep 2008 05:15:23 -0400 Received: from mga10.intel.com ([192.55.52.92]:41425 "EHLO fmsmga102.fm.intel.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751501AbYIJJPX (ORCPT ); Wed, 10 Sep 2008 05:15:23 -0400 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.32,371,1217833200"; d="scan'208";a="378687643" Subject: Re: [BUG] 2.6.27-rc5 couldn't boot on tulsa machine randomly From: "Zhang, Yanmin" To: Peter Zijlstra Cc: Ingo Molnar , LKML In-Reply-To: <1220930793.25574.20.camel@ymzhang> References: <1220930793.25574.20.camel@ymzhang> Content-Type: text/plain; charset=UTF-8 Date: Wed, 10 Sep 2008 17:12:58 +0800 Message-Id: <1221037978.25574.22.camel@ymzhang> Mime-Version: 1.0 X-Mailer: Evolution 2.21.5 (2.21.5-2.fc9) Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2008-09-09 at 11:26 +0800, Zhang, Yanmin wrote: > On my tulsa x86-64 machine, kernel 2.6.25-rc5 couldn't boot randomly. > > Basically, function __enable_runtime forgets to reset rt_rq->rt_throttled to 0. Peter, Is there any issue with the patch? I tested 2.6.27-rc6 and it still couldn't boot on my tulsa machine. With my patch, kernel could boot. Yanmin > When every cpu is up, per-cpu migration_thread is created and it runs very fast, > sometimes to mark the corresponding rt_rq->rt_throttled to 1 very quickly. After > all cpus are up, with below calling chain, > sched_init_smp => arch_init_sched_domains => build_sched_domains => ... > => cpu_attach_domain => rq_attach_root => set_rq_online => ... => __enable_runtime, > __enable_runtime is called against every rt_rq again, so rt_rq->rt_time is reset to > 0, but rt_rq->rt_throttled might be still 1. Later on function do_sched_rt_period_timer > couldn't reset it, and all RT tasks couldn't be scheduled to run on that cpu. > here is RT task migration_thread which is woken up when a task is migrated to another cpu. > > Below patch fixes it against 2.6.27-rc5. > > Signed-off-by: Zhang Yanmin > > --- > > diff -Nraup linux-2.6.27-rc5/kernel/sched_rt.c linux-2.6.27-rc5_fix/kernel/sched_rt.c > --- linux-2.6.27-rc5/kernel/sched_rt.c 2008-09-09 11:06:43.000000000 +0800 > +++ linux-2.6.27-rc5_fix/kernel/sched_rt.c 2008-09-09 11:13:04.000000000 +0800 > @@ -350,6 +350,7 @@ static void __enable_runtime(struct rq * > spin_lock(&rt_rq->rt_runtime_lock); > rt_rq->rt_runtime = rt_b->rt_runtime; > rt_rq->rt_time = 0; > + rt_rq->rt_throttled = 0; > spin_unlock(&rt_rq->rt_runtime_lock); > spin_unlock(&rt_b->rt_runtime_lock); > } > > > -- > 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/