Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757908AbYB0NZ1 (ORCPT ); Wed, 27 Feb 2008 08:25:27 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756903AbYB0NZM (ORCPT ); Wed, 27 Feb 2008 08:25:12 -0500 Received: from e28smtp02.in.ibm.com ([59.145.155.2]:39481 "EHLO e28esmtp02.in.ibm.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1756898AbYB0NZK (ORCPT ); Wed, 27 Feb 2008 08:25:10 -0500 Date: Wed, 27 Feb 2008 18:54:59 +0530 From: Dhaval Giani To: Peter Zijlstra Cc: Ingo Molnar , Sudhir Kumar , Balbir Singh , Aneesh Kumar KV , Srivatsa Vaddagiri , lkml Subject: Re: [PATCH] sched: don't allow rt_runtime_us to be zero for groups having rt tasks Message-ID: <20080227132459.GE15731@linux.vnet.ibm.com> Reply-To: Dhaval Giani References: <20080227110829.GA15731@linux.vnet.ibm.com> <1204116417.6242.383.camel@lappy> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1204116417.6242.383.camel@lappy> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2558 Lines: 87 On Wed, Feb 27, 2008 at 01:46:56PM +0100, Peter Zijlstra wrote: > > On Wed, 2008-02-27 at 16:38 +0530, Dhaval Giani wrote: > > This patch checks if we can set the rt_runtime_us to 0. If there is a > > realtime task in the group, we don't want to set the rt_runtime_us to 0 > > otherwise bad things will happen. > > I had considered this a: don't do that then, thing. But sure, helping > the admin seems like a valid option. > Well, if it can be done, it shall be done :) > > > + err = -EINVAL; > > -EBUSY perhaps? > Well, the group is certainly not busy. I will go with invalid as it is definitly an invalid value when the groups have rt tasks. But if someone disagrees, I have no issue with it being something else. Corrected patch as follows, -- This patch checks if we can set the rt_runtime_us to 0. If there is a realtime task in the group, we don't want to set the rt_runtime_us as 0 or bad things will happen. Signed-off-by: Dhaval Giani --- kernel/sched.c | 17 +++++++++++++++++ 1 files changed, 17 insertions(+) Index: linux-2.6.25-rc3/kernel/sched.c =================================================================== --- linux-2.6.25-rc3.orig/kernel/sched.c +++ linux-2.6.25-rc3/kernel/sched.c @@ -7960,6 +7960,17 @@ static int __rt_schedulable(struct task_ return total + to_ratio(period, runtime) < global_ratio; } +/* Must be called with tasklist_lock held */ +static inline int tg_has_rt_tasks(struct task_group *tg) +{ + struct task_struct *p; + for_each_process(p) { + if (rt_task(p) && rt_rq_of_se(&p->rt)->tg == tg) + return 1; + } + return 0; +} + int sched_group_set_rt_runtime(struct task_group *tg, long rt_runtime_us) { u64 rt_runtime, rt_period; @@ -7971,6 +7982,11 @@ int sched_group_set_rt_runtime(struct ta rt_runtime = rt_period; mutex_lock(&rt_constraints_mutex); + read_lock(&tasklist_lock); + if (rt_runtime_us == 0 && tg_has_rt_tasks(tg)) { + err = -EINVAL; + goto unlock; + } if (!__rt_schedulable(tg, rt_period, rt_runtime)) { err = -EINVAL; goto unlock; @@ -7979,6 +7995,7 @@ int sched_group_set_rt_runtime(struct ta rt_runtime = RUNTIME_INF; tg->rt_runtime = rt_runtime; unlock: + read_unlock(&tasklist_lock); mutex_unlock(&rt_constraints_mutex); return err; -- regards, Dhaval -- 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/