From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nicholas Mc Guire Subject: Re: [PATCH]sched/rt: Do not try to push tasks if pinned task switches to RT Date: Wed, 12 Mar 2014 11:39:42 +0100 Message-ID: <20140312103942.GB5321@opentech.at> References: <4451359470707@web16g.yandex.ru> <20140312061833.3a43aa64@gandalf.local.home> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Peter Zijlstra , Kirill Tkhai , linux-kernel@vger.kernel.org, Ingo Molnar , linux-rt-users To: Steven Rostedt Return-path: Content-Disposition: inline In-Reply-To: <20140312061833.3a43aa64@gandalf.local.home> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-rt-users.vger.kernel.org On Wed, 12 Mar 2014, Steven Rostedt wrote: > Peter, > > I'm going through my inbox (over a year old), and found this patch from > Kirill. It looks fine to me. You can apply it with my > > Acked-by: Steven Rostedt > > -- Steve > > [PATCH]sched/rt: Do not try to push tasks if pinned task switches to RT > > Just switched pinned task is not able to be pushed. If the rq had had > several RT tasks before they have already been considered as candidates > to be pushed (or pulled). > > Signed-off-by: Kirill V Tkhai > CC: Steven Rostedt > CC: Ingo Molnar > CC: Peter Zijlstra > CC: linux-rt-users > --- > kernel/sched/rt.c | 4 ++-- > 1 files changed, 2 insertions(+), 2 deletions(-) > diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c > index 4e8f0f4..5aab032 100644 > --- a/kernel/sched/rt.c > +++ b/kernel/sched/rt.c > @@ -1925,9 +1925,9 @@ static void switched_to_rt(struct rq *rq, struct task_struct *p) > */ > if (p->on_rq && rq->curr != p) { > #ifdef CONFIG_SMP > - if (rq->rt.overloaded && push_rt_task(rq) && > + if (p->nr_cpus_allowed > 1 && rq->rt.overloaded && > /* Don't resched if we changed runqueues */ > - rq != task_rq(p)) > + push_rt_task(rq) && rq != task_rq(p)) > check_resched = 0; > #endif /* CONFIG_SMP */ > if (check_resched && p->prio < rq->curr->prio) would there not need to be a check for p->migrate_disable ? push_rt_task() is not checking and so a high prio RT task preemting a low prio RT task in a migrate_disable() section would actually push it off this cpu ? atleast I did not find why that would not happen. thx! hofrat