From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755314Ab1IMQEg (ORCPT ); Tue, 13 Sep 2011 12:04:36 -0400 Received: from mailout-de.gmx.net ([213.165.64.22]:58987 "HELO mailout-de.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1755274Ab1IMQEd (ORCPT ); Tue, 13 Sep 2011 12:04:33 -0400 X-Authenticated: #14349625 X-Provags-ID: V01U2FsdGVkX197E54segF7h9FD1Pqdm9oSX/Pfs8KTfHiLQe8P5y nak9ha2/XiSO3e Subject: Re: [PATCH tip/core/rcu 44/55] rcu: wire up RCU_BOOST_PRIO for rcutree From: Mike Galbraith To: paulmck@linux.vnet.ibm.com Cc: linux-kernel@vger.kernel.org, mingo@elte.hu, laijs@cn.fujitsu.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@polymtl.ca, josh@joshtriplett.org, niv@us.ibm.com, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, Valdis.Kletnieks@vt.edu, dhowells@redhat.com, eric.dumazet@gmail.com, darren@dvhart.com, patches@linaro.org In-Reply-To: <20110913153413.GB2416@linux.vnet.ibm.com> References: <20110906180015.GA2560@linux.vnet.ibm.com> <1315332049-2604-44-git-send-email-paulmck@linux.vnet.ibm.com> <1315915334.6300.15.camel@marge.simson.net> <20110913153413.GB2416@linux.vnet.ibm.com> Content-Type: text/plain; charset="UTF-8" Date: Tue, 13 Sep 2011 18:04:18 +0200 Message-ID: <1315929858.6312.16.camel@marge.simson.net> Mime-Version: 1.0 X-Mailer: Evolution 2.32.1 Content-Transfer-Encoding: 7bit X-Y-GMX-Trusted: 0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2011-09-13 at 08:34 -0700, Paul E. McKenney wrote: > On Tue, Sep 13, 2011 at 02:02:14PM +0200, Mike Galbraith wrote: > > @@ -1608,7 +1618,7 @@ static int rcu_node_kthread(void *arg) > > continue; > > } > > per_cpu(rcu_cpu_has_work, cpu) = 1; > > - sp.sched_priority = RCU_KTHREAD_PRIO; > > + sp.sched_priority = current->rt_priority; > > This is broken -- the per-node kthread runs at RT prio 99, but we usually > would not want to boost that high. Ouch, right. My userland sets things on boot, so it works. > Seems like we should have a global variable that tracks the current > priority. This global variable could then be set in a manner similar > to the softirq priorities -- or, perhaps better, simply set whenever > the softirq priority is changed. > > Thoughts? RCU threads would have to constantly watch for user priority changes on their own, and update private data methinks. -Mike