Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756278Ab2FFOoo (ORCPT ); Wed, 6 Jun 2012 10:44:44 -0400 Received: from e37.co.us.ibm.com ([32.97.110.158]:56467 "EHLO e37.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753886Ab2FFOok (ORCPT ); Wed, 6 Jun 2012 10:44:40 -0400 Date: Wed, 6 Jun 2012 07:44:17 -0700 From: "Paul E. McKenney" To: Peter Zijlstra Cc: Thomas Gleixner , "Luck, Tony" , "Yu, Fenghua" , Rusty Russell , Ingo Molnar , H Peter Anvin , "Siddha, Suresh B" , "Mallick, Asit K" , Arjan Dan De Ven , linux-kernel , x86 , linux-pm , "Srivatsa S. Bhat" Subject: Re: [PATCH 0/6] x86/cpu hotplug: Wake up offline CPU via mwait or nmi Message-ID: <20120606144417.GH19601@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <3E5A0FA7E9CA944F9D5414FEC6C7122007728081@ORSMSX105.amr.corp.intel.com> <1338913190.2749.10.camel@twins> <3908561D78D1C84285E8C5FCA982C28F19300965@ORSMSX104.amr.corp.intel.com> <1338918625.2749.29.camel@twins> <1338925756.2749.36.camel@twins> <1338931856.2749.57.camel@twins> <20120605221240.GW2388@linux.vnet.ibm.com> <1338972175.2749.78.camel@twins> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1338972175.2749.78.camel@twins> User-Agent: Mutt/1.5.21 (2010-09-15) X-Content-Scanned: Fidelis XPS MAILER x-cbid: 12060614-7408-0000-0000-000005A084AD Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1527 Lines: 33 On Wed, Jun 06, 2012 at 10:42:55AM +0200, Peter Zijlstra wrote: > On Tue, 2012-06-05 at 15:12 -0700, Paul E. McKenney wrote: > > > RCU has similar nasties. > > > > I am working to rid RCU of this sort of thing. I have rcu_barrier() so > > that it avoids messing with CPUs that don't have callbacks, which will > > be almost all of the idle CPUs, especially for CONFIG_RCU_FAST_NO_HZ=y. > > I believe that I have also removed all of RCU's dependencies on CPU > > hotplug's using kstopmachine, though Murphy would say otherwise. > > > > I still need to fix up synchronize_sched_expedited(), but that is on > > the list. I considered getting rid of this one, but I am probably going > > to have to make synchronize_sched() map to it during boot time to keep > > the boot-speed demons satisfied. > > Not the point really. Its perfectly fine for applications in an > 'isolated' set to use system calls, hence they get to participate in RCU > state. > > I don't think the isolation means userspace while(1) applications is > interesting. Sure, some people do this, and we should dtrt for them, but > the far more interesting case is 'regular' applications that do use > system calls. OK, I will bite. What are the semantics/properties for your isolated set? Thanx, Paul -- 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/