From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754458Ab2AaNkb (ORCPT ); Tue, 31 Jan 2012 08:40:31 -0500 Received: from casper.infradead.org ([85.118.1.10]:51752 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753024Ab2AaNkX (ORCPT ); Tue, 31 Jan 2012 08:40:23 -0500 Date: Tue, 31 Jan 2012 05:41:55 -0800 From: Arjan van de Ven To: Ingo Molnar Cc: linux-kernel@vger.kernel.org, Milton Miller , Andrew Morton , arjanvandeven@gmail.com, Linus Torvalds , Peter Zijlstra , Thomas Gleixner , "H. Peter Anvin" Subject: Re: smp: Start up non-boot CPUs asynchronously Message-ID: <20120131054155.371e8307@infradead.org> In-Reply-To: <20120131125232.GD4408@elte.hu> References: <20120130205444.22f5e26a@infradead.org> <20120131125232.GD4408@elte.hu> Organization: Intel X-Mailer: Claws Mail 3.7.9 (GTK+ 2.24.7; i386-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-SRS-Rewrite: SMTP reverse-path rewritten from by casper.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 31 Jan 2012 13:52:32 +0100 Ingo Molnar wrote: > > The real fix would be to make the init code depend less on each > other, i.e. have less hotplug lock dependencies. Or, if it's > such a hot lock for a good reason, why does spinning on it slow > down the boot process? It really shouldnt. by inspection, anything that calls get_online_cpus()/put_online_cpus() will block while a CPU is coming up. This is used in things like kmem_cache_create()... which is used about everywhere. (there's various other places... more or less it's a requirement for using the for_each_online_cpu() api correctly) -- Arjan van de Ven Intel Open Source Technology Centre For development, discussion and tips for power savings, visit http://www.lesswatts.org