Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753877AbWKREx3 (ORCPT ); Fri, 17 Nov 2006 23:53:29 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753882AbWKREx3 (ORCPT ); Fri, 17 Nov 2006 23:53:29 -0500 Received: from smtp.osdl.org ([65.172.181.25]:60114 "EHLO smtp.osdl.org") by vger.kernel.org with ESMTP id S1753877AbWKREx2 (ORCPT ); Fri, 17 Nov 2006 23:53:28 -0500 Date: Fri, 17 Nov 2006 20:51:03 -0800 From: Andrew Morton To: Alan Stern Cc: "Paul E. McKenney" , Jens Axboe , Linus Torvalds , Thomas Gleixner , Ingo Molnar , LKML , john stultz , David Miller , Arjan van de Ven , Andi Kleen , , Subject: Re: [patch] cpufreq: mark cpufreq_tsc() as core_initcall_sync Message-Id: <20061117205103.847081a4.akpm@osdl.org> In-Reply-To: References: <20061118003859.GG2632@us.ibm.com> X-Mailer: Sylpheed version 2.2.7 (GTK+ 2.8.17; x86_64-unknown-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1742 Lines: 43 On Fri, 17 Nov 2006 23:33:45 -0500 (EST) Alan Stern wrote: > On Fri, 17 Nov 2006, Paul E. McKenney wrote: > > > > Perhaps a better approach to the initialization problem would be to assume > > > that either: > > > > > > 1. The srcu_struct will be initialized before it is used, or > > > > > > 2. When it is used before initialization, the system is running > > > only one thread. > > > > Are these assumptions valid? If so, they would indeed simplify things > > a bit. > > I don't know. Maybe Andrew can tell us -- is it true that the kernel runs > only one thread up through the time the core_initcalls are finished? I don't see why - a core_initcall could go off and do the multithreaded-pci-probing thing, or it could call kernel_thread() or anything. I doubt if any core_initcall functions _do_ do that, but there are a lot of them. > If not, can we create another initcall level that is guaranteed to run > before any threads are spawned? It's a simple and cheap matter to create a precore_initcall() - one would need to document it carefully to be able to preserve whatever guarantees it needs. However by the time the initcalls get run, various thing are already happening: SMP is up, the keventd threads are running, the CPU scheduler migration threads are running, ksoftirqd, softlockup-detector, etc. keventd is the problematic one. So I guess you'd need a new linker section and a call from do_pre_smp_initcalls() or thereabouts. - 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/