Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932359AbVISHhS (ORCPT ); Mon, 19 Sep 2005 03:37:18 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932360AbVISHhS (ORCPT ); Mon, 19 Sep 2005 03:37:18 -0400 Received: from smtp204.mail.sc5.yahoo.com ([216.136.130.127]:49291 "HELO smtp204.mail.sc5.yahoo.com") by vger.kernel.org with SMTP id S932359AbVISHhQ (ORCPT ); Mon, 19 Sep 2005 03:37:16 -0400 DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=s1024; d=yahoo.com.au; h=Received:Subject:From:To:Cc:In-Reply-To:References:Content-Type:Date:Message-Id:Mime-Version:X-Mailer:Content-Transfer-Encoding; b=oaUoM0R7nkmprJL3BcSpleeABs880AO653khDife9zyVv2TChet/LNEiDqbLfROho7b2IOigWnj/2K9FifltoyJEARUki11rsA/LoPYLcH9HavfGsJG0bwF8QTsfep3EbJiJcR9G6ZnCKW5xuVd708dyb3unl/Erwu0xRgzosOo= ; Subject: Re: PATCH: Fix race in cpu_down (hotplug cpu) From: Nick Piggin To: Ingo Molnar Cc: Shaohua Li , vatsa@in.ibm.com, Nigel Cunningham , Andrew Morton , Linus Torvalds , Zwane Mwaikambo , lkml , Rusty Russell In-Reply-To: <20050919072842.GA11293@elte.hu> References: <59D45D057E9702469E5775CBB56411F171F7E0@pdsmsx406> <20050919051024.GA8653@in.ibm.com> <1127107887.3958.9.camel@linux-hp.sh.intel.com> <20050919055715.GE8653@in.ibm.com> <1127110271.9696.97.camel@localhost> <20050919062336.GA9466@in.ibm.com> <1127111830.4087.3.camel@linux-hp.sh.intel.com> <1127111784.5272.10.camel@npiggin-nld.site> <1127113930.4087.6.camel@linux-hp.sh.intel.com> <1127114538.5272.16.camel@npiggin-nld.site> <20050919072842.GA11293@elte.hu> Content-Type: text/plain Date: Mon, 19 Sep 2005 17:37:05 +1000 Message-Id: <1127115425.5272.21.camel@npiggin-nld.site> Mime-Version: 1.0 X-Mailer: Evolution 2.0.1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1605 Lines: 42 On Mon, 2005-09-19 at 09:28 +0200, Ingo Molnar wrote: > * Nick Piggin wrote: > > Oh really? I think yes, the latency should be taken care of because we > > want to be able to provide good latency even for !preempt kernels. If > > a solution can be found for acpi_processor_idle, that would be ideal. > > the ACPI idle code runs with irqs disabled anyway, so there's no issue > here. If something takes long there, we can do little about it. (but in > practice ACPI sleep latencies are pretty ok - the only latencies i found > in the past were due to need_resched bugs in the ACPI idle routine) > Ah, in that case I agree: we have nothing to worry about by merging such a patch then. > > IMO it always felt kind of hackish to run the idle threads with > > preempt on. > > Yes, idle threads can have preemption disabled. There's not any big > difference in terms of latencies, the execution paths are all very > short. > Thanks for the confirmation Ingo. This is part of my "cleanup resched and cpu_idle" patch FYI. It should already be in -mm, but has some trivial EM64T bug in it that Andrew hits but I can't reproduce. I'll dust it off and send it out, hopefully someone will be able to reproduce the problem! -- SUSE Labs, Novell Inc. Send instant messages to your online friends http://au.messenger.yahoo.com - 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/