From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261794AbVHDRah (ORCPT ); Thu, 4 Aug 2005 13:30:37 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261821AbVHDR37 (ORCPT ); Thu, 4 Aug 2005 13:29:59 -0400 Received: from fmr23.intel.com ([143.183.121.15]:5350 "EHLO scsfmr003.sc.intel.com") by vger.kernel.org with ESMTP id S262405AbVHDR3U (ORCPT ); Thu, 4 Aug 2005 13:29:20 -0400 Date: Thu, 4 Aug 2005 10:27:12 -0700 From: Ashok Raj To: Andi Kleen Cc: Ashok Raj , Andrew Morton , zwane@arm.linux.org.uk, linux-kernel@vger.kernel.org Subject: Re: [patch 5/8] x86_64:Dont do broadcast IPIs when hotplug is enabled in flat mode. Message-ID: <20050804102712.A16102@unix-os.sc.intel.com> References: <20050801202017.043754000@araj-em64t> <20050801203011.403184000@araj-em64t> <20050804105107.GD97893@muc.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5.1i In-Reply-To: <20050804105107.GD97893@muc.de>; from ak@muc.de on Thu, Aug 04, 2005 at 12:51:07PM +0200 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Aug 04, 2005 at 12:51:07PM +0200, Andi Kleen wrote: > > static void flat_send_IPI_allbutself(int vector) > > { > > +#ifndef CONFIG_HOTPLUG_CPU > > if (((num_online_cpus()) - 1) >= 1) > > __send_IPI_shortcut(APIC_DEST_ALLBUT, vector,APIC_DEST_LOGICAL); > > +#else > > + cpumask_t allbutme = cpu_online_map; > > + int me = get_cpu(); /* Ensure we are not preempted when we clear */ > > + cpu_clear(me, allbutme); > > + flat_send_IPI_mask(allbutme, vector); > > + put_cpu(); > > This still needs the num_online_cpus()s check. > > -Andi Modified patch attached. Andrew: the filename in your -mm queue is below, with the attached patch. x86_64dont-do-broadcast-ipis-when-hotplug-is-enabled-in-flat-mode.patch -- Cheers, Ashok Raj - Open Source Technology Center Note: Recent introduction of physflat mode for x86_64 inadvertently deleted the use of non-shortcut version of routines breaking CPU hotplug. The option to select this via cmdline also is deleted with the physflat patch, hence directly placing this code under CONFIG_HOTPLUG_CPU. We dont want to use broadcast mode IPI's when hotplug is enabled. This causes bad effects in send IPI to a cpu that is offline which can trip when the cpu is in the process of being kicked alive. Signed-off-by: Ashok Raj ------------------------------------------------------- arch/x86_64/kernel/genapic_flat.c | 10 ++++++++++ 1 files changed, 10 insertions(+) Index: linux-2.6.13-rc4-mm1/arch/x86_64/kernel/genapic_flat.c =================================================================== --- linux-2.6.13-rc4-mm1.orig/arch/x86_64/kernel/genapic_flat.c +++ linux-2.6.13-rc4-mm1/arch/x86_64/kernel/genapic_flat.c @@ -78,8 +78,18 @@ static void flat_send_IPI_mask(cpumask_t static void flat_send_IPI_allbutself(int vector) { +#ifndef CONFIG_HOTPLUG_CPU if (((num_online_cpus()) - 1) >= 1) __send_IPI_shortcut(APIC_DEST_ALLBUT, vector,APIC_DEST_LOGICAL); +#else + cpumask_t allbutme = cpu_online_map; + int me = get_cpu(); /* Ensure we are not preempted when we clear */ + cpu_clear(me, allbutme); + + if (!cpus_empty(allbutme)) + flat_send_IPI_mask(allbutme, vector); + put_cpu(); +#endif } static void flat_send_IPI_all(int vector)