Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754697Ab3FML0Q (ORCPT ); Thu, 13 Jun 2013 07:26:16 -0400 Received: from ch1ehsobe001.messaging.microsoft.com ([216.32.181.181]:30210 "EHLO ch1outboundpool.messaging.microsoft.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752088Ab3FML0O (ORCPT ); Thu, 13 Jun 2013 07:26:14 -0400 X-Forefront-Antispam-Report: CIP:70.37.183.190;KIP:(null);UIP:(null);IPV:NLI;H:mail.freescale.net;RD:none;EFVD:NLI X-SpamScore: -3 X-BigFish: VS-3(zz98dI936eI1432Izz1f42h1ee6h1de0h1fdah1202h1e76h1d1ah1d2ah1fc6hzzz2dh2a8h668h839h944hd25hf0ah1220h1288h12a5h12a9h12bdh137ah13b6h1441h1504h1537h153bh162dh1631h16a6h1758h1806h18e1h1946h19b5h1ad9h1b0ah1d0ch1d2eh1d3fh1de2h1dfeh1dffh1155h) Date: Thu, 13 Jun 2013 19:25:52 +0800 From: Zhao Chenhui To: Benjamin Herrenschmidt CC: , Subject: Re: [PATCH] powerpc/sysfs: disable hotplug for the boot cpu Message-ID: <20130613112552.GC7536@localhost.localdomain> References: <1369727984-21505-1-git-send-email-chenhui.zhao@freescale.com> <1369727984-21505-2-git-send-email-chenhui.zhao@freescale.com> <1370036984.3928.144.camel@pasglop> <20130603104315.GA1365@localhost.localdomain> <1371007522.8250.169.camel@pasglop> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <1371007522.8250.169.camel@pasglop> User-Agent: Mutt/1.5.21 (2010-09-15) X-OriginatorOrg: freescale.com Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1861 Lines: 47 On Wed, Jun 12, 2013 at 01:25:22PM +1000, Benjamin Herrenschmidt wrote: > On Mon, 2013-06-03 at 18:43 +0800, Zhao Chenhui wrote: > > On Sat, Jun 01, 2013 at 07:49:44AM +1000, Benjamin Herrenschmidt wrote: > > > On Tue, 2013-05-28 at 15:59 +0800, Zhao Chenhui wrote: > > > > Some features depend on the boot cpu, for instance, hibernate/suspend. > > > > So disable hotplug for the boot cpu. > > > > > > Don't we have code to "move" the boot CPU around when that happens ? > > > > > > Ben. > > > > > > > Currently, the code in generic_cpu_disable() likes this: > > > > if (cpu == boot_cpuid) > > return -EBUSY; > > But the code in pseries/hotplug-cpu.c doesn't, we just "move" the boot > CPU around when that happens. Any reason we can't do that generically ? > > Cheers, > Ben. > Some multicore SoCs firstly boot up the cpu0 after warm reset. In some suspend/resume cases, SoC will do a warm reset when resuming. In order to ensure that the suspending and resuming is running on a same cpu, cpu0 should be the last cpu to suspend. Here, cpu0 is the boot_cpuid. -Chenhui > > If the dying cpu is the boot cpu, it will return -EBUSY. In the subsequent error handling, > > cpu_notify_nofail(CPU_DOWN_FAILED) in _cpu_down() will be called. Unfortunately, some > > cpu notifier callbacks handled CPU_DOWN_PREPARE, but not CPU_DOWN_FAILED, such as sched_cpu_inactive(). > > So it will cause issues. > > > > If we set the hotpluggable for the boot cpu, we can prevent user applications from disabling the boot cpu. > > > > -Chenhui > > -- 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/