From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754590AbaIZNWi (ORCPT ); Fri, 26 Sep 2014 09:22:38 -0400 Received: from cam-admin0.cambridge.arm.com ([217.140.96.50]:46279 "EHLO cam-admin0.cambridge.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754285AbaIZNWh (ORCPT ); Fri, 26 Sep 2014 09:22:37 -0400 Date: Fri, 26 Sep 2014 14:20:38 +0100 From: Mark Rutland To: Russell King - ARM Linux Cc: Chenhui Zhao , "kernel@pengutronix.de" , "linux-kernel@vger.kernel.org" , "Zhuoyu.Zhang@freescale.com" , "Jason.Jin@freescale.com" , "leoli@freescale.com" , "linux-arm-kernel@lists.infradead.org" Subject: Re: [PATCH 1/3] arm: ls1: add CPU hotplug platform support Message-ID: <20140926132038.GF7422@leverpostej> References: <1411730703-25836-1-git-send-email-chenhui.zhao@freescale.com> <1411730703-25836-2-git-send-email-chenhui.zhao@freescale.com> <20140926122003.GP5182@n2100.arm.linux.org.uk> <20140926124614.GD7422@leverpostej> <20140926130311.GQ5182@n2100.arm.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140926130311.GQ5182@n2100.arm.linux.org.uk> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > > This looks to be a carbon copy of the vexpress pseudo-hotplug in > > arch/arm/mach-vexpress/hotplug.c, which is obviously broken in the way > > you describe above. Perhaps we should go about ripping that out? > > The Versatile Express does not support suspend so the only problem case > is kexec. However, isn't this support needed for big.LITTLE, and as > the Versatile Express is the platform which these features get developed > on, having working CPU hotplug seems rather fundamental for ARM kernel > feature development. > > In that regard, Versatile Express is something of a special case. It is admittedly helpful during development to perform pseudo-hotplug on Versatile Express. I have a local patch adding vexpress_cpu_disable so I can test for bugs that only trigger if CPU0 is hotplugged. Given that, perhaps we should make it clearer that Versatile Express is not a reference implementation for CPU hotplug; add some Kconfig (e.g. VEXPRESS_PSEUDO_HOTPLUG) that depends on !KEXEC && !SUSPEND, and putting a note in hotplug.c stating it's not suitable as a reference implementation. ...but perhaps that's overkill. Mark.