From mboxrd@z Thu Jan 1 00:00:00 1970 From: Russell King - ARM Linux Subject: Re: Is Pandaboard cpuhotplug working stably? Date: Wed, 21 Dec 2011 10:07:06 +0000 Message-ID: <20111221100706.GC3354@n2100.arm.linux.org.uk> References: <20111221094624.GB3354@n2100.arm.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Received: from caramon.arm.linux.org.uk ([78.32.30.218]:44668 "EHLO caramon.arm.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751652Ab1LUKHQ (ORCPT ); Wed, 21 Dec 2011 05:07:16 -0500 Content-Disposition: inline In-Reply-To: Sender: linux-omap-owner@vger.kernel.org List-Id: linux-omap@vger.kernel.org To: Barry Song <21cnbao@gmail.com> Cc: linux-omap@vger.kernel.org, yongsheng.liu@csr.com, linaro-dev , peiyu.li@csr.com, DL-SHA-WorkGroupLinux , linux-arm-kernel@lists.infradead.org On Wed, Dec 21, 2011 at 05:59:07PM +0800, Barry Song wrote: > 2011/12/21 Russell King - ARM Linux : > > cpu hotplug is basically totally buggered - the preconditions place= d > > upon the bringup code path are basically impossible to satisfy in a= ny > > shape or form at the moment. > > > > There's the requirement that the secondary CPU is marked online and > > active before interrupts are enabled for the thread migration stuff > > to behave correctly. =A0However, this is incompatible with smp_call= _function() > > which will wait for online CPUs to respond to an IPI - which this o= ne > > won't because interrupts are disabled. > > > > I think there was some discussion about how to fix this but I don't > > recall the details. >=20 > thanks, Russell. then could i think this is an ARM-kernel-specific bu= g > which exists on all ARM SMP chips for the moment? > and that bug doesn't happen on x86: I don't think so. There's nothing ARM specific about it. -- To unsubscribe from this list: send the line "unsubscribe linux-omap" i= n the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html From mboxrd@z Thu Jan 1 00:00:00 1970 From: linux@arm.linux.org.uk (Russell King - ARM Linux) Date: Wed, 21 Dec 2011 10:07:06 +0000 Subject: Is Pandaboard cpuhotplug working stably? In-Reply-To: References: <20111221094624.GB3354@n2100.arm.linux.org.uk> Message-ID: <20111221100706.GC3354@n2100.arm.linux.org.uk> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Wed, Dec 21, 2011 at 05:59:07PM +0800, Barry Song wrote: > 2011/12/21 Russell King - ARM Linux : > > cpu hotplug is basically totally buggered - the preconditions placed > > upon the bringup code path are basically impossible to satisfy in any > > shape or form at the moment. > > > > There's the requirement that the secondary CPU is marked online and > > active before interrupts are enabled for the thread migration stuff > > to behave correctly. ?However, this is incompatible with smp_call_function() > > which will wait for online CPUs to respond to an IPI - which this one > > won't because interrupts are disabled. > > > > I think there was some discussion about how to fix this but I don't > > recall the details. > > thanks, Russell. then could i think this is an ARM-kernel-specific bug > which exists on all ARM SMP chips for the moment? > and that bug doesn't happen on x86: I don't think so. There's nothing ARM specific about it.