From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marc Gonzalez Subject: Re: [PATCH v3 1/2] ARM: tango: add HOTPLUG_CPU support Date: Wed, 29 Jun 2016 14:28:23 +0200 Message-ID: <5773BEE7.4080501@sigmadesigns.com> References: <57726597.8030501@sigmadesigns.com> <577266AD.8000006@sigmadesigns.com> <57726DE0.8090308@arm.com> <577291F1.8060105@sigmadesigns.com> <577294E2.5030405@arm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Return-path: Received: from a.mx.sdesigns.eu ([78.31.43.6]:62247 "EHLO a.mx.sdesigns.eu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752048AbcF2M2Z (ORCPT ); Wed, 29 Jun 2016 08:28:25 -0400 In-Reply-To: <577294E2.5030405@arm.com> Sender: linux-pm-owner@vger.kernel.org List-Id: linux-pm@vger.kernel.org To: Robin Murphy Cc: Mark Rutland , Sebastian Frias , linux-pm , Thibaud Cornic , Mason , arm-soc , Linux ARM On 28/06/2016 17:16, Robin Murphy wrote: > On 28/06/16 16:04, Marc Gonzalez wrote: > >> On 28/06/2016 14:30, Robin Murphy wrote: >> >>> Does the firmware guarantee that this will succeed (or at least report >>> success) in finite time, regardless of how messed up the system might >>> be? I'd imagine this should probably have either a timeout or a comment >>> clarifying why it doesn't need a timeout. >> >> Good point. >> >> The FW allows only one thread at a time. If a thread is wedged inside >> the FW, no other thread can use the FW. In that situation, cpu0 would >> remain stuck inside tango_cpu_kill(). >> >> Note, that if tango_cpu_kill() starts failing, then secondary cores >> will remain "zombies". So the system is mostly hosed anyway... >> Only cpu0 will be available. > > Indeed; my thought was that if CPU1 somehow ends up wedged such that > tango_aux_core_die() never completes, then CPU0 eventually timing out > and being able to limp through a clean(ish) reboot is probably > preferable to spinning in cpu_kill() forever. I have sent an updated patch addressing your comment. Thanks for flagging the issue. Regards.