From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752108AbbJPCOx (ORCPT ); Thu, 15 Oct 2015 22:14:53 -0400 Received: from ozlabs.org ([103.22.144.67]:41801 "EHLO ozlabs.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751509AbbJPCOw (ORCPT ); Thu, 15 Oct 2015 22:14:52 -0400 Message-ID: <1444961690.28419.1.camel@ellerman.id.au> Subject: Re: [PATCH] powerpc: on crash, kexec'ed kernel needs all CPUs are online From: Michael Ellerman To: Laurent Vivier Cc: Benjamin Herrenschmidt , Paul Mackerras , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, dgibson@redhat.com, thuth@redhat.com Date: Fri, 16 Oct 2015 13:14:50 +1100 In-Reply-To: <1444935658-27319-1-git-send-email-lvivier@redhat.com> References: <1444935658-27319-1-git-send-email-lvivier@redhat.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.12.11-0ubuntu3 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 2015-10-15 at 21:00 +0200, Laurent Vivier wrote: > On kexec, all secondary offline CPUs are onlined before > starting the new kernel, this is not done in the case of kdump. > > If kdump is configured and a kernel crash occurs whereas > some secondaries CPUs are offline (SMT=off), > the new kernel is not able to start them and displays some > "Processor X is stuck.". Do we know why they are stuck? I really don't like this fix. The reason we're doing a kdump is because the first kernel has panicked, possibly with locks held or data structures corrupted. Calling cpu_up() then goes and tries to run a bunch of code in the crashed kernel, which increases the chance of us just wedging completely. cheers