Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753956Ab3EMN7v (ORCPT ); Mon, 13 May 2013 09:59:51 -0400 Received: from relay2.sgi.com ([192.48.179.30]:41553 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753906Ab3EMN7t (ORCPT ); Mon, 13 May 2013 09:59:49 -0400 Date: Mon, 13 May 2013 08:59:48 -0500 From: Robin Holt To: Thomas Gleixner Cc: Robin Holt , Frederic Weisbecker , linux-kernel@vger.kernel.org, Ingo Molnar Subject: Re: Full dynticks needs evtdesc set before marking cpu online. Message-ID: <20130513135948.GF3658@sgi.com> References: <20130508235736.GT3658@sgi.com> <20130513125514.GE3658@sgi.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1577 Lines: 38 On Mon, May 13, 2013 at 03:03:55PM +0200, Thomas Gleixner wrote: > On Mon, 13 May 2013, Robin Holt wrote: > > > On Mon, May 13, 2013 at 11:21:00AM +0200, Thomas Gleixner wrote: > > > On Wed, 8 May 2013, Robin Holt wrote: > > > > > > > Thomas, > > > > > > > > We are seeing failures booting medium sized machines which I think is > > > > a change in expectations that dyntick put on x86's start_secondary. > > > > > > > > During boot of cpus, we see an occassional panic in tick_do_broadcast at > > > > > > http://lkml.indiana.edu/hypermail/linux/kernel/1305.0/01818.html > > > > > > Will hit Linus tree soon. > > > > I think this is really due to a sequence in start_secondary. The cpu > > has been marked as online, but its evtdesc has not been initialized. > > I sent a followup to this with a hack/patch. > > No, the real issue is that I messed up the cpumask conversion in the > broadcast code, i.e. using alloc instead of zalloc, which allocated > nonzeroed memory for the cpumasks, so any random bit set will crash > the machine. Your patch is just papering over the issue. I believe I understand now. What would be the downside of moving the initialization to before marking the cpu online? It seems like a reasonable this to expect as well in spite of it not being the right fix to the other bug. Thanks, Robin -- 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/