Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S936267AbdGTLr4 (ORCPT ); Thu, 20 Jul 2017 07:47:56 -0400 Received: from mail-wm0-f67.google.com ([74.125.82.67]:33582 "EHLO mail-wm0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935041AbdGTLry (ORCPT ); Thu, 20 Jul 2017 07:47:54 -0400 Date: Thu, 20 Jul 2017 13:47:50 +0200 From: Ingo Molnar To: Andrew Banman Cc: mingo@redhat.com, tglx@linutronix.de, x86@kernel.org, linux-kernel@vger.kernel.org, rja@hpe.com, mike.travis@hpe.com Subject: Re: [PATCH] x86/platform/uv/BAU: disable BAU on single hub configurations Message-ID: <20170720114750.mykc2i2cc44m34sp@gmail.com> References: <1500414693-84043-1-git-send-email-abanman@hpe.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1500414693-84043-1-git-send-email-abanman@hpe.com> User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2133 Lines: 79 * Andrew Banman wrote: > The BAU confers no benefit to a UV system running with only one hub/socket. > Permanently disable the BAU driver if there are less than two hubs online > to avoid BAU overhead. We have observed failed boots on single-socket UV4 > systems caused by BAU that are avoided with this patch. > > Signed-off-by: Andrew Banman > Acked-by: Russ Anderson > Acked-by: Mike Travis > --- > arch/x86/platform/uv/tlb_uv.c | 6 ++++++ > 1 file changed, 6 insertions(+) > > diff --git a/arch/x86/platform/uv/tlb_uv.c b/arch/x86/platform/uv/tlb_uv.c > index 2511a28..88216cc 100644 > --- a/arch/x86/platform/uv/tlb_uv.c > +++ b/arch/x86/platform/uv/tlb_uv.c > @@ -2251,6 +2251,12 @@ static int __init uv_bau_init(void) > } > > nuvhubs = uv_num_possible_blades(); > + if (nuvhubs < 2) { > + pr_crit("UV: BAU disabled - insufficient hub count\n"); > + set_bau_off(); > + nobau_perm = 1; > + return 0; > + } Yeah, could you structure the error paths in this function in a bit more organized fashion? It has two similar error handling blocks: pr_crit("UV: BAU disabled - insufficient hub count\n"); set_bau_off(); nobau_perm = 1; return 0; ... set_bau_off(); nobau_perm = 1; return 0; which could be consolidated via the usual goto exception construct: if (nuvhubs < 2) { pr_crit("UV: BAU disabled - insufficient hub count\n"); goto err_disable_bau; } ... if (init_per_cpu(nuvhubs, uv_base_pnode)) pr_crit("UV: BAU disabled - per CPU init failed\n"); goto err_disable_bau; } ... return 0; err_disable_bau: set_bau_off(); nobau_perm = 1; return 0; Note that I added an error message to the second case as well. Plus, in the error case you might want to use a 'return -EINVAL;' instead of return 0, or so? Plus plus, there's probably a (mild) memory leak in the error paths, can the cpumasks be free_cpumask_var() freed - or are they still required even if BAU is disabled? Thanks, Ingo