From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wi0-f175.google.com (mail-wi0-f175.google.com [209.85.212.175]) by kanga.kvack.org (Postfix) with ESMTP id 271E86B0032 for ; Mon, 13 Apr 2015 12:49:54 -0400 (EDT) Received: by wiax7 with SMTP id x7so69324968wia.0 for ; Mon, 13 Apr 2015 09:49:53 -0700 (PDT) Received: from mail-wi0-x235.google.com (mail-wi0-x235.google.com. [2a00:1450:400c:c05::235]) by mx.google.com with ESMTPS id uc1si18505030wjc.27.2015.04.13.09.49.52 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 13 Apr 2015 09:49:52 -0700 (PDT) Received: by wiun10 with SMTP id n10so74186736wiu.1 for ; Mon, 13 Apr 2015 09:49:52 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: <552BC6E8.1040400@yandex-team.ru> References: <20150408165920.25007.6869.stgit@buzz> <552BC6E8.1040400@yandex-team.ru> From: Rob Herring Date: Mon, 13 Apr 2015 11:49:31 -0500 Message-ID: Subject: Re: [PATCH] of: return NUMA_NO_NODE from fallback of_node_to_nid() Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: Konstantin Khlebnikov Cc: Grant Likely , "devicetree@vger.kernel.org" , Rob Herring , "linux-kernel@vger.kernel.org" , sparclinux@vger.kernel.org, "linux-mm@kvack.org" , linuxppc-dev On Mon, Apr 13, 2015 at 8:38 AM, Konstantin Khlebnikov wrote: > On 13.04.2015 16:22, Rob Herring wrote: >> >> On Wed, Apr 8, 2015 at 11:59 AM, Konstantin Khlebnikov >> wrote: >>> >>> Node 0 might be offline as well as any other numa node, >>> in this case kernel cannot handle memory allocation and crashes. >>> >>> Signed-off-by: Konstantin Khlebnikov >>> Fixes: 0c3f061c195c ("of: implement of_node_to_nid as a weak function") >>> --- >>> drivers/of/base.c | 2 +- >>> include/linux/of.h | 5 ++++- >>> 2 files changed, 5 insertions(+), 2 deletions(-) >>> >>> diff --git a/drivers/of/base.c b/drivers/of/base.c >>> index 8f165b112e03..51f4bd16e613 100644 >>> --- a/drivers/of/base.c >>> +++ b/drivers/of/base.c >>> @@ -89,7 +89,7 @@ EXPORT_SYMBOL(of_n_size_cells); >>> #ifdef CONFIG_NUMA >>> int __weak of_node_to_nid(struct device_node *np) >>> { >>> - return numa_node_id(); >>> + return NUMA_NO_NODE; >> >> >> This is going to break any NUMA machine that enables OF and expects >> the weak function to work. > > > Why? NUMA_NO_NODE == -1 -- this's standard "no-affinity" signal. > As I see powerpc/sparc versions of of_node_to_nid returns -1 if they > cannot find out which node should be used. Ah, I was thinking those platforms were relying on the default implementation. I guess any real NUMA support is going to need to override this function. The arm64 patch series does that as well. We need to be sure this change is correct for metag which appears to be the only other OF enabled platform with NUMA support. In that case, then there is little reason to keep the inline and we can just always enable the weak function (with your change). It is slightly less optimal, but the few callers hardly appear to be hot paths. Rob -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org