From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753136AbeDIOoz (ORCPT ); Mon, 9 Apr 2018 10:44:55 -0400 Received: from mail-qk0-f196.google.com ([209.85.220.196]:42721 "EHLO mail-qk0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750759AbeDIOox (ORCPT ); Mon, 9 Apr 2018 10:44:53 -0400 X-Google-Smtp-Source: AIpwx496y8uqBCEsPiuMJ8yCJsIpMW2W+1qWOFcW7tzStjrzbHGUEmBAuBSFPMRtvIdj58TScfvqiw== Subject: Re: [PATCH] net: decnet: Replace GFP_ATOMIC with GFP_KERNEL in dn_route_init To: Jia-Ju Bai , davem@davemloft.net, kafai@fb.com, weiwan@google.com, dsa@cumulusnetworks.com, johannes.berg@intel.com, fw@strlen.de Cc: linux-decnet-user@lists.sourceforge.net, netdev@vger.kernel.org, linux-kernel@vger.kernel.org References: <1523283035-25639-1-git-send-email-baijiaju1990@gmail.com> From: Eric Dumazet Message-ID: <945ed4f2-e1e2-a038-2808-f18a79a35732@gmail.com> Date: Mon, 9 Apr 2018 07:44:49 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 MIME-Version: 1.0 In-Reply-To: <1523283035-25639-1-git-send-email-baijiaju1990@gmail.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 04/09/2018 07:10 AM, Jia-Ju Bai wrote: > dn_route_init() is never called in atomic context. > > The call chain ending up at dn_route_init() is: > [1] dn_route_init() <- decnet_init() > decnet_init() is only set as a parameter of module_init(). > > Despite never getting called from atomic context, > dn_route_init() calls __get_free_pages() with GFP_ATOMIC, > which waits busily for allocation. > GFP_ATOMIC is not necessary and can be replaced with GFP_KERNEL, > to avoid busy waiting and improve the possibility of sucessful allocation. > > This is found by a static analysis tool named DCNS written by myself. > And I also manually check it. > > Signed-off-by: Jia-Ju Bai > --- > net/decnet/dn_route.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/net/decnet/dn_route.c b/net/decnet/dn_route.c > index 0bd3afd..59ed12a 100644 > --- a/net/decnet/dn_route.c > +++ b/net/decnet/dn_route.c > @@ -1898,7 +1898,7 @@ void __init dn_route_init(void) > while(dn_rt_hash_mask & (dn_rt_hash_mask - 1)) > dn_rt_hash_mask--; > dn_rt_hash_table = (struct dn_rt_hash_bucket *) > - __get_free_pages(GFP_ATOMIC, order); > + __get_free_pages(GFP_KERNEL, order); > } while (dn_rt_hash_table == NULL && --order > 0); > > if (!dn_rt_hash_table) > This might OOM under pressure. This would need __GFP_NOWARN | __GFP_NORETRY I guess, and would target net-next