From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755129AbcANWCQ (ORCPT ); Thu, 14 Jan 2016 17:02:16 -0500 Received: from out5-smtp.messagingengine.com ([66.111.4.29]:39999 "EHLO out5-smtp.messagingengine.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754375AbcANWCO (ORCPT ); Thu, 14 Jan 2016 17:02:14 -0500 X-Sasl-enc: fbpeK8QB3G2TODc4muemv8V+HrlcxN4TN2CV8E7O25Qa 1452808933 Subject: Re: [PATCH RT] net: move xmit_recursion to per-task variable on -RT To: Sebastian Andrzej Siewior , Thomas Gleixner References: <20160113152352.GH29964@linutronix.de> <20160114145007.GC17776@linutronix.de> Cc: linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org, Steven Rostedt , netdev@vger.kernel.org From: Hannes Frederic Sowa Message-ID: <56981AE1.20202@stressinduktion.org> Date: Thu, 14 Jan 2016 23:02:09 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.5.0 MIME-Version: 1.0 In-Reply-To: <20160114145007.GC17776@linutronix.de> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 14.01.2016 15:50, Sebastian Andrzej Siewior wrote: > * Thomas Gleixner | 2016-01-13 18:31:46 [+0100]: > >> On Wed, 13 Jan 2016, Sebastian Andrzej Siewior wrote: >>> +#ifdef CONFIG_PREEMPT_RT_FULL >>> +static inline int dev_recursion_level(void) >>> +{ >>> + return atomic_read(¤t->xmit_recursion); >> >> Why would you need an atomic here. current does hardly race against itself. > > right. We are just adding a second recursion limit solely to openvswitch which has the same problem: https://patchwork.ozlabs.org/patch/566769/ This time also we depend on rcu_read_lock marking the section being nonpreemptible. Nice would be a more generic solution here which doesn't need to always add something to *current. Thanks, Hannes