From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A909BC4CECD for ; Tue, 17 Sep 2019 14:08:49 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 79D2621852 for ; Tue, 17 Sep 2019 14:08:49 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727030AbfIQOIt (ORCPT ); Tue, 17 Sep 2019 10:08:49 -0400 Received: from mx1.redhat.com ([209.132.183.28]:59758 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727024AbfIQOIt (ORCPT ); Tue, 17 Sep 2019 10:08:49 -0400 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id DCD684E8AC; Tue, 17 Sep 2019 14:08:48 +0000 (UTC) Received: from ovpn-117-172.phx2.redhat.com (ovpn-117-172.phx2.redhat.com [10.3.117.172]) by smtp.corp.redhat.com (Postfix) with ESMTP id 8EDC460606; Tue, 17 Sep 2019 14:08:45 +0000 (UTC) Message-ID: Subject: Re: [PATCH RT v3 4/5] rcu: Disable use_softirq on PREEMPT_RT From: Scott Wood To: Sebastian Andrzej Siewior Cc: linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org, "Paul E . McKenney" , Joel Fernandes , Thomas Gleixner , Steven Rostedt , Peter Zijlstra , Juri Lelli , Clark Williams Date: Tue, 17 Sep 2019 09:08:45 -0500 In-Reply-To: <20190911165729.11178-5-swood@redhat.com> References: <20190911165729.11178-1-swood@redhat.com> <20190911165729.11178-5-swood@redhat.com> Organization: Red Hat Content-Type: text/plain; charset="UTF-8" User-Agent: Evolution 3.30.5 (3.30.5-1.fc29) MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Tue, 17 Sep 2019 14:08:49 +0000 (UTC) Sender: linux-rt-users-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-rt-users@vger.kernel.org On Wed, 2019-09-11 at 17:57 +0100, Scott Wood wrote: > kernel/rcu/tree.c | 9 +++++++-- > 1 file changed, 7 insertions(+), 2 deletions(-) > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > index fc8b00c61b32..ee0a5ec2c30f 100644 > --- a/kernel/rcu/tree.c > +++ b/kernel/rcu/tree.c > @@ -98,9 +98,14 @@ struct rcu_state rcu_state = { > /* Dump rcu_node combining tree at boot to verify correct setup. */ > static bool dump_tree; > module_param(dump_tree, bool, 0444); > -/* By default, use RCU_SOFTIRQ instead of rcuc kthreads. */ > -static bool use_softirq = 1; > +/* > + * By default, use RCU_SOFTIRQ instead of rcuc kthreads. > + * But, avoid RCU_SOFTIRQ on PREEMPT_RT due to pi/rq deadlocks. > + */ > +static bool use_softirq = !IS_ENABLED(CONFIG_PREEMPT_RT_FULL); > +#ifdef CONFIG_PREEMPT_RT_FULL > module_param(use_softirq, bool, 0444); > +#endif Ugh, that should be s/ifdef/ifndef/ -Scott