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=-5.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=unavailable 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 032FCC3A5A2 for ; Fri, 23 Aug 2019 16:20:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D9A6B21726 for ; Fri, 23 Aug 2019 16:20:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2436695AbfHWQU0 (ORCPT ); Fri, 23 Aug 2019 12:20:26 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:36216 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389701AbfHWQU0 (ORCPT ); Fri, 23 Aug 2019 12:20:26 -0400 Received: from bigeasy by Galois.linutronix.de with local (Exim 4.80) (envelope-from ) id 1i1CIa-0005sk-7l; Fri, 23 Aug 2019 18:20:24 +0200 Date: Fri, 23 Aug 2019 18:20:24 +0200 From: Sebastian Andrzej Siewior To: Scott Wood Cc: linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org, "Paul E . McKenney" , Joel Fernandes , Thomas Gleixner , Peter Zijlstra , Juri Lelli , Clark Williams Subject: Re: [PATCH RT v2 2/3] sched: migrate_enable: Use sleeping_lock to indicate involuntary sleep Message-ID: <20190823162024.47t7br6ecfclzgkw@linutronix.de> References: <20190821231906.4224-1-swood@redhat.com> <20190821231906.4224-3-swood@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20190821231906.4224-3-swood@redhat.com> User-Agent: NeoMutt/20180716 Sender: linux-rt-users-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-rt-users@vger.kernel.org On 2019-08-21 18:19:05 [-0500], Scott Wood wrote: > Without this, rcu_note_context_switch() will complain if an RCU read > lock is held when migrate_enable() calls stop_one_cpu(). > > Signed-off-by: Scott Wood > --- > v2: Added comment. > > If my migrate disable changes aren't taken, then pin_current_cpu() > will also need to use sleeping_lock_inc() because calling > __read_rt_lock() bypasses the usual place it's done. > > include/linux/sched.h | 4 ++-- > kernel/rcu/tree_plugin.h | 2 +- > kernel/sched/core.c | 8 ++++++++ > 3 files changed, 11 insertions(+), 3 deletions(-) > > --- a/kernel/sched/core.c > +++ b/kernel/sched/core.c > @@ -7405,7 +7405,15 @@ void migrate_enable(void) > unpin_current_cpu(); > preempt_lazy_enable(); > preempt_enable(); > + > + /* > + * sleeping_lock_inc suppresses a debug check for > + * sleeping inside an RCU read side critical section > + */ > + sleeping_lock_inc(); > stop_one_cpu(task_cpu(p), migration_cpu_stop, &arg); > + sleeping_lock_dec(); this looks like an ugly hack. This sleeping_lock_inc() is used where we actually hold a sleeping lock and schedule() which is okay. But this would mean we hold a RCU lock and schedule() anyway. Is that okay? > + > return; > } > } Sebastian