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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 660C2C48BD6 for ; Wed, 26 Jun 2019 16:49:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 41C1C2080C for ; Wed, 26 Jun 2019 16:49:26 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726690AbfFZQtY (ORCPT ); Wed, 26 Jun 2019 12:49:24 -0400 Received: from mx1.redhat.com ([209.132.183.28]:56536 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726042AbfFZQtY (ORCPT ); Wed, 26 Jun 2019 12:49:24 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 54DFD3082AEF; Wed, 26 Jun 2019 16:49:20 +0000 (UTC) Received: from ovpn-116-138.phx2.redhat.com (ovpn-116-138.phx2.redhat.com [10.3.116.138]) by smtp.corp.redhat.com (Postfix) with ESMTP id 2E7635C224; Wed, 26 Jun 2019 16:49:17 +0000 (UTC) Message-ID: <8462f30720637ec0da377aa737d26d2cad424d36.camel@redhat.com> Subject: Re: [RFC PATCH RT 4/4] rcutorture: Avoid problematic critical section nesting From: Scott Wood To: Steven Rostedt , "Paul E. McKenney" Cc: Sebastian Andrzej Siewior , Peter Zijlstra , Thomas Gleixner , Juri Lelli , Clark Williams , linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org Date: Wed, 26 Jun 2019 11:49:16 -0500 In-Reply-To: <20190626110847.2dfdf72c@gandalf.local.home> References: <20190619011908.25026-1-swood@redhat.com> <20190619011908.25026-5-swood@redhat.com> <20190620211826.GX26519@linux.ibm.com> <20190621163821.rm2rhsnvfo5tnjul@linutronix.de> <20190621235955.GK26519@linux.ibm.com> <20190626110847.2dfdf72c@gandalf.local.home> 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 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.45]); Wed, 26 Jun 2019 16:49:24 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 2019-06-26 at 11:08 -0400, Steven Rostedt wrote: > On Fri, 21 Jun 2019 16:59:55 -0700 > "Paul E. McKenney" wrote: > > > I have no objection to the outlawing of a number of these sequences in > > mainline, but am rather pointing out that until they really are outlawed > > and eliminated, rcutorture must continue to test them in mainline. > > Of course, an rcutorture running in -rt should avoid testing things that > > break -rt, including these sequences. > > We should update lockdep to complain about these sequences. That would > "outlaw" them in mainline. That is, after we clean up all the current > sequences in the code. And we also need to get Linus's approval of this > as I believe he was against enforcing this in the past. Was the opposition to prohibiting some specific sequence? It's only certain misnesting scenarios that are problematic. The rcu_read_lock/ local_irq_disable restriction can be dropped with the IPI-to-self added in Paul's tree. Are there any known instances of the other two (besides rcutorture)? -Scott