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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 58E91C7618F for ; Wed, 17 Jul 2019 00:09:32 +0000 (UTC) Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.kernel.org (Postfix) with SMTP id A35D821872 for ; Wed, 17 Jul 2019 00:09:31 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org A35D821872 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.ibm.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kernel-hardening-return-16491-kernel-hardening=archiver.kernel.org@lists.openwall.com Received: (qmail 32764 invoked by uid 550); 17 Jul 2019 00:09:24 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Received: (qmail 32742 invoked from network); 17 Jul 2019 00:09:23 -0000 Date: Tue, 16 Jul 2019 17:07:57 -0700 From: "Paul E. McKenney" To: Joel Fernandes Cc: linux-kernel@vger.kernel.org, Alexey Kuznetsov , Bjorn Helgaas , Borislav Petkov , c0d1n61at3@gmail.com, "David S. Miller" , edumazet@google.com, Greg Kroah-Hartman , Hideaki YOSHIFUJI , "H. Peter Anvin" , Ingo Molnar , Jonathan Corbet , Josh Triplett , keescook@chromium.org, kernel-hardening@lists.openwall.com, kernel-team@android.com, Lai Jiangshan , Len Brown , linux-acpi@vger.kernel.org, linux-doc@vger.kernel.org, linux-pci@vger.kernel.org, linux-pm@vger.kernel.org, Mathieu Desnoyers , neilb@suse.com, netdev@vger.kernel.org, Oleg Nesterov , Pavel Machek , peterz@infradead.org, "Rafael J. Wysocki" , Rasmus Villemoes , rcu@vger.kernel.org, Steven Rostedt , Tejun Heo , Thomas Gleixner , will@kernel.org, "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" Subject: Re: [PATCH 2/9] rcu: Add support for consolidated-RCU reader checking (v3) Message-ID: <20190717000757.GQ14271@linux.ibm.com> References: <20190715143705.117908-1-joel@joelfernandes.org> <20190715143705.117908-3-joel@joelfernandes.org> <20190716183833.GD14271@linux.ibm.com> <20190716184649.GA130463@google.com> <20190716185303.GM14271@linux.ibm.com> <20190716220205.GB172157@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190716220205.GB172157@google.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-07-16_06:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1907160263 On Tue, Jul 16, 2019 at 06:02:05PM -0400, Joel Fernandes wrote: > On Tue, Jul 16, 2019 at 11:53:03AM -0700, Paul E. McKenney wrote: > [snip] > > > > A few more things below. > > > > > --- > > > > > include/linux/rculist.h | 28 ++++++++++++++++++++----- > > > > > include/linux/rcupdate.h | 7 +++++++ > > > > > kernel/rcu/Kconfig.debug | 11 ++++++++++ > > > > > kernel/rcu/update.c | 44 ++++++++++++++++++++++++---------------- > > > > > 4 files changed, 67 insertions(+), 23 deletions(-) > > > > > > > > > > diff --git a/include/linux/rculist.h b/include/linux/rculist.h > > > > > index e91ec9ddcd30..1048160625bb 100644 > > > > > --- a/include/linux/rculist.h > > > > > +++ b/include/linux/rculist.h > > > > > @@ -40,6 +40,20 @@ static inline void INIT_LIST_HEAD_RCU(struct list_head *list) > > > > > */ > > > > > #define list_next_rcu(list) (*((struct list_head __rcu **)(&(list)->next))) > > > > > > > > > > +/* > > > > > + * Check during list traversal that we are within an RCU reader > > > > > + */ > > > > > + > > > > > +#ifdef CONFIG_PROVE_RCU_LIST > > > > > > > > This new Kconfig option is OK temporarily, but unless there is reason to > > > > fear malfunction that a few weeks of rcutorture, 0day, and -next won't > > > > find, it would be better to just use CONFIG_PROVE_RCU. The overall goal > > > > is to reduce the number of RCU knobs rather than grow them, must though > > > > history might lead one to believe otherwise. :-/ > > > > > > If you want, we can try to drop this option and just use PROVE_RCU however I > > > must say there may be several warnings that need to be fixed in a short > > > period of time (even a few weeks may be too short) considering the 1000+ > > > uses of RCU lists. > > Do many people other than me build with CONFIG_PROVE_RCU? If so, then > > that would be a good reason for a temporary CONFIG_PROVE_RCU_LIST, > > as in going away in a release or two once the warnings get fixed. > > PROVE_RCU is enabled by default with PROVE_LOCKING, so it is used quite > heavilty. > > > > But I don't mind dropping it and it may just accelerate the fixing up of all > > > callers. > > > > I will let you decide based on the above question. But if you have > > CONFIG_PROVE_RCU_LIST, as noted below, it needs to depend on RCU_EXPERT. > > Ok, will make it depend. But yes for temporary purpose, I will leave it as a > config and remove it later. Very good, thank you! Plus you got another ack. ;-) Thanx, Paul