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=-4.8 required=3.0 tests=DATE_IN_PAST_24_48, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 A49D3C3A5A4 for ; Sat, 24 Aug 2019 18:09:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 849BC2082F for ; Sat, 24 Aug 2019 18:09:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727773AbfHXSJN (ORCPT ); Sat, 24 Aug 2019 14:09:13 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:55214 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726464AbfHXSJM (ORCPT ); Sat, 24 Aug 2019 14:09:12 -0400 Received: from pps.filterd (m0098413.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x7OI6mcf109799; Sat, 24 Aug 2019 14:08:39 -0400 Received: from pps.reinject (localhost [127.0.0.1]) by mx0b-001b2d01.pphosted.com with ESMTP id 2ujycnpjww-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Sat, 24 Aug 2019 14:08:39 -0400 Received: from m0098413.ppops.net (m0098413.ppops.net [127.0.0.1]) by pps.reinject (8.16.0.27/8.16.0.27) with SMTP id x7OI866r111633; Sat, 24 Aug 2019 14:08:38 -0400 Received: from ppma02dal.us.ibm.com (a.bd.3ea9.ip4.static.sl-reverse.com [169.62.189.10]) by mx0b-001b2d01.pphosted.com with ESMTP id 2ujycnpjwc-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Sat, 24 Aug 2019 14:08:38 -0400 Received: from pps.filterd (ppma02dal.us.ibm.com [127.0.0.1]) by ppma02dal.us.ibm.com (8.16.0.27/8.16.0.27) with SMTP id x7OI581E030781; Sat, 24 Aug 2019 18:08:37 GMT Received: from b01cxnp23033.gho.pok.ibm.com (b01cxnp23033.gho.pok.ibm.com [9.57.198.28]) by ppma02dal.us.ibm.com with ESMTP id 2ujvv63wuv-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Sat, 24 Aug 2019 18:08:37 +0000 Received: from b01ledav003.gho.pok.ibm.com (b01ledav003.gho.pok.ibm.com [9.57.199.108]) by b01cxnp23033.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x7OI8b9f26739032 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Sat, 24 Aug 2019 18:08:37 GMT Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id E04AFB2065; Sat, 24 Aug 2019 18:08:36 +0000 (GMT) Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id B27A9B206C; Sat, 24 Aug 2019 18:08:36 +0000 (GMT) Received: from paulmck-ThinkPad-W541 (unknown [9.85.187.121]) by b01ledav003.gho.pok.ibm.com (Postfix) with ESMTP; Sat, 24 Aug 2019 18:08:36 +0000 (GMT) Received: by paulmck-ThinkPad-W541 (Postfix, from userid 1000) id 124E316C3882; Fri, 23 Aug 2019 05:30:38 -0700 (PDT) Date: Fri, 23 Aug 2019 05:30:38 -0700 From: "Paul E. McKenney" To: Scott Wood Cc: Joel Fernandes , Sebastian Andrzej Siewior , linux-rt-users@vger.kernel.org, linux-kernel@vger.kernel.org, Thomas Gleixner , Peter Zijlstra , Juri Lelli , Clark Williams Subject: Re: [PATCH RT v2 1/3] rcu: Acquire RCU lock when disabling BHs Message-ID: <20190823123038.GR28441@linux.ibm.com> Reply-To: paulmck@linux.ibm.com References: <20190821231906.4224-1-swood@redhat.com> <20190821231906.4224-2-swood@redhat.com> <20190821233358.GU28441@linux.ibm.com> <20190822133955.GA29841@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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=2019-08-24_11:,, 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=8.0.1-1906280000 definitions=main-1908240201 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Aug 22, 2019 at 10:23:23PM -0500, Scott Wood wrote: > On Thu, 2019-08-22 at 09:39 -0400, Joel Fernandes wrote: > > On Wed, Aug 21, 2019 at 04:33:58PM -0700, Paul E. McKenney wrote: > > > On Wed, Aug 21, 2019 at 06:19:04PM -0500, Scott Wood wrote: [ . . . ] > > > > include/linux/rcupdate.h | 4 ++++ > > > > kernel/rcu/update.c | 4 ++++ > > > > kernel/softirq.c | 12 +++++++++--- > > > > 3 files changed, 17 insertions(+), 3 deletions(-) > > > > > > > > diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h > > > > index 388ace315f32..d6e357378732 100644 > > > > --- a/include/linux/rcupdate.h > > > > +++ b/include/linux/rcupdate.h > > > > @@ -615,10 +615,12 @@ static inline void rcu_read_unlock(void) > > > > static inline void rcu_read_lock_bh(void) > > > > { > > > > local_bh_disable(); > > > > +#ifndef CONFIG_PREEMPT_RT_FULL > > > > __acquire(RCU_BH); > > > > rcu_lock_acquire(&rcu_bh_lock_map); > > > > RCU_LOCKDEP_WARN(!rcu_is_watching(), > > > > "rcu_read_lock_bh() used illegally while idle"); > > > > +#endif > > > > > > Any chance of this using "if (!IS_ENABLED(CONFIG_PREEMPT_RT_FULL))"? > > > We should be OK providing a do-nothing __maybe_unused rcu_bh_lock_map > > > for lockdep-enabled -rt kernels, right? > > > > Since this function is small, I prefer if -rt defines their own > > rcu_read_lock_bh() which just does the local_bh_disable(). That would be > > way > > cleaner IMO. IIRC, -rt does similar things for spinlocks, but it has been > > sometime since I look at the -rt patchset. > > I'll do it whichever way you all decide, though I'm not sure I agree about > it being cleaner (especially while RT is still out-of-tree and a change to > the non-RT version that fails to trigger a merge conflict is a concern). > > What about moving everything but the local_bh_disable into a separate > function called from rcu_read_lock_bh, and making that a no-op on RT? That makes a lot of sense to me! Thanx, Paul