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=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, 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 875A0C31E40 for ; Tue, 13 Aug 2019 02:51:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 604702067D for ; Tue, 13 Aug 2019 02:51:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726488AbfHMCvB (ORCPT ); Mon, 12 Aug 2019 22:51:01 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:50098 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726453AbfHMCvB (ORCPT ); Mon, 12 Aug 2019 22:51:01 -0400 Received: from pps.filterd (m0098404.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x7D2llCK142409; Mon, 12 Aug 2019 22:50:59 -0400 Received: from ppma02wdc.us.ibm.com (aa.5b.37a9.ip4.static.sl-reverse.com [169.55.91.170]) by mx0a-001b2d01.pphosted.com with ESMTP id 2ubg6hg6kt-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Mon, 12 Aug 2019 22:50:59 -0400 Received: from pps.filterd (ppma02wdc.us.ibm.com [127.0.0.1]) by ppma02wdc.us.ibm.com (8.16.0.27/8.16.0.27) with SMTP id x7D2oBr9003683; Tue, 13 Aug 2019 02:50:58 GMT Received: from b01cxnp23034.gho.pok.ibm.com (b01cxnp23034.gho.pok.ibm.com [9.57.198.29]) by ppma02wdc.us.ibm.com with ESMTP id 2u9nj62bf0-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 13 Aug 2019 02:50:58 +0000 Received: from b01ledav003.gho.pok.ibm.com (b01ledav003.gho.pok.ibm.com [9.57.199.108]) by b01cxnp23034.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x7D2ovOd51380506 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 13 Aug 2019 02:50:57 GMT Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id A9145B2064; Tue, 13 Aug 2019 02:50:57 +0000 (GMT) Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 89864B205F; Tue, 13 Aug 2019 02:50:57 +0000 (GMT) Received: from paulmck-ThinkPad-W541 (unknown [9.80.215.124]) by b01ledav003.gho.pok.ibm.com (Postfix) with ESMTP; Tue, 13 Aug 2019 02:50:57 +0000 (GMT) Received: by paulmck-ThinkPad-W541 (Postfix, from userid 1000) id 3BC6116C0AC3; Mon, 12 Aug 2019 19:50:57 -0700 (PDT) Date: Mon, 12 Aug 2019 19:50:57 -0700 From: "Paul E. McKenney" To: Joel Fernandes Cc: rcu@vger.kernel.org Subject: Re: need_heavy_qs flag for PREEMPT=y kernels Message-ID: <20190813025057.GY28441@linux.ibm.com> Reply-To: paulmck@linux.ibm.com References: <20190811180852.GA128944@google.com> <20190811211318.GX28441@linux.ibm.com> <20190812032142.GA171001@google.com> <20190812035306.GE28441@linux.ibm.com> <20190812212013.GB48751@google.com> <20190812230138.GS28441@linux.ibm.com> <20190813010249.GA129011@google.com> <20190813022726.GW28441@linux.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190813022726.GW28441@linux.ibm.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=2019-08-12_09:,, 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=727 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1906280000 definitions=main-1908130029 Sender: rcu-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org On Mon, Aug 12, 2019 at 07:27:26PM -0700, Paul E. McKenney wrote: > On Mon, Aug 12, 2019 at 09:02:49PM -0400, Joel Fernandes wrote: > > On Mon, Aug 12, 2019 at 04:01:38PM -0700, Paul E. McKenney wrote: [ . . . ] > > Instead of checking dynticks_nmi_nesting == 2 in rcu_nmi_exit_common(), can > > we do the tick_dep_set_cpu(rdp->cpu, TICK_DEP_MASK_RCU) from > > rcu_nmi_enter_common() ? We could add this code there, under the "if > > (rcu_dynticks_curr_cpu_in_eqs())". > > It might well make sense to do this on entry, especially if doing so > might safe an instruction or two. It won't make the tick happen much > faster, given that interrupts are disabled throughout the handler. > > > I will test this patch tomorrow and let you know how it goes. > > No need, it dies horribly and quickly with rcutorture. Not exactly > a surprise. ;-) And also not a surprise, due to a laughably stupid mistake... Thanx, Paul