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Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Wed, 20 Mar 2019 15:20:57 -0000 Received: from b01ledav003.gho.pok.ibm.com (b01ledav003.gho.pok.ibm.com [9.57.199.108]) by b01cxnp22036.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x2KFKua620840700 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 20 Mar 2019 15:20:56 GMT Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 4AE96B2065; Wed, 20 Mar 2019 15:20:56 +0000 (GMT) Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 37C4BB206B; Wed, 20 Mar 2019 15:20:56 +0000 (GMT) Received: from paulmck-ThinkPad-W541 (unknown [9.70.82.188]) by b01ledav003.gho.pok.ibm.com (Postfix) with ESMTP; Wed, 20 Mar 2019 15:20:56 +0000 (GMT) Received: by paulmck-ThinkPad-W541 (Postfix, from userid 1000) id 87BAC16C2956; Wed, 20 Mar 2019 08:21:46 -0700 (PDT) Date: Wed, 20 Mar 2019 08:21:46 -0700 From: "Paul E. McKenney" To: Sebastian Andrzej Siewior Cc: linux-kernel@vger.kernel.org, Josh Triplett , Steven Rostedt , Mathieu Desnoyers , Lai Jiangshan , Joel Fernandes , tglx@linutronix.de, Mike Galbraith Subject: Re: [PATCH v2] rcu: Allow to eliminate softirq processing from rcutree Reply-To: paulmck@linux.ibm.com References: <20190315111130.4902-1-bigeasy@linutronix.de> <20190318022434.GE4102@linux.ibm.com> <20190319114419.qlsw3i5bmndoyvao@linutronix.de> <20190320113219.d6c3gouqbnsnl5nj@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20190320113219.d6c3gouqbnsnl5nj@linutronix.de> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 x-cbid: 19032015-2213-0000-0000-00000367934C X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00010789; HX=3.00000242; KW=3.00000007; PH=3.00000004; SC=3.00000281; SDB=6.01177119; UDB=6.00615751; IPR=6.00957815; MB=3.00026072; MTD=3.00000008; XFM=3.00000015; UTC=2019-03-20 15:21:00 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 19032015-2214-0000-0000-00005DBC9825 Message-Id: <20190320152146.GH4102@linux.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-03-20_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=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1903200115 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Mar 20, 2019 at 12:32:19PM +0100, Sebastian Andrzej Siewior wrote: > On 2019-03-19 12:44:19 [+0100], To Paul E. McKenney wrote: > > diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c > > index 0f31b79eb6761..0a719f726e149 100644 > > --- a/kernel/rcu/tree.c > > +++ b/kernel/rcu/tree.c > … > > +/* > > + * Spawn per-CPU RCU core processing kthreads. > > + */ > > +static int __init rcu_spawn_core_kthreads(void) > > +{ > > + int cpu; > > + > > + for_each_possible_cpu(cpu) > > + per_cpu(rcu_data.rcu_cpu_has_work, cpu) = 0; > > + if (!IS_ENABLED(CONFIG_RCU_BOOST) && !rcu_softirq_enabled) > > and this needs to become > - if (!IS_ENABLED(CONFIG_RCU_BOOST) && !rcu_softirq_enabled) > + if (!IS_ENABLED(CONFIG_RCU_BOOST) && rcu_softirq_enabled) > > With this change and hunk that I just sent to Joel I get thee three RCU > modes with and without BOOST booted. > > Unless there is something (and Paul agrees that the Joel hunk is > correct) I would post a v3 with those changes included. Well, I did get a bunch of grace-period hangs of various sorts when I ran rcutorture like this: tools/testing/selftests/rcutorture/bin/kvm.sh --memory 1G --bootargs rcunosoftirq I also got a silent hard hang on TREE03. And an rcutorture forward-progress failure, which goes along with the grace-period hangs. So something does need adjustment. I will try again with this change. Thanx, Paul > > + return 0; > > + WARN_ONCE(smpboot_register_percpu_thread(&rcu_cpu_thread_spec), "%s: Could not start rcub kthread, OOM is now expected behavior\n", __func__); > > + return 0; > > +} > > +early_initcall(rcu_spawn_core_kthreads); > > Sebastian >