From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932868AbcHVQox (ORCPT ); Mon, 22 Aug 2016 12:44:53 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:58413 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S932486AbcHVQot (ORCPT ); Mon, 22 Aug 2016 12:44:49 -0400 X-IBM-Helo: d03dlp01.boulder.ibm.com X-IBM-MailFrom: paulmck@linux.vnet.ibm.com Date: Mon, 22 Aug 2016 09:44:29 -0700 From: "Paul E. McKenney" To: Nikolay Borisov Cc: linux-kernel@vger.kernel.org, mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com, akpm@linux-foundation.org, mathieu.desnoyers@efficios.com, josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org, rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com, dvhart@linux.intel.com, fweisbec@gmail.com, oleg@redhat.com, bobby.prani@gmail.com, Ding Tianhong Subject: Re: [PATCH tip/core/rcu 1/5] rcu: Fix soft lockup for rcu_nocb_kthread Reply-To: paulmck@linux.vnet.ibm.com References: <20160822152956.GA8160@linux.vnet.ibm.com> <1471879821-8974-1-git-send-email-paulmck@linux.vnet.ibm.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-Content-Scanned: Fidelis XPS MAILER x-cbid: 16082216-0016-0000-0000-0000047A98C0 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00005629; HX=3.00000240; KW=3.00000007; PH=3.00000004; SC=3.00000183; SDB=6.00748143; UDB=6.00353050; IPR=6.00520808; BA=6.00004672; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00012420; XFM=3.00000011; UTC=2016-08-22 16:44:24 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 16082216-0017-0000-0000-0000323B3BB6 Message-Id: <20160822164429.GE3482@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2016-08-22_09:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1604210000 definitions=main-1608220172 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Aug 22, 2016 at 07:19:53PM +0300, Nikolay Borisov wrote: > > [SNIP] > > > > Signed-off-by: Ding Tianhong > > [ paulmck: Substituted cond_resched_rcu_qs for cond_resched. ] > > This contradicts... > > > Signed-off-by: Paul E. McKenney > > --- > > kernel/rcu/tree_plugin.h | 1 + > > 1 file changed, 1 insertion(+) > > > > diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h > > index 0082fce402a0..85c5a883c6e3 100644 > > --- a/kernel/rcu/tree_plugin.h > > +++ b/kernel/rcu/tree_plugin.h > > @@ -2173,6 +2173,7 @@ static int rcu_nocb_kthread(void *arg) > > cl++; > > c++; > > local_bh_enable(); > > + cond_resched_rcu_qs(); > > with what's here? Ding Tianhong's original patch: http://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1167918.html had cond_resched() here, which works for his workload, but can result in stall warnings in other cases. I therfore changed his cond_resched() to the cond_resched_rcu_qs() that you see above, and documented this change in the "paulmck" note after Ding Tianhong's Signed-off-by. So all is as it should be. Thanx, Paul > > list = next; > > } > > trace_rcu_batch_end(rdp->rsp->name, c, !!list, 0, 0, 1); > > >