From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752432AbeEKQX0 (ORCPT ); Fri, 11 May 2018 12:23:26 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:55134 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752405AbeEKQXW (ORCPT ); Fri, 11 May 2018 12:23:22 -0400 Date: Fri, 11 May 2018 09:24:43 -0700 From: "Paul E. McKenney" To: Joel Fernandes 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, fweisbec@gmail.com, oleg@redhat.com, joel.opensrc@gmail.com, torvalds@linux-foundation.org, npiggin@gmail.com Subject: Re: [tip/core/rcu, 05/21] rcu: Make rcu_gp_cleanup() more accurately predict need for new GP Reply-To: paulmck@linux.vnet.ibm.com References: <1524452624-27589-5-git-send-email-paulmck@linux.vnet.ibm.com> <20180510072133.GA122810@joelaf.mtv.corp.google.com> <20180510131546.GN26088@linux.vnet.ibm.com> <20180510173754.GB228531@joelaf.mtv.corp.google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180510173754.GB228531@joelaf.mtv.corp.google.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 x-cbid: 18051116-0048-0000-0000-0000026BAF15 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00009006; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000260; SDB=6.01030800; UDB=6.00526835; IPR=6.00809931; MB=3.00021049; MTD=3.00000008; XFM=3.00000015; UTC=2018-05-11 16:23:19 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18051116-0049-0000-0000-00004515E040 Message-Id: <20180511162443.GA26088@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-05-11_07:,, 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 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1709140000 definitions=main-1805110154 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, May 10, 2018 at 10:37:54AM -0700, Joel Fernandes wrote: > On Thu, May 10, 2018 at 06:15:46AM -0700, Paul E. McKenney wrote: > [...] > > > Also in rcu_future_gp_cleanup, we call: > > > trace_rcu_future_gp(rnp, rdp, c, > > > needmore ? TPS("CleanupMore") : TPS("Cleanup")); > > > For this case, in the final trace event record, rnp->completed and c will be > > > the same, since c is set to rnp->completed before calling > > > trace_rcu_future_gp. I was thinking they should be different, do you expect > > > them to be the same? > > > > Hmmm... That does look a bit inconsistent. And it currently uses > > rnp->gp_seq instead of rnp->gp_seq_needed despite having the same > > "CleanupMore" name. > > > > Looks like a review of the calls to trace_rcu_this_gp() is in order. > > I see you changed trace_rcu_future_gp to use trace_rcu_this_gp in 15/21.. I > am not sure if the concern is still valid then since you seem to be correctly > getting the future GP in those cases, except for the naming which I suggest > be changed from 'c' to 'future_gp' just for clarity / self-documenting code. Indeed, "c" for "->completed" is completely outdated. ;-) Would you be willing to send a patch providing a better name? Thanx, Paul