From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753365AbeBCUM5 (ORCPT ); Sat, 3 Feb 2018 15:12:57 -0500 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:45244 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753168AbeBCUMi (ORCPT ); Sat, 3 Feb 2018 15:12:38 -0500 Date: Sat, 3 Feb 2018 01:16:28 -0800 From: "Paul E. McKenney" To: Ildar Ismagilov Cc: Josh Triplett , Steven Rostedt , Mathieu Desnoyers , Lai Jiangshan , linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] srcu: Prevent sdp->srcu_gp_seq_needed_exp counter wrap Reply-To: paulmck@linux.vnet.ibm.com References: <20180131193954.28386-1-devix84@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180131193954.28386-1-devix84@gmail.com> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 x-cbid: 18020320-2213-0000-0000-000002672D87 X-IBM-SpamModules-Scores: X-IBM-SpamModules-Versions: BY=3.00008466; HX=3.00000241; KW=3.00000007; PH=3.00000004; SC=3.00000248; SDB=6.00984559; UDB=6.00499431; IPR=6.00763838; BA=6.00005810; NDR=6.00000001; ZLA=6.00000005; ZF=6.00000009; ZB=6.00000000; ZP=6.00000000; ZH=6.00000000; ZU=6.00000002; MB=3.00019353; XFM=3.00000015; UTC=2018-02-03 20:12:36 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18020320-2214-0000-0000-000058FDACA2 Message-Id: <20180203091628.GF3617@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2018-02-03_05:,, 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-1802030269 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jan 31, 2018 at 10:39:53PM +0300, Ildar Ismagilov wrote: > Signed-off-by: Ildar Ismagilov I did apply this for testing and review, thank you and good eyes! However, I had to: 1. hand-edit it to make it work against the rcu/dev branch of my -rcu tree: git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git 2. fill out the commit logs. Please see below for the updated patch, and please let me know if I messed something up. In the future, could you please apply your patches against the rcu/dev branch of -rcu and provide more complete commit logs? The commit log should describe the problem and how that problem is fixed. Also, are you able to test these using rcutorture? If not, let's get you set up for that, as I am prone to testing backlogs just now. Plus I am writing this while 34,000 feet over Western Australia. So it would mean fewer delays for you if you could test your own patches. ;-) Thanx, Paul ------------------------------------------------------------------------ commit 753abb606ba61012c8838c73e2c888aea20efe13 Author: Ildar Ismagilov Date: Wed Jan 31 22:39:53 2018 +0300 srcu: Prevent sdp->srcu_gp_seq_needed_exp counter wrap SRCU checks each srcu_data structure's grace-period number for counter wrap four times per cycle by default. This frequency guarantees that normal comparisons will detect potential wrap. However, the expedited grace-period number is not checked. The consquences are not too horrible (a failure to expedite a grace period when requested), but it would be good to avoid such things. This commit therefore adds this check to the expedited grace-period number. Signed-off-by: Ildar Ismagilov Signed-off-by: Paul E. McKenney diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index 2878387d4189..ad3e1aa5e6ea 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -579,6 +579,9 @@ static void srcu_gp_end(struct srcu_struct *sp) if (ULONG_CMP_GE(gpseq, sdp->srcu_gp_seq_needed + 100)) sdp->srcu_gp_seq_needed = gpseq; + if (ULONG_CMP_GE(gpseq, + sdp->srcu_gp_seq_needed_exp + 100)) + sdp->srcu_gp_seq_needed_exp = gpseq; spin_unlock_irqrestore_rcu_node(sdp, flags); } }