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dkim=none (message not signed) header.d=none;vger.kernel.org; dmarc=none action=none header.from=windriver.com; Received: from SN6PR11MB3309.namprd11.prod.outlook.com (2603:10b6:805:bd::14) by SN6PR11MB3088.namprd11.prod.outlook.com (2603:10b6:805:ce::22) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4242.21; Fri, 25 Jun 2021 01:45:00 +0000 Received: from SN6PR11MB3309.namprd11.prod.outlook.com ([fe80::a170:9c84:bd22:f77c]) by SN6PR11MB3309.namprd11.prod.outlook.com ([fe80::a170:9c84:bd22:f77c%6]) with mapi id 15.20.4264.023; Fri, 25 Jun 2021 01:45:00 +0000 Subject: Re: [PATCH v3] rcuscale: Console output claims too few grace periods To: paulmck@kernel.org Cc: dave@stgolabs.net, josh@joshtriplett.org, rostedt@goodmis.org, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com, joel@joelfernandes.org, linux-kernel@vger.kernel.org, rcu@vger.kernel.org References: <20210624143424.16158-1-jiangong.han@windriver.com> <20210624164045.GU4397@paulmck-ThinkPad-P17-Gen-1> From: "Han, Jiangong" Message-ID: <0f251dba-0e0d-970f-904a-24b540a175be@windriver.com> Date: Fri, 25 Jun 2021 09:44:43 +0800 User-Agent: Mozilla/5.0 (X11; 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Br, Jiangong 在 2021/6/25 上午12:40, Paul E. McKenney 写道: > [Please note: This e-mail is from an EXTERNAL e-mail address] > > On Thu, Jun 24, 2021 at 10:34:24PM +0800, Jiangong.Han wrote: >> The rcuscale console output claims N grace periods, numbered from zero >> to N, which means that there were really N+1 grace periods. The root >> cause of this bug is that rcu_scale_writer() stores the number of the >> last grace period (numbered from zero) into writer_n_durations[me] >> instead of the number of grace periods. This commit therefore assigns >> the actual number of grace periods to writer_n_durations[me], and also >> makes the corresponding adjustment to the loop outputting per-grace-period >> measurements. >> >> Sample of old console output: >> rcu-scale: writer 0 gps: 133 >> ...... >> rcu-scale: 0 writer-duration: 0 44003961 >> rcu-scale: 0 writer-duration: 1 32003582 >> ...... >> rcu-scale: 0 writer-duration: 132 28004391 >> rcu-scale: 0 writer-duration: 133 27996410 >> >> Sample of new console output: >> rcu-scale: writer 0 gps: 134 >> ...... >> rcu-scale: 0 writer-duration: 0 44003961 >> rcu-scale: 0 writer-duration: 1 32003582 >> ...... >> rcu-scale: 0 writer-duration: 132 28004391 >> rcu-scale: 0 writer-duration: 133 27996410 >> >> Signed-off-by: Jiangong.Han >> Signed-off-by: Paul E. McKenney > I already have it queued in -rcu here: > > 4c154a910344 ("rcuscale: Console output claims too few grace periods") > > Or did you find an error in my wordsmithed version of your commit log? > If so, please point out the error explicitly. (It looks identical to me, > but I could easily be missing something.) > > Thanx, Paul > >> --- >> kernel/rcu/rcuscale.c | 4 ++-- >> 1 file changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/kernel/rcu/rcuscale.c b/kernel/rcu/rcuscale.c >> index dca51fe9c73f..2cc34a22a506 100644 >> --- a/kernel/rcu/rcuscale.c >> +++ b/kernel/rcu/rcuscale.c >> @@ -487,7 +487,7 @@ rcu_scale_writer(void *arg) >> if (gp_async) { >> cur_ops->gp_barrier(); >> } >> - writer_n_durations[me] = i_max; >> + writer_n_durations[me] = i_max + 1; >> torture_kthread_stopping("rcu_scale_writer"); >> return 0; >> } >> @@ -561,7 +561,7 @@ rcu_scale_cleanup(void) >> wdpp = writer_durations[i]; >> if (!wdpp) >> continue; >> - for (j = 0; j <= writer_n_durations[i]; j++) { >> + for (j = 0; j < writer_n_durations[i]; j++) { >> wdp = &wdpp[j]; >> pr_alert("%s%s %4d writer-duration: %5d %llu\n", >> scale_type, SCALE_FLAG, >> -- >> 2.17.1 >>