From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-20.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id E1971C63797 for ; Wed, 21 Jul 2021 21:04:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id CA6A66138C for ; Wed, 21 Jul 2021 21:04:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230287AbhGUUYO (ORCPT ); Wed, 21 Jul 2021 16:24:14 -0400 Received: from mail.kernel.org ([198.145.29.99]:34834 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229908AbhGUUYH (ORCPT ); Wed, 21 Jul 2021 16:24:07 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 51F0261264; Wed, 21 Jul 2021 21:04:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1626901483; bh=BRCA3cizbBxreJRulOEZaGT1dH+vBvoN0yRwdhOIDXA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=NqjY/CkneNItcKa12J60Xuq2mrGrTF1kYM1PZBkd68l3VxTc8fsEVqFgpqskGPCls tzjCqRO1272inrIIrkoJMxzK47COzOD9mjoWZfiKGLgLOZDiNqjzbgrZ9aD9oDkyeZ W7DqFsjalpPGm4uNPSUVu/FHOxPZK7Cejdpl/mOBOhi3abaut6e0+AqCDt4sLuRmep 48CbLY9fdItr7ECvRlE5R8UKPZJcuLPyflz5QH6yPQe0CeTaypL12EgV1G91/B69qj oEDrj2yq8HtCrlkl3XH5b8j8RzYpSvjje8zTsqlkxsXbI7RMh/Xg8A4DoJfMQt0x85 macz8cEv/CXWQ== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 20CF55C0A11; Wed, 21 Jul 2021 14:04:43 -0700 (PDT) From: "Paul E. McKenney" To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com, mingo@kernel.org, jiangshanlai@gmail.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@joelfernandes.org, "Jiangong.Han" , "Paul E . McKenney" Subject: [PATCH rcu 3/7] rcuscale: Console output claims too few grace periods Date: Wed, 21 Jul 2021 14:04:37 -0700 Message-Id: <20210721210441.796995-3-paulmck@kernel.org> X-Mailer: git-send-email 2.31.1.189.g2e36527f23 In-Reply-To: <20210721210421.GA788053@paulmck-ThinkPad-P17-Gen-1> References: <20210721210421.GA788053@paulmck-ThinkPad-P17-Gen-1> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: "Jiangong.Han" 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 --- 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 dca51fe9c73f2..2cc34a22a5060 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, -- 2.31.1.189.g2e36527f23