From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755579AbcEYBWH (ORCPT ); Tue, 24 May 2016 21:22:07 -0400 Received: from mail-oi0-f68.google.com ([209.85.218.68]:36070 "EHLO mail-oi0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751346AbcEYBWF (ORCPT ); Tue, 24 May 2016 21:22:05 -0400 From: Boqun Feng To: linux-kernel@vger.kernel.org Cc: "Paul E. McKenney" , Josh Triplett , Steven Rostedt , Mathieu Desnoyers , Lai Jiangshan , fengguang.wu@intel.com, Boqun Feng Subject: [PATCH] rcuperf: Don't treat gp_exp mis-setting as a WARN Date: Wed, 25 May 2016 09:25:33 +0800 Message-Id: <1464139533-26551-1-git-send-email-boqun.feng@gmail.com> X-Mailer: git-send-email 2.8.2 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 0day found a boot warning triggered in rcu_perf_writer() on !SMP kernel: WARN_ON(rcu_gp_is_normal() && gp_exp); , the root cause of which is trying to measure expedited grace periods(by setting gp_exp to true by default) when all the grace periods are normal(TINY RCU only has normal grace periods). However, such a mis-setting would only result in failing to measure the performance for a specific kind of grace periods, therefore using a WARN_ON to check this is a little overkilling. We could handle this inside rcuperf module via some error messages to tell users about the mis-settings. Therefore this patch removes the WARN_ON in rcu_perf_writer() and handles those checkings in rcu_perf_init() with plain if() code. Moreover, this patch changes the default value of gp_exp to 1) align with rcutorture tests and 2) make the default setting work for all RCU implementations by default. Suggested-by: Paul E. McKenney Signed-off-by: Boqun Feng Fixes: http://lkml.kernel.org/r/57411b10.mFvG0+AgcrMXGtcj%fengguang.wu@intel.com --- kernel/rcu/rcuperf.c | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) diff --git a/kernel/rcu/rcuperf.c b/kernel/rcu/rcuperf.c index 3cee0d8393ed..8ce4eecff319 100644 --- a/kernel/rcu/rcuperf.c +++ b/kernel/rcu/rcuperf.c @@ -58,7 +58,7 @@ MODULE_AUTHOR("Paul E. McKenney "); #define VERBOSE_PERFOUT_ERRSTRING(s) \ do { if (verbose) pr_alert("%s" PERF_FLAG "!!! %s\n", perf_type, s); } while (0) -torture_param(bool, gp_exp, true, "Use expedited GP wait primitives"); +torture_param(bool, gp_exp, false, "Use expedited GP wait primitives"); torture_param(int, holdoff, 10, "Holdoff time before test start (s)"); torture_param(int, nreaders, -1, "Number of RCU reader threads"); torture_param(int, nwriters, -1, "Number of RCU updater threads"); @@ -363,8 +363,6 @@ rcu_perf_writer(void *arg) u64 *wdpp = writer_durations[me]; VERBOSE_PERFOUT_STRING("rcu_perf_writer task started"); - WARN_ON(rcu_gp_is_expedited() && !rcu_gp_is_normal() && !gp_exp); - WARN_ON(rcu_gp_is_normal() && gp_exp); WARN_ON(!wdpp); set_cpus_allowed_ptr(current, cpumask_of(me % nr_cpu_ids)); sp.sched_priority = 1; @@ -631,6 +629,16 @@ rcu_perf_init(void) firsterr = -ENOMEM; goto unwind; } + if (rcu_gp_is_expedited() && !rcu_gp_is_normal() && !gp_exp) { + VERBOSE_PERFOUT_ERRSTRING("All grace periods expedited, no normal ones to measure!"); + firsterr = -EINVAL; + goto unwind; + } + if (rcu_gp_is_normal() && gp_exp) { + VERBOSE_PERFOUT_ERRSTRING("All grace periods normal, no expedited ones to measure!"); + firsterr = -EINVAL; + goto unwind; + } for (i = 0; i < nrealwriters; i++) { writer_durations[i] = kcalloc(MAX_MEAS, sizeof(*writer_durations[i]), -- 2.8.2