From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932673AbeEaCvo (ORCPT ); Wed, 30 May 2018 22:51:44 -0400 Received: from lgeamrelo13.lge.com ([156.147.23.53]:56320 "EHLO lgeamrelo11.lge.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S932621AbeEaCvm (ORCPT ); Wed, 30 May 2018 22:51:42 -0400 X-Original-SENDERIP: 156.147.1.121 X-Original-MAILFROM: byungchul.park@lge.com X-Original-SENDERIP: 10.177.220.135 X-Original-MAILFROM: byungchul.park@lge.com Subject: Re: [RFC] rcu: Check the range of jiffies_till_xxx_fqs on setting them From: Byungchul Park To: paulmck@linux.vnet.ibm.com Cc: jiangshanlai@gmail.com, josh@joshtriplett.org, rostedt@goodmis.org, mathieu.desnoyers@efficios.com, linux-kernel@vger.kernel.org, kernel-team@lge.com, joel@joelfernandes.org References: <1527578616-5595-1-git-send-email-byungchul.park@lge.com> <20180529120155.GC3803@linux.vnet.ibm.com> <07271222-2e1d-2dc8-1648-4c53d710a092@lge.com> Message-ID: <3d2d8dec-445a-da31-dbe0-34b2331523ed@lge.com> Date: Thu, 31 May 2018 11:51:40 +0900 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.8.0 MIME-Version: 1.0 In-Reply-To: <07271222-2e1d-2dc8-1648-4c53d710a092@lge.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2018-05-31 11:18, Byungchul Park wrote: > On 2018-05-29 21:01, Paul E. McKenney wrote: > >> One approach would be to embed the kernel_params_ops structure inside >> another structure containing the limits, then just have two structures. >> Perhaps something like this already exists?  I don't see it right off, >> but then again, I am not exactly an expert on module_param. >> >> Thoughts? > > Unfortunately, I couldn't find it. There might be no way to verify > range of a variable except the way I did. Could you give your opinion > about whether I should go on it? Like.. ----->8----- diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 4e96761..eb54d7d 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -518,8 +518,38 @@ void rcu_all_qs(void) static ulong jiffies_till_next_fqs = ULONG_MAX; static bool rcu_kick_kthreads; -module_param(jiffies_till_first_fqs, ulong, 0644); -module_param(jiffies_till_next_fqs, ulong, 0644); +static int param_set_first_fqs_jiffies(const char *val, const struct kernel_param *kp) +{ + ulong j; + int ret = kstrtoul(val, 0, &j); + + if (!ret) + WRITE_ONCE(*(ulong *)kp->arg, (j > HZ) ? HZ : j); + return ret; +} + +static int param_set_next_fqs_jiffies(const char *val, const struct kernel_param *kp) +{ + ulong j; + int ret = kstrtoul(val, 0, &j); + + if (!ret) + WRITE_ONCE(*(ulong *)kp->arg, (j > HZ) ? HZ : (j ?: 1)); + return ret; +} + +static struct kernel_param_ops first_fqs_jiffies_ops = { + .set = param_set_first_fqs_jiffies, + .get = param_get_ulong, +}; + +static struct kernel_param_ops next_fqs_jiffies_ops = { + .set = param_set_next_fqs_jiffies, + .get = param_get_ulong, +}; + +module_param_cb(jiffies_till_first_fqs, &first_fqs_jiffies_ops, &jiffies_till_first_fqs, 0644); +module_param_cb(jiffies_till_next_fqs, &next_fqs_jiffies_ops, &jiffies_till_next_fqs, 0644); module_param(rcu_kick_kthreads, bool, 0644); /* @@ -2129,10 +2159,6 @@ static int __noreturn rcu_gp_kthread(void *arg) /* Handle quiescent-state forcing. */ first_gp_fqs = true; j = jiffies_till_first_fqs; - if (j > HZ) { - j = HZ; - jiffies_till_first_fqs = HZ; - } ret = 0; for (;;) { if (!ret) { @@ -2167,13 +2193,6 @@ static int __noreturn rcu_gp_kthread(void *arg) WRITE_ONCE(rsp->gp_activity, jiffies); ret = 0; /* Force full wait till next FQS. */ j = jiffies_till_next_fqs; - if (j > HZ) { - j = HZ; - jiffies_till_next_fqs = HZ; - } else if (j < 1) { - j = 1; - jiffies_till_next_fqs = 1; - } } else { /* Deal with stray signal. */ cond_resched_tasks_rcu_qs(); -- Thanks, Byungchul