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=-13.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 70B8DC49EC8 for ; Sat, 26 Jun 2021 13:05:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5A73161C68 for ; Sat, 26 Jun 2021 13:05:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230283AbhFZNIO (ORCPT ); Sat, 26 Jun 2021 09:08:14 -0400 Received: from mail.kernel.org ([198.145.29.99]:34210 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230108AbhFZNIB (ORCPT ); Sat, 26 Jun 2021 09:08:01 -0400 Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id B7A2861C50; Sat, 26 Jun 2021 13:05:39 +0000 (UTC) Received: from rostedt by gandalf.local.home with local (Exim 4.94.2) (envelope-from ) id 1lx80A-000Eq5-Po; Sat, 26 Jun 2021 09:05:38 -0400 Message-ID: <20210626130538.648729939@goodmis.org> User-Agent: quilt/0.66 Date: Sat, 26 Jun 2021 09:04:26 -0400 From: Steven Rostedt To: linux-kernel@vger.kernel.org Cc: Ingo Molnar , Andrew Morton , Phil Auld , Sebastian Andrzej Siewior , Kate Carcia , Jonathan Corbet , Ingo Molnar , Peter Zijlstra , Thomas Gleixner , Alexandre Chartre , Clark Willaims , John Kacur , Juri Lelli , Borislav Petkov , "H. Peter Anvin" , x86@kernel.org, linux-doc@vger.kernel.org, Daniel Bristot de Oliveira Subject: [for-next][PATCH 22/24] trace/hwlat: Protect kdata->kthread with get/put_online_cpus References: <20210626130404.033700863@goodmis.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org From: Daniel Bristot de Oliveira In preparation to the hotplug support, protect kdata->kthread with get/put_online_cpus() to avoid concurrency with hotplug operations. Link: https://lore.kernel.org/linux-doc/20210621134636.5b332226@oasis.local.home/ Link: https://lkml.kernel.org/r/8bdb2a56f46abfd301d6fffbf43448380c09a6f5.1624372313.git.bristot@redhat.com Cc: Phil Auld Cc: Sebastian Andrzej Siewior Cc: Kate Carcia Cc: Jonathan Corbet Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Alexandre Chartre Cc: Clark Willaims Cc: John Kacur Cc: Juri Lelli Cc: Borislav Petkov Cc: "H. Peter Anvin" Cc: x86@kernel.org Cc: linux-doc@vger.kernel.org Cc: linux-kernel@vger.kernel.org Suggested-by: Steven Rostedt (VMware) Signed-off-by: Daniel Bristot de Oliveira Signed-off-by: Steven Rostedt (VMware) --- kernel/trace/trace_hwlat.c | 19 +++++++++++++------ 1 file changed, 13 insertions(+), 6 deletions(-) diff --git a/kernel/trace/trace_hwlat.c b/kernel/trace/trace_hwlat.c index a625bfdb844e..20e31f79ebd9 100644 --- a/kernel/trace/trace_hwlat.c +++ b/kernel/trace/trace_hwlat.c @@ -396,13 +396,19 @@ static int kthread_fn(void *data) static void stop_single_kthread(void) { struct hwlat_kthread_data *kdata = get_cpu_data(); - struct task_struct *kthread = kdata->kthread; + struct task_struct *kthread; + + get_online_cpus(); + kthread = kdata->kthread; if (!kthread) - return; + goto out_put_cpus; kthread_stop(kthread); kdata->kthread = NULL; + +out_put_cpus: + put_online_cpus(); } @@ -419,20 +425,19 @@ static int start_single_kthread(struct trace_array *tr) struct task_struct *kthread; int next_cpu; + get_online_cpus(); if (kdata->kthread) - return 0; + goto out_put_cpus; kthread = kthread_create(kthread_fn, NULL, "hwlatd"); if (IS_ERR(kthread)) { pr_err(BANNER "could not start sampling thread\n"); + put_online_cpus(); return -ENOMEM; } - /* Just pick the first CPU on first iteration */ - get_online_cpus(); cpumask_and(current_mask, cpu_online_mask, tr->tracing_cpumask); - put_online_cpus(); if (hwlat_data.thread_mode == MODE_ROUND_ROBIN) { next_cpu = cpumask_first(current_mask); @@ -446,6 +451,8 @@ static int start_single_kthread(struct trace_array *tr) kdata->kthread = kthread; wake_up_process(kthread); +out_put_cpus: + put_online_cpus(); return 0; } -- 2.30.2