From 039a602db393c00665e7a3b968b15fb6fd7042b1 Mon Sep 17 00:00:00 2001 From: Daniel Bristot de Oliveira Date: Tue, 22 Jun 2021 16:42:29 +0200 Subject: [PATCH] trace/hwlat: Protect kdata->kthread with get/put_online_cpus 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 a625bfdb844e0..20e31f79ebd90 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