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trace/hwlat: Protect kdata->kthread with get/put_online_cpus

Browse source 
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 <pauld@redhat.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Kate Carcia <kcarcia@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Alexandre Chartre <alexandre.chartre@oracle.com>
Cc: Clark Willaims <williams@redhat.com>
Cc: John Kacur <jkacur@redhat.com>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org
Cc: linux-doc@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Suggested-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: Daniel Bristot de Oliveira <bristot@redhat.com>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
This commit is contained in:
Daniel Bristot de Oliveira 2021-06-22 16:42:29 +02:00 committed by Steven Rostedt (VMware)
parent a955d7eac1
commit 039a602db3
1 changed files with 13 additions and 6 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

19
kernel/trace/trace_hwlat.c
View file

@ -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;
}