Commit 039a602d authored by Daniel Bristot de Oliveira's avatar Daniel Bristot de Oliveira Committed by Steven Rostedt (VMware)
Browse files

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 <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: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
Signed-off-by: default avatarDaniel Bristot de Oliveira <bristot@redhat.com>
Signed-off-by: default avatarSteven Rostedt (VMware) <rostedt@goodmis.org>
parent a955d7ea

kernel/trace/trace_hwlat.c

+13 −6
Original line number Diff line number Diff line
@@ -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;

}