Commit ba998f7d authored by Daniel Bristot de Oliveira's avatar Daniel Bristot de Oliveira Committed by Steven Rostedt (VMware)
Browse files

trace/hwlat: Support hotplug operations 

Enable and disable hwlat thread during cpu hotplug online
and offline operations, respectivelly.

Link: https://lore.kernel.org/linux-doc/20210621134636.5b332226@oasis.local.home/
Link: https://lkml.kernel.org/r/52012d25ea35491a0f8088b947864d8df8e25157.1624372313.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 039a602d

kernel/trace/trace_hwlat.c

+65 −0
Original line number Diff line number Diff line
@@ -466,6 +466,7 @@ static void stop_cpu_kthread(unsigned int cpu) 
	kthread = per_cpu(hwlat_per_cpu_data, cpu).kthread;

	if (kthread)

		kthread_stop(kthread);

	per_cpu(hwlat_per_cpu_data, cpu).kthread = NULL;

}



/*
@@ -506,6 +507,68 @@ static int start_cpu_kthread(unsigned int cpu) 
	return 0;

}



#ifdef CONFIG_HOTPLUG_CPU

static void hwlat_hotplug_workfn(struct work_struct *dummy)

{

	struct trace_array *tr = hwlat_trace;

	unsigned int cpu = smp_processor_id();



	mutex_lock(&trace_types_lock);

	mutex_lock(&hwlat_data.lock);

	get_online_cpus();



	if (!hwlat_busy || hwlat_data.thread_mode != MODE_PER_CPU)

		goto out_unlock;



	if (!cpumask_test_cpu(cpu, tr->tracing_cpumask))

		goto out_unlock;



	start_cpu_kthread(cpu);



out_unlock:

	put_online_cpus();

	mutex_unlock(&hwlat_data.lock);

	mutex_unlock(&trace_types_lock);

}



static DECLARE_WORK(hwlat_hotplug_work, hwlat_hotplug_workfn);



/*

 * hwlat_cpu_init - CPU hotplug online callback function

 */

static int hwlat_cpu_init(unsigned int cpu)

{

	schedule_work_on(cpu, &hwlat_hotplug_work);

	return 0;

}



/*

 * hwlat_cpu_die - CPU hotplug offline callback function

 */

static int hwlat_cpu_die(unsigned int cpu)

{

	stop_cpu_kthread(cpu);

	return 0;

}



static void hwlat_init_hotplug_support(void)

{

	int ret;



	ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "trace/hwlat:online",

				hwlat_cpu_init, hwlat_cpu_die);

	if (ret < 0)

		pr_warn(BANNER "Error to init cpu hotplug support\n");



	return;

}

#else /* CONFIG_HOTPLUG_CPU */

static void hwlat_init_hotplug_support(void)

{

	return;

}

#endif /* CONFIG_HOTPLUG_CPU */



/*

 * start_per_cpu_kthreads - Kick off the hardware latency sampling/detector kthreads

 *
@@ -822,6 +885,8 @@ __init static int init_hwlat_tracer(void) 
	if (ret)

		return ret;



	hwlat_init_hotplug_support();



	init_tracefs();



	return 0;