Commit c8895e27 authored by Daniel Bristot de Oliveira's avatar Daniel Bristot de Oliveira Committed by Steven Rostedt (VMware)
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trace/osnoise: Support hotplug operations 

Enable and disable osnoise/timerlat thread during on 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/39f98590b3caeb3c32f09526214058efe0e9272a.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 ba998f7d

kernel/trace/trace_osnoise.c

+135 −30
Original line number Diff line number Diff line
@@ -1416,53 +1416,45 @@ static int timerlat_main(void *data) 
#endif /* CONFIG_TIMERLAT_TRACER */



/*

 * stop_per_cpu_kthread - stop per-cpu threads

 *

 * Stop the osnoise sampling htread. Use this on unload and at system

 * shutdown.

 * stop_kthread - stop a workload thread

 */

static void stop_per_cpu_kthreads(void)

static void stop_kthread(unsigned int cpu)

{

	struct task_struct *kthread;

	int cpu;



	for_each_online_cpu(cpu) {

	kthread = per_cpu(per_cpu_osnoise_var, cpu).kthread;

	if (kthread)

		kthread_stop(kthread);

	per_cpu(per_cpu_osnoise_var, cpu).kthread = NULL;

}

}



/*

 * start_per_cpu_kthread - Kick off per-cpu osnoise sampling kthreads

 * stop_per_cpu_kthread - Stop per-cpu threads

 *

 * This starts the kernel thread that will look for osnoise on many

 * cpus.

 * Stop the osnoise sampling htread. Use this on unload and at system

 * shutdown.

 */

static int start_per_cpu_kthreads(struct trace_array *tr)

static void stop_per_cpu_kthreads(void)

{

	struct cpumask *current_mask = &save_cpumask;

	struct task_struct *kthread;

	char comm[24];

	void *main = osnoise_main;

	int cpu;



	get_online_cpus();

	/*

	 * Run only on CPUs in which trace and osnoise are allowed to run.

	 */

	cpumask_and(current_mask, tr->tracing_cpumask, &osnoise_cpumask);

	/*

	 * And the CPU is online.

	 */

	cpumask_and(current_mask, cpu_online_mask, current_mask);

	put_online_cpus();



	for_each_online_cpu(cpu)

		per_cpu(per_cpu_osnoise_var, cpu).kthread = NULL;

		stop_kthread(cpu);



	put_online_cpus();

}



/*

 * start_kthread - Start a workload tread

 */

static int start_kthread(unsigned int cpu)

{

	struct task_struct *kthread;

	void *main = osnoise_main;

	char comm[24];



	for_each_cpu(cpu, current_mask) {

#ifdef CONFIG_TIMERLAT_TRACER

	if (osnoise_data.timerlat_tracer) {

		snprintf(comm, 24, "timerlat/%d", cpu);
@@ -1483,11 +1475,116 @@ static int start_per_cpu_kthreads(struct trace_array *tr) 


	per_cpu(per_cpu_osnoise_var, cpu).kthread = kthread;

	wake_up_process(kthread);



	return 0;

}



/*

 * start_per_cpu_kthread - Kick off per-cpu osnoise sampling kthreads

 *

 * This starts the kernel thread that will look for osnoise on many

 * cpus.

 */

static int start_per_cpu_kthreads(struct trace_array *tr)

{

	struct cpumask *current_mask = &save_cpumask;

	int retval;

	int cpu;



	get_online_cpus();

	/*

	 * Run only on CPUs in which trace and osnoise are allowed to run.

	 */

	cpumask_and(current_mask, tr->tracing_cpumask, &osnoise_cpumask);

	/*

	 * And the CPU is online.

	 */

	cpumask_and(current_mask, cpu_online_mask, current_mask);



	for_each_possible_cpu(cpu)

		per_cpu(per_cpu_osnoise_var, cpu).kthread = NULL;



	for_each_cpu(cpu, current_mask) {

		retval = start_kthread(cpu);

		if (retval) {

			stop_per_cpu_kthreads();

			return retval;

		}

	}



	put_online_cpus();



	return 0;

}



#ifdef CONFIG_HOTPLUG_CPU

static void osnoise_hotplug_workfn(struct work_struct *dummy)

{

	struct trace_array *tr = osnoise_trace;

	unsigned int cpu = smp_processor_id();





	mutex_lock(&trace_types_lock);



	if (!osnoise_busy)

		goto out_unlock_trace;



	mutex_lock(&interface_lock);

	get_online_cpus();



	if (!cpumask_test_cpu(cpu, &osnoise_cpumask))

		goto out_unlock;



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

		goto out_unlock;



	start_kthread(cpu);



out_unlock:

	put_online_cpus();

	mutex_unlock(&interface_lock);

out_unlock_trace:

	mutex_unlock(&trace_types_lock);

}



static DECLARE_WORK(osnoise_hotplug_work, osnoise_hotplug_workfn);



/*

 * osnoise_cpu_init - CPU hotplug online callback function

 */

static int osnoise_cpu_init(unsigned int cpu)

{

	schedule_work_on(cpu, &osnoise_hotplug_work);

	return 0;

}



/*

 * osnoise_cpu_die - CPU hotplug offline callback function

 */

static int osnoise_cpu_die(unsigned int cpu)

{

	stop_kthread(cpu);

	return 0;

}



static void osnoise_init_hotplug_support(void)

{

	int ret;



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

				osnoise_cpu_init, osnoise_cpu_die);

	if (ret < 0)

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



	return;

}

#else /* CONFIG_HOTPLUG_CPU */

static void osnoise_init_hotplug_support(void)

{

	return 0;

}

#endif /* CONFIG_HOTPLUG_CPU */



/*

 * osnoise_cpus_read - Read function for reading the "cpus" file

 * @filp: The active open file structure
@@ -1583,7 +1680,14 @@ osnoise_cpus_write(struct file *filp, const char __user *ubuf, size_t count, 
		osnoise_tracer_stop(tr);



	mutex_lock(&interface_lock);

	/*

	 * osnoise_cpumask is read by CPU hotplug operations.

	 */

	get_online_cpus();



	cpumask_copy(&osnoise_cpumask, osnoise_cpumask_new);



	put_online_cpus();

	mutex_unlock(&interface_lock);



	if (running)
@@ -1940,6 +2044,7 @@ __init static int init_osnoise_tracer(void) 
		return ret;

	}

#endif

	osnoise_init_hotplug_support();



	init_tracefs();