From: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx> Enable and disable hwlat thread during cpu hotplug online and offline operations, respectivelly. Link: https://lore.kernel.org/linux-doc/20210621134636.5b332226@xxxxxxxxxxxxxxxx/ Link: https://lkml.kernel.org/r/52012d25ea35491a0f8088b947864d8df8e25157.1624372313.git.bristot@xxxxxxxxxx Cc: Phil Auld <pauld@xxxxxxxxxx> Cc: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> Cc: Kate Carcia <kcarcia@xxxxxxxxxx> Cc: Jonathan Corbet <corbet@xxxxxxx> Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Alexandre Chartre <alexandre.chartre@xxxxxxxxxx> Cc: Clark Willaims <williams@xxxxxxxxxx> Cc: John Kacur <jkacur@xxxxxxxxxx> Cc: Juri Lelli <juri.lelli@xxxxxxxxxx> Cc: Borislav Petkov <bp@xxxxxxxxx> Cc: "H. Peter Anvin" <hpa@xxxxxxxxx> Cc: x86@xxxxxxxxxx Cc: linux-doc@xxxxxxxxxxxxxxx Cc: linux-kernel@xxxxxxxxxxxxxxx Suggested-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx> Signed-off-by: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx> Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx> --- kernel/trace/trace_hwlat.c | 65 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 65 insertions(+) diff --git a/kernel/trace/trace_hwlat.c b/kernel/trace/trace_hwlat.c index 20e31f79ebd9..a6c0cdaf4b87 100644 --- a/kernel/trace/trace_hwlat.c +++ b/kernel/trace/trace_hwlat.c @@ -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; -- 2.30.2
