Enable and disable hwlat thread during cpu hotplug online
and offline operations, respectivelly.
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
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
Signed-off-by: Daniel Bristot de Oliveira <bristot@xxxxxxxxxx>
---
kernel/trace/trace.c | 6 ++++++
kernel/trace/trace_hwlat.c | 34 ++++++++++++++++++++++++++++++++++
2 files changed, 40 insertions(+)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 9299057feb56..c094865e2f71 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -5064,7 +5064,13 @@ int tracing_set_cpumask(struct trace_array *tr,
arch_spin_unlock(&tr->max_lock);
local_irq_enable();
+ /*
+ * tracing_cpumask is read by tracers that support CPU
+ * hotplug.
+ */
+ get_online_cpus();
cpumask_copy(tr->tracing_cpumask, tracing_cpumask_new);
+ put_online_cpus();
return 0;
}
diff --git a/kernel/trace/trace_hwlat.c b/kernel/trace/trace_hwlat.c
index 6c6918e86087..9fcfd588c4f6 100644
--- a/kernel/trace/trace_hwlat.c
+++ b/kernel/trace/trace_hwlat.c
@@ -490,6 +490,35 @@ static int start_cpu_kthread(unsigned int cpu)
return 0;
}
+/*
+ * hwlat_cpu_init - CPU hotplug online callback function
+ */
+static int hwlat_cpu_init(unsigned int cpu)
+{
+ struct trace_array *tr = hwlat_trace;
+
+ if (!hwlat_busy)
+ return 0;
+
+ if (!cpumask_test_cpu(cpu, tr->tracing_cpumask))
+ return 0;
+
+ return start_cpu_kthread(cpu);
+}
+
+/*
+ * hwlat_cpu_die - CPU hotplug offline callback function
+ */
+static int hwlat_cpu_die(unsigned int cpu)
+{
+ if (!hwlat_busy)
+ return 0;
+
+ stop_cpu_kthread(cpu);
+
+ return 0;
+}
+
/*
* start_per_cpu_kthreads - Kick off the hardware latency sampling/detector kthreads
*
@@ -903,6 +932,11 @@ __init static int init_hwlat_tracer(void)
if (ret)
return 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");
+
init_tracefs();
return 0;
--
2.31.1
