1 files changed, 55 insertions, 0 deletions

diff --git a/kernel/trace/trace_hwlat.c b/kernel/trace/trace_hwlat.c
index 08dfabe4e862..65aab3914a56 100644
--- a/kernel/trace/trace_hwlat.c
+++ b/kernel/trace/trace_hwlat.c
@@ -42,6 +42,7 @@
 #include <linux/kthread.h>
 #include <linux/tracefs.h>
 #include <linux/uaccess.h>
+#include <linux/cpumask.h>
 #include <linux/delay.h>
 #include "trace.h"
 
@@ -211,6 +212,57 @@ out:
         return ret;
 }
 
+static struct cpumask save_cpumask;
+static bool disable_migrate;
+
+static void move_to_next_cpu(void)
+{
+        static struct cpumask *current_mask;
+        int next_cpu;
+
+        if (disable_migrate)
+                return;
+
+        /* Just pick the first CPU on first iteration */
+        if (!current_mask) {
+                current_mask = &save_cpumask;
+                get_online_cpus();
+                cpumask_and(current_mask, cpu_online_mask, tracing_buffer_mask);
+                put_online_cpus();
+                next_cpu = cpumask_first(current_mask);
+                goto set_affinity;
+        }
+
+        /*
+         * If for some reason the user modifies the CPU affinity
+         * of this thread, than stop migrating for the duration
+         * of the current test.
+         */
+        if (!cpumask_equal(current_mask, &current->cpus_allowed))
+                goto disable;
+
+        get_online_cpus();
+        cpumask_and(current_mask, cpu_online_mask, tracing_buffer_mask);
+        next_cpu = cpumask_next(smp_processor_id(), current_mask);
+        put_online_cpus();
+
+        if (next_cpu >= nr_cpu_ids)
+                next_cpu = cpumask_first(current_mask);
+
+ set_affinity:
+        if (next_cpu >= nr_cpu_ids) /* Shouldn't happen! */
+                goto disable;
+
+        cpumask_clear(current_mask);
+        cpumask_set_cpu(next_cpu, current_mask);
+
+        sched_setaffinity(0, current_mask);
+        return;
+
+ disable:
+        disable_migrate = true;
+}
+
 /*
  * kthread_fn - The CPU time sampling/hardware latency detection kernel thread
  *
@@ -230,6 +282,8 @@ static int kthread_fn(void *data)
 
         while (!kthread_should_stop()) {
 
+                move_to_next_cpu();
+
                 local_irq_disable();
                 get_sample();
                 local_irq_enable();
@@ -473,6 +527,7 @@ static int hwlat_tracer_init(struct trace_array *tr)
 
         hwlat_trace = tr;
 
+        disable_migrate = false;
         hwlat_data.count = 0;
         tr->max_latency = 0;
         save_tracing_thresh = tracing_thresh;