mmiotrace: print overrun counts

Signed-off-by: Pekka Paalanen <pq@iki.fi>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 25 insertions, 0 deletions

diff --git a/kernel/trace/trace_mmiotrace.c b/kernel/trace/trace_mmiotrace.c
index 6d2edbdde93..d0f649a2203 100644
--- a/kernel/trace/trace_mmiotrace.c
+++ b/kernel/trace/trace_mmiotrace.c
@@ -17,11 +17,13 @@ struct header_iter {
 };
 
 static struct trace_array *mmio_trace_array;
+static bool overrun_detected;
 
 static void mmio_reset_data(struct trace_array *tr)
 {
         int cpu;
 
+        overrun_detected = false;
         tr->time_start = ftrace_now(tr->cpu);
 
         for_each_online_cpu(cpu)
@@ -124,12 +126,34 @@ static void mmio_close(struct trace_iterator *iter)
         iter->private = NULL;
 }
 
+static unsigned long count_overruns(struct trace_iterator *iter)
+{
+        int cpu;
+        unsigned long cnt = 0;
+        for_each_online_cpu(cpu) {
+                cnt += iter->overrun[cpu];
+                iter->overrun[cpu] = 0;
+        }
+        return cnt;
+}
+
 static ssize_t mmio_read(struct trace_iterator *iter, struct file *filp,
                                 char __user *ubuf, size_t cnt, loff_t *ppos)
 {
         ssize_t ret;
         struct header_iter *hiter = iter->private;
         struct trace_seq *s = &iter->seq;
+        unsigned long n;
+
+        n = count_overruns(iter);
+        if (n) {
+                /* XXX: This is later than where events were lost. */
+                trace_seq_printf(s, "MARK 0.000000 Lost %lu events.\n", n);
+                if (!overrun_detected)
+                        pr_warning("mmiotrace has lost events.\n");
+                overrun_detected = true;
+                goto print_out;
+        }
 
         if (!hiter)
                 return 0;
@@ -142,6 +166,7 @@ static ssize_t mmio_read(struct trace_iterator *iter, struct file *filp,
                 iter->private = NULL;
         }
 
+print_out:
         ret = trace_seq_to_user(s, ubuf, cnt);
         return (ret == -EBUSY) ? 0 : ret;
 }