2 files changed, 21 insertions, 0 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 58435415b366..f147f198b9a6 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -1478,6 +1478,17 @@ void trace_seq_print_cont(struct trace_seq *s, struct trace_iterator *iter)
                 trace_seq_putc(s, '\n');
 }
 
+static void test_cpu_buff_start(struct trace_iterator *iter)
+{
+        struct trace_seq *s = &iter->seq;
+
+        if (cpu_isset(iter->cpu, iter->started))
+                return;
+
+        cpu_set(iter->cpu, iter->started);
+        trace_seq_printf(s, "##### CPU %u buffer started ####\n", iter->cpu);
+}
+
 static enum print_line_t
 print_lat_fmt(struct trace_iterator *iter, unsigned int trace_idx, int cpu)
 {
@@ -1497,6 +1508,8 @@ print_lat_fmt(struct trace_iterator *iter, unsigned int trace_idx, int cpu)
         if (entry->type == TRACE_CONT)
                 return TRACE_TYPE_HANDLED;
 
+        test_cpu_buff_start(iter);
+
         next_entry = find_next_entry(iter, NULL, &next_ts);
         if (!next_entry)
                 next_ts = iter->ts;
@@ -1612,6 +1625,8 @@ static enum print_line_t print_trace_fmt(struct trace_iterator *iter)
         if (entry->type == TRACE_CONT)
                 return TRACE_TYPE_HANDLED;
 
+        test_cpu_buff_start(iter);
+
         comm = trace_find_cmdline(iter->ent->pid);
 
         t = ns2usecs(iter->ts);
@@ -2631,6 +2646,10 @@ static int tracing_open_pipe(struct inode *inode, struct file *filp)
                 return -ENOMEM;
 
         mutex_lock(&trace_types_lock);
+
+        /* trace pipe does not show start of buffer */
+        cpus_setall(iter->started);
+
         iter->tr = &global_trace;
         iter->trace = current_trace;
         filp->private_data = iter;
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index cfda9d219e66..978145088fb8 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -277,6 +277,8 @@ struct trace_iterator {
         unsigned long           iter_flags;
         loff_t                  pos;
         long                    idx;
+
+        cpumask_t               started;
 };
 
 int tracing_is_enabled(void);