[PATCH v2 3/5] tracing: Add method for recording "func_repeats" events

["Yordan Karadzhov (VMware)" <y.karadz@gmail.com>]

This patch only provides the implementation of the method.
Later we will used it in a combination with a new option for
function tracing.

Signed-off-by: Yordan Karadzhov (VMware) <y.karadz@gmail.com>
---
 kernel/trace/trace.c | 26 ++++++++++++++++++++++++++
 kernel/trace/trace.h |  4 ++++
 2 files changed, 30 insertions(+)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 6fcc159c34a8..0d3d14112f50 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3116,6 +3116,32 @@ static void ftrace_trace_userstack(struct trace_array *tr,
 
 #endif /* CONFIG_STACKTRACE */
 
+void trace_last_func_repeats(struct trace_array *tr,
+			     struct trace_func_repeats *last_info,
+			     unsigned int trace_ctx)
+{
+	struct trace_buffer *buffer = tr->array_buffer.buffer;
+	struct func_repeats_entry *entry;
+	struct ring_buffer_event *event;
+	u64 delta;
+
+	event = __trace_buffer_lock_reserve(buffer, TRACE_FUNC_REPEATS,
+					    sizeof(*entry), trace_ctx);
+	if (!event)
+		return;
+
+	delta = ring_buffer_event_time_stamp(buffer, event) -
+		last_info->ts_last_call;
+
+	entry = ring_buffer_event_data(event);
+	entry->ip = last_info->ip;
+	entry->parent_ip = last_info->parent_ip;
+	entry->count = last_info->count;
+	FUNC_REPEATS_SET_DELTA_TS(entry, delta)
+
+	__buffer_unlock_commit(buffer, event);
+}
+
 /* created for use with alloc_percpu */
 struct trace_buffer_struct {
 	int nesting;
diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 1cd4da7ba769..e1f34119c036 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -701,6 +701,10 @@ static inline void __trace_stack(struct trace_array *tr, unsigned int trace_ctx,
 }
 #endif /* CONFIG_STACKTRACE */
 
+void trace_last_func_repeats(struct trace_array *tr,
+			     struct trace_func_repeats *last_info,
+			     unsigned int trace_ctx);
+
 extern u64 ftrace_now(int cpu);
 
 extern void trace_find_cmdline(int pid, char comm[]);
-- 
2.25.1