[for-next][PATCH 36/46] tracing: Use the ring-buffer nesting to allow synthetic events to be traced

Steven Rostedt
2018-03-21T02:22:51Z

[-- Attachment #1: 0036-tracing-Use-the-ring-buffer-nesting-to-allow-synthet.patch --]
[-- Type: text/plain, Size: 1765 bytes --]

From: "Steven Rostedt (VMware)" <rostedt@goodmis.org>

Synthetic events can be done within the recording of other events. Notify
the ring buffer via ring_buffer_nest_start() and ring_buffer_nest_end() that
this is intended and not to block it due to its recursion protection.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
kernel/trace/trace_events_hist.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/kernel/trace/trace_events_hist.c b/kernel/trace/trace_events_hist.c
index f7d0da20c5c8..4f027642ceef 100644
--- a/kernel/trace/trace_events_hist.c
+++ b/kernel/trace/trace_events_hist.c
@@ -640,6 +640,7 @@ static notrace void trace_event_raw_event_synth(void *__data,
struct trace_event_file *trace_file = __data;
struct synth_trace_event *entry;
struct trace_event_buffer fbuffer;
+ struct ring_buffer *buffer;
struct synth_event *event;
unsigned int i, n_u64;
int fields_size = 0;
@@ -651,10 +652,17 @@ static notrace void trace_event_raw_event_synth(void *__data,

fields_size = event->n_u64 * sizeof(u64);

+ /*
+ * Avoid ring buffer recursion detection, as this event
+ * is being performed within another event.
+ */
+ buffer = trace_file->tr->trace_buffer.buffer;
+ ring_buffer_nest_start(buffer);
+
entry = trace_event_buffer_reserve(&fbuffer, trace_file,
sizeof(*entry) + fields_size);
if (!entry)
- return;
+ goto out;

for (i = 0, n_u64 = 0; i < event->n_fields; i++) {
if (event->fields[i]->is_string) {
@@ -670,6 +678,8 @@ static notrace void trace_event_raw_event_synth(void *__data,
}

trace_event_buffer_commit(&fbuffer);
+out:
+ ring_buffer_nest_end(buffer);
}

static void free_synth_event_print_fmt(struct trace_event_call *call)
--
2.15.1