From: "Steven Rostedt (VMware)" Date: Wed, 7 Feb 2018 17:29:46 -0500 Subject: [PATCH 46/48] tracing: Use the ring-buffer nesting to allow synthetic events to be traced Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.16/older/patches-4.16.8-rt3.tar.xz 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) (cherry picked from commit 92c571543120ffed5e725f5b57b9de0b535e9d0a) Signed-off-by: Sebastian Andrzej Siewior --- kernel/trace/trace_events_hist.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) --- a/kernel/trace/trace_events_hist.c +++ b/kernel/trace/trace_events_hist.c @@ -640,6 +640,7 @@ static notrace void trace_event_raw_even 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_even 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_even } trace_event_buffer_commit(&fbuffer); +out: + ring_buffer_nest_end(buffer); } static void free_synth_event_print_fmt(struct trace_event_call *call)