ring-buffer: Add nesting for adding events within events

The ring-buffer code has recusion protection in case tracing ends up tracing
itself, the ring-buffer will detect that it was called at the same context
(normal, softirq, interrupt or NMI), and not continue to record the event.

With the histogram synthetic events, they are called while tracing another
event at the same context. The recusion protection triggers because it
detects tracing at the same context and stops it.

Add ring_buffer_nest_start() and ring_buffer_nest_end() that will notify the
ring buffer that a trace is about to happen within another trace and that it
is intended, and not to trigger the recursion blocking.

Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/include/linux/ring_buffer.h b/include/linux/ring_buffer.h
index 7cb84774c20d..a0233edc0718 100644
--- a/include/linux/ring_buffer.h
+++ b/include/linux/ring_buffer.h
@@ -117,6 +117,9 @@ int ring_buffer_unlock_commit(struct ring_buffer *buffer,
 int ring_buffer_write(struct ring_buffer *buffer,
 		      unsigned long length, void *data);
 
+void ring_buffer_nest_start(struct ring_buffer *buffer);
+void ring_buffer_nest_end(struct ring_buffer *buffer);
+
 struct ring_buffer_event *
 ring_buffer_peek(struct ring_buffer *buffer, int cpu, u64 *ts,
 		 unsigned long *lost_events);