tracing: expand the ring buffers when an event is activated

To save memory, the tracer ring buffers are set to a minimum.
The activating of a trace expands the ring buffer size. This patch
adds this expanding, when an event is activated.

Signed-off-by: Steven Rostedt <srostedt@redhat.com>

1 files changed, 20 insertions, 0 deletions

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 0c1dc185085..35ee63ae412 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2357,6 +2357,26 @@ static int tracing_resize_ring_buffer(unsigned long size)
 	return ret;
 }
 
+/**
+ * tracing_update_buffers - used by tracing facility to expand ring buffers
+ *
+ * To save on memory when the tracing is never used on a system with it
+ * configured in. The ring buffers are set to a minimum size. But once
+ * a user starts to use the tracing facility, then they need to grow
+ * to their default size.
+ *
+ * This function is to be called when a tracer is about to be used.
+ */
+int tracing_update_buffers(void)
+{
+	int ret = 0;
+
+	if (!ring_buffer_expanded)
+		ret = tracing_resize_ring_buffer(trace_buf_size);
+
+	return ret;
+}
+
 struct trace_option_dentry;
 
 static struct trace_option_dentry *