tracing/events: Add trace_event boot option
We already have ftrace= boot option, and this adds a similar
boot option for trace events, so allow trace events to be
enabled at boot, for boot debugging purpose.
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <4A4ACE29.3010407@cn.fujitsu.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/Documentation/trace/events.txt b/Documentation/trace/events.txt
index f157d75..2bcc8d4 100644
--- a/Documentation/trace/events.txt
+++ b/Documentation/trace/events.txt
@@ -83,6 +83,15 @@
X - there is a mixture of events enabled and disabled
? - this file does not affect any event
+2.3 Boot option
+---------------
+
+In order to facilitate early boot debugging, use boot option:
+
+ trace_event=[event-list]
+
+The format of this boot option is the same as described in section 2.1.
+
3. Defining an event-enabled tracepoint
=======================================