tracing: Add trace_options kernel command line parameter

Add trace_options to the kernel command line parameter to be able to
set options at early boot. For example, to enable stack dumps of
events, add the following:

  trace_options=stacktrace

This along with the trace_event option, you can get not only
traces of the events but also the stack dumps with them.

Requested-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 16 insertions, 0 deletions

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 9776f068306b..2b48c52464a1 100644
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -2859,6 +2859,22 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
                         to facilitate early boot debugging.
                         See also Documentation/trace/events.txt
 
+        trace_options=[option-list]
+                        [FTRACE] Enable or disable tracer options at boot.
+                        The option-list is a comma delimited list of options
+                        that can be enabled or disabled just as if you were
+                        to echo the option name into
+
+                            /sys/kernel/debug/tracing/trace_options
+
+                        For example, to enable stacktrace option (to dump the
+                        stack trace of each event), add to the command line:
+
+                              trace_options=stacktrace
+
+                        See also Documentation/trace/ftrace.txt "trace options"
+                        section.
+
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