[for-next][PATCH 14/21] tracing: Have the document reflect that the trace file keeps tracing enabled
From: Steven Rostedt
Date: Sun Mar 29 2020 - 14:43:45 EST
From: "Steven Rostedt (VMware)" <rostedt@xxxxxxxxxxx>
Now that reading the trace file does not temporarly stop tracing while it is
open, update the document to reflect this fact.
Link: http://lkml.kernel.org/r/20200317213417.209675068@xxxxxxxxxxx
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
---
Documentation/trace/ftrace.rst | 13 +++++++------
1 file changed, 7 insertions(+), 6 deletions(-)
diff --git a/Documentation/trace/ftrace.rst b/Documentation/trace/ftrace.rst
index c33950a35d65..00621731bf27 100644
--- a/Documentation/trace/ftrace.rst
+++ b/Documentation/trace/ftrace.rst
@@ -125,10 +125,13 @@ of ftrace. Here is a list of some of the key files:
trace:
This file holds the output of the trace in a human
- readable format (described below). Note, tracing is temporarily
- disabled when the file is open for reading. Once all readers
- are closed, tracing is re-enabled. Opening this file for
+ readable format (described below). Opening this file for
writing with the O_TRUNC flag clears the ring buffer content.
+ Note, this file is not a consumer. If tracing is off
+ (no tracer running, or tracing_on is zero), it will produce
+ the same output each time it is read. When tracing is on,
+ it may produce inconsistent results as it tries to read
+ the entire buffer without consuming it.
trace_pipe:
@@ -142,9 +145,7 @@ of ftrace. Here is a list of some of the key files:
will not be read again with a sequential read. The
"trace" file is static, and if the tracer is not
adding more data, it will display the same
- information every time it is read. Unlike the
- "trace" file, opening this file for reading will not
- temporarily disable tracing.
+ information every time it is read.
trace_options:
--
2.25.1