lkml.org 
[lkml]   [2019]   [Dec]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[PATCH] docs: ftrace: Specifies when buffers get clear
Clarify in a few places where the ring buffer and the "snapshot"
buffer are cleared as a side effect of an operation.

This will avoid users lost of tracing data because of these so far
undocumented behavior.

Signed-off-by: Frank A. Cancio Bello <frank@generalsoftwareinc.com>
---
Documentation/trace/ftrace.rst | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/Documentation/trace/ftrace.rst b/Documentation/trace/ftrace.rst
index d2b5657ed33e..5cc65314e16d 100644
--- a/Documentation/trace/ftrace.rst
+++ b/Documentation/trace/ftrace.rst
@@ -95,7 +95,8 @@ of ftrace. Here is a list of some of the key files:
current_tracer:

This is used to set or display the current tracer
- that is configured.
+ that is configured. Changing the current tracer clears
+ the ring buffer content as well as the "snapshot" buffer.

available_tracers:

@@ -126,7 +127,9 @@ of ftrace. Here is a list of some of the key files:
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.
+ are closed, tracing is re-enabled. Opening this file for
+ writing with the O_TRUNC flag clears the ring buffer content
+ as well as the "snapshot" buffer.

trace_pipe:

@@ -490,6 +493,9 @@ of ftrace. Here is a list of some of the key files:

# echo global > trace_clock

+ Setting a clock clears the ring buffer content as well as the
+ "snapshot" buffer.
+
trace_marker:

This is a very useful file for synchronizing user space
--
2.17.1
\
 
 \ /
  Last update: 2019-12-16 05:28    [W:0.032 / U:3.412 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site