[PATCH] docs: ftrace: Specifies when buffers get clear
From: Frank A. Cancio Bello <hidden>
Date: 2019-12-16 04:28:00
Also in:
lkml
Subsystem:
documentation, function hooks (ftrace), the rest, tracing · Maintainers:
Jonathan Corbet, Steven Rostedt, Masami Hiramatsu, Linus Torvalds
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 <redacted> --- 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