The current text could mislead the user into believing that only read()
disables tracing. Clarify that any open() call that requests read access
disables tracing.
Link: https://lkml.kernel.org/r/CAADnVQ+hU6QOC_dPmpjnuv=9g4SQEeaMEMqXOS2WpMj=q=LdiQ@mail.gmail.com
Signed-off-by: Peter Wu <[email protected]>
---
Documentation/trace/ftrace.rst | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)
diff --git a/Documentation/trace/ftrace.rst b/Documentation/trace/ftrace.rst
index f60079259669..965be5c9afb3 100644
--- a/Documentation/trace/ftrace.rst
+++ b/Documentation/trace/ftrace.rst
@@ -125,7 +125,8 @@ 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 while this file is being read (opened).
+ disabled when the file is open for reading. Once all readers
+ are closed, tracing is re-enabled.
trace_pipe:
@@ -139,8 +140,9 @@ 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. This file will not
- disable tracing while being read.
+ information every time it is read. Unlike the
+ "trace" file, opening this file for reading will not
+ temporarily disable tracing.
trace_options:
@@ -3153,7 +3155,10 @@ different. The trace is live.
Note, reading the trace_pipe file will block until more input is
-added.
+added. This is contrary to the trace file. If any process opened
+the trace file for reading, it will actually disable tracing and
+prevent new entries from being added. The trace_file file does
+not have this limitation.
trace entries
-------------
--
2.22.0
On Fri, 23 Aug 2019 00:48:23 +0100
Peter Wu <[email protected]> wrote:
> The current text could mislead the user into believing that only read()
> disables tracing. Clarify that any open() call that requests read access
> disables tracing.
>
> Link: https://lkml.kernel.org/r/CAADnVQ+hU6QOC_dPmpjnuv=9g4SQEeaMEMqXOS2WpMj=q=LdiQ@mail.gmail.com
> Signed-off-by: Peter Wu <[email protected]>
> ---
> Documentation/trace/ftrace.rst | 13 +++++++++----
> 1 file changed, 9 insertions(+), 4 deletions(-)
>
> diff --git a/Documentation/trace/ftrace.rst b/Documentation/trace/ftrace.rst
> index f60079259669..965be5c9afb3 100644
> --- a/Documentation/trace/ftrace.rst
> +++ b/Documentation/trace/ftrace.rst
> @@ -125,7 +125,8 @@ 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 while this file is being read (opened).
> + disabled when the file is open for reading. Once all readers
> + are closed, tracing is re-enabled.
>
> trace_pipe:
>
> @@ -139,8 +140,9 @@ 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. This file will not
> - disable tracing while being read.
> + information every time it is read. Unlike the
> + "trace" file, opening this file for reading will not
> + temporarily disable tracing.
>
> trace_options:
>
> @@ -3153,7 +3155,10 @@ different. The trace is live.
>
>
> Note, reading the trace_pipe file will block until more input is
> -added.
> +added. This is contrary to the trace file. If any process opened
> +the trace file for reading, it will actually disable tracing and
> +prevent new entries from being added. The trace_file file does
I was just about to ack this, and then I saw the above.
s/trace_file/trace_pipe/
Other than that, it looks good!
-- Steve
> +not have this limitation.
>
> trace entries
> -------------
The current text could mislead the user into believing that only read()
disables tracing. Clarify that any open() call that requests read access
disables tracing.
Link: https://lkml.kernel.org/r/CAADnVQ+hU6QOC_dPmpjnuv=9g4SQEeaMEMqXOS2WpMj=q=LdiQ@mail.gmail.com
Signed-off-by: Peter Wu <[email protected]>
---
v2: fix typo s/trace_file/trace_pipe/ (spotted by Steven)
---
Documentation/trace/ftrace.rst | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)
diff --git a/Documentation/trace/ftrace.rst b/Documentation/trace/ftrace.rst
index f60079259669..e3060eedb22d 100644
--- a/Documentation/trace/ftrace.rst
+++ b/Documentation/trace/ftrace.rst
@@ -125,7 +125,8 @@ 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 while this file is being read (opened).
+ disabled when the file is open for reading. Once all readers
+ are closed, tracing is re-enabled.
trace_pipe:
@@ -139,8 +140,9 @@ 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. This file will not
- disable tracing while being read.
+ information every time it is read. Unlike the
+ "trace" file, opening this file for reading will not
+ temporarily disable tracing.
trace_options:
@@ -3153,7 +3155,10 @@ different. The trace is live.
Note, reading the trace_pipe file will block until more input is
-added.
+added. This is contrary to the trace file. If any process opened
+the trace file for reading, it will actually disable tracing and
+prevent new entries from being added. The trace_pipe file does
+not have this limitation.
trace entries
-------------
--
2.22.0
On Sat, 31 Aug 2019 16:35:00 +0100
Peter Wu <[email protected]> wrote:
> The current text could mislead the user into believing that only read()
> disables tracing. Clarify that any open() call that requests read access
> disables tracing.
>
> Link: https://lkml.kernel.org/r/CAADnVQ+hU6QOC_dPmpjnuv=9g4SQEeaMEMqXOS2WpMj=q=LdiQ@mail.gmail.com
> Signed-off-by: Peter Wu <[email protected]>
Acked-by: Steven Rostedt (VMware) <[email protected]>
Jon care to take this in your tree?
Thanks!
-- Steve
> ---
> v2: fix typo s/trace_file/trace_pipe/ (spotted by Steven)
> ---
> Documentation/trace/ftrace.rst | 13 +++++++++----
> 1 file changed, 9 insertions(+), 4 deletions(-)
>
> diff --git a/Documentation/trace/ftrace.rst b/Documentation/trace/ftrace.rst
> index f60079259669..e3060eedb22d 100644
> --- a/Documentation/trace/ftrace.rst
> +++ b/Documentation/trace/ftrace.rst
> @@ -125,7 +125,8 @@ 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 while this file is being read (opened).
> + disabled when the file is open for reading. Once all readers
> + are closed, tracing is re-enabled.
>
> trace_pipe:
>
> @@ -139,8 +140,9 @@ 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. This file will not
> - disable tracing while being read.
> + information every time it is read. Unlike the
> + "trace" file, opening this file for reading will not
> + temporarily disable tracing.
>
> trace_options:
>
> @@ -3153,7 +3155,10 @@ different. The trace is live.
>
>
> Note, reading the trace_pipe file will block until more input is
> -added.
> +added. This is contrary to the trace file. If any process opened
> +the trace file for reading, it will actually disable tracing and
> +prevent new entries from being added. The trace_pipe file does
> +not have this limitation.
>
> trace entries
> -------------
On Sat, 31 Aug 2019 11:58:35 -0400
Steven Rostedt <[email protected]> wrote:
> Acked-by: Steven Rostedt (VMware) <[email protected]>
>
> Jon care to take this in your tree?
Will do.
jon