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=l...@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 > -------------
