Randy wrote: > Hi, > Hi Randy,
> On 8/30/26 4:12 AM, [email protected] wrote: > > From: Shengming Hu <[email protected]> > > > > Document set_ftrace_comm and set_ftrace_notrace_comm, including their > > write and O_TRUNC behavior, accepted comm names, interaction with PID > > filters, and when a task is rechecked after its comm changes. > > > > Signed-off-by: Shengming Hu <[email protected]> > > --- > > Documentation/trace/ftrace.rst | 31 +++++++++++++++++++++++++++++++ > > 1 file changed, 31 insertions(+) > > > > diff --git a/Documentation/trace/ftrace.rst b/Documentation/trace/ftrace.rst > > index 7261f25f8b4b..a96fc436ec16 100644 > > --- a/Documentation/trace/ftrace.rst > > +++ b/Documentation/trace/ftrace.rst > > @@ -313,6 +313,37 @@ of ftrace. Here is a list of some of the key files: > > If a PID is in both this file and "set_ftrace_pid", then this > > file takes precedence, and the thread will not be traced. > > > > + set_ftrace_comm: > > + > > + Have the function and function_graph tracers trace only threads whose > > + task comm is listed in this file. Names are matched exactly and must > > + contain between 1 and TASK_COMM_LEN - 1 bytes. > > + > > + Each write adds one name. A single trailing newline is ignored, while > > + embedded newlines are rejected. A zero-length write or a write > > containing > > + only a newline adds no entry. Duplicate entries have no effect. > > + > > + Opening the file with O_TRUNC clears the filter. Otherwise, writes add > > Is there a way to clear the filter from (in) a shell script? > Yes. It can be cleared with: # echo > set_ftrace_comm The shell opens the file with O_TRUNC, which clears the existing filter. I described the O_TRUNC behavior but overlooked the corresponding user-facing shell command. Thanks for pointing this out. Based on Masami's feedback, I am now considering reworking the series around a generic event trigger that updates set_ftrace_pid, so the comm-specific files may not remain in the next version. -- With Best Regards, Shengming
