Re: [RFC PATCH v2 4/4] rtla/osnoise: Leverage IPI event filters when tracing a subset of CPUs

[Steven Rostedt <rostedt@goodmis.org>]

On Wed, 1 Jul 2026 08:45:40 +0200
Tomas Glozar <tglozar@redhat.com> wrote:

> I double-checked that and you are correct that the docstring says so,
> but it's an error in the docstring. According to the manpage, it
> returns the number of bytes written (i.e. positive on success, not
> zero) [1]:

Note, the man page is considered the source of "truth".

> 
> "RETURN VALUE
> ...
> tracefs_event_file_write() and tracefs_event_file_append() returns
> *the number of bytes written to the system/event file* or negative on
> error."
> 
> The code agrees as well: in tracefs_event_file_write() there's the
> wrong docstring (likely copied from another function) [2]:
> 
> /*
>  * tracefs_event_file_write - write to an event file
>  * ...
>  * Return 0 on success, and -1 on error.

Ug, that's a bug and needs to be fixed.

Thanks for catching this. I need to spend some time to catch up on the user
side of tracing. There's a few new bugzillas and patches I need to apply.

-- Steve


>  */
> int tracefs_event_file_write(struct tracefs_instance *instance,
>     const char *system, const char *event,
>     const char *file, const char *str)
> {
>         ....
>         ret = tracefs_instance_file_write(instance, path, str);
>         free(path);
>         return ret;
> }